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

Purpose: 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.

Methods: 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 60 N. The load was increased stepwise up to 100 and 180 N. Cyclic displacement (means + standard dev.) as well as load-to-failure was determined, and mode of failure was recorded.

Results: In the reconstructed shoulders at 60 N, a mean cyclic displacement of 3.2 ± 0.7 mm was found in the 25 % tear, 2.6 ± 0.6 mm in the 50 % tear. At 100 N, 5.1 ± 1.2 mm was seen in the 25 % tear and 4.3 ± 0.3 mm in the 50 % tear. At highest load of 180 N, 7.6 ± 2.2 mm was recorded in the 25 % tear, 6.5 ± 0.8 mm was found in the 50 % tear. Ultimate failure load was 486 ± 167 N in the 25 % tear and 455 ± 213 N 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.

Conclusions: 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.

Clinical Relevance: 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.