Biomechanical effects of different suture pretension levels in suture-bridge repair of supraspinatus tendon tears: a finite element analysis

Objective The optimal initial suture pretension during suture-bridge repair of full-thickness supraspinatus tendon tears remains uncertain and is largely determined by the surgeon’s experience. This study aimed to evaluate the effects of different suture pretensions on the mechanical environment of the tendon-bone interface and to provide a biomechanical reference for intraoperative tension control. Methods A three-dimensional finite element model of the shoulder joint was reconstructed from computed tomography data of a healthy adult volunteer. A full-thickness supraspinatus tear was simulated and repaired using a double-row suture-bridge configuration. Seven total pretension levels (30–90 N, in 10 N increments) and three shoulder abduction positions (10°, 20°, and 30°) were combined to generate 21 loading conditions. The mean contact pressure, effective contact area, relative interfacial displacement, and tendon-side von Mises stress were analyzed. Results Increasing pretension increased the mean tendon-bone contact pressure at all abduction angles. At 20° of abduction, the mean contact pressure increased from 0.382 MPa to 0.856 MPa. The peak tendon-side von Mises stress also increased with pretension, reaching a maximum of 4.533 MPa in the 30°/90 N condition. The effective contact area changed only slightly at 10° of abduction, decreased from 181.4 mm 2 to 169.5 mm 2 at 20°, and reached relatively high values at 50–60 N at 30°. High-stress regions were mainly concentrated around the medial-row suture perforation sites and expanded as pretension increased. Conclusion Suture pretension improved tendon-bone compression and initial interfacial stability, but higher pretension increased local pressure and tendon stress concentration. Within the tested configurations, 50–60 N represented an intermediate, condition-dependent range rather than a universal clinical target.