Assessment of knee implant alignment using coordinate measurement on three-dimensional computed tomography reconstructions

The rapid development of navigation systems designed to improve implant alignment calls for precise methods to verify positioning. One new approach to assess knee implant alignment is coordinate measurement (CM) using reference objects on 3-dimensional reconstructions of computed tomographic (CT) image sequences. The objectives of this study were to determine whether implant alignment can be accurately and precisely examined with CT-based CM, and whether correct positioning of a transversal support implant can be attained using a specially developed aiming instrument. Average deviation of CT measurements from those made with a digital caliper remained within the caliper's range of error. This level of accuracy was observer independent. CT-based CM can be used for accurate and precise alignment verification. As well, precise alignment of transversal support can be achieved during implantation with a conventional aiming device, assuming the bony landmarks are appropriately recognized.