A Biomechanical Comparison of Tendon-Bone Interface Motion and Cyclic Loading Between Single-Row, Triple-Loaded Cuff Repairs and Double-Row, Suture-Tape Cuff Repairs Using Biocomposite Anchors

Purpose: To compare tendon-bone interface motion and cyclic loading in a single-row, triple-loaded anchor repair with a suture-tape, rip-stop, double-row rotator cuff repair. Methods: Using 18 human shoulders from 9 matched cadaveric pairs, we created 2 groups of rotator cuff repairs. Group 1 was a double-row, rip-stop, suture-tape construct. Group 2 was a single-row, triple-loaded construct. Before mechanical testing, the supraspinatus footprint was measured with calipers. A superiorly positioned digital camera optically measured the tendon footprint motion during 60 degrees of humeral internal and external rotation. Specimens were secured at a fixed angle not exceeding 45 degrees in reference to the load. After preloading, each sample was cycled between 10 N and 100 N for 200 cycles at 1 Hz, followed by destructive testing at 33 mm/s. A digital camera with tracking software measured the repair displacement at 100 and 200 cycles. Ultimate load and failure mode for each sample were recorded. Results: The exposed anterior footprint border (6.5% +/- 6%) and posterior footprint border (0.9% +/- 1.7%) in group 1 were statistically less than the exposed anterior footprint border (30.3% +/- 17%) and posterior footprint border (29.8% +/- 14%) in group 2 (P = .003 and P < .001, respectively). The maximal internal rotation and external rotation tendon footprint displacements in group 1 (1.6 mm and 1.4 mm, respectively) were less than those in group 2 (both 3.6 mm) (P = .007 and P = .004, respectively). Mean displacement after 100 cycles for group 1 and group 2 was 2.0 mm and 3.2 mm, respectively, and at 200 cycles, mean displacement was 2.5 mm and 4.2 mm, respectively (P = .02). The mean ultimate failure load in group 1 (586 N) was greater than that in group 2 (393 N) (P = .02). The suture-tendon interface was the site of most construct failures. Conclusions: The suture-tape, rip-stop, double-row rotator cuff repair had greater footprint coverage, less rotational footprint displacement, and a greater mean ultimate failure load than the triple-loaded, single-row repair on mechanical testing. No double-row or single-row constructs showed 5 mm of displacement after the first 100 cycles. The most common failure mode for both constructs was suture tearing through the tendon. Clinical Relevance: Differences in cuff fixation influence rotational tendon movement and may influence postoperative healing. Stronger repair constructs still fail at the suture-tendon interface.