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Byline: Guoan Li, PhD (Bioengineering Laboratory, Department of Orthopaedic Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, gli1@partners.org); Ramprasad Papannagari, MS (Bioengineering Laboratory, Department of Orthopaedic Surgery, Massachusetts [...]

The movement of the knee joint consists of a coupled motion between the tibiofemoral and patellofemoral articulations. This study measured the six degrees-of-freedom kinematics of the tibia, femur, and patella using dual-orthogonal fluoroscopy and magnetic resonance imaging. Ten normal knees from ten living subjects were investigated during weightbearing flexion from full extension to maximum flexion. The femoral and the patellar motions were measured relative to the tibia. The femur externally rotated by 12.9 deg and the patella tilted laterally by 16.3 deg during the full range of knee flexion. Knee flexion was strongly correlated with patellar flexion ([R.sup.2]= 0.91 ), posterior femoral translation was strongly correlated to the posterior patellar translation ([R.sup.2] = 0.87), and internal-external rotation of the femur was correlated to patellar tilt ([R.sup.2]=0.73) and medial-lateral patellar translation ([R.sup.2]=0.63). These data quantitatively indicate a kinematic coupling between the tibia, femur, and patella, and provide base line information on normal knee joint kinematics throughout the full range of weightbearing flexion. The data also suggest that the kinematic coupling of tibia, femur, and patella should be considered when investigating patellar pathologies and when developing surgical techniques to treat knee joint diseases. [DOI: 10.1115/1.2803267] Keywords: kinematics, tibiofemoral joint, patellofemoral joint, coupled knee kinematics, knee joint motion

Background: The biomechanical functions of the anterolateral and posteromedial bundles of the posterior cruciate ligament over the range of flexion of the knee joint remain unclear. Hypothesis: The posterior cruciate ligament bundles have minimal length at low flexion angles and maximal length at high flexion angles. Study Design: Descriptive laboratory study. Methods: Seven knees from normal, healthy subjects were scanned with magnetic resonance, and 3-dimensional models of the femur, tibia, and posterior cruciate ligament attachment sites were created. The lines connecting the centroids of the corresponding bundle attachment sites on the femur and tibia represented the anterolateral and posteromedial bundles of the posterior cruciate ligament. Each knee was imaged during weightbearing flexion (from 0° to maximal flexion) using a dual-orthogonal fluoroscopic system. The length, elevation, deviation, and twist of the posterior cruciate ligament bundles were measured as a function of flexion. Results: The lengths of the anterolateral and posteromedial bundles increased with flexion from 0° to 120° and decreased beyond 120° of flexion. The posteromedial bundle had a lower elevation angle than the anterolateral bundle beyond 60° of flexion. The anterolateral bundle had a larger deviation angle than the posteromedial bundle beyond 75° of flexion. The femoral attachment of the posterior cruciate ligament twisted externally with increasing flexion and reached a maximum of 86.4° ± 14.7° at 135° of flexion (P < .05). Conclusion: These data suggest that there is no reciprocal function of the bundles with flexion, which is contrary to previous findings. The orientation of the anterolateral and posteromedial bundles suggests that at high flexion, the anterolateral bundle might play an important role in constraining the mediolateral translation, whereas the posteromedial bundle might play an important role in constraining the anteroposterior translation of the tibia. Clinical Relevance: These data provide a better understanding of the biomechanical function of the posterior cruciate ligament bundles and may help to improve the design of the 2-bundle reconstruction techniques of the ruptured posterior cruciate ligament. Keywords: posterior cruciate ligament; in vivo kinematics; posterior cruciate ligament reconstruction; double-bundle reconstruction, Double-bundle reconstruction of a ruptured posterior cruciate ligament (PCL) has increasingly attracted attention in the literature. (2),(9),(12),(30) A survey conducted by the Herodicus Society to assess the status of treatment [...]

Background: Recently, double-bundle anterior cruciate ligament reconstruction has been advocated. However, there are little data on the in vivo biomechanics of the anteromedial and posterolateral bundles of the anterior cruciate [...]

Background: Although anterior cruciate ligament deficiency has been shown to lead to joint degeneration, few quantitative data have been reported on its effect on soft tissue structures surrounding the knee [...]

Background: Recent follow-up studies have reported a high incidence of joint degeneration in patients with anterior cruciate ligament reconstruction. Abnormal kinematics after anterior cruciate ligament reconstruction have been thought to [...]

This study presents an optimized matching algorithm for a dual-orthogonal fluoroscopic image system used to determine six degrees-of-freedom total knee arthroplasty (TKA) kinematics in-vivo. The algorithm was evaluated using controlled conditions and standard geometries. Results of the validation demonstrate the algorithm's robustness and capability of realizing a pose from a variety of initial poses. Under idealized conditions, poses of a TKA system were recreated to within 0.02 [+ or -] 0.01 mm and 0.02 [+ or -] 0.03 deg for the femoral component and 0.07 [+ or -] 0.09 mm and 0.16 [+ or -] 0.18 deg for the tibial component. By employing a standardized geometry with spheres, the translational accuracy and repeatability under actual conditions was found to be 0.01 [+ or -] 0.06 mm. Application of the optimized matching algorithm to a TKA patient showed that the pose of in-vivo TKA components can be repeatedly located, with standard deviations less than [+ or -] 0.12 mm and [+ or -] 0.12 deg for the femoral component and [+ or -] 0.29 mm and [+ or -] 0.25 deg for the tibial component. This methodology presents a useful tool that can be readily applied to the investigation of in-vivo motion of TKA kinematics. [DOI: 10.1115/1.2205865]

Background: Previous studies of knee joint function after anterior cruciate ligament deficiency have focused on measuring anterior-posterior translation and internal-external rotation. Few studies have measured the effects of anterior cruciate [...]

Accurately determining in vivo knee kinematics is still a challenge in biomedical engineering. This paper presents an imaging technique using two orthogonal images to measure 6 degree-of-freedom (DOF) knee kinematics during weight-bearing flexion. Using this technique, orthogonal images of the knee were captured using a 3-D fluoroscope at different flexion angles during weight-bearing flexion. The two orthogonal images uniquely characterized the knee position at the specific flexion angle. A virtual fluoroscope was then created in solid modeling software and was used to reproduce the relative positions of the orthogonal images and X-ray sources of the 3-D fluoroscope during the actual imaging procedure. Two virtual cameras in the software were used to represent the X-ray sources. The 3-D computer model of the knee was then introduced into the virtual fluoroscope and was projected onto the orthogonal images by the two virtual cameras. By matching the projections of the knee model to the orthogonal images of the knee obtained during weight-bearing flexion, the knee kinematics in 6 DOF were determined. Using regularly shaped objects with known positions and orientations, this technique was shown to have an accuracy of O.1 mm and 0.1 deg in determining the positions and orientations of the objects, respectively.