Biomechanical effects of superior capsular reconstruction in a rotator cuff–deficient shoulder: a cadaveric study

Abstract

Background: Superior capsular reconstruction (SCR) has been gaining popularity as a treatment for irreparable rotator cuff tears (RCTs), especially in younger patients. This biomechanical study aimed to investigate how SCR affects functional abduction force, humeral head migration, and passive range of motion following an irreparable RCT. We hypothesized that SCR will restore these parameters to nearly intact shoulder levels. Methods: Six fresh-frozen cadaveric shoulders were evaluated using a custom biomechanical testing apparatus. Each shoulder was taken through 3 conditions: (1) intact (control); (2) irreparable, complete supraspinatus (SS) tear; and (3) SCR. Functional abduction force, superior humeral head migration, and passive range of motion, including axial shoulder rotation, were measured in static condition at 0 , 30 , and 60 of glenohumeral abduction. Data were analyzed using the paired Student t test or Wilcoxon signed rank test, depending on the results of normality testing. Results: The irreparable SS tear resulted in significantly lower functional abduction force at 30 of abduction (P ¼ .01) and a trend toward a decrease (P ¼ .17) at 60 compared with the intact configuration. SCR shoulders produced greater functional force at 0 compared with the tear configuration (P ¼ .046). Humeral head migration was significantly increased by 4.4 and 3.0 mm at 0 and 30 of abduction, respectively, when comparing the intact vs. SS tear configurations (P ¼ .001). SCR decreased superior migration down to levels of intact shoulders at 0 and 30 of abduction (P ¼ .008 and P ¼ .013, respectively) and was not significantly different from the intact configuration at any angle. SCR decreased passive shoulder extension compared with the tear configuration and increased abduction compared with the intact configuration (P ¼ .007 and P ¼ .03, respectively). The overall arc of axial rotation was not significantly different between SCR and the intact configuration at any angle. Conclusions: In the setting of an irreparable SS tear, SCR restores key biomechanical parameters of the shoulder to intact levels. SCR should be considered for qualifying patients with irreparable RCTs.

Biomechanical outcomes of superior capsular reconstruction for irreparable rotator cuff tears by different graft materials-a systematic review and meta-analysis

“…The unbalanced loading condition was achieved by removing the loads from latissimus dorsi and pectoralis major, and added an additional 40N to the deltoid. Two studies reduced deltoid load by half (balanced system: 20N; unbalanced system: 40N) ( 49 , 52 ). The loading conditions were not properly displayed in the other six experiments ( 46 – 48 , 51 , 53 , 56 ).…”

Clinical and Functional Outcomes by Graft Type in Superior Capsular Reconstruction: A Systematic Review and Meta-analysis

“…14,20 Although biomechanical studies have not assessed the effectiveness of SCR with xenograft, cadaveric studies evaluating SCR with dermal allograft have shown excellent results. 55 SCR with xenograft may be able to provide similar restoration of shoulder function with more cost-effectiveness. However, use of the LHBT may be limited by its availability owing to anatomic variation or concomitant rupture.…”

Understanding shoulder pseudoparalysis. Part II: Treatment

“…Ishihara et al described in a cadaveric study that massive cuff tears result in not only superior instability but also anterior–posterior capsular instability ( 16 ). A recent cadaveric study by Rybalko et al found that superior capsular reconstruction (SCR) significantly decreased superior migration by 72 and 64% at 0° and 30° of abduction, respectively, compared with a full-thickness tear, largely re-centring the humeral head ( 17 ). The graft effectively functions as a spacer by shifting the humerus inferiorly and decreasing subacromial pressure.…”