Pressed Long Head of the Biceps Tendon Autograft Augmentation Enhances Tendon-to-Bone Healing in a Rat Model of Rotator Cuff Repair.

Abstract

To investigate the underlying regeneration mechanisms of biological augmentation using pressed long head biceps tendon (LHBT) in a rat model. Bilateral infraspinatus tendons were torn and repaired 1 week later in 32 Sprague-Dawley rats. In the biologic augmentation (BA) group, the LHBT was extracted, pressed, and augmented on the repair site. Histological evaluation was performed at 3 and 6 weeks to measure the thickness of the repaired tendon, number of chondrocytes and non-chondrocytes, percentage of aligned chondrocytes, areas of fibrocartilage and collagen fiber, and COL1/COL3 ratio. Genetic expression of collagen types 1 and 3 (COL1 and COL3, respectively); matrix metalloproteinases-1, 3, and 13; and transforming growth factor beta were measured at 3 and 6 weeks. Mechanical testing was performed at 3 and 6 weeks. Tendon thickness (3.72 mm vs 2.83 mm; P = .01), number of chondrocytes (73.8 vs 39.7; P = .01), fibrocartilage area (0.35 vs 0.22 mm²; P = .03), and collagen fiber area (0.20 vs 0.11 mm²; P = .03) at 6 weeks were significantly higher in the BA group than in the control group. COL1/COL3 ratio at 3 and 6 weeks was significantly higher in the BA group than in the control group (3 weeks, 1.01 vs 0.51; P = .01 and 6 weeks, 0.68 vs 0.27; P = .04). COL3 expression at 6 weeks was significantly lower in the BA group (P = .02). Matrix metalloproteinase-1 expression at 3 weeks was significantly higher in the BA group (P = .005). The ultimate load to failure at 6 weeks was significantly higher in the BA group (51.5 N vs 31.5 N; P = .03). Biological augmentation using pressed autologous LHBT promoted tendon-to-bone healing and enhanced mechanical strength. Augmentation with pressed LHBT may improve the biology and mechanical strength of rotator cuff repair.