Evaluation of True Ankle Motion Following Total Ankle Replacement Utilizing XROMM technology

Abstract

Introduction/Purpose: Total ankle replacement (TAR) is common tool used by the foot and ankle specialist to treat end-stage ankle arthritis. Current data about ankle motion following TAR are derived from gait analysis utilizing external markers. Utilizing x-ray reconstruction of moving morphology (XROMM), which combines 3D mapping technology with biplanar fluoroscopy in vivo to visualize true skeletal motion, we can evaluate true motion of TAR implants. Current TAR replacement systems are either mobile bearing or fixed bearing. We hypothesized that subjects implanted with a fixed bearing prosthesis would exhibit less tibiotalar rotation and translation than subjects implanted with a mobile bearing prosthesis. Method(s): Six subjects with total ankle replacement at least 1 year postimplantation gave informed consent before participating (IRB #H16496). Three subjects with a mobile bearing prosthesis with an average age 63.3 +/- 11.1 years were compared to 3 matched subjects with a fixed bearing prosthesis with an average age of 64.7 +/- 1.5 years. Utilizing 3D slicer software, lower body CT scans for each subject were evaluated to create 3D models of the foot and ankle bones and implant components. All subjects walked for several trials at a self-selected pace along a walkway while their foot and ankle motions were captured by a high-speed biplanar fluoroscopic x-ray motion analysis (XMA) system. The 3D models were combined with the x-ray images within a 3D animation platform and rotoscoped to resolve accurate kinematic motions at the tibiotalar joint during stance phase of gait. We examined for differences between the 2 groups using a 2-sample t test (P