Polyethylene wear testing of a nonmechanically linked total elbow replacement.

Background: The objective of this study was to perform a polyethylene wear test on a nonmechanically linked total elbow arthroplasty implant using a clinically relevant in-vitro elbow wear test methodology that simulated 10 years of use in the light to moderate activity of daily living range.

Materials and methods: The test protocol applied an 80° arc of ulnohumeral motion beginning at 30° shy of full extension and progressing to 110° of flexion. Force was applied at 7° to recreate a valgus load on the elbow. A variable joint load profile at a frequency of 0.5 Hz was employed. The implants were tested for 5 million cycles (mc) in a bovine serum lubricant. Implant component failure was characterized and polyethylene wear was determined gravimetrically.

Results: After 5 mc, the small polyethylene bushing wear rate was 0.56 mg/mc. The medium size wear rate was 0.28 mg/mc. Three large sizes were tested and the average wear rate was 0.39 ± 0.07 mg/mc. No implant failure was identified.

Conclusion: The test recreated an in vivo loading environment and measured polyethylene wear rates at specified cycle counts. The test demonstrated less wear than other joint replacements. Further clinical evaluation is necessary to determine if this translates into reduced complications of total elbow replacement associated with wear.