Shoulder rotator cuff tears can be very debilitating and painful. Whilst massive tears may defy attempts at surgical repair due to the size of the defect, various biological materials have been proposed to reinforce tenuous repairs; initial results have been promising. It has been suggested that these materials may be used to bridge defects in the rotator cuff as a ‘patch’ or ‘interposition implant’ to provide pain relief and even offer some hope of functional recovery. A porcine dermal collagen implant (Permacol ©) has been engineered and introduced for the repair and reconstruction of soft tissues in the human body. In orthopaedics, it has been successfully used in the reinforcement and augmentation of rotator cuff repairs by suturing it over the repaired tendon. Proper et al reported good short term results in using this implant to bridge defects in massive rotator cuff tears and suggested it was good solution for this group of patients, reporting improvement in all aspects of the Constant Score. We have used Permacol © to reinforce cuff repairs with satisfactory results and thus considered its use as a salvage procedure to bridge massive rotator cuff defects, both of traumatic and degenerate origins. Unfortunately, we have seen with great concern that our results have been less than satisfactory. In a cohort of 20 patients who underwent Permacol © interposition / rotator cuff repair, 4 of these have failed, despite a promising initial recovery phase with good pain relief. We believe that use of this and similar implants to bridge a defect in the cuff is not indicated; MRI and dynamic ultrasound examination showed an inflammatory response in the shoulder, and resulting weakness/failure of the implant. We present clinical, radiographic, and histological findings of our experience and a discussion as to the probable cause for the failure of this implant in this particular group of patients.