A method for the measurement of joint kinematics from dynamic magnetic resonance imaging data and its application to the study of the anterior cruciate ligament deficient human knee

Approximately 80,000 ruptures of the anterior cruciate ligament (ACL) occur annually in the United States. Most require reconstructive surgery to restore knee stability (non-topers). ACL reconstruction is expensive, and the development of osteoarthritis in the long term is reported in some patients. A small percentage of ACL injured individuals who elect non-operative treatment are able to resume activities without apparent deficit (topers). To investigate the effectiveness of reconstructions, as well as the reasons for the improved function of topers, precise measurements of knee joint kinematics during activity are needed. A novel method (the tine-PC rigid body tracking/RBT method) for the noninvasive measurement of knee kinematics from tine phase contrast magnetic resonance imaging data was developed. A validation study was performed using a specially developed device; average RMS accuracies for anterior/posterior position and axial rotation were measured as 2.82 mm and 2.63°. A human subjects repeatability study produced RMS differences in anterior/posterior position and axial rotation of 1.44 mm and 2.35°. The kinematics in 16 ACL deficient pre-operative non-topers and 16 uninjured control subjects were then compared. Non-copers exhibited more anterior positioning of the tibia in the injured knees relative to the control knees, as well as trends of increased rates of anterior tibial translation and decreased external tibial rotation. Subsequently, kinematics in three groups of nine subjects (control subjects, topers, and non-topers) were compared. The findings in the non-topers and controls were largely repeated in this study. The injured knees of topers did not exhibit anterior tibial subluxation, but did show some evidence of increased tibial translation and decreased external tibia] rotation. The copers' results were generally more variable but on average intermediate to those from the controls and non-copers. The results of the studies supported the decision of surgical reconstruction of the ACL to limit pathological motion in the non-copers. The previously observed diminished impairment of quadriceps function was proposed to be the cause of the overall more normative results of the copers; however, the increased variability of their results warrants further investigation of specialized strategies used by individual copers to maintain knee stabilization.