Wear characterization and contact surfaces analysis of menisci and femoral retrieved components in bi-condylar knee prostheses.

PURPOSE: Although total knee arthroplasty is a well-practiced surgical procedure, material properties and surface topography can contribute to the wear mechanisms and the implant failure. It has been advised that an increased femoral component's surface roughness of total knee prostheses may be a contributing factor to accelerated wear of the polyethylene menisci and eventually prosthesis failure. The aim of this study is to investigate the wear phenomena occurring on medial and lateral compartments of retrieved total knee arthroplasty in order to correlate the surface roughness vs. BMI, age at revision, and time in situ. METHODS: Qualitative visual analyses were performed on all the retrieved knee components to assess the damage due to the wear phenomena. Quantitative analysis includes surface characterization performed using optical apparatus to describe surface roughness and morphology on the retrieved femoral, tibial and polyethylene component. The Mann-Whitney statistical test was performed to correlate the medial vs. lateral condyle surface roughness of all explants with BMI, age at revision, and time in situ. RESULTS: Visual and topographical analysis showed damage along the entire zone of the sliding contact area. A statistical difference between medial and lateral condyle roughness was found on four prosthesis. No statistical significance was found between surface roughness measurements and patient BMI, age at revision, and time in situ. On the femoral components various scratches were observed in the anterior/posterior (AP) direction of all the fixed femoral components. A statistically significant difference between medial and lateral condyle was found on two mobile knee design (p = 0.03) and on two fixed design (p = 0.01). The results were discussed in the framework of the usual TKR loading conditions during the gait, and of knowledge on the bio-tribological behavior of the prosthetic joint. CONCLUSIONS: The visual and topographical analysis showed consistent damage patterns with respect to the main movements to which the prosthetic components are subjected and no statistical significance was found between surface roughness measurements and patient BMI, age at revision, and time in situ.

Custom-Made Total Talonavicular Replacement in a Professional Rock Climber: Functional Evaluation With Gait Analysis and 3-Dimensional Medical Imaging in Weightbearing at 5 Years' Follow-Up.

With the goal to restore ankle and foot function also in the long term, custom-made prostheses are becoming more frequently possible solutions for severe bone loss and avascular necrosis of the talus. A young professional rock climber was implanted with a custom-made talonavicular prosthesis, and short-term (30 months) assessment has been published. A thorough assessment at the intermediate term (60 months), with state-of-the-art gait and medical imaging analyses, is reported here. Level walking and more demanding motor tasks were analyzed with both a full-body and a multisegment foot protocol on the operated and contralateral limbs. Cone-beam computer-tomography was also used to obtain 3-dimensional (3D) position and orientation of bone models on the operated ankle. These models were also used for a 3D video fluoroscopy analysis, with the ankle in 3 joint positions at the extremes of motion. Distance map analysis was performed to check for possible changes over time of bone morphology and joint contact areas, in all 3 joint positions. Very satisfactory functional results were observed, with large and symmetric joint motion and physiological muscular recruitment even in demanding motor tasks. Distance map analyses revealed that very small morphologic and contact patterns changes occurred in the replaced ankle between 30 and 60 months. Concerns about possible wear of the cartilage in the tibial mortise are not yet supported by experimental evidence.