Registration of Knee Articulating Surface Utilizing a Portable Handheld Laser Scanner: A Cadaveric Study

Abstract

Image-based navigation systems for total knee arthroplasty (TKA) require intra-operative registration of anatomical landmarks to the pre-operative images. Unfortunately, this process is long, tedious, and involves multiple steps with an optical tracking probe to bony identify landmarks. We hypothesized that use of a handheld laser scanner can achieve an accurate and fast registration of the cartilage surface. Magnetic resonance imaging (MRI) scans were obtained for six cadavers and images were segmented to produce 3-dimenstional (3D) models of the articulating surface of the tibia and femur using commercial software (MIMICS, Materialise). A portable, hand-held laser scanner (E4D Technologies) was used to generate surface models of the same tibia and femur. An iterative closest point (ICP) algorithm was then used to align the handheld scans to the MRI scans. The accuracy of the registration fit was determined by the Root Mean Square (RMS) difference between the two surfaces. There were a total of 72 scans. All 6 cadaveric knees were successfully registered to their MRI images with <1mm mean RMS error. The mean time for successful registration was 54 +/- 24 seconds. The inter- and intra-observer reliability were 0.92 and 0.87 respectively. A handheld laser scanner can produce fast and accurate registration of the tibia and femur during a TKA. Registration was accurate within less than 1mm with multiple operators of different training. Further studies should assess in vivo accuracy of scanned bone topography and implant positioning compared to other technologies.