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Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_34 | Pages 428 - 428
1 Dec 2013
Loss of Cement-Bone Interlock With in Vivo Service in Total Knee Replacement
Mann K Miller M Goodheart J Izant TH Rimnac C Cleary R
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INTRODUCTION:

Aseptic loosening continues to be a short and long-term complication for patients with cemented knee replacements. Changes in cemented total knee replacement (TKR) fixation have been limited to assessment of radiographic changes at the implant-bone interface and quantification of component migration. The goal of this study was to determine the interlock morphology between cement and trabecular bone using en bloc postmortem retrieved TKR. Note that these retrievals were not obtained from revision surgery for a loose implant, but rather after death. Thus the implants can be considered successful for the lifetime of the patient. We hypothesized that constructs with greater time in service have less interlock between cement and bone and constructs with more estimated initial interlock sustain more interlock with in-vivo service.

METHODS:

Twelve retrieved tibial components and two lab-prepared constructs with time in service from 0 to 20 years were sectioned in the transverse plane in 10 mm increments, imaged at high resolution, and the current contact fraction (curCF), estimated initial interdigation depth (inID), current interdigitation depth (curID), and loss of interdigitation depth (lossID) were quantified at the cement-bone interface. Contact fraction was determined using a stereology method using random ray projections (Figure 1A). The trabecular shape cast into the cement layer upon curing was used to document the initial penetration of bone into the cement. A line tracing algorithm was used to determine interdigiation depth (Figure 1B).