Histologic and biomechanical comparison of fascia lata autograft, acellular dermal xenograft, and synthetic patch for bridging massive rotator cuff tear in a rabbit model.

Background: Bridging repair has emerged as a promising and reliable treatment strategy for the massive rotator cuff tears (MRCTs). However, there remains a lack of evidence on which bridging graft provides the better repair results, and a dearth of animal studies comparing bridging repairs with different grafts. The purpose of this study was to evaluate the histological and biomechanical outcomes of commonly used grafts (autologous fascia lata (FL), acellular dermal matrix graft (ADM), and polyethylene terephthalate (PET) patch).

Methods: A total of 66 male New Zealand White Rabbits were used to mimic a model of unilateral chronic MRCTs. The rabbits were randomly divided into three groups: (1) FL group, which underwent bridging repair with autologous FL; (2) ADM group, which underwent bridging with ADM; and (3) PET group, which underwent bridging with PET patch. Tissue samples were collected and subjected to histological analysis using Hematoxylin and eosin, Picrosirius red, Safranin O/Fast green staining, and Immunostaining. Collagen diameter and fibril density in the regenerated tendon was analyzed with transmission electron microscopy (TEM). Additionally, biomechanical tests were performed at 6 and 12 weeks after repair.

Results: The regenerated tendon successfully reattached to the footprint in all experimental groups. At 6 weeks after repair, the FL group had a significantly higher Modified Tendon Histological Evaluation (MTHE) score at the regenerated tendon than the PET group (13.2 ± 1.64 vs 9.6 ± 1.95, respectively;  = 0.038). The picrosirius red staining results showed that the FL group had a significantly higher type I collagen content than the ADM and PET groups at 6 weeks, and this difference was sustained with the PET group at 12 weeks ( < 0.05). Immunofluorescence analysis against CD68 indicated that the number of macrophage infiltrates was significantly lower in the FL group than in the ADM and PET groups ( < 0.05). At 12 weeks after repair, the area of Safranin O metachromasia was significant greater in ADM group than that in the PET group ( = 0.01). The FL group showed a significantly larger collagen diameter in the regenerated tendon than the PET group ( < 0.05), as indicated by TEM results. Furthermore, the FL group resulted in a greater failure load (at 6 weeks; 118.40 ± 16.70 N vs 93.75 ± 9.06 N, respectively;  = 0.019) and elastic modulus (at 6 weeks; 12.28 ± 1.94 MPa vs 9.58 ± 0.79 MPa, respectively;  = 0.024; at 12 weeks; 15.02 ± 2.36 MPa vs 11.63 ± 1.20 MPa, respectively;  = 0.032) than the ADM group.

Conclusions: This study demonstrated that all three grafts could successfully bridging chronic MRCTs in a rabbit model. However, autologous FL promoted tendon regeneration and maturation, and enhanced the tensile properties of the tendon-to-bone complex when compared with ADM and PET grafts.