Glenoid Radius of Curvature and Humeral Head Volume Are Associated With Postoperative Dislocation After Arthroscopic Bankart Repair

Abstract

Purpose: To measure bony morphologic parameters and identify their association with arthroscopic Bankart repair failure. Methods: This was a retrospective comparative study. The inclusion criteria were primary arthroscopic Bankart repair, no prior shoulder surgery, traumatic cause, and had a Bankart (soft tissue and bony) lesion evident on magnetic resonance imaging (MRI). The exclusion criteria were posterior labral pathology, multidirectional instability, connective tissue disorder, rotator cuff pathology, and those who underwent concomitant shoulder procedures. Patients who had a postoperative redislocation (unstable group) were compared with matched patients who did not (stable group). Data were obtained by chart review and from preoperative MRI. Comparisons were made using the Student t test, Fisher exact test, or c 2 test. Statistical significance was defined as P < .05. Inter-rater reliability was measured between reviewers. Results: A total of 45 patients experienced a postoperative dislocation and were matched to 90 patients without a postoperative dislocation. There were no differences in demographic and radiographic variables. The radius of curvature (ROC) of the glenoid was larger (shallower) in the unstable group (23.6 mm vs 22.6 mm, P ¼ .05). The humeral head volume (HHV) trended higher in the unstable group (68.9 mL vs 62.9 mL, P ¼ .06). The glenoid volume was not significantly different. A greater percentage of patients with a glenoid ROC of 24.5 mm or greater (62.1% vs 26.4%, P ¼ .0003) and an HHV of 80 mm 3 or greater (60.8% vs 28.9%, P ¼ .003) experienced a redislocation compared with patients without these factors. Patients with a glenoid ROC of 24.5 mm or more and an HHV of 80 mm 3 or more had greater than 4 times the odds of redislocation (odds ratio, 4.56; 95% confidence interval, 1.44-14.43; P ¼ .0098). Strong inter-rater reliability was found for the HHV, glenoid volume, glenoid ROC, and humeral head ROC measurements (r ¼ 0.94, r ¼ 0.88, r ¼ 0.89, and r ¼ 0.95, respectively). Conclusions: This study shows that large ROC (shallow) glenoids in conjunction with large humeral heads may predispose patients to failure after arthroscopic Bankart repair. Level of Evidence: Level III, retrospective comparative trial. V arious demographic, radiographic, and surgical risk factors for redislocation after arthroscopic Bankart repair have been identified. 1 Despite identification of these risk factors, the long-term redislocation rate after arthroscopic Bankart repair has been reported to be as high as 30%. 2 Variations in the bony morphology of the glenohumeral articulation may predispose certain patients to redislocation after arthroscopic Bankart repair. The critical shoulder angle (CSA) has been shown to affect glenohumeral translation in biomechanical studies. 3 Glenoid retroversion and inferior inclination have been shown to be

Comparison of Glenohumeral Bone Morphology Between Patients With Versus Without Anterior Shoulder Instability

“…Our study included more patients and used a match-pairing design to further identify the differences in glenohumeral joint morphology between the affected and contralateral healthy shoulders, and we found results similar to those of Peltz et al However, we also found the GROC in both the AP (58.26 ± 14.45 mm) and the SI (31.74 ± 4.33) directions was greater than that reported by Peltz et al Such differences can be explained by the different measurement methods and ethnicities of the participants. Vaswani et al 18 used magnetic resonance imaging (MRI) to measure the GROC of patients who underwent arthroscopic Bankart repair, and the mean value of GROC (23.6 mm) was also smaller than our results. This may be due to the different measurement sources (MRI vs CT), and the changes in the glenoid labrum after surgery may also contribute to the differences.…”

“…In addition, our finding that in patients with ASI, the GROC in the SI direction was smaller than in the AP direction was also consistent with previous studies. 14,18 The conformity index, calculated as HROC/GROC, was used to measure the congruency of the glenohumeral joint. We found that this measurement was significantly smaller in the ASI group than in controls (0.44 6 0.10 vs 0.62 6 0.12, respectively; P \ .001).…”

“…In addition, our finding that in patients with ASI, the GROC in the SI direction was smaller than in the AP direction was also consistent with previous studies. 14 , 18 …”

Defining Critical Humeral Bone Loss: Inferior Craniocaudal Hill-Sachs Extension as Predictor of Recurrent Instability After Primary Arthroscopic Bankart Repair

“…The dynamic, 3-dimensional nature of anterior shoulder instability remains poorly understood. Significant gaps in understanding of bone morphology and soft tissue contributions exist and include, but are not limited to, bipolar instability in the medial-lateral axis (the DTD spectrum), 2 capsulolabral hyperlaxity, 4,34 Hill-Sachs size and capsulolabral laxity in relation to multiple dislocations, 9 Hill-Sachs angle and its relation to arm position at time of dislocation, 8,10 labral volume, 42 glenoid version, 27 glenoid concavity, 31,41,44 and motion-dependent dynamic stability from such contributions as labral concavity compression 28 and muscle imbalance. 32 Studies that have attempted to portray the Hill-Sachs lesion in all 3 dimensions have only successfully shown that larger and more medially positioned Hill-Sachs lesions pose greater risk of recurrent instability.…”