Biomechanical Analysis of Rotator Cuff Repair: Comparison of Sutures and Fixation Techniques in a Synthetic Model

Introduction Irreparable rotator cuff tears represent one of the greatest challenges in contemporary orthopedic surgery, imposing significant functional limitation and requiring reconstruction strategies with high mechanical fixation strength. The choice between different suture materials and anchoring techniques directly influences the initial biomechanical stability of the repair, determining construct safety during the critical period of biological healing. Objective To evaluate and compare the load-to-failure of four tendon repair configurations in humeral head synthetic models (Sawbones®; Pacific Research Laboratories, Inc., Vashon, WA, USA), combining two surgical sutures - Ethibond® USP 5 (Ethicon Inc., Raritan, NJ, USA; braided polyester) and FiberWire® USP 2 (Arthrex Inc., Naples, FL, USA; ultra-high-molecular-weight polyethylene) - with two fixation techniques: double metal anchor and transosseous tunnel. Methods Linear tensile mechanical tests to failure were performed on 20 shoulder models, with five samples per experimental group. The tendon was simulated using synthetic leather strips (corino), secured with a five-pass epitendinous running suture. Maximum load to failure was measured with a calibrated dynamometer in kilogram-force (kgf) and converted to Newtons (N). Inclusion criteria restricted the analysis to failures exclusive to the suture material, excluding any structural construct failure. Results All configurations exceeded the 200 N biomechanical threshold considered safe for early rehabilitation. The Ethibond® transosseous tunnel group showed the highest mean strength (357.55 N; SD ± 46.7), followed by FiberWire® with double anchor (330.88 N; SD ± 18.3), transosseous FiberWire® (296.36 N; SD ± 8.6), and Ethibond® with double anchor (293.41 N; SD ± 43.9). Between-group Welch's t-tests showed a trend toward higher strength for the Ethibond® transosseous configuration versus Ethibond® double anchor (p = 0.056), and a significant difference between FiberWire® double anchor and FiberWire® transosseous (p = 0.010); pooled main effects of suture material and fixation technique alone were not significant, suggesting an interaction between suture caliber and fixation geometry. Conclusion In this synthetic model, the transosseous technique combined with high-caliber polyester suture produced the greatest mean mechanical strength, although the advantage over anchor fixation did not reach statistical significance. Surgeons may achieve biomechanically safe and cost-effective fixation using transosseous tunnels with Ethibond® USP 5, reserving anchors and FiberWire® for cases in which tear geometry precludes tunnel creation.