Loss of Cement-Bone Interlock during In Vivo Service of Total Knee Replacements

The morphology of the cement-bone interface from total knee replacements was investigated as a function of time in service. Ten post-mortem retrievals and one lab-prepared specimen were sectioned and imaged with high-resolution microscopy. Stereology was used to quantify contact fraction and interdigitation depth. The results show that loss of fixation occurs by resorption of trabeculae that interlock with cement. This occurs early after implantation (1-2 years). Donor bones with better initial interlock maintain interlock better in the short term. The results suggest that loss of interlock between cement and bone could be a factor contributing to aseptic loosening.