FAILURE MODES OF SUTURE REPAIR OF THE TUBEROSITIES IN HEMI-ARTHROPLASTY FOR FOUR PART FRACTURE OF THE SHOULDER.

Abstract

Introduction: We investigated the use of suture repair for tuberosities in hemiarthroplasty for 4 part fractures, by examining cadaveric repairs after repetitive loading tests.

Sutures are the most popular repair tool currently. However tuberosity “disappearance” with this is common; and touted as the prime cause for failure. In some studies biochemical lysis has been suggested to explain this. The aim of this study was to analyse the mode of failure.

Materials and Methods: Tests were carried out in line with UK HTA regulations. Eight fresh frozen cadaver shoulders were stripped of all soft tissue except the rotator cuff. A 4 part fracture was then created by osteotomising the tuberosities. A standard hemiarthroplasty implant was cemented in at the native height and retroversion. A tuberosity repair with Ethibond 5 sutures, employed transverse cerclage sutures; and vertical figure of eight repairs, from the cuff to a shaft drill hole.

The repairs were subjected to cyclical tension on the cuff musculature, and simultaneous gleno-humeral motion; using a test process we have described separately. During the entire process the repair site was videoed

At the end of 8000 cycles the tuberosities were probed with a forceps, to record any movement in vertical, horizontal and axial planes. The humeral shaft was also rotated to check for dissociation between tuberosities and shaft.

Results: Uniform failure of the hold on the tuberosities occurred by 8000 cycles. Defining failure as movement of any tuberosity more than 3mm, failure rate was 100% (exact 95% confidence interval 65.2 – 100% due to sample size). Movements of at least 1cm were commonly observed. The sutures were loose but never snapped. Failure mechanisms involved digging of the sutures into the tendon, cutting of the sutures through bone, loss of cancellous supporting structure, and migration of the sutures. Failure occurred early in what we considered to the parallel of 1 to 2 weeks of rehabilitation.

Conclusion: Suture repair of tuberosities has a high chance of failure if the cuff can not be prevented from contracting. We believe failure is early and mechanical, rather than by lysis or biochemical means. More effective alternatives to suture techniques would be desirable.