Fayçal Houfani
email: faycal.houfani@gmail.com

Didier Mainard

Brice Rubens-Duval

Pierre-Emmanuel Papin

Gilles Pasquier

Matthieu Ehlinger

Rotating-hinge prosthesis for aseptic revision knee arthroplasty: A multicentre retrospective study of 127 cases with a mean follow-up of five years

Keywords: Knee arthroplasty, Revision surgery, Hinged prosthesis, Rotating-hinge prosthesis, Survival, Complications, 1

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

Introduction

The good outcomes currently provided by total knee arthroplasty (TKA) [START_REF] Kurtz | Future clinical and economic impact of revision total hip and knee arthroplasty[END_REF] explain the sharp rise in TKA procedures [START_REF] Losina | The dramatic increase in total knee replacement utilization rates in the United States cannot be fully explained by growth in population size and the obesity epidemic[END_REF][START_REF] Berger | Longterm follow-up of the Miller-Galante total knee replacement[END_REF], which are being performed at increasingly younger ages. This success has led inevitably to an increased number of revision TKAs in the medium and long terms [START_REF] Robertsson | The Swedish Knee Arthroplasty Register 1975-1997: an update with special emphasis on 41,223 knees operated on in 1988-1997[END_REF][START_REF]The Swedish Knee Arthroplasty Register (SKAR)[END_REF] and to an increase in repeated revisions [START_REF] Yu | Re-revision total knee arthroplasty: epidemiology and factors associated with outcomes[END_REF][START_REF] Mckie | Registry The New Zealand joint registry twenty year report[END_REF].

The main reasons for TKA revision, apart from prosthetic joint infection and periprosthetic fractures, are aseptic loosening (19-40%), instability (6-26%), polyethylene wear (0-25%), extensor apparatus failure, and material failure [START_REF] Postler | Analysis of Total Knee Arthroplasty revision causes[END_REF][START_REF] Parratte | Instability after total knee arthroplasty[END_REF][START_REF] Vince | The unstable total knee arthroplasty: causes and cures[END_REF][START_REF] Sharkey | Why are total knee arthroplasties failing today--has anything changed after 10 years?[END_REF][START_REF] Pietrzak | Have the frequency of and reasons for revision total knee arthroplasty changed since 2000? Comparison of two cohorts from the same hospital: 255 cases (2013-2016) and 68 cases (1991-1998[END_REF]. In France, the 2000 SoFCOT symposium on aseptic TKA revision found the following reasons in a cohort of 473 patients: loosening, 35.9%; patellar complications and tendon ruptures, 18.8%; stiffness, 15.2%; tibio-femoral laxity, 13.7%; mechanical failure, 6.9%; and unexplained pain, 6.5% [START_REF] Burdin | Les reprises de prothèses totales de genou-Symposium de la SOFCOT 2000[END_REF]. Non-hinged knee prostheses (posterior-stabilized, semi-constrained) also produce satisfactory outcomes when used for revision arthroplasty [START_REF] Lachiewicz | Clinical and radiographic results of the Total Condylar III and Constrained Condylar total knee arthroplasty[END_REF][START_REF] Peters | Revision total knee arthroplasty with a cemented posterior-stabilized or constrained condylar prosthesis: a minimum 3-year and average 5-year follow-up study[END_REF]. However, patients with severe instability due to failure of the capsule and ligaments require a greater level of constraint [START_REF] Barrack | Evolution of the rotating hinge for complex total knee arthroplasty[END_REF][START_REF] Westrich | Rotating hinge total knee arthroplasty in severly affected knees[END_REF][START_REF] Boelch | Revision knee arthroplasty with rotating hinge systems in patients with gross ligament instability[END_REF][START_REF] Putman | Total knee replacement on more than 20° valgus: A case control study[END_REF]. Increased constraint does not seem to diminish the functional improvements. The constrained condylar knee prosthesis, which is the most widely used design in patients with instability or deformity, produces excellent long-term outcomes [START_REF] Cholewinski | Long-term outcomes of primary constrained condylar knee arthroplasty[END_REF], but has limitations in patients with severe instability. Although much has been written about TKA revision, few studies have focussed on aseptic TKA revision using a rotating-hinge prosthesis [START_REF] Joshi | Is there a place for rotating-hinge arthroplasty in knee revision surgery for aseptic loosening?[END_REF][START_REF] Neumann | Follow-up of a modular rotating hinge knee system in salvage revision total knee arthroplasty[END_REF][START_REF] Rodríguez-Merchán | Revision knee arthroplasty with a rotating-hinge design in elderly patients with instability following total knee arthroplasty[END_REF].

The objective of the multicentre retrospective* study reported here was to evaluate the clinical and radiological outcomes of aseptic knee arthroplasty revision performed using a rotating-hinge prosthesis. Our working hypothesis was that the rotating-hinge knee prostheses currently used in France provide significant improvements in function and selfsufficiency of patients undergoing revision TKA, with outcomes comparable to those reported with constrained condylar knees.

Patients and methods

Study design

We conducted a multicentre retrospective study under the auspices of the SoFCOT and within the framework of the 2017 symposium on the place of rotating-hinge prostheses in France. The 17 centres were located in Amiens, Bordeaux, Clamart, Dijon, Fort de France, Grenoble, Lille, Lyon, Nancy, Nantes, Nîmes, Paris, Poitiers, Saint Etienne, Strasbourg, Toulouse, and Tours. We included all patients who had had revision of total knee arthroplasty or unicompartmental arthroplasty using a rotating-hinge prosthesis, for any of the following aseptic reasons: (a) aseptic loosening, (b) major instability; (c) severe bone loss, (d) failure of the extensor apparatus; (e) bulkiness of the prosthesis, (f) polyethylene wear, and (g) failure of the material. Failure, and therefore the survival rate, was defined as surgical revision for any reason. We included 127 patients (127 knees). One patient with missing clinical and radiological data was excluded (Figure 1).

Methods

We recorded the usual data: age, sex, age at revision surgery, body mass index (BMI), American Society of Anesthesiologists (ASA) score [START_REF] Fitz-Henry | The ASA classification and peri-operative risk[END_REF], hip-knee-ankle (HKA) angle, mechanical axis before revision (varus or valgus knee), surgical approach, whether a procedure was performed on the anterior tibial tuberosity, and previous surgical procedures on the knee.

The clinical assessments before surgery and at last follow-up included an evaluation of self-sufficiency by the Devane score [START_REF] Devane | Three-dimensional polyethylene wear of a press-fit titanium prosthesis. Factors influencing generation of polyethylene debris[END_REF] and of function by the International Knee Society (IKS) score [START_REF] Debette | French adaptation of the new Knee Society Scoring System for total knee arthroplasty[END_REF]. Intra-operative and post-operative clinical complications were recorded.

The radiographic assessment consisted in standing coronal and lateral views, a skyline view, and a long-leg view. These views were obtained before surgery and at last follow-up.

Bone loss was assessed by determining the class in the Anderson Orthopedic Research

Institute (AORI) classification [START_REF] Engh | A classification of bone defects[END_REF].

Statistical analysis

The anonymised data were entered into a server. The statistical analyses were done at the Lille university hospital.

The first step consisted in a descriptive analysis of the parameters. Continuous variables were described as mean, standard deviation, and range and categorical variables as percentages. Then, changes in the functional scores were evaluated by applying Student's test, with values of p less than 0.05 taken to indicate significant differences. Survival curves were plotted according to Kaplan-Meier.

Results

Description of the cohort

We included 127 patients (127 knees). There were 79 females and 48 males. Mean age at revision was 69.5±11.8 years (range, 23-89 years). The mean BMI was 29.3 (range, 17.9-47.6) and the mean ASA score was 2.38±0.6 (range, 1-4). Mean follow-up was 67.3±36.9 months (range, 13-180 months) (Table 1 and Figure 2).

Mean time from primary TKA to revision was 85 months (range, 2-302 months). Aseptic loosening was the most common reason for revision (Figure 3), with 59% of patients, followed by instability (39%), mechanical failure (17%) (material breakage, wear and luxation of the polyethylene), and extensor apparatus rupture (6%).

The mean preoperative values were 91 for the IKS score and 2.7±1 (range, 1-5) for the Devane score. Tables 2 and3 report details on the intraoperative data and on the implants used for TKA exchange.

At inclusion, 12 (9%) patients had died, after a mean time since surgery of 69 months (range, 26-151 months). As their follow-up duration was deemed sufficient and they had no missing clinical or radiological data, these 12 patients were included.

Clinical outcomes

After the mean follow-up of 67.3 months, significant improvements were seen in the total IKS score (from 91 to 133; p<0.0001), IKS function score (from 44 to 56; p=0.0007), IKS knee score (from 47 to 77; p<0.0001), and pain score (from 17 to 37; p<0.0001) (Figure 4). Mean flexion was also improved, from 92° to 96° (p=0.03).

Despite the overall improvement in the function of the operated knee, some loss of self-sufficiency was noted, with a decline in the Devane score from 2.7 to 2.26 (p=0.0003).

The numbers of patients in the Devane groups 1 and 2 (with low self-sufficiency) increased, from 12 to 28 and from 55 to 57, respectively; whereas the numbers in the Devane groups 3, 4, and 5 (with a higher level of activity) decreased, from 36 to 24, from 10 to 4, and from 15 to 9, respectively.

Complications

Of the 127 patients, 37 (29%) experienced one complication (29%) (Table 4).

-Infection developed in 12 (9.4%) patients and consistently required surgery. The -Peri-prosthetic fractures developed in 7 (5.5%) patients, who were managed by internal fixation.

-Rupture of the extensor apparatus occurred in 6 (4.7%) patients.

-Rupture of the femoral extension stem occurred in 1 (0.8%) patient and was managed by replacement of the component.

In sum:

-106 (83.4%) prostheses were still in place with no evidence of loosening at last follow-up, including 2 (1.6%) infected sealed prostheses.

-18 (14.2%) prostheses were no longer present as they had been exchanged due to septic or aseptic loosening, removed to perform arthrodesis, or removed during transfemoral amputation.

-3 (2.4%) loosened prostheses were not treated surgically, due either to a contraindication to anaesthesia or to complete absence of pain and functional repercussions.

Survival rate

When failure of the rotating-hinge prosthesis was defined as all-cause surgical revision the survival rate was 87% (95% confidence interval [95%CI], 0.81-0.93]) after 1 year, 77% (95%CI, 0.70-0.85] after 5 years, and 73% at last follow-up (95%CI, 0.65-0.81) (Figure 5).

Discussion

TKA revision surgery often raises technical challenges, particularly as the patients may have had multiple knee surgeries and are frequently elderly and frail. The hinged knee prosthesis was typically reserved for elderly patients with low functional demands, given the very high complication rates seen with the first-generation implants [START_REF] Aubriot | GUEPAR hinge knee prosthesis[END_REF]. However, recent reports show that hinged prostheses are no longer reserved for salvage procedures [START_REF] Kowalczewski | Primary rotating-hinge total knee arthroplasty: good outcomes at mid-term follow-up[END_REF]. The latest report issued by the French Drug and Healthcare Product Safety Agency (ANSM) [START_REF] Ansm | Surveillance des dispositifs médicaux à risque : Prothèses totales de genou (PTG) Juillet[END_REF] states that, in 2013, hinged prostheses were used in 573 (0.7%) of 80 819 TKA procedures, a 21% increase over 2008. In 2017, a survey conducted by the SoFCOT symposium among prosthesis manufacturers demonstrated that about 3000 hinged prostheses were implanted in France. Hinged prostheses thus accounted for 3% of all TKA procedures, and most were rotating-hinge prostheses. These data confirm the place held by the rotating-hinge prosthesis in our therapeutic armamentarium. In 2018, the Swedish TKA register recorded 14 957

primary TKAs in 2017, including 51 (0.3%) hinge prostheses. From 2007 to 2016, primary hinged-prosthesis TKA was performed for 598 (0.5%) knees. Over the same period, hinged prostheses were used for 7.35% of first TKA revisions [START_REF] Robertsson | The Swedish Knee Arthroplasty Register -Annual Report[END_REF]. The total number of hinged prostheses used, including repeat revisions, was not recorded in this register.

Our hypothesis was confirmed in that knee function improved significantly. The functional outcomes in our cohort were satisfactory. Marked improvements were seen after surgery compared to the preoperative values, with a mean 30-point increase in the IKS knee score (p<0.001) and a 12-point increase in the IKS function score (p<0.001). Despite these functional improvements, self-sufficiency did not increase, as shown by the 0.44-point decrease in the Devane score. This loss of self-sufficiency is undoubtedly ascribable to the age of the patients (mean age, 69.5 years) and to their many comorbidities, some of which impaired the ability to walk. However, we found no supporting statistical correlation in our study. The Devane score is probably not relevant for assessing the activity of patients after revision arthroplasty, as the progression of comorbidities and presence of other prostheses decrease the Devane score.

Although statistically significant, the clinical improvement in our population was less marked than in other studies of rotating-hinge prostheses used for aseptic TKA revision. In a study of 24 patients, Neumann et al. [START_REF] Neumann | Follow-up of a modular rotating hinge knee system in salvage revision total knee arthroplasty[END_REF] respectively, for our study (14-16) (Table 5). On the other hand, our clinical outcomes are comparable to those observed for other causes of TKA revision, such as infection and aseptic trauma [START_REF] Korim | A systematic review of endoprosthetic replacement for non-tumour indications around the knee joint[END_REF].

The complication rate in the literature varies from 4% to 36% [START_REF] Joshi | Is there a place for rotating-hinge arthroplasty in knee revision surgery for aseptic loosening?[END_REF][START_REF] Sheng | Patient outcome following revision total knee arthroplasty: a meta-analysis[END_REF][START_REF] Cottino | Long-term results after total knee arthroplasty with contemporary rotating-hinge prostheses[END_REF][START_REF] Guenoun | Complications following rotating hinge Endo-Modell (Link) knee arthroplasty[END_REF] and was 29% in our cohort. Joshi et al. [START_REF] Joshi | Is there a place for rotating-hinge arthroplasty in knee revision surgery for aseptic loosening?[END_REF] report comparable results with 27% of complications. In their meta-analysis, Sheng et al. [START_REF] Sheng | Patient outcome following revision total knee arthroplasty: a meta-analysis[END_REF] found a mean complication rate of 19%. This lower rate compared to our study may be ascribable to the inclusion in the meta-analysis of cohorts treated by revision with posterior-stabilized or constrained condylar knees. This complication rate is higher than for primary TKA [START_REF]The Swedish Knee Arthroplasty Register (SKAR)[END_REF][START_REF] Poss | Factors influencing the incidence and outcome of infection following total joint arthroplasty[END_REF] and for revision with less constrained prostheses [START_REF] Kim | Long-term clinical outcomes and survivorship of revision total knee arthroplasty with use of a constrained condylar knee prosthesis[END_REF][START_REF] Kim | Revision total knee arthroplasty with use of a constrained condylar knee prosthesis[END_REF]. No case of intra-prosthetic dislocation was recorded in our study. This rare complication is typical of rotating-hinge prostheses and is dependent on their design [START_REF] Cavaignac | Recurring intraprosthetic dislocation of rotating-hinge total knee prosthesis. Effect of implant design on intrinsic stability[END_REF].

Infection remains a common cause of failure and revision after TKA exchange by a rotating-hinge prosthesis [START_REF] Poss | Factors influencing the incidence and outcome of infection following total joint arthroplasty[END_REF]. The rate was 9.4% in our study, with 12 patients (including 5

in whom the unfavourable course required either transfemoral amputation [n=3] or arthrodesis [n=2]). These numbers are higher than in the studies of aseptic TKA revision by Merchan, Joshi, and Neuman in which there was 1 case of infection managed by two-stage exchange, 2 cases of septic loosening managed by arthrodesis, and no cases of post-operative infection, respectively. The high rate of infection in our study is ascribable to the characteristics of our population, with numerous comorbidities associated with a high risk of infection (high ASA score, diabetes, obesity) and often with a history of multiple surgeries on the knee [START_REF] Rodríguez-Merchán | Revision knee arthroplasty with a rotating-hinge design in elderly patients with instability following total knee arthroplasty[END_REF]. Severe infection required amputation in 3 of our patients. In the studies of hinged prostheses for knee tumours or trauma done at the 2017 SoFCOT symposium, the rates of infection were 16% and 15%, respectively [START_REF] Mazaleyrat | Survival and complications in hinged knee reconstruction prostheses after distal femoral or proximal tibial tumor resection: A retrospective study of 161 cases[END_REF][START_REF] Kouyoumdjian | Hinged total knee arthroplasty for fracture cases: Retrospective study of 52 patients with a mean follow-up of 5 years[END_REF]. However, the high rate of infection after hinged prosthesis implantation is not related only to multiple surgeries to treat a tumour or traumatic injury. Abdulkarim et al. performed a meta-analysis of primary TKA with a rotating-hinge knee prosthesis, from which they excluded tumours and trauma, and found an infection rate of up to 14% [START_REF] Abdulkarim | Rotating-hinge knee prosthesis as a viable option in primary surgery: Literature review & meta-analysis[END_REF]. Infection was the cause of 31.5% of treatment failures in this meta-analysis. These data indicate that the longer operative time and greater aggressiveness for the tissues increase the risk of infection.

Five-year survival rates vary in the literature from 52% to 90% [START_REF] Cottino | Long-term results after total knee arthroplasty with contemporary rotating-hinge prostheses[END_REF][START_REF] Gudnason | Implant survival and outcome after rotating-hinge total knee revision arthroplasty: a minimum 6-year follow-up[END_REF][START_REF] Pour | Rotating hinged total knee replacement: use with caution[END_REF][START_REF] Bistolfi | Endo-Modell rotating-hinge total knee for revision total knee arthroplasty[END_REF][START_REF] Smith | Comparison of mechanical and nonmechanical failure rates associated with rotating hinged total knee arthroplasty in nontumor patients[END_REF] irrespective of the type of hinged prosthesis used and of the reason for revision. With our severe definition of failure as all-cause revision surgery, the survival rate was 77%, which is toward the lower middle of previously reported values. However, when failure is defined as septic or aseptic loosening, the survival rate at last follow-up (mean, 67.3 months) is 82%. In another study, when failure was defined as revision for aseptic loosening, the 10-year survival rate was nearly 90%, whereas it was 65% when failure was defined as all-cause revision [START_REF] Gudnason | Implant survival and outcome after rotating-hinge total knee revision arthroplasty: a minimum 6-year follow-up[END_REF].

Our study shows that some surgeons prefer the rotating-hinge prosthesis over constrained prostheses such as the constrained condylar prosthesis, even for knees without marked hyperlaxity, which is theoretically the indication for rotating-hinge prostheses used for the first TKA revision. The SoFCOT symposium held in 2000 on TKA revision had already found that hinged prostheses were sometimes chosen routinely for TKA revision [START_REF] Burdin | Les reprises de prothèses totales de genou-Symposium de la SOFCOT 2000[END_REF].

The best type of implant for TKA revision remains a matter of debate. The rotatinghinge prosthesis has the main advantage of requiring no support from the ligaments.

Hermans et al. [START_REF] Hermans | Hinged versus CCK revision arthroplasty for the stiff total knee[END_REF] compared the rotating-hinge prosthesis to the constrained condylar knee in patients undergoing TKA revision for stiffness requiring extensive joint release. The functional outcomes were better with the rotating-hinge prosthesis. However, in a study by Rhöner et al. [START_REF] Röhner | Good clinical and radiological results of total knee arthroplasty using varus valgus constrained or rotating hinge implants in ligamentous laxity[END_REF] of primary TKA for laxity, the rotating-hinge prosthesis and the constrained condylar knee produced comparable results in terms of laxity, mobility, and satisfaction. The meta-analysis by Yoon et al. [START_REF] Yoon | Rotating hinge knee versus constrained condylar knee in revision total knee arthroplasty: A meta-analysis[END_REF] on TKA revision found a higher survival rate with the rotating-hinge prosthesis than with the constrained condylar knee after less than 5 years (87.4% vs. 75%) contrasting with better survival of the constrained condylar knee after 5 to 10 years (81.3% vs. 83.8%). The complication rate was higher with the rotatinghinge knee (Table 6).

In our study, prosthetic wedges were generally used to handle minor epiphyseal and metaphyseal bone defects, whereas bone grafts were used for larger defects. No preformed tantalum cones were used, although they have been reported to provide good outcomes [START_REF] Girerd | Total knee arthroplasty revision with trabecular tantalum cones: Preliminary retrospective study of 51 patients from two centres with a minimal 2-year follow-up[END_REF][START_REF] Boureau | Tantalum cones and bone defects in revision total knee arthroplasty[END_REF]. Their recent introduction in France and high cost explain that they were not used in our study.

Our study has several limitations. The retrospective and multicentre design should be borne in mind, although it allowed us to obtain one of the largest cohorts in the literature.

The use of different rotating-hinge knee models in the study centres may make comparisons difficult. To date, 16 models of rotating-hinge prosthesis are available on the French market.

Finally, comparisons of our results to those reported previously are hindered by the heterogeneous surgical indications in most studies. We were unable to analyse the results and complications for each reason for TKA revision because, at patient inclusion, the surgeon could give one or more reasons for revision of the same knee. Such an analysis would enable the identification, before surgery, of the ideal indication for the rotating-hinge prosthesis and the required level of constraint [START_REF] Girard | Total knee arthroplasty in valgus knees: predictive preoperative parameters influencing a constrained design selection[END_REF].

Despite these limitations, this study provides an overview of the use of rotating-hinge prostheses in France and shows that this type of prosthesis is increasingly used with ever better outcomes.

Conclusion

The rotating-hinge prosthesis is an indispensable component of the therapeutic armamentarium to treat patients with major ligament failure, certain comminuted fractures of osteoporotic bone, and of course tumours [START_REF] Lustig | Hinged knee prostheses: To be used with due consideration, but indispensable in complex situations[END_REF][START_REF] Pasquier | The role of rotating hinge implants in revision total knee arthroplasty[END_REF]. TKA revision using a rotating-hinge prosthesis is technically challenging and was historically reserved for salvage surgery. The outcomes obtained with the more recent generations of rotating-hinge prosthesis have resulted in greater use outside the typical indications.

Data in the literature clearly demonstrate that outcomes of aseptic TKA using a rotating-hinge prosthesis are satisfactory overall. The good functional outcomes obtained in our study confirm these data but should be considered in the light of the high rate of mechanical and septic complications (29%) and of the absence of gains in self-sufficiency.

In addition, revising rotating-hinge TKA often raises complex technical challenges [START_REF] Massin | Removal of infected cemented hinge knee prostheses using extended femoral and tibial osteotomies: six cases[END_REF] associated with complications. The medium-term survival rate is lower than with constrained condylar prostheses in earlier studies, although we used a very broad definition of failure.

Patients must be selected with discernment and informed of the risk of complications.

  treatment consisted in single-stage exchange in 1 patient and two-stage exchange in 4 patients; none of these 5 patients experienced recurrent infection. Arthrodesis was performed in 2 patients, transfemoral amputation in 3 patients, and joint lavage with suppressive antibiotic therapy in 2 patients. -Aseptic loosening occurred in 11 (8.6%) patients at a mean of 40.7 months (range, 3-96 months) after revision surgery. Eight of these patients required surgery, which consisted in removal and repositioning of the same prosthesis in 4 patients, a change of the tibial component in 3 patients, and a change of the femoral component in 1 patient. The remaining 3 patients did not undergo surgery.

Figure 1 .Figure 2 .Figure 3 .Figure 4 .Figure 5 .

 12345 Figure 1. Flow diagram

Figure 2

 2 Figure 2.

Figure 5 .

 5 Figure 5.

  reported a 50-point increase in the IKS function score after 56 months, while Joshi et al.[START_REF] Joshi | Is there a place for rotating-hinge arthroplasty in knee revision surgery for aseptic loosening?[END_REF] obtained a 28-point increase after 94 months in 78 patients and Merchan et al.[START_REF] Rodríguez-Merchán | Revision knee arthroplasty with a rotating-hinge design in elderly patients with instability following total knee arthroplasty[END_REF] a 20-point increase after 87 months in 96 patients. These differences are ascribable to the higher pre-operative IKS scores in our population than on average in the literature: the IKS knee scores ranged from 25 to 38 and the IKS function scores from 33 to 35 in the studies by Merchan, Joshi, and Neumann compared to47 and 44,

Table 1 .

 1 Main features in the study population

	Sex (F/M)	79 (62%)/48 (38%)
	Mean age, years	69.5±12 (42-89)
	ASA score [24] mean 2.38
	ASA 1	3 (2.4%)
	ASA 2	69 (54.3%)
	ASA 3	46 (36.2%)
	ASA 4	1 (0.8%)
	missing	8 (6.3%)
	Morphotype before revision
	HKA, mean	174°
	Varus Knee	68 (63%)
	Valgus Knee	20 (19%)
	Normal alignment	19 (18%)
	Mean flexion before revision	92°±25 (0-130)
	IKS Total	91
	IKS function	44
	IKS knee	47
	IKS pain	17
	Devane score [25] mean before revision: 2.7
	Devane 1	12 (9.4%)
	Devane 2	55 (43.3%)
	Devane 3	35 (27.6%)
	Devane 4	10 (7.9%)
	Devane 5	15 (11.8%)

Table 2 :

 2 Intra-operative data from the study cohort

	Medial approach						90%
	Procedure on the anterior tibial tuberosity			23%
	85 months (2-302) on average between the primary knee arthroplasty a
				and the revision
	50 % of patients had had a single operation on the knee before
	implantation of the rotating-hinge prosthesis
	Number of
	operations
		1	2	3	4 5	6	7	8	9	>10
	before the
	revision
	Patient (n)	63 36 17 5 3	1	0	1	0	1
	Type of primary prosthesis before revision
	-Total knee arthroplasty				120 (94.5%)
	-Unicompartmental knee
								7 (5.5%)
	arthroplasty
	Other procedure on the knee
								8 (6%)
	-Meniscectomy
	-Valgus high tibial osteotomy			12 (9%)
	Implant fixation modality (cemented /cementless)
	-Cemented component: 112 femoral components (88 %) and 108
	tibial plateaux (85 %)
	-Cemented stem extension: 66 tibial and 66 femoral (52 %)
	Filling of bone defects
	wedges femoral							30 (24%)
	tibial							27 (21%)
	both							10 (8%)
	allograft							14 (11%)
	autograft							2 (1.5%)

a either total knee arthroplasty or unicompartmental knee arthroplasty

Table 3 .

 3 Rotating-hinge prostheses used for the revision

	Manufacturer	Prosthesis	N	%
	ZIMMER	RHK NexGen	40	31.5
	STRYKER	MRH	40	31.5
	LINK	Endomodel	18	14.2
	STANMORE	METS	7	5.5
	SMITH & N	RT PLUS	4	3.1
	BBRAUN	AXEL	3	2.4
		Enduro	2	1.6
	IMPLANTCAST	MUTARS KRI	1	0.8
	Other		1	0.8
	Missing		11	8.6

Table 4 .

 4 Post-operative complications

	Complications	n	%
	Infections	12	9.4
	Aseptic loosening	11	8.6
	Peri-prosthetic fracture	7	5.5
	Rupture of the extensor	6	4.7
	apparatus
	Hardware failure	1	0.8
	Total	37	29

Table 5 .

 5 Revision using rotating-hinge prostheses: review of the literature

							Range of
		Number of	Mean age	Mean follow-	IKS Knee	IKS function	Motion
		patients	(years)	up	(pts)	(pts)	Extension -
							Flexion
	Joshi (2008)						-4° -> -1°
		78	72	5 years	38 -> 86	33 -> 61
	Endomodell (Link)						103° -> 97°
	Neumann (2012)
							0°
	RHK Nexgen	24	67	4.6 years	25 -> 91	35 -> 85
							72 -> 116°
	(Zimmer)
	Rodriguez-Merchan
							-15° -> -5°
	(2015)	96	79	7.3 years	33 -> 79	34 -> 54
							80° -> 120°
	Endomodell (Link)
							-4° -> 0°
	Sofcot (2017)	127	69.5	5.8 years	47 -> 77	44 -> 56
							91.6 -> 96°

Table 6 .

 6 Comparison to revision using constrained condylar prostheses

			Sanz-Ruiz	Kim 2009
			2015 [50]	[38] (JBJS-Am)
		Our study	(BMC)
	Revisions (n)	127	47	114
	Mean follow-up (months) 67.3	98.4	86.4
	Mean age (years) 69,5	73	65
	Post-op. complications	37	11	10
	-Infections	12	2	2
	-Aseptic loosening	11	2	4
	-Fracture	7	2	0
	-Rupture of the	6	0	3
	extensor
	apparatus
	-Implant failure	1	0	1
	-Instability	0	1	0
	Progression IKS knee	47 -> 78	40 -> 80	35 -> 90
	Progression IKS function	44 -> 56	32 -> 56	16 -> 64
	Progression Flexion	92 -> 96	90 ->106	95 -> 106
	Survival rate	77 % at 5	80 % at 6.5	96 % at 10
		years	years	years

Acknowledgements

-Symposium : Matthieu Ehlinger, Pierre Marz, Adrien d'Ambrosio, Bertrand Boyer, Thomas Neri, Pierre-Emmanuel Papin, Didier Mainard, Faycal Houfani, Brice Rubens-Duval, Jean-Louis Rouvillain, Pascal Kouyoumdjian, Henry Jarnouhen de Villartay, Etienne Cavaignac, Antoine Gabrion, Etienne Caron, Nicolas Verdier, Mathieu Mazaleyrat, Guillaume Auberger, Denis Waast, Gilles Pasquier, Gualter Vaz -Lille Biostatistics Department: Mme Ramdane Nassima -CALIMED santé: Barbara Guérin

Funding

Study conducted with the financial support of the SoFCOT

Contributions of each author

FH, DM, GP, ME: drafted the manuscript BRD, PP: revised the manuscript for important intellectual content

Conflicts of interest