Total hip replacement is a human surgical intervention with the aim of pain relief and function restoration, with a survival rate of ≥ 90% at ten years. Currently, imaging techniques are the primary diagnostic and follow-up method, but are unreliable for early loosening detection. Vibrometry has been proposed as an alternative, more sensitive method for loosening diagnosis.Despite the fact that acetabular cups have a higher revision rate over femoral components, most of the existing vibrometry literature is stem related. A limited number of studies have examined cup loosening without defining the loosening level detected. Hence, the present study aimed to investigate the feasibility of detecting acetabular cup loosening using vibrometry, and to define the earliest loosening phase that could be accurately detected. Three objectives were devised to address this aim. Firstly, a simplified set-up with minimal boundary conditions utilising Sawbones blocks. Secondly, a complex bone geometry was examined by utilising a Sawbones hemi-pelvis, and thirdly a more clinically relevant experiment was tested by using a composite femur and hemi-pelvis. Loosening was demonstrated by a reduction in the fundamental frequency and an increase in the magnitude of the related harmonics. By quantifying the magnitude of the harmonics in relation to the fundamental frequency, it was found that the harmonic ratio would increase, corresponding to the degree of loosening. These findings support the existing vibrometry literature. In the first objective the minimum detected simulated loosening was 1mm zone 2 loosening within the frequency range 2000-2500Hz. For the second and third objectives this was 1mm spherical acetabular cup loosening within the range 500-1500Hz. Hence, the study suggests that vibrometry has the potential to diagnose early acetabular cup loosening. This study is therefore novel because it has defined the minimum acetabular cup loosening level that can be reliably detected, alongside the favourable frequency range.
|Date of Award||27 Oct 2016|
|Supervisor||James Cunningham (Supervisor) & Tony Miles (Supervisor)|