Julien Garnon

Laurence Meylheuc

Roberto Luigi Cazzato

Danoob Dalili

Guillaume Koch

Pierre Auloge

Bernard Bayle

Afshin Gangi

Luarence Meylheuc

Russell H Morgan

Percutaneous extra-spinal cementoplasty in patients with cancer: A systematic review of procedural details and clinical outcomes

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Percutaneous cementoplasty has been described for the first time in 1987 for the management of an agressive hemangioma of C2 [START_REF] Galibert | Preliminary note on the treatment of vertebral angioma by percutaneous acrylic vertebroplasty[END_REF]. It was then successfully applied for the treatment of painful osteoporotic and malignant vertebral compression fractures [START_REF] Gangi | Percutaneous vertebroplasty: indications, technique, and results[END_REF][START_REF] Weill | Spinal metastases: indications for and results of percutaneous injection of acrylic surgical cement[END_REF]. Hence, in cancer patients, vertebroplasty offers a minimally invasive solution both to alleviate the pain related to spinal metastases and to provide bone consolidation in case of an impending fracture of the vertebral body [START_REF] Health | Vertebral Augmentation Involving Vertebroplasty or Kyphoplasty for Cancer-Related Vertebral Compression Fractures: A Systematic Review[END_REF][START_REF] Spratt | An integrated multidisciplinary algorithm for the management of spinal metastases: an International Spine Oncology Consortium report[END_REF].

The management of painful malignant lesions outside the spine with cementoplasty, also known as extra-spinal cementoplasty or osteoplasty, followed on from the spinal experience and turned out to be effective as well [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF]. Besides pain management, bone consolidation is of utmost importance is some mechanical critical areas. For example, standalone cementoplasty can be applied to the acetabulum (acetabuloplasty) in order to prevent from a pathological fracture [START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF]. In other locations such as the long bones, PMMA can be used in combination with other devices such as nails to enhance the biomechanical stability of the surgical device [START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF]. Similarly to the spine, the antalgic effect does not seem to be related to the amount of injected cement [START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Cotten | Percutaneous vertebroplasty for osteolytic metastases and myeloma: effects of the percentage of lesion filling and the leakage of methyl methacrylate at clinical follow-up[END_REF][START_REF] Luo | Vertebroplasty: only small cement volumes are required to normalize stress distributions on the vertebral bodies[END_REF]. On the other hand, it is assumed that optimal bone consolidation requires to fill as much as possible the metastatic process and the surrounding cancellous bone [START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF]. If the technique of vertebroplasty is quite well standardized, there is little literature focusing on the technique of extra-spinal cementoplasty. Hence, the present review was performed to give an overview of extra-spinal cementoplasty regarding patient/lesions characteristics and procedural details.

Materials and methods

Selection criteria

Informed consent was not required for this retrospective systematic review. We search PUBMED, MEDLINE, MEDLINE in-process, EMBASE and the Cochrane databases between January 1990 and February 2019 using the following keywords «percutaneous cementoplasty», «percutaneous osteoplasty» and «extraspinal cementoplasty». After exclusion of duplicates, the titles and abstracts of publications identified by the database search were screened for studies that potentially met the inclusion/exclusion criteria. Final eligibility was based after examination of full text. The screening was performed by two of the authors (XX and XX).

Disagreements were resolved by consensus.

The following criteria were used for selection : (a) retrospective/prospective cohort > 4 patients, (b) published in English, (c) reporting the use of percutaneous cementoplasty, i.e percutaneous injection of cement inside a bone metastasis using a dedicated bone trocar, in extraspinal locations (d) as a stand-alone procedure or in combination with another percutaneous intervention, in order to (e) provide pain palliation and/or bone consolidation.

Papers reporting the use of hollowed implants through which cement was injected (hollowed screws for example) were not considered as true cementoplasty procedures and were therefore excluded from analysis. Studies including both spinal and extraspinal procedures were only included if detailed data of extraspinal interventions were accessible. Sacral cementoplasties were considered as extra-spinal cementoplasties. Commentaries, abstract, review articles and conference presentations were not included.

Methodological quality assessment

The quality of studies was evaluated with a modified version of the Newcastle-Ottawa scale [START_REF] Lanza | Osteoid osteoma treated by percutaneous thermal ablation: when do we fail? A systematic review and guidelines for future reporting[END_REF][START_REF] Wells | The Newcastle-Ottawa Scale (NOS) for assessing the quality of non-randomised studies in meta-analyses[END_REF]. This system evaluates the quality of non-randomized studies included in a review using a "star system" from 0 to 6. The higher the number of stars, the lower the risk of bias.

Papers awarded with less than four stars were excluded from the present review.

Data extraction and analysis

Full text of all included papers was reviewed in order to collect specific items in a dedicated spreadsheet (Excel 2011, Microsoft, Seattle, WA). For each study, data on (a) patient age, (b) lesion characteristics (histology, size, localisation, Harrington classification for acetabular lesions, Mirel's score for lesions located in long bones), (c) performing physician (surgeon/interventional radiologist), (d) additional percutaneous intervention within the same session of treatment (balloon expansion, thermal ablation, implants), (e) bone needle size in Gauge, (f) volume of cement, (g) degree of lesion filling, (h) description of the technique for injection greater than 10ml, (i) rate of overall and symptomatic leakages, (j) pain score before and after the intervention at last time-point of assessment, and (k) secondary fractures/surgery were extracted if available. Case by case analysis was performed whenever possible.

Descriptive statistics were computed to present results. The overall weighted mean method was used to calculate a mean value across studies whenever feasible.

Results

The first search query produced 2678 papers. After screening by title and abstracts, 65 studies were included for full text analysis. Of those, 30 fulfilled the inclusion/exclusion criteria and were therefore included for the present study (fig. 1). No exclusions were made due to risk of bias.

Included publications were issued between 1995 and 2019. There were 20 retrospective and 6 prospective articles, while 4 papers did not clearly state whether the study was prospective or retrospective.

Patients and lesions characteristics

A total of 761 extra-spinal lesions (data available from all papers; number of paper np=30) were treated using percutaneous cementoplasty [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF]. The mean age of the patients at the time of treatment was available/could be extracted for all studies but one (np=29) and ranged between 48,6 and 69,4 years old across publications [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Hierholzer | Percutaneous osteoplasty as a treatment for painful malignant bone lesions of the pelvis and femur[END_REF][START_REF] Cotten | Malignant acetabular osteolyses: percutaneous injection of acrylic bone cement[END_REF][START_REF] Durfee | Percutaneous Acetabuloplasty for Metastatic Lesions to the Pelvis[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Weill | Acetabulum malignancies: technique and impact on pain of percutaneous injection of acrylic surgical cement[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Hoffmann | Radiofrequency ablation in combination with osteoplasty in the treatment of painful metastatic bone disease[END_REF][START_REF] Kelekis | Pelvic osteoplasty in osteolytic metastases: technical approach under fluoroscopic guidance and early clinical results[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Wei | Computed tomographyguided percutaneous microwave ablation combined with osteoplasty for palliative treatment of painful extraspinal bone metastases from lung cancer[END_REF][START_REF] Marcy | Percutaneous cementoplasty for pelvic bone metastasis[END_REF][START_REF] Gupta | Evaluating the safety and effectiveness of percutaneous acetabuloplasty[END_REF]. The most frequent histology was available/could be extracted for all papers (np=30) [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF]. Lung cancer was the most frequently reported primary tumor (11 papers), followed by breast (8 papers) and myeloma/kidney (7 papers).

Size of lesions was available in 9 papers (np=9) [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF]. The mean size was reported/could be calculated for 8 papers (np=8), while one paper reported only the volume of the lesions. The mean size ranged from 29mm to 73mm across studies [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF].

The mean size calculated among 315 lesions (np=8) using the overall weighted mean method was 45mm [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF].

Localisation of the extra-spinal lesions was available for all papers and could be divided into lesions of the pelvis (coxal bone and sacrum), of the long bones and of other bones (rib, skull) [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF]. 11 papers focused on pelvic cementoplasties, 6 on cementoplasties of the long bones and 13 included all kind of locations. Overall, 489 lesions were located in the pelvis, 262 in the long bones of the limbs and 10 in other locations (np=30) (table1) [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF]. The most frequently treated area in the coxal bone (np=22) was the acetabulum (197 lesions) followed by the ilium (90 lesions) and the ischium/pubis. Only two papers over the 24 articles reporting percutaneous cementoplasty in the pelvis did not specify sublocation of the tumours within the coxal bone [START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF]. Grading of acetabular lesions using the Harrington classification could be extracted from 3 papers, representing a total of 55 lesions with a mean score of 2,3 [START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF]. Lesions of the long bones were more frequently localized (np=19) in the femur (166 lesions) [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Hierholzer | Percutaneous osteoplasty as a treatment for painful malignant bone lesions of the pelvis and femur[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Hoffmann | Radiofrequency ablation in combination with osteoplasty in the treatment of painful metastatic bone disease[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Wei | Computed tomographyguided percutaneous microwave ablation combined with osteoplasty for palliative treatment of painful extraspinal bone metastases from lung cancer[END_REF]. The Mirel's score, which evaluates the risk of pathological fracture for lesions of the long bones, was reported in 5 papers, with a mean score greater than 9 (over 12) in all publications [START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF].

Palliative pain management was the main indication in 735 cases (np=27) [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Hierholzer | Percutaneous osteoplasty as a treatment for painful malignant bone lesions of the pelvis and femur[END_REF][START_REF] Cotten | Malignant acetabular osteolyses: percutaneous injection of acrylic bone cement[END_REF][START_REF] Durfee | Percutaneous Acetabuloplasty for Metastatic Lesions to the Pelvis[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Weill | Acetabulum malignancies: technique and impact on pain of percutaneous injection of acrylic surgical cement[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Hoffmann | Radiofrequency ablation in combination with osteoplasty in the treatment of painful metastatic bone disease[END_REF][START_REF] Kelekis | Pelvic osteoplasty in osteolytic metastases: technical approach under fluoroscopic guidance and early clinical results[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Wei | Computed tomographyguided percutaneous microwave ablation combined with osteoplasty for palliative treatment of painful extraspinal bone metastases from lung cancer[END_REF][START_REF] Marcy | Percutaneous cementoplasty for pelvic bone metastasis[END_REF][START_REF] Gupta | Evaluating the safety and effectiveness of percutaneous acetabuloplasty[END_REF], while prevention of fracture was the major concern in 26 cases (np=3) [START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF].

Procedural details

Performing physician

The performing physician could be evaluated in all studies but one (np=29) [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Hierholzer | Percutaneous osteoplasty as a treatment for painful malignant bone lesions of the pelvis and femur[END_REF][START_REF] Cotten | Malignant acetabular osteolyses: percutaneous injection of acrylic bone cement[END_REF][START_REF] Durfee | Percutaneous Acetabuloplasty for Metastatic Lesions to the Pelvis[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Weill | Acetabulum malignancies: technique and impact on pain of percutaneous injection of acrylic surgical cement[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Hoffmann | Radiofrequency ablation in combination with osteoplasty in the treatment of painful metastatic bone disease[END_REF][START_REF] Kelekis | Pelvic osteoplasty in osteolytic metastases: technical approach under fluoroscopic guidance and early clinical results[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Marcy | Percutaneous cementoplasty for pelvic bone metastasis[END_REF][START_REF] Gupta | Evaluating the safety and effectiveness of percutaneous acetabuloplasty[END_REF]. Among the 728 treatments, 613 (84,2%) were performed by interventional radiologists and 115 (15,8%) by orthopaedic surgeons. Lesions treated by surgeons (np=5) were located either in the long bones (n=63) or the acetabulum (n=52) [START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Durfee | Percutaneous Acetabuloplasty for Metastatic Lesions to the Pelvis[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Gupta | Evaluating the safety and effectiveness of percutaneous acetabuloplasty[END_REF]. All 63 percutaneous cementoplasties performed by surgeons for lesions of the long bones (np=2) were combined with surgical stabilization using flexible (n=20) or closed intramedullary (n=43) nails [START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF]. There was no other extra-spinal lesion treated by surgeons. Interventional radiologists (np=24) treated more lesions in the pelvis (n=408) than in the long bones (n=195) [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Hierholzer | Percutaneous osteoplasty as a treatment for painful malignant bone lesions of the pelvis and femur[END_REF][START_REF] Cotten | Malignant acetabular osteolyses: percutaneous injection of acrylic bone cement[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Weill | Acetabulum malignancies: technique and impact on pain of percutaneous injection of acrylic surgical cement[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Hoffmann | Radiofrequency ablation in combination with osteoplasty in the treatment of painful metastatic bone disease[END_REF][START_REF] Kelekis | Pelvic osteoplasty in osteolytic metastases: technical approach under fluoroscopic guidance and early clinical results[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Marcy | Percutaneous cementoplasty for pelvic bone metastasis[END_REF]. Cementoplasty without any additional implanted device was used in the majority of lesions (n=166, representing 85% of the lesions) treated by IRs in the long bones [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Hierholzer | Percutaneous osteoplasty as a treatment for painful malignant bone lesions of the pelvis and femur[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Hoffmann | Radiofrequency ablation in combination with osteoplasty in the treatment of painful metastatic bone disease[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF]. Implant augmented cementoplasties were performed for the remaining 31 lesions (15%), and included cannulated screws (n=13, one paper), bone puncture needles after removal of the tails and pinpoints (n=6, one paper) and 22G stainless steel microneedles (n=12, one paper) [START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF].

Additional intervention

Detailed data were available for all papers but one (np=29) that reported the use of balloon kyphoplasty for some pelvic cases without further specifications [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF].

Cementoplasty was reported as a stand-alone procedure for 427 lesions (60,1%). Kyphoplasty was performed in 10 cases (1,4%) (np=2), all located in the acetabulum [START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Durfee | Percutaneous Acetabuloplasty for Metastatic Lesions to the Pelvis[END_REF]. For 186 lesions (26,2%), thermal ablation was combined to cementoplasty (np=10): 134 lesions (72%) were ablated with monopolar RFA (np=7), 33 lesions (17,7%) with microwave (np=1), 12 (6,5%) with bipolar RFA (np=1) and 7 (3,8%) with cryoablation (np=1) [START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Hoffmann | Radiofrequency ablation in combination with osteoplasty in the treatment of painful metastatic bone disease[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Wei | Computed tomographyguided percutaneous microwave ablation combined with osteoplasty for palliative treatment of painful extraspinal bone metastases from lung cancer[END_REF].

Localisation of the lesion that were ablated was the pelvis in 148 cases (79,6%), the long bones in 34 cases (18,3%) and other locations in 4 cases (2,1%). Lesions that were cryoablated in the acetabulum all benefited from the combination of kyphoplasty and cementoplasty either the same day after cryoablation (2 patients) or the day after (5 patients) (np=1) [START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF]. As priorly detailed, implant-augmented cementoplasty was performed for 94 lesions (12,3%) (np=5), all located in the long bones [START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF].

Needle size

The needle size was reported in 25 articles representing 704 lesions (np=25) [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Cotten | Malignant acetabular osteolyses: percutaneous injection of acrylic bone cement[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Weill | Acetabulum malignancies: technique and impact on pain of percutaneous injection of acrylic surgical cement[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Hoffmann | Radiofrequency ablation in combination with osteoplasty in the treatment of painful metastatic bone disease[END_REF][START_REF] Kelekis | Pelvic osteoplasty in osteolytic metastases: technical approach under fluoroscopic guidance and early clinical results[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Wei | Computed tomographyguided percutaneous microwave ablation combined with osteoplasty for palliative treatment of painful extraspinal bone metastases from lung cancer[END_REF][START_REF] Gupta | Evaluating the safety and effectiveness of percutaneous acetabuloplasty[END_REF]. Precise data could be extracted from 14 papers (379 lesions) [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Cotten | Malignant acetabular osteolyses: percutaneous injection of acrylic bone cement[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Weill | Acetabulum malignancies: technique and impact on pain of percutaneous injection of acrylic surgical cement[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Kelekis | Pelvic osteoplasty in osteolytic metastases: technical approach under fluoroscopic guidance and early clinical results[END_REF][START_REF] Wei | Computed tomographyguided percutaneous microwave ablation combined with osteoplasty for palliative treatment of painful extraspinal bone metastases from lung cancer[END_REF][START_REF] Marcy | Percutaneous cementoplasty for pelvic bone metastasis[END_REF]. The diameter of the needles in the remaining 11 papers (325 lesions) was variable, without the possibility of a case by case analysis [START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Hoffmann | Radiofrequency ablation in combination with osteoplasty in the treatment of painful metastatic bone disease[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Gupta | Evaluating the safety and effectiveness of percutaneous acetabuloplasty[END_REF]. The Gauge size was 13G for 72 lesions (10,2%) (np=2), 11G for 150 lesions (21,3%) (np=5), 10G for 145 lesions (20,6%) (np=6), and 8G for 12 lesions (1,7%) (np=1). It ranged from 11G to 13G for 285 lesions (40,5%) (np=8) and from 8G to 15G for 40 lesions (5,7%) (np=3).

Volume of cement

The volume of injected cement was available in 20 papers, reported as a mean value in 11 papers and as case by case data in 9 papers [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Hierholzer | Percutaneous osteoplasty as a treatment for painful malignant bone lesions of the pelvis and femur[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Weill | Acetabulum malignancies: technique and impact on pain of percutaneous injection of acrylic surgical cement[END_REF][START_REF] Hoffmann | Radiofrequency ablation in combination with osteoplasty in the treatment of painful metastatic bone disease[END_REF][START_REF] Kelekis | Pelvic osteoplasty in osteolytic metastases: technical approach under fluoroscopic guidance and early clinical results[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Wei | Computed tomographyguided percutaneous microwave ablation combined with osteoplasty for palliative treatment of painful extraspinal bone metastases from lung cancer[END_REF][START_REF] Marcy | Percutaneous cementoplasty for pelvic bone metastasis[END_REF]. One paper reported only the mean volume of cement for pelvic cementoplasties but not for lesions in the long bones [START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF]. 9 papers did not report the amount of cement [START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Cotten | Malignant acetabular osteolyses: percutaneous injection of acrylic bone cement[END_REF][START_REF] Durfee | Percutaneous Acetabuloplasty for Metastatic Lesions to the Pelvis[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Gupta | Evaluating the safety and effectiveness of percutaneous acetabuloplasty[END_REF].

The mean volume of cement ranged from 2,7ml to 32,2ml across studies (np=20) (table1). Data from these 20 studies were extracted and used to calculate a mean volume using the overall weighted mean method. Hence, the mean volume was 8,8 ml among the 485 lesions used for statistical evaluation (np=20). More specifically, data for pelvic injections could be extracted from 13 papers: the mean volume calculated over 188 lesions (np=13) was 9,1 ml (table2). The maximal reported volume for a pelvic osteoplasty was 36ml [START_REF] Hierholzer | Percutaneous osteoplasty as a treatment for painful malignant bone lesions of the pelvis and femur[END_REF]. For long bones, data from 8 papers were extracted: the mean volume was calculated over 84 lesions (np=8) and was 16,9 ml (table2). Maximal reported volume for a cementoplasty in a long bone was 42 ml [START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF]. Detailed analysis of the 9 papers reporting case by case data showed that over 116 lesions, 50 were filled with more than 10 ml, 12 with more than 20ml and 6 with more than 30ml. 26 of the 50 lesions filled with a volume greater than 10ml were located in the pelvis (acetabulum was the most frequent location), and 24 in the long bones (femur was the most frequent location).

Technique of injection for volumes >10ml

Over the 17 papers which reported either a mean or a maximum volume superior to 10ml, 7 briefly stated how such injection was achieved [START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Cotten | Malignant acetabular osteolyses: percutaneous injection of acrylic bone cement[END_REF][START_REF] Weill | Acetabulum malignancies: technique and impact on pain of percutaneous injection of acrylic surgical cement[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF]. They all describe the use of additional needle(s) and cement(s) to complete the injection. The mean number of needles per site of injection was available for one of those 7 papers, with a mean value of 3,83 [START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF]. One paper described precisely the technique used to inject more than 10ml of cement [START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF]. In that paper, the authors were injecting simultaneously different volumes of cement on 2 or 3 different bone trocars.

Lesion filling

Precise information (i.e not subjective) about the percentage of filling by cement was available in 3 papers (62 lesions) focusing on pelvic osteoplasties [START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF]. The percentage ranged from 54,8% to 64%, for a mean value of 56,8 % using the overall weighted mean method. One other paper reported the percentage of filling of the lesion as superior or inferior to 50%, with 70% of the lesions exhibiting a filling greater than 50% without further specification [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF].

Outcomes

Pain palliation

Pain scores using a visual analogic scale (VAS score) could be extracted from 24 papers [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Cotten | Malignant acetabular osteolyses: percutaneous injection of acrylic bone cement[END_REF][START_REF] Durfee | Percutaneous Acetabuloplasty for Metastatic Lesions to the Pelvis[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Kelekis | Pelvic osteoplasty in osteolytic metastases: technical approach under fluoroscopic guidance and early clinical results[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Wei | Computed tomographyguided percutaneous microwave ablation combined with osteoplasty for palliative treatment of painful extraspinal bone metastases from lung cancer[END_REF][START_REF] Marcy | Percutaneous cementoplasty for pelvic bone metastasis[END_REF][START_REF] Gupta | Evaluating the safety and effectiveness of percutaneous acetabuloplasty[END_REF]. 22 of the 24 papers reported the VAS score as a 10 points scale [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Cotten | Malignant acetabular osteolyses: percutaneous injection of acrylic bone cement[END_REF][START_REF] Durfee | Percutaneous Acetabuloplasty for Metastatic Lesions to the Pelvis[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Kelekis | Pelvic osteoplasty in osteolytic metastases: technical approach under fluoroscopic guidance and early clinical results[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Wei | Computed tomographyguided percutaneous microwave ablation combined with osteoplasty for palliative treatment of painful extraspinal bone metastases from lung cancer[END_REF][START_REF] Marcy | Percutaneous cementoplasty for pelvic bone metastasis[END_REF][START_REF] Gupta | Evaluating the safety and effectiveness of percutaneous acetabuloplasty[END_REF]; 2 papers used a 100 points scale which was turned into a 10 points scale for further evaluation [START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF]. One paper mentioned the VAS score but without the possibility to differentiate the extra-spinal cases from the spinal ones and was therefore not included for analysis [START_REF] Hoffmann | Radiofrequency ablation in combination with osteoplasty in the treatment of painful metastatic bone disease[END_REF]. The 5 remaining papers did not report precisely the VAS score and only mentioned subjective evaluation of the pain [START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Hierholzer | Percutaneous osteoplasty as a treatment for painful malignant bone lesions of the pelvis and femur[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Weill | Acetabulum malignancies: technique and impact on pain of percutaneous injection of acrylic surgical cement[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF]. The preoperative VAS scores ranged between 3.2 and 9.5 (np=24). For the post-operative pain scores, we used the last time point available for evaluation. This time point could be extracted from 21 papers and ranged from 24 hours to one-year, with 14 articles reporting the last evaluation at one month or more (table3), and 10 articles at 3 months or more. The number of patients completing the last follow-up couldn't be precisely numbered. Overall, post-operative scores ranged from 0,4 to 5,6 (np=24) [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Cotten | Malignant acetabular osteolyses: percutaneous injection of acrylic bone cement[END_REF][START_REF] Durfee | Percutaneous Acetabuloplasty for Metastatic Lesions to the Pelvis[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Kelekis | Pelvic osteoplasty in osteolytic metastases: technical approach under fluoroscopic guidance and early clinical results[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Wei | Computed tomographyguided percutaneous microwave ablation combined with osteoplasty for palliative treatment of painful extraspinal bone metastases from lung cancer[END_REF][START_REF] Marcy | Percutaneous cementoplasty for pelvic bone metastasis[END_REF][START_REF] Gupta | Evaluating the safety and effectiveness of percutaneous acetabuloplasty[END_REF]. 21 papers over 24 reported a difference between the pre-and the post-interventional scores greater than two [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Durfee | Percutaneous Acetabuloplasty for Metastatic Lesions to the Pelvis[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Kelekis | Pelvic osteoplasty in osteolytic metastases: technical approach under fluoroscopic guidance and early clinical results[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Wei | Computed tomographyguided percutaneous microwave ablation combined with osteoplasty for palliative treatment of painful extraspinal bone metastases from lung cancer[END_REF][START_REF] Gupta | Evaluating the safety and effectiveness of percutaneous acetabuloplasty[END_REF]. 13 papers reported a reduction of 5 points or more [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF].

Symptomatic cement leakage

A total of 10 symptomatic leakages were numbered among the 761 lesions (np=30), giving a rate of symptomatic leakage of 1,3% [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF]. Nerve injury was the most frequent symptomatic leakage (n=4 -0,6%).

Secondary fractures and secondary surgical procedures 6 papers did not clearly state if fracture assessment at the treated site was part of the follow-up [START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Hoffmann | Radiofrequency ablation in combination with osteoplasty in the treatment of painful metastatic bone disease[END_REF][START_REF] Gupta | Evaluating the safety and effectiveness of percutaneous acetabuloplasty[END_REF]. Hence, 24 papers (626 lesions) were analyzed [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Hierholzer | Percutaneous osteoplasty as a treatment for painful malignant bone lesions of the pelvis and femur[END_REF][START_REF] Cotten | Malignant acetabular osteolyses: percutaneous injection of acrylic bone cement[END_REF][START_REF] Durfee | Percutaneous Acetabuloplasty for Metastatic Lesions to the Pelvis[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Weill | Acetabulum malignancies: technique and impact on pain of percutaneous injection of acrylic surgical cement[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Kelekis | Pelvic osteoplasty in osteolytic metastases: technical approach under fluoroscopic guidance and early clinical results[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Wei | Computed tomographyguided percutaneous microwave ablation combined with osteoplasty for palliative treatment of painful extraspinal bone metastases from lung cancer[END_REF][START_REF] Marcy | Percutaneous cementoplasty for pelvic bone metastasis[END_REF]. The length of follow-up was available for 22 of these 24 articles and ranged from 62 days to 26,4 months. A total of 14 fractures (2,2%) occuring at the treated site could be identified (np=24), at an interval from the cementoplasty procedure ranging from 3 days to 7 months. 7 surgical interventions to fix the fracture were reported [START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Cazzato | Percutaneous long bone cementoplasty of the limbs: experience with fifty-one non-surgical patients[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF].

Additionally, two surgical extractions of cement leakages and 7 delayed acetabular interventions following percutaneous cementoplasty of the acetabulum (interval from the procedure available for only 3 cases, ranging from 10 to 39 months) were reported [START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Durfee | Percutaneous Acetabuloplasty for Metastatic Lesions to the Pelvis[END_REF][START_REF] Weill | Acetabulum malignancies: technique and impact on pain of percutaneous injection of acrylic surgical cement[END_REF].

Discussion

Percutaneous cementoplasty is an effective tool to alleviate the pain associated with extra-spinal bone metastases [START_REF] Iannessi | Percutaneous cementoplasty for the treatment of extraspinal painful bone lesion, a prospective study[END_REF][START_REF] Couraud | Evaluation of short-term efficacy of extraspinal cementoplasty for bone metastasis: A monocenter study of 31 patients[END_REF][START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Kim | Palliative percutaneous stabilization of lower extremity for bone metastasis using flexible nails and bone cement[END_REF][START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Fares | Combined percutaneous radiofrequency ablation and cementoplasty for the treatment of extraspinal painful bone metastases: A prospective study[END_REF][START_REF] Tian | Combination radiofrequency ablation and percutaneous osteoplasty for palliative treatment of painful extraspinal bone metastasis: a single-center experience[END_REF][START_REF] Sun | Cementoplasty for managing painful bone metastases outside the spine[END_REF][START_REF] Masala | Percutaneus osteoplasty in the treatment of extraspinal painful multiple myeloma lesions[END_REF][START_REF] Basile | Cementoplasty in the management of painful extraspinal bone metastases: our experience[END_REF][START_REF] Anselmetti | Treatment of extraspinal painful bone metastases with percutaneous cementoplasty: a prospective study of 50 patients[END_REF][START_REF] Durfee | Percutaneous Acetabuloplasty for Metastatic Lesions to the Pelvis[END_REF][START_REF] Maccauro | Percutaneous acetabuloplasty for metastatic acetabular lesions[END_REF][START_REF] Munk | Combined cementoplasty and radiofrequency ablation in the treatment of painful neoplastic lesions of bone[END_REF][START_REF] Kelekis | Percutaneous Augmented Peripheral Osteoplasty in Long Bones of Oncologic Patients for Pain Reduction and Prevention of Impeding Pathologic Fracture: The Rebar Concept[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Kelekis | Pelvic osteoplasty in osteolytic metastases: technical approach under fluoroscopic guidance and early clinical results[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] Toyota | Radiofrequency ablation therapy combined with cementoplasty for painful bone metastases: initial experience[END_REF][START_REF] Wei | Computed tomographyguided percutaneous microwave ablation combined with osteoplasty for palliative treatment of painful extraspinal bone metastases from lung cancer[END_REF][START_REF] Gupta | Evaluating the safety and effectiveness of percutaneous acetabuloplasty[END_REF]. The technique has been reported in more than 750 cases in the literature and has mostly been applied for acetabular lesions in the pelvis and in the femur for the long bones. The clinical benefit seems clear, as 21 over 24 studies reported a drop in pain score greater than 2 (which is considered as the threshold for significance), while the rate of symptomatic leakages was inferior to 2%. On the other hand, the review of literature also demonstrates great heterogeneity in terms of clinical practice. Most of the procedures (84,2%) were performed by interventional radiologists, probably because of an easier access to CT-scan/CBCT that offer high precision. Osteoplasty was performed as a stand-alone technique in the majority of cases (60,1%), while in the remaining 40% it was combined with another technique such as thermal ablation (26,2%), implant devices (12,3%) or balloon kyphoplasty (1,4%) prior to cement injection.

The exact benefit of combined ablation and cementoplasty vs cementoplasty alone cannot be assessed, especially for lesion limited to bone without extension to the surrounding soft tissue [START_REF] Cazzato | Percutaneous radiofrequency ablation of painful spinal metastasis: a systematic literature assessment of analgesia and safety[END_REF][START_REF] Kam | Combined Vertebral Augmentation and Radiofrequency Ablation in the Management of Spinal Metastases: an Update[END_REF]. Thermal ablation certainly makes sense to alleviate the pain related to the invasion of the surrounding muscle in case of a large osteolytic metastasis [START_REF] Coupal | The Hopeless Case? Palliative Cryoablation and Cementoplasty Procedures for Palliation of Large Pelvic Bone Metastases[END_REF][START_REF] Uri | An ice block: a novel technique of successful prevention of cement leakage using an ice ball[END_REF]. This certainly explains that ablation was predominantly performed in association to cementoplasty for lesions located in the pelvic girdle, which frequently involve the surrounding soft tissue.

Ablation prior to cement injection may also be indicated whenever local tumour control is indicated, as cementoplasty has little to no antitumoral effect and has been reported to transiently increase the level of the cancer circulating cells in the minutes following injection [START_REF] Tomasian | Spine Cryoablation: Pain Palliation and Local Tumor Control for Vertebral Metastases[END_REF][START_REF] Tomasian | Simultaneous Bipedicular Radiofrequency Ablation Combined with Vertebral Augmentation for Local Tumor Control of Spinal Metastases[END_REF][START_REF] Anselmetti | Temperature measurement during polymerization of bone cement in percutaneous vertebroplasty: an in vivo study in humans[END_REF][START_REF] Mohme | Circulating Tumour Cell Release after Cement Augmentation of Vertebral Metastases[END_REF]. The predominance of monopolar RFA may seem strange in an era where bipolar RFA, cryoablation and even MW are more and more promoted for bone ablation [START_REF] Callstrom | Percutaneous image-guided cryoablation of painful metastases involving bone: multicenter trial[END_REF][START_REF] Bornemann | Temperature distribution during radiofrequency ablation of spinal metastases in a human cadaver model: Comparison of three electrodes[END_REF][START_REF] Kinczewski | Microwave Ablation for Palliation of Bone Metastases[END_REF]. The most likely explanation comes with the year with which the papers were issued, when monopolar RFA was the main if not the only modality available [START_REF] Goetz | Percutaneous image-guided radiofrequency ablation of painful metastases involving bone: a multicenter study[END_REF].

The use of implant devices in association with cementoplasty for lesions located in the long bones but not in the acetabulum makes sense on a biomechanical point of view: the high resistance of cement to compression load is adapted to ensure bone consolidation in the acetabulum, while the poor resistance of cement to shear, binding and torsion stresses makes it unsuitable as a stand-alone intervention for metaphyseal/diaphyseal lesions with a high risk of impending fractures [START_REF] Cornelis | Augmented osteoplasty for proximal femur consolidation in cancer patients: Biomechanical considerations and techniques[END_REF][START_REF] Cazzato | Biomechanical effects of osteoplasty with or without Kirschner wire augmentation on long bone diaphyses undergoing bending stress: implications for percutaneous imagingguided consolidation in cancer patients[END_REF][START_REF] Deschamps | Cementoplasty of metastases of the proximal femur: is it a safe palliative option?[END_REF][START_REF] Cazzato | Percutaneous consolidation of bone metastases: strategies and techniques[END_REF]. Interestingly, all the lesions localized in the long bones and that were treated by surgeons underwent nail fixation and cementoplasty, while only 15% of the procedures in the long bones performed by IRs were associated with other implant devices, for which little to no biomechanical validation exists. It is possible that the procedures performed by orthopaedics were more driven towards a mechanical stabilization than the one performed by IRs where pain control was the major concern. As demonstrated in another review, standalone cementoplasty in the long bones is effective to achieve pain alleviation and to improve mechanical function but fracture is the most frequent complication [START_REF] Cazzato | Percutaneous Long Bone Cementoplasty for Palliation of Malignant Lesions of the Limbs: A Systematic Review[END_REF]. In any case, mechanical stabilization should always be kept in mind when performing percutaneous cementoplasty in the long bones, and additional fixation using nails/screws always be balanced [START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Cazzato | Percutaneous consolidation of bone metastases: strategies and techniques[END_REF][START_REF] Cazzato | Percutaneous image-guided screws meditated osteosynthesis of impeding and pathological/insufficiency fractures of the femoral neck in non-surgical cancer patients[END_REF][START_REF] Buy | Image-Guided Bone Consolidation in Oncology[END_REF][START_REF] Deschamps | Percutaneous Fixation by Internal Cemented Screw for the Treatment of Unstable Osseous Disease in Cancer Patients[END_REF].

The needle size used to perform cement injection ranged from 10G to 13G in almost all cases, which is similar to spinal cementoplasty [START_REF] Tsoumakidou | CIRSE Guidelines on Percutaneous Vertebral Augmentation[END_REF]. However, one major difference with spine is the amount of cement that is injected. As shown in this review, the volume of cement was extremely variable. On average, the amount of injected cement was 8,8ml, which is much higher than the mean value for a spinal vertebroplasty [START_REF] Luo | Vertebroplasty: only small cement volumes are required to normalize stress distributions on the vertebral bodies[END_REF][START_REF] Tsoumakidou | CIRSE Guidelines on Percutaneous Vertebral Augmentation[END_REF][START_REF] Sun | The Optimal Volume Fraction in Percutaneous Vertebroplasty Evaluated by Pain Relief, Cement Dispersion, and Cement Leakage: A Prospective Cohort Study of 130 Patients with Painful Osteoporotic Vertebral Compression Fracture in the Thoracolumbar Vertebra[END_REF]. This review also outlines that a significant number of procedures, especially in the long bones, required a volume greater than 10ml. Such volume exceeds the usual volume of cement available in most of the commercially available cement kits. Surprisingly, only one paper over the 30 included for that review described in detail the technical approach to deal with such large volume [START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF]. Hence, in that paper focusing on pelvic osteoplasty, the authors injected simultaneously in 2 trocars with the idea to provide a coalescence of the different cement streams while injecting as much as possible. In all other articles there was no/only brief description of the technique, which consisted in most of the cases to insert an additional needle to inject more cement whenever required, but without further specification [START_REF] Kim | Closed intramedullary nailing with percutaneous cement augmentation for long bone metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Cotten | Malignant acetabular osteolyses: percutaneous injection of acrylic bone cement[END_REF][START_REF] Weill | Acetabulum malignancies: technique and impact on pain of percutaneous injection of acrylic surgical cement[END_REF][START_REF] Deschamps | Percutaneous stabilization of impending pathological fracture of the proximal femur[END_REF][START_REF] Wallace | Combination acetabular radiofrequency ablation and cementoplasty using a navigational radiofrequency ablation device and ultrahigh viscosity cement: technical note[END_REF][START_REF] He | Feasibility of percutaneous cementoplasty combined with interventional internal fixation for impending pathologic fracture of the proximal femur[END_REF]. Besides, filling of the lesions is rarely reported, and is inferior to 60% in the few papers publishing the data [START_REF] Moser | Cementoplasty of pelvic bone metastases: systematic assessment of lesion filling and other factors that could affect the clinical outcomes[END_REF][START_REF] Colman | Percutaneous Acetabuloplasty Compared With Open Reconstruction for Extensive Periacetabular Carcinoma Metastases[END_REF][START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF]. There is no standardized volume of cement for extra-spinal cementoplasties and most authors advocate to fill the lesion and the surrounding cancellous bone as much as possible to provide optimal bone consolidation [START_REF] Kurup | Balloon-assisted osteoplasty of periacetabular tumors following percutaneous cryoablation[END_REF][START_REF] Sutter | A biomechanical evaluation of femoroplasty under simulated fall conditions[END_REF]. Still, little is known how to technically achieve such filling while mitigating the risk of leakages. Moreover, the impact of the degree of lesion filling on the mechanical outcome is unclear in clinical practice.

In conclusion, percutaneous cementoplasty is an effective tool to manage pain associated with bone metastases. There is however a clear lack of standardization of the technique among the different publications.

Figures

  Figures

Fig. 1

 1 Fig.1: flow chart of article selection

  Fig.1: flow chart of article selection