Electronic Thesis and Dissertation Repository


Doctor of Philosophy


Medical Biophysics


David W Holdsworth


Total knee arthroplasty (TKA) has become the gold standard approach for treating advanced osteoarthritis of the knee. Although the surgery continues to be very successful at relieving pain and restoring joint function, its longevity is challenged by wear and loosening of the implant components. This requires the patient to undergo a revision surgery to replace the implant, a much more challenging operation than primary arthroplasty. Wear of the polyethylene tibial inserts from TKA is assessed in vitro using mechanical wear simulator testing and by examining failed implants retrieved from patients during revision surgery, as well as with direct in vivo measurements. Current in vitro measurement tools provide only a global estimate of wear (failing to describe whether the wear has occurred on the articulating or backside surfaces, or stabilizing post), or are qualitative measurements, or lack resolution. Current in vivo measurement techniques are performed statically or quasi-statically, leading to the potential for an underestimation of wear volume as the contact area of the implant components change throughout flexion. The purpose of this thesis was to describe, validate, and utilize new advanced imaging techniques to measure TKA implant wear for both in vitro and in vivo applications. Micro-computed tomography (micro-CT), a non-destructive, high resolution imaging technique was utilized to provide detailed images of the geometry of tibial inserts used in wear simulator trials or retrieved from patients, and create surface deviation maps to accurately quantify wear. Ways to create an unworn reference geometry, for use in comparing to a worn retrieved tibial insert when the pre-wear geometry is unknown, were evaluated and a best practice approach was determined. These methods were then applied to study a group of tibial inserts retrieved from patients during revision surgery, which were found to be well functioning with a yearly wear rate equivalent to other contemporary implant designs. Finally, a pilot study to evaluate the use of dynamic single-plane flat panel digital radiography for use in measuring TKA implant wear in vivo was conducted. The system was determined to have a measurement accuracy and precision sufficient to begin a pilot clinical study with patients.