Use of a Novel Multimodal Imaging Technique to Model In Vivo Quadriceps Force and ACL Strain During Dynamic Activity

Abstract

Background: Quadriceps loading of the anterior cruciate ligament (ACL) may play a role in the noncontact mechanism of ACL injury. Musculoskeletal modeling techniques are used to estimate the intrinsic force of the quadriceps acting at the knee joint. Purpose/Hypothesis: The purpose of this paper was to develop a novel musculoskeletal model of in vivo quadriceps force during dynamic activity. We used the model to estimate quadriceps force in relation to ACL strain during a single-leg jump. We hypothesized that quadriceps loading of the ACL would reach a local maximum before initial ground contact with the knee positioned in extension. Study Design: Descriptive laboratory study. Methods: Six male participants underwent magnetic resonance imaging in addition to high-speed biplanar radiography during a single-leg jump. Three-dimensional models of the knee joint, including the femur, tibia, patellofemoral cartilage surfaces, and attachment-site footprints of the patellar tendon, quadriceps tendon, and ACL, were created from the magnetic resonance imaging scans. The bone models were registered to the biplanar radiographs, thereby reproducing the positions of the knee joint at the time of radiographic imaging. The magnitude of quadriceps force was determined for each knee position based on a 3-dimensional balance of the forces and moments of the patellar tendon and the patellofemoral cartilage contact acting on the patella. Knee kinematics and ACL strain were determined for each knee position. Results: A local maximum in average quadriceps force of approximately 6500 N (8.4× body weight) occurred before initial ground contact. ACL strain increased concurrently with quadriceps force when the knee was positioned in extension. Conclusion: This novel participant-specific modeling technique provides estimates of in vivo quadriceps force during physiologic dynamic loading. A local maximum in quadriceps force before initial ground contact may tension the ACL when the knee is positioned in extension. Clinical Relevance: These data contribute to understanding noncontact ACL injury mechanisms and the potential role of quadriceps activation in these injuries.

The Predicted Position of the Knee Near the Time of ACL Rupture Is Similar Between 2 Commonly Observed Patterns of Bone Bruising on MRI: Response

“…We believe that our previous work using imaging techniques to quantify in vivo ACL elongation and joint motion supports the findings of the present study, in that the previous studies suggested that knee extension elevates ACL strain 2-6,8,9,22-24 and puts the ligament at increased risk for injury. As noted previously, these techniques have advantages over cadaveric studies, which may not accurately reproduce in vivo loading conditions, 7 and videographic techniques, which may be susceptible to errors due to the viewpoint of the camera 3 and skin motion artifact.…”

“…15 Specifically, this study suggested that the knee was in a straight position in both the sagittal (\20°of flexion) and coronal (\10°of valgus) planes and underwent large anterior tibial translation (.20 mm) near the time of ACL rupture for both bone bruise patterns. 15 We believe that our previous work using imaging techniques to quantify in vivo ACL elongation and joint motion supports the findings of the present study, in that the previous studies suggested that knee extension elevates ACL strain [2][3][4][5][6]8,9,[22][23][24] and puts the ligament at increased risk…”

Elevated In Vivo ACL Strain Is Associated With a Straight Knee in Both the Sagittal and the Coronal Planes

“…It has been shown that quadriceps activity increases prior to landing from a jump. 16,30,50,78 This portion of the jump is when we observed elevated ACL strain, suggesting that quadriceps forces may load the ACL prior to landing. Thus, in the event of landing on an extended knee with unanticipated timing, the ACL is primed with increased tension and therefore more susceptible to rupture.…”

“…1,69 After the MRI, participants were imaged using highspeed biplanar radiography (matrix size, 1152 3 1152 pixels 2 ; frame rate, 120 Hz; pulse width, 1.0-1.5 ms), as previously described. 27,[30][31][32][33] Briefly, the participant was positioned within the field of view of the sources and intensifiers, which were adjusted to minimize obstruction from the contralateral limb. Next, calibration images were collected to correct for image distortion and to define the (C) The wireframe models were used to generate 3D models of the bones, including the femoral and tibial attachment sites of the anterior cruciate ligament.…”

The Predicted Position of the Knee Near the Time of ACL Rupture Is Similar Between 2 Commonly Observed Patterns of Bone Bruising on MRI

“…Specifically, when the knee is extended, the patellar tendon is oriented to apply an anteriorly directed shear force to the proximal tibia. 13,17,18,20 As the flexion angle increases, the patellar tendon applies a posteriorly directed shear force on the tibia. Together with these investigations of in vivo ACL strain as a function of knee flexion angle, 15,[17][18][19] the findings of the present study suggest that landing on an extended knee is a high-risk position for ACL rupture for both those with 3 and 4 bone bruises.…”