Comparison of a Novel Joint Distraction Radiology Protocol in Total Knee Arthroplasty Planning with Navigated Joint Gaps

Native extension and flexion joint gaps are primarily measured intraoperatively using devices such as navigation systems or tensioners, but there are advantages to being able to pre-operatively plan to such gaps. This study aims to validate the ability of a novel distracted joint gap radiology protocol to measure pre-operative extension andflexion joint gaps. A retrospective study comprised of 42 knees was performed. Patient imaging was obtained and used to perform segmentation, landmarking and 3D-to-2D registration. The pre-operative medial and lateral joint gaps were determined in extension and flexion. Intraoperatively, a range of motion analysis was conducted using the Brainlab Knee 3 navigation system to measure the joint gaps in extension and flexion.In extension, both medial and lateral pre-operative radiological and intraoperative navigated gaps displayed moderate and statistically significant correlations (r=0.45; p=0.003 for medial and r=0.4; p=0.01 for lateral). In flexion, only the medial radiological and navigated joint gaps correlated (r=0.54, p<0.001), with a not statistically significant trend for the lateral flexion joint gaps.The moderate and statistically significant correlations between these joint gaps to those measured intraoperatively suggests they are reflective of on the table experience with patients. Although further work is required to understand if differences are attributable to variability in the radiological or intra-operative assessments, the pre- operative analysis technique described in this study provides the opportunity to develop a more holistic pre-operative surgical plan which considers the state of both hard and soft tissue within the joint.