BACKGROUND: Following repairs of large-to-massive tears of the rotator cuff, the rates of tendon retears are high and often involve tissue deficiency. Animal studies of the Restore Orthobiologic Implant, a collagen-based material derived from the small intestine mucosa of pigs, have indicated that it might be used to help overcome such problems. We carried out a study to determine whether patients who received this xenograft to augment a rotator cuff repair exhibited greater shoulder strength, shoulder function, and/or resistance to retearing. METHODS: We compared data from a group of patients who had undergone conventional rotator cuff repair with xenograft augmentation (the xenograft group) with data from a group in whom a repair had been done by the same surgeon without augmentation (the controls). The groups were matched for gender, mean age, and mean size of the rotator cuff tear. All subjects completed a pain and function questionnaire and were given a systematic clinical shoulder examination preoperatively and at three, six, and twenty-four months postoperatively. The twenty-four-month visit included magnetic resonance imaging to determine whether a retear had occurred. RESULTS: Four patients who had received a xenograft had a severe postoperative reaction requiring surgical treatment. At two years after the surgery, six of the ten tendons repaired with a xenograft and seven of the twelve control tendons had retorn, as documented by magnetic resonance imaging. The patients with a xenograft had significantly less lift-off strength, as measured with a dynamometer, and significantly less strength in internal rotation and adduction than the controls at two years after the surgery (all p < 0.05). Also, the xenograft group had significantly more impingement in external rotation, a slower rate of resolution of pain during activities, more difficulty with hand-behind-the-back activities, and less sports participation (all p < 0.05). CONCLUSIONS: Two years after surgical repair of a large rotator cuff defect supplemented with a xenograft, patients had several persisting deficits and no recognizable benefit as compared with the results in a control group. In view of these findings, together with the unsatisfactorily high proportion of patients with a severe inflammatory reaction to the xenograft, we do not recommend use of the Restore Orthobiologic Implant in its present form. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.
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