Valgus Moment Research Articles

방향전환 동작 시 골반 사전운동이 하지분절 운동역학적 변인에 미치는 영향

Purpose: The purpose of this study is to analyze the effect of pre-orientation of the pelvis on kinematic and kinetic variables of the lower extremity injury during 90˚SSC (side step cutting). This study is also to investigate the relationship between pelvic pre-orientation and lower extremity injury during the SSC.BR Method: Nine healthy male college students participated in this study. Three dimensional motion analyses were used to analyze the kinematic and kinematic variables of A-SSC (typical SSC) and B-SSC (SSC which suppressed pre-orientation of the pelvis) during WAP (weight acceptance phase).BR Results: The approach velocity reached to side cutting point was not significantly different between the two SSCs. Pelvic pre-orientation significantly decreased in the B-SC. The maximum ground reaction force and the location of the center of gravity significantly increased laterally in the A-SSC. Landing distance and last step length both increased with the B-SSC. The maximum angles of knee and hip were not significantly different except the valgus angle of knee joint. The knee valgus and internal rotation moment increased significantly in the A-SSC.BR Conclusion: The length of the last step increased laterally in the B-SSC, but did not increase with the valgus and internal rotation moment of the knee joint. Therefore, even if the pelvic pre-orientation is suppressed during the SSC, it does not seem to have any negative effect on the non-contact knee injury.

Rearfoot strikes more frequently apply combined knee valgus and tibial internal rotation moments than forefoot strikes in females during the early phase of cutting maneuvers

BackgroundAnterior cruciate ligament (ACL) injury often occurs during deceleration maneuvers in sports. Combined knee valgus and tibial internal rotation (VL + IR) moments have been recognized as a risk leading to ACL injury; however, it is unknown how the foot strike pattern (forefoot or rearfoot strike) affects the occurrence rate of the aforementioned combined knee moments during cutting maneuvers. Research questionTo test the hypothesis that rearfoot strikes rather than forefoot strikes show a significantly higher occurrence rate of the combined VL + IR moments during the early stance phase of a cutting maneuver. MethodsTwenty-four females performed 60° cutting maneuvers under rearfoot and forefoot strike conditions. Positional data of lower limb markers and ground reaction force (GRF) were collected. Knee varus/valgus and tibial internal/external rotation moments due to GRF were calculated and time-normalized (0–100 %) to the stance phase. The occurrence rates of combined VL + IR moments were compared between rearfoot and forefoot strike conditions throughout the stance (chi-squared test, p < 0.01). Furthermore, the time patterns of the two knee moments and the position of the GRF acting point were compared using the statistical parametric mapping paired t-test (p < 0.0125). ResultsRearfoot strikes more frequently produced combined VL + IR moments than forefoot strikes (maximum occurrence rates: 73.5 % vs. 27.8 %, p < 0.01) during the first 0–40 % of the stance. Both foot strikes consistently showed an increase in knee valgus moment soon after foot impact; however, rearfoot and forefoot strikes respectively applied opposite internal and external rotation moments during the first 0–7 % of stance (p < 0.0125), indicating that the GRF vector that generated knee valgus moment further applied tibial internal rotation moment when it acted posterior to the tibial rotation axis. SignificanceThe current results suggest that rearfoot strike in cuttings elevates the probability of ACL injury via combined VL + IR moments.

Anterior cruciate ligament repair versus reconstruction: A kinematic analysis

BackgroundThe purpose of this study was to compare the biomechanical properties of an anterior cruciate ligament (ACL) anatomic repair of a true femoral avulsion to an anatomic ACL reconstruction. It was hypothesized that the ACL repair and ACL reconstruction would have comparable biomechanical behavior when compared to the native knee. MethodsTen paired fresh-frozen cadaveric knees (n = 20) were used to investigate knee kinematics when an anterior drawer force, varus, valgus, internal, and external rotational moment were applied at 0, 15, 30, 45, 60, and 90 degrees of flexion. Displacement and rotation were recorded in the following conditions: ACL-intact, ACL-deficient, and ACL-repaired vs reconstructed. ResultsSectioning of the ACL significantly increased anterior tibial translation (0°, 15°, 30° and 45°) compared to the intact state. The mean anterior displacement difference from intact was lower in the ACL-repaired knees compared to reconstructed knees at 30° and 90°. There were no significant differences between conditions in varus, valgus, internal, or external rotations. ConclusionACL repair and ACL reconstruction procedures restored knee anterior tibial translation in matched paired specimens. There were no differences in valgus, varus, internal, or external rotation. Although, ACL-repaired knees (avulsion model) demonstrated less anterior tibial translation when compared to ACL-reconstructed knees, this difference was less than one millimeter. Based on the findings of this study, repair and reconstruction procedures both restored anterior tibial translation in matched-pair specimens. This suggests that the initial functionality of both techniques is similar and that further clinical studies are needed to compare the long-term stability.

By failing to prepare, you are preparing your anterior cruciate ligament to fail.

There is strong evidence linking an athlete's movement technique during sidestepping with anterior cruciate ligament (ACL) injury risk. However, it is unclear how these injuriouspostures are influenced by prior movement. We aim to describe preparatory trunk and thigh kinematics at toe-off of the penultimate-step and flight-phase angular momenta, and explore their associations with frontal-plane risk factors during unplanned sidestepping maneuvers. We analyzed kinematic and kinetic data of 33 male Australian Football players performing unplanned sidestepping tasks (103 trials). Linear mixed models tested for reliable associations between ACL injury risk during weight acceptance of the execution-step, with preparatory kinematics and angular momenta of the trunk and thigh during the penultimate-step. Multi-planar flight-phase trunk momenta along with hip abduction angle at penultimate-step toe-off were significantly associated with peak knee valgus moments during the execution-step (R2 =.21, P<.01). Execution-step trunk lateral flexion was significantly predicted by frontal and sagittal-plane preparatory trunk positioning at toe-off of the penultimate-step (R2 =.44, P<.01). Multi-planar flight-phase trunk momenta as well as multi-planar trunk and hip positioning at penultimate-step toe-offwere associated with hip abduction during the execution-step (R2 =.53, P<.01). Preparatory positioning of the trunk and hip, along with flight-phase trunk momentum adjusting this positioning are linked to known ACL injury risk factors. We recommendthat during the penultimate-step athletes maintain an upright trunk, as well as minimize frontal-plane trunk momentum and transverse-plane trunk momentum toward the sidestep direction to reduce risk of ACL injury during unplanned sidesteps.

Somatosensory Function Influences Aberrant Gait Biomechanics Following Anterior Cruciate Ligament Reconstruction.

Osteoarthritis is common following anterior cruciate ligament reconstruction (ALCR), and aberrant gait biomechanics are considered a primary contributor. Somatosensory dysfunction potentially alters gait biomechanics, but this association is unclear. Therefore, the purposes of this investigation were to compare somatosensory function between limbs and evaluate associations between somatosensory function and gait biomechanics linked to osteoarthritis development in individuals with ALCR. Seventy-three volunteers with ALCR participated. Gait biomechanics (peak vertical ground reaction force magnitude and loading rate, peak internal knee extension and valgus moments, peak knee flexion and varus angles, and quadriceps/hamstrings co-activation) were assessed as subjects walked at their preferred speed. The somatosensory function was assessed via joint position sense error (knee flexion) and vibratory perception threshold (femoral epicondyles, malleoli, and first metatarsal). Though somatosensory function did not differ between the ACLR and contralateral limbs, poorer joint position sense in the ACLR limb was associated with lower loading rates and internal knee extension moments, and greater co-activation. Poorer vibratory perception at the medial and lateral malleoli and first metatarsal head in the ACLR limb was associated with lower loading rates, greater internal knee valgus moments and varus angles, and greater co-activation. Poorer vibratory perception at the medial malleolus and first metatarsal head in the contralateral limb was associated with greater peak knee varus angles and internal knee valgus moments. These results suggest that future research evaluating rehabilitation approaches for improving somatosensory function is warranted as a potential approach for restoring normal gait biomechanics and reducing osteoarthritis risk. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:620-628, 2020.

A 2-yr Biomechanically Informed ACL Injury Prevention Training Intervention in Female Field Hockey Players

ABSTRACT Purpose Anterior cruciate ligament (ACL) injury prevention programs have been shown to have mixed success in reducing injury rates, raising the question whether these programs are effectively targeting biomechanical mechanisms of injury. The current study examined the efficacy of a biomechanically informed ACL injury prevention training program in reducing injury risk and injury incidence and investigated its effect on athletic performance. Participants Twenty-six elite female field hockey players participated in this study. Methods Athletes participated in a 2-yr injury prevention training program. Injury incidence (i.e., lower limb and ACL) and athletic performance (i.e., strength, speed, and aerobic power) were measured during a control season and after two intervention seasons. Biomechanical ACL injury risk factors were recorded during unplanned sidestepping at baseline and after intensive (9 wk: 4 × 20 min·wk−1) and maintenance (16 wk: 3 × 10 min·wk−1) training phases for a subset of athletes (n = 17). Results Training was effective in reducing ACL and lower limb injury incidence after the 2-yr program, where zero ACL injuries occurred after implementation (vs 0.4 per 1000 player hours in the control year). High-risk athletes reduced their peak knee valgus moments by 30% (P = 0.045) and demonstrated improvements in desirable muscle activation strategies after intensive training. The majority of benefits elicited in intensive training were retained during the maintenance phase. One-repetition max strength, beep test scores, and sprint times improved or were maintained over the 2-yr intervention period. Conclusions Biomechanically informed injury prevention training was successful in reducing both biomechanical ACL injury risk factors and ACL injury incidence while maintaining and/or improving athletic performance. It is important to consider the biomechanical mechanisms of injury when designing injury prevention programs.

Do the landing mechanics of experienced netball players differ from those of trained athletes competing in sports that do not require frequent landings?

ObjectivesThis study examined whether young (15–19 years old) high-performance netball players exhibit different landing mechanics compared to female controls who do not participate in sports requiring frequent landings. DesignComparative, cross-sectional. MethodsLower limb kinematics and kinetics from 23 youth high performance female netball players (age: 17.5±1.7 years, height: 1.77±0.06m, mass: 66.5±6.33kg, netball experience: 8.5±2.3 years) were compared to data from 23 females (age: 22.0±3.2 years, height: 1.70±0.05m, mass: 64.4±6.7kg) who were involved in competitive sport, but had minimal experience playing a jump-landing sport. The jump landing task required participants to perform a countermovement jump and grab a netball suspended at 85% of the participant’s maximum jump height. On random trials the ball was raised rapidly to 100% maximum jump height as the participant initiated her jump. ResultsThe netball group landed with significantly less contribution from the knee extensors to total work for the non-preferred leg (P<0.001, ds=1.10) than the inexperienced group. Although no other significant differences were found between groups, there were several small to moderate differences in several of the key biomechanical variables identified as being risk factors for ACL injury or associated with ACL strain. ConclusionsBoth groups had similar knee valgus and internal rotation angles and moments, with nearly all participants presenting with relatively poor frontal plane knee control. Overall, results suggest that experience playing a netball may not be enough to develop low-risk landing mechanics.

Cluster analysis successfully identifies clinically meaningful knee valgus moment patterns: frequency of early peaks reflects sex-specific ACL injury incidence

BackgroundBiomechanical studies of ACL injury risk factors frequently analyze only a fraction of the relevant data, and typically not in accordance with the injury mechanism. Extracting a peak value within a time series of relevance to ACL injuries is challenging due to differences in the relative timing and size of the peak value of interest.Aims/hypothesesThe aim was to cluster analyze the knee valgus moment time series curve shape in the early stance phase. We hypothesized that 1a) There would be few discrete curve shapes, 1b) there would be a shape reflecting an early peak of the knee valgus moment, 2a) youth athletes of both sexes would show similar frequencies of early peaks, 2b) adolescent girls would have greater early peak frequencies.MethodsN = 213 (39% boys) youth soccer and team handball athletes (phase 1) and N = 35 (45% boys) with 5 year follow-up data (phase 2) were recorded performing a change of direction task with 3D motion analysis and a force plate. The time series of the first 30% of stance phase were cluster analyzed based on Euclidean distances in two steps; shape-based main clusters with a transformed time series, and magnitude based sub-clusters with body weight normalized time series. Group differences (sex, phase) in curve shape frequencies, and shape-magnitude frequencies were tested with chi-squared tests.ResultsSix discrete shape-clusters and 14 magnitude based sub-clusters were formed. Phase 1 boys had greater frequency of early peaks than phase 1 girls (38% vs 25% respectively, P < 0.001 for full test). Phase 2 girls had greater frequency of early peaks than phase 2 boys (42% vs 21% respectively, P < 0.001 for full test).ConclusionsCluster analysis can reveal different patterns of curve shapes in biomechanical data, which likely reflect different movement strategies. The early peak shape is relatable to the ACL injury mechanism as the timing of its peak moment is consistent with the timing of injury. Greater frequency of early peaks demonstrated by Phase 2 girls is consistent with their higher risk of ACL injury in sports.

Using the single leg squat as an assessment of stride leg knee mechanics in adolescent baseball pitchers

ObjectivesLack of control of the lower extremity or trunk during single leg tasks is often associated with pathomechanic adaptations during the pitching motion which may increase the risk of pain and injury to the upper extremity. The objectives of the study were to determine the amount of variability in stride knee mechanics accounted for by compensations during a common movement assessment, the single leg squat (SLS) and to establish the usefulness of SLS as a screening tool for at-risk athletes. DesignCross-sectional design. MethodsSixty-one adolescent baseball pitchers performed a SLS on each leg. Participants performed three fastball pitches to a catcher at a regulation distance. Kinematic data were collected at 100Hz using an electromagnetic tracking device. ResultsMANOVAs with follow-up one-way ANOVAs were used to examine the amount of variance in pitching knee mechanics explained by SLS compensations. At stride foot contact, there was a significant effect of SLS valgus angle on knee valgus angle (F1,51=23.16, p<0.001, ηp2=0.31) and valgus moment (F1,51=8.28, p=0.006, ηp2=0.14). At ball release (BR), there was a significant effect of SLS valgus angle on flexion angle (F1,51=9.37, p=0.004, ηp2=0.16) and valgus angle (F1,51 = 26.93, p<0.001, ηp2=0.35). Examination of the average values occurring between SFC and BR, revealed a significant effect of SLS valgus angle on knee valgus angle (F1,51=30.91, p<0.001, ηp2=0.38). ConclusionsSLS compensations are potentially a useful screening tool for stride knee mechanics in adolescent baseball pitchers.

Small Lateral Meniscus Tears Propagate and are Detrimental to Knee Kinematics and Contact Forces

Aims and Objectives: To quantify propagation of small vertical lateral meniscus tears located in the posterior horn during simulated cyclic cutting maneuvers on a robotic testing system and the resulting changes in knee kinematics and forces. Materials and Methods: 14 fresh-frozen human cadaveric knees (mean age: 74.8 ± 14.4) were mounted onto a 6-DOF robotic testing system. Knees with osteoarthritis greater than grade II were excluded. A small vertical tear in the posterior horn of the lateral meniscus medial to the popliteus tendon was created via a posterior arthrotomy. Tear length was measured with a custom-made device (accuracy 0.2 mm, inter-rater reliability 0.914). In 6 specimens, the ACL was resected arthroscopically, whereas in 8 knees the ACL was left intact. 10Nm valgus and 5Nm external rotation moment combined with 250N of axial compression were applied while the knees were continuously flexed from full extension to 90° of flexion for 500 cycles. Meniscus tear length was measured after each 100 cycles. After the measurements, the posterior capsule and skin were closed in a standardized fashion. Knee kinematics, the in situ force in the ACL, the resultant force in the lateral meniscus, and bony contact forces at the tibiofemoral joint were calculated at 30°, 60°, and 90° of knee flexion. A repeated measures ANOVA was used to compared the outcome parameters between knee states (p &lt; 0.05). Results: In intact knees, small vertical lateral meniscus tears propagated significantly from baseline to 100, 200, 300, 400, and 500 cycles (all p &lt; 0.001). This corresponds to a tear propagation of 28.7% ± 5.4%. Similarly, in ACL deficient knees meniscus tear propagation was significant throughout all sets of cycles (p = 0.001). This corresponds to a tear propagation of 26.1% ± 8.3%. While in intact knees, external tibial rotation was significantly increased by up to 45.5% after meniscus tear propagation, knee kinematics were not significantly affected in ACL deficient knees (NS). The resultant forces in the lateral meniscus increased with tear propagation in the intact knees by up to 54.1%. Likewise, the resultant forces in the lateral meniscus increased in the ACL deficient knees by up to 116.5% (p &lt; 0.05). In intact knees, bony contact forces at the tibiofemoral joint increased with meniscus tear propagation by up to 91.9% (p &lt; 0.05), which was comparable to ACL deficient knees. Conclusion: The data of this study suggest, that small vertical lateral meniscus tears propagate significantly regardless of the integrity of the ACL and after only 100 cycles of knee loading. The findings of the current robotic study are in contrast to recent clinical studies that found that small, vertical and stable tears in the posterior horn of the lateral meniscus could be left in situ. However, based on the current data, such tears do propagate over time regardless of the integrity of the ACL, which might alter knee kinematics and resultant forces in the lateral meniscus as well as bony contact forces at the tibiofemoral joint.

The Biomechanical Effects of Fatigue on Drop-Jump Performance in Basketball Athletes

Anterior Cruciate Ligament (ACL) injuries have high occurrences in the sport of basketball due to the high amounts of landing, cutting, and other sudden deceleration maneuvers. During landing, studies have prospectively linked insufficient amounts of knee flexion, greater knee valgus angles, and greater knee valgus moments accompanied by greater vertical ground reaction force to increased risk of ACL injuries. These mechanisms have shown to be increased in a fatigued state therefore suggesting an athlete may be at greater risk for ACL injury when they are fatigued. Research to support this claim, however, is inconclusive. PURPOSE: To examine the difference in peak knee flexion angle (pKFA), peak knee valgus angle (pKVA), peak knee valgus moment (pKVM), and peak vertical ground reaction force (vGRF) pre and post fatigue during the landing phase of a drop jump task in basketball athletes. METHODS: Twenty-five subjects participated in the study and performed three drop jump trials before and after a fatigue protocol involving repeated counter movement jumps touching a customized target specific to each subject. Data was captured using a Qualisys 9-camera motion capture system sampling at 240-Hz and two AMTI force plates sampling at 2400-Hz. RESULTS: Paired t-tests showed subjects landed with significantly greater pKFA post fatigue (p < .05) while pKVA, pKVM, and pGRF showed no difference pre- and post-fatigue (p > .05). CONCLUSION: Subjects in this study adopted a safer landing strategy post fatigue, hence, suggesting our study did not support the claim that athletes would be at greater risk for ACL injuries in a fatigued state.

Co-activation during gait following anterior cruciate ligament reconstruction

BackgroundHeightened co-activation of the quadriceps and hamstrings has been reported following anterior cruciate ligament reconstruction during various tasks, and may contribute to post-traumatic osteoarthritis risk. However, it is unclear if this phenomenon occurs during walking or how co-activation influences gait biomechanics linked to changes in joint health. MethodsCo-activation and gait biomechanics were assessed in 50 individuals with ACLR and 25 healthy controls. Biomechanical outcomes included knee flexion displacement, peak vertical ground reaction force magnitude and rate, peak internal knee extension and valgus moments and rates, sagittal knee stiffness, and the heelstrike transient. Co-activation was calculated for the flexors and extensors collectively (i.e. composite), the medial musculature, and the lateral musculature. FindingsComposite co-activation was greater in the ACLR limb compared to the contralateral limb and the control cohort during the preparatory and heelstrike phases of gait, and co-activation of the medial musculature was greater in the ACLR limb compared to the control cohort during the heelstrike phase. Greater co-activation in multiple gait phases was associated with less knee flexion displacement (r = −0.293 to −0.377), smaller peak vertical ground reaction force magnitude (r = −0.291), smaller peak internal knee extension moment (r = −0.291 to −0.328), and greater peak internal knee valgus moment (r = 0.317). InterpretationIndividuals with ACLR displayed heightened co-activation during walking which was associated with biomechanical outcomes that have been linked to negative changes in joint health following ACLR. These data suggest that excessive co-activation may contribute to the mechanical pathogenesis of post-traumatic osteoarthritis.ClinicalTrials.gov Identifier: NCT02605876.

Biomechanical Differences in Knee Valgus Angles in Collegiate Female Athletes Participating in Different Sports

Background: Dynamic knee valgum is a major risk factor in ligamentous injuries of the knee. Different sports have higher rates of knee ligament injury than others and females experience knee non-contact ligament injuries at higher rates than their male counterparts. Objectives: The purpose of this study was to investigate the lower extremity biomechanics of genu valgum in female collegiate athletes of various sports while performing a drop jump test. This information may provide those designing individualized prevention programs assistance in reducing risk of knee ligamentous injury during jumping tasks. Methods: Current members of Idaho State University’s women’s basketball, soccer, and softball teams were evaluated for this study. Thirty-seven athletes participated. Motion capture reflective markers were placed bilaterally on the lower extremities to allow for analysis of knee biomechanics during a double-leg drop jump test. The angles of knee valgum in the frontal plane were calculated and analyzed between sport groups. Results: Female athletes of different sports displayed statistically significant differences in knee angles for both right, and left knees. Post hoc analysis with a Bonferroni adjustment revealed that basketball players utilized a more valgus right knee angle compared to both soccer and softball players and a more varus left knee angle compared with softball players. Conclusions: Our study suggests that collegiate-level female basketball players have an increased risk of right leg non-contact knee ligament injury during jump landing maneuvers when compared to collegiate level softball and soccer players due to increased knee valgus movements during the drop jump test. Collegiate-level female basketball players may benefit from biomechanical exercise interventions designed to decrease right knee valgus moments in jumping and landing to decrease their risk of injury.

Visual-Spatial Memory Deficits Are Related to Increased Knee Valgus Angle During a Sport-Specific Sidestep Cut

Background: Identifying athletes at an increased risk of injury is a promising approach to improve the effect of injury prevention interventions; however, it requires first identifying the potential athlete-specific risk factors. Cognitive ability was recently shown to correlate with noncontact anterior cruciate ligament injury rates and lower extremity mechanics, marking an underexplored area. A better understanding of how individuals’ cognitive ability is associated with neuromuscular control during sport-specific tasks may improve injury prevention. Hypothesis: Athletes with lower cognitive performance on a standardized cognitive assessment would demonstrate greater increases in knee valgus angle and moment when performing a sidestep cut with soccer ball dribbling versus without. Visual-spatial memory was expected to demonstrate stronger relationships than reaction time or processing speed. Study Design: Descriptive laboratory study. Methods: Fifteen male collegiate club soccer players participated (mean ± SD: 20.7 ± 2.0 years, 1.78 ± 0.07 m, 76.5 ± 8.9 kg). Participants performed anticipated 45° run-to-cut trials with and without a dual task of dribbling a soccer ball. Peak early-stance knee valgus angle and moment for the plant limb were calculated. Participants also completed a cognitive assessment to evaluate visual memory, verbal memory, reaction time, and processing speed. These composite scores were entered as candidate predictors for a stepwise regression analysis on the dual-task change scores in lower extremity biomechanical parameters (ie, ball handling – non–ball handling). Results: Visual memory composite score (a measure of visual-spatial memory) was the only cognitive outcome significantly associated with the change in biomechanical parameters. Each unit decrease in the visual memory composite score was associated with an increase of 0.21°± 0.05° in peak knee valgus angle during the ball-handling task as compared with the non–ball handling task (R2 = 52%, P = .003). Conclusion: Visual-spatial memory was associated with neuromuscular control during a sidestep cutting task during soccer ball dribbling, with deficits in this cognitive domain being associated with increased peak knee valgus angle. Clinical Relevance: Assessing visual-spatial memory ability may provide useful information to better understand conditions associated with impaired neuromuscular control and to potentially identify athletes at an elevated risk for musculoskeletal injury.

Amputee Locomotion: Joint Moment Adaptations to Running Speed Using Running-Specific Prostheses after Unilateral Transtibial Amputation.

The objective of this study was to investigate three-dimensional lower extremity joint moment differences between limbs and speed influences on these differences in individuals with lower extremity amputations using running-specific prostheses. Eight individuals with unilateral transtibial amputations and 8 control subjects with no amputations ran overground at three constant velocities (2.5, 3.0, and 3.5 m/sec). A 2 × 2 × 3 (group × leg × speed) repeated-measures analysis of variance with Bonferroni adjustments determined statistical significance. The prosthetic limb generated significantly greater peak ankle plantarflexion moments and smaller peak ankle varus, knee stance extension, knee swing flexion, knee internal rotation, hip stance flexion, hip swing flexion, hip swing extension, hip valgus, and hip external rotation moments than the intact limb did. The intact limb had greater peak hip external rotation moments than control limbs did, but all other peak moments were similar between these limbs. Increases in peak hip stance and knee swing flexion moments associated with speed were greater in the intact limb than in the prosthetic limb. Individuals with amputation relied on the intact limb more than the prosthetic limb to run at a particular speed when wearing running-specific prostheses, but the intact joints were not overloaded relative to the control limbs.

DOES A COMBINED INTRA-ARTICULAR AND EXTRA-ARTICULAR ACL RECONSTRUCTION EFFECT EXTERNAL KNEE VALGUS MOMENT ASYMMETRY?

Introduction: Peak external knee valgus moment can predict future ACL injury and is, often times, asymmetric following anatomic intra-articular ACL reconstruction. The purpose of this study is to evaluate the external knee valgus moment during a drop landing and a single limb squat 2 years following an iliotibial band (ITB) intra-articular and extra-articular physeal-sparing ACL reconstruction. Methods: Fourteen study subjects (mean age: 14.3 ± 2.6 yrs) who had previously undergone a physeal-sparing ACL reconstruction, as originally described by McIntosh using an ITB autograft, were enrolled in this IRB-approved study. All subjects were seen at a minimum of 24 months after surgery (mean follow-up: 55.0 ± 28.9 mos) and clinical, radiographic, and patient reported outcomes were collected. During functional testing, subjects underwent drop landing (DL) and unilateral squat (US) tasks. Isokinetic muscle strength of the hip and knee was collected using an isokinetic dynamometer at 60°/s. Paired student’s t-tests evaluated differences between affected (AFF) and unaffected (UNAFF) limbs. Results: During a drop landing, the AFF limb, compared to the UNAFF limb, did not demonstrate a difference in external knee valgus moment (0.50° vs. 0.51°, p=0.736). However, in the AFF limb, the mean knee peak knee valgus angle was 2.8 degrees less than the UNAFF limb during a drop landing (p=0.039). This difference was not considered within the range of a minimal clinical difference (MCD) of 5.1 degrees. Similar trends were found during a single limb squat with no significant difference seen in peak knee valgus moment between AFF and UNAFF (0.14° vs. 0.07°, p=0.150) with a statistical, yet not minimal clinical difference, in knee valgus angle at 45° squat position (-2.4° vs. 0.7°, p=0.033; MCD = 5.2). Thus, no asymmetry in peak knee valgus moment during a drop landing or a single limb squat following an ITB intra- and extra-articular ACL reconstruction was observed. In this series at 2 years’ post-op, the Pedi-IKDC and HSS Pedi-FABS were 96.54 ± 5 and 22.6 ± 5, respectively. Subjects demonstrated return to pre-operative Tegner Activity scores (8.42 vs. 8.17, p=0.33). Normalized hip abduction strength was significantly stronger in AFF (1.05 Nm/kg) vs. UNAFF (0.93 Nm/kg, p=0.02). Conclusion: Overall, there were no clinically significant differences, or asymmetry, in functional knee valgus in subjects following combined intra- and extra-articular iliotibial band ACL reconstruction during a drop landing or single leg squat. Young athletes can be expected to return to pre-operative activity levels and demonstrate appropriate knee valgus control following this physeal-sparing ACL reconstruction.

AGE, BODY MASS INDEX AND SEX RELATED TO DYNAMIC KNEE VALGUS AND SHOCK ABSORPTION DURING SINGLE LEG LANDING IN UNINJURED ADOLESCENT ATHLETES

BACKGROUND Dynamic limb valgus and poor shock absorption strategies have been implicated in anterior cruciate ligament (ACL) injuries. Additionally, biomechanics during over ground and double leg landing tasks have been shown to differ depending on sex and age/maturation. However, there is limited evidence evaluating the effect of age, body mass index (BMI) and sex on single leg landing strategies. METHODS 51 uninjured athletes (ages 7-15 years, mean 12.2, SD 2.3; 45% female) completed the single leg hop (SLH) for distance task. 3-D motion analysis using a 6 degree-of-freedom model was used to collect lower extremity kinematics and kinetics from initial foot contact to peak knee flexion of landing limb; for each limb the hop with the longest distance and appropriate landing (stuck for &gt;2 seconds) was used for analysis. Using multivariate regression with standardized coefficients, the effects of age, BMI and sex on biomechanical variables of interest were assessed. RESULTS When considering dynamic valgus components, younger age was associated with higher knee valgus (ß=0.251; p=0.038) and hip abduction (ß=0.250; p=0.038) angles, higher BMI was associated with higher knee valgus angles (ß=0.262; p=0.028), and females tended to have higher hip abduction moments (ß=0.301; p=0.003), but a more abducted (ß=0.281; p=0.005) and internally rotated hip position (ß=0.359; p=0.003) along with higher internal rotation hip moments (ß=0.298; p=0.001) and with higher ankle inversion moments (ß=0.304; p=0.003). Although differences were observed, R2 values were low ranging from 0.191 (hip ab/adduction angles) to 0.053 (knee valgus moment). Sagittal plane components of shock absorption were partially explained by age, BMI and sex (R2 values range from 0.685 to 0.013; vertical ground reaction force (vGRF) in multiples of body weight, ankle dorsi/plantarflexion moment, respectively). Younger age was associated with higher vGRF (ß=-0.520; p&lt;0.0001) and knee flexion moments (ß=-0.225; p=0.034), but with lower knee flexion angles (ß=0.252; p=0.041), ankle dorsiflexion angles (ß=0.322; p=0.003) and hip flexion moments (ß=0.289; p=0.016). Higher BMI was associated with lower GRF (ß=-0.387; p&lt;0.0001), lower knee (ß=-0.277; p=0.009) and hip (ß=-0.289; p=0.043) flexion moments and lower sagittal plane energy absorption at the knee (ß=-0.267; p=0.016). Females tended to have lower vGRF (ß=0.147; p=0.017), more sagittal plane hip (ß=0.282; p=0.007) and knee (ß =0.250; p=0.010) energy absorption and less ankle dorsiflexion (ß=-0.283; p=0.002). CONCLUSION/SIGNIFICANCE Biomechanical risk factors for ACL injury during single leg hop landings are influenced by age, BMI and sex. Female sex and higher BMI are associated with dynamic limb valgus while younger age is associated with both dynamic limb valgus and poor shock absorption during single leg hop landings. These are important findings due to the known ACL injury risk in female athletes and the high re-tear rate in pediatric athletes. Identifying these biomechanical risk factors related to demographics and anthropometrics may provide objective direction needed to contribute to effective intervention strategies and eventual injury reduction in these high risk groups.

RELIABILITY OF A NEW LANDING ERROR SCORING SYSTEM: THE LESS-RMC

BACKGROUND Several biomechanical deficits have been shown to increase non-contact knee injury risk of the anterior cruciate ligament (ACL). The Landing Error Scoring System (LESS) is a clinical assessment tool that has been successfully used to predict the individuals that are at a high risk for injury and evaluate changes in landing technique after participation in a neuromuscular preventive training program. The LESS-RT is a shortened version of the LESS and is a method to score landing technique without the use of video. The current study proposes a new tool for the evaluation of landing technique and ACL injury risk that blends the LESS and LESS-RT protocols but emphasizes the movement features that contribute to high knee valgus moments including movement asymmetry. The LESS-RMC (Rocky Mountain Consortium) consists of evaluating 11 comprehensive landing errors that are related to ACL injury risk. Consolidating questions pertaining to the opposite ends of joint motion such as “toe in” and “toe out” into “maximum foot rotation position” and adding a global asymmetry score were performed to reduce the time demands for evaluation yet capture the salient factors of the LESS; whereas the penalty for knee valgus severity was pulled from the LESS-RT but implemented for both knees in the new LESS-RMC to ultimately stratify knee injury risk during the jump landing task. The purpose of this study was to determine the reliability of the new LESS-RMC assessment tool. METHODS Thirty-seven, elite female soccer athletes (13.2 +/- 0.4 y) performed three drop-jumps from a height of 30 cm. Front and side views of the landing were recorded with digital video cameras. Movement quality was rated by 4 researchers evaluating 17 components of the landing with the LESS and a modified, 11 component version of the LESS (LESS-RMC). The 4 raters were novel to the evaluation of both scoring systems. Each rater was trained how to score each test and was instructed to evaluate the landing trials from the first 10 participants. After a group video review and discussion, the raters repeated the scoring procedures for the same 10 participants 48 hours after the original review. After another 48 hours, the raters evaluated the landing trials for all 37 participants (111 trials). Inter-rater reliability of the LESS and LESS-RMC were determined using the ICC (3,1) equations and the output from a two-way ANOVA (SPSS, version 25). RESULTS The mean LESS score was 6.45 +/- 0.55 (rater 1, 6.42; rater 2, 7.15; rater 3, 5.79; rater 4, 6.45). The ICC agreement between raters of scoring the LESS was .389 whereas the ICC agreement for the mean of the four raters was .718. The ICC for scoring consistency was .382 and Cronbach’s a was .735. The mean LESS-RMC score was 6.19 +/- 0.74 (rater 1, 5.65; rater 2, 6.99; rater 3, 5.48; rater 4, 6.64). The ICC agreement of scoring the LESS-RMC was .585 whereas the ICC agreement for the mean of the four raters was .849. The ICC for scoring consistency was .574 and Cronbach’s a was .884. CONCLUSION On average, the raters scored the LESS and the LESS-RMC with moderate reliability across the group of athletes. The LESS-RMC was scored with greater reliability than the LESS for this group of relatively novice raters. This is likely due to the simplification of the overall protocol in terms of quantity of questions, the ability of a novel rater to understand scenarios which elicit specific scores and the clear separation of body segments (e.g. hip and trunk flexion). In conjunction with this, it was reported by the raters that LESS-RMC was less redundant and more effective at assessing crucial aspects of a jump landing pattern. Overall, LESS RMC was objectively and subjectively more reliable and easier to use than the LESS for the four raters involved in this study. It is concluded that the LESS-RMC is a quick, easy and reliable clinical assessment tool that may be used to stratify individuals who may be at risk for ACL injury.

Effects of tibiofemoral compression on ACL forces and knee kinematics under combined knee loads.

Injuries to the anterior cruciate ligament (ACL) can occur during landing from a jump or changing direction during a cutting maneuver. In these instances, the knee is subjected to combined forces and moments as it flexes under tibiofemoral compression force (TCF). We hypothesized that TCF would increase ACL forces and tibiofemoral motions under isolated and combined modes of loading relevant to knee injury. ACL force and knee kinematics were recorded in human cadaveric specimens during knee flexion from 0° to 50° under the following test conditions (alone and in combination): 2 N-m internal tibial torque (IT), 5 N-m valgus moment (VM), and 45N anterior tibial force (AF). Knees were tested with 25N (baseline), 250N, and 500N TCF. ACL force increased with knee flexion during all tests. As the knee was flexed, VM produced a coupled internal tibial rotation, and IT produced a coupled valgus rotation. ACL forces with IT + VM were significantly higher than with IT alone (beyond 10° flexion) or VM alone (at all flexion angles). Increasing the level of TCF above baseline did not significantly change valgus or tibial rotations for any loading condition, but did significantly increase anterior tibial translation (ATT) at all flexion angles and ACL force at flexion angles beyond 5° to 15°. Addition of AF to tests with IT + VM significantly increased ATT and ACL force without significantly altering internal and valgus rotations. The mechanism of high ACL force generation from increased TCF was related to ATT and not internal or valgus rotations of the tibia. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

A Biomechanical Comparison of Single-, Double-, and Triple-Bundle Anterior Cruciate Ligament Reconstructions Using a Hamstring Tendon Graft

The first objective of our cadaveric study was to perform a biomechanical comparison of single-bundle (SB), double-bundle (DB), and triple-bundle (TB) anterior cruciate ligament (ACL) reconstructions using a hamstring tendon graft to determine the laxity match pre-tension (LMP) value, which is the tension within the graft required to re-create the same anterior laxity as the ACL-intact knee. The second objective was to determine the anterior laxity and force distribution during the application of both an anterior force and a simulated pivot-shift test. Eleven fresh-frozen cadaveric knees were tested using a robotic/universal force-moment sensor system in the intact state, TB-reconstructed knee, DB-reconstructed knee, and SB-reconstructed knee. The LMP in each reconstruction was recorded. Each reconstructed knee was tested with an external load of 100-N anterior drawer and combined rotatory loads of 10-Nm valgus moment and 5-Nm internal rotation. The anterior tibial translation and tensile forces of each graft bundle were measured. The LMP values for the TB reconstruction were 1.7N for the anteromedial-medial graft, 1.7N for the anteromedial-lateral graft, and 3.4N for the posterolateral graft (PLG). The LMP value was 5.6N for the anteromedial graft and PLG in the DB reconstruction. The LMP value was 26.3N for the whole graft in the SB reconstruction. No statistically significant difference in stability was found between TB and DB reconstructions during the anterior load and the combined rotatory load test. For force distribution, the PLG tension in the TB reconstruction was statistically lower than that in the DB reconstruction. Anatomic TB ACL reconstruction with the lowest initial tension on the graft stabilized the knee equally to DB or SB reconstruction, which required greater initial tension. Although SB, DB, and TB ACL reconstructions through the anatomic tunnel position could equally restore stability, the initial tension on the graft required to restore stability was less in the latter 2 multi-tunnel reconstructions.