Tissue-engineered rotator cuff tendon using porcine small intestine submucosa. Histologic and mechanical evaluation in dogs.

To determine its efficacy in stimulating the regeneration of a rotator cuff tendon, an implant of 10-ply porcine small intestinal submucosa was used to replace a completely resected infraspinatus tendon in 21 adult mongrel dogs. The contralateral infraspinatus tendon was elevated and then reattached to the greater tubercle with sutures to mimic conventional repair (sham operation). Mechanical evaluations were performed at 0, 3, and 6 months (five specimens at each time period). Histologic comparisons were made at 3 and 6 months (three specimens). At both times, the gross appearance, histologic continuity, and failure mode of the constructs mimicked those of sham-operated and native infraspinatus tendons, thus suggesting host tissue ingrowth and implant remodeling with solid integration of the regenerated tissue to muscular and bony interfaces. Tissue ingrowth occurred without histologic evidence of foreign body or immune-mediated reactions or adhesions to peripheral tissues. Sham operations simulated tendon mobilization and reimplantation procedures routinely performed to treat chronic rotator cuff tendon injuries. Although the ultimate strength of small intestinal submucosa-regenerated tendons was significantly less than that of native infraspinatus tendons (P < 0.001), it was similar to that of reimplanted tendons at 3 (P > 0.05) and 6 months (P > 0.05).