Three-dimensional in vivo patellofemoral kinematics and contact area of anterior cruciate ligament-deficient and -reconstructed subjects using magnetic resonance imaging.
ABSTRACT The purpose of this study was to test whether (1) the 3-dimensional in vivo patellofemoral kinematics and patellofemoral contact area of anterior cruciate ligament (ACL)-deficient knees are different from those of normal, contralateral knees and (2) ACL reconstruction restores in vivo patellofemoral kinematics and contact area.
Ten ACL-deficient knees and twelve ACL-reconstructed knees, as well as the contralateral uninjured knees, were tested. Magnetic resonance imaging was performed at full extension and 40 degrees of flexion under simulated partial weight-bearing conditions. Six-degrees of freedom patellofemoral kinematics, patellofemoral contact area, and contact location were analyzed by use of magnetic resonance image-based 3-dimensional patellofemoral knee models.
The patella in the ACL-deficient knees underwent significantly more lateral tilt during flexion (P < .05) and tended to translate more laterally (P = .083) than the patella in contralateral knees. After ACL reconstruction, no kinematic parameters were significantly different from those in contralateral knees. The patellofemoral contact areas of ACL-deficient knees at both the extended and flexed positions (37 +/- 22 mm(2) and 357 +/- 53 mm(2), respectively) were significantly smaller than those of contralateral knees (78 +/- 45 mm(2) and 437 +/- 119 mm(2), respectively) (P < .05). After reconstruction, the patellofemoral contact area of ACL-reconstructed knees in the extended position (86 +/- 41 mm(2)) was significantly larger (P < .05) than that of contralateral knees (50 +/- 34 mm(2)), but no difference was detected in the flexed position. Reproducibility of all patellofemoral kinematic parameters, contact centroid translation, and contact area showed coefficients of variation of less than 6.8%.
ACL injuries alter patellofemoral kinematics including patellar tilt and patellar lateral translation, but ACL reconstruction with hamstring or allograft restores altered patellar tilt. ACL injuries reduce the patellofemoral contact area at both the extended and flexed positions, but ACL reconstruction enlarges the patellofemoral contact area at extension and restores the normal contact area at low angles of flexion.
Level III, case-control study.
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ABSTRACT: Background Aberrant patellar tracking is thought to be an important risk factor in the pathogenesis of patellofemoral osteoarthritis. Anterior cruciate ligament deficiency and quadriceps muscle weakness are considered to be important contributing factors. However, data from in vivo experiments looking at dynamic patellar joint kinematics and muscle force are scarce. Therefore, the purpose of this study was to evaluate the effects of anterior cruciate ligament transection and loss of vastus medialis force on patellar tracking in the rabbit knee in vivo. Methods Eight skeletally mature New Zealand White Rabbits, weighing 6.0kg (0.6kg standard deviation) were used. The experimental trials consisted of active, concentric and eccentric movements of the knee joint (between 30 to 90° of flexion). Measurements were performed with the intact, the anterior cruciate ligament deficient, and the vastus medialis transected knee. Within each trial knee extensor forces were adjusted between measurements. Patellofemoral kinematics (shift, rotation) were quantified from high speed video. Findings Following anterior cruciate ligament transection, patellar tracking occurred more laterally, and caused a significant lateral rotation of the patella. The addition of vastus medialis transection did not alter patellar tracking or rotation significantly for any of the force-matched experimental conditions. Interpretation Our results suggest that the loss of the anterior cruciate ligament results in lateral patellar shift and rotation while the loss of vastus medialis muscle force does not affect patellar tracking or rotation in the anterior cruciate ligament deficient knee. Together with previously observed results that isolated vastus medialis weakness does not affect patellar tracking in the intact knee, we suggest that the current results should be considered carefully in future interpretations of knee extensor imbalance and more research is needed to describe the contribution of vastus medialis muscle strength to medial patellofemoral stability and confirm these results in the human knee.Clinical biomechanics (Bristol, Avon) 05/2014; DOI:10.1016/j.clinbiomech.2014.03.001 · 1.88 Impact Factor
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ABSTRACT: In total knee arthroplasty (TKA), the patella is significantly associated with range of motion and gait performance. Currently, no highly accurate methods are available that can measure the 3D in vivo behavior of the TKA patellar component, as the component is made of x-ray-permeable ultra-high molecular weight polyethylene. Previously, we developed a computer simulation that matches CT scan and unidirectional radiographic images using image correlations, and applied it to kinematic studies of natural and TKA knees. The examination of the measurement accuracy for the patellar bone of a fresh-frozen pig knee joint yielded a root mean square error of 0.2 mm in translation and 0.2° in rotation. In this study, we recruited four patients who had a TKA and investigated 3D movements of the patellar component during squatting. We could visualize the patellar component using the position of the holes drilled for the component peg, and estimated and visualized the contact points between the patellar and femoral components. The principles and the utility of the simulation method are reported. This analytical method is useful for evaluating the pathologies and post-surgical conditions of the knee and other joints. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.Journal of Orthopaedic Research 05/2014; 32(5). DOI:10.1002/jor.22596 · 2.97 Impact Factor
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ABSTRACT: Mechanics play a role in the initiation and progression of osteoarthritis. However, our understanding of which mechanical parameters are most important, and what their impact is on the disease, is limited by the challenge of measuring the most important mechanical quantities in living subjects. Consequently, comprehensive statements cannot be made about how mechanics should be modified to prevent, slow or arrest osteoarthritis. Our current understanding is based largely on studies of deviations from normal mechanics caused by malalignment, injury, and deformity. Some treatments for osteoarthritis focus on correcting mechanics, but there appears to be scope for more mechanically based interventions.Rheumatic Disease Clinics of North America 02/2013; 39(1):21-44. DOI:10.1016/j.rdc.2012.11.002 · 1.74 Impact Factor