Antoine Moraux
email: antoinemorauxamoraux@yahoo.com

Thomas Le Corroller

Aurelien Aumar

& Aurelien Aumar

Stefano Bianchi

Stenosing tenosynovitis of the extensor digitorum tendons of the hand: clinical and sonographic features

Keywords: Tendon entrapment, Ultrasound, Wrist, Hand

Stenosing tenosynovitis of the extensor digitorum tendons of the hand: clinical and sonographic features.

Introduction

Stenosing tenosynovitis (ST) is a frequently encountered clinical condition that may involve the first extensor compartment of the wrist in the De Quervain tenosynovitis or the flexor digitorum tendons in the trigger finger. ST affecting the extensor digitorum communis (EDC) tendons is rather unusual with only a few reports in the literature [START_REF] Gooding | Tenosynovitis of the wrist. A sonographic demonstration[END_REF][START_REF] Wilson | Extensor tendon impingement in a gymnast[END_REF][START_REF] Vanheest | Extensor retinaculum impingement in the athlete: a new diagnosis[END_REF][START_REF] Khazzam | Extensor tendon triggering by impingement on the extensor retinaculum: a report of 5 cases[END_REF][START_REF] Mahajan | Surgical treatment of tenosynovitis of extensor tendons of fourth compartment of wrist in nonrheumatoid patients-a case series of 10 patients in India[END_REF]. Yet, we herein describe the ultrasound (US) features of extensor digitorum communis stenosing tenosynovitis (EDCST) in eighteen patients. To the best of our knowledge, this is the first study providing a thorough description of the static and dynamic US features of EDCST.

Materials and methods

This study was approved by the institutional review boards with permission to review medical records; and waivers were issued for written informed consent.

A retrospective search in the radiologic information systems of two separate Institutions was performed to identify all patients presenting EDCST on a total of 986 wrist ultrasound examinations between January 2010 and September 2019 using the following keywords: stenosing tenosynovitis, extensor digitorum tendons, tendon entrapment, tendon impingement, and wrist. Medical records were reviewed to assess patients' past history, EDCST treatment, complications, and clinical outcomes. Patients with a past history of either previous surgery of the affected wrist and proven or suspected rheumatologic disease were excluded. A total of 18 patients (ten males and eight females; mean age, 57.4 years) could be identified and finally included in this study. The follow-up period was variable with ten patients (10/18; 55%) presenting at least 1-year clinical follow-up in our Institutions. The following patient data were collected: age, gender, contributing factors, symptom duration, triggering factors, and treatments. US examinations were performed by two senior radiologists (AM and SB) with 12 and 32 years of experience, respectively, in musculoskeletal US.

US examinations were carried out over a 10-year period using either an Affiniti (Philips Healthcare, Bothell, WA) with 15-7 MHz (width = 23 mm) or 18-5 MHz (width = 39 mm) linear transducers or a RS85 (Samsung Medical, Seoul, Korea) with a 4-18 MHz linear transducer (width = 37.3 mm), both for B-mode and power Doppler energy mode. All patients underwent the same US examination protocol including patient position (hand in pronation lying on the examination table) and bilateral examination with both static and dynamic assessment. No standoff pad was used. US images of the dorsal wrists were obtained in the transverse and sagittal planes.

All images and videos of our population were reviewed and assessed retrospectively in consensus by two senior radiologists (AM and SB). In all patients, the ER of the EDC was identified, as described previously [START_REF] Robertson | Extensor retinaculum of the wrist: sonographic characterization and pseudotenosynovitis appearance[END_REF]. Data obtained from US examinations were thickness and echogenicity of the ER and EDC, presence of an effusion and a thickening of the EDC synovial tendon sheath on transverse images, and presence of EDC intratendinous cysts. The largest value for ER and EDC thickness was measured on both the symptomatic and contralateral sides. ER and EDC echogenicity was rated as either hypo-or isoechoic in relation to the contralateral side. Intratendinous cyst size was measured in the longitudinal and transverse planes. Tendon sheath was rated as either normal (no thickening), mildly thickened (synovial sheath thinner than EDC tendons), or markedly thickened (synovial sheath thicker than EDC tendons). Power Doppler images were also reviewed for positive or negative flow within the ER, EDC, and EDC tendon sheath. The presence of local anatomic variants including accessory muscles was noted. Bilateral and comparative dynamic assessment was available on video clip records obtained during active and passive flexion/extension of the wrist and fingers. Tendon impingement was diagnosed on US dynamic examination with correlation with patients' pain. It was rated as positive in case of bulging of tendons on the distal edge of the ER with restriction of tendon sliding in comparison with the normal side and reproduction of the patient pain during the dynamic impingement. Ultrasound examination searched also tenosynovitis of both palmar and other dorsal tendons of the wrists and synovitis of radio-ulnar, radiocarpal, and mediocarpal joints (i.e., effusion, synovial thickening, and power Doppler hyperemia) to exclude potential rheumatologic disease.

Statistics

Quantitative data are reported as mean, median, first and third quartiles, as well as minimum and maximum. Qualitative data were reported by number and percentage. Univariate comparisons use Fisher's exact test for qualitative data and Wilcoxon's rank test for quantitative values.

All statistical tests used give significative values for p < 0.05. A statistical report was performed using opensource R version 3.4.4 (2018-03-15) and LATEX, on a i386-w64-mingw32 platform. Tables and graphics were created using Sweave 1.

Results

The study population characteristics are presented in Table 1. There were 10 males and 8 females with a mean age of 57.4 years; and the age range was 11-94 years. EDCST most often affected the left wrist (n = 11). Dominant hand was recorded in only 6 cases in the database. In six patients (6/18; 33%), repetitive movements were recorded prior to the apparition of the lump: the youngest patient was a gymnast, one patient was a typist, one was a safe installer, one was a pianist, and the two remaining patients were referred after intensive gardening. In 12 patients, no repetitive movement or microtraumatic injury could be identified. No patient had a history of previous local trauma or surgery. No patient was diabetic. A total of 15 patients (15/18; 83%) consulted for a chronic painful swelling of the dorsal aspect of the wrist extending distally to the hand associated with local discomfort (Fig. 1a). Of note, the lumps were partially compressible (Fig. 1b). One patient had an acute onset with a rapid development of the swelling a few days before the US examination. Except for the patient with acute onset, the duration of symptoms was >3 months with a progressive onset. No patient was clinically suspected of EDCST. At the time of US examination, the overlying skin was normal. Mild local tenderness and pain were exacerbated by wrist extension. In contrast, the three remaining patients (3/18; 17%) consulted for a dorsal painful mass that was in continuity with the index extensor tendon and showed proximal and distal migration during extension and flexion of the finger.

US showed changes in both the ER and EDC in all patients. The ER was hypoechoic and thickened in all cases (Fig. 2). The mean thickness of the ER was 2.1 mm versus 1.1 mm for the unaffected contralateral wrist ranging from 1.2 to 2.7 mm versus 0.76 to 1.6 mm (p < 0.0007) (Table 2) (Graph.1).

The EDC was thickened and hypoechoic in all cases with a mean thickness of 5.2 mm versus 3.8 mm for the unaffected side ranging from 3.0 to 7.3 mm versus 2.6 to 5.1 (p < 0.013) (Table 2) (Graph 2). Patients were divided into 2 groups: ER thickness values up to 2 × contralateral ER thickness, and ER values superior to 2 × contralateral ER thickness. The patients with less thick ER were older (mean age 69 vs 58 years old), mainly men (78% vs 50%), and presented relatively thicker EDC (mean diameter 6.2 Vs 4,2 mm). Power Doppler hyperemia of the ER was inconstant and observed in 11 cases (11/ 18; 61.1%) (Fig. 3). A cyst located inside the EDC of the index finger was observed in three cases (3/18; 16,7%). When present, the intratendinous cyst exhibited a fusiform appearance with the largest diameter in the sagittal plane (mean 18.4 mm, range: 13.4-27.0 mm). Tendon sheath effusion was observed in 16 cases (16/18; 88.9%). Tendon sheath synovial thickening was constant (18/18; 100%) and was constantly rated as mild (Fig. 4a). Tendon sheath Doppler hyperemia was observed in 14 cases (14/18; 77.8%) (Fig. 4b).

A dynamic study showed impingement between the EDC and ER in all cases during wrist and finger extension when the enlarged EDC tendon mass impacted on the distal boundary of the thickened ER which limited its excursion (Fig. 5). The impingement reproduced the pain experienced by the patients. In the three patients with an intratendinous cyst, extension of the index finger was associated with the confinement of the cyst under the ER, which was displaced dorsally (Fig. 6). We did not observe any anatomical variant of the fourth dorsal compartment of the wrist. Finally, no other tenosynovitis/ synovitis was depicted.

In four of these patients (4/18; 22%), surgery was able to confirm the US diagnosis. Exploration via a mini-open technique showed thickening of both the ER and EDC. Surgical release of the ER and tenosynovectomy was followed in all patients by complete pain relief at 3 months. Synovial tissue histological analysis revealed fibrosis changes with no/little synovial hyperplasia and inflammatory reaction. In one of these four patients, the extensor tendon had in addition to be repaired (Fig. 7). Among the fourteen patients that did not undergo surgery, two patients were treated with US-guided corticosteroid injection providing complete symptom relief at 3 months. Five patients were treated conservatively and presented mild residual swelling and partial relief of pain at the last follow-up. Unfortunately, seven patients including the three patients with intratendinous cysts were initially treated conservatively and then lost to clinical follow-up.

Discussion

At the dorsal aspect of the wrist, the extensor tendons course in osteofibrous tunnels delimited by bony depressions and the ER, a fibrous band that inserts into the dorsal aspects of the distal radial styloid process and in the palmar side into the flexor carpi ulnaris, triquetrum pisiform, fascia of the abductor digiti quinti muscle, and, deep to it, into the base of the small finger metacarpal [START_REF] Taleisnik | The extensor retinaculum of the wrist[END_REF] (Fig. 8). Proximally, the ER arises from the antebrachial fascia of the forearm and extends distally into the superficial fascia of the dorsum of the hand [START_REF] Taleisnik | The extensor retinaculum of the wrist[END_REF]9]. At the level of the distal epiphysis of the radius, the insertions of the ER give origin to six compartments that house the extensor tendons surrounded by synovial sheaths. The function of the ER is to prevent bowstringing by keeping the extensor tendons close to the bone surface but separate from each other.

The US appearance of the fourth dorsal compartment ER has been described previously [START_REF] Robertson | Extensor retinaculum of the wrist: sonographic characterization and pseudotenosynovitis appearance[END_REF]. It is thicker than the ER of the other dorsal compartments, which may be misinterpreted as Power Doppler ER hyperemia may be helpful in the diagnosis but is not constant. In all cases, the EDC tendons were thickened with a more rounded cross section at the level of ER. In the transverse view, the association of retinaculum hypoechoic thickening and a more rounded tendon is the typical pattern of De Quervain tenosynovitis [START_REF] Marini | De Quervain's disease: diagnostic imaging[END_REF][START_REF] Nagaoka | Ultrasonographic examination of de Quervain's disease[END_REF][START_REF] Trentanni | Ultrasonic diagnosis of De Quervain's stenosing tenosynovitis[END_REF][START_REF] Giovagnorio | Ultrasonographic evaluation of de Quervain disease[END_REF][START_REF] Gitto | Sonography of non-neoplastic disorders of the hand and wrist tendons[END_REF] and trigger finger [START_REF] Bianchi | Ultrasound features of trigger finger: review of the literature[END_REF]. In the same way, this pattern was constant in all our EDCST cases. Our operational definition of impingement was based on three coincident features. Morphologic US criteria (thickening of the ER compared by the asymptomatic side, morphologic changes of the EDC), dynamic US criteria (impingement of the EDC against the ER during simultaneous finger and wrist extension), and reproduction of the patient pain during the dynamic impingement. The synovial hypoechoic thickening observed in all our patients and synovial sheath fluid observed in 88.9% of our patients could be confusing with proliferative extensor tenosynovitis which is a common and well-described condition in patients with rheumatoid arthritis [START_REF] Rubin | MRI and ultrasound of the hands and wrists in rheumatoid arthritis. I Imaging findings[END_REF] that commonly affects the fourth compartment [START_REF] Wilson | Extensor tendon problems in rheumatoid arthritis[END_REF][START_REF] Papp | The rheumatoid wrist[END_REF]. In rheumatic tenosynovitis, the ER remains normal and may even be used for surgical procedure [START_REF] Rabarin | Butterfly flap": the retinaculum to the rescue of the extensors[END_REF]. Therefore, in case of unicompartmental tenosynovitis of the EDC, ER thickness should be assessed, and local impingement of the EDC tendons should be evaluated [20] and by Mahajan [START_REF] Mahajan | Surgical treatment of tenosynovitis of extensor tendons of fourth compartment of wrist in nonrheumatoid patients-a case series of 10 patients in India[END_REF]. They described proliferative extensor tenosynovitis of the wrist in, respectively, 11 and 10 patients. These authors reported the presence of a proliferative synovial mass adherent to the EDC that blocked proximal tendon extrusion, but they did not assess the ER and could not exclude EDCST. In our population, we hypothesize that the synovial thickening is only a part of the spectrum of EDCST and should therefore be considered a consequence of the impingement between the tendon sheath and the ER. According to our data, dynamic sagittal US scanning during flexion/extension of the fingers is a key examination in diagnosing ST because it demonstrates decreased tendon motion and is the only imaging modality to confirm the impingement between the thickened EDC and the ER. Interestingly, we did not find a past history of repetitive movements as a contributing factor for EDCST in 11 out of our 18 patients. Nevertheless, we believe that overuse and chronic microtrauma may lead to localized thickening of the ER as has been described in the De Quervain tenosynovitis or trigger finger. Age may also be a contributing factor as most of our patients were in their fifties. In three cases, patients had an intratendinous cyst. Para-articular ganglion cysts are very common at the wrist [START_REF] Zhang | Sonography of wrist ganglion cysts: which location is most common?[END_REF], but intratendinous cysts are very unusual. One of the three patients with an intratendinous cyst was a gymnast, as reported in one case by Wilson et al. [START_REF] Wilson | Extensor tendon impingement in a gymnast[END_REF], supporting the hypothesis of a microtraumatic origin. Microtrauma of the EDC on the ER may also lead to tendon attrition lesions as observed on the fourth finger extensor tendon of one of our patients during surgery. Like Seidman et al. [START_REF] Seidman | Intratendinous ganglia of the hand[END_REF] and Khazzam et al. [START_REF] Khazzam | Extensor tendon triggering by impingement on the extensor retinaculum: a report of 5 cases[END_REF], we suggest that tenosynovitis may invade a damaged tendon, as encountered in the EDC index tendon in our three patients. It is difficult to determine which phenomenon occurred first, ER thickening and stenosis or occurrence of the intratendinous cyst, given that cases of intratendinous cysts have been reported without impingement [START_REF] Seidman | Intratendinous ganglia of the hand[END_REF]. Nevertheless in our three cases, cysts developed in hypoechoic and thickened EDC tendons with dynamic conflict, which can logically be related to repetitive microtrauma and synovial intratendinous invasion. Our work presents several limitations. First, because this entity is quite rare, the study was retrospective in nature. We have not included patients with tenosynovitis of other etiology and so cannot affirm that the described three coincident features are pathognomonic of EDCST. Nevertheless, in our practice, we never noted such simultaneous features in other types of tenosynovitis, and we are not aware of studies on this subject. Second, we did not investigate intra-or inter-observer variability in EDR and EDC measurements, and did not compare our measurements with a control group. Third, a surgical correlation was only available in four cases. Nevertheless, surgical findings confirmed the US data in all patients. Finally, clinical follow-up was variable in our population with ten patients only presenting at least 1-year follow-up in our Institutions.

Conclusion

Stenosing tenosynovitis is a rare finding at the 4th dorsal compartment. US typical features associate in our patients a mild proliferative thickening of EDC tendon sheath with fluid, hypoechoic thickening of the EDC tendons with a round pattern in transverse view, a hypoechoic thickening of the ER, and most importantly a dynamic impingement between the tendon and the ER. Further studies on EDC tenosynovitis without impingement seem required to judge if the described features are specific to EDCST.

Fig. 1 a

 1 Fig. 1 a, b Clinical appearance of EDCST in a 65-year-old female patient show a soft swelling (arrows) on the dorsal aspect of the right wrist

Fig. 2 1 :Graph 1 2 Fig. 3

 21123 Fig. 2 Ultrasound appearance of EDCST in the same patient as Fig. 1: Left (right wrist): transverse image showing a hypoechoic thickening (small double curved arrow) of the ER (arrowheads) and thickening and round shape of EDC (double arrow). Right: image obtained at the same level for the contralateral normal wrist. (R, radius)

Fig. 4

 4 Fig. 4 Power Doppler ultrasound appearance of EDCST in a 59-year-old male patient. a Transverse grayscale and b power Doppler ultrasounds obtained distal to the thickened ER. In a, note the normal hyperechoic tendons surrounded by an effusion (arrows) and hypoechoic thickening of the synovial sheath (asterisks). b Power Doppler shows hyperemia of the sheath

Fig. 6 Fig. 5 4 .Fig. 7

 6547 Fig. 6 Ultrasound Dynamic examination of EDCST with intratendinous cyst in an 11-year-old gymnast. Sagittal ultrasound image obtained at rest (a) and with active finger extension (b). a Intratendinous ganglion cyst within the index EDC (white arrow) surrounded by hypoechoic thickening of the tendon (black arrow) and focal compression of the ER (black arrowheads). b Proximal displacement of the tendon and ganglion cyst (white dotted arrow) with the confinement of the ganglion cyst under the ER and bulging of the EDC. (M3, third metacarpal bone; Cap, capitatum)

Table 1

 1 Characteristics of the study population (N = 18)

	Characteristic
	Age (years)
	Mean	57.4
	Median (range: min-max)	61.4 (11-94)
	Gender
	Male	10
	Female	8
	Hand affected
	Right	7
	Left

Table 2

 2 Ultrasound findings

	Pathological side	Unaffected side

Declarations

Conflict of interest The authors declare no competing interests.

Informed consent Written informed consent was obtained from all subjects (patients) in this study.

Ethical approval Institutional Review Board approval was obtained.

No study subjects or cohorts have been previously reported. Methodology: retrospective.


Mathieu Carissimi

Pierre Sautet

Dimitri Charre

Lukas Hanak

Matthieu Ollivier

Grégoire Micicoi
email: greg_micicoi@yahoo.fr

Patellar height is not modified after isolated open-wedge high tibial osteotomy without change in posterior tibial slope

Keywords: Patellar height, Open-wedge high tibial osteotomy, Posterior tibial slope, Deformity, Knee

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

Introduction

Open-wedge high tibial osteotomy (OWHTO) is a well-established procedure correcting lower-limb deformities, notably in cases of medial compartment osteoarthritis with varus deformity [START_REF] Hernigou | Proximal tibial osteotomy for osteoarthritis with varus deformity. A ten to thirteen-year follow-up study[END_REF][START_REF] Amendola | Results of high tibial osteotomy: review of the literature[END_REF][START_REF] Goshima | Age does not affect the clinical and radiological outcomes after open-wedge high tibial osteotomy[END_REF][START_REF] Siboni | Ostéotomie tibiale de valgisation par ouverture médiale dans les grandes corrections supérieures à 10 degrés, sans greffe osseuse. À propos de 27 cas[END_REF]. The aim is to relieve load on the affected compartment, transferring forces to the healthy side by changing coronal alignment [START_REF] Kim | Change of Chondral Lesions and Predictive Factors After Medial Open-Wedge High Tibial Osteotomy With a Locked Plate System[END_REF][START_REF] Kumagai | Factors affecting cartilage repair after medial opening-wedge high tibial osteotomy[END_REF][START_REF] Jung | Second-look arthroscopic assessment of cartilage regeneration after medial opening-wedge high tibial osteotomy[END_REF]. However, changes may also be induced in the sagittal plane affecting posterior tibial slope and patellar height. Thus, many authors reported increased posterior tibial slope and decreased patellar height after proximal tibial osteotomy [START_REF] Hanada | Comparison of the change in patellar height between opening and closed wedge high tibial osteotomy: measurement with a new method[END_REF][START_REF] El-Azab | Patellar height and posterior tibial slope after open-and closed-wedge high tibial osteotomy: a radiological study on 100 patients[END_REF][START_REF] Brouwer | Patellar height and the inclination of the tibial plateau after high tibial osteotomy[END_REF][START_REF] Cullu | Does patellar ligament length change after dome-type high tibial osteotomy?[END_REF], leading some surgeons to modify their operative technique [START_REF] Krause | Patella height is not altered by descending medial open-wedge high tibial osteotomy (HTO) compared to ascending HTO[END_REF][START_REF] Akiyama | Distal Tibial Tuberosity Arc Osteotomy in Open-Wedge Proximal Tibial Osteotomy to Prevent Patella Infra[END_REF][START_REF] Amzallag | Patellar height modification after high tibial osteotomy by either medial opening-wedge or lateral closingwedge osteotomies[END_REF][START_REF] Luceri | Effects of sagittal tibial osteotomy on frontal alignment of the knee and patellar height[END_REF].

These surgical variants remain controversial, as most patellar height measurement indices are based on a tibial landmark that is inevitably altered by proximal tibial osteotomy.

In 1997, Miura et al. [START_REF] Miura | Is patellar height really lower after high tibial osteotomy?[END_REF] analyzed the inaccuracy of indices based on an anterior tibial landmark, favoring those based rather on a femoral reference.

Ihle et al. [START_REF] Ihle | No change in patellar height following open wedge high tibial osteotomy using a novel femur-referenced measurement method[END_REF] recently described a patellar height measurement index based on a femoral reference, using the base of the patella, the femoral epicondyles and the joint surface of the femoral condyles as landmarks. Patellar height was unchanged by osteotomy according to this index, which, however, has yet to be validated in another clinical series.

The aim of the present study was to analyze change in patellar height after posteromedial OWHTO, based on tibial and femoral reference indices.

The study hypothesis was that patellar height is unchanged after isolated posteromedial OWHTO performed without changing tibial slope, using a patient-specific cutting-guide. The procedure consisted in an isolated posteromedial OWHTO with unchanged tibial slop and osteotomy site filled by bone allograft; fixation used a Newclip Activ-Motion plate.

Material and method

Postoperative rehabilitation was identical in all cases [START_REF] Chaouche | Patient-specific cutting guides for open-wedge high tibial osteotomy: safety and accuracy analysis of a hundred patients continuous cohort[END_REF]. Holes were drilled in the proximal part of the tibia through the patient-specific cutting-guide. The cut was followed by progressive opening of the osteotomy site, according to the intended correction in the coronal plane. The guide reliably reproduces the preoperative plan, with a margin of error of 0.2° in the coronal plane and 0.1° in the sagittal plane [START_REF] Donnez | Are three-dimensional patient-specific cutting guides for open wedge high tibial osteotomy accurate? An in vitro study[END_REF]. X-rays were taken for the preoperative work-up and for the usual follow-up.

Exclusion criteria comprised: post-traumatic osteoarthritis, severe congenital or acquired bone abnormalities such as Blount's disease, >10° preoperative flexion contracture, and previous surgery.

X-rays were analyzed for 129 patients, comprising weight-bearing knee views (AP in complete extension; lateral in 30° flexion) and long-leg view, preoperatively and at 12months.

Radiographic measurements

Pre-and post-operative radiographic measurements were taken twice, at a 2-month interval by 2 independent observers.

The usual angles were measured, following Paley et al. [START_REF] Paley | Normal Lower Limb Alignment and Joint Orientation[END_REF]: hip-knee-ankle (HKA) angle, lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), joint line convergence angle (JLCA) and joint line obliquity (JLO) (figure 1). Posterior tibial slope (PTS) was defined according to Amendola et al. [START_REF] Westermann | Minimizing alteration of posterior tibial slope during opening wedge high tibial osteotomy: a protocol with experimental validation in paired cadaveric knees[END_REF][START_REF] Amendola | Total knee arthroplasty following high tibial osteotomy for osteoarthritis[END_REF] as the angle between the anatomic tibial axis and the tangent to the medial tibial plateau in the sagittal plane (figure 2).

Patellar height was measured sagittally on Caton-Deschamps (CD) [START_REF] Caton | Patella infera. A propos de 128 cas[END_REF] and Insall-Salvati (IS) [START_REF] Insall | Patella Position in the Normal Knee Joint[END_REF] indices with proximal tibial reference (figure 3), and coronally on Schröter index with distal femoral reference [START_REF] Ihle | No change in patellar height following open wedge high tibial osteotomy using a novel femur-referenced measurement method[END_REF] (figure 4).

Schröter index

Change in tibial slope drastically affects the CD index without altering relations between joint line and real patellar height in the trochlea.

Consequently, a new method, referenced on the femur, was proposed in 2017 by Ihle et al.

[17]: Schröter's Femoral Patella Height Index (FPHI). It is measured on weight-bearing AP view in full extension. The landmarks consist of the base of the patella, the femoral epicondyles and the femoral condyle joint surface. It is calculated by dividing distance A between 2 vertical tangents to the femoral epicondyles, by distance B between the horizontal lines from the base of the patella to the tangent of the femoral condyle joint surfaces (Figure 4).

This index was validated in a scientific paper [START_REF] Ihle | No change in patellar height following open wedge high tibial osteotomy using a novel femur-referenced measurement method[END_REF] but to or knowledge has not since been used in a larger series.

Validation process

Radiographic measurements, both pre-and post-operatively (first at 12 months), were taken twice by 2 independent observers at a 2-month interval for intra-observer reproducibility assessment.

To determine pre-to post-operative change, test-retest reliability was assessed; intra-and inter-observer reproducibility was described by intraclass correlation coefficient (ICC) with 95% confidence interval.

Analyses used JMP software. Normal distribution was checked on Kolmogorov-Smirnov test.

Pre-to post-operative change was assessed on parametric or non-parametric tests according to distribution normality.

Post-hoc analysis based on mean patellar-height endpoint values with standard deviation checked that the sample size allowed differences of 0.04, 0.03 and 0.04 on CD, IS and Schröter indices to emerge as significant. The clinical significance thresholds for changes in these indices have not been reported.

All analyses respected legal and regulatory requirements with regard to review board approval and informed consent.

Results

Table 1 shows intra-and inter-observer reproducibility, which was high, with ICC between 0.79 and 0.91.

Osteotomy significantly impacted HKA angle (Δ = 6.3 ± 0.95°, p < 0.0001) and MPTA (Δ = 7 ± 0.88°, p < 0.0001). Values for mechanical LDFA (mLDFA), PTS, and JLO were unchanged (Table 2).

Tibial and femoral referenced patellar height indices were unchanged (Table 3).

Multivariate analysis found no association between change in HKA angle (p = 0.

Discussion

The present results showed no change in patellar height after isolated posteromedial OWHTO without change in tibial slope, using patient-specific cut-guides.

For the CD index, referenced on the proximal tibia, patellar height was shown to correlate with degree of coronal correction and PTS correction after medial OWHTO [START_REF] Amzallag | Patellar height modification after high tibial osteotomy by either medial opening-wedge or lateral closingwedge osteotomies[END_REF].

Greater changes in tibial slope may occur with OWHTO [START_REF] Marti | Accuracy of frontal and sagittal plane correction in open-wedge high tibial osteotomy[END_REF][START_REF] Nha | Change in Posterior Tibial Slope After Open-Wedge and Closed-Wedge High Tibial Osteotomy: A Meta-analysis[END_REF]. In the present study, changes in the sagittal plane (0.36°) were not significant, which may explain why the CD index was unchanged. The IS index is independent of posterior tibial slope, but may be altered by patellar tendon shortening caused by the postoperative scar and/or by peritendinous tissue retraction [START_REF] Cullu | Does patellar ligament length change after dome-type high tibial osteotomy?[END_REF][START_REF] Okamoto | Shortening of patellar ligament and patella baja with improvement of quadriceps muscle strength after high tibial osteotomy[END_REF]; this index is unchanged by OWHTO.

Schröter index [START_REF] Ihle | No change in patellar height following open wedge high tibial osteotomy using a novel femur-referenced measurement method[END_REF] is unaffected by proximal tibial osteotomy, and enables reproducible follow-up of patellar height after OWHTO.

Many authors advocated for more distal osteotomy below the tibial tuberosity to reduce risk of patella infera [START_REF] Akiyama | Distal Tibial Tuberosity Arc Osteotomy in Open-Wedge Proximal Tibial Osteotomy to Prevent Patella Infra[END_REF][START_REF] Hopwood | The biplanar open wedge high tibial osteotomy preserving the tibial tubercle[END_REF][START_REF] Gaasbeek | Distal tuberosity osteotomy in open wedge high tibial osteotomy can prevent patella infera: a new technique[END_REF]. Double-level osteotomy does not seem to prevent patellar descent [START_REF] Akaoka | Changes in patellar height and patellofemoral alignment following double level osteotomy performed for osteoarthritic knees with severe varus deformity[END_REF] but does reduce the rate of non-anatomic correction [START_REF] Micicoi | Osteotomy around the knee is planned toward an anatomical bone correction in less than half of patients[END_REF][START_REF] Micicoi | Comments on: "Is patientspecific instrumentation more precise than conventional techniques and navigation in achieving planned correction in high tibial osteotomy?[END_REF]. According to Otsuki et al. [START_REF] Otsuki | Hybrid high tibial osteotomy is superior to medial opening high tibial osteotomy for the treatment of varus knee with patellofemoral osteoarthritis[END_REF], hybrid tibial osteotomy can be performed in case of pre-existing patellofemoral osteoarthritis, associating 33% medial opening to 67% lateral closure to reduce the tibial tuberosity-trochlear groove (TT-TG) distance without lowering the patella.

Patella infera can lead to patellofemoral incongruence and osteoarthritis [START_REF] Goutallier | The patello-femoral joint in osteoarthritis of the knee with genu varum[END_REF], as can difficulties encountered in total knee replacement for preoperative patella infera [START_REF] Windsor | Technical considerations of total knee arthroplasty after proximal tibial osteotomy[END_REF].

Patellofemoral joint problems after OWHTO may be due to anterior translation of the proximal tibial fragment [START_REF] Tseng | The correlation of sagittal osteotomy inclination and the anteroposterior translation in medial open-wedge high tibial osteotomy-one of the causes affecting the patellofemoral joint?[END_REF] or to medial patellar tilt increasing lateral patellofemoral pressure [START_REF] Gaasbeek | The influence of open and closed high tibial osteotomy on dynamic patellar tracking: a biomechanical study[END_REF]. In contrast, a recent study with a mean 3 years' follow-up found no deterioration in patellofemoral cartilage associated with decreased patellar height [START_REF] Kim | The patellofemoral joint does not deteriorate clinically after open-wedge high tibial osteotomy[END_REF].

The issue of post-osteotomy patellar height was raised by Miura et al. in 1997 [16];

the definition of patella alta or infera mainly depended on the index chosen to assess patellar height. The present values support the results of Ihle et al., who proposed normal values between 1.5 and 1.6, without change after OWHTO; however, these thresholds are to be taken with caution before drawing any therapeutic conclusions ahead of osteotomy, and individual patellofemoral symptoms should be given prime consideration.

The femoral-referenced Bernageau index [START_REF] Bernageau | New exploration technic of the patellofemoral joint. Relaxed axial quadriceps and contracted quadriceps[END_REF] cannot be used if X-rays are poor-quality, and reproducibility seems to be poorer than for FPHI, which is measured on standardized views and can easily be calculated from long-leg weight-bearing X-rays and showed reliable reproducibility over time.

The present study had several limitations. Follow-up was too short to be able to estimate possible correction loss in the sagittal plane, notably due to change in patellar height, but the aim was to validate the FPHI rather than to assess changes over time. Secondly, the retrospective design did not include CT analysis, and subclinical preoperative extension deficit and rotational disorder may have induced error in angle measurements in the coronal plane [START_REF] Babazadeh | The long leg radiograph is a reliable method of assessing alignment when compared to computerassisted navigation and computer tomography[END_REF][START_REF] Jud | Rotation or flexion alters mechanical leg axis measurements comparably in patients with different coronal alignment[END_REF].

Conclusion

The present clinical series showed that patellar height was unchanged by isolated posteromedial OWHTO without change in tibial slope, using patient-specific cutting-guides, with whichever femoral or tibial reference index. The Schröter femoral patella height index was highly reliable and is independent of proximal tibial changes in assessing patellar height, and can thus be recommended for following up OWHTO. J o u r n

J o u r

  Patellar height is not modified after isolated open-wedge high tibial osteotomy without change in posterior tibial slope. Mathieu Carissimi, Pierre Sautet, Dimitri Charre, Lukas Hanak, Matthieu Ollivier, Grégoire Micicoi To cite this version: Mathieu Carissimi, Pierre Sautet, Dimitri Charre, Lukas Hanak, Matthieu Ollivier, et al.. Patellar height is not modified after isolated open-wedge high tibial osteotomy without change in posterior tibial slope.. Orthopaedics & Traumatology: Surgery & Research, 2021, 107 (7), pp.103032. 10.1016/j.otsr.2021.103032. hal-03553768

  5) or MPTA (p = 0.4) and change in patellar height. No demographic or preoperative angle or patellar height values showed significant correlation with changes in patellar height indices.

Figure 1

 1 Figure 1 Long-leg weight-bearing view with angular values in coronal plane

Figure 2

 2 Figure 2 Tibial slope according to Amendola

Figure 3 Figure 4

 34 Figure 3 Patellar height measurement

Table 1 . Reproducibility analysis of radiographic measurement of patellar height.

 1

	Criterion	Inter-observer ICC	Intra-observer ICC
	CD index	0.81, 95%CI (0.75-0.87)	0.9, 95%CI (0.87-092)
	IS index	0.79, 95%CI (0.77-0.81)	0.86, 95%CI (0.81-0.91)
	Schröter index	0.84, 95%CI (0.79-0.89)	0.91, 95%CI (0.85-0.97)
	CD, Caton-Deschamps index; IS, Insall-Salvati index; CI, confidence interval; ICC, intraclass
	correlation coefficient

Table 2 .

 2 Pre-and post-operative anatomic parameters and correction

	Parameters	Preoperative	Postoperative	Δ	p
	HKA°	173.4±2.8	179.7±2.4	6.3±0.95	< 0.0001
	MPTA°	83.4±0.7	90.4±0.7	7±0.88	< 0.0001
	mLDFA°	89.2±1.4	89.39±1.5	0.2±0.5	0.7
	JLCA°	1.55±0.15	1.2±0.16	-0.3±0.1	0.12
	JLO°	3±0.29	2.9±0.3	0.09±0.42	0.9
	PTS°	79.9±0.7	79.5±0.7	0.36±1	0.7
	Mean values ± standard deviation. Δ: pre-to post-operative difference. Significance
	threshold: p < 0.05

Table 3 .

 3 Change in patellar height 12 months after posteromedial open wedge high tibial

	osteotomy
	Parameters	Preoperative	Postoperative	Δ	p
	CD index	1.01±0.1	0.94±0.08	-0.06 ±0.003	0.058
	IS index	1.05±0.02	1.03±0.02	-0.02±0.02	0.36
	Schröter index	1.57±0.026	1.54±0.03	-0.03±0.04	0.4
	CD index, Caton-Deschamps index; IS index, Insall-Salvati index; mean values ± standard
	deviation; Δ: pre-to post-operative difference. Significance threshold: p < 0.05

Ethical considerations: As a category-3, non-interventional study under the terms of the French "Jardé" law of 2020, data protection authorization was not required. Data analysis was retrospective and anonymized. Data collection used an encrypted spreadsheet and was conducted as part of current care. Informed consent: not required Conflits of interest: MC, PS, DC, LH and GM have no conflicts of interest to disclose. MO is a consultant for Newclip Technics. Funding: None. Author contributions: MO: study design; statistics. DC and LH: data collection. MC and PS: draft writing and subsequent re-editing. GM and MO: article writing and re-editing. All authors approved the final version.


Damien Lami

Nicolas Fauvet
email: nico.fauvet@gmail.com

Matthieu Ollivier

Jean-Noël Argenson

Jean- Charles Grillo

A HYBRID OPEN-ARTHROSCOPIC LATARJET CORACOID BONE-BLOCK TECHNIQUE USING "HyLa" INSTRUMENTATION

Keywords: Latarjet, arthroscopic Latarjet, shoulder instability, glenohumeral instability, Bankart repair, Hill-Sachs remplissage, HyLa

Latarjet coracoid bone-block is a gold-standard procedure for anteroinferior instability of the shoulder. Nowadays, it can be performed as open surgery or entirely under arthroscopy. The pure arthroscopic technique has the advantage of allowing concomitant intra-articular surgery, but involves a long learning curve. Here we present a hybrid concept using dedicated instrumentation comprising a specific guide with or without arthroscopic step, and notably ensuring the safety and reproducibility of the procedure, whatever the modality. This technique offers an alternative to arthroscopic coracoid bone block, performing the more complex steps as open surgery without major change to Latarjet's original technique, so as to enable concomitant intra-articular surgery if needed while getting around some of the limitations of the purely arthroscopic procedure.

INTRODUCTION

Latarjet coracoid bone-block is a gold-standard procedure for anteroinferior instability of the shoulder [START_REF] Walch | Latarjet-Bristow Procedure for Recurrent Anterior Instability[END_REF][START_REF] Latarjet | Treatment of recurrent dislocation of the shoulder[END_REF][START_REF] Young | Open Latarjet procedure for management of bone loss in anterior instability of the glenohumeral joint[END_REF][START_REF] Plancher | Open Latarjet: A Reliable, Successful Method to Prevent Recurrence in the Presence of Bony Defects[END_REF][START_REF] Balg | The instability severity index score. A simple pre-operative score to select patients for arthroscopic or open shoulder stabilisation[END_REF]. The literature reports long follow-up, with satisfactory long-term clinical results and better control of recurrence than with other shoulder stabilization techniques [START_REF] Zimmermann | Long-Term Restoration of Anterior Shoulder Stability: A Retrospective Analysis of Arthroscopic Bankart Repair Versus Open Latarjet Procedure[END_REF][START_REF] Hurley | Long-term outcomes of the Latarjet procedure for anterior shoulder instability: a systematic review of studies at 10-year follow-up[END_REF][START_REF] Chillemi | Latarjet procedure for anterior shoulder instability: a 24-year follow-up study[END_REF]. Technically, the procedure is demanding, requiring perfect exposure to guarantee perfect coracoid graft positioning and reduce the risk of complications [START_REF] Griesser | Complications and re-operations after Bristow-Latarjet shoulder stabilization: a systematic review[END_REF][START_REF] Gupta | Complications of the Latarjet procedure[END_REF] such as neurovascular lesions, especially in the axillary and musculocutaneous nerves [START_REF] Shah | Short-Term Complications of the Latarjet Procedure[END_REF]. A cut guide seems to improve precision and reproducibility [START_REF] Barth | Can a Drill Guide Improve the Coracoid Graft Placement During the Latarjet Procedure: A Prospective Comparative Study With the Freehand Technique[END_REF][START_REF] Meyer | Accurate coracoid graft placement through use of a drill guide for the Latarjet procedure[END_REF].

Recent years have witnessed the advent of entirely arthroscopic coracoid bone-block techniques [START_REF] Lafosse | Arthroscopic Latarjet procedure[END_REF][START_REF] Lafosse | The arthroscopic Latarjet procedure for the treatment of anterior shoulder instability[END_REF][START_REF] Boileau | Arthroscopic Bankart-Bristow-Latarjet procedure: the development and early results of a safe and reproducible technique[END_REF] and new methods of graft fixation [START_REF] Boileau | A guided surgical approach and novel fixation method for arthroscopic Latarjet[END_REF]. Their technical demands increase the learning curve and the risk of complications [START_REF] Kordasiewicz | Arthroscopic Latarjet Stabilization: Analysis of the Learning Curve in the First 90 Primary Cases: Early Clinical Results and Computed Tomography Evaluation[END_REF][START_REF] Leuzinger | Learning Curves in the Arthroscopic Latarjet Procedure: A Multicenter Analysis of the First 25 Cases of 5 International Surgeons[END_REF][START_REF] Valsamis | The arthroscopic Latarjet: a multisurgeon learning curve analysis[END_REF]: good mastery requires 20-50 procedures, even for well-experienced surgeons.

Macroeconomic studies [START_REF] Randelli | Open Latarjet versus arthroscopic Latarjet: clinical results and cost analysis[END_REF] also suggest considerable extra cost in equipment and personnel for these purely arthroscopic techniques.

Moreover, no added value has been demonstrated unless concomitant intra-articular surgery is planned [START_REF] Horner | Open versus arthroscopic Latarjet procedures for the treatment of shoulder instability: a systematic review of comparative studies[END_REF][START_REF] Kordasiewicz | Comparative study of open and arthroscopic coracoid transfer for shoulder anterior instability (Latarjet)clinical results at short term follow-up[END_REF].

Nevertheless, the possibility of associating arthroscopy to coracoid bone-block is interesting. In some cases, concomitant procedures such as Hills-Sachs lesion remplissage [START_REF] Saliken | Combined All-arthroscopic Hill-Sachs Remplissage, Latarjet, and Bankart Repair in Patients With Bipolar Glenohumeral Bone Loss[END_REF], Bankart repair [START_REF] Boileau | Arthroscopic Bristow-Latarjet Combined With Bankart Repair Restores Shoulder Stability in Patients With Glenoid Bone Loss[END_REF] or cuff repair [START_REF] Jouve | Recurrent anterior instability of the shoulder associated with full thickness rotator cuff tear: results of surgical treatment[END_REF] can be of benefit.

CONCEPT and MATERIAL

All the above considerations encouraged us to develop a hybrid concept with a dedicated cut guide, offering the choice between associating arthroscopy or not.

We sought to simplify the all-arthroscopic technique, with the following objectives:

to circumvent the steps that are technically demanding under arthroscopy [START_REF] Metais | Preliminary clinical outcomes of Latarjet-Patte coracoid transfer by arthroscopy vs. open surgery: Prospective multicentre study of 390 cases[END_REF]: to avoid the extra cost of systematic arthroscopy when it is not necessary.

The HyLa hybrid Latarjet (Newclip) was developed in an anatomy laboratory. It is sterilizable and reusable.

It comprises a dedicated guide (Figure 1) for stable solidity of the pediculated coracoid graft, manipulating it through the subscapularis incision. This can be used in open surgery or in the hybrid procedure, with the aim of:

ensuring safety by protecting neurovascular structures against the rotating tools; -enhancing inter-operator reproducibility by ensuring screw parallelism for optimal graft compression; -controlling graft positioning by avoiding protrusion thanks to an adjustable intraarticular grip (Figure 1).

The "3-in-1" tools (Figure 1) are hand devices for guiding pins, fixing the bone-block to the guide, and unicortical graft tapping to prepare the screwhead imprints. They come in various lengths, to avoid impingement.

The bone-block is stabilized with two 3.5 mm cannulated Herbert self-compression screws, biomechanically validated [START_REF] Massin | Comparative biomechanical study of five systems for fixation of the coracoid transfer during the Latarjet procedure for treatment of anterior recurrent shoulder instability[END_REF] with predefined pitch of 9.5mm.

The present technical note describes an original Latarjet coracoid bone-block concept with a dedicated guide that can be used in standard open surgery or in a hybrid technique including an arthroscopy step. The technical details are codified and specified below.

SURGICAL TECHNIQUE 1) Core steps: graft preparation and bone-block fixation on guide

The patient is positioned semi-seated; surgery is performed under general anesthesia with interscalene nerve block.

A deltopectoral approach is performed, and the coracoid graft is harvested and freshened on the inferior side. Width is measured by the ruler included in the instrumentation kit (Figure 2) and transposed to the intra-articular grip to ensure screw centering (Figure 3). The graft is then laid aside under the pectoralis major. At this point, an open subscapularis incision is made, whatever the intended procedure.

Depending on the option, the graft is fixed on the guide at different points in time, but following the same order of steps. The 3-in-1 tools are centered by the clip-on guide grip (Figure 4), then the guide is fixed on the bone-block with the following steps: pins introduced through the bone-block; unicortical drilling of the bone-block (Figure 5); then insertion of the tapping part of the 3-in-1 tools into the bone-block (Figure 5). The clip-on guide grip is then removed.

2) Option 1: open positioning of the bone-block

In this option, after subscapularis incision, glenohumeral joint capsule arthrotomy is performed and the anteroinferior side of the cavity is freshened. The bone-block is then fixed onto the HyLa guide, and the two are fitted against the glenoid; the intra-articular grip helps in positioning the graft subequatorially without lateral protrusion (Figure 6). It can be withdrawn if it hinders the procedure, especially if a Fukuda intra-articular retractor is used. Positioning is then at the surgeon's discretion: the graft can be manipulated easily using the guide.

The graft is fixed temporarily with 2 bicortical K-wires, measured on the ruler (Figure 7).

After unicortical glenoid drilling, the screws (Figure 8) are introduced using a stop-check screwdriver to avoid excessive screwhead penetration in the bone-block; K-wires and guide are then withdrawn (Figure 9).

3) Option 2: arthroscopic positioning of the bone-block (movie 1)

In this option, subscapularis incision but not arthrotomy is an open procedure (Figure 10). The bone-block is fixed on the HyLa guide and the two are set aside under the subscapularis split, up against the joint capsule.

Posterior arthroscopy (Figure 11) then begins with joint assessment. Arthrotomy is performed by capsule-labrum release by monopolar probe until the deep subscapularis fibers are exposed. The anteroinferior side of the glenoid is freshened by shaver. An optional anterolateral portal can be performed for instruments or to visualize anterior glenoid freshening (Figure 11).

The guide+graft is then picked up though the subscapularis incision, and the bone-block is positioned and fixed to the glenoid as described for open surgery, but under arthroscopic control. Associated intra-articular procedures are executed at different steps, depending on their type:

-For remplissage of Hills-Sachs lesion by infraspinatus capsule-tenodesis, anchor positioning and suture passing is performed after capsule-labrum release and before positioning the bone-block, while tendon suturing is performed after boneblock fixation.

-For capsule-labrum reinsertion, anchor positioning and suture passing is performed after bone-block fixation.

-For rotator cuff repair, preparation is performed before capsule-labrum release, to optimize intra-articular pressure. As repair is mostly within the subacromial space, the question of pressure is relative, based mainly on intraoperative control of bleeding and blood pressure.

Crossover from arthroscopy to open surgery with or without guide is possible at any point.

CONCLUSION

The present concept aims primarily to simplify the all-arthroscopic Latarjet coracoid bone-block technique while still allowing associated arthroscopic procedures, and to ensure safety and inter-operator reproducibility without significant change in technique with respect to the classical Latarjet procedure.

To validate these objectives, further studies are underway in a cohort operated on using the HyLa instrumentation, with CT assessment of graft positioning and analysis of the learning curve and inter-operator reproducibility.

FIGURES

  coracoid harvesting and preparation, and subscapularis incision; these are performed as open surgery; -to keep an open option of crossover, respecting the full charge-book of the goldstandard open Latarjet procedure;

Figure 1 :

 1 Figure 1: Diagram of HyLa guide for coracoid bone-block positioning. a: Cut guide

Figure 2 :

 2 Figure 2: Diagram and intraoperative view of bone-block width measurement by the 2-

Figure 3 :

 3 Figure 3: Diagram and intraoperative view of transposing graft width to the adjustable

Figure 4 :

 4 Figure 4: Diagram and intraoperative view of positioning the clipped support grip to

Figure 5 :

 5 Figure 5: Diagram and intraoperative view of attachment of guide and graft by 3-10-1

Figure 6 :

 6 Figure 6: Diagram and intraoperative view of guide+graft positioning against glenoid.

Figure 7 :

 7 Figure 7: Intraoperative view of screw sizing with ruler.

Figure 8 :

 8 Figure 8: Diagram of assembly with guide still in place.

Figure 9 :

 9 Figure 9: Final result: diagram, intraoperative view, radiographic view.

Figure 10 :

 10 Figure 10: Intraoperative view of subscapularis split with intact joint capsule.

Figure 11 :Movie 1 :

 111 Figure 11: Intraoperative view of arthroscopic portals.

ACKNOWLEDGMENTS

Newclip Montpellier-Nîmes university anatomy laboratory DISCLOSURE OF INTEREST Nicolas Fauvet -no conflicts of interest Damien Lami -Newclip (HyLa instrumentation designer) Matthieu Ollivierno conflicts of interest Jean-Noël Argenson -Symbios (royalties) / Zimmer (royalties -consultant) / EKA (president) / SOFCOT (permanent board member) / JBJS (board member) Jean-Charles Grillo -Newclip (HyLa instrumentation designer) Funding: none

Author contributions:

Damien Lami: study design,