Metal-backed glenoid implant with polyethylene insert is not a viable long-term therapeutic option

Abstract

The aims of this study were to determine the survival of anatomic total shoulder arthroplasty with uncemented metal-backed (MB) glenoid components with a polyethylene (PE) insert in primary osteoarthritis, to assess the reasons for revision surgery, and to identify patients and diagnostic factors that influence failure rates. Between 1994 and 1999, 165 patients (mean age, 68years) with primary osteoarthritis were treated with anatomic total shoulder arthroplasty using an uncemented MB/PE glenoid component. Outcomes were assessed both clinically and radiologically with a minimum of 2years of follow-up. A prosthetic survival curve was constructed with the end point defined as either partial or complete revision, using 100% confidence intervals. Survival rate free of revision was 46% (100% confidence interval, 32%-54%) at 12years. At a mean follow-up of 8.5years (range, 2-16years), revision was required in 61 patients (37%); 80% of shoulders undergoing revision (49 of 61) had evidence of PE wear. Glenoid loosening (because of osteolysis secondary to wear debris), soft tissue deficiency, and prosthetic instability were the most common modes of failure. Younger patients and biconcave glenoids (with posterior humeral subluxation) have a negative effect on implant survival. Proximal humerus osteolysis was significantly more frequent in shoulders with PE wear. Exchange of the PE insert (with conservation of the MB tray) was possible in only 3% of the revised shoulders. Uncemented MB glenoid resurfacing is not a viable long-term therapeutic option because of accelerated PE wear leading to early revision surgery. Conservation of the MB tray with reinsertion of a new PE insert is rarely possible because of glenoid bone loss, implant loosening, soft tissue deficiency, and prosthetic instability. Younger patients and biconcave glenoids have a negative effect on implant survival.