The ability of tibial tray component shapes to appropriately fit boney geometry is an important aspect of implant design in total knee arthroplasty. Overhang of components in the knee has been associated with soft tissue damage and joint pain [1,2]. Good coverage establishes stability through adequate cortical bone support of the tray component, and reduces the likelihood of loosening and subsidence [3–5], and therefore serves as a key factor in component fixation, especially in those that rely on biological growth into porous component backings such as Trabecular Metal™ Material. More importantly, rotational malalignment of the tibial tray can disrupt the natural kinematics and implant longevity [6]. Previous studies investigated coverage of multiple tibial trays on digitized bone resection contours [1,7]. However the methodology for rotational alignment during implantation was not identified. Although rotational alignment has been investigated in numerous studies, most of the studies were carried out by either investigating the impact of malalignment [6], or assessing different definitions of the tibia rotational axis [8]. No correlation between the size of the rotational alignment window and the amount of coverage has been shown.

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