J. Mandume Kerina, MD, of Leesburg (Fla.) Regional Medical Center, has performed hundreds of mobile and fixed bearing partial knees, taught countless surgeons in both techniques as a surgeon educator and lately has led a team of experts in detailing the road map for the next generation of UKA, the MOTO Partial Knee System. Both mobile and fixed bearing implants have been highly successful, yet each has room for improvement. The team’s mission was simple: make today’s unicompartmental knee arthroplasty that serves all patients, from elderly to high-demand, in all sizes ranging from the petite to the professional athlete, and is well suited for today’s ASCs with efficient trays and no requirement for expensive robotic technologies.
So, why MOTO? Aside from implant design, instruments and education are key components.
The design rationale required a compartment-specific approach. The MOTO implants are designed for each specific compartment using an anthropometric database of thousands of knee CT scans to optimize anatomic coverage, contours, size range and precise fit. MOTO is a cemented fixedbearing UKA, using proven materials.
The Co-Cr-Mo femoral component comes in 10 sizes; the titanium alloy (Ti-Al6-V4) tibial tray comes in eight sizes, and the high-quality polyethylene insert in single-millimeter incremental thicknesses. It is a round-on-flat design that minimizes shear stress on the implants, and allows for all femoraltibial size combinations. The femoral component is anatomic, with anatomic posterior femoral condyle coverage for deep flexion. It has cement interdigitation recesses, and two pegs which diverge from the posterior flange for secure fixation (three pegs on largest sizes). Likewise, the tibial tray has the cement interdigitation recesses, two pegs and a keel.
Perhaps the most distinguishing feature of MOTO is the instrumentation that allows for precise bone resections to balance knee flexion-extension gap mismatch, while maintaining slight alignment under-correction. UKA is unique in that the implants must be placed within a given soft tissue envelope specific to that knee, without ligament releases, and still achieve balance and alignment goals. This requires precise (1 mm) bone resections on the tibia, distal femur and posterior femoral condyle. MOTO enables the surgeon to independently adjust flexion and extension gaps, and allows the surgeon to change any step all the way up to cementation. Even the medial-lateral positioning of the femoral component can be changed after trial reduction to optimize positioning. All femoral components have the same two lug holes, distal and posterior cuts, enabling a change in femoral component sizing even after the cuts and lug drill holes were made.
The Medacta commitment to surgeon education is a key component to the success of MOTO. Surgeons benefit from one-on-one instruction and proctoring as well as visiting design surgeons and attending learning centers for didactics and cadaver lab training.
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