Retropatellar complications after total knee arthroplasty (TKA) such as anterior knee pain and subluxations might be related\nto altered patellofemoral biomechanics, in particular to trochlear design and femorotibial joint positioning. A method was\ndeveloped to test femorotibial and patellofemoral joint modifications separately with 3D-rapid prototyped components for in\nvitro tests, but material differences may further influence results. This pilot study aims at validating the use of prostheses made\nof photopolymerized rapid prototype material (RPM) by measuring the sliding friction with a ring-on-disc setup as well as knee\nkinematics and retropatellar pressure on a knee rig. Cobalt-chromium alloy (standard prosthesis material, SPM) prostheses served\nas validation standard. Friction coefficients between these materials and polytetrafluoroethylene (PTFE) were additionally tested\nas this latter material is commonly used to protect pressure sensors in experiments. No statistical differences were found between\nfriction coefficients of both materials to PTFE. UHMWPE shows higher friction coefficient at low axial loads for RPM, a difference\nthat disappears at higher load. No measurable statistical differences were found in knee kinematics and retropatellar pressure\ndistribution. This suggests that using polymer prototypes may be a valid alternative to original components for in vitro TKA studies\nand future investigations on knee biomechanics.
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