Biomechanical evaluation of patch augmentation in a rotator cuff repair model using a porcine flexor digitorum profundus tendon: influence of knot tying and time-zero stability.

BACKGROUND: This study evaluates the biomechanical effects of acellular dermal matrix (ADM) patch augmentation in a rotator cuff repair model and determines the effect of medial knot tying on time-zero stability. METHODS: A biomechanical study was conducted using a porcine flexor digitorum profundus tendon model. Eighteen specimens were assigned to three groups: non-patched repair with medial row knot tying (n=5), patch-augmented repair without medial row knot tying (n=4), and patch-augmented repair with medial row knot tying (n=4). All repairs were performed using a standardized double-row suture bridge technique. Biomechanical testing assessed elongation, strain, load to failure, and construct stiffness at time zero. RESULTS: Patch augmentation without medial row knot tying resulted in significantly greater tendon elongation (12.9±6.5 mm) than nonpatched repairs (5.0±5.3 mm, P=0.016) and patch-augmented repairs with medial row knot tying (4.4±4.4 mm, P=0.027). Similarly, strain was significantly higher in the patch-augmented group without medial knot tying (75.8%±42.9%) than in the non-patched repair (35.2%±38.9%, P=0.028) and patch-augmented repair with medial knot tying groups (29.1%±28.9%, P=0.052). However, load to failure did not differ significantly among the groups (P>0.05). CONCLUSIONS: ADM patch augmentation did not enhance time-zero mechanical strength in the tested conditions, though biomechanical advantages might emerge after integration to the tendon. In addition, patch augmentation without medial row knot tying showed the highest elongation and strain among groups, potentially reducing the stability of the repair. Level of evidence: V, controlled laboratory study.