A QUANTITATIVE TECHNIQUE FOR REPORTING SURFACE DEGRADATION PATTERNS OF UHMWPE COMPONENTS OF RETRIEVED TOTAL KNEE REPLACEMENTS

A quantitative method of reporting surface degradation of the ultra-hi gh molecular weight polyethylene (UHMWPE) tibial component from retrie ved total knee replacements (TKR) was developed. Specific features inc lude a qualitative assessment expressing the patterns in which the dam age was detected as well as a quantitative summary of the observed deg radation mechanisms. In addition, a method of measuring lower limb ali gnment changes with time is described and related to the observed dama ge patterns. Two case studies are presented. One case illustrated that changes in alignment resulted from factors other than wear. The damag e observed on the tibial plateau appeared to occur subsequent to the c hanges in alignment. The second case illustrated that the wear of the UHMWPE tibial insert lead to the changes in the overall lower limb ali gnment. The methods described provide additional information regarding TKR failure mechanisms compared to reporting methods currently availa ble. In particular, the collection of temporal alignment data at clini cal follow-up visits enhanced the assessment of the retrieved TKR. (C) 1995 John Wiley and Sons, Inc.