J Garret
email: j.garret@cliniqueduparclyon.com

G Nourissat
email: gnourissat@wanadoo.fr

M B Hardy

D Antonucci
email: antonucci.diego01@gmail.com

P Clavert

P Mansat
email: mansat.p@chu-toulouse.fr

A Godenèche
email: arnaud.godeneche@wanadoo.fr

Painful posterior shoulder instability: Anticipating and preventing failure. A study in 25 patients

Keywords:

Background: Painful posterior shoulder instability (PPSI) is the least common of the three clinical patterns of posterior shoulder instability. PPSI is defined as pain combined with anatomical evidence of posterior instability but no instability events. Material and method: We studied a multicentre cohort of 25 patients with PPSI; 23 were identified retrospectively and had a follow-up of at least 2 years and 2 patients were included prospectively. Most patients engaged in sports. Results: All 25 patients underwent surgery, which usually consisted in arthroscopic capsulo-labral reconstruction. The outcome was excellent in 43% of patients; another 43% had improvements but reported persistent pain. The pain remained unchanged or worsened in the remaining 14% of patients. Causes of failure consisted of a missed diagnosis of shoulder osteoarthritis with posterior subluxation, technical errors, and postoperative complications. The main cause of incomplete improvement with persistent pain was presence of cartilage damage. Conclusion: Outcomes were excellent in patients who were free of cartilage damage, bony abnormalities associated with posterior instability (reverse Hill-Sachs lesion, erosion or fracture of the posterior glenoid), technical errors, and postoperative complications.

Introduction

Posterior shoulder instability (PSI) is a rare condition that accounts for only 2% to 10% of all cases of shoulder instability [START_REF] Antosh | Posterior shoulder instability: current surgical management[END_REF][START_REF] Wooten | Athroscopic capsulolabral reconstruction for posterior shoulder instability in patients 18 years old or younger[END_REF][START_REF] Owens | Risk factors for posterior shoulder instability in young athletes[END_REF][START_REF] Tannenbaum | Evaluation and management of posterior shoulder instability[END_REF][START_REF] Bottoni | Operative stabilization of posterior shoulder instability[END_REF]. PSI differs from anterior shoulder instability regarding the clinical manifestations, diagnosis, and treatment. * Corresponding author.

Clinically, PSI presents as three different entities [START_REF] Boileau | The unstable painful shoulder (UPS) as cause of pain from unrecognized anteroinferior instability in the young athlete[END_REF]: recurrent involuntary posterior dislocation and/or subluxation; voluntary PSI, which may progress to involuntary PSI; and painful PSI (PPSI), in which pain is the only symptom. Three main treatment approaches can be distinguished: non-operative treatment, surgical stabilisation by capsulo-labral reconstruction, and surgical stabilisation via a bone block procedure.

This multicentre study reports outcomes in patients with painful PPSI, i.e., with no history of dislocation or subluxation. The patients were included retrospectively or prospectively. The study objectives were to assess the features of PPSI and the effectiveness of the treatments used and to devise means of anticipating and preventing treatment failures. The working hypothesis was that treatment outcomes were more variable in PPSI than in other patterns of PSI.

Material and methods

Patients

Two multicentre studies, one retrospective and the other prospective, were approved by the appropriate ethics committee. Of 203 patients treated for PPSI, 151 were included retrospectively; all these patients were treated surgically and re-evaluated at least 2 years after surgery. The remaining 52 patients were treated non-operatively or surgically. The patients were recruited by 17 surgeons in 11 centres in France.

The patients were divided into three clinical subgroups: involuntary dislocation and/or subluxation (the largest subgroup); voluntary PSI with or without progression to involuntary PSI; and PPSI (the smallest subgroup). PPSI was defined as pain with anatomical findings indicating posterior instability but no instability events.

Data collection

We recorded the following data: sex; side involved; dominant side; age at symptom onset; age at treatment; sports activities; whether PPSI was due to trauma; overall shoulder mobility; shoulder laxity; Beighton's criteria [START_REF] Beighton | Orthopedic aspects of the Ehlers-Danlos syndrome[END_REF]; and results of posterior, anterior, and inferior apprehension tests. Standard radiographs (anteroposterior views in neutral, external, and internal rotation and scapular Y view) and axial slice images with intra-articular contrast injection (computed tomography [CT] and/or magnetic resonance imaging) were evaluated. Treatment outcomes were evaluated based on the Constant's pain subscore (with a value of 0 indicating the worst pain possible and a value of 15 no pain), Constant's score [START_REF] Roy | A systematic review of the psychometric properties of the Constant-Murley score[END_REF][START_REF] Constant | A clinical method of functional assessment of the shoulder[END_REF][START_REF] Wright | Shoulder outcomes measures[END_REF], and the Subjective Shoulder Value (SSV) [START_REF] Gilbart | Comparison of the subjective shoulder value and the Constant score[END_REF].

Statistical analysis

Descriptive statistics were computed. The Shapiro-Wilk test was used to assess distribution normality. Differences between mean values were compared by applying Student's test when distribution was normal and the Mann-Whitney test otherwise. The Chi 2 test was chosen to evaluate associations linking categorical variables. Statistical analyses were performed using R software version 3.3.3. (R Foundation, Vienna, Austria). Values of P < 0.05 were considered statistically significant.

Results

Patients

Of the 25 study patients with PPSI, 23 were included retrospectively and 2 prospectively. There were 16 males and 9 females with a mean age of 30 years (range, 16-45 years). The right shoulder was involved in 15 patients and the left shoulder in 10 patients; the dominant side was involved in 68% of cases. A history of trauma was noted in 80% of patients. Furthermore, 84% of patients reported engaging in sports overall, 46% in recreational sports, and 38% in competitions. Among patients with sports activities, 83% participated in sports that place strain on the shoulders (boxing, handball, volleyball, tennis, judo, rugby, weight-lifting) (Table 1). Mean time from symptom onset to surgery was 23 months (median, 15 months; range, 3-93 months).

Physical findings

The posterior apprehension test in adduction and internal rotation was positive in 40% of patients, the anterior apprehension test in abduction and external rotation in 40% of patients, and the inferior Gagey apprehension test in 20% of patients [START_REF] Gagey | The hyperabduction test[END_REF]. The anterior test was the only positive apprehension test in 20% of patients.

Imaging study findings

On the imaging studies, 52% of shoulders had no bony abnormalities related to instability (glenoid erosion or fracture, reverse Hills-Sachs notch). In contrast, 22% of shoulders had damage to the glenoid cartilage. In keeping with this finding, the surgical exploration found cartilage damage to the glenoid in 28% of cases (Fig. 1) and to the humeral head in 8% of cases.

Management

All 25 patients underwent surgical treatment. Surgery consisted in arthroscopic capsulo-labral reconstruction in 22 patients (Fig. 2). An overhanging iliac bone block was implanted in 2 patients and a flush acromial bone block in 1 patient. After surgery, the shoulder was immobilised in neutral rotation in 74% of patients.

Outcomes

Overall outcomes

The SSV improved from 45% before surgery to 82% after surgery. After surgery, the Walch-Duplay score was 76 and the Rowe score was 81. The crude Constant score improved from 67 preoperatively to 81 postoperatively (Table 2). After surgery, 74% of patients reported being satisfied by the procedure and had resumed their main sports activity.

Clinical outcomes

The assessment of postoperative pain differentiated three groups of patients (Table 3). Major pain relief defined as a Constant pain subscore of 13-15 was noted in 43% of patients and moderate pain relief with a Constant pain subscore of 10-12 in 43% of patients. The treatment failed in the remaining 3 (14%) patients, who had unchanged or worsened pain with a Constant pain subscore lower than 5.

Anatomical outcomes

Of the 3 patients with treatment failure, 1 had bipolar osteoarthritis with static posterior subluxation, 1 had early anchor migration, and 1 had acromial block nonunion.

Partial improvement was noted in 11 patients with persistent but moderate pain. Among them, 50% had glenoid cartilage damage visible during arthroscopy and 40% on imaging studies. In this group, 2 patients had postoperative shoulder stiffness, 1 had osteolysis of an iliac bone block, and 2 had deep reverse Hill-Sachs notches.

Surgery was successful in 11 patients, who reported little or no postoperative pain. None of these patients had cartilage damage, postoperative shoulder stiffness, surgical complications (anchor migration or bone block lysis), or reverse Hill-Sachs notches.

Discussion

The shoulder is the least stable joint in the body, with less than one-third of the humeral head surface in contact with the glenoid cavity. Static stability is provided by the joint cartilage, labrum, and ligaments [START_REF] Wang | Pathomechanics of acquired shoulder instability: a basic science perspective[END_REF]. The structures responsible for posterior stability are the posterior capsule, inferior glenohumeral ligament, and posterior labrum. Damage to any of these structures can therefore result in PSI [START_REF] Tannenbaum | Evaluation and management of posterior shoulder instability[END_REF][START_REF] Pagnani | Stabilizers of the glenohumeral joint[END_REF]. Our study confirms the existence of PPSI as a clinical entity in which pain is the only symptom. Furthermore, the results support our hypothesis that treatment outcomes vary, depending on the presence of preexisting bone and cartilage lesions.

The patient profile was similar to that seen in involuntary PSI. Thus, many patients engaged in sports that put strain on the shoulders and reported a trauma as the inciting event. No patients had ligament laxity or joint hypermobility. Time from symptom onset to surgery was less than 2 years in the patients with PPSI, compared to 6 years in the group with involuntary PSI and 8 years in the group with voluntary-to-involuntary PSI. These differences suggest that pain may be less well tolerated than posterior instability events.

The physical findings were limited. Thus, the posterior apprehension test was negative in over 60% of patients and the only positive apprehension test was anterior in 20% of patients. The diagnostic was usually provided by a finding of posterior labral damage on imaging studies.

The main preoperative predictor of treatment outcomes was the presence of cartilage damage. The differential diagnoses of PPSI are incipient posterior osteoarthritis with subluxation and posterosuperior impingement syndrome. Diagnostic errors may lead to inappropriate stabilising surgery, which may worsen the condition [START_REF] Wang | Pathomechanics of acquired shoulder instability: a basic science perspective[END_REF].

Compared to the other PSI groups, the PPSI group had a higher proportion of patients managed by capsulo-labral reconstruction. The rationale for this procedure is the absence of bony alterations associated with instability and of ligament laxity. A meta-analysis indicated that arthroscopic capsulo-labral reconstruction provided better outcomes compared to bone block procedures [START_REF] Delong | Posterior instability of the shoulder: a systematic review and meta-analysis of clinical outcomes[END_REF]. Surgery should be considered in patients who have failed optimal nonoperative treatment given for at least 6 months. Non-operative treatment consists of proprioception exercises, strengthening exercises for the external rotators and scapular stabilisers, and sports activity modification [START_REF] Tannenbaum | Evaluation and management of posterior shoulder instability[END_REF].

Conclusion

PPSI with pain as the only symptom is the least common presentation of PSI. The diagnosis is often provided by imaging studies performed to assess shoulder pain in a young athlete. Surgical capsulo-labral reconstruction, seems to be a reliable treatment option [START_REF] Delong | Posterior instability of the shoulder: a systematic review and meta-analysis of clinical outcomes[END_REF] that produces good outcomes in patients without preexisting cartilage damage, postoperative complications, or postoperative shoulder stiffness. Damage to the posterior glenoid cartilage predicts incomplete improvement after surgery and should be sought routinely. The most common causes of treatment failure are diagnostic errors, technical errors, and postoperative complications [START_REF] Bradley | Arthroscopic capsulolabral reconstruction for posterior instability of the shoulder: prospective study of 100 shoulders[END_REF].

Fig. 1 .

 1 Fig. 1. Posterior cartilage damage.

Fig. 2 .

 2 Fig. 2. Re-attachment of the posterior labrum.

Table 1

 1 Study patients.

		Sex	Side	Age (years)	Trauma	Sports
	25 patients	16 (64%) males	Right, n = 15 (60%)	Minimum 16	Yes, 20/25 (80%)	Competition, 9/25 (38%)
		9 (36%) females	Left, n = 10 (40%)	Maximum 45	No, 5/25 (20%)	Recreational, 12/25 (46%)
			Dominant side involved in	Mean, 30		None, 4/25 (16%)
			17/25 (68%)

Table 2

 2 Functional and subjective outcomes.

		Before surgery	After surgery
	Constant, pain subscore	6	11.3
	Constant, total score	67	83
	SSV	45	82
	Walch-Duplay score		76
	Rowe score		81
	SSV: Subjective Shoulder Value.

Table 3

 3 Constant pain subscore.

		Pain subscore	Percentage
	Marked pain relief	13/15to 15/15	44
	Moderate pain relief	10/15 to 12/15	44
	No pain relief	Lower than 5/15	12

Disclosure of interest

The authors declare that they have no competing interest.


MD, PhD a , Xavier Ohl

MD, PhD Nicolas Bonnevialle
email: nicolasbonnevialle@yahoo.fr

MD c , David Gallinet

PhD Nassima Ramdane

MD e , Philippe Valenti

MD Lauryl Decroocq

MD, PhD Pascal Boileau

How the

Keywords: Proximal humerai fractures, reverse shoulder arthroplasty, greater tuberosity excision, greater tuberosity healing, shoulder instability, complication

Proximal humeral fractures (PHFs) are the third most corn.mon fracture in elderly persans and represent a significant challenge for orthopedic surgeons. [START_REF] Court-Brown | The spectrum of fractures in the elderly[END_REF] Fracture fixation in the elderly population increases tbe risk of failure owing to poor bone quality and avascular • ecrosis. On the other band, nonoperative treatment does not always lead to acceptable sboulder fonction because of the possibility of severe malunion in an o lder population of patients wanting to recover their quality of life after the in jury. Her• iarthroplasty bas been proposed as an alternative to fixation; however, clinical outcornes depend on anatomie healing of the tuberosities around the implant I Because reverse shouJder arthroplasty (RSA) has led to prornising results in patients with cuff deficiency, indications for this procedure have been expanded to complex PHFs. [START_REF] Cazeneuve | Delta III reverse shoulder arthroplasty: radiological outcome for acute complex fractures of the proximal humerus in elderly patients[END_REF] Optimal management of the tuberosities in RSA remains unclear and controversial. Sorne authors reported satisfactory clinical outcomes of RSA after removaJ of both tuberosities. [START_REF] Bonnevialle | Hemiarthroplasty versus reverse shoulder arthroplasty in 4-part displaced fractures of the proximal humerus: multicenter retrospective study[END_REF] Others reported better active external rotation after fixation and healing of the tuberosities around the stem.4-6 However, despite slrong fixation, malunions, osteolysis, and nonunions have been reported. [START_REF] Bufquin | Reverse shoulder arthroplasty for the treatment of three-and four-part fractures of the proximal humerus in the elderly: a prospective review of 43 cases with a short-term follow-up[END_REF] • 7 • 11 T he aim of this study was to assess the clinical and radiologie outcomes of RSA implanted for acute PHFs in a large cohort of elderly patients and compare the results in patients with anatomie greater tuberosity (GT) healing, failed fixation (malunion, nonunion, or osteolysis), and GT excision. We hypothesized that better clinical outcomes would be observed in patients with healed tuberosities than in patients with failed tuberosity fixation or in those in whom the tuberosities have been excised.

Materials and methods

Study design

ln this retrospective multicenter study, we included patients with an acute PHF wbo were treated with a primary RSA between January 2010 and December 2015, regardless of whether the GT was fixed or removed, and who had a minimum follow-up period of 12 months. We excluded patients with pathologie fractures (primary tumor or metastasis), patients with previous surgery on the involved shoulder, patients in whom surgery was performed more than 6 weeks after the injury occurred, and patients without plain anteroposterior radiographs of the shoulder at 12 months after surgery. Patients gave their consent for the analysis of their clinical and radiologie data.

Patient popu lation

Five hundred sixty-seven patients were eligible, and 420 patients (74%) with an RSA implanted for an acute PHF were reviewed and underwent radiography with minimum 1-year follow-up (Fig. 1 ). The mean age at surgery was 78 years, 83% of patients were women, the mean body mass index was 26.3 ± 5.5 kg/m2, and the injured shoulder was on the dominant side in 58% of cases. The American Society of Anesthesiologists score was III or N in 38% of the cohort.

Su rgical techni que

A deltopectoral approach (n = 100) or deltoid-splitting approach (n = 320) was performed with patients in the beach-chair position. Six different RSA models were used; 48% (n = 200) were specifically designed to treat PHFs with a low-profile stem and bone grafting around the metaphysis. A cemented stem was used in 88% of cases (n = 370). The glenosphere diameter was 36 mm in 66% of cases. ln 300 RSA cases, both tuberosities were fixed with 2 or 4 horizontal cerclages around the metaphysis. For the remaining 120 RSAs, the surgeons decided to excise the greater and lesser tuberosities. Postoperatively, the shoulder was placed in a sling in 75% of cases. Physiotherapy was started immediately with free range of motion in 55%.

Patients lncluded

Radiologic evaluation

Anteroposterior views in the neutral position were analyzed (minimum, 12 months) to determine the status of the GT and classify the patients into 3 groups:

-Group A showed anatomic tuberosity healing, in which the GT was visible on the lateral part of the stem, at the level with or below (no more than 5 mm) the prosthetic head, and in continuity with the diaphysis (Fig. 2). -Group B had failed anatomic healing with malunion, nonunion, or resorption (Fig. 3).

-Group C underwent excision of the tuberosities at the time of surgery (Fig. 4).

Clinical assessment

The Constant-Murley score (CMS) and Simple Shoulder Value (SSV) were used to determine the functional outcome. [START_REF] Boileau | Reversed shoulder arthroplasty with modified L'Episcopo for combined loss of active elevation and external rotation[END_REF][START_REF] Constant | A review of the Constant score: modifications and guidelines for its use[END_REF][START_REF] Gilbart | Comparison of the subjective shoulder value and the Constant score[END_REF] For active range of motion, elevation (active anterior elevation) was measured with a goniometer (patient in a seated position) in the sagittal plane and external rotation was measured in the coronal plane with the arm by the patient's side and in 90°of abduction. Internal rotationmeasured as the highest vertebral level the patient could reach behind his or her back-was translated into a numerical value as in the CMS.

Statistical analysis

Statistical tests were performed by an independent epidemiologic department using the SAS software package (release 9.4; SAS Institute, Cary, NC, USA). Data are presented as number (percentage) for categorical variables and mean ± standard deviation (range) for quantitative variables. The normality of distribution was checked graphically and by using the Shapiro-Wilk test. Demographic data and outcome scores between the 3 groups according to GT status were compared using the χ 2 or Fisher exact test for categorical variables and Kruskal-Wallis test for quantitative variables. We also performed Dwass-Steel-Critchlow-Fligner multiple-comparison analysis, which is based on pair-wise 2-sample Wilcoxon comparisons. The significance threshold was set at .05.

Results

Complications and revision

There were 10 postoperative infections (2.4%), 6 cases of glenoid loosening (1.4%), and 8 cases of humeral loosening (1.9%). Of the shoulders, 20 (4.7%) were unstable, with early dislocations (<1 month) in 16 and late dislocations in 4. Six were stable after closed reduction, whereas 4 others remained unstable but were left in their dislocated state because of an unacceptable perioperative risk of revision surgery. Reoperation was performed on 13 shoulders: 12 were successfully revised and 1 implant was removed.

Clinical results

At a mean follow-up of 28 months (range, 12-60 months), the mean CMS was 57 ± 15 points, the mean adjusted CMS was 86% ± 23%, and the mean SSV was 70% ± 18%. Overall, mean active anterior elevation reached 115°± 30°, mean active external rotation with the arm at the side was 17°± 17°, mean external rotation in 90°of abduction was 32°± 25°, and mean internal rotation was 4 ± 2 points (sacrum).

Radiologic results

The patients were divided into 3 groups according to GT status as defined earlier: group A (anatomic GT healing, n = 169 [40%]), group B (GT resorption, malunion, or nonunion; n = 131 [31%]), and group C (GT excision, n = 120 [29%]).

There was no significant difference in demographic characteristics between groups A, B, and C (Table I).

Influence of tuberosity conservation and healing

Patients in group A (tuberosity healing) had the best shoulder function, the best range of active motion, and the highest subjective shoulder values (Table II). Overall, the mean adjusted CMS was significantly higher in group A (93% ± 22%) than in group B (82% ± 22%) and group C (80% ± 24%) (P < .001), but there was no difference between group B and group C (P = .88).

At last follow-up, the mean SSV in group A (75%) outperformed the results found in groups B (69%, P < .001) and C (56%, P < .001). Anterior active elevation was significantly better in group A (127°± 27°) than in groups B (114°± 29°) and C (101°± 25°, P < .001). Active external rotation was also significantly better in group A (22°± 16°) than in groups B (17°± 20°) and C (7°± 7°, P < .001). Finally, the rate of postoperative shoulder instability was significantly higher in group C (12%, P < .0001) than in group A (n = 2) or group B (n = 3). The other complications were not correlated with the type of group.

Discussion

In this large cohort of 420 patients who underwent review and radiography with a mean follow-up period of 28 months (range, 12-60 months), we found that tuberosity reattachment and healing around the RSA were associated with the best functional outcomes, the best range of active motion, and the best subjective outcomes. Patients with GT malunion, nonunion, or osteolysis had significantly lower active range of motion, functional results, and SSVs, whereas patients in whom the tuberosities had been excised had the worst clinical and subjective outcomes and the highest risk of shoulder instability (12.5%).

Instability after RSA implantation is a severe postoperative complication. The fact that tuberosity excision is increasing the risk of postoperative instability is not surprising: After excision of the tuberosities, the stabilizing effect of soft tissues (rotator cuff) around the ball-and-socket joint is lost. Moreover, the anatomic landmark provided by the GT reduction is lost, making it difficult (if not impossible) to determine the height of the prosthesis. Without the GT landmark, the humerus can be potentially shortened (ie, the prosthesis can be implanted too low), which can contribute to postoperative instability. Unfortunately, because we did not make postoperative measurements of both humeri at last review, we were not able to validate this hypothesis.

RSA for the treatment of displaced PHFs in elderly patients is gaining popularity among surgeons because clinical results are more reliable than those obtained with hemiarthroplasty. [START_REF] Boileau | Tuberosity malposition and migration: reasons for poor outcomes after hemiarthroplasty for displaced fractures of the proximal humerus[END_REF][START_REF] Bufquin | Reverse shoulder arthroplasty for the treatment of three-and four-part fractures of the proximal humerus in the elderly: a prospective review of 43 cases with a short-term follow-up[END_REF][START_REF] Cazeneuve | The reverse shoulder prosthesis in the treatment of fractures of the proximal humerus in the elderly[END_REF][START_REF] Cazeneuve | Delta III reverse shoulder arthroplasty: radiological outcome for acute complex fractures of the proximal humerus in elderly patients[END_REF][START_REF] Chun | Reverse shoulder arthroplasty for four-part proximal humerus fracture in elderly patients: can a healed tuberosity improve the functional outcomes?[END_REF][START_REF] Gallinet | Improvement in shoulder rotation in complex shoulder fractures treated by reverse shoulder arthroplasty[END_REF][START_REF] Gilbart | Comparison of the subjective shoulder value and the Constant score[END_REF][START_REF] Sebastiá-Forcada | Reverse shoulder arthroplasty versus hemiarthroplasty for acute proximal humeral fractures. A blinded, randomized, controlled, prospective study[END_REF] Since RSA has been designed to overcome cuff-deficient shoulders, some surgeons have proposed excising the tuberosities, [START_REF] Cazeneuve | The reverse shoulder prosthesis in the treatment of fractures of the proximal humerus in the elderly[END_REF][START_REF] Cazeneuve | Delta III reverse shoulder arthroplasty: radiological outcome for acute complex fractures of the proximal humerus in elderly patients[END_REF] whereas others have suggested that tuberosity reattachment is less important than in hemiarthroplasty. [START_REF] Formaini | Tuberosity healing after reverse shoulder arthroplasty for acute proximal humerus fractures: the "black and tan" technique[END_REF][START_REF] Gallinet | Improvement in shoulder rotation in complex shoulder fractures treated by reverse shoulder arthroplasty[END_REF] The question that we attempted to answer in this study was as follows: Are clinical and subjective outcomes of RSA for PHFs comparable in the case of tuberosity excision, failed fixation, or anatomic healing? To try to answer this question, we performed a multicenter study and analyzed the clinical and subjective results based on the surgical tuberosity management (excision vs conservation) and the final aspect of the tuberosities on the last postoperative radiographs (GT healing in an anatomic position vs nonunion, malunion, or resorption).

Our study data suggest that healing of the GT in an anatomic position is required to achieve the best functional outcomes in patients with RSA for PHFs. As a result, surgeons should make all efforts to perform conservation, bone grafting, and fixation of the tuberosities to obtain bone healing around the prosthesis, and they should discontinue tuberosity excision in RSA for acute PHFs.

The results found in this study are similar to those reported in the literature and confirm that tuberosity excision should not be performed in patients who receive an RSA for acute fracture. Cazeneuve and Cristofari 5 reported on their first RSA cases in 47 fractures with a mean follow-up period of more than 6 years (range, 1-16 years). They did not address the tuberosities and used an implant with a bulky metaphysis that was not specifically designed for fracture cases. They reported a mean Constant score at the last follow-up of 53 points and found a 10% rate of postoperative instability. Gallinet et al 11 compared 2 cohorts of RSAs with or without tuberosity fixation retrospectively. They concluded that preservation and fixation of the tuberosities led to better clinical outcomes in terms of active range of motion, especially in external rotation in abduction with a gain of +35°. Because external rotation can be provided by only the teres minor and infraspinatus muscles, GT fixation is necessary if we expect to restore spatial control of the hand during arm elevation and activities of daily living. However, successful healing in an anatomic position after GT fixation is difficult to achieve. Gallinet et al reported that only 64% of cases had anatomic healing after use of the suture technique described by Boileau et al. [START_REF] Boileau | Tuberosity malposition and migration: reasons for poor outcomes after hemiarthroplasty for displaced fractures of the proximal humerus[END_REF] More recently, Sebastiá-Forcada et al [START_REF] Sebastiá-Forcada | Reverse shoulder arthroplasty versus hemiarthroplasty for acute proximal humeral fractures. A blinded, randomized, controlled, prospective study[END_REF] reported the same rate. The addition of a lateral autograft (from the humeral head) between the metaphysis of the implant and tuberosities results in an anatomic healing rate of 80% to 100%. [START_REF] Formaini | Tuberosity healing after reverse shoulder arthroplasty for acute proximal humerus fractures: the "black and tan" technique[END_REF][START_REF] Garofalo | Reverse shoulder arthroplasty for proximal humerus fracture using a dedicated stem: radiological outcomes at a minimum 2 years of follow-up-case series[END_REF][START_REF] Levy | Reverse shoulder prosthesis for acute four-part fracture: tuberosity fixation using a horseshoe graft[END_REF] This study has the limitations related to a multicenter, retrospective study. One limitation is the high number of patients who died before 1 year or were too frail to be clinically reviewed with radiographs and therefore could not be included. Another limitation is related to the number of different implants used. A more lateralized design versus a medialized one may have potentially influenced the functional outcomes. Finally, we analyzed mainly the impact of GT healing and positioning, but we did not investigate the impact of the lesser tuberosity (healed or not) on clinical outcomes because the radiologic evaluation was not considered accurate enough. To our knowledge, this is the largest cohort of RSAs implanted for acute fractures reported in the literature today. Moreover, we stratified the patients and analyzed the results according to the tuberosity management and healing, and the 3 groups of patients studied (tuberosity healing vs tuberosity malunion or nonunion vs tuberosity excision) were comparable in terms of age, sex, and health status (American Society of Anesthesiologists score).

Conclusion

In elderly patients who have undergone an RSA for acute PHFs, tuberosity healing improves the clinical outcomes and decreases the risk of postoperative instability. Tuberosity fixation failure is associated with lower functional results, whereas tuberosity excision provides the worst functional results and the highest risk of postoperative instability. Our results suggest that tuberosity preservation, fixation, and healing are mandatory when RSA is used to treat displaced PHFs in an elderly population.

Disclaimer

The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.

Figure 1

 1 Figure 1 Flowchart.

Figure 2

 2 Figure 2 Anatomic healing of greater tuberosity.

Figure 3

 3 Figure 3 Malunion of greater tuberosity.Figure 4 Excision of greater tuberosity.

Figure 4

 4 Figure 3 Malunion of greater tuberosity.Figure 4 Excision of greater tuberosity.

Table I

 I Demographic characteristics of patients according to GT status

		Total (n = 420)	Group			P value
			A (n = 169)	B (n = 131)	C (n = 120)
	Age, yr	77.7 ± 7.7 (48-97)	78 ± 8 (45-97)	77 ± 8 (58-93)	77 ± 8 (58-93)	.19
	Female	86.4%	84.0%	84.0%	93.3%	.056
	ASA score III or IV	32.4%	30.8%	33.0%	33.3%	.86

GT, greater tuberosity; ASA, American Society of Anesthesiologists. Values are expressed as percentage or mean ± standard deviation (range). No difference was observed between groups. Group A showed anatomic healing; group B showed failed fixation (nonunion, osteolysis, or malunion); and group C underwent tuberosity excision.


Matthieu Ehlinger
email: matthieu.ehlinger@chru-strasbourg.fr

Alfred D'ambrosio

Pascal Vie

Sylvain Leclercq

François Bonnomet

Paul Bonnevialle

Sébastien Lustig

Sébastien Parratte

S Leclerc

M Colmar

J.-N Argenson

Total knee arthroplasty after opening-versus closing-wedge high tibial osteotomy. A 135-case series with minimum 5-year follow-up

Keywords:

come

Introduction: High tibial osteotomy (HTO) is effective in treating isolated medial osteoarthritis of the knee, but subsequent deterioration is inevitable, and total knee arthroplasty (TKA) is then an option. The present study sought to compare TKA following medial opening-wedge HTO (OW-HTO) versus lateral closing-wedge HTO (CW-HTO) in terms of intraoperative data and clinical results. The study hypothesis was that there is no significant difference in clinical results or complications in TKA following OW-HTO or CW-HTO. Material and method: A retrospective multicenter (9 centers) study was conducted for the French Society of Orthopedic Surgery and Traumatology (SoFCOT), including 135 TKAs following HTO (58 OW and 77 CW) at a minimum 5 years' follow-up. Mean interval between HTO and TKA was 134 months and was longer in case of CW-HTO (P < 0.0001). Mean age at TKA was 65.4 years and older in case of CW-HTO (P = 0.021). Tibial slope was greater in case of OW-HTO (P = 0.024). Prior to TKA, 55.7% of patients could walk without canes, 98.4% found stairs difficult or impossible and only 19.1% could manage a walking distance greater than 1000 m. Mean flexion was 110 • ; 54.2% of patients showed frontal knee stability and 87.8% sagittal stability; 60.1% had a mechanical axis in varus, without difference according to OWor CW-HTO. Results: Hardware was almost systematically removed (in 98.5% of cases): in the same step for OW-HTO (P = 0.018) or often in 2 steps for CW-HTO. The primary approach was generally re-used (54.2%), but less frequently in the CW-HTO group (P = 0.0004). Lateral or medial ligament release was not associated in respectively 78.2% and 79.7% of cases. The TKA implant was usually without stem (87.2%) and was fitted using a conventional technique (74.4%). At a mean 87 months' follow-up, 78.5% of patients could walk without canes, stairs were still difficult or impossible for 67%, and 74.1% could now walk further than 1000 m; mean flexion was 110.5 • . Overall, 91.5% of patients showed frontal knee stability and 98.2% sagittal stability, without difference according to OW-or CW-HTO. There were 15 complications within 3 months, more often in the OW-HTO group (12.3%) although not significantly, and with no difference in severity. Late complications comprised loosening (5.5%) and infection (3.6%) and were more frequent in the CW-HTO group (12%) (P < 0.05). Discussion: The study hypothesis was partially confirmed. The only technical differences concerned hardware removal, often performed in two steps in case of CW-HTO, and TKA approach, which differed from the primary approach in case of CW-HTO. Clinical results were comparable between OW-and CW-HTO, but late complications were more frequent in the CW-HTO group. Level of evidence: III; comparative retrospective study.

Introduction

High tibial osteotomy (HTO), by opening wedge (OW-HTO) or closing wedge (CW-HTO), is effective in treating medial osteoarthritis of the knee in young subjects [START_REF] Gstottner | Long-term outcome after high tibial osteotomy[END_REF], without difference between the two types of osteotomy [START_REF] Sun | Comparison between closing-wedge and opening-wedge high tibial osteotomy in patients with medial knee osteoarthritis: a systematic review and meta-analysis[END_REF]. Results are satisfactory, but longer-term deterioration is unavoidable [START_REF] Papachristou | Deterioration of long-term results following high tibial osteotomy in patients under 60 years of age[END_REF][START_REF] Virolainen | High tibial osteotomy for the treatment of osteoarthritis of the knee: a review of the literature and a meta-analysis of follow-up studies[END_REF]. Khoshbin et al. [START_REF] Khoshbin | The effect of patient, provider and surgical factors on survivorship of high tibial osteotomy to total knee arthroplasty: a population based study[END_REF] reported 67% 10-year survival in 2671 HTOs, with risk factors comprising age > 46 years, female gender, comorbidity and history of arthroscopy.

Surgical revision is thus necessary, usually in the form of total knee arthroplasty (TKA). Insall et al. [START_REF] Insall | High tibial osteotomy for varusgonarthrosis. A long-term follow-up study[END_REF] reported a 23% rate of TKA at 10 years after HTO.

TKA is reputed to be difficult following HTO, requiring management of the previous scar, extra-articular deformity, possible residual material, patellar height and ligament balance. Systematic literature reviews, meta-analyses and large-scale registries either find no difference between primary TKA and TKA following HTO or else report higher complications rates following HTO [START_REF] Han | Total knee arthroplasty after failed high tibial osteotomy: a systematic review of open versus closed wedge osteotomy[END_REF][START_REF] Badawy | The risk of revision in total knee arthroplasty is not affected by previous high tibial osteotomy[END_REF][START_REF] Niinimaki | Total kneearthroplasty after high tibial osteotomy: a registry-based case-control study of 1036 knees[END_REF][START_REF] Vanraaij | Total knee arthroplasty after high tibial osteotomy. A systematic review[END_REF][START_REF] Gupta | Outcomes of total knee arthroplasty following high tibial osteotomy[END_REF][START_REF] Haslam | Total knee arthroplasty after failed high tibial osteotomy long-term follow-up of matched groups[END_REF][START_REF] Kazakos | Midterm results of total knee arthroplasty after high tibial osteotomy[END_REF][START_REF] Efe | TKA following high tibial osteotomy versus primary TKA-a matched pair analysis[END_REF][START_REF] Saragaglia | Computer-assisted total knee replacement after medial opening wedge high tibial osteotomy: medium-term results in a series of ninety cases[END_REF][START_REF] Karabatsos | Functional outcome of total knee arthroplasty after high tibial osteotomy[END_REF]. There have been few studies comparing TKA following OW-HTO or following CW-HTO. Han et al. [START_REF] Han | Total knee arthroplasty after failed high tibial osteotomy: a systematic review of open versus closed wedge osteotomy[END_REF], in a systematic literature review, reported no difference.

The present study sought to compare TKA following medial OW-HTO versus lateral CW-HTO in terms of intraoperative data, clinical results and complications. The study hypothesis was that there is no significant difference in clinical results or complications in TKA following OW-HTO or CW-HTO.

Patients and method

Series

A retrospective multicenter study was conducted for the French Society of Orthopedic Surgery and Traumatology (SoFCOT) as part of the November 2016 symposium, including 135 TKAs following HTO performed over a 5-year period from January 1, 2005 to December 31, 2009. Nine centers participated.

Inclusion criteria comprised: TKA after OW-HTO or after CW-HTO (whatever the model of TKA), with at least 5 years' follow-up after TKA.

Exclusion criteria comprised:

• femoral osteotomy;

• revision of osteotomy by unicompartmental implant;

• revision of osteotomy;

• tibial medial closing-wedge;

• tibial lateral opening-wedge. The series comprised 135 patients (54% female): 58 OW-HTOs (43%) and 77 CW-HTOs (57%). Mean age was 65.4 years (range, 31-87; median, 64) and mean weight 85 kgs (range, 44-185; median, 82). Before the TKA, 55.7% could walk without canes; 98.4% found stairs difficult or impossible; 80.9% could walk only less than 1000 m. Mean flexion was 110 • ; the knee was stable frontally in 54.2% of cases, and sagittally in 87.8%. The mechanical axis was in varus in 60.1% of cases (Table 1).

The two groups differed in as much as age was greater in the CW group (P = 0.021) and tibial slope greater in the OW group (P = 0.024) (Table 1).

Method

Clinical (flexion, stability, autonomy, walking distance, stairs, walking aids) and radiological data (HKA angle) were assessed at last follow-up. Pain was self-scored as "none", "occasional" (once a month), "moderate" (once a week) or "severe" (every day). Results were considered "good" if autonomy (walking and stairs) and pain improved.

Laxity was assessed clinically according to the examiner's judgment. The mechanical axis was considered to be in varus if HKA < 180 • . Loosening was defined by progressive radiolucency. Complications were noted: earlier than 3 months and at last followup.

Kaplan-Meier survival curves were drawn up for each HTO group, considering TKA revision as endpoint.

Statistical analysis

Statistical analysis was descriptive (range, mean, median). Qualitative variables were compared on Fisher's test and quantitative variables on Wilcoxon test for matched pairs. The significance threshold was set at P < 0.05. Analysis used SAS software.

Results

Intraoperative data

Mean HTO-to-TKA interval was 134 months and was longer in the CW group (P < 0.0001) (Table 2).

TKA was in all cases posterior-stabilized without further constraint, but the model was left up to the surgeon.

The groups did not differ (Table 2) in terms of conventional or navigation-assisted technique, use of an extension stem or frequency of lateral or medial release. The primary incision was more frequently re-used in the OW group (P = 0.0004).

Hardware was removed in 98.5% of cases and in the same surgical step in 47.3%. One-step removal was more frequent in case of OW-HTO (P = 0.018).

Clinical and radiological results

Table 3 shows overall results. At a mean 86.7 months, post-TKA (range, 2-136 months: 88.9 months in OW-HTO and 84.9 months in CW-HTO), there was significant improvement in pain, unassisted walking, stairs, walking distance, leaving the house, extension and stability.

There were no clinical or radiological differences between groups (Table 4).

Complications

There were 15 early complications (Table 5). Although they were more frequent in the OW group (12.3% versus 8.3%), the difference was not significant (P > 0.05). In the 111 files documenting late complications during followup, there were 11 cases of revision surgery: 6 for loosening (5.5%) at a mean 59 months, 4 for infection (3.6%) at a mean 34 months and 1 for a "technical problem". Late complications were more frequent in the CW-HTO group (12% versus 6%; P < 0.05).

Survival curves

Ten-year survival was 94% (95% CI: [83-98]) in the OW-HTO group and 82% (95% CI: [61-93]) in the CW-HTO group, without significant difference (P = 0.338) (Fig. 1).

Discussion

Surgical habits for TKA after HTO were unchanged despite this context of HTO revision, with few stems used and mostly conventional surgery. In the CW group, hardware removal was mainly performed as a separate step and the primary approach was not mainly reutilized for TKA. Long-term clinical outcome was good and comparable between groups. Late complications, however, were more frequent in the CW group (12% versus 6%). The study hypothesis was thus partially confirmed.

The present results are comparable to those in the literature (systematic reviews, meta-analyses, comparative series and largescale registries [START_REF] Han | Total knee arthroplasty after failed high tibial osteotomy: a systematic review of open versus closed wedge osteotomy[END_REF][START_REF] Badawy | The risk of revision in total knee arthroplasty is not affected by previous high tibial osteotomy[END_REF][START_REF] Niinimaki | Total kneearthroplasty after high tibial osteotomy: a registry-based case-control study of 1036 knees[END_REF][START_REF] Vanraaij | Total knee arthroplasty after high tibial osteotomy. A systematic review[END_REF][START_REF] Gupta | Outcomes of total knee arthroplasty following high tibial osteotomy[END_REF][START_REF] Haslam | Total knee arthroplasty after failed high tibial osteotomy long-term follow-up of matched groups[END_REF][START_REF] Kazakos | Midterm results of total knee arthroplasty after high tibial osteotomy[END_REF][START_REF] Efe | TKA following high tibial osteotomy versus primary TKA-a matched pair analysis[END_REF][START_REF] Saragaglia | Computer-assisted total knee replacement after medial opening wedge high tibial osteotomy: medium-term results in a series of ninety cases[END_REF][START_REF] Karabatsos | Functional outcome of total knee arthroplasty after high tibial osteotomy[END_REF]) for TKA following HTO and primary TKA, with improved autonomy and conserved range of motion. Analyzing the literature in the light of levels of evidence, however, refines these conclusions.

Level-IV retrospective series confirm clinical improvement, but with a relatively high rate of complications (6-15%), revision surgery and malalignment [START_REF] Han | Total knee arthroplasty after failed high tibial osteotomy: a systematic review of open versus closed wedge osteotomy[END_REF][START_REF] Badawy | The risk of revision in total knee arthroplasty is not affected by previous high tibial osteotomy[END_REF][START_REF] Niinimaki | Total kneearthroplasty after high tibial osteotomy: a registry-based case-control study of 1036 knees[END_REF][START_REF] Vanraaij | Total knee arthroplasty after high tibial osteotomy. A systematic review[END_REF][START_REF] Gupta | Outcomes of total knee arthroplasty following high tibial osteotomy[END_REF], as in the present study. Gupta et al. [START_REF] Gupta | Outcomes of total knee arthroplasty following high tibial osteotomy[END_REF] reported a 50-point improvement in IKS score and 32 • improvement in flexion, but with a major complications rate of 14%. In contrast, at 15 years' follow-up, the Norwegian registry [START_REF] Badawy | The risk of revision in total knee arthroplasty is not affected by previous high tibial osteotomy[END_REF] found no difference in survival between primary TKA and TKA following HTO, although the proportions of reasons for revision differed: in primary TKA failure comprised 28% loosening or wear, 21% infection and 6% pain and in TKA following HTO 35% loosening or wear, 12% infection and 11% pain.

In level-III case-control studies comparing primary TKA versus TKA following HTO, results are less clear-cut and more controversial [START_REF] Haslam | Total knee arthroplasty after failed high tibial osteotomy long-term follow-up of matched groups[END_REF][START_REF] Kazakos | Midterm results of total knee arthroplasty after high tibial osteotomy[END_REF][START_REF] Efe | TKA following high tibial osteotomy versus primary TKA-a matched pair analysis[END_REF][START_REF] Saragaglia | Computer-assisted total knee replacement after medial opening wedge high tibial osteotomy: medium-term results in a series of ninety cases[END_REF][START_REF] Karabatsos | Functional outcome of total knee arthroplasty after high tibial osteotomy[END_REF]. Clinical results were comparable in 2 reports [START_REF] Kazakos | Midterm results of total knee arthroplasty after high tibial osteotomy[END_REF][START_REF] Saragaglia | Computer-assisted total knee replacement after medial opening wedge high tibial osteotomy: medium-term results in a series of ninety cases[END_REF] and better in primary TKA in 2 others [START_REF] Efe | TKA following high tibial osteotomy versus primary TKA-a matched pair analysis[END_REF][START_REF] Karabatsos | Functional outcome of total knee arthroplasty after high tibial osteotomy[END_REF]. Complications rates were comparable in 4 series [START_REF] Haslam | Total knee arthroplasty after failed high tibial osteotomy long-term follow-up of matched groups[END_REF][START_REF] Kazakos | Midterm results of total knee arthroplasty after high tibial osteotomy[END_REF][START_REF] Efe | TKA following high tibial osteotomy versus primary TKA-a matched pair analysis[END_REF][START_REF] Karabatsos | Functional outcome of total knee arthroplasty after high tibial osteotomy[END_REF], with identical revision rates in only 1 report [START_REF] Karabatsos | Functional outcome of total knee arthroplasty after high tibial osteotomy[END_REF] and good alignment in 3 [START_REF] Kazakos | Midterm results of total knee arthroplasty after high tibial osteotomy[END_REF][START_REF] Efe | TKA following high tibial osteotomy versus primary TKA-a matched pair analysis[END_REF][START_REF] Saragaglia | Computer-assisted total knee replacement after medial opening wedge high tibial osteotomy: medium-term results in a series of ninety cases[END_REF]. The most striking report was by Efe et al. [START_REF] Efe | TKA following high tibial osteotomy versus primary TKA-a matched pair analysis[END_REF], with nearly 10 • gain in flexion, a 12-point improvement in IKS score and a 50% lower revision rate in primary TKA.

Finally, Meding et al. [START_REF] Meding | Does high tibial osteotomy affect the success or survival of a total knee replacement?[END_REF] published an original study with 15 years' follow-up, comparing primary TKA and TKA following HTO in the same patient; in the 39 patients, there were no clinical or radiological differences, with 100% 15-year survival in primary TKA and 97% in TKA following HTO.

The most frequent complications in the present post-HTO-TKA series were those commonly reported:

• skin complications; • infection; • stiffness. There were no differences according TKA after OW-HTO or TKA after CW-HTO in our study, in agreement with the literature [START_REF] Han | Total knee arthroplasty after failed high tibial osteotomy: a systematic review of open versus closed wedge osteotomy[END_REF][START_REF] Bastosfilho | Total knee arthroplasty after high tibial osteotomy: a comparison of opening and closing wedge osteotomy[END_REF][START_REF] Preston | Total knee arthroplasty after high tibial osteotomy: no difference between medial and lateral osteotomy approaches[END_REF][START_REF] Kuwashima | Comparison of the impact of closing wedge versus opening wedge high tibial osteotomy on proximal tibial deformity and subsequent revision to total knee arthroplasty[END_REF]. BastosFihlo et al. [START_REF] Bastosfilho | Total knee arthroplasty after high tibial osteotomy: a comparison of opening and closing wedge osteotomy[END_REF], comparing 117 TKAs after CWand 24 after OW-HTO, found identical gain in range of motion and functional scores and comparable alignment correction, although with more frequent complementary intraoperative procedures in the CW group:

• 1 medial release; • 1 anterior tibial tuberosity osteotomy; • 1 quadriceps snip;

• more frequent posterolateral release [START_REF] Bastosfilho | Total knee arthroplasty after high tibial osteotomy: a comparison of opening and closing wedge osteotomy[END_REF].

Generally, all authors underline that TKA is more demanding after HTO, with more frequent complementary procedures [START_REF] Han | Total knee arthroplasty after failed high tibial osteotomy: a systematic review of open versus closed wedge osteotomy[END_REF][START_REF] Gupta | Outcomes of total knee arthroplasty following high tibial osteotomy[END_REF][START_REF] Bastosfilho | Total knee arthroplasty after high tibial osteotomy: a comparison of opening and closing wedge osteotomy[END_REF][START_REF] Preston | Total knee arthroplasty after high tibial osteotomy: no difference between medial and lateral osteotomy approaches[END_REF][START_REF] Kuwashima | Comparison of the impact of closing wedge versus opening wedge high tibial osteotomy on proximal tibial deformity and subsequent revision to total knee arthroplasty[END_REF][START_REF] Cerciello | Total knee arthroplasty after high tibial osteotomy[END_REF][START_REF] Erak | Total knee arthroplasty following medial opening wedge tibial osteotomy: technical issues early clinical radiological results[END_REF]. This is attributed to architectural changes in the proximal tibia due to HTO: altered tibial slope, epiphyseal enlargement, metaphyseal malunion, possible lateral impingement by the tibial base in CW-HTO, and change in patellar height [START_REF] Sun | Comparison between closing-wedge and opening-wedge high tibial osteotomy in patients with medial knee osteoarthritis: a systematic review and meta-analysis[END_REF][START_REF] Han | Total knee arthroplasty after failed high tibial osteotomy: a systematic review of open versus closed wedge osteotomy[END_REF][START_REF] Saragaglia | Computer-assisted total knee replacement after medial opening wedge high tibial osteotomy: medium-term results in a series of ninety cases[END_REF][START_REF] Dragosloveanu | The effect of high tibial osteotomy on the posterior tibial slope[END_REF][START_REF] El Amrani | Patellar height relevance in opening-wedge high tibial osteotomy[END_REF], as well as vascular risk in CW-HTO [START_REF] Darnis | Vascular injuries during closing-wedge high tibial osteotomy: a cadaveric angiographic study[END_REF]. The recent introduction of personalized cutting-guides in OW-HTO has reduced architectural alteration in tibial slope, improving reproducibility [START_REF] Munier | Can three-dimensional patient-specific cutting guides be used to achieve optimal correction for high tibialosteotomy? Pilot study[END_REF]. The present study did not confirm these technical findings, but did highlight the fact that hardware removal tended to be performed in a separate step in the CW group and with a new incision for TKA. This was not reported by Han et al. [START_REF] Han | Total knee arthroplasty after failed high tibial osteotomy: a systematic review of open versus closed wedge osteotomy[END_REF] or Preston et al. [START_REF] Preston | Total knee arthroplasty after high tibial osteotomy: no difference between medial and lateral osteotomy approaches[END_REF], who found no difference according to the approach used for revision TKA.

Despite these frequently highlighted technical issues, the literature shows that a gliding prosthesis without adding a stem is usually enough to stabilize the knee [START_REF] Gupta | Outcomes of total knee arthroplasty following high tibial osteotomy[END_REF][START_REF] Cerciello | Total knee arthroplasty after high tibial osteotomy[END_REF][START_REF] Robertsson | the risk of revision after TKA is affected by previous HTO or UKA[END_REF][START_REF] Mason | Meta-analysis of alignment outcomes in computer-assisted total knee arthroplasty surgery[END_REF][START_REF] Chen | Cruciate retaining versus posterior stabilized total knee arthroplasty after previous high tibial osteotomy[END_REF][START_REF] Akasaki | Total knee arthroplasty following failed high tibial osteotomy: mid-term comparison of posterior cruciate-retaining versus posterior stabilized prosthesis[END_REF][START_REF] Walther | Results of posterior cruciateretaining unconstrained total knee arthroplasty after proximal tibial osteotomy for osteoarthrosis: a prospective cohort study[END_REF]. The rationale for posterostabilization is that there is frequent posterior cruciate ligament failure, especially in case of severe bone defect. Posterostabilization improves knee stability and clinical outcome. The present study confirmed these findings. Navigation may be useful [START_REF] Saragaglia | Computer-assisted total knee replacement after medial opening wedge high tibial osteotomy: medium-term results in a series of ninety cases[END_REF] but was not used in most of the present cases. The inclusion period was too early for the use of personalized cutting guides to be analyzed.

The study involved certain limitations. The retrospective multicenter design could have incurred a risk of missing data and variation in techniques and practices, but in fact this did not happen. The multicenter design, on the other hand, enabled a large series to be included, indeed one of the largest in the literature for TKA after HTO. The minimum 5-year follow-up was sufficient to meet objectives and test the study hypothesis. The lack of functional scoring and precise radiologic assessment was another limitation; but comparative study on the same set of technical and clinical criteria limited bias.

Conclusion

The present series of TKA following HTO confirmed that clinical outcome is good, with no differences between CW-and OW-HTO, except for more frequent late complications with CW-HTO. In case of CW-compared to OW-HTO:

Fig. 1 .

 1 Fig. 1. Survival curve. Blue: survival of total knee arthroplasty after closing-wedge high tibial osteotomy. Red: survival of total knee arthroplasty after opening-wedge high tibial osteotomy, 95% confidence intervals.

Table 1

 1 Description of the series at the time of TKA.

		Full series	TKA after OW-HTO	TKA after CW-HTO	P
					(OW/CW)
	n	135	58	77
	Female	73 (54%)	32 (55.2%)	41 (53.2%)	NS
	Age (years)	65.4	63.2	67	P = 0.021
	Weight (kg)	85.5	84	86.7	NS
	Unassisted walking	75/131 (55.7%)	35/58 (60.3%)	40/77 (51.9%)	NS
	Stairs impossible	40/130 (30.7%)	17/57 (29.8%)	23/73 (31.5%)	NS
	Stairs difficult	88/130 (67.7%)	39/57 (68.4%)	49/73 (67.1%)	NS
	Walking distance > 1000 m	25/131 (19.1%)	12/58 (20.7%)	13/73 (17.8%)	NS
	Not leaving the house	12/131 (9.2%)	8/58 (13.8%)	4/73 (5.5%)	NS
	Mean flexion ( 0)	NS
	Frontal stability (< 5 • )	71/131 (54.2%)	34/58 (58.6%)	37/73 (50.7%)	NS
	Sagittal stability (< 5 • )	115/131 (87.8%)	50/58 (86.2%)	65/73 (89%)	NS
	Radiologic frontal axis (< 180 • )	77/128 (60.1%)	35/57 (61.4%)	42/71 (59.1%)	NS
	Mean tibial slope (

• ) 110 • (70 to140. med 110) 110 • (75 to 140. med 110) 108 • (70 to140. med 110) NS Mean extension ( • ) -5 • (0 to -30. med 0) -4 • (0 to -20. med 0) -6 • (0 to -30. med • ) 3.6 • (-10 to 20. med 0) 4.4 • (-8 to 15. med 5) 2.7 • (-10 to 20. med 3) P = 0.024 OW-HTO: opening-wedge high tibial osteotomy; CW-HTO: closing-wedge high tibial osteotomy; TKA: total knee arthroplasty; NS: non-significant.

Table 2

 2 Intraoperative data.

		Full series	TKA after OW-HTO	TKA after CW-HTO	P
					(OW/CW)
	n	135	58	77
	Mean HTO-TKA interval (months)	134 (8-393. med 117)	104 (8-332. med 99)	155 (12-393. med 140)	< 0.0001
	Hardware removal	129/131 (98.5%)	55/56 (98.2%)	74/75 (98.7%)	NS
	1-step ablation	62/131 (47.3%)	32/56 (57.1%)	30/75 (40%)	P = 0.018
	Primary incision re-used	71/131 (54.2%)	41/57 (71.9%)	30/74 (40.5%)	P = 0.0004
	No lateral ligament release	104/133 (78.2%)	43/58 (74.1%)	61/75 (81.3%)	NS
	No medial ligament release	106/133 (79.7%)	46/58 (79.3%)	60/75 (80%)	NS
	TKA with stem	17/133 (12.8%)	8/58 (13.8%)	9/75 (12%)	NS
	Conventional TKA	99/133 (74.4%)	45/58 (77.6%)	54/75 (72%)	NS
	TKA with navigation	34/133 (25.5%)	13/58 (22.4%)	21/75 (28%)	NS
	OW-HTO: opening-wedge high tibial osteotomy; CW-HTO: closing-wedge high tibial osteotomy; TKA: total knee arthroplasty; NS: non-significant.

Table 3

 3 Comparison between pre-TKA and last follow-up clinical data for the full series.

		Pre-TKA	Last follow-up	P
	n	135	135
	No or occasional pain	5/91 (5.5%)	88/118 (74.6%)	< 0.0001
	Unassisted walking	75/131 (55.7%)	91/116 (78.5%)	< 0.0001
	Stairs impossible	40/130 (30.7%)	10/115 (8.7%)	< 0.001
	Stairs difficult	88/130 (67.7%)	67/115 (58.2%)	< 0.0001
	Walking distance > 1000 m	25/131 (19.1%)	86/116 (74.1%)	< 0.0001
	Not leaving the house	12/131 (9.2%)	2/116 (1.7%)	< 0.001
	Mean flexion ( • )	110 • (70 to140, med 110)	110.5 • (80 to130, med 110)	NS
	Mean extension ( • )	-5 • (0 to -30, med 0)	-0.8 • (-20 to 0, med 0)	< 0.0001
	Frontal stability (< 5 • )	71/131 (54.2%)	108/118 (91.5%)	< 0.0001
	Sagittal stability (< 5 • )	115/131 (87.8%)	115/117 (98.2%)	< 0.005

NS: non-significant; pre-TKA: pre-total knee arthroplasty.

Table 4

 4 Outcomes: comparison of TKA after opening wedge osteotomie or closing wedge osteotomy.

		TKA after OW-HTO	TKA after -CW-HTO	P
				(OW/CW)
	n	58	77
	No or occasional pain	42/56 (75%)	46/62 (74.2%)	NS
	Unassisted walking	44/54 (81.5%)	47/62 (75.8%)	NS
	Stairs impossible	2/55 (3.6%)	8/60 (13.3%)	NS
	Stairs difficult	33/55 (60%)	34/60 (56.7%)	NS
	Walking distance > 1000 m	41/55 (74.5%)	45/61 (73.8%)	NS
	Not leaving the house	1/55 (1.8%)	1/61 (1.6%)	NS
	Mean flexion ( • )	111 • (80 to 130, med 110)	110 • (65 to 140, med 110)	NS
	Mean extension ( • )	0 • (-10 to 0, med 0)	-1 • (-20 to 0, med 0)	NS
	Frontal stability (< 5 • )	50/55 (90.9%)	58/63 (92%)	NS
	Sagittal stability (< 5 • )	53/54 (98.1%)	62/63 (98.4%)	NS
	Radiologic varus (< 180 • )	31/53 (58.5%)	36/61 (59%)	NS

OW-HTO: opening-wedge high tibial osteotomy; CW-HTO: closing-wedge high tibial osteotomy; TKA: total knee arthroplasty; NS: non-significant.

Table 5

 5 Early complications (< 3 months).

	Complication	n	OW-HTO	CW-HTO
	Skin necrosis	5	2	3
	Common peroneal nerve	1	-	1
	injury
	Posterior tibial nerve injury	1	1	-
	Rotational polyethylene	1	-	1
	dislocation
	Infection	3	2	1
	Joint stiffness	4	3	1
	OW-HTO: opening-wedge high tibial osteotomy; CW-HTO: closing-wedge high tib-
	ial osteotomy.

Fol low-u p (years)

Acknowledgments

The authors thank all the symposium members and their teams: P. Bizot (Paris), J.L. Briard (Rouen), O. Cantin (Lyon), G. Dereudre (Rouen), A. Grandjean (Paris), M. Ollivier (Marseille), G. Pirovano (Marseille) and S. Putman (Lille).

Special thanks to Pr. Duhamel's biostatistics department in Lille.

Disclosure of interest


Sophie Putman
email: sophie.putman@chru-lille.fr

Jean-Noël Argenson

Paul Bonnevialle

Matthieu Ehlinger

Pascal Vie

Sylvain Leclercq

Pascal Bizot

Sebastien Lustig

J.-N Argenson

S Parratte

N Ramdane

M Colmar

A French multicentre study of 263 patients

Keywords:

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

Introduction

Total knee arthroplasty (TKA) has shown a large gain in popularity, particularly over the last decade, and this trend is expected to continue as the spectrum of indications broadens [START_REF] Kurtz | Projections of primary and revisionhip and knee arthroplasty in the United States from 2005 to 2030[END_REF][START_REF] Niemeläinen | Different incidences of knee arthroplasty in the Nordic countries[END_REF]. Mean age at TKA for knee osteoarthritis was 70 years in 2012 [START_REF] Carr | Knee replacement[END_REF]. The ageing of the population, increasing patient expectations regarding function, and growing use of surgery to treat multiple conditions (trauma, ligament injury, conservative surgery) will increase the number of TKA procedures performed after trauma or surgery to the same knee.

A study done for the 2010 SoFCOT symposium showed that the 10-year survival of TKA for primary knee osteoarthritis was 92% [START_REF] Argenson | Survival analysis of total knee arthroplasty at a minimum 10 years' follow-up: a multicenter French nationwide study including 846 cases[END_REF]. In theory, TKA to treat knee osteoarthritis caused by trauma or surgery is associated with a higher risk of complications and a lower survival rate, but no accurate data from large populations followed-up for 10 years are available.

This retrospective study in 263 patients with TKA after knee trauma or surgery and a follow-up of 10 years was therefore designed based on the 2010 SoFCOT study of TKA survival in primary knee osteoarthritis. The objectives were to assess survival, functional outcomes, and the nature and frequency of complications. The working hypothesis was that knee trauma or surgery before TKA increased the risk of complications and decreased prosthesis survival compared to TKA for primary osteoarthritis.

Patients and methods

Patients

This multicentre study was designed to reflect the daily practice of nine centres in performing TKA to treat secondary knee osteoarthritis after knee injury or surgery between 2005 and 2009. The nine centres were each in a different French city (Caen, Lille, Lyon, Marseille, Paris Lariboisière, Rouen, Saint-Brieuc, Strasbourg, and Toulouse). Each centre used an electronic case-record form to collect data on eligible patients. The statistical analysis of those data was then conducted by the medical statistics department of the university hospital in Lille, France. Exclusion criteria were septic complications before TKA, unicompartmental knee arthroplasty, and hinged knee arthroplasty.

The study included 263 TKA procedures in 263 patients with a mean age of 61 years (range, 45-83 years). There were 122 (47%) females and 141 (53%) males. The patients had osteoarthritis secondary to a fracture (n = 66), ligament injury (n = 66), or osteotomy (n = 131). Patients with a history of fracture [START_REF] Sanders | Long-term followup of isolated ACL tears treated without ligament reconstruction[END_REF] or ligament injury [START_REF] El-Galaly | Increased risk of early and medium-term revision after post-fracture total knee arthroplasty[END_REF] were classified as having post-traumatic knee osteoarthritis. Patients with a previous knee osteotomy were included in the study, since an osteotomy is a controlled fracture; in addition, knee osteoarthritis after an osteotomy cannot be considered primary, and an osteotomy is a major event that can be likened to a knee injury [START_REF] Gaillard | Total knee arthroplasty after varus distal femoral osteotomy vs native knee: similar results in a case control study[END_REF][START_REF] Fröhlich | Navigated TKA after osteotomy versus primary navigated TKA: a matched-pair analysis[END_REF][START_REF] Ornetti | Cross cultural adaptation and validation of the French version of the Knee injury and Osteoarthritis Outcome Score (KOOS) in knee osteoarthritis patients[END_REF].

Of the 66 fractures, 42 involved the tibia and 24 the femur; 32 and 7 fractures were intra-articular in these two groups, respectively. Of the 66 ligament injuries, 22 were anterior cruciate ligament (ACL) tears managed by reconstruction, 39 were ACL tears managed non-operatively, and 5 were multiligaments injuries managed surgically. Finally, of the 131 osteotomies, 126 involved the tibia (medial opening wedge, n = 51; lateral opening wedge, n = 2; medial closing wedge, n = 2; and lateral closing wedge, n = 71) and 5 the femur (medial opening wedge, n = 1; lateral opening wedge, n = 1; and medial closing wedge, n = 3).

Mean time from knee injury or surgery to TKA was 145 months (range, 72-219). Before TKA, mean extension was -5 • [range, -50 • to 0 • ] and mean flexion was 108 • [range, 30 • to 130 • ). Varus deformity (hip-knee-ankle [HKA] angle > 177 • was noted in 152 patients and valgus deformity (HKA angle > 183 • ) in 73 patients; alignment was normal in the remaining 38 patients.

Operative technique

Standard sliding knee prostheses were implanted without retaining the posterior cruciate ligament. The implants, approach, and use of navigation varied according to standard practice at each centre. Navigation was used in 61 patients. Anterior tibial tuberosity (ATT) osteotomy was required to improve exposure via the lateral approach in 14 patients, including 8 of 66 in the fracture group, 2 of 66 in the ligament injury group, and 4 of 131 in the osteotomy group.

Assessment method

The patients were evaluated during visits before and after the TKA procedure. The Knee injury and Osteoarthritis Outcome Score (KOOS) was determined at last follow-up [START_REF] Benazzo | Knee replacement in chronic post-traumatic cases[END_REF] but not before TKA. The radiographic work-up performed before TKA and at last followup consisted of antero-posterior and lateral weight-bearing views, antero-posterior telemetry to determine the mechanical axis of the lower limb (HKA angle), and a tangential femoro-patellar view with the knee flexed at 60 • . The radiographs were used to determine the mechanical axis and to look for lucent lines suggesting loosening.

Statistical methods

The data were analyzed using SAS version 9.4 (SAS Institute Inc, Cary, NC, USA). Values of p below 0.05 were taken to indicate significant differences. Qualitative variables were described as number (%) and quantitative variables as mean ± SD and as median (interquartile range, IQR). Quantitative variables were assessed for distribution normality by applying the Shapiro-Wilk test and a graphical method. Flexion and extension ranges at baseline and last follow-up were compared using the Wilcoxon test for paired data. Survival was evaluated by plotting Kaplan-Meier curves and computing the 95% confidence intervals (95% CIs). Between-group comparisons of estimated survival were with the log-rank test. Survival was assessed to the date of revision surgery for implant exchange or last follow-up.

Results

Complications

Three patients died of conditions unrelated to the TKA. The major complications were infection (n = 12, 4.5%), skin problems (n = 8, 3%), and stiffness (n = 8, 3%). Revision surgery was required for infection in 12 (4.5%) patients and skin necrosis in 6 (3%) patients. Of the 12 patients with infection, 4 (4/263, 1.5%) required early revision within the first 3 months without implant exchange and 8 (3%) delayed revision after 3 months with implant exchange. Revision with implant exchange was performed for mechanical loosening in 7 patients and dislocation of a rotational polyethylene insert in 1 patient. Thus, implant exchange was required in 16 (6%) patients, for infection in 8 and non-infectious complications in 8. In addition, in 8 (8/263, 3%) patients, postoperative stiffness was managed by manipulation without implant revision.

Implant survival

The survival rate with implant exchange for any reason as the endpoint was 89% ± 2.8% (95% CI [0.82-0.94]) after 10 years (mean, 9.27 ± 0.12 years) (Fig. 1). Survival was not significantly different across the three groups (fracture, ligament injury, and osteotomy) (Fig. 2) (p > 0.05).

Clinical and functional outcomes

Flexion range improved by 2.5 • ± 17 • (p = 0.02) to a mean of 110 • (range, 30 • to 140 • ) and extension range by 4 • ± 7 • (p < 0.001) to a mean of -1.19 • (range, -20 • to 0 • ). The walking distance was greater than 1000 m in 175 (66%) patients and less than 500 m or limited to indoor ambulation in 27 (10%) patients. Quality of life data collected by the KOOS at last follow-up indicated little or no discomfort in 159 (60%) patients, little or no pain in 157 (60%) patients, and extreme or severe distress in 41 (16%) patients.

Radiographic outcomes

Mean HKA angle after TKA was 179 • ± -3.2 • (range, 171 • -188 • ), with no significant difference between patients managed with and without navigation (178

• ± 2 • [range, 175 • -183 • ] and 179 • ± 3 • [range, 171 • -188 • ]
, respectively; p > 0.05). Among the patients who did not require revision surgery, none had radiographic evidence of loosening at last follow-up 10 years after TKA.

Discussion

Survival to implant exchange for any reason was 89% ± 2% (95% CI [0.82-0.94]) after 10 years (mean, 9.27 ± 0.12 years) in this multicentre retrospective nationwide study of 263 patients managed with TKA for osteoarthritis secondary to trauma or surgery. The study cohort was established as performed previously for the 2010 SoFCOT symposium on 10-year TKA survival in patients with primary osteoarthritis [START_REF] Argenson | Survival analysis of total knee arthroplasty at a minimum 10 years' follow-up: a multicenter French nationwide study including 846 cases[END_REF]. Implant survival in patients with previous trauma or surgery to the knee was lower, despite a shorter mean follow-up, compared to those with primary osteoarthritis (89% [95% CI: 0.82-0.94] versus 92% [95% CI: 0.9-0.94%), confirming our working hypothesis.

Despite the larger sample size for the 2010 study (n = 846), the methodological similarities between the two studies (multicentre recruitment, multiple surgeons, and different implants across centres) allow a comparative analysis. Our population was younger compared to the 2010 study (61 versus 71 years) and to published epidemiological studies of TKA (mean age, 70 years) [START_REF] Carr | Knee replacement[END_REF].

The choice of the three aetiological groups (fracture, ligament injury, and osteotomy) may appear criticisable but is fully consistent with the objective of the 2016 SoFCOT symposium. Osteotomy carries the same risks and requires the same precautions as previous trauma to the knee (history of surgery with a previous approach and possible ligament damage) [START_REF] Fröhlich | Navigated TKA after osteotomy versus primary navigated TKA: a matched-pair analysis[END_REF][START_REF] Ornetti | Cross cultural adaptation and validation of the French version of the Knee injury and Osteoarthritis Outcome Score (KOOS) in knee osteoarthritis patients[END_REF][START_REF] Benazzo | Knee replacement in chronic post-traumatic cases[END_REF].

Specific complications were more common in our study compared to the population with primary knee osteoarthritis studied in 2010. Thus, the infection rate was higher (4.5% versus 1.8%), skin problems were not infrequent (3% versus none reported), and stiffness was more common (3% versus 1%). These complications are usually seen in studies of TKA for knee osteoarthritis after trauma [START_REF] Benazzo | Knee replacement in chronic post-traumatic cases[END_REF] or osteotomy. Thus, in a study by Efe et al. [START_REF] Efe | TKA following high tibial osteotomy versus primary TKA -a matched pair analysis[END_REF] of 6-year outcomes in 41 TKAs after high tibial osteotomy and 41 primary TKAs, the active flexion range was nearly 10 • greater in the primary TKA group and the revision rate was twice as high in the osteotomy group. Ehlinger et al. [START_REF] Ehlinger | Total knee arthroplasty after opening -versus closing -wedge high tibial osteotomy. A 135-case series with minimum 5-year follow-up[END_REF] recorded a 12.3% rate of early complications in a study of 135 patients comparing outcomes of any type of TKA after opening-versus closing-wedge high tibial osteotomy. In a study by Lunebourg et al. [START_REF] Lunebourg | Lower function, quality of life, and survival rate after total knee arthroplasty for posttraumatic arthritis than for primary arthritis[END_REF] of outcomes after post-fracture TKA (n = 33) versus primary TKA (n = 407) assessed after at least 5 years, the post-fracture group had a lower 10-year survival of 79% compared to 99% in the primary group. A comparison of TKA after ACL reconstruction versus primary TKA conducted by Magnussen et al. [START_REF] Magnussen | Total knee arthroplasty for secondary osteoarthritis following ACL reconstruction: a matched-pair comparative study of intra-operative and early postoperative complications[END_REF] showed a higher rate of stiffness requiring manipulation under general anaesthesia in the ACL group.

Our results confirm the improvement in flexion range achieved after TKA, in keeping with the data from the 2010 symposium (flexion increase by 7 • to a mean of 112 • ± 12 • (range, 25 • to 125 • ) [START_REF] Argenson | Survival analysis of total knee arthroplasty at a minimum 10 years' follow-up: a multicenter French nationwide study including 846 cases[END_REF]. In 1607 primary TKAs studied by Pasquier et al. [START_REF] Pasquier | Influence of preoperative factors on the gain in flexion after total knee arthroplasty[END_REF], mean flexion increase after 2 years was 8.4 • . A study by Massin et al. [START_REF] Massin | Total knee replacement in post-traumatic arthritic knees with limitation of flexion[END_REF] of 40 TKAs for post-traumatic osteoarthritis with flexion limitation to 90 • or less showed a large mean flexion gain of 26.7 • ± 20 • . However, among our patients only 60% reported little or no pain, an outcome that makes a major contribution to patient satisfaction [START_REF] Lange | What do patients expect from total knee arthroplasty? A Delphi consensus study on patient treatment goals[END_REF][START_REF] Jiang | Predictors of patient-reported pain and functional outcomes over 10 years after primary total knee arthroplasty: a prospective cohort study[END_REF].

The treatment goal in our patients was to obtain a neutral or near-neutral mechanical axis. The use of navigation did not significantly change the proportion of patients achieving this goal in our population. Other studies, in contrast, found benefits from navigation in complex cases [START_REF] Huang | Total knee arthroplasty in patients with Ranawat type-II valgus arthritic knee with a marked coronal femoral bowing deformity: comparison between computer-assisted surgery and intra-articular resection[END_REF][START_REF] Saragaglia | Computer navigation for revision of unicompartmental knee replacements to total knee replacements: the results of a case-control study of forty-six knees comparing computer navigated and conventional surgery[END_REF][START_REF] Cip | Encouraging treatment algorithm for computer-assisted navigated total knee arthroplasty (TKA): a retrospective cohort analysis[END_REF]. The difference in navigation systems across centres in our study may explain the absence of significant benefits. Consequently, our results should not be construed as evidence that navigation systems are unnecessary in complex cases [START_REF] Desseaux | Radiographic outcomes in the coronal plane with Iassist TM versus optical navigation for total knee arthroplasty: a preliminary case-control study[END_REF][START_REF] Yang | Robotic total knee arthroplasty with a cruciate-retaining implant: a 10-year follow-up study[END_REF]. In addition, several studies indicate that maintaining the original knee malalignment may provide better kinematics compared to restoring normal alignment and may, therefore, result in better patient satisfaction [START_REF] Parratte | Effect of postoperative mechanical axis alignment on the fifteen-year survival of modern, cemented total knee replacements[END_REF][START_REF] Matsumoto | Radiological and clinical comparison of kinematically versus mechanically aligned total knee arthroplasty[END_REF][START_REF] Almaawi | The impact of mechanical and restricted kinematic alignment on knee anatomy in total knee arthroplasty[END_REF][START_REF] Rames | No impact of undercorrection and joint line obliquity on clinical outcomes of total knee arthroplasty for the varus knee[END_REF].

The limitations of this study include the diversity of the previous knee conditions (fracture, ligament injury, and osteotomy), differences in practices across centres, and possible bias due to data collection by the surgeons who performed the TKAs. Nevertheless, the use of an electronic data collection form limited the amount of missing data, standardized the collection of the data, and minimized the risk of collection bias. Our multicentre recruitment provided a major advantage over single-centre studies by producing a far larger sample size.

Conclusion

In this study, survival was lower (89%) after TKA for osteoarthritis secondary to trauma or surgery, compared to TKA for primary osteoarthritis [START_REF] Argenson | Survival analysis of total knee arthroplasty at a minimum 10 years' follow-up: a multicenter French nationwide study including 846 cases[END_REF]. Three complications deserve special attention: infection, skin problems, and stiffness. Although TKA improved knee range of motion, only 60% of patients were satisfied with the procedure.

Disclosure of interest

SPu is an educational consultant for Tornier-Corin; JNA a consultant for Zimmer-Biomet; PBo a consultant for Stryker and Depuy-Synthes; ME a consultant for Depuy-Synthes, Lepine, and NewClip; PV a consultant for Medacta; SLe a consultant for Ceraver; SLu a consultant for Medacta and Smith & Nephew and a provider of institutional research support for Amplitude and Corin-Tornier; SP a consultant for Zimmer-Biomet, Arthrex, Newclip, Graftys, and Adler Ortho, and MC a consultant for Ceraver.

PBi declares that he has no competing interest.

Fig. 1 .

 1 Fig. 1. Overall survival of TKA after trauma or surgery, with the 95% confidence interval.

Fig. 2 .

 2 Fig. 2. Survival of TKA after trauma or surgery according to the previous condition: fracture (in red), ligament injury (in blue), or osteotomy (in green).

  '-,-----~----~---~----~----~-----.-'

Acknowledgements

We thank Evamed for the data collection and Henri Migaud for assistance in writing the study report.


Philippe Clavert
email: philippe.clavert@chru-strasbourg.fr

Florence Aim

Nicolas Bonnevialle

Marine Arboucalot

Matthieu Ehlinger

Thomas Bauer

Biomechanical properties of transosseous bony Bankart repair in a cadaver model

Keywords:

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Introduction

Glenohumeral dislocation most often occurs when the arm is cocked, thus abducted and externally rotated [START_REF] Branch | The role of glenohumeral capsular ligaments in internal and external rotation of the humerus[END_REF][START_REF] Matsen | The shoulder: a balance of mobility and stability[END_REF][START_REF] Moseley | The anterior capsular mechanism in recurent anterior dislocation of the shoulder[END_REF][START_REF] Ovesen | Stability of the shoulder joint: cadaver study of stabilizing structures[END_REF][START_REF] Terry | The stabilizing function of passive shoulder restraints[END_REF][START_REF] Bankart | The pathology and treatment of recurrent dislocation of the shoulder joint[END_REF][START_REF] Perry | Anatomy and biomechanics of the shoulder in throwing, swimming, gymnastics and tennis[END_REF]. This results in avulsion of anterior capsule/labrum structures on the glenoid rim [START_REF] Bankart | The pathology and treatment of recurrent dislocation of the shoulder joint[END_REF]; the bony structures may also be damaged. Under certain conditions -injury mechanism, patient age, osteoporosis -the energy of the trauma can cause an intra-articular fracture of the anteroinferior portion of the glenoid fossa, type IA in the Ideberg classification [START_REF] Ideberg | Epidemiology of scapular fractures Incidence and classification of 338 fractures[END_REF][START_REF] Ideberg | Unusual glenoid fractures: a report on 92 cases[END_REF][START_REF] Ideberg | Fractures of the scapula involving the glenoid fossa[END_REF]. These fractures are generally treated conservatively. But in cases with a large fracture fragment and significant displacement (more than 20% of articular surface involved and more than 10 mm displacement [START_REF] Palma | Fractures and fracture-dislocations of the shoulder girdle[END_REF]), the natural history includes recurrence of the instability and osteoarthritis [START_REF] Ideberg | Unusual glenoid fractures: a report on 92 cases[END_REF][START_REF] Palma | Fractures and fracture-dislocations of the shoulder girdle[END_REF][START_REF] Sugaya | Glenoid rim morphology in recurrent anterior glenohumeral instability[END_REF]. Until recently, surgical fixation was recommended [START_REF] Mayo | Displaced fractures of the glenoid fossa. Results of open reduction and internal fixation[END_REF][START_REF] Schandelmaier | Fractures of the glenoid treated by operation. A 5-to 23-year follow-up of 22 cases[END_REF][START_REF] Sinha | Fixation of fractures of the glenoid rim[END_REF][START_REF] Kavanagh | Open reduction and internal fixation of displaced intra-articular fractures of the glenoid fossa[END_REF]. However, the need to detach and then suture the subscapularis tendon contributed to the development of arthroscopic fixation of this type of fracture with suture anchors. This technique has good clinical and radiological outcomes [START_REF] Sugaya | Arthroscopic repair of glenoid fractures using suture anchors[END_REF][START_REF] Bauer | Arthroscopic treatment of glenoid fractures[END_REF][START_REF] Tauber | Arthroscopic screw fixation of large anterior glenoid fractures[END_REF][START_REF] Gigante | Arthroscopy-assisted reduction and percutaneous fixation of a multiple glenoid fracture[END_REF][START_REF] Cameron | Arthroscopic reduction and internal fixation of an anterior glenoid fracture[END_REF][START_REF] Porcellini | Arthroscopic approach to acute bony Bankart lesion[END_REF]. The advantages of these arthroscopic techniques are that they provide better reduction of the intra-articular fracture, limit the tissue dissection and reduce the morbidity [START_REF] Marsland | Arthroscopically assisted fixation of glenoid fractures: a cadaver study to show potential applications of percutaneous screw insertion and anatomic risks[END_REF]. However, there are no studies on the biomechanics of these arthroscopic techniques, which are needed to evaluate the risk of secondary displacement and to support postoperative recommendations.

The primary objective of our study was to define the primary mechanical properties of transosseous repair of an Ideberg IA fracture relative to intact shoulders (control condition). The secondary objective was to determine the contribution of supplemental anteroposterior screw fixation of the bone fragment. We hypothesized that transosseous repair is sufficient to effectively stabilize an anterior glenoid rim fracture (Ideberg IA).

Materials and methods

We used an anterior glenohumeral instability model that has been described previously [START_REF] Clavert | Biomechanics of open Bankart and coracoid abutment procedures in a human cadaveric shoulder model[END_REF].

Dissection

Fifteen fresh cadaver shoulders from bodies donated to the Anatomy Institute of the Strasbourg Faculty of Medicine were used for the study (9 male, 6 female). The mean age of the subjects was 76 years (range 69-82). Before starting, each shoulder underwent X-rays with the humerus in the frontal plane to calculate the Tingart index used to balance out the groups based on the degree of osteoporosis [START_REF] Tingart | The cortical thickness of the proximal humeral diaphysis predicts bone mineral density of the proximal humerus[END_REF]. Arthroscopy was performed by the posterior route to eliminate all shoulders with osteoarthritis or damage to anterior capsule and labrum structures. Next, 5 specimens were randomly placed in the control group and 10 in the reconstruction group.

All of the tissues were dissected to leave only 15 cm of the humerus, the glenohumeral joint capsule and the rotator cuff tendons. Two traction sutures were placed in the subscapularis tendon (Ethibond No. 6, Ethicon, Somerville, NJ, USA). In the reconstruction group, a fracture of the anteroinferior portion of the glenoid fossa (between 3 and 6 o'clock) involving nearly 30% of the surface area was created with an osteotome under fluoroscopy control. The continuity of the capsule/periosteum was preserved as was the integrity of the labrum. First, transosseous repair was done by placing interrupted sutures on two or three 3.5-mm diameter absorbable PLLA suture anchors (Panalok, Mitek, Norwood, MA) depending on the length of the osteotomy (which varied based on the subject's size). All the repairs were performed directly, leaving the subscapularis tendon reflected. After the biomechanical testing was completed, the same shoulder was re-used. A new repair was done using the same protocol but with a larger diameter suture anchor, inserted in the same hole as the first anchor, in the cranial and caudal segments of the fracture. A 3.5-mm diameter cannulated screw was added to the suture repair, perpendicular to the fracture line, and in the middle of it, to provide additional bicortical fixation of the fracture fragment.

Biomechanical testing

Biomechanical testing was carried out on a materials testing machine (Instron 8500 PLUS, Instron Corp., High Wycombe, Buckinghamshire, United Kingdom). The shoulders were positioned in a jig that allowed 80 • abduction on the scapular plane and 90 • external rotation of the humerus [START_REF] Johnston | The movement of the shoulder joint. Aplea for the use for 'the plan of the scapula' as the reference for movement occuring at the humero-scapula joint[END_REF] to simulate the arm-cock position. The scapula was secured between two plates and then a K-wire was inserted through the humerus to maintain its position (Fig. 1). A 20 N pre-load was applied to the subscapularis tendon using the two, previously applied traction sutures. A 10 N pre-load was applied to the construct by the actuator of the testing machine on the posterior side of the humeral head. Only at this point was the final position of the humerus set by locking the K-wire. The humeral head was then translated anteriorly at 160 mm/s. The load and displacement were recorded. The 10 specimens that underwent transosseous repair were tested, then the same 10 specimens were re-tested with the screw fixation added to the transosseous repair.

We analyzed the mode of failure, site of failure, load at failure and stiffness, which corresponded to the slope of the linear portion of the load-displacement curve. The specimens were kept moist throughout the experiments.

Statistical analysis

A one-way ANOVA was used to compare the two reconstruction techniques to the control group. The results of the consecutive repairs on the same shoulder were compared using the nonparametric Wilcoxon test. The alpha level was 5%. The software XLstat 2007 (Addinsoft, Paris, France) was used.

Results

Fragment area

All the fractures involved more than one-third of the inferior articular surface, calculated as described by Sugaya et al. [START_REF] Sugaya | Glenoid rim morphology in recurrent anterior glenohumeral instability[END_REF].

Type of failure

In all specimens in the control group, the failure occurred at the anterior capsule/labrum area (3 to 6 o'clock). There were no fractures of the anterior rim of the glenoid fossa or capsular failure at the humeral neck.

In the transosseous repair group, none of the suture anchor points failed. In every specimen, the failure occurred with breaking of the sutures themselves and displacement of the fragment (Fig. 2).

In the transosseous repair + screw fixation group, the capsule failed in all specimens, with fragmentation of the screwed anterior glenoid rim.

Mechanical properties

The load to failure and stiffness are summarized in Table 1. The mechanical strength (p = 0.001) and stiffness (p = 0.001) were significantly less in the two reconstruction groups than in the control group. Adding a screw significantly increased the load to failure (p = 0.02) and the stiffness (p = 0.001) relative to the group with transosseous repair only.

Discussion

The results for the control group (load to failure of 457 N) are comparable to published values [START_REF] Clavert | Biomechanics of open Bankart and coracoid abutment procedures in a human cadaveric shoulder model[END_REF], thus making for a valid comparison with the reconstruction groups. This study clearly shows that arthroscopic transosseous repair for Ideberg IA glenoid fracture restores the anatomy of the glenoid fossa within the scapula but does not restore the primary mechanical properties of the native glenoid. Adding an anteroposterior screw significantly improves the mechanical stability of the construct, both in terms of the load to failure (p = 0.02) and the stiffness (p = 0.001). Note that in the transosseous repair group, the load at failure and stiffness were much lower than in the other two groups. This can be explained by the fact that the suture anchor + screw construct is very rigid once the screws are inserted, thus the hardware is being tested more than the construct itself. This study was not designed to determine the minimum size of fragment needed to allow a screw to be added to the suture anchor construct.

Since only one-third of the humeral head makes contact with the glenoid's articular surface, this joint is only partially constrained by its bony relationships. However, lesions in the inferior portion of the glenoid make the glenohumeral joint highly unstable in cases with a displaced intra-articular fracture. Moreover, anterior ligament structures also contribute to the joint's stability [START_REF] Terry | The stabilizing function of passive shoulder restraints[END_REF][START_REF] Warner | Static capsuloligamentous restraints to superior-inferior translation of the glenohumeral joint[END_REF]. Thus it seems necessary to not only reduce the articular fragment, but also to secure the anterior capsule and labrum in their anatomical position in order to control the bone and ligament structures. This is likely the reason why arthroscopy improves the quality and stability of repairs, as it allows associated lesions such as partial or complete rotator cuff tears and/or superior or posterior extension of labrum tears to be repaired (up to 78.3% in the Scheibel study [START_REF] Scheibel | Arthroscopic reduction and fixation of large solitary and multifragmented anterior glenoid rim fractures[END_REF]) and better fixation of ligament structures.

Cameron [START_REF] Cameron | Arthroscopic reduction and internal fixation of an anterior glenoid fracture[END_REF] was the first to propose performing arthroscopic fixation of intra-articular glenoid fractures using a 3.5-mm diameter cannulated screw. Later on, it was shown that transosseous fixation stabilizes the fragments well enough for the fracture to heal in an anatomical position [START_REF] Sugaya | Arthroscopic repair of glenoid fractures using suture anchors[END_REF][START_REF] Bauer | Arthroscopic treatment of glenoid fractures[END_REF][START_REF] Tauber | Arthroscopic screw fixation of large anterior glenoid fractures[END_REF][START_REF] Gigante | Arthroscopy-assisted reduction and percutaneous fixation of a multiple glenoid fracture[END_REF][START_REF] Cameron | Arthroscopic reduction and internal fixation of an anterior glenoid fracture[END_REF][START_REF] Porcellini | Arthroscopic approach to acute bony Bankart lesion[END_REF]. However, all of these studies were done with fragments involving less than 20% of the glenoid surface. Scheibel et al. [START_REF] Warner | Static capsuloligamentous restraints to superior-inferior translation of the glenohumeral joint[END_REF] proposed using an absorbable screw to secure the bone fragment. With a 100% union rate, these authors suggested that along with better stability, adding the screw compresses the fracture site more and contributes to its healing. The alternative to using a screw is performing a double-row repair [START_REF] Millett | The "bony Bankart bridge" procedure: a new arthroscopic technique for reduction and internal fixation of a bony Bankart lesion[END_REF]. In a cadaver study, it was shown that this fixation technique provides greater stability than suture anchor fixation on the anterior rim of the glenoid (single-row repair performed typically).

Study limitations

As with any cadaver study, the number of specimens was limited to the minimum needed for use of non-parametric statistical tests. Moreover, this study was done with donors older than the age of patients who typically suffer this type of injury. It can only measure the primary mechanical strength of the construct at T0 and does not take into account remodeling and healing that occurs in vivo. We did not test different types of sutures, in particular newer non-absorbable sutures. Also, the amount of plastic deformation in the joint capsule cannot be determined in vivo, thus cannot be reproduced in a laboratory setting. Lastly, the dislocation mechanism, by application of an anteroposterior translation load does not always reflect reality and other mechanisms come into play in clinical practice. For this reason, this study did not evaluate the lesions associated with a fracture/dislocation and their impact on the stability of the construct.

Conclusions

Arthroscopic transosseous repair of Ideberg IA intra-articular glenoid fractures appears to correctly stabilize the anteroinferior fragment. Adding screw fixation significantly improves the strength of the construct. However, these constructs do not fully restore the primary mechanical properties of the native glenoid. Thus we feel it is necessary to immobilize the patients' shoulder postoperatively.

Disclosure of interest

PhC: consultant and product development for Wright-Tornier, Associate editor for OTSR.

NB: consultant for Smith & Nephew, Wright-Tornier, Stryker; royalties from SBM. ME: consultant and product development for DePuy-Synthes, Lépine, Symbios, Newclip, Amplitude ® , Associate editor for the SOFCOT instructional lectures. FA declares that he has no competing interest. TB: consultant for Arthrex ® , Zimmer/Biomet ® .

Fig. 1 .

 1 Fig. 1. Test jig with the arm placed in the cocked position through the scapulohumeral joint. Traction sutures are placed in the subscapularis (SC) tendon.

Fig. 2 .

 2 Fig. 2. Failure of the sutures with displacement of the bone fragment, which remains attached to the capsule.

Table 1

 1 Mean values (SD) of the load to failure and stiffness for the control group and two fracture fixation techniques.

		Load to failure (N)	Stiffness
			(N/mm)
	Control	457 (187.1) a	26.2 (7.5) a
	Transosseous repair	277 (48.7) a	14.6 (3.2) a
	Transosseous repair + screw fixation	325 (129.4) a	24.6 (8.4) a

a Significantly different (p-values in the text).

Funding

None.

Author contributions

All the authors contributed to the study design, validation and writing of the manuscript.