Cementless Total Knee Arthroplasty has been developed to reduce the incidence of failure secondary to aseptic loosening, osteolysis and stress-induced osteopenia, especially in younger and more active patients. However, failures are still more common compared to cemented components, especially those involving the tibia. It is hypothesized that this is caused by incomplete contact between the tibial tray and the underlying bony surface due to: (i) inadequate flatness of the tibial osteotomy, or (ii) failure of implantation to spread the area of contact over the exposed cancellous surface. In the present study we compare the contact area developed during implantation of a cementless tray as a function of the initial flatness of the tibial osteotomy. Eight joint replacement surgeons prepared 14 cadaveric knees for cementless TKR using a standard instrumentation set (ZimmerBiomet Inc). The tibial osteotomy was created using an oscillating bone saw and a 1.27mm blade (Stryker Inc) directed by a slotted cutting guide mounted on an extramedullary rod and fixed to the tibia with pins and screws. The topography of the exposed cancellous surface was captured with a commercial laser scanner (Faro Inc, Halifax, approx. 33,000 surface points). 3D computer models of each tibial surface were generated in a CAD environment (Rapidform, Inuus). After scanning, a cementless tibial tray was implanted on the prepared tibial surface using a manual impactor. The tray-tibia constructs were dissected free of soft tissue, embedded in mounting resin, and sectioned with a diamond wafering saw. Points of bone-tray contact and interface separation were identified by stereomicroscopy and incorporated in the 3D computer models. Maps were generated depicting contacting and non-contacting areas Each model was subdivided into 7 zones for characterizing the distribution of interface contact in terms of anatomic location.Background
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