Strain Distribution in the Tibia as a Function of Applied Loading through a Revision Total Knee Replacement

Abstract

The growth in primary total knee replacement procedures coupled with changes in patient demographics and life expectancy has led to corresponding growth in revision total knee replacements. Revision components usually include intramedullary stems to aid fixation and manage bone stock deficiencies. Stemmed tibial components are thought to have an adverse effect on load transfer, contributing to complications in revision knee replacement. Current in vitro testing rarely incorporates physiological loading which considers the compartmental load share across the tibial plateau or includes the patellofemoral joint.A robust experimental test protocol was developed to assess the effect of the applied loading on strain distribution in the tibia for the evaluation of stemmed revision tibial components. A tibiofemoral loading rig was developed to incorporate compartmental load distribution. This increased the confidence in the strain distribution results, but did not include potential effects of the load transfer associated with the patellofemoral joint. A combined loading rig included the force transferred through both the tibiofemoral and patellofemoral joints. It was therefore possible to compare the results from this rig to those of the tibiofemoral rig whilst allowing testing at higher flexion angles.Investigations were conducted into the effect of applied loading on strain distribution through the tibia. The results demonstrate that implanting a revision tibial component, increasing the flexion angle and including the patellofemoral joint all reduce the principal compressive strains through the tibia. However, below the stem tip the compressive strains significantly increased following implantation of the tibial component. This research has demonstrated the issues with a current component design, which contribute to proximal strain shielding and end of stem pain linked to distal strain concentrations. A novel test methodology has been developed which better simulates physiological loading and can be used in future pre-clinical evaluation of revision total knee implants.

Date of Award	6 Oct 2015
Original language	English
Awarding Institution	University of Bath
Supervisor	Tony Miles (Supervisor) & Sabina Gheduzzi (Supervisor)