Abstract
Introduction: Inflammatory or degenerative processes of glenohumeral joint lead to pain and restriction of movements of the shoulder. As with the treatment of disabling arthritis in the other large joints, prosthetic replacement of the glenohumeral joint has gained in popularity because of its efficacy in relieving pain. Several designs for the total shoulder replacement (TSR) prostheses are currently used for the cemented and cementless implantation. The uncemented prostheses were developed in order to achieve a “biological” fixation of the implant to the adjacent bone. No survivorship data exists to compare these devices to the original TSR prostheses for cemented implantation, although this information is crucial for the decision making regarding their use. We present the long term survival rates of the Bio-Modular TSR prosthesis for uncemented implantation.
Methods:The Bio-Modular TSR prosthesis was implanted in 90 patients between 1989–1994 (15 men and 75 women, mean age 61 years, range 19–92 years). This prosthesis was the first to use an anatomical, offset humeral head, based on the study on the bony anatomy of the upper humerus. The mean follow-up period was 8.8 years. Survivorship analysis, according to the method described by Murray et al. and based on Rothman’s formula for the confidence limits determination, was used for the outcome evaluation of all the prostheses studied. The criterion for failure in this series was are-operation on the shoulder with a removal of part or all of the prosthesis.
Results: The ten-year cumulative survival rates of the Bio-Modular prosthesis was 71.7%.
The main cause for this low survivorship rate is the low survivorship of this prosthesis among patients with primary osteoarthritis, 61.4% ten years survivorship. Conversely among the patients with rheumatoid arthritis the ten years survivorship was considerably higher (86.9%). The main cause of failure of this prosthesis was related to the glenoid component and was either due to aseptic glenoid component loosening (in 54% of the failed cases) or a failure (uncoupling) of the polyethylene bearing liner in 17% of failed cases. Furthermore about 70% of the failed cases occurred during the first four postoperative years showing an overall four years cumulative survivorship rate of 80.9%.
Discussion: The survivorship data presented here indicate that the use of the Bio-Modular TSR prosthesis in patients with osteoarthritis produces less favorable results, comparing to the classical (Neer II) cemented designs. Therefore, the use of this prosthesis in patients with osteoarthritis should be reconsidered. But the higher survival of the prosthesis in the patients with rheumatoid arthritis suggests its safe use in the rheumatoid patients.
The abstracts were prepared by Ms Orah Naor. Correspondence should be addressed to Israel Orthopaedic Association at PO Box 7845, Haifa 31074, Israel.
