Correlation of compartment pressure data from an intraoperative sensing device with postoperative fluoroscopic kinematic results in TKA patients

Fluoroscopy has recently been used to analyze postoperative kinematics in total knee arthroplasty (TKA). These analyses have reported varying results even in patients with similar implant design. In addition, patterns of wear in retrieved tibial polyethylene inserts of similar design have been found to vary substantially. These findings suggest that surgical technique, especially soft tissue balancing, may play a role in postoperative kinematics and implant failure. Accurate soft-tissue balancing is hypothesized to result in similar pressures within the medial and lateral compartments of the knee. However, a method of easily measuring these pressures at TKA has not been developed. In the present study, 32 patients were implanted with a mobile-bearing LCS TKA utilizing the balanced gap technique. An electronic pressure sensor, developed specifically to record pressure magnitude and distribution in the medial and lateral compartments, was incorporated into the implant trials. The knee was then passively taken through a range of motion while pressure data was recorded via computer. Postoperatively, 16 patients underwent active fluoroscopic kinematic analysis to assess for condylar liftoff and femorotibial translation. We found that abnormal compartment pressures and distributions as recorded by the intraoperative pressure sensor were correlated with inappropriate or paradoxical postoperative kinematics. In addition, subjects having similar pressures in both compartments throughout a range of motion did not experience condylar liftoff values greater than 1.0 mm. These data suggest that surgical technique influences the magnitude and distribution of forces at the articulation, postoperative kinematics, and likely, implant longevity.