Three-dimensional motion analysis of the human knee joint: comparison between intra- and post-operative measurements

To compare intra-operative knee joint kinematic measurements immediately after total knee replacement with those of the same patients post-operatively at 6-month follow-up.

Fifteen patients who underwent total knee arthroplasty were analysed retrospectively. Eight were implanted with one prosthesis design and seven with another. The intra-operative measurements were performed by using a standard knee navigation system. This provided accurate three-dimensional positions and orientations for the femur and tibia by corresponding trackers pinned into the bones. At 6-month follow-up, the patients were analysed by standard three-dimensional video-fluoroscopy of the replaced knee during stair climbing, chair rising and step-up. Relevant three-dimensional positions and orientations were obtained by an iterative shape-matching procedure between the silhouette contours and the CAD-model projections. A number of traditional kinematic parameters were calculated from both measurements to represent the joint motion.

Good post-operative replication of the intra-operative measurements was observed for most of the variables analysed. The statistical analysis also supported the good consistency between the intra- and post-operative measurements.

Intra-operative kinematic measurements, accessible by a surgical navigation system, are predictive of the following motion performance of the replaced knees as experienced in typical activities of daily living.

Prognostic studies—investigating natural history and evaluating the effect of a patient characteristic, Level II.