THE USE OF NON-SCREW ROTATOR CUFF ANCHORS IN OSTEOPOROTIC BONE- IS IT SAFE?

Abstract

Introduced in 2005, the Opus Magnum (Arthrocare) anchor has been used in our unit for repair of rotator cuff tears. It is a non-screw type anchor which relies on the deployment of wings locked in the subchondral bone. In order to evaluate whether these anchors migrate after implantation we undertook radiographic examination of their placement at intervals. We attempted to assess whether loss of fixation could be secondary to osteoporosis. Between 2005 and 2006, 106 patients (59 female, 47 male) aged 35–84 years (average age 62 years) underwent arthroscopic repair of rotator cuff tears with a total of 229 anchors. A review of radiographs taken at six weeks and 12 months post-insertion was undertaken. Cortical index of the proximal humeral diaphysis was measured from the AP radiograph indicating bone density; this involved measuring humeral width and medullary cavity diameter at a fixed point of 10cm below the greater tuberosity of the humerus. At six weeks follow-up there were no anchor pull-outs seen on radiographs. At 12 months follow-up 10 of the 229 anchors were found to have pulled out of the bone, equating to a failure rate of 4%. Of these seven of the 10 patients were asymptomatic. The average cortical index was found to be significantly lower in the failure group. Bone quality at the greater tuberosity of the humerus can be insufficient to withstand the tensions developed in newer anchor technology, leading to anchor migration. We present evidence that radiographs may be sufficient to influence the clinician’s choice of anchorage device. An economic estimation of bone density would be a helpful predictor of pull-out strength of suture anchors, essentially a low cortical index would indicate that these anchors are more likely to fail. A routine radiograph at 12 months would also identify the asymptomatic anchor failures.