Superior capsular reconstruction using the long head of biceps tendon: a biomechanical assessment of tenodesis location and angle of fixation.

BACKGROUND

Massive irreparable rotator cuff tears (MIRCTs) treated with superior capsular reconstruction (SCR) using the long head of the biceps tendon have shown satisfactory early results. Different techniques and positions for biceps tenodesis have been described. This study aimed to evaluate the effect of tenodesis location and glenohumeral fixation angle for graft tensioning on the biomechanics of an SCR using a single-strand biceps technique.

METHODS

Eight cadaveric shoulders were mounted onto a custom biomechanical simulator that used static tone loads to the deltoid and rotator cuff muscles. All cadavers were first tested in the intact condition, and then in the simulated MIRCT condition by sectioning the tendinous insertions of the supraspinatus and upper border of the infraspinatus. SCR using the long head of the biceps tendon was then evaluated. Three biceps tenodesis locations relative to the greater tuberosity (anterior, middle, and posterior) and 2 glenohumeral fixation angles (0° and 30°) for graft tensioning were tested. An optical tracking system was used to quantify superior-inferior and anterior-posterior humeral head translation relative to the glenoid, whereas the functional abduction force was quantified using a load sensor. All tests were conducted at 0°, 30°, and 60° of glenohumeral abduction in a randomized fashion.

RESULTS

When assessing isolated superior humeral head migration, all biceps tenodesis locations were effective at decreasing superior migration, with no tenodesis location significantly better than the other (P = .213). However, biceps grafts tensioned at 30° of glenohumeral abduction were significantly better at reducing proximal humeral migration as compared to graft tensioning at 0° abduction (P = .008). Posterior humeral head translation observed in the MIRCT condition was significantly reduced when tensioning the biceps tendon at 30° of glenohumeral abduction compared with 0° for all tenodesis locations (P ≤ .043). The tenodesis location also significantly influenced posterior humeral head translation (P = .001), with the middle and posterior positions restoring near normal humeral head position when fixed at 30° glenohumeral abduction. All SCR techniques using the biceps tendon improved the functional abduction force relative to the MIRCT condition, although no statistically significant differences were observed relative to the intact condition (P ≥ .448).

DISCUSSION

SCR using the long head of the biceps tendon is biomechanically effective in reducing posterosuperior translation of the humeral head in the setting of an MIRCT. Graft tensioning and fixation at 30° of glenohumeral abduction combined with either a middle or posterior tenodesis location on the greater tuberosity most effectively restores near normal time-zero humeral head kinematics.