Wear of congruent meniscal bearings in unicompartmental knee arthroplasty - A retrieval study of 16 specimens

Many designs of unicompartmental knee replacement show early and mid-term f ailure due to polyethylene wear. We studied the wear rate of congruent poly ethylene meniscal bearings retrieved from failed Oxford unicompartmental kn ee replacements, We examined 16 bearings, 0.8 to 12.8 years after implantation, measuring th eir thickness and comparing it with that of 14 unused bearings. The mean ra te of penetration, which included the effects of wear at both upper and low er surfaces, was 0.036 mm per year (maximum 0.08). Bearings as thin as 3.5 mm wore no faster than thicker models, but ten with evidence of impingement had greater wear. The six bearings with no impingement showed a mean rate of penetration of 0.01 mm psr year, In unicompartmental knee replacement, careful implantation of fully congruo us meniscal bearings can avoid failure due to polyethylene wear.