Histologic Evaluation of Biopsy Specimens Obtained After Rotator Cuff Repair Augmented With a Highly Porous Collagen Implant

Purpose: To histologically evaluate biopsy specimens from patients who previously underwent rotator cuff repair augmented with a highly porous collagen implant. Methods: Biopsies of collagen implant/ host-tissue constructs were obtained from 7 patients undergoing a second arthroscopic procedure at various time periods (5 weeks to 6 months) after arthroscopic rotator cuff repair augmented with a collagen implant overlay. The biopsy specimens were examined histologically for host-tissue ingrowth, host-tissue maturation, and host-implant biocompatibility. Results: At the earliest time period (5 weeks), the biopsy revealed the presence of host cells (fibroblasts) within the interstices of the porous collagen implant. Cells were aligned along the linear orientation of the collagen implant structure, and there was evidence of early collagen formation. The 3-month biopsies showed increased collagen formation, maturation, and organization over the surface of the implant and evidence of the collagen implant. At 6 months, the newly generated tissue had the histologic appearance of a tendon, suggesting functional loading of the new generated host tissue. There was no evidence of any remnants of the collagen implant in the 6-month biopsy. There was no evidence of any inflammatory or foreign body reaction within any of the tissue samples. Conclusions: Biopsies of collagen implants retrieved from human rotator cuff repair subjects revealed cellular incorporation, tissue formation and maturation, implant resorption, and biocompatibility. Clinical Relevance: The histologic observations from these clinical biopsies support the biocompatibility of this implant and its ability to promote new connective tissue with the histological appearance of tendon over the surface of the native cuff tendon.