SHOULDER AND ELBOW. M. Bouliane, D. Saliken, L. A. Beaupre, A. Silveira, M. K. Saraswat, D. M. Sheps

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1 M. Bouliane, D. Saliken, L. A. Beaupre, A. Silveira, M. K. Saraswat, D. M. Sheps From University of Alberta, Edmonton, Alberta, Canada M. Bouliane, MD, FRCS(C), Orthopaedic Surgeon D. Saliken, MD, Orthopaedic Surgery Resident D. M. Sheps, MD, MBA, FRCS(C), Orthopaedic Surgeon Department of Surgery, University of Alberta, CSB, Street, Edmonton, Alberta, T6G 2B7, Canada. L. A. Beaupre, PT, PhD, Associate Professor Department of Physical Therapy, University of Alberta, 2-50 Corbett Hall, Edmonton, Alberta, T6G 2G4, Canada. A. Silveira, PT, MScRS, Research Associate M. K. Saraswat, MHS, Research Associate Alberta Health Services, CSB, Street, Edmonton, Alberta, T6G 2B7, Canada. Correspondence should be sent to Dr L. A. Beaupre; The British Editorial Society of Bone & Joint Surgery doi: / x.96b $2.00 Bone Joint J 2014;96-B: Received 16 May 2014; Accepted after revision 8 August 2014 SHOULDER AND ELBOW Evaluation of the Instability Severity Index Score and the Western Ontario Shoulder Instability Index as predictors of failure following arthroscopic Bankart repair In this study we evaluated whether the Instability Severity Index Score (ISIS) and the Western Ontario Shoulder Instability Index (WOSI) could detect those patients at risk of failure following arthroscopic Bankart repair. Between April 2008 and June 2010, the ISIS and WOSI were recorded pre-operatively in 110 patients (87 male, 79%) with a mean age of 25.1 years (16 to 61) who underwent this procedure for recurrent anterior glenohumeral instability. A telephone interview was performed two-years post-operatively to determine whether patients had experienced a recurrent dislocation and whether they had returned to preinjury activity levels. In all, six (5%) patients had an ISIS > 6 points (0 to 9). Of 100 (91%) patients available two years post-operatively, six (6%) had a recurrent dislocation, and 28 (28%) did not return to pre-injury activity. No patient who dislocated had an ISIS > 6 (p = 1.0). There was no difference in the mean pre-operative WOSI in those who had a redislocation and those who did not (p = 0.99). The pre-operative WOSI was significantly lower (p = 0.02) in those who did not return to pre-injury activity, whereas the ISIS was not associated with return to pre-injury activity (p = 0.13). In conclusion, neither the pre-operative ISIS nor WOSI predicted recurrent dislocation within two years of arthroscopic Bankart repair. Patients with a lower pre-operative WOSI were less likely to return to pre-injury activity. Cite this article: Bone Joint J 2014; 96-B: Recurrent anterior glenohumeral instability is common and frequently requires surgical treatment. 1,2 The available operations include arthroscopic and open approaches, with stabilisation achieved by repair of the soft tissues, bony augmentation or a combination of the two. Using modern suture anchor techniques, failure rates of arthroscopic soft-tissue stabilisation range from 4% to 17%. 3-5 This failure rate is influenced by several factors relating to the patient including age, contact-sport activity, glenohumeral bone loss and joint laxity, as well as surgical factors such as the number of anchors used. 6-9 Significant glenoid bone loss often warrants an alternative procedure, such as a Latarjet procedure, and significant humeral bone loss in isolation may be an indication for an intervention such as a Remplissage 10 in combination with a Bankart repair. 2 It is therefore important to carefully consider the best surgical approach for each patient. The Instability Severity Index Score (ISIS) is a ten-point scale intended to guide surgical decision making (Table I). 11,12 It uses age, activity level, joint laxity (defined as external rotation > 85º or difference on the Gagey hyperabduction test 13 of 20º) and glenohumeral bone loss, to determine the risk of failure of an arthroscopic Bankart repair. In a study including 131 patients, those scoring > 6 points had a reported risk of failure of 76%. 11 Since the original publication, a score of > 3 points has been proposed as being associated with an increased risk of failure but this has not been as commonly studied. 14 At the time of the initiation of our current study, an ISIS of six points was the accepted threshold, based on the original publication, 11 and so was used as the cut-off for the purposes of evaluating the ISIS as a predictor of failure. Although good reliability has been reported for the ISIS, 12 it has not been evaluated in a prospective manner. The Western Ontario Shoulder Instability Index (WOSI) is a reliable and valid diseasespecific patient-reported quality-of-life outcome measure which assesses the impact of glenohumeral instability. 15 It is a visual analogue score made up of 21 questions subdivided into four domains: physical symptoms, sports/recreation/work, lifestyle and emotions THE BONE & JOINT JOURNAL

2 EVALUATION OF THE INSTABILITY SEVERITY INDEX SCORE AND THE WESTERN ONTARIO SHOULDER INSTABILITY INDEX 1689 Table I. Instability Severity Index Score (ISIS) Prognostic factors Points Age at surgery (years) < 20 2 > 20 0 Degree of sport participation (pre-operative) Competitive 2 Recreational or none 0 Types of sports (pre-operative) Contact or forced overhead 1 Other 0 Shoulder hyperlaxity Shoulder hyperlaxity 1 Normal laxity 0 Hill Sachs lesion on anteroposterior radiograph Visible in external rotation 2 Not visible in external rotation 0 Glenoid loss of contour on anteroposterior radiograph Loss of contour 2 No lesion 0 Total 10 A higher score indicates a better quality of life. This score has never been evaluated as a prognostic measure for patients undergoing surgery for glenohumeral instability Our study was undertaken in patients with recurrent post-traumatic anterior instability undergoing an arthroscopic Bankart repair at a single centre. The primary objective was to determine whether those with a pre-operative ISIS > 6 points had a higher rate of failure 24 months postoperatively compared to those who had a pre-operative ISIS of 6. A secondary objective was to determine whether patients who had a failed outcome within 24 months postoperatively had a worse pre-operative WOSI score than those who did not fail. A third objective was to determine whether patients with a pre-operative ISIS of > 6 points who underwent an arthroscopic Bankart repair had a lower pre-operative WOSI than those who had a pre-operative ISIS of 6 points. We hypothesised that those with a higher pre-operative ISIS and worse pre-operative WOSI would have higher rates of surgical and functional failure within 24 months of surgery, and that the pre-operative WOSI would be worse in those with a higher pre-operative ISIS. Patients and Methods Between April 2008 and June 2010, 110 patients (87 men and 23 women) with a mean age of 25.2 years (16 to 61) with recurrent post-traumatic anterior glenohumeral instability were enrolled in a prospective longitudinal study evaluating recurrent dislocation and functional failure following arthroscopic Bankart repair. The inclusion criterion was adult patients with recurrent anterior instability who were scheduled for this procedure. Those with humeral avulsion of the glenohumeral ligament, seizures, extreme combined glenohumeral bone loss with inadequate labral tissue for repair, advanced glenohumeral osteoarthritis (OA) (greater than Outerbridge grade 16 three), prior surgery for chronic instability of the shoulder, and/or inability to commit to the proposed rehabilitation were excluded. Baseline pre-operative details included the ISIS, completed by the operating surgeon, WOSI, age and gender. All patients underwent a standard arthroscopic Bankart repair from one of four fellowship-trained shoulder surgeons. Patients were positioned in the beach-chair position under general anaesthesia. A 4 mm diameter arthroscope was inserted through a standard posterior portal and a diagnostic arthroscopy was performed. An anterior working portal was created superior to the subscapularis tendon and lateral to the conjoined tendon. The anterior labrum was freed and the neck of the glenoid was decorticated. A standard repair of the capsulolabral complex was performed using a median of 4 (IQR 3 to 5) suture anchors. The data that were collected intra-operatively included the presence or absence of a Hill Sachs 17 and/or bony Bankart lesion. 18 Post-operatively, patients followed a standard rehabilitation protocol with a return to sport between 12 and 24 weeks after surgery, based on strength and range of movement. The study coordinator, who had no part in the treatment, asked two questions by telephone, two years postoperatively to determine the outcome. Patients were asked whether they had experienced a re-dislocation or significant subluxation requiring medical treatment, which was considered to be a surgical failure, and whether they had returned to pre-injury activity. Failure to return to preinjury activity was considered a functional failure. The primary outcome measure was failure, either surgical or functional, of the arthroscopic Bankart repair. Statistical analysis. Assuming a post-operative rate of failure of 10%, using α = 0.05 and power of 80%, a sample size of 100 patients was required. The primary analysis was the relationship between surgical and functional failure VOL. 96-B, No. 12, DECEMBER 2014

3 1690 M. BOULIANE, D. SALIKEN, L. A. BEAUPRE, A. SILVEIRA, M. K. SARASWAT, D. M. SHEPS Table II. Baseline characteristics Number Total patients 110 Mean age (yrs) (range) 25.2 (16 to 61) Male gender (%) 87 (79) Mean WOSI score (%) (range) 42.5 (8.3 to 84.0) ISIS score > 6 (%) 6 (5) ISIS, Instability Severity Index Score; WOSI, Western Ontario Shoulder Instability Index Fig. 1a Fig. 1b Fig. 1c A patient with no apparent glenohumeral bone loss on plain radiography but a large Hill Sachs lesion and glenoid bone loss on CT: a) True anteroposterior radiograph with no loss in sclerotic glenoid contour; b) axial CT scan showing Hill Sachs lesion; c) 3D CT reconstruction enface view showing glenoid bone loss. Table III. Surgical failure within 24 months Dislocation n = 6 No dislocation n = 94 p-value Mean age (yrs) (range) 21.3 (16 to 27) 25.5 (16 to 61) 0.26 * Number of men (%) 6 (100) 71 (76) 0.33 ISIS score 1.0 Number with ISIS > 6 (%) 0 (0) 5 (5) Number with ISIS 6 (%) 6 (6) 89 (95) Baseline WOSI score Mean WOSI score (%) (range) 42.1 (18.7 to 58.6) 42.1 (8.3 to 83.5) 0.99 * ISIS, Instability Severity Index Score; WOSI, Western Ontario Shoulder Instability Index * Independent t-test Chi-squared test and the ISIS (ISIS 6; ISIS > 6) using the chi-squared test. The secondary analysis was the relationship between surgical and functional failure and the WOSI using an independent t-test. In addition, the relationship between the ISIS (ISIS 6; ISIS > 6) and pre-operative WOSI was also evaluated using an independent t-test. Tests of normality were performed prior to this analysis. All analyses were performed with Predictive Analytics Software (PASW; SPSS Inc., Chicago, Illinois) and significance was set at p < Results Of the 110 patients with an ISIS completed pre-operatively, only six (5%) had a score > 6. Although so few patients had a high score, of the 100 patients available for follow-up, 34 (34%) participated in competitive sports, 49 (49%) participated in overhead or contact sports and 33 (33%) had joint laxity. Of the 110 patients recruited to the study, the pre-operative plain radiographs revealed that 22 (20%) had a Hill Sachs lesion and 19 (17%) showed loss of glenoid contour (Table II). THE BONE & JOINT JOURNAL

4 EVALUATION OF THE INSTABILITY SEVERITY INDEX SCORE AND THE WESTERN ONTARIO SHOULDER INSTABILITY INDEX 1691 Table IV. Functional failure within 24 months Did not return to activity n = 28 Returned to activity n = 72 p-value Mean age (yrs) (range) 21.8 (16 to 38) 26.6 (15 to 61) * Number of men (%) 21 (75) 56 (78) 0.80 ISIS score 0.13 Number with ISIS > 6 (%) 3 (60) 2 (40) Number with ISIS 6 (%) 25 (26) 70 (74) Baseline WOSI score Mean WOSI score (%) (range) 36.1 (8.3 to 71.0) 44.4 (9.5 to 83.5) 0.02 * ISIS, Instability Severity Index Score; WOSI, Western Ontario Shoulder Instability Index * Independentt-test Chi-squared test Of the 100 (91%) patients who were assessed 24-months post-operatively for the determination of failure, six (6%) had surgical failure, with two requiring further surgery. One of these had a Hill Sachs lesion with no loss of glenoid contour, but the pre-operative CT had shown significant glenoid bone loss (Fig. 1). Although only a few patients had surgical failure, an additional 28 (28%) had functional failure. There were no significant differences in age, gender distribution, mean ISIS or pre-operative WOSI between those who had surgical failure and those who did not (Table III). In contrast, those who had functional failure were younger and more likely to have had a worse pre-operative baseline WOSI (Table IV). Of the six patients with an ISIS > 6 at the time of entry into the study, five completed the 24-month follow-up. Two (40%) of these five patients with ISIS > 6 returned to pre-injury activity, compared with 70 (74%) of the 95 patients with an ISIS 6. However, this difference did not reach statistical significance (p = 0.13). No significant differences were seen between the pre-operative WOSI scores of patients with an ISIS > 6 (mean 42 (8.26 to 84.04)) or 6 (mean 54 (8.26 to 84.04)) (p = 0.13). Discussion In the 100 patients who were assessed for the outcome of arthroscopic shoulder stabilisation, the rates of surgical and functional failure were 6% and 28%, respectively. We were unable to predict surgical failure at two years followup using the ISIS or the pre-operative WOSI. Although these did not predict surgical failure, the mean WOSI was lower in patients who did not return to pre-injury activity, and 60% of those who had an ISIS > 6 did not return to their pre-injury activity levels. The pre-operative WOSI did not distinguish between those who had a higher or a lower ISIS, but the small number of patients with a score of > 6 may have influenced this finding. Many studies have evaluated surgical failure as the primary outcome measure following surgery to the shoulder for instability. Another relevant outcome measure is the inability to return to pre-injury activity, reflecting functional failure. In this study, the rate of functional failure was high compared with the rate of surgical failure (28% vs 6%). Cho et al 19 prospectively studied 29 athletes who underwent arthroscopic Bankart repair and found that 34.5% were unable to return to their pre-injury level of sports activity. Garofalo et al 20 followed 20 patients treated in the same way and found that 20% were unable to return to sport at mean follow-up of 43 months. Ide et al 5 found an inability to return to the pre-injury level of sports activity in 20% of 55 patients followed prospectively for 42 months. However, these studies did not include a pre-operative score to predict functional failure, as was done in this study with the WOSI and ISIS. Many patients who opt for surgical management of glenohumeral instability do so in the hope of regaining their pre-injury functional status. Pre-operative HRQL questionnaires such as the WOSI may help the surgeon counsel the patient appropriately, align expectations, and could potentially affect surgical decision making if the patient wishes to return to their pre-injury level in a sport that involves either contact or overhead activity. In this study, the pre-operative WOSI was significantly lower in patients who had functional failure (p = 0.02). This index is a valid and reliable patient-generated outcome measure for glenohumeral instability. 15 Van der Linde et al 9 evaluated the long-term results following arthroscopic Bankart repair and noted that although the mean postoperative WOSI was good overall, it was significantly worse in patients who re-dislocated than in those who did not (p = 0.05). This is the first study to use this index as a pre-operative predictor of outcome. Although it was not possible using this score to detect those who would fail an arthroscopic repair two years post-operatively (surgical failure) (p = 0.99), it did identify those with functional failure (p = 0.02). The patients with significantly lower preoperative WOSI scores also had lower post-operative scores, and did not do as well irrespective of the pathology identified. Although the differences in the mean preoperative WOSI between those who returned to pre-injury activity and those who did not (44% and 36%, respectively) reached statistical significance (p = 0.02), this was less than the previously reported minimal clinically important difference for the WOSI score of 10%. 21 Therefore, these results should be interpreted with caution. The ISIS scores followed a similar pattern in detecting those who did not return to pre-injury activity, but did not attain statistical significance (p = 1.0). However, our cohort included only six patients with an ISIS > 6. Similar findings VOL. 96-B, No. 12, DECEMBER 2014

5 1692 M. BOULIANE, D. SALIKEN, L. A. BEAUPRE, A. SILVEIRA, M. K. SARASWAT, D. M. SHEPS were also reported in another cohort of 47 patients, so this may not be unusual in those who are considered for an arthroscopic Bankart repair. 22 The ISIS evaluates factors that pre-dispose patients to failure of an arthroscopic Bankart repair, based on the outcomes in the literature. 4 Whereas the first three categories (patient age, level/type of sport, and joint laxity) are easy to determine, the last two components (glenoid and humeral bone loss) are dependent on individual radiological assessment. Determining whether glenohumeral bone loss is present on a single anteroposterior (AP) radiograph may be difficult owing to intra- and inter-rater reliability. Using an alternative imaging modality, such as 3D imaging, may allow more accurate identification of bone loss. This may further improve the performance of the ISIS in predicting functional failure of arthroscopic soft-tissue stabilisation. This was a large prospective study with excellent follow-up to 24 months (91%). We used two definitions of failure, surgical and functional, rather than focusing solely on re-dislocation or significant subluxation (surgical failure). As there appears to be a much higher rate of functional failure, other studies should consider examining functional failure as the primary outcome measure and use surgical failure as the secondary endpoint. As noted by Castagna et al 23 follow-up of 24 months may be inadequate, as recurrence after can occur up to ten years after arthroscopic Bankart repair. We acknowledge that following our patients for a longer time could have affected the results. In addition, although an a priori power analysis was undertaken, we did not account for the large difference in distribution within the groups; thus our study may still be under-powered. We found a higher rate of failure following arthroscopic Bankart repair than if surgical failure was the only measure used. We were not able to predict surgical failure following this procedure using the ISIS or WOSI scores. The baseline WOSI was significantly lower in patients who had functional failure, and 60% of those with a preoperative ISIS > 6 failed to return to pre-injury activity. However, even though a statistically significant difference was found in the mean WOSI scores between those patients who returned to pre-injury activity and those who did not, this difference was less than the previously described clinically important difference. The identification of a pre-operative WOSI that provides a cut-off point for determining the outcome after arthroscopic Bankart could also be tested in a future study. A larger cohort, combined with a longer follow-up, using functional failure as the primary outcome, may answer these questions more definitively and further enhance the ability of the ISIS and the WOSI scores to guide surgical decision making for the patient with post-traumatic recurrent anterior shoulder instability. Dr Beaupre receives salary support from the Canadian Institutes of Health Research as a New Investigator (Patient Oriented Research) and Alberta Innovates Health Solutions as a Population Health Investigator. This study was supported by the Edmonton Orthopedic Research Committee. The author or one or more of the authors have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this article. This article was primary edited by G. Scott and first proof edited by J. Scott. References 1. Brophy RH, Marx RG. 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