The Effects of Femoral Fixed Body Coordinate System Definition on Knee Kinematic Description

Abstract

Understanding the differences in knee kinematic descriptions is important for comparing data from different laboratories and observing small but important changes within a set of knees. The purpose of this study was to identify how differences in fixed body femoral coordinate systems affect the described tibiofemoral and patellofemoral kinematics for cadaveric knee studies with no hip present. Different methods for describing kinematics were evaluated on a set of seven cadaveric knees during walking in a dynamic knee simulator. Three anatomical landmark coordinate systems, a partial helical axis, and an experimental setup-based system were examined. The results showed that flexion-extension was insensitive to differences in the kinematic systems tested, internal-external rotation was similar for most femoral coordinate systems although there were changes in absolute position, varus-valgus was the most sensitive to variations in flexion axis direction, and anterior-posterior motion was most sensitive to femoral origin location. Femoral coordinate systems that define the sagittal plane using anatomical landmarks and locate the flexion axis perpendicular to the femur's mechanical axis in the frontal plane were typically similar and described kinematics most consistently.

Evaluation of automated statistical shape model based knee kinematics from biplane fluoroscopy

“…the flexion parameter in Figure 7). Coordinate-system definitions may greatly influence the results (Lenz et al, 2008), but analyzing the effect is outside the scope of this paper.…”

In vivo sagittal plane kinematics of the FPV patellofemoral replacement

“…The PTA was measured as the angle subtended between the long axis of the tibia and the line along the length of the patellar tendon, the PFA as the angle between the axis passing through the distal and proximal poles of the patella and the femoral axis, and the KFA as the angle subtended between the long axes of the femur and tibia [18, 26]. To measure the PTA, PFA, and KFA, a user interface was developed in Matlab (version 7.0, The MathWorks, MA, USA), which allowed interactive templating of the tibial axis, femoral axis [26], tibial tubercle, distal pole of the patella, and the proximal pole of the patella (Fig.…”

Fully automatic extraction of knee kinematics from dynamic CT imaging; normative tibiofemoral and patellofemoral kinematics of 100 healthy volunteers

“…Secondly, the choice of coordinate system has a major influence on the kinematic description [8,16,28,29]. The choice of coordinate system together with natural variation in anatomy and pose are a possible explanation for offsets, or different starting positions and orientations [23]. The absolute numbers from this study, may therefore not by directly comparable to studies where other coordinate systems are used.…”

“…Whereas there is little to no valgus rotation of the tibia in the studies of Seisler & Sheehan, our data suggests a median varus alignment of 5°at 85°of TF flexion. This difference may be caused by the use of different coordinate systems, where a valgus rotated, or externally rotated femoral ML axis causes a more valgus description during knee flexion [23].…”