Background: An alternative tri-condylar implant has been designed to incorporate necessary posterior stability without a post, but has not been evaluated. The purpose of the current study was to determine the in vivo three dimensional femoro-tibial kinematics of a tri-condylar implant during a weight bearing deep knee bend activity.
Methods: Fluoroscopy based in vivo femoro-tibial kinematics of the tri-condylar implant was assessed for 66 knees during a deep knee bend activity, using a three dimensional to two dimensional model fitting approach.
Findings: Average range of motion was 125.5° (standard deviation (SD)=20.5°) in sagittal plane, and 42 knees (63.6%) experienced at least 120° of weight-bearing knee flexion. The average amount of posterior femoral movement (PFM) was 8.7mm (SD=4.3mm) for the medial condyle and 11.2mm (SD=5.4mm) for the lateral condyle. PFM of the medial condyle was significantly smaller than that of the lateral condyle. The average amount of femoro-tibial axial rotation was 5.7° (SD=6.4°), and 56 knees (84.8%) experienced a normal axial rotation pattern. Condylar lift-off, mostly occurring in deep flexion range, was experienced in 16 knees (24.2%).
Interpretation: Knees in the current study did achieve high weight-bearing flexion, more normal-like greater posterior femoral movement of lateral condyle than the medial condyle and a normal axial rotation pattern, albeit, less in magnitude than the normal knee.
Keywords: Deep knee flexion; Fluoroscopy; Knee kinematics; Total knee arthroplasty; Tri-condylar implant.
Copyright © 2014 Elsevier Ltd. All rights reserved.