Addition of a second double-row reduces fragment micromotion and increases fixation strength in suture fixation of a bony Bankart injury: A biomechanical study.

PURPOSE: The purpose of the present study was to evaluate micromotion and failure load when the bony Bankart bridge (BBB) is performed with one versus two double-rows. It was hypothesized that the addition of a second double-row would reduce fragment micromotion and increase ultimate failure load. METHODS: Seven pairs of fresh-frozen cadaveric shoulders (age: 48 years [22-65 years], sex: 57.1% male) with bony Bankart lesions, with a defect width of 25% of the glenoid diameter, were tested in the present study. In a paired design, one shoulder underwent the BBB with one double-row, and the contralateral shoulder underwent the BBB with two double-rows. Micromotion of the bony Bankart fragment was tested by cyclic non-physiological point loading (5-20 N at 1 Hz for 50 cycles) using a dynamic tensile machine. Optical markers and a three-dimensional digitizer established fragment and glenoid coordinate systems, enabling precise tracking of translational and rotational displacements of the fragment. This was followed by failure testing, where the fragment was loaded to failure at 0.5 mm/s. Failure load and stiffness were recorded. RESULTS: Under inferior point loading, the repair with one double-row demonstrated significantly greater rotation about the x-axis (5.20° [3.01°-5.29°] vs. 1.64° [0.94°-2.40°], p = 0.016, q = 0.047) and translation along the z-axis (2.78 mm [1.81-4.20 mm] vs. 1.06 mm [0.51-1.51 mm], p = 0.016, q = 0.047) compared with the repair with two double-rows. Under superior point loading, no significant differences were observed for the rotational or translational outcomes. The repair with one double-row demonstrated a significantly lower failure load than the repair with two double-rows (388 N [243-463 N] vs. 602 N [539-641 N], p = 0.016, q = 0.031). No significant differences in stiffness were found between groups. CONCLUSIONS: Fixation with two double-rows resulted in a significantly less fragment micromotion and a significantly greater failure strength compared with the BBB using one double-row. LEVEL OF EVIDENCE: N/A.