Efficacy of bone marrow-stimulating technique in rotator cuff repair.

BACKGROUND: This study used a chronic rotator cuff (RC) tear model to investigate the effect of microfracture as a bone marrow-stimulating (BMS) technique for RC healing.

METHODS: A chronic retracted RC tendon tear model was created bilaterally in the subscapularis tendons of 20 New Zealand rabbits. The tendons were repaired after 8 weeks using a single-row configuration. Tendons in the right shoulder were repaired in standard fashion (control group). Microfractures were performed in the left shoulders before repair (microfracture group). The animals were euthanized 8 and 16 weeks after repair. The repaired tendons were tested biomechanically for their ultimate failure load, linear stiffness, and elongation at failure. Gross and histologic evaluations of the tendon-to-bone healing were evaluated.

RESULTS: Macroscopically, subscapularis tendons were attached on the lesser tuberosity. In the microfracture group, collagen fibers were organized in relatively thicker bundles. The mean ultimate failure load of the microfracture group was significantly greater at 8 weeks (148.4 ± 31 N vs. 101.4 ± 26 N, respectively; P = .011) and 16 weeks (155 ± 30 N vs. 114.9 ± 25 N, respectively; P = .017) after repair. There were no significant differences between the groups for linear stiffness at 8 weeks (15.9 ± 2.7 N/mm vs. 15.8 ± 1.3 N/mm, respectively; P = .798) and 16 weeks (16.9 ± 4.3 N/mm vs. 17.1 ± 3.6 N/mm, respectively, P = .848) and elongation at failure at 8 weeks (4.7 ± 1.1 mm vs. 4.7 ± 1.3 mm, respectively; P = .848) and 16 weels (4.8 ± 1.5 mm vs. 4.9 ± 0.9 mm, respectively; P = .749).

CONCLUSION: The microfracture on the tuberosity of the repaired chronic rotator cuff tear promoted dynamic tendon healing with significantly increased ultimate force to failure and with thicker collagen bundles and more fibrocartilage histologically at 8 weeks.