Characterisation of wear areas on UHMWPE total knee replacement prostheses through study of their areal surface topographical parameters

Total knee replacement is one of the most common elective surgeries in the world, and presents a number of challenges related to the wear of ultra-high molecular weight polyethylene (UHMWPE). This paper presents an analysis of the surface topographical properties of the worn and unworn condylar surfaces on a small cohort of both wear simulated and retrieved prostheses of varying designs. A number of measurement points were taken on each prostheses in a mixture of worn and unworn areas through the use of focus-variation microscopy (FVM), a non-contact method of surface measurement. Surface areal parameters were extracted from this data to analyse and search for patterns within the data. It was found that in general, worn implant surfaces appear to show smoother, less peak dominated surfaces than unworn area. It was also found that wear simulated and retrieved implants display similar characteristics of surface topography. In addition, variation was noted between different designs of TKR device, with posterior stabilised designs found to be peak dominated and cruciate retaining type implants being valley dominated.