Comparisons of In Vivo Three-Dimensional Kinematics of Minimally-Invasive and Patient-Specific Instrument Total Knee Replacements During Functional Activities

Total knee replacements (TKR) have been the main choice of treatment for alleviating pain and restoring physical function in advanced degenerative osteoarthritis (OA) of the knee. In recent years, interests in minimally invasive surgery TKR (MIS-TKR) have increased substantially in industry and between orthopedic surgeons and patients. Moreover, patient-specific instrumentation (PSI) was designed to replace the previous surgical instrumentations without the needs for the computer navigation system. PSI-TKR was a newly developed surgical technique, aiming to more accurately restore the knee axis of the TKR than previous approaches, and was conducted with the minimally invasive surgical approaches in general. Therefore, the purposes of the project were to measure the 3D kinematics of the TKR in vivo. The kinematic data of the knee for the patients with MIS-TKR and PSI-TKR after surgery six-monthly have been calculated during functional tasks , i.e. active knee extension, flexion and sit-to-stand. According to the results, The performances of MIS-TKR and PSI-TKR patients are regarded to be equal on the translation except on the M/L direction. However, the differences on the M/L direction were too slight to affect the movement clinically. To be mentioned, MIS-TKR didn’t externally rotate to represent the screw home mechanism as a normal knee. It could induce abnormal articular contact pattern to the plastic insert which might shorten the life cycle of the TKR. It is suggested that the anatomical pose of the TKR in the minimally invasive surgery should be dealt with much more care to avoid consistent lateral contact broken.