Improved restoration of biomechanical factors using a narrow-box shaped reconstruction compared to a wide one in superior capsular reconstruction for irreparable supraspinatus tendon tears: a biomechanical study using a static shoulder simulator.

ABSTRACT

HYPOTHESIS AND/OR BACKGROUND: Extensive, irreparable rotator cuff tears remain a surgical challenge and multiple treatment options are proposed and currently in use. To biomechanically compare superior glenohumeral translation, subacromial contact pressures, and area in a box-shaped reconstruction using the long head of the biceps tendon (LHBT) in an irreparable supraspinatus tendon tear model. METHODS: Seven cadaveric shoulders (mean age 61 years; range 32-84 years; standard deviation 22.3) were tested with a custom testing rig used to evaluate superior translation; subacromial contact pressures; and areas at 0°, 30°, and 60° of glenohumeral abduction. Conditions tested included the native state; a complete tear of the supraspinatus tendon; a wide box-shaped, double-bundle LHBT superior capsular reconstruction (BS-SCR); and a narrow BS-SCR. RESULTS: Compared with the wide BS-SCR, the narrow BS-SCR had statistically significantly lower median contact pressure at 30° and 60°. The subacromial contact area showed a statistically significant difference at 0° (P = .001) and 30° (P = .004) for the narrow BS-SCR compared with the wide BS-SCR. At an abduction angle of 0°, the narrow BS-SCR could restore superior translation significantly better compared with the wide construct. For all angles, the wide and narrow BS-SCR increased the median subacromial distance statistically significantly. The contact areas in 30° and 60° of abduction were higher for all scenarios, both peaking in the intact state in 30° with approximately 600 mm2. CONCLUSIONS: In comparison to a wide BS-SCR, a narrow BS-SCR using the LHBT has biomechanical advantages in regard to subacromial contact pressures, the subacromial contact areas, as well as the acromiohumeral distance. The width of the reconstruction, therefore, has a direct influence on the success of the technique.