Comparing three attachment systems used to determine knee kinematics during gait

This work compared three attachment systems (AS) designed to minimize soft tissue artefacts in gait analysis measurements. The systems’ displacement for different knee flexion angles and after 50 gait cycles was investigated using an EOS® low dose biplanar X-ray system. Eighteen subjects (six per AS) were equipped with one AS and placed in five positions. Frontal and profile views were taken for each position. The bones’ 3D model and the AS's position were obtained from stereoradiographic reconstructions. The AS's relative position to the underlying bone were computed and interpreted in the anatomical coordinate systems (CS).The AS appeared to be stable in the frontal and sagittal plane (under 1.5° average displacement around the underlying bones) but unstable in the axial plane (over 6° average displacement). The average translation along the femoral and tibial diaphysis was 4.5 mm and 2.7 mm, respectively. Femoral system B translated significantly less along the diaphysis than the other AS. Concerning the axial rotation, system C appeared to present the most important displacement but there was no statistically significant difference. Systems A and B's rotation in the transverse plane correlated to the knee flexion angle. For the tibia, system B was more stable than systems A and C (p = 0.04). On the whole, system B appeared to be the most stable system. This study highlights the fact that no system can limit displacement in the transverse plane.