KS47: MINIMALLY INVASIVE IMAGELESS COMPUTER NAVIGATED KNEE SURGERY: INITIAL RESULTS

Abstract

Background: The combination of imageless computer aided navigation and minimally invasive surgery for total knee arthroplasty (TKA) has not been reported. Computer Aided Surgery (CAS) of the knee has demonstrated more reproducible component alignment compared to standard instrumentation. Minimally Invasive Surgery (MIS) for total knee arthroplasty allows for quicker rehabilitation and less post-operative pain. However, MIS has been associated with a higher complication rate, including component malalignment, compared to a conventional operative approach. Both MIS and CAS have been demonstrated to have a learning curve.

Aims: This study presents the initial 30 procedures in which imageless CAS was combined with MIS for TKA by the senior author. Specifically, we examined the accuracy of coronal alignment and the learning curve associated with the combined technique.

Between 6 and 12 weeks full length weight bearing radiographs were taken when patients could achieve full extension. Coronal alignments of the tibial and femoral components were calculated relative to the mechanical axis. The goal for both femoral and tibial component alignment was within 30 of 900 to the mechanical axis. The results were verified by an independent observer. Analysis of sequential tourniquet times, complication rates and component alignment were used as measure of the learning curve for the technique.

Component position was acceptable for all implants. The mean coronal tibial alignment was 90.35 degrees (range 88 to 92 degrees) and the mean coronal femoral alignment 90.10 degrees (range 88 to 93 degrees) to the mechanical axis. Tourniquet time averaged 90 minutes (range 60 to 118 minutes). There was no significant reduction in tourniquet time with increasing familiarity with the technique. Our results demonstrate that CAS combined with MIS for TKA maintains the accuracy of component alignment despite the minimally invasive approach. These initial results demonstrate no significant learning curve associated with the technique.