Biomechanical evaluation of the H-Loop technique and single-row knotted technique for repairing upper third subscapularis tendon injuries.

We evaluated the biomechanical performance of the new knotless H-Loop technique in repairing the upper third subscapularis (SSC) tendon tear, and compared these results with the single-row knotted technique. A total of 69 subscapularis tendons from sheep were collected, with 10 specimens randomly selected for comprehensive biomechanical testing after either complete tendon or upper third tear. An additional five specimens were dedicated to measuring the size and extent of the footprint area of the SSC tendon. The remaining 44 specimens were randomly and evenly divided into two groups: H-Loop(n = 11) and single-row knotted groups(n = 11). Contact area and pressure, ultimate tensile strength, stiffness, and elongation were assessed. Compared to the single-row knotted technique, the footprint contact pressure repaired by H-Loop technique was significantly larger (mean difference = 5.09 N, p = 0.004), but the footprint contact area (64.09 ± 10.37mm) was similar to that of single-row knotted technique (58.27 ± 9.84mm). The ultimate tensile strength and stiffness of the H-Loop technique were significantly greater than those of the single-row knotted technique (mean difference = 16.58 N, p = 0.003; mean difference = 0.82 N/mm, p = 0.002), while the peak-to-peak elongation was significantly lower (mean difference = 0.51 mm, p = 0.030). The primary failure mode for single-row knotted techniques is suture cut-through at the suture-tendon interface, while for the H-Loop technique, the main failure mode is related to the eyelet. The H-Loop technique provides higher tendon-bone contact pressure and mechanical strength with a smaller gap between the tendon and bone compared to the single-row knotted technique.