Mechanism of non-contact ACL injury: OREF Clinical Research Award 2021

A Robotic Clamped-Kinematic System to Study Knee Ligament Injury

Knee ligament injury is among the most common sports injuries and is associated with long recovery periods and low return-to-sport rates. Unfortunately, the mechanics of ligament injury are difficult to study in vivo, and computational studies provide limited insight. The objective of this study was to implement and validate a robotic system capable of reproducing natural six degree-of-freedom clamped-kinematic trajectories on human cadaver knees (meaning that positions and orientations are rigidly controlled and resultant loads are measured). To accomplish this, we leveraged the field's recent access to high-fidelity bone kinematics from dynamic biplanar radiography (DBR), and implemented these kinematics in a coordinate frame built around the knee's natural flexion-extension axis. We assessed our system's capabilities in the context of ACL injury, by moving seven cadaveric knee specimens through kinematics derived from walking, running, drop jump, and ACL injury. We then used robotically simulated clinical stability tests to evaluate the hypothesis that knee stability would be only reduced by the motions intended to injure the knee. Our results show that the structural integrity of the knee was not compromised by non-injurious motions, while the injury motion produced a clinically relevant ACL injury with characteristic anterior and valgus instability. We also demonstrated that our robotic system can provide direct measurements of reaction loads during a variety of motions, and facilitate gross evaluation of ligament failure mechanisms. Clamped-kinematic robotic evaluation of cadaver knees has the potential to deepen understanding of the mechanics of knee ligament injury.

Increased rate of injuries to the anterior cruciate ligament in amateur soccer players after the COVID-19 pandemic lockdown

The COVID-19 pandemic led to the discontinuation of soccer activities at all levels of play. Injuries to the anterior cruciate ligament (ACL) are still one of the most severe injuries in soccer. The aim of this investigation was to analyze the changes in the incidence and mechanism of ACL injuries in professional and amateur soccer before and after the lockdown period. Injury data were prospectively collected using the database 'ACL registry in German soccer'. Between 2019 and 2021, 10 matches in professional, semi-professional, and amateur leagues before and after the lockdown were analyzed for the incidence and mechanism of ACL injuries. Data were collected using standardized and recently published study methods. Mean incidence of the 84 ACL injuries recorded during the study period was 0.083 injuries per 1000 h of exposure before and 0.079 injuries per 1000 h of exposure after the lockdown period (p = 0.699). In amateur soccer, the incidence of ACL injuries increased significantly from 0.058 injuries per 1000 h of exposure before to 0.128 injuries per 1000 h of exposure after the lockdown period (p = 0.026), in contrast to professional (p = 0.436) and semi-professional (p = 0.802) soccer. The predominant mechanisms of ACL injuries were non-contact injuries (pre-COVID: 59.1%; post-COVID: 57.7%) and indirect contact injuries (pre-COVID: 31.8%; post-COVID: 30.8%). The absence from training and match practice in German soccer during the COVID-19 lockdown led to a significantly increased ACL injury rate in amateur leagues, while in professional and semi-professional soccer no differences were reported. The mechanism of ACL injuries did not change after the lockdown period.Level of evidence: II.

Prediction of ACL-tear by lower limbs muscle strength and flexibility: a prospective cohort study in 95 female soccer players

The aims of the study were to build models using logistic regression analysis of flexibility and strength tests to prospectively predict risk factors for anterior cruciate ligament tear (ACL-tear) in female soccer (FS) players, and to determine training cut-off for risk factors of the predictive model built. A prospective cohort study of 95 female players (aged 14-33 years) was conducted. Age, anthropometric data, soccer history, lower limb range of motion (ROM) and hip maximal isometric strength (MIS) were measured. At the prospective follow-up after 12 months, 7.4% of the players had developed an ACL-tear. The model showed a significant relationship (χ2(93) = 30.531, p < 0.001) between the ACL-tear and the predictor variables (leg length, HAD-NH [hip adduction] MIS, asymmetric ROM [ankle dorsiflexion with knee extended (AD-KE) and with knee flexed (AD-KF), and HE (hip extension)], hip ROM [HIR (internal rotation) and HAB (abduction)]). The Akaike Information Criteria (AIC) and Bayesian Information Criteria (BIC) for model fit were 30.24 and 51.79, respectively. The value R2 showed good model fit, 76.5% for Nagelkerke´s R2, 71.4% for McFadden´s R2 and 67.5% for Tjur´s R2. For the screening test, cut-off for leg length of ≥0.40 m, for HIR ROM of ≤44º and for asymmetry of HE ROM of ≥5° were set, which have an acceptable (AUC ≥ 0.755) discriminatory ability for the development of ACL-tear.

Anterior Cruciate Ligament Tears in Soccer Players

Anterior cruciate ligament (ACL) injuries to soccer players present unique challenges in sports medicine, given the sport's global prevalence and intricate injury dynamics. These injuries, especially in the youth and female demographic, have become a substantial concern in sports medicine. This review explores the epidemiology, mechanism of injury, diagnostic procedures, treatment modalities, and rehabilitation strategies related to ACL tears within the soccer community. Progress in diagnostics, treatments, and rehabilitation underscores the importance of evidence-based approaches. As soccer continues its ascent in popularity, addressing the specific risks and nuances of ACL injuries in this context remains of paramount significance.

Video analysis of anterior cruciate ligament tears of professional basketball players in the National Basketball Association

BACKGROUND

Anterior cruciate ligament (ACL) tears are devastating for elite athletes, including those in the National Basketball Association (NBA). The purpose of this study was to describe common in-game mechanisms of injury, playing situations, and anatomic positioning of players who sustained an ACL injury in the NBA.

METHODS

ACL tears which occurred in NBA games during the previous 16 seasons (2007-2022) and had accessible video clips were identified through publicly available reports.

RESULTS

Thirty-one ACL tears were identified with quality videos available. Nearly all players were on offense (93.5%, 29/31). Most ACL tears (29/31, 93.5%) did not involve direct contact to the injured extremity. The most common physical activity at the time of injury was landing from any type of jump (45.2%, 14/31). Anatomically, the knee was frequently in early flexion (58.8%, 10/17) and abducted (77.4%, 24/31); the foot was commonly abducted (87.1%, 27/31); and the hip was usually abducted (64.5%, 20/31) and flexed (80.6%, 25/31). Almost all players had another individual near them at the time of injury, with 90.3% (28/31) and 96.8% (30/31) having someone within 2ft and 5ft.

CONCLUSIONS

Most ACL tears occurred inside the lane, regardless of mechanism of injury (26/31, 83.9%). ACL tears in the NBA were primarily not due to direct contact of the injured extremity but did have common anatomic patterns. The findings of this study can be used in the future to help reduce the risk of injury through the adaptation of current training activities.

Investigation of the anatomic risk factors in acute anterior cruciate ligament ruptures to develop ramp lesions of the medial meniscus by quantitative MRI

OBJECTIVE

To investigate the anatomic risk factors of knee in patients with acute non-contact anterior cruciate ligament (aACL) ruptures to develop ramp lesions.

METHODS

A total of 202 subjects were retrospectively divided into three groups: (1) aACL ruptures combined with ramp lesions group (n = 76); (2) isolated ACL ruptures group (n = 56) and (3) normal controls group (n = 70). Quantitative morphological parameters on MRI were measured including: diameter of medial femoral condyle (MFC), anterior-posterior length and depth of medial tibial plateau (MTP AP length and depth), lateral posterior tibial slope (LPTS) and medial posterior tibial slope (MTPS), asymmetry of LPTS and MPTS (LMPTS), lateral meniscal slope (LMS), and medial meniscal slope (MMS).

RESULTS

The MTP AP length, MTP AP length/MFC diameter ratio, MTP depth, LPTS and the asymmetry of LMPTS showed significant differences among the three groups (p < 0.001). The risk factors associated with the ramp lesions including a longer MTP AP length (OR 1.17, 95% CI 1.00-1.44, p = 0.044), increased MTP depth (OR 1.91, 95% CI 1.22-3.00, p = 0.005) and lager ratio (OR 1.11, 95% CI 1.01-1.22, p = 0.036). The highest AUC was the MTP AP length/MFC diameter ratio (0.74; 95% CI, 0.66-0.82). The combination model increased higher accuracy (0.80; 95% CI, 0.72-0.88).

CONCLUSION

Several bony anatomic characteristics of the knee, especially the morphology of medial tibia plateau, are additional risk factors for aACL ruptures to develop ramp lesions.

CRITICAL RELEVANCE STATEMENT

Predictive anatomic risk factors of the knee for patients with acute non-contact anterior cruciate ligament (aACL) ruptures to develop ramp lesions, especially the morphology of medial tibia plateau, are detectable by MRI.

KEY POINTS

Ramp lesion development can complicate aACL ruptures and requires specific treatment. Longer AP length and increased MTP depth are risk factors for concurrent ramp lesions. Identification of ramp lesions allows for the most appropriate treatment.

Influence of the Menstrual Cycle and Training on the Performance of a Perturbed Single-Leg Squatting Task in Female Collegiate Athletes

Background

Anterior cruciate ligament (ACL) injuries often occur when an athlete experiences an unexpected disruption, or perturbation, during sports. ACL injury rates may also be influenced by the menstrual cycle.

Purpose

To determine whether training adaptations to knee control and muscle activity during a perturbed single-leg squatting (SLS) task depend on menstrual cycle phase in female athletes.

Study Design

Controlled laboratory study.

Methods

A total of 21 healthy female collegiate athletes (current or former [<3 years]) who competed in 9 different sports performed an SLS task in which they attempted to match their knee position (user signal) to a target signal. The protocol consisted of a 9-condition pretest, 5 sets of 3 training trials, and a 9-condition posttest. One perturbation was delivered in each condition by altering the resistance of the device. Sagittal knee control (absolute error between the target signal and user signal) was assessed using a potentiometer. Muscle activity during perturbed squat cycles was normalized to maximal activation and to corresponding muscle activity during unperturbed squat cycles (%unperturbed) within the same test condition. Athletes performed the protocol during a distinct menstrual cycle phase (early follicular [EF], late follicular [LF], midluteal [ML]). Two-way mixed analysis of variance was used to determine the effects of the menstrual cycle and training on knee control and muscle activity during task performance. Venous blood was collected for hormonal analysis, and a series of health questionnaires and anthropometric measures were also assessed to determine differences among the menstrual cycle groups.

Results

After training, athletes demonstrated better knee control during the perturbed squat cycles (lower absolute error, P < .001) and greater soleus feedback responses to the perturbation (%unperturbed, P = .035). Better knee control was demonstrated in the ML phase versus the EF phase during unperturbed and perturbed squat cycles (P < .039 for both). Quadriceps activation was greater in the ML phase compared with the EF and LF phases, both immediately before and after the perturbation (P < .001 for all).

Conclusion

Athletes learned to improve knee control during the perturbed performance regardless of menstrual cycle phase. The best knee control and greatest quadriceps activation during the perturbed squatting task was found in the ML phase.

Clinical Relevance

These findings may correspond to a lower incidence of ACL injury in the luteal phase and alterations in exercise performance across the menstrual cycle.

Direct contact and very rapid valgus distortion characterise the injury mechanism of anterior cruciate ligament ruptures in judo

PURPOSE

To analyse anterior cruciate ligament (ACL) rupture (ACLR) injury mechanisms in competitive judo using systematic video analysis, focusing on contact situations and biomechanics.

METHODS

Seventeen videos of judo competitions wherein athletes developed ACLRs were included and retrospectively evaluated by five analysts. In all videos, the moment of initial contact and the index frame were defined. The judo techniques leading to the injury; the occurrence of direct contact, indirect contact or noncontact mechanisms; the time interval between the initial contact and index frame; the positions of the hip, knee and foot in relation to the initial contact and index frame; and the balance status during the initial contact and index frame were recorded.

RESULTS

Eleven (65%) of ACLRs in judo involved direct contact. The mean time interval between initial contact and index frame was 15 ± 22 ms. Thirteen (77%) athletes were not balanced at initial contact. In the index frame, the hip was abducted in all cases and in combination with internal rotation in 12 (71%) cases. From initial contact to index frame, hip flexion increased in all cases; at index frame, the knee joint was internally rotated relative to the trunk in 12 (71%) cases, and the knee flexion angles increased from the initial contact. In the index frame, the foot was externally rotated relative to the knee in 12 (71%) cases, and severe valgus development of the knee with valgus collapse was observed in 14 (82%) cases.

CONCLUSIONS

A direct attack on the knee was the most common injury mechanism observed. Valgus distortion appears to be the most important component of the mechanism of injury. With this knowledge, 'modified defence reactions' for specific judo techniques can be developed to reduce the injury risk.

LEVEL OF EVIDENCE

Level IV.

The deterministic condition for the ground reaction force acting point on the combined knee valgus and tibial internal rotation moments in early phase of cutting maneuvers in female athletes

BACKGROUND

Combined knee valgus and tibial internal rotation (VL + IR) moments have been shown to stress the anterior cruciate ligament (ACL) in several in vitro cadaveric studies. To utilize this knowledge for non-contact ACL injury prevention in sports, it is necessary to elucidate how the ground reaction force (GRF) acting point (center of pressure (CoP)) in the stance foot produces combined knee VL + IR moments in risky maneuvers, such as cuttings. However, the effects of the GRF acting point on the development of the combined knee VL + IR moment in cutting are still unknown.

METHODS

We first established the deterministic mechanical condition that the CoP position relative to the tibial rotational axis differentiates the GRF vector's directional probability for developing the combined knee VL + IR moment, and theoretically predicted that when the CoP is posterior to the tibial rotational axis, the GRF vector is more likely to produce the combined knee VL + IR moment than when the CoP is anterior to the tibial rotational axis. Then, we tested a stochastic aspect of our theory in a lab-controlled in vivo experiment. Fourteen females performed 60° cutting under forefoot/rearfoot strike conditions (10 trials each). The positions of lower limb markers and GRF data were measured, and the knee moment due to GRF vector was calculated. The trials were divided into anterior- and posterior-CoP groups depending on the CoP position relative to the tibial rotational axis at each 10 ms interval from 0 to 100 ms after foot strike, and the occurrence rate of the combined knee VL + IR moment was compared between trial groups.

RESULTS

The posterior-CoP group showed significantly higher occurrence rates of the combined knee VL + IR moment (maximum of 82.8%) at every time point than those of the anterior-CoP trials, as theoretically predicted by the deterministic mechanical condition.

CONCLUSION

The rearfoot strikes inducing the posterior CoP should be avoided to reduce the risk of non-contact ACL injury associated with the combined knee VL + IR stress.

Individualized Technique Feedback for Instant Technique Improvements and Knee Abduction Moment Reductions - A New Approach for 'Sidestepping' ACL Injuries?

Background

Sidestep cutting technique is highly individual and has been shown to influence knee joint loading. However, studies assessing whether individualized technique feedback improves technique and ACL injury-relevant knee joint loads instantly in a sport-specific task are lacking.

Purpose

To determine the instant effects of individualized augmented technique feedback and instructions on technique and the peak external knee abduction moment (pKAM) in a handball-specific sidestep cut. Additionally, to determine the effects of technique modifications on the resultant ground reaction force and its frontal plane moment arm to the knee joint center.

Study Design

Controlled laboratory cohort study.

Methods

Three-dimensional biomechanics of 48 adolescent female handball players were recorded during a handball-specific sidestep cut. Following baseline cuts to each side, leg-specific visual and verbal technique feedback on foot strike angle, knee valgus motion, or vertical impact velocity using a hierarchically organized structure accounting for the variables' association with performance was provided. Subsequently, sidestep cuts were performed again while verbal instructions were provided to guide technique modifications. Combined effects of feedback and instructions on technique and pKAM as well as on the resultant ground reaction force and its frontal plane moment arm to the knee joint center were assessed.

Results

On average, each targeted technique variable improved following feedback and instructions, leading to instant reductions in pKAM of 13.4% to 17.1%. High inter-individual differences in response to feedback-instruction combinations were observed. These differences were evident in both the adherence to instructions and the impact on pKAM and its components.

Conclusion

Most players were able to instantly adapt their technique and decrease ACL injury-relevant knee joint loads through individualized augmented technique feedback, thereby potentially reducing the risk of injury. More research is needed to assess the retention of these adaptations and move towards on-field technique assessments using low-cost equipment.

Level of Evidence

Level 3.

Most Anterior Cruciate Ligament Injuries in Professional Athletes Occur Without Contact to the Injured Knee: A Systematic Review of Video Analysis Studies

PURPOSE

To systematically review studies using video analyses to evaluate anterior cruciate ligament (ACL) injury mechanisms in athletes during sport to better understand risk factors and the potential for injury prevention.

METHODS

A literature search was conducted in accordance with the 2020 Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines statement using SCOPUS, PubMed, Medline, and the Cochrane Central Register for Controlled Trials from database inception through June 2023. Inclusion criteria included studies reporting on ACL injury mechanisms occurring in athletes based on video analysis. Athlete demographics, injury mechanisms, position of the lower extremity, and activity at the time of injury were recorded.

RESULTS

A total of 13 studies, consisting of 542 athletes, met inclusion criteria. Most athletes competed at the professional level (91%, n = 495/542), with 79% (n = 422/536) of athletes being male. The most common sports were soccer (33%, n = 178/542) and American football (26%, n = 140/542). The most common injury mechanism was noncontact in 42.9% (n = 230/536) of athletes, followed by indirect contact (32.6%, n = 175/536) and direct contact (22.4%, n = 120/536). The most common position of injury was with a planted foot (91.7%, n = 110/120), full or near-full knee extension (84.4%, n = 49/58), and axial loading (81.3%, n = 87/107). Injuries commonly involved a deceleration/shift in momentum (50.4%, n = 123/244) or pivoting maneuver (36.1%, n = 77/213). At the time of injury, the knee commonly fell into valgus (76.8%, n = 225/293) with associated internal (53.5%, n = 46/86) or external tibiofemoral rotation (57.7%, n = 101/175).

CONCLUSIONS

Most ACL injuries, when evaluated by video analysis, involve professional athletes participating in soccer and American football. The most common injury mechanism occurred without contact with the knee in extension during a deceleration or momentum shift, with resultant valgus and rotational force across the knee.

LEVEL OF EVIDENCE

Level IV, systematic review of Level IV studies.

Extrinsic Risk Factors for Primary Noncontact Anterior Cruciate Ligament Injury in Adolescents Aged between 14 and 18 years: A Systematic Review

BACKGROUND

Adolescents present a high incidence of ACL injury compared with other age groups. Examining the risk factors that predispose adolescents to primary noncontact ACL injury is a key strategy to decrease the number of injuries in this population.

OBJECTIVE

The aim of this systematic review was to summarise the existing literature investigating extrinsic risk factors that have been linked with primary noncontact ACL injury risk (identified either using ACL injury occurrence or using screening tests measuring biomechanical mechanisms for noncontact ACL injury) in adolescents including research investigating: (1) the association between extrinsic risk factors and primary noncontact ACL injury risk; and (2) whether primary noncontact ACL injury risk was different in populations or groups exposed to different extrinsic risk factors in adolescents.

METHODS

The same search strategy was used in MEDLINE, SPORTDiscus, CINAHL, PubMed and Embase. Articles were included if: written in English; published in peer-reviewed journals; investigating and discussing primary noncontact ACL injury risk associated with extrinsic risk factors; they were original research articles with an observational design; and participants presented a mean age ranging between 14 and 18 years. The Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies (QATOCCS) was used to assess the quality and risk of bias of the articles included in this systematic review.

RESULTS

The systematic review included 16 eligible articles published up to August 2022 about extrinsic risk factors for primary noncontact ACL injury including: sport (8 studies); sport exposure amount (5); sport level (3); sport season (1); environment (2); equipment (1). Differences in biomechanical risk factors predisposing to ACL injury were reported by sport in female adolescents playing basketball and soccer; however, no good evidence of differences in primary noncontact ACL injury rate by sport was reported in both male and female adolescents. There was contrasting evidence about associations between sport exposure and biomechanical and neuromuscular risk factors predisposing to ACL injury or primary noncontact ACL injury rate in both male and female adolescent players from different sports. There was weak evidence of differences in biomechanical risk factors predisposing to ACL injury by environmental condition in both male and female adolescents playing soccer and season phase in male adolescents playing basketball. Lastly, few good-quality articles suggested that higher sport level might be associated with increased primary noncontact ACL injury rate in female adolescents playing basketball and floorball and that bracing might not prevent primary noncontact ACL injuries in both male and female adolescent players from different sports.

DISCUSSION

The findings emphasise the need for further research to clarify the evidence about extrinsic risk factors and primary noncontact ACL injury in adolescents to develop ACL injury prevention guidelines that would help practitioners and researchers identify adolescents at risk and design future interventions. Future epidemiological studies should collect data about extrinsic factors as well as data about primary noncontact injury separately from secondary injuries or contact injuries to better inform primary noncontact ACL injury prevention in adolescents.

REGISTRATION

https://doi.org/10.17605/OSF.IO/VM82F (11/08/2021).

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.

Biomechanical behavior of the lower limbs and of the joints when landing from different heights

Landing from a jump is a challenging task as the energy accumulated during the aerial phase of the jump must be fully dissipated by the lower limbs during landing; the higher the jump height, the greater the amount of energy to be dissipated. In the present study, we aim to understand (1) how the biomechanical behavior is tuned as a function of the mechanical demand, and (2) the relationship between the self-selected landing strategy and the behavior of the joints. Fourteen subjects were asked to drop off a box of 10 to 60 cm height and land on the ground. The ground reaction forces and the kinematics were recorded using force plates and a motion capture system. A model was used to estimate the properties, i.e. stiffness and damping, of the lower limbs and of the joints. Our results show that, whatever the amount of energy to be dissipated (i.e. height of the jump), the lower limbs and the anke and knee joints behave first as a spring, then as a spring-damper system. However each joint plays a specific role: during the spring phase, the behaviour of the lower limb is associated with the stiffness of the ankle and with the landing constraints (i.e. force peak and loading rate), while during the spring-damper phase, it is associated with the stiffness of the knee and with the amount of energy to be dissipated. Our findings suggest that constraints and performance result from a distinct control of biomechanical parameters at the joints.

An 8-week injury prevention exercise program combined with change-of-direction technique training limits movement patterns associated with anterior cruciate ligament injury risk

Knee ligament sprains are common during change-of-direction (COD) maneuvers in multidirectional team sports. This study aimed to compare the effects of an 8-week injury prevention exercise program containing COD-specific exercises and a similar program containing linear sprint exercises on injury- and performance-related variables during a 135° COD task. We hypothesized that the COD-specific training would lead to (H1) stronger reductions in biomechanical variables associated with anterior cruciate ligament (ACL) injury risk during COD, i.e. knee abduction moment and angle, hip internal rotation angle and lateral trunk lean, and (H2) more effective improvements in COD performance according to the COD completion time, executed angle, ground contact time, and approach speed. Twenty-two sports science students (40% female) completed biomechanical assessments of COD movement strategies before and after participating in two supervised 25-min training sessions per week over 8 weeks. We observed significant 'training x group' interaction effects in support of H1: the COD-specific training but not the linear sprint training led to reduced peak knee abduction moments (interaction, p = 0.027), initial knee abduction (interaction, p < 0.001), and initial lateral trunk lean angles (interaction, p < 0.001) compared to baseline. Although the COD-specific training resulted in sharper executed angles (interaction, p < 0.001), the sprint-specific training group showed reduced COD completion (interaction, p = 0.037) and ground contact times (interaction, p < 0.001). In conclusion, a combination of generic and COD-specific injury prevention training resulted in COD technique adaptations that can help to avoid ACL injury-prone COD movements but may negatively affect COD speed.

Increased knee torsional misalignment associated with femoral torsion is related to non-contact anterior cruciate ligament injury: a case-control study

BACKGROUND

Altered axial biomechanics of the knee are recognized as a risk factor for non-contact anterior cruciate ligament (ACL) injury. However, the relationship of knee and segmental torsion to non-contact ACL and combined anterolateral ligament (ALL) injury is unclear. This study aims to determine the relationship of knee and segmental torsion to non-contact ACL injury and to explore their relationship with ALL injuries.

METHODS

We divided 122 patients with arthroscopically confirmed non-contact ACL injuries into an ACL injury group (isolated ACL injury, 63 patients) and an ACL + ALL injury group (ACL combined with ALL injury,59 patients). Additionally, 90 normal patients with similar age, gender and body mass index (BMI) were matched as a control group. The tibial tubercle-trochlear groove (TT-TG) distance, distal femoral torsion (DFT), posterior femoral condylar torsion (PFCT) and proximal tibial torsion (PTT) were measured using magnetic resonance imaging (MRI). We assessed the differences between the groups using an independent samples t test and utilized receiver operating characteristic (ROC) curves to determine the cut-off value for the increased risk of ACL injury.

RESULTS

In patients with ACL injury, the measurements of the TT-TG (11.8 ± 3.1 mm), DFT (7.7° ± 3.5°) and PFCT (3.6° ± 1.3°) were significantly higher compared to the control group (9.1 ± 2.4 mm, 6.3° ± 2.7° and 2.8° ± 1.3°, respectively; P < 0.05), but the PTT did not differ between the two groups. The TT-TG, DFT and PFCT were not significantly larger in patients combined with ALL injury. ROC curve analysis revealed ACL injury is associated with TT-TG, DFT and PFCT.

CONCLUSIONS

Knee torsional alignment is associated with ACL injury, predominantly in the distal femur rather than the proximal tibia. However, its correlation with ALL injury remains unclear. These findings may help identify patients at high risk for non-contact ACL injury and inform the development of targeted prevention and treatment strategies.

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.

Internal Rotation Measurement of the Knee with Polymer-Based Capacitive Strain Gauges versus Mechanical Rotation Measurement Taking Gender Differences into Account: A Comparative Analysis

With the conventional mechanical rotation measurement of joints, only static measurements are possible with the patient at rest. In the future, it would be interesting to carry out dynamic rotation measurements, for example, when walking or participating in sports. Therefore, a measurement method with an elastic polymer-based capacitive measuring system was developed and validated. In our system, the measurement setup was comprised of a capacitive strain gauge made from a polymer, which was connected to a flexible printed circuit board. The electronics integrated into the printed circuit board allowed data acquisition and transmission. As the sensor strip was elongated, it caused a change in the spacing between the strain gauge's electrodes, leading to a modification in capacitance. Consequently, this alteration in capacitance enabled the measurement of strain. The measurement system was affixed to the knee by adhering the sensor to the skin in alignment with the anterolateral ligament (ALL), allowing the lower part of the sensor (made of silicone) and the circuit board to be in direct contact with the knee's surface. It is important to note that the sensor should be attached without any prior stretching. To validate the system, an in vivo test was conducted on 10 healthy volunteers. The dorsiflexion of the ankle was set at 2 Nm using a torque meter to eliminate any rotational laxity in the ankle. A strain gauge sensor was affixed to the Gerdii's tubercle along the course of the anterolateral ligament, just beneath the lateral epicondyle of the thigh. In three successive measurements, the internal rotation of the foot and, consequently, the lower leg was quantified with a 2 Nm torque. The alteration in the stretch mark's length was then compared to the measured internal rotation angle using the static measuring device. A statistically significant difference between genders emerged in the internal rotation range of the knee (p = 0.003), with female participants displaying a greater range of rotation compared to their male counterparts. The polymer-based capacitive strain gauge exhibited consistent linearity across all measurements, remaining within the sensor's initial 20% strain range. The comparison between length change and the knee's internal rotation angle revealed a positive correlation (r = 1, p < 0.01). The current study shows that elastic polymer-based capacitive strain gauges are a reliable instrument for the internal rotation measurement of the knee. This will allow dynamic measurements in the future under many different settings. In addition, significant gender differences in the internal rotation angle were seen.

Patellar tendon angle is not elevated in ACL-injured subjects, suggesting methods to correct should focus on prehabilitation and rehabilitation rather than surgery

Purpose

The aim of the study was to explore if the patellar tendon angles (PTAs) is an intrinsic risk factor for anterior cruciate ligament (ACL) rupture. We hypothesised that the PTAs will be increased in ACL rupture patients compared to matched controls.

Methods

We performed a retrospective radiographic cohort study. A cohort of ACL-injured patients between 2019 and 2022 was utilised. The control population, from the same time period, was a consecutive series of 100 patients without ligament or meniscal injuries which were prospectively added to our institutional registry. Posterior tibial slope (PTS), static anterior tibial translation (SATT), patellar tendon to tibial plateau angle (PT-TPA), patellar tendon-tibial shaft angle (PT-TSA) were measured.

Results

A total of 100 patients were included in the control cohort and 110 in the ACL cohort. The PT-TPA was significantly less in the ACL cohort compared to the control cohort, mean and SD of 15.33 (±5.74) versus 13.91 (±5.68), respectively (p = 0.01). PT-TSA was also less in the ACL cohort, mean and SD of 116.15 (±5.89) versus 114.27 (±4.81), however, this failed to reach statistical significance (p = 0.08). The PT-TPA was not correlated with PTS (p = 0.65) and the PT-TSA was inversely correlated with PTS; Pearson correlation coefficient of -0.28 (p < 0.01). The PT-TSA had a greater correlation -0.4 (p < 0.01) with SATT than PTS 0.37 (p < 0.01).

Conclusion

PTAs are not elevated in ACL-injured subjects. While anteriorisation of the tibial tubercle is utilised in dogs to decrease the anterior thrust resulting from the anteriorly directed vector of the quadriceps, this treatment in the humans is not warranted and methods to reduce the PTAs should focus on prehabilitation and rehabilitation.

Level of Evidence

Level III.

Evaluation of the Anterior Cruciate Ligament Injury Risk During a Jump-Landing Task Using 3-Dimensional Kinematic Analysis Versus the Landing Error Scoring System

Background

The Landing Error Scoring System (LESS) has been utilized on the field or in the clinic to identify patients with an increased risk for anterior cruciate ligament (ACL) injuries; however, its validity and efficacy have not been fully confirmed.

Purpose

To assess the efficacy of the LESS in identifying the ACL injury risk by examining the correlation between the LESS score and motion patterns on 3-dimensional kinematic analysis.

Study Design

Controlled laboratory study.

Methods

The jump-landing motion was analyzed for 16 female basketball or badminton players who volunteered to participate in the study. All study participants were aged 19 or 20 years. The sequence of motion was evaluated with the LESS, while kinematic data were simultaneously acquired with a 3-dimensional motion analysis system utilizing the point cluster method. The correlation between the LESS score and knee kinematics was statistically analyzed.

Results

When a LESS score ≥6 was defined to be a risk factor for ACL injuries, 7 of the 16 participants (43.8%) were found to exhibit risky motion patterns. Significant correlations were noted between the LESS score and knee valgus (r = 0.87; P < .0001) and internal tibial rotation (r = 0.57; P = .02) at landing. By contrast, a substantial variability was present in knee flexion, showing no correlation with the LESS score.

Conclusion

Significant correlations were found between the LESS score and knee valgus and internal tibial rotation during a jump-landing task.

Clinical Relevance

The LESS can be regarded as an effective measure to identify risky motion patterns that may increase the likelihood of ACL injuries.

Hop to It! The Relationship Between Hop Tests and The Anterior Cruciate Ligament - Return to Sport Index After Anterior Cruciate Ligament Reconstruction in NCAA Division 1 Collegiate Athletes

Background

Outcomes after anterior cruciate ligament reconstruction (ACLR) may not be optimal, with poor physical and psychological function potentially affecting return to sport (RTS) ability. Understanding the relationship between commonly used hop tests and the Anterior Cruciate Ligament - Return to Sport Index (ACL-RSI) may improve rehabilitation strategies and optimize patient outcomes.

Hypothesis/Purpose

The purpose of this study was to examine the relationship between ACL-RSI scores and limb symmetry index (LSI) for the single hop for distance (SHD), triple hop for distance (THD), crossover hop for distance (CHD), timed 6-meter hop (T6H), and single leg vertical hop (SLVH) in a cohort of National Collegiate Athletic Association (NCAA) Division 1 collegiate athletes after ACLR. The hypothesis was that SLVH LSI would be more highly correlated with ACL-RSI score than all horizontal hop tests.

Study design

Cross-Sectional Study.

Methods

Twenty-one National Collegiate Athletic Association (NCAA) Division 1 collegiate athletes (7 males, 14 females) at 6.62 ± 1.69 months after ACLR were included in this retrospective study. Primary outcomes were ACL-RSI score and LSI for SHD, THD, CHD, T6H, and SLVH. The relationship between ACL-RSI scores and performance on hop tests (LSIs) was evaluated using correlation analysis and step-wise linear regression (p ≤ 0.05).

Results

There were significant correlations found when comparing ACL-RSI and the LSI for SHD (rs = 0.704, p < 0.001), THD (rs = 0.617, p = 0.003), CHD (rs = 0.580, p = 0.006), and SLVH (rs = 0.582, p = 0.006). The CHD explained 66% (R2 value of 0.660) of the variance in the ACL-RSI, while the other hop tests did not add to the predictive model.

Conclusions

Physical function has the capacity to influence psychological status after ACLR. Clinicians should recognize that SLVH, SHD, THD, and CHD are correlated with ACL-RSI and improvements in physical function during rehabilitation may improve psychological status and optimize RTS after ACLR.

Level of evidence

Level 3.

Bone Morphological Characteristics as Risk Factors for Anterior Cruciate Ligament Injury: Comparison Between Contact and Noncontact Injury

Background

Altered bone morphologies are considered risk factors for noncontact anterior cruciate ligament (ACL) injuries.

Purpose/Hypothesis

This study aimed to investigate bone morphological characteristics as risk factors for ACL tears in contact injuries and compare these factors with those for noncontact ACL injuries. We hypothesized that altered bone morphologies would also be risk factors for contact ACL injury.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Enrolled were patients who underwent primary ACL reconstructions between January 2000 and December 2021 within 6 weeks after injury. Patients in the ACL group were classified according to injury mechanism (contact vs noncontact). During the same period, a control group of patients matched by age, height, and body mass index to the ACL group was selected. The lateral femoral condylar ratio (LFCR), notch width index (NWI), and lateral posterior tibial slope (PTS) were measured. Measured parameters were compared between the control, contact, and noncontact groups using analysis of variance.

Results

There were 86 patients in the control group, 102 patients in the contact ACL group, and 105 patients in the noncontact ACL group. The demographic characteristics of the 3 groups did not differ significantly. The contact group had significantly higher LFCRs and lower NWIs compared with the control group (P < .001 and P = .001, respectively). The noncontact group had significantly higher LFCRs and PTSs and lower NWIs compared with the control group (P = .031; P < .001; and P < .001, respectively). The noncontact group had significantly higher PTSs and lower NWIs compared with the contact group (P = .003 and P =.014, respectively). In the contact group, the LFCR, PTS, and NWI were significant risk factors for ACL tears (odds ratio [OR], 1.25 [P < .001]; OR, 1.16 [P = .008]; and OR, 1.27 [P = .001], respectively), and in the noncontact group, the PTS and NWI were significant risk factors for ACL tears (OR, 1.20 [P < .001]; OR, 1.59 [P < .001], respectively).

Conclusion

Altered bone morphological characteristics of the knee were found to be risk factors for ACL tears in contact injuries as well as noncontact injuries. Altered morphology has a more significant effect in noncontact ACL injuries.

A new etiological cause for anterior cruciate ligament injury: E-Scooter

The usage of electric scooters has been popular because it is a cheap and fast transportation method. Its use has increased in recent years because public transportation is less preferred during the covid-19 pandemic and in parallel, the publications reporting e-scooter accidents are increasing. There is no article examining the relationship between e-scooter and anterior cruciate ligament (ACL) injury in current literature. We aim to examine the relationship between e-scooter accidents and ACL injury incidence. Patients over the age of 18 years who applied to our orthopedics outpatient clinic with the diagnosis of ACL injury between January 2019- June 2021 were evaluated. 80 e-scooter accidents resulting with ACL tears were reviewed. The electronic medical records of the patients were reviewed retrospectively. Information about the age, gender, trauma history of the patients, and type of trauma was obtained. Fifty-eight patients had a history of falling while stopping the scooter, and 22 patients had a history of falling after hitting something. Anterior cruciate ligament reconstruction was performed with hamstring tendon grafts in 62(77,5%) of the patients included in the study. 18 (22,5%) patients were followed up with functional physical therapy exercises because they did not want to be operated on. Various bone or soft tissue injuries while using e-scooters have been reported in the literature until now. ACL injury is also seen quite frequently after these traumas, and necessary information and warnings should be given to the users to prevent ACL injuries.

Correlation of Lower Limb Muscle Activity with Knee Joint Kinematics and Kinetics during Badminton Landing Tasks

A study on a single-leg landing task after an overhead stroke in badminton suggests that poor knee biomechanical indicators may be a risk factor for anterior cruciate ligament (ACL) injury. A preventive program targeting neuromuscular control strategies is said to alter the biomechanics of the knee joint and have a beneficial effect on reducing ACL injury. However, the relationship between muscle activity around the knee joint and knee biomechanical risk factors in the badminton landing task is unclear. The purpose of this study was to investigate the relationship between this movement pattern of muscle activity and knee kinematics and kinetics. This experiment analyzed knee muscle activity and biomechanical information in a sample of 34 badminton players (17 male, 17 female) during a badminton landing task. We assessed the relationship between the rectus femoris (RF), medial hamstring (MHAM), lateral hamstring (LHAM), medial gastrocnemius (MGAS), lateral gastrocnemius (LGAS), medial and lateral hamstring to quadriceps co-contraction ratio (MH/Q and LH/Q) with the knee flexion angle, valgus angle, extension moment, valgus moment, and proximal tibial anterior shear force. A moderate negative correlation was found between the peak knee flexion angle and electromyography (EMG) activity in LGAS (r = 0.47, p = 0.0046, R² = 0.23, 95% CI: 0.16 to 0.70). Peak proximal tibial shear force showed strong and positive correlations with RF EMG activity (r = 0.52, p = 0.0016, R² = 0.27, 95% CI: 0.22 to 0.73) and strong and negative correlations with MH/Q (r = 0.50, p = 0.0023, R² = 0.25, 95% CI: 0.20 to 0.72). The knee extension moment showed moderate and positive correlations with RF EMG activity (r = 0.48, p = 0.0042, R² = 0.23, 95% CI: 0.17 to 0.70) and strong and negative correlations with MH/Q (r = 0.57, p = 0.0004, R² = 0.33, 95% CI: 0.29 to 0.76). The peak knee valgus moment showed strong and positive correlations with LH/Q (r = 0.55, p = 0.0007, R² = 0.31, 95% CI: 0.26 to 0.75). Our findings suggest that there is a correlation between lower extremity muscle activity and knee kinematics and kinetics during the single-leg landing task in badminton; therefore, lower extremity muscle activity should be considered when developing rehabilitation or injury prevention programs.

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.

[Research progress of anterior cruciate ligament reconstruction with over-the-top technique]

OBJECTIVE

To review the research progress regarding the over-the-top technique for anterior cruciate ligament (ACL) reconstruction.

METHODS

The relevant literature on ACL reconstruction using the over-the-top technique was analyzed for its evolution, clinical application, advantages, and limitations.

RESULTS

Over-the-top technique for ACL reconstruction is a combined intra- and extra-articular technique. Because it avoids drilling the femoral tunnel, its advantages are mainly highlighted in the protection of the femur. Therefore, it is widely used in children and adolescents with epiphyseal occlusion and in patients with revision reconstruction. In addition, significant improvements in postoperative joint stability, functional scores, and return to exercise rates are found in long-term follow-up studies of patients with primary ACL reconstruction and combined anterolateral tenodesis. However, the technique also has some limitations, such as poor stability of knee flexion after operation, high requirement for graft length, and easy impact of graft in the intercondylar fossa.

CONCLUSION

The current research results show the effectiveness and safety of the over-the-top technique for primary and revision ACL reconstruction, with the advantages of wide application, simple operation, and quick recovery; however, more researches are needed to further optimize the selection of grafts and femoral condyle management problems, and to clarify the long-term effectiveness.

Ultrasound Imaging in Predicting the Autograft Size in Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-Analysis

Anterior cruciate ligament (ACL) reconstruction is widely used to restore knee stability after injury, but the risk of revision surgery increases when the autograft size is inadequate. Ultrasound (US) measurements of preoperative target tendons have been applied to predict the intraoperative autograft size, with various outcomes across different studies. This systematic review and meta-analysis aimed to summarize the evidence and investigate the usefulness of US in predicting autograft size. Electronic databases were searched for relevant studies from inception to 19 January 2022. The primary outcome was the correlation between the preoperative US measurements of donor tendons and intraoperative autograft size. The secondary outcomes encompassed the predictive performance of US for autograft size and the comparison between US and magnetic resonance imaging (MRI) for preoperative tendon measurements. Nine studies, comprising 249 patients, were enrolled. The preoperative US measurements of the donor tendons demonstrated a significant positive correlation with their intraoperative autograft diameter, with a pooled correlation coefficient of 0.443 (95% confidence interval [CI], 0.266−0.591, p < 0.001) for the gracilis and semitendinosus autograft, 0.525 (95% CI, 0.114−0.783, p = 0.015) for the semitendinosus autograft, and 0.475 (95% CI, 0.187−0.687, p = 0.002) for the gracilis autograft. The pooled sensitivity and specificity of US imaging in predicting the autograft diameter were 0.83 (95% CI 0.57−0.95) and 0.70 (95% CI, 0.36−0.91), respectively. Moreover, no significant differences were observed between US and MRI measurements in predicting the sizes of the gracilis and semitendinosus autografts. Preoperative US measurements of the target tendons were moderately correlated with the intraoperative autograft size. US imaging has a discriminative performance similar to that of MRI in predicting the autograft size. A standardized US scanning protocol is needed for future studies to minimize the variations in tendon measurements across different investigators and increase the comparability of US imaging with intraoperative findings.