Clinical assessment methodology for the in-vivo measurement of pain and discomfort in patients with standard metal and PEEK total knee replacement

Total knee replacement represents the main solution to treat end-stage osteoarthritis. The procedure can vastly impact the surrounding structures of the joint, impairing its functionality and stability. Various complications may follow the surgery: pain, discomfort, soreness, stiffness, infection, and swelling. They can be evaluated through specific diagnostic tools. The purpose of this thesis is to study the possible non-invasive methodologies and develop a clinical protocol to compare different prosthetic implants and materials. The analysed solutions are the conventional metal alloy (CoCr) device and a newly developed polymeric (PEEK) femoral insert. Two distinct tools are introduced to evaluate joint swelling and superficial temperature: Bioelectrical Impedance Analysis (BIA) and Infrared Thermography (IR). These factors can vastly undermine knee functionality: an unsuccessful treatment can accelerate the deterioration and wear rate of the articular surfaces. An assessment protocol is developed for both techniques to investigate the variations of the selected parameters. Daily life stress conditions are simulated to analyse the typical response of the prosthetic implant. The recorded data are confronted with thresholds from the literature. A feasibility test is also performed on three healthy subjects to explore the reliability of a BIA-based follow-up in standard conditions and with local ice application on the knee joint. The evaluated parameters are resistance, reactance, and phase angle. The obtained average ICC values are 0.93, 0.87, and 0.50, respectively. The results show an excellent accuracy and sensitivity to small variations of fluid accumulation. No differences (p>0.05) are found regarding the local ice application in the different time frames. This approach may represent a promising and viable alternative in the follow-up of TKA patients. Further studies are needed to investigate the range of application of the two techniques.