Reconstruction of 25 and 50% subscapularis tears: a single anchor with a double-mattress suture is sufficient for the reconstruction.

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Evaluation of the biomechanical performance of repairs of 25% (Fox/Romeo II) and 50% (Fox/Romeo III) full-thickness subscapularis tears using a single-suture anchor. Six pairs of human cadaver specimens were used for the testing. Artificial subscapularis tears were created in order to simulate a 25% (6) and a 50% (6) full-thickness tear. The reconstructions were made with a double-loaded suture anchor (5.5-mm Bio-Corkscrew with two No. 2 Fiberwire) creating a double-mattress suture repair. Reconstructions were cyclically loaded from 10 to 60N. The load was increased stepwise up to 100 and 180N. Cyclic displacement (means+standard dev.) as well as load-to-failure was determined, and mode of failure was recorded. In the reconstructed shoulders at 60N, a mean cyclic displacement of 3.2±0.7mm was found in the 25% tear, 2.6±0.6mm in the 50% tear. At 100N, 5.1±1.2mm was seen in the 25% tear and 4.3±0.3mm in the 50% tear. At highest load of 180N, 7.6±2.2mm was recorded in the 25% tear, 6.5±0.8mm was found in the 50% tear. Ultimate failure load was 486±167N in the 25% tear and 455±213N in the 50% tear. Statistically significant differences between the tested repairs were seen neither in cyclic displacement nor in ultimate failure loads (p>0.05). Mode of failure revealed bone fractures and anchor pull-out as major cause in the 25% group, whereas failure of the suture-tendon interface was the major cause of failure in the 50% group. Subscapularis repair using a single double-loaded suture anchor revealed similar biomechanical performance in 25% compared to 50% full-thickness subscapularis tears. With increased tear size, however, an optimized suture-tendon interface seems to become more relevant in order to decrease failure rate of the repair. A single double-loaded suture anchor provides sufficient biomechanical strength even in Fox/Romeo grade III tears of the subscapularis tendon. However, a modified suture configuration is recommended, especially in grade III tears as the suture-tendon interface is the weakest point of the construct.