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

Effects of lower limb parameters on femoral bone tunnel biomechanics after anterior cruciate ligament reconstruction during dynamic tasks

Tendon-bone healing after anterior cruciate ligament (ACL) reconstruction is influenced by the local mechanical environment. This study aimed to investigate the effects of lower limb kinematics, kinetics, and muscle force on femoral bone tunnel strain, and identify parameters that can predict high bone tunnel strain during three dynamic tasks. Motion data from twelve lower limbs were collected during gait, lunge, and squat using a three-dimensional motion capture system. Lower limb biomechanical parameters were obtained using inverse dynamics methods. A finite element model of single-bundle ACL reconstruction was established to calculate the bone volume around the femoral tunnel within the 2000-4000 μ-strain range. The Spearman correlation coefficient assessed relationships between lower limb parameters and bone tunnel biomechanics. Receiver operating characteristic curve analyses and multivariate binary logistic regressions identified lower limb parameters that distinguished between high and low strain values. Higher semitendinosus muscle force (ρ = 0.895), greater anterior tibial translation (ρ = 0.937), and greater peak knee valgus moment (ρ = 0.872) demonstrated the strongest associations with high bone tunnel strain during gait, lunge, and squat tasks, respectively. The regression model using kinetics to predict high bone tunnel strain trials during the lunge task yielded the highest accuracy (82.6 %), sensitivity (0.424), and specificity (0.960) among all models. Key parameters strongly associated with and predictive of beneficial bone tunnel biomechanics included higher knee lateral contact force during gait, greater hip flexion angle and extension moment during the lunge, and greater lateral tibial rotation angle during the squat.

Posterior Trunk Pulling Perturbation Increased Variables Associated With Anterior Cruciate Ligament Loading in Both Sagittal and Frontal Planes During Landing

Trunk perturbation before initial ground contact (IC) is associated with increased anterior cruciate ligament (ACL) injury risk. The purpose of this study was to determine the effect of midflight anterior and posterior pulling perturbation applied to the upper trunk on ACL loading variables during landings. Participants performed double-leg vertical jumps with and without anterior or posterior pulling perturbation. The perturbation was created by a customized device, pulling participants through a freely dropping slam ball before IC. Whole-body kinematics and ground reaction forces were collected using optoreflective cameras and force plates. Data from 31 participants were included for analysis. The posterior pulling perturbation resulted in the significantly smallest peak trunk and knee flexion angles, the greatest peak knee abduction angle, and peak knee extension and adduction moments during landings. The anterior pulling perturbation resulted in the significantly greatest peak trunk flexion angle and smallest peak knee extension moment among all conditions, and significantly greater peak knee flexion angle, smaller peak knee abduction angle, and smaller peak knee adduction moment compared to the posterior pulling perturbation. The findings suggest increased ACL loading variables and potential injury risk associated with midflight posterior pulling perturbation and provide information for understanding indirect-contact ACL injury mechanisms.

Does Tibial Plateau Slope and Depth Influence ACL Strain In Vivo?

Background

The anterior cruciate ligament (ACL) is loaded under tension when the tibia translates anteriorly relative to the femur. The shape of the articular surfaces of the tibiofemoral joint may influence the amount of anterior tibial translation under compressive loading. Thus, a steep lateral tibial plateau and a shallow medial plateau are thought to be risk factors for ACL injury.

Purpose/Hypothesis

The purpose of this study was to evaluate whether tibial plateau slope and depth influence peak ACL strain during a single-leg jump. We hypothesized that there would be a significant correlation between tibial plateau slope and depth with ACL strain.

Study Design

Descriptive laboratory study.

Methods

A total of 17 healthy participants (8 male, 9 female) were assessed using magnetic resonance imaging (MRI) and high-speed biplanar radiography to obtain peak ACL strain during a single-leg jump. Two orthopaedic surgeons used the sagittal plane MRI scans to measure the medial and lateral tibial plateau slopes and the medial tibial plateau depth. The intraclass correlation coefficient was used to assess measurement reliability, and the Spearman rank correlation was used to evaluate the relationship between measurements of tibial morphology and peak ACL strain during the single-leg jump.

Results

The overall range of intraclass correlation coefficients for intra- and interrater reliability of the medial and lateral tibial plateau slopes and medial plateau depth was 0.59 to 0.97. No significant correlations were found between peak ACL strain and any of the slope or depth measurements.

Conclusion

In this cohort of healthy participants, correlations between any of the tibial plateau measurements with peak ACL strain during a single-leg jump were not detected. These findings are consistent with prior work, suggesting that tibial plateau slope and depth may not be linked to risk for ACL rupture. However, it is possible that tibial plateau morphology may interact with other factors to increase ACL injury risk or that individuals with extreme slope angles may produce differing results.

Clinical Relevance

This study enhances the knowledge of the loading mechanisms for the ACL and thus improves the understanding of risk factors for ACL injury.

A comparison of three methods for establishing an ACL reference length in vivo

As anterior cruciate ligament (ACL) injuries are highly prevalent among active individuals, it is vital to better understand the loading conditions which lead to injury. One method for doing so is through measurement of dynamic, in vivo ACL strain. To measure strain, it is necessary to normalize elongation of the ACL to a 'reference length' which corresponds to the point at which the ligament transitions from being unloaded to carrying tension. The purpose of this study was to compare the length of the ACL in three different positions to evaluate their utility for establishing a reference (or zero-strain) length of the ACL. ACL reference length was determined using three different methods for each of ten healthy participants. Using magnetic resonance and biplanar radiographic imaging techniques, we measured the length of the ACL during supine resting, quiet standing, and anterior/posterior (AP) drawer testing. During the AP drawer testing, the slack-taut transition point was defined as the inflection point of the AP translation vs ACL elongation curve. There was good consistency between the three ACL length measurements (ICC=0.80). Differences in mean ACL length between the three methods were within 1 mm. While determining the precise zero-strain length of the ACL in vivo remains a challenge, the reference positions utilized in this study produce consistent measurements of ACL length. These findings are important because reliable measurements of in vivo ACL strain have the potential to serve as indicators of propensity for injury.

Unanticipated mid-flight external trunk perturbation increased frontal plane ACL loading variables during sidestep cuttings

Unanticipated trunk perturbation is commonly observed when anterior cruciate ligament (ACL) injuries occur during direction-changing manoeuvres. This study aimed to quantify the effect of mid-flight medial-lateral external trunk perturbation directions/locations on ACL loading variables during sidestep cuttings. Thirty-two recreational athletes performed sidestep cuttings under combinations of three perturbation directions (no-perturbation, ipsilateral-perturbation, and contralateral-perturbation relative to the cutting leg) and two perturbation locations (upper-trunk versus lower-trunk). The pushing perturbation was created by customised devices releasing a slam ball to contact participants near maximum jump height prior to cutting. Perturbation generally resulted in greater peak vertical ground reaction force and slower cutting velocity. Upper-trunk contralateral perturbation showed the greatest lateral trunk bending away from the travel direction, greatest peak knee flexion and abduction angles, and greatest peak internal knee adduction moments compared to other conditions. Such increased ACL loading variables were likely due to the increased lateral trunk bending and whole-body horizontal velocity away from the cutting direction caused by the contralateral perturbation act at the upper trunk. The findings may help understand the mechanisms of indirect contact ACL injuries and develop effective cutting techniques for ACL injury prevention.

Falling decreased anterior cruciate ligament loading variables during single-leg landings after mid-flight external trunk perturbation

Mid-flight external upper-trunk perturbation is associated with increased anterior cruciate ligament (ACL) injury risk during landing. This study aimed to assess the effect of natural, soft, and falling landing techniques on knee mechanics and vertical ground reaction forces (VGRF) during single-leg landings with/without mid-flight medial-lateral external upper-trunk pushing perturbation. Twenty-eight participants performed single-leg landings using the three landing techniques with/without mid-flight pushing perturbation. The perturbation was created by a customized apparatus releasing a slam ball and pushing the participants near the peak jump height at the upper trunk. Perturbation resulted in significantly greater lateral trunk bending angles, knee flexion angles at initial contact, peak knee abduction angles, and peak knee adduction moments compared to no perturbation. The falling condition significantly demonstrated the greatest lateral trunk bending angles, knee flexion angles, and peak knee external rotation moments and the smallest peak knee abduction angles, peak VGRF, and peak knee extension moments compared to natural/soft landings regardless of perturbation conditions. Mid-flight external perturbation resulted in variables associated with greater ACL loading during single-leg landings. Falling demonstrated variables associated with smaller ACL loading, particularly for perturbation conditions. Incorporating falling techniques into jump-landing training programs may guide players to safely fall on the ground when perturbation occurs. Falling provides an alternative strategy to potentially decrease indirect contact ACL injury risk when the sports environment allows.

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

BACKGROUND

Noncontact anterior cruciate ligament (ACL) injuries typically occur during deceleration movements such as landing or cutting. However, conflicting data have left the kinematic mechanisms leading to these injuries unclear. Quantifying the influence of sagittal and coronal plane knee kinematics on in vivo ACL strain may help to elucidate noncontact ACL injury mechanisms.

PURPOSE/HYPOTHESIS

The purpose of this study was to measure in vivo sagittal and coronal plane knee kinematics and ACL strain during a single-leg jump. We hypothesized that ACL strain would be modulated primarily by motion in the sagittal plane and that limited coronal plane motion would be measured during this activity.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Seventeen healthy participants (8 male/9 female) underwent magnetic resonance imaging (MRI) followed by high-speed biplanar radiography, obtained as participants performed a single-leg jump. Three-dimensional models of the femur, tibia, and associated ACL attachment site footprints were created from the MRIs and registered to the radiographs to reproduce the position of the knee during the jump. ACL strain, knee flexion/extension angles, and varus/valgus angles were measured throughout the jump. Spearman rank correlations were used to assess relationships between mean ACL strain and kinematic variables.

RESULTS

Mean ACL strain increased with decreasing knee flexion angle (ρ = -0.3; P = .002), and local maxima in ACL strain occurred with the knee in a straight position in both the sagittal and the coronal planes. In addition, limited coronal plane motion (varus/valgus angle) was measured during this activity (mean ± SD, -0.5°± 0.3°). Furthermore, we did not detect a statistically significant relationship between ACL strain and varus/valgus angle (ρ = -0.01; P = .9).

CONCLUSION

ACL strain was maximized when the knee was in a straight position in both the sagittal and coronal planes. Participants remained in <1° of varus/valgus position on average throughout the jump. As a ligament under elevated strain is more vulnerable to injury, landing on a straight knee may be an important risk factor for ACL rupture.

CLINICAL RELEVANCE

These data may improve understanding of risk factors for noncontact ACL injury, which may be useful in designing ACL injury prevention programs.

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

BACKGROUND

Bone bruises observed on magnetic resonance imaging (MRI) can provide insight into the mechanisms of noncontact anterior cruciate ligament (ACL) injury. However, it remains unclear whether the position of the knee near the time of injury differs between patients evaluated with different patterns of bone bruising, particularly with regard to valgus angles.

HYPOTHESIS

The position of the knee near the time of injury is similar between patients evaluated with 2 commonly occurring patterns of bone bruising.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Clinical T2- and T1-weighted MRI scans obtained within 6 weeks of noncontact ACL rupture were reviewed. Patients had either 3 (n = 20) or 4 (n = 30) bone bruises. Patients in the 4-bone bruise group had bruising of the medial and lateral compartments of the femur and tibia, whereas patients in the 3-bone bruise group did not have a bruise on the medial femoral condyle. The outer contours of the bones and associated bruises were segmented from the MRI scans and used to create 3-dimensional surface models. For each patient, the position of the knee near the time of injury was predicted by moving the tibial model relative to the femoral model to maximize the overlap of the tibiofemoral bone bruises. Logistic regressions (adjusted for sex, age, and presence of medial collateral ligament injury) were used to assess relationships between predicted injury position (quantified in terms of knee flexion angle, valgus angle, internal rotation angle, and anterior tibial translation) and bone bruise group.

RESULTS

The predicted injury position for patients in both groups involved a flexion angle <20°, anterior translation >20 mm, valgus angle <10°, and internal rotation angle <10°. The injury position for the 3-bone bruise group involved less flexion (odds ratio [OR], 0.914; 95% CI, 0.846-0.987; P = .02) and internal rotation (OR, 0.832; 95% CI, 0.739-0.937; P = .002) as compared with patients with 4 bone bruises.

CONCLUSION

The predicted position of injury for patients displaying both 3 and 4 bone bruises involved substantial anterior tibial translation (>20 mm), with the knee in a straight position in both the sagittal (<20°) and the coronal (<10°) planes.

CLINICAL RELEVANCE

Landing on a straight knee with subsequent anterior tibial translation is a potential mechanism of noncontact ACL injury.

Indirect contact matters: Mid-flight external trunk perturbation increased unilateral anterior cruciate ligament loading variables during jump-landings

BACKGROUND

To determine the effect of unanticipated mid-flight medial-lateral external perturbation of the upper or lower trunk on anterior cruciate ligament (ACL) loading variables during jump-landings.

METHODS

Thirty-two participants performed double-leg vertical jump-landings while bilateral kinematics and kinetics were collected under 6 conditions (upper or lower trunk perturbation locations; no, left, or right perturbation directions). Two customized catapult apparatuses were created to apply pushing perturbation to participants near the maximal jump height.

RESULTS

The ball contacted participants near the center of mass for the lower-trunk conditions and approximately 23 cm above the center of mass for the upper-trunk conditions. Under upper-trunk perturbation, the contralateral leg demonstrated significantly smaller knee flexion angles at initial contact and greater peak knee abduction angles, peak vertical ground reaction forces, peak knee extension moments, and peak knee adduction moments compared to other legs among all conditions. Under lower-trunk perturbation, the contralateral leg showed significantly smaller knee flexion angles at initial contact and increased peak vertical ground reaction forces and peak knee extension moments compared to legs in the no-perturbation conditions.

CONCLUSION

Mid-flight external trunk pushing perturbation increased ACL loading variables for the leg contralateral to the perturbation. The upper-trunk perturbation resulted in greater changes in ACL loading variables compared to the lower-trunk perturbation, likely due to trunk and ipsilateral leg rotation and more laterally located center of mass relative to the contralateral leg. These findings may help us understand the mechanisms of indirect-contact ACL injuries and develop jump-landing training strategies under mid-flight trunk perturbation to better prevent ACL injury.