Non-contact ACL injuries in female athletes: an International Olympic Committee current concepts statement

Individual Variation in Adaptive Ability of the Anticipated Postural Stability During a Dual-Task Single-Leg Landing in Female Athletes

Background

Precise postural control helps prevent anterior cruciate ligament injury. However, it is unknown whether the anticipated postural stability can be improved during a physically uncertain and cognitively demanding task.

Hypothesis

Anticipated postural stability will improve through unanticipated single-leg landing with a rapid foot placement target tracking.

Study Design

Controlled laboratory study.

Methods

A total of 22 healthy female university-level athletes performed a novel dual-task paradigm: an unanticipated single-leg landing with foot placement target tracking. In the normal condition (60 trials), the participants jumped from a 20 cm-high box onto the landing target with their dominant leg as softly as possible. In the subsequent perturbation condition (PC) (60 trials), the initially assigned landing target was abruptly switched randomly, requiring participants to modify their preplanned foot placement position to the newly assigned position. The center-of-pressure trajectory length within the first 100 ms after foot impact (CoP₁₀₀) was calculated as a measure of anticipated postural stability for each trial. In addition, the peak vertical ground-reaction force (Fz_Peak) was quantified to assess landing load, and the degree of postural adaptation during PC was quantified by fitting an exponential function to trial-by-trial changes in CoP₁₀₀. Participants were divided into 2 groups according to increase or decrease in CoP₁₀₀, and results were compared between the groups.

Results

The direction and magnitude of postural sway alterations of the 22 participants showed a spectrum-like variation during the repeated trials. Twelve participants (sway-decreased group) exhibited a gradual reduction in postural sway (CoP₁₀₀) during the PC, while the remaining 10 participants (sway-increased group) showed a gradual increase in CoP₁₀₀. The Fz_Peak during the PC was significantly less in the sway-decreased group compared with the sway-increased group (P < .05).

Conclusion

Variation in the direction and magnitude of postural sway alteration among participants suggested that there was individual variation in an athlete's adaptive ability of the anticipated postural stability.

Clinical Relevance

The novel dual-task paradigm described in this study may be useful for rating individual injury risk based on an athlete's postural adaptation ability and may aid in targeted prevention strategies.

Real-Time Ground Reaction Force and Knee Extension Moment Estimation During Drop Landings Via Modular LSTM Modeling and Wearable IMUs

This work investigates real-time estimation of vertical ground reaction force (vGRF) and external knee extension moment (KEM) during single- and double-leg drop landings via wearable inertial measurement units (IMUs) and machine learning. A real-time, modular LSTM model with four sub-deep neural networks was developed to estimate vGRF and KEM. Sixteen subjects wore eight IMUs on the chest, waist, right and left thighs, shanks, and feet and performed drop landing trials. Ground embedded force plates and an optical motion capture system were used for model training and evaluation. During single-leg drop landings, accuracy for the vGRF and KEM estimation was R2 = 0.88 ± 0.12 and R2 = 0.84 ± 0.14, respectively, and during double-leg drop landings, accuracy for the vGRF and KEM estimation was R2 = 0.85 ± 0.11 and R2 = 0.84 ± 0.12, respectively. The best vGRF and KEM estimations of the model with the optimal LSTM unit number (130) require eight IMUs placed on the eight selected locations during single-leg drop landings. During double-leg drop landings, the best estimation on a leg only needs five IMUs placed on the chest, waist, and the leg's shank, thigh, and foot. The proposed modular LSTM-based model with optimally-configurable wearable IMUs can accurately estimate vGRF and KEM in real-time with relatively low computational cost during single- and double-leg drop landing tasks. This investigation could potentially enable in-field, non-contact anterior cruciate ligament injury risk screening and intervention training programs.

Incidence of anterior cruciate ligament injury patterns in Japanese judo players from a nationwide insurance database

Objective

This study aimed to characterize the age- and sex-specific Anterior cruciate ligament (ACL) injury rates and related injury patterns in judo players in Japan using the nationwide insurance database.

Methods

This was a descriptive epidemiological study. We examined a total of 2142 adolescents with anterior cruciate ligament injuries registered in the insurance system of the Japan Sports Council between January 2009 and December 2018. The age- and sex-specific incidences were estimated for the levels of 7th, 8th, and 9th grades of junior high school and 10th, 11th, and 12th grades of high school. The anterior cruciate ligament injury circumstances were classified into three patterns based on the impact to the involved knee: high-impact valgus force, low-impact trunk displacement, or no-impact knee twisting.

Results

The incidence of anterior cruciate ligament injury from the 7th to 12th grades were 0.5, 0.9, 0.9, 6.9, 8.6, and 6.1 per 1000 athlete-years in male players and 1.3, 3.8, 3.4, 16.8, 19.5, and 13.6 per 1000 athlete-years in female players. The most prevalent injury pattern was a low-impact contact injury (42.6%) with Osoto-gari, followed by a high-impact contact injury (29.8%). The concomitant medial collateral ligament (MCL) injury rate was 18.1%, which was correlated with a high-impact contact injury (p = 0.005) by multiple regression analysis.

Conclusions

The highest incidence of age- and sex-specific anterior cruciate ligament injury was 19.5 per 1000 athlete-years in female high school students in the 11th grade. The most frequent injury pattern was low-impact contact injury with trunk displacement, indicating that trunk stabilization training could help prevent anterior cruciate ligament injury in judo.

Postoperative considerations based on graft type after anterior cruciate ligament reconstruction a narrative review

Background and Objective

Graft selection for anterior cruciate ligament reconstruction (ACLR) affects rehabilitation throughout the course of postoperative care.

Methods

A search of PubMed and EBSCO was performed and abstracts independently reviewed by two authors. This search was also supplemented with additional evidence relevant to each phase of ACLR rehabilitation.

Key Content and Findings

Direct implications of graft type on clinical decisions vary throughout treatment phases, transitioning from potential differences in acute postoperative pain management immediately after surgery to facilitating sufficient and appropriate lower extremity loading in subsequent weeks. Regardless of graft type, surgical limb weakness persists throughout the course of rehabilitation; however, harvest site selection for autografts contributes to disproportionate weakness of the harvested muscle group and the potential for surgical-induced tendinopathy. In later phases of rehabilitation, as athletes are transitioning into return to sport (RTS), treatment decisions and protocols are less affected by graft type but expectations for meeting clinical milestones and the time required to do so does differ between graft types.

Conclusions

Targeted strengthening interventions to address muscle weakness following graft harvest in autografts should be continued throughout the rehabilitation process. Lingering deficits in quadriceps strength symmetry may also influence time to meet progression and RTS criteria following graft harvest from the extensor mechanism.

Lower Limb Anthropometric Profiling in Professional Female Soccer Players: A Proof of Concept for Asymmetry Assessment Using Video Analysis

The objective was to evaluate the clinical joint and limb measures in professional female soccer players. The study was a cross-sectional observational design. It was a preseason clinical setting. The inclusion criteria were outfield professional female soccer players, based in the UK, competing in the highest English league. The exclusion criteria included players who had had surgery in the last six months or had missed a single training session or match due to injury in the previous three months. In terms of the outcome measures, the dependent variables were the true limb length, ankle dorsiflexion, knee flexion and extension, hip flexion, extension, internal rotation and external rotation, and straight leg raise measured using video analysis software. Additionally, passive clinical knee and ankle stability tests were conducted. The independent variables were leg dominance and playing position (defender, midfielder, and attacker). For the results, all the ROM measurements demonstrated limb symmetry (p = 0.621). However, there were significant main effects of the playing position on the ankle dorsiflexion and hip internal rotation, with defenders demonstrating a significantly reduced range of motion in comparison to midfielders and attackers. A notable finding from the bilateral passive stability measures was that 38.3% of players exhibited ankle talar inversion instability when using a talar tilt. In conclusion, bilateral differences do not appear to be apparent in this population; however, positional differences may occur in the ankle and hip range of motion measures. A high proportion of this population may present with passive ankle inversion instability. Future research should consider whether this leads to a higher risk of injury in this population.

Gender Differences in Neuromuscular Control during the Preparation Phase of Single-Leg Landing Task in Badminton

BACKGROUND

Studies on the biomechanical mechanisms of an anterior cruciate ligament (ACL) injury have been extensively studied, but studies on the neuromuscular control-related risk factors for an ACL injury in specific maneuvers have not been reported for badminton players.

STUDY DESIGN

Controlled laboratory study.

METHODS

Sixteen badminton players (8 male, 8 female) performed a single-leg badminton ball landing task, and lower limb muscle activity, kinematic data, and ground reaction force were measured during this procedure using marker-based movement analysis, force plates, and electromyography (EMG). Gender differences in the lower limb kinematic data, mean values of normalized lower limb muscle activation (MVC%), and co-contraction values during the landing preparation phase (100 ms before initial contact) were analyzed using MANOVA.

RESULTS

In the badminton landing task, the knee valgus angle was greater in females than in males (6.27 ± 2.75 vs. 1.72 ± 3.20) in the pre-landing preparation position. Compared to male badminton players, females exhibited greater gluteus maximus (44.92 ± 18.00 vs. 20.34 ± 11.64), rectus femoris (41.56 ± 9.84 vs. 26.14 ± 10.46), and medial gastrocnemius (37.39 ± 17.31 vs. 19.11 ± 11.17) lateral gastrocnemius (36.86 ± 17.82 vs. 13.59 ± 2.71) muscle activity (MVC%).

CONCLUSION

Female badminton players exhibit neuromuscular control strategies that may be inadequate for ACL protection and may be a potential risk factor for a high incidence of ACL injury In the future, when devising injury prevention plans for female badminton players, optimizing neuromuscular control during the pre-landing phase can be targeted.

Improvement Trajectories in Patient-Reported Outcomes Between Males and Females After Anterior Cruciate Ligament Reconstruction

CONTEXT

Patient-reported outcomes (PROs) are used to track recovery and inform clinical decision-making after anterior cruciate ligament reconstruction (ACLR). Whether sex influences the trajectory of improvements in PROs over time post-ACLR remains unclear.

OBJECTIVES

To (1) examine the effect of sex on the association between months post-ACLR and Knee injury and Osteoarthritis Outcome Score (KOOS) Quality of Life (QOL) scores in individuals with ACLR and (2) assess sex differences in the KOOS QOL score at selected timepoints post-ACLR.

DESIGN

Cross-sectional study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 133 females (20± 3 years) and 85 males (22 ± 4 years) within 6 to 60 months of primary, unilateral ACLR.

MAIN OUTCOME MEASURE(S)

The KOOS QOL was completed at a single follow-up timepoint post-ACLR. A multivariate linear regression model was calculated to assess the interaction of sex on the association between months post-ACLR and KOOS QOL score. Sex-specific linear regression models were then used to predict KOOS QOL estimated marginal means at each clinical timepoint (6, 12, 24, 36, 48, and 60 months post-ACLR) and compare the sexes.

RESULTS

In the primary model (R2 = 0.16, P < .0001), a significant interaction existed between sex and time post-ACLR (β = -0.46, P < .01). Greater months post-ACLR were associated with better KOOS QOL scores for males (R2 = 0.29, β = 0.69, P < .001); months post-ACLR was a weaker predictor of KOOS QOL scores for females (R2 = 0.04, β = 0.23, P < .02). Estimated marginal means for KOOS QOL scores were greater for males than females at 36 months (t210 = 2.76, P < .01), 48 months (t210 = 3.02, P < .01), and 60 months (t210 = 3.09, P = .02) post-ACLR.

CONCLUSIONS

Males exhibited PRO improvement post-ACLR as the months post-ACLR increased, whereas females did not demonstrate the same magnitude of linear increase in KOOS QOL score. Females may require extended intervention to improve clinical outcomes post-ACLR and address a plateau in QOL score.

Neuromuscular activity of the lower-extremities during running, landing and changing-of-direction movements in individuals with anterior cruciate ligament reconstruction: a review of electromyographic studies

PURPOSE

Running, jumping/landing and cutting/change of direction (CoD) are critical components of return to sport (RTS) following anterior cruciate ligament reconstruction (ACLR), however the electromyographic (EMG) activity patterns of the operated leg during the execution of these tasks are not clear.

METHODS

A systematic review was conducted to retrieve EMG studies during running, jumping/landing and cutting/(CoD) in ACLR patients. MEDLINE, PubMed, SPORTDiscus and Web of Science databases were searched from 2000 to May, 2022 using a combination of keywords and their variations: "anterior cruciate ligament reconstruction" OR "ACLR", "electromyography" OR "EMG", "running", "jumping" OR "landing", "cutting" OR "change-of-direction" OR "CoD". The search identified studies comparing EMG data during running, landing and cutting/(CoD) between the involved limb and contralateral or control limbs. Risk of bias was assessed and quantitative analyses using effect sizes were performed.

RESULTS

Thirty two studies met the inclusion criteria. Seventy five percent (24/32) of the studies reported altered EMG activity pattern of the ACLR leg during running, jumping/landing and cutting/(CoD) when compared with either the healthy control leg or the contra-lateral leg. Twelve studies showed decreased, delayed or earlier onset and delayed peak in quadriceps EMG activity with small to large effect sizes and 9 studies showed increased, delayed or earlier onset and delayed peak in hamstrings EMG activity with small to large effect sizes. Four studies showed a "hamstrings-dominant" strategy i.e. decreased quadriceps coupled with increased hamstrings EMG activity in both running and jumping/landing irrespective of graft type. One study reported that on the grounds of decreased quadriceps activity, lower hamstrings EMG activity was predictive of ipsilateral re-injury in ACLR patients.

CONCLUSION

This systematic review of Level III evidence showed that the ACLR leg displays decreased quadriceps or increased hamstrings EMG activity or both despite RTS. Simultaneous decreased quadriceps and increased hamstrings EMG activity was shown for both running and jumping/landing. From a clinical perspective this "hamstrings dominant" strategy can serve as a protective mechanism against graft re-injury.

LEVEL OF EVIDENCE

III.

Curves and kinematics: Relationship between the force-time curve and landing ability

Anterior cruciate ligament (ACL) injuries have a significant impact on athletic performance and long-term quality of life. Force plates and qualitative screening tools are feasible and effective screening methods to identify abnormal movement quality associated with increased injury risk. Comparing qualitative assessments of landing ability with force-time curves, may detect unique differences between safe and high-risk athletic movement patterns. The aim of this study was to determine low- and high-risk landing ability from qualitive landing assessments and to examine the resulting force-time curves using functional principal component analysis (fPCA). Thirty-one healthy academy athletes (10 males and 21 females) completed double- and single-leg dominant and non-dominant jump-landing-rebound tasks. All movements were filmed in multiple-planes, and vertical ground reaction forces (vGRF) were simultaneously collected. The Landing Error Scoring System (LESS) and Single-Leg Landing Error Scoring System (SL-LESS) were used to score landing footage. From these scores, athletes were categorized into low-risk and high-risk groups for further analysis. fPCA was used to examine differences between landing quality groups force-time curves. Compared to high-risk landers, low-risk landers demonstrated significantly longer contact times across all movements. Scores from fPC1 revealed safe and high-risk landing techniques expose athletes to significantly different loading patterns during double- and single-leg dominant movements. A significant positive relationship was observed between fPC1 and LESS scores, however this relationship was not observed in both single-leg landing scores. Where possible incorporating curve analysis methods like fPCA into multi-faceted screening approaches may help practitioners uncover unique insights into athletic loading strategies.

Single-leg disuse decreases skeletal muscle strength, size, and power in uninjured adults: A systematic review and meta-analysis

We aimed to quantify declines from baseline in lower limb skeletal muscle size and strength of uninjured adults following single-leg disuse. We searched EMBASE, Medline, CINAHL, and CCRCT up to 30 January 2022. Studies were included in the systematic review if they (1) recruited uninjured participants; (2) were an original experimental study; (3) employed a single-leg disuse model; and (4) reported muscle strength, size, or power data following a period of single-leg disuse for at least one group without a countermeasure. Studies were excluded if they (1) did not meet all inclusion criteria; (2) were not in English; (3) reported previously published muscle strength, size, or power data; or (4) could not be sourced from two different libraries, repeated online searches, and the authors. We used the Cochrane Risk of Bias Assessment Tool to assess risk of bias. We then performed random-effects meta-analyses on studies reporting measures of leg extension strength and extensor size. Our search revealed 6548 studies, and 86 were included in our systematic review. Data from 35 and 20 studies were then included in the meta-analyses for measures of leg extensor strength and size, respectively (40 different studies). No meta-analysis for muscle power was performed due to insufficient homogenous data. Effect sizes (Hedges' g_av ) with 95% confidence intervals for leg extensor strength were all durations = -0.80 [-0.92, -0.68] (n = 429 participants; n = 68 aged 40 years or older; n ≥ 78 females); ≤7 days of disuse = -0.57 [-0.75, -0.40] (n = 151); >7 days and ≤14 days = -0.93 [-1.12, -0.74] (n = 206); and >14 days = -0.95 [-1.20, -0.70] (n = 72). Effect sizes for measures of leg extensor size were all durations = -0.41 [-0.51, -0.31] (n = 233; n = 32 aged 40 years or older; n ≥ 42 females); ≤7 days = -0.26 [-0.36, -0.16] (n = 84); >7 days and ≤14 days = -0.49 [-0.67, -0.30] (n = 102); and >14 days = -0.52 [-0.74, -0.30] (n = 47). Decreases in leg extensor strength (cast: -0.94 [-1.30, -0.59] (n = 73); brace: -0.90 [-1.18, -0.63] (n = 106)) and size (cast: -0.61[-0.87, -0.35] (n = 41); brace: (-0.48 [-1.04, 0.07] (n = 41)) following 14 days of disuse did not differ for cast and brace disuse models. Single-leg disuse in adults resulted in a decline in leg extensor strength and size that reached a nadir beyond 14 days. Bracing and casting led to similar declines in leg extensor strength and size following 14 days of disuse. Studies including females and males and adults over 40 years of age are lacking.

Anterior Cruciate Ligament Reconstruction Using a 4-Strand Semitendinosus Tendon Graft or a Doubled Semitendinosus and Gracilis Tendon Graft: A 4.5-Year Prospective, Randomized, Double-Blind, Parallel-Group Study

BACKGROUND

Hamstring tendon grafts are the most common choice for anterior cruciate ligament (ACL) reconstruction (ACLR). Previous studies have provided evidence that offers conflicting opinions concerning the most favorable graft choice.

PURPOSE

To identify whether the use of a quadrupled semitendinosus tendon (ST) or doubled semitendinosus tendon and gracilis tendon (ST/G) graft provides comparable anterior tibial translation (ATT) with similar functional results and similar donor site morbidity.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

This was a prospective, patient- and surgeon-blinded, randomized trial set in a busy orthopaedic and traumatology department at a university hospital. Between 2015 and 2017, a total of 162 patients with ACL lesions were randomized to undergo ACLR with either a quadrupled ST or doubled ST/G graft. The primary endpoint was ATT assessed with the KT-1000 arthrometer. Clinical outcomes were assessed using the patient-reported outcome measures (PROMs) of the visual analog scale (VAS), International Knee Documentation Committee (IKDC) subjective evaluation form, Knee injury and Osteoarthritis Outcome Score (KOOS), Tegner activity scale, and Lysholm knee scoring scale.

RESULTS

Preoperative demographic data, ATT, and PROM scores showed no significant differences. At 4.5 years, no significant differences were found between the ST and ST/G groups with respect to PROM scores and KT-1000 arthrometer, Lachman test, and pivot-shift test findings. Differences in functional results between groups were significant (muscle strength). Subgroup analysis revealed significantly increased ATT in female patients undergoing ACLR with a quadrupled ST graft during the 4.5-year observation period, as assessed by the KT-1000 arthrometer, as well as inferior KOOS, IKDC, Lysholm, and VAS scores.

CONCLUSION

This study showed a significant increase in ATT as well as inferior results on PROMs during a 4.5-year observation period in female patients undergoing ACLR with a quadrupled ST graft. In male patients, the study provided evidence of the noninferiority of ACLR with an ST graft, with no influence on donor site morbidity.

TRIAL REGISTRATION

clinicaltrials.gov: NCT03626883.

MR Imaging of Acute Knee Injuries: Systematic Evaluation and Reporting

Acute knee injury ranges among the most common joint injuries in professional and recreational athletes. Radiographs can detect joint effusion, fractures, deformities, and malalignment; however, MR imaging is most accurate for radiographically occult fractures, chondral injury, and soft tissue injuries. Using a structured checklist approach for systematic MR imaging evaluation and reporting, this article reviews the MR imaging appearances of the spectrum of traumatic knee injuries, including osteochondral injuries, cruciate ligament tears, meniscus tears and ramp lesions, anterolateral complex and collateral ligament injuries, patellofemoral translation, extensor mechanism tears, and nerve and vascular injuries.

Anterior cruciate ligament reconstruction and concomitant procedures in Finland between 2004 and 2018 based on national registers

BACKGROUND AND PURPOSE

We aimed to assess the incidence of anterior cruciate ligament reconstruction (ACLR) and concomitant procedures in Finland.

PATIENTS AND METHODS

We identified all the patients who underwent ACLR between 2004 and 2018 in Finland using national registry data. Patients with an ICD-10 diagnosis code S83.5 and the NOMESCO operation codes NGE30 or NGE35 were included. We recorded the patient's age, sex, Charlson comorbidity index, and concomitant procedures. NGE30 or NGE35 was defined as the main procedure and all other procedures attached to this procedure were included as concomitant procedures.

RESULTS

Our study included 37,224 ACLRs. The overall incidence of ACLR was 46 (95%CI 34-62) per 105 person-years. This increased from 38 per 105 person-years in 2004 to its peak of 53 in 2014 before decreasing to 47 by 2018. Male patients had a higher overall incidence of ACLR than female patients (61 [CI 47-78] vs. 32 [CI 22-45] per 105 person-years, respectively). However, this difference changed over time: for the males, a decrease in ACLR incidence was observed after 2014, whereas for the females, the trend increased throughout the study period. For both sexes, the highest incidence of ACLRs was in the age group 16-29 years (159 and 71 per 105 person-years, respectively). Concomitant procedures were performed at the time of ACLR in 32% of cases.

CONCLUSION

While the total incidence of ACLR decreased slightly from 2014 to 2018, it increased among women over the full study period, which might be due to increased female participation in contact sports. Special attention should be given to girls' and women's ACL rupture prevention and treatment.

Diagnostic value of the lateral femoral notch sign and kissing contusion in patients with anterior cruciate ligament injuries: a case-control study

INTRODUCTION

The lateral femoral notch sign (LFNS) and the kissing contusion (KC) are two indirect signs of anterior cruciate ligament (ACL) injuries. They can be used to diagnose ACL injuries.

MATERIALS AND METHODS

A total of 1000 patients were enrolled in this study, including 500 patients with ACL injuries who assigned to experimental group and 500 patients with meniscal tear (MT) who allocated to control group. All the patients underwent magnetic resonance imaging (MRI) preoperatively, and the diagnosis was confirmed with the aid of arthroscopy. The depth of LFNS and the presence of KC were determined on MRI findings. The relationship and characteristics between these two indicators was explored.

RESULTS

The notch depth of lateral femoral condyle in the experimental group (0.99 ± 0.56 mm) was significantly greater than that in the control group (0.49 ± 0.28 mm) (P < 0.05). The positive rate of KC in the experimental group (183/500) was markedly higher than that in the control group (3/500) (P < 0.05). The values of notch depth in patients who had ACL rupture concomitant lateral MT injuries and medial collateral ligament (MCL) injuries were 1.12 ± 0.64 and 1.23 ± 0.74 mm, respectively, which were significantly higher than those in patients with only ACL injury (0.89 ± 0.49 mm) (P < 0.05). It also was revealed that when the optimal cut-off point of LFNS was 0.72 mm (area under the curve (AUC) = 81%), the values of specificity and sensitivity were 67% and 84%, respectively. For KC, the corresponding values were 36.6% and 99.4%, respectively. The diagnostic outcome of LFNS was not in agreement with that of KC, as there was a poor coincidence according to the Kappa coefficient (Kappa = 0.155 < 0.4, P = 0.035).

CONCLUSION

The LFNS and KC have strong clinical significance in the diagnosis of ACL injuries. A deeper notch often indicates a more complex knee injury. Notch depth equal to 0.72 mm can be basically considered as the optimal cut-off point for LFNS in statistics.

Motor Competence Among Irish Adolescents: An Investigation of Sex Differences and Relatedness Between Fundamental Movement Skills and Functional Movement

In prior research, Irish youth displayed poor motor competence across fundamental movement skills (FMS) and functional movements (FM). Our purpose in this study was to compare FMS and FM across male and female Irish adolescents and to determine whether there are associations between these movement domains. We collected data on 373 adolescents (178 females; M age = 14.38, SD = 0.87 years) from six Irish secondary schools, including motor competence testing of 10 FMS, and 7 FM. Overall levels of motor competence of both FMS and FM were low, and certain levels of dysfunctional movement were high. We observed significant sex-based differences in both FMS and FM, and there was a moderate association between FMS and FM that warrants further investigation. There is a need for societal intervention and policy changes to address low levels of motor competence among adolescent youth.

Effects of a Football Simulated Exercise on Injury Risk Factors for Anterior Cruciate Ligament (ACL) Injury in Amateur Female Players

Females are more at risk of Anterior Cruciate Ligament (ACL) injuries than males; however, there is limited literature on neuromuscular risk factors such as angle-specific hamstring/quadriceps functional strength ratios (H_ecc/Q_con) and rate of torque development (RTD) in female footballers. The aim of this study was to investigate the effects of fatigue on these neuromuscular risk factors. Thirty-three amateur players (20.3 ± 2.0 years old, 1.67 ± 9.31 m, 63.4 ±8.1 kg, 23.6 ± 5.7% body fat) performed strength assessments of the quadriceps (concentrically, Q_con) and hamstrings (eccentrically, H_ecc) on both legs on an isokinetic dynamometer, before and immediately after a football-specific exercise. Results showed significantly lower peak H_ecc (-15.1 to -15.5%), peak H_ecc/Q_con (-8.8 to -12.9%) and RTD (-14.0 to -17.0%) for hamstring eccentric contractions after fatigue in the dominant and non-dominant legs. Furthermore, significant decreases in H_ecc/Q_con were observed at 10° only in the dominant leg (-15.5%), and at 10°, 20° and 30° in the non-dominant leg (-15.1 to -21.8%). These results suggest a reduced capacity of the hamstrings to stabilise the knee joint with fatigue. Unlike results previously shown on men, the non-dominant leg seemed more affected, highlighting the need to consider specific prevention measures in females.

Loading mechanisms of the anterior cruciate ligament

This review identifies the three-dimensional knee loads that have the highest risk of injuring the anterior cruciate ligament (ACL) in the athlete. It is the combination of the muscular resistance to a large knee flexion moment, an external reaction force generating knee compression, an internal tibial torque, and a knee abduction moment during a single-leg athletic manoeuvre such as landing from a jump, abruptly changing direction, or rapidly decelerating that results in the greatest ACL loads. While there is consensus that an anterior tibial shear force is the primary ACL loading mechanism, controversy exists regarding the secondary order of importance of transverse-plane and frontal-plane loading in ACL injury scenarios. Large knee compression forces combined with a posteriorly and inferiorly sloped tibial plateau, especially the lateral plateau-an important ACL injury risk factor-causes anterior tibial translation and internal tibial rotation, which increases ACL loading. Furthermore, while the ACL can fail under a single supramaximal loading cycle, recent evidence shows that it can also fail following repeated submaximal loading cycles due to microdamage accumulating in the ligament with each cycle. This challenges the existing dogma that non-contact ACL injuries are predominantly due to a single manoeuvre that catastrophically overloads the ACL.

Quadriceps Function and Athletic Performance in Highly Trained Female Athletes

CONTEXT

Quadriceps strength is considered a key contributor to performance in various athletic tasks. Yet, past research has reported conflicting results based on population, with little data available in highly trained female athletes.

DESIGN

Cross-sectional.

METHOD

To examine how athletic performance relates to quadriceps strength and neural function, we measured the quadriceps maximum voluntary isometric contraction force (MVIC) and rate of force development over 0 to 50 ms (rate of force development [RFD]0-50ms), and various performance measures in 34 highly trained female athletes.

RESULTS

Stepwise multiple regression analysis revealed that the quadriceps variables explained 16 of 21 performance variables (R2 = .08-.36, P ≤ .10). Squat performance related to RFD0-50ms alone (R2 = .17-.20, P < .05; βRFD = 0.41 to 0.45, P < .05) but only MVIC explained the variance in sprinting and vertical jump performance (R2 = .08-.34, P ≤ .10; βMVIC = -0.51 to 0.58, P ≤ .10). The broad jump model included both parameters and their interaction (R2 = .20, P = .08; βRFD = 0.06, P = .76; βMVIC = -0.39, P = .03; βRFD×MVIC = -0.24, P = .10).

CONCLUSION

The contribution of the quadriceps MVIC or RFD0-50ms varies in size and nature depending on the task or leg dominance. While quadriceps are significant contributors to performance, because our models leave most of the variance in performance unexplained, rehabilitation and performance professionals should refrain from interpreting peak athletic performance as a reflection of knee-extensors function in highly trained female athletes.

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

BACKGROUND

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

HYPOTHESIS

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

STUDY DESIGN

Descriptive laboratory study.

METHODS

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

RESULTS

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

CONCLUSION

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

CLINICAL RELEVANCE

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

Different patient and activity-related characteristics result in different injury profiles for patients with anterior cruciate ligament and posterior cruciate ligament injuries

PURPOSE

To compare patient characteristics including patient sex, age, body mass index (BMI), activities at the time of injury and injury profiles in patients with anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) injuries.

METHODS

Data were obtained from the Swedish National Knee Ligament Registry. Two study groups were created: (1) index ACL reconstruction (ACL group) and (2) index PCL reconstruction (PCL group). Between-group differences were investigated using Fisher's exact test and Fisher's non-parametric permutation test for dichotomous variables and continuous variables, respectively.

RESULTS

Of 39,010 patients, 38,904 were ACL injuries. A larger proportion of patients with combined injuries to the PCL, meniscus and cartilage were female, aged > 25 years and with a BMI of > 35 kg/m² compared with patients with combined injuries to the ACL, meniscus and cartilage. An isolated ACL injury was more commonly found in males, while all other injury profiles of ACL, including combined injuries with meniscus, cartilage and collateral ligament injuries, were more frequently observed in females. The PCL injuries were sustained either during pivoting sports, non-pivoting sports or were traffic-related.

CONCLUSION

Different patient characteristics (BMI, age and sex), and activities at the time of injury (sport- versus traffic-related activities), resulted in distinct injury profiles for the ACL and PCL groups. These findings provide valuable information of the way specific injury patterns of cruciate ligament injuries occur, and subsequently may help clinicians with the diagnostic process of ACL and PCL injuries.

LEVEL OF EVIDENCE

III.

Sex differences in musculoskeletal injury and disease risks across the lifespan: Are there unique subsets of females at higher risk than males for these conditions at distinct stages of the life cycle?

Sex differences have been reported for diseases of the musculoskeletal system (MSK) as well as the risk for injuries to tissues of the MSK system. For females, some of these occur prior to the onset of puberty, following the onset of puberty, and following the onset of menopause. Therefore, they can occur across the lifespan. While some conditions are related to immune dysfunction, others are associated with specific tissues of the MSK more directly. Based on this life spectrum of sex differences in both risk for injury and onset of diseases, a role for sex hormones in the initiation and progression of this risk is somewhat variable. Sex hormone receptor expression and functioning can also vary with life events such as the menstrual cycle in females, with different tissues being affected. Furthermore, some sex hormone receptors can affect gene expression independent of sex hormones and some transitional events such as puberty are accompanied by epigenetic alterations that can further lead to sex differences in MSK gene regulation. Some of the sex differences in injury risk and the post-menopausal disease risk may be "imprinted" in the genomes of females and males during development and sex hormones and their consequences only modulators of such risks later in life as the sex hormone milieu changes. The purpose of this review is to discuss some of the relevant conditions associated with sex differences in risks for loss of MSK tissue integrity across the lifespan, and further discuss several of the implications of their variable relationship with sex hormones, their receptors and life events.

Measures of Knee Capability in Handball Players Differ by Age: A Cross Sectional Study

The return to sport after knee injury is challenging. This is burdensome for sports with a high incidence of injuries, such as team handball. Various tests guide decision making, but often the athlete's preinjury performance of these measures remains unknown. Moreover, objective return-to-sport criteria of a matching population are missing. The purpose of this study was to evaluate objective measures of knee capability in handball depending on players' age. Two hundred sixty-one handball players performed a functional test battery designed to evaluate knee capability after an anterior cruciate ligament injury: two- and one-legged stability analysis, jumps, speed tests, and agility assessments. For age-specific evaluation, athletes were divided into three age groups (16-19; 20-29;≥30 years). Male players showed differences in two and one-legged jumping height (p<0.02) as well as power per body weight (p<0.01) between age groups. Young female players reached better results in two-and one-legged stability. Besides the quick feet test, results of females did not differ between age groups. Functional knee stability in healthy handball players is partly influenced by age, and females show better results in stability and male athletes in power measurements. This aspect should be considered for return to sports testing and underlines the importance of performance measures in athletic testing.

Association of medial arch support of foot orthoses with knee valgus angle at initial contact during cutting maneuvers in female athletes: a controlled laboratory study

BACKGROUND

The effect of medial arch support foot orthoses on kinematics and kinetics of the knee joint has remained unknown.

METHODS

Sixteen female collegiate-level athletes volunteered to participate. Participants were asked to perform a 30° sidestep cut using orthoses of 3 different medial arch heights, comprising of the following: (1) "low," a full flat foot orthosis without arch support, (2) "mid," a commercially available foot orthosis with general height arch support, and (3) "high," a foot orthosis with double the commercially available height for arch support to observe the effect on the knee when overcorrected. Kinematics and kinetics of the knee joint were collected by a markerless motion capture system with 2 force plates and compared between orthosis types using linear regression analysis, assuming a correlation between the measurements of the same cases in the error term.

RESULTS

The knee valgus angle at initial contact was 2.3 ± 5.2 degrees for "low" medial arch support height, 2.1 ± 5.8 degrees for "mid," and 0.4 ± 6.6 degrees for "high". Increased arch support height significantly decreased the knee valgus angle at initial contact (p = 0.002). Other kinematic and kinetic measurements did not differ between groups.

CONCLUSIONS

The valgus angle of the knee at initial contact was decreased by the height of the medial arch support provided by foot orthosis during cutting manoeuvres. Increasing the arch support height may decrease knee valgus angle at initial contact. Medial arch support of foot orthosis may be effective in risk reduction of ACL injury. Clinical trial registration numbers and date of registration: UMIN000046071, 15/11/2021.

Examining the Effects of Mirror Therapy on Psychological Readiness and Perception of Pain in ACL-Injured Female Football Players

Virtual reality-guided imagery (VRGI) and mirror therapy (MT) have been used in isolation to treat patients suffering from different injuries. However, no attempts have been made to understand the effects of combined VRGI and MT added to conventional physical therapy, and no information exists regarding perceptual responses to these rehabilitation strategies in female football players. Thus, this study aimed to examine the effect of MT added to conventional rehabilitation on psychological readiness and perception of pain in ACL-injured female football players. Thirty ACL-injured female football players competing in the 2nd and 3rd Italian tier who underwent an ACL rehabilitation program from the same clinic participated in this study. Players were randomly distributed in an MT group (n = 15) and a CON group (n = 15). All participants reported their perception of pain on a VAS before and after the interventions and their psychological readiness to return to sport after ACL injury and reconstruction surgery on the ACL-RSI scale after the intervention. An independent-sample t-test was performed to assess between-group differences in post-intervention ACL-RSI, and a further independent-sample t-test to assume non-significant differences between VAS values before the intervention. A two-way repeated-measures analysis of variance was used to test the null hypothesis of no different change in VAS over time between groups. After the intervention, the MT group perceived largely greater psychological readiness (p < 0.01). MT and CON groups experienced a large reduction in VAS after the intervention (p < 0.001). However, a small time × group interaction was observed (p = 0.023). MT reported a greater perception of the psychological readiness of the soccer players and a lower perception of pain than those who performed conventional therapy.

Exploring pre-impact landing kinematics associated with increase and decrease in the anterior cruciate ligament injury risk

This study aimed to explore the single-legged landing kinematics that could lead to increase or decrease in the risk of anterior cruciate ligament (ACL) injury. Immediate pre-impact kinematics at the single-legged landing from 33 healthy young female handball players were evaluated. Thereafter, two-year follow-up for ACL injury incidence was conducted, in which six new ACL injuries in non-dominant leg were registered. The evaluation of pre-impact kinematics across participants was performed first by the principal component analysis to decompose them into the kinematic components (KCs), and then by the linear discrimination analysis (LDA) for a set of KC-scores to obtain important KCs for discriminating injured and non-injured legs. The result of LDA showed that the combination of second major KC (knee flexion/extension angle and angular velocity) and some minor KCs such as torso medial/lateral leaning accurately discriminated the injured and non-injured legs with the error rate of 12.5%. To examine the mechanisms of this discriminative ability, we generated hypothetical pre-impact kinematics in the subspaces spanned by eigenvectors of multiple KCs, and examined relationships between pre-impact kinematics and the corresponding knee valgus torque predicted by the motion-equation-based model. The result showed that the second major KC and the minor KCs representing torso medial/lateral leaning and/or hip adduction/abduction angle, which contributed in LDA to discriminating injured legs, also significantly affected the frontal-plane knee loading patterns. These findings suggested that KC-based postural characterization of the pre-impact landing kinematics and the motion-equation-based knee stress quantification possibly explain the future ACL injury risks of female athletes.

Intrinsic Risk Factors for Ankle Sprain Differ Between Male and Female Athletes: A Systematic Review and Meta-Analysis

Background

Ankle sprains remain prevalent across most team sports. However, despite divergent ankle sprain injury rates in male and female athletes, little is known about potential sex-specific risk factors for ankle sprain.

Objective

To systematically investigate the sex-specific risk factors for ankle sprain.

Methods

Combinations of the key terms were entered into PubMed, Web of Science, Embase and Cochrane Library databases, and prospective studies reporting ankle sprain risk factors in males or females were included for meta-analysis.

Results

Sixteen studies were eligible for inclusion, for a total of 3636 athletes (735 female) and 576 ankle sprains (117 female). Out of 21 prognostic factors, previous ankle sprain injury (odds ratio = 2.74, P < .001), higher body mass index (SMD = 0.50, P < 0.001), higher weight (SMD = 0.24, P = 0.02), lower isometric hip abduction strength (SMD = − 0.52, P < 0.0001) and lower dynamic balance performance (SMD = − 0.48 to − 0.22, P < 0.001–0.04) were identified as risk factors in male athletes. In female athletes, out of 18 factors eligible for meta-analysis, only lower concentric dorsiflexion strength was identified as a risk factor (SMD = − 0.48, P = 0.005).

Conclusion

This meta-analysis provides novel evidence for different risk factor profiles for ankle sprain injuries between female and male athletes. Further studies, particularly in female athletes, are needed to strengthen the evidence.

Comparison of the Effectiveness of Two Management Strategies in the Pandemic COVID-19 Period in Patient Visits (Face-to-Face Visits vs. a Smartphone) in follow-up the Range of Motion of the Knee in Patients with Anterior Cruciate Ligament Reconstruction

Background

As the prevalence of the coronavirus increases, there is now more emphasis on reducing "face-to-face" patient visits. Therefore, the use of smartphones and their special medical applications can play an important role in following up patients. The aim of this study was to evaluate the use of smartphone in evaluating clinical outcomes and range of motion (ROM) of patients after anterior cruciate ligament reconstruction (ACLR).

Materials and Methods

From January to December 2020, 112 patients between 20 and 50 years old were randomly selected at our orthopedic sports center. All patients were visited online through smartphone by a knee fellowship surgeon in the morning (case group) and again all of them were visited online through smartphone in the evening by another knee fellowship surgeon (control group). Both visits were done at regular intervals in the 2^nd, 6^th, and 12^th week after surgery. Patients were evaluated for function outcomes and joint ROM.

Results

The two groups were similar in terms of mean International Knee Documentation Committee score, Lysholm knee score, and Tegner Knee Score and did not show statistically significant difference (P < 0.05) There was no significant difference in knee ROM measurements between the two groups (face-to-face visits and online through smartphone visits) during the follow-ups (P > 0.05).

Conclusion

Smartphone apps are highly effective in assessing postoperative condition of knee ROM after ACLR, especially in the short time. However, this ability has been reduced in evaluating the long term. Hence, evaluation is still necessary through direct examination in the presence visit.

Unanticipated fake-and-cut maneuvers do not increase knee abduction moments in sport-specific tasks: Implication for ACL injury prevention and risk screening

Non-contact anterior cruciate ligament injuries typically occur during cutting maneuvers and are associated with high peak knee abduction moments (KAM) within early stance. To screen athletes for injury risk or quantify the efficacy of prevention programs, it may be necessary to design tasks that mimic game situations. Thus, this study compared KAMs and ranking consistency of female handball players in three sport-specific fake-and-cut tasks of increasing complexity. The biomechanics of female handball players (n = 51, mean ± SD: 66.9 ± 7.8 kg, 1.74 ± 0.06 m, 19.2 ± 3.4 years) were recorded with a 3D motion capture system and force plates during three standardized fake-and-cut tasks. Task 1 was designed as a simple pre-planned cut, task 2 included catching a ball before a pre-planned cut in front of a static defender, and task 3 was designed as an unanticipated cut with three dynamic defenders involved. Inverse dynamics were used to calculate peak KAM within the first 100 ms of stance. KAM was decomposed into the frontal plane knee joint moment arm and resultant ground reaction force. RANOVAs (α ≤ 0.05) were used to reveal differences in the KAM magnitudes, moment arm, and resultant ground reaction force for the three tasks. Spearman's rank correlations were calculated to test the ranking consistency of the athletes' KAMs. There was a significant task main effect on KAM (p = 0.02;η p 2 = 0.13). The KAM in the two complex tasks was significantly higher (task 2: 1.73 Nm/kg; task 3: 1.64 Nm/kg) than the KAM in the simplest task (task 1: 1.52 Nm/kg). The ranking of the peak KAM was consistent regardless of the task complexity. Comparing tasks 1 and 2, an increase in KAM resulted from an increased frontal plane moment arm. Comparing tasks 1 and 3, higher KAM in task 3 resulted from an interplay between both moment arm and the resultant ground reaction force. In contrast to previous studies, unanticipated cutting maneuvers did not produce the highest KAMs. These findings indicate that the players have developed an automated sport-specific cutting technique that is utilized in both pre-planned and unanticipated fake-and-cut tasks.

Assessment Of Femoral Notch Morphology In Male Patients With Anterior Cruciate Ligament Injury: An MRI Study

Aim: The objective of the present study was to evaluate the femoral notch type, notch width index (NWI), notch angle (NA) and α angle in patients with ACL injury and compare with nonathletic male population using magnetic resonance imaging (MRI). Methods: 79 patients with complete ACL tear and 80 patients as control group (aged 19-43 years) who had knee MRI were evaluated. NWI, NA measurements and notch shape were evaluated on axial fat-saturated proton-weighted sequences. Femoral notch shape was classified as A, U and W types. Results: A statistically significant association was found between notch type, NWI, NA and ACL injury (p

Injury prevention programs that include plyometric exercises reduce the incidence of anterior cruciate ligament injury: a systematic review of cluster randomised trials

QUESTION

Do injury prevention programs that include plyometric exercises reduce the incidence of anterior cruciate ligament (ACL) injuries in sport?

DESIGN

Systematic review of (cluster) randomised trials with meta-analysis.

PARTICIPANTS

Sporting participants of any age, sex or competition level.

INTERVENTIONS

The experimental intervention was an injury prevention program that included plyometric exercises. The control intervention was the usual warm-up program, which did not include plyometric exercises.

OUTCOME MEASURES

Exposure-based ACL injury rates.

RESULTS

The initial search yielded 7,302 articles, of which nine met the inclusion criteria. All nine articles reported cluster randomised trials, providing data on 14,394 participants. The pooled results showed that injury prevention programs that include plyometric exercises reduce the risk of ACL injury by 60% per 1,000 hours of exposure compared with the control group, with an injury risk ratio (IRR) of 0.40 (95% CI 0.26 to 0.63). Data from subgroups of these trials estimated that this preventative effect may be stronger in males (IRR 0.21, 95% CI 0.07 to 0.62) and weaker in females (IRR 0.51, 95% CI 0.30 to 0.87), albeit with less precise estimates. Subgroup analysis also suggested a stronger effect on non-contact ACL injuries (IRR 0.34, 95% CI 0.18 to 0.65), whereas the effect on contact ACL injuries remained uncertain (IRR 0.59, 95% CI 0.15 to 2.30).

CONCLUSIONS

Injury prevention programs that incorporate plyometric exercises substantially decrease the risk of ACL injuries more than warm-up programs that do not include plyometric exercises. The preventive effect appears to be stronger among males and in the prevention of ACL injuries that do not involve contact with another player. PROSPERO CRD42020196982.

Athletes with high knee abduction moments show increased vertical center of mass excursions and knee valgus angles across sport-specific fake-and-cut tasks of different complexities

Young female handball players represent a high-risk population for anterior cruciate ligament (ACL) injuries. While the external knee abduction moment (KAM) is known to be a risk factor, it is unclear how cutting technique affects KAMs in sport-specific cutting maneuvers. Further, the effect of added game specificity (e.g., catching a ball or faking defenders) on KAMs and cutting technique remains unknown. Therefore, this study aimed: (i) to test if athletes grouped into different clusters of peak KAMs produced during three sport-specific fake-and-cut tasks of different complexities differ in cutting technique, and (ii) to test whether technique variables change with task complexity. Fifty-one female handball players (67.0 ± 7.7 kg, 1.70 ± 0.06 m, 19.2 ± 3.4 years) were recruited. Athletes performed at least five successful handball-specific sidestep cuts of three different complexities ranging from simple pre-planned fake-and-cut maneuvers to catching a ball and performing an unanticipated fake-and-cut maneuver with dynamic defenders. A k-means cluster algorithm with squared Euclidean distance metric was applied to the KAMs of all three tasks. The optimal cluster number of koptimal = 2 was calculated using the average silhouette width. Statistical differences in technique variables between the two clusters and the tasks were analyzed using repeated-measures ANOVAs (task complexity) with nested groupings (clusters). KAMs differed by 64.5%, on average, between clusters. When pooling all tasks, athletes with high KAMs showed 3.4° more knee valgus, 16.9% higher downward and 8.4% higher resultant velocity at initial ground contact, and 20.5% higher vertical ground reaction forces at peak KAM. Unlike most other variables, knee valgus angle was not affected by task complexity, likely due to it being part of inherent movement strategies and partly determined by anatomy. Since the high KAM cluster showed higher vertical center of mass excursions and knee valgus angles in all tasks, it is likely that this is part of an automated motor program developed over the players' careers. Based on these results, reducing knee valgus and downward velocity bears the potential to mitigate knee joint loading and therefore ACL injury risk.

Consensus Delphi study on guidelines for the assessment of anterior cruciate ligament injuries in children

Background: Knee examination guidelines in minors are intended to aid decision-making in the management of knee instability. Clinical question: A Delphi study was conducted with a formal consensus process using a validated methodology with sufficient scientific evidence. A group consensus meeting was held to develop recommendations and practical guidelines for use in the assessment of instability injuries in children. Key findings: there is a lack of evidence to analyse anterior cruciate ligament injuries in children and their subsequent surgical management if necessary. Diagnostic guidelines and clinical assessment of the patient based on a thorough examination of the knee are performed and a guide to anterior cruciate ligament exploration in children is developed. Clinical application: In the absence of a strong evidence base, these established guidelines are intended to assist in that decision-making process to help the clinician decide on the most optimal treatment with the aim of benefiting the patient as much as possible. Following this expert consensus, surgical treatment is advised when the patient has a subjective sensation of instability accompanied by a pivot shift test ++, and may include an anterior drawer test + and a Lachman test +. If these conditions are not present, the conservative approach should be chosen, as the anatomical and functional development of children, together with a physiotherapy programme, may improve the evolution of the injury.

Effects of a soccer-specific vertical jump on lower extremity landing kinematics

Anterior cruciate ligament (ACL) injury frequently occurs in female soccer athletes during deceleration movements such as landings. In soccer, landings mostly occur following jumping headers. Little research has been done to determine the mechanics that follow and how they compare to standard drop vertical jumps (DVJ). The purpose of this study was to analyze differences in kinematics between the DVJ and the soccer-specific vertical jump (SSVJ) in female soccer athletes to better assess the sport-specific risk for ACL injury. A secondary aim was to compare second landings (L2) to first landings (L1). Eight female recreational soccer athletes performed DVJs and SSVJs initiated from a 31 ​cm height. Motion capture was performed during landings and data were analyzed using repeated-measures ANOVA. SSVJs produced less peak hip flexion (p ​= ​0.03) and less peak knee flexion (p ​= ​0.002) than DVJs. SSVJs also demonstrated increased ankle plantarflexion at initial contact (IC) than DVJs (p ​= ​0.005). L2s produced less peak hip (p ​= ​0.007) and knee flexion (p ​= ​0.002) than L1s. SSVJs and L2s displayed a more erect landing posture than the DVJs and L1s at the hip and knee, a known ACL risk factor. The significant results between jump styles show that the SSVJ displays mechanics that are different from the DVJ. The SSVJ may be a better sport-specific screening tool for ACL injury mechanisms than the DVJ in soccer athletes as it has a more direct translation to the sport.

Age- and Sex-Specific Joint Biomechanics in Response to Partial and Complete Anterior Cruciate Ligament Injury in the Porcine Model

CONTEXT

Pediatric anterior cruciate ligament (ACL) injury rates are increasing and are highest in female adolescents. Complete ACL tears are typically surgically reconstructed, but few guidelines and very limited data exist regarding the need for surgical reconstruction or rehabilitation for partial ACL tears in skeletally immature patients.

OBJECTIVE

To evaluate the effects of partial (anteromedial bundle) and complete ACL transection on joint laxity and tissue forces under anterior and rotational loads in male and female stifle joints throughout skeletal growth in the porcine model.

DESIGN

Descriptive laboratory study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

We studied 60 male and female Yorkshire crossbreed pigs aged 1.5, 3, 4.5, 6, and 18 months (n = 6 pigs per age per sex).

MAIN OUTCOME MEASURE(S)

Joint laxity was measured in intact, anteromedial bundle-transected, and ACL-transected joints under applied anterior-posterior drawer and varus-valgus torque using a robotic testing system. Loading of the soft tissues in the stifle joint was measured under each condition.

RESULTS

Anterior-posterior joint laxity increased by 13% to 50% (P < .05) after anteromedial bundle transection and 75% to 178% (P < .05) after ACL transection. Destabilization after anteromedial bundle transection increased with age (P < .05) and was greater in late female than late male adolescents (P < .05). In anteromedial bundle-transected joints, the posterolateral bundle resisted the anterior load. In ACL-transected joints, the medial collateral ligament (MCL) contribution was largest, followed by the medial meniscus. The MCL contribution was larger and the medial meniscus contribution was smaller in male versus female specimens.

CONCLUSIONS

Partial ACL transection resulted in moderate increases in joint laxity, with the remaining bundle performing the primary ACL function. Destabilization due to partial ACL transection (anteromedial bundle) was largest in late adolescent joints, indicating that operative treatment should be considered in active, late-adolescent patients with this injury. Increased forces on the MCL and medial meniscus after ACL transection suggested that rehabilitation protocols may need to focus on protecting these tissues.

Myofascial and Movement Tests after Anterior Cruciate Ligament Reconstruction

Functional evaluation after anterior cruciate ligament reconstruction is one of the key points involved in decision making about the return of patients to full and unrestricted physical activity. The objective of the present study was to verify whether myofascial chain NEURAC^® and Functional Movement Screen (FMS™) tests can be used to detect functional differences between the operated and the non-operated extremity in patients after anterior cruciate ligament reconstruction. A total of 83 young and physically active recreational athletes (mean age: 26.9 ± 9.7 years) who underwent primary single-bundle anterior cruciate ligament reconstruction using an autogenous semitendinosus-gracilis tendon graft were evaluated between the 3^rd and the 4^th month after surgery. Subjects received a similar, standardised rehabilitation programme. Two experienced raters, blinded to the objective of this study, were involved in functional outcome data collection using myofascial NEURAC^® and Functional Movement Screen tests. Only two of the NEURAC^® tests showed significant differences in the results between the operated and the non-operated extremity: the supine bridging (mean 2.92 vs. 3.51 points, p < 0.001) and prone bridging (mean 2.76 vs. 3.67 points, p < 0.001) tests. Additionally, the summary score of all NEURAC^® tests significantly differed between extremities (mean 12.08 for the operated vs. 13.67 points for the non-operated extremity, p < 0.001). Myofascial tests (supine and prone bridging) in comparison with a battery of Functional Movement Screen tests seem to be more effective in detecting functional differences between the operated and the non-operated extremity at the early stage of recovery after anterior cruciate ligament reconstruction.

Sex-specific biomechanics and morphology of the anterior cruciate ligament during skeletal growth in a porcine model

Pediatric anterior cruciate ligament (ACL) injuries are on the rise, and females experience higher ACL injury risk than males during adolescence. Studies in skeletally immature patients indicate differences in ACL size and joint laxity between males and females after the onset of adolescence. However, functional data regarding the ACL and its anteromedial and posterolateral bundles in the pediatric population remain rare. Therefore, this study uses a porcine model to investigate the sex-specific morphology and biomechanics of the ACL and its bundles throughout skeletal growth. Hind limbs from male and female Yorkshire pigs aged early youth to late adolescence were imaged using magnetic resonance imaging to measure the size and orientation of the ACL and its bundles, then biomechanically tested under anterior-posterior drawer using a robotic testing system. Joint laxity decreased (p < 0.001) while joint stiffness increased (p < 0.001) throughout skeletal growth in both sexes. The ACL was the primary stabilizer against anterior tibial loading, while the functional role of the anteromedial bundle increased with age (p < 0.001), with an earlier increase in males. ACL and posterolateral bundle cross-sectional area and ACL and anteromedial bundle length were larger in males than females during adolescence (p < 0.01 for all), while ACL and bundle sagittal angle remained similar between sexes. Additionally, in situ ACL stiffness versus cross-sectional area regressions were significant across skeletal growth (r²  = 0.75, p < 0.001 in males and r²  = 0.64, p < 0.001 in females), but not within age groups. This study has implications for age and sex-specific surgical intervention strategies and suggests the need for human studies.

Rates of Anterior Cruciate Ligament Rerupture in Adolescent Patients with and without Patella Alta

The objective of this study was to compare rates of anterior cruciate ligament (ACL) failure among adolescent patients to evaluate patella alta as a high-risk variable. Demographic and surgical data were retrospectively queried for patients ≤18 years of age with primary ACL reconstruction performed at a single academic center between 2011 and 2016 and minimum of 2-year clinical surveillance. Patellar height indices, including Caton-Deschamps index (CDI) and Insall-Salvati index (ISI), were retrospectively calculated from preoperative imaging to assess the presence of patella alta. Failure was defined as (1) ACL graft rerupture, (2) Lachman's grade 2 + , (3) presence of pivot shift, and (4) side-to-side difference of 3 mm on KT-1000 arthrometer. A total of 184 patients (84 females and 100 males) and 192 knees were identified, with an average age of 16.2 ± 1.8 years. Of these, 30 (15.63%) experienced ACL failure. Male sex was the only significant risk factor for rerupture (p = 0.026). The mean CDI was 1.06 ± 0.17 and mean ISI was 1.04 ± 0.15. Of the 49 knees that met criteria for patella alta on radiographic evaluation, rerupture occurred in seven (14.29%). Patella alta was not a significant risk factor for ACL failure among adolescent patients (p = 0.359 and 0.277). Only male sex was associated with increased rates of ACL failure. Age, graft selection technique, fixation construct, and presence of patella alta were not risk factors for reinjury. This study is a therapeutic case series and reflects level of evidence IV.

Automatic segmentation model of intercondylar fossa based on deep learning: a novel and effective assessment method for the notch volume

BACKGROUND

Notch volume is associated with anterior cruciate ligament (ACL) injury. Manual tracking of intercondylar notch on MR images is time-consuming and laborious. Deep learning has become a powerful tool for processing medical images. This study aims to develop an MRI segmentation model of intercondylar fossa based on deep learning to automatically measure notch volume, and explore its correlation with ACL injury.

METHODS

The MRI data of 363 subjects (311 males and 52 females) with ACL injuries incurred during non-contact sports and 232 subjects (147 males and 85 females) with intact ACL were retrospectively analyzed. Each layer of intercondylar fossa was manually traced by radiologists on axial MR images. Notch volume was then calculated. We constructed an automatic segmentation system based on the architecture of Res-UNet for intercondylar fossa and used dice similarity coefficient (DSC) to compare the performance of segmentation systems by different networks. Unpaired t-test was performed to determine differences in notch volume between ACL-injured and intact groups, and between males and females.

RESULTS

The DSCs of intercondylar fossa based on different networks were all more than 0.90, and Res-UNet showed the best performance. The notch volume was significantly lower in the ACL-injured group than in the control group (6.12 ± 1.34 cm3 vs. 6.95 ± 1.75 cm3, P < 0.001). Females had lower notch volume than males (5.41 ± 1.30 cm3 vs. 6.76 ± 1.51 cm3, P < 0.001). Males and females who had ACL injuries had smaller notch than those with intact ACL (p < 0.001 and p < 0.005). Men had larger notches than women, regardless of the ACL injuries (p < 0.001).

CONCLUSION

Using a deep neural network to segment intercondylar fossa automatically provides a technical support for the clinical prediction and prevention of ACL injury and re-injury after surgery.

Prevention of Non-Contact Anterior Cruciate Ligament Injuries among Youth Female Athletes: An Umbrella Review

Anterior cruciate ligament (ACL) injuries account for a large percentage of knee injuries, disproportionately affecting female athletes. To help health professionals stay current, we performed an umbrella review to evaluate the effectiveness of ACL injury prevention programs in reducing non-contact ACL injury rates, determine the effective components within interventions, and provide clinical recommendations. Twelve databases (Medline, Embase, Cochrane Database of Systematic Reviews, SPORTDiscus, Cumulative Index to Nursing and Allied Health Literature, PEDro, Web of Science Core Collection, Epistemonikos, TRIP, BC Guidelines and Protocols, CPG Infobase, ProQuest Dissertations and Theses Global) were searched in May 2021 to identify relevant systematic reviews and meta-analyses. Four databases were searched again in September 2021 to identify recent primary literature. Non-contact ACL injury data were extracted to calculate incidence rate ratios (IRRs) and these were combined using an inverse variance random-effects model. A qualitative assessment of included reviews was performed. The methodological quality of the studies was assessed using a Measurement Tool to Assess Systematic Reviews 2 (AMSTAR 2) or Cochrane Risk-of-Bias Tool for Randomized Trials (RoB 2). Sixteen reviews and two primary studies met the inclusion criteria. Across 11 primary studies, prevention programs were effective in reducing non-contact ACL injuries by 64% (IRR = 0.36 (95% CI: 0.18-0.70)). A multi-faceted exercise program, beginning in the pre-season and containing at least three exercise types, may be beneficial in reducing ACL injury risk.

Anterior Cruciate Ligament Reconstruction Surgery: Creating a Permissive Healing Phenotype in Military Personnel and Civilians for Faster Recovery

Introduction

Anterior cruciate ligament (ACL) rupture in military personnel and civilians can be a devastating injury. A service member is 10 times more likely to suffer an ACL injury than their civilian counterparts, and despite successful surgical stabilization, 4%-35% will develop arthrofibrosis, over 50% will not return to full active duty, and up to 50% will develop post-traumatic osteoarthritis (PTOA) within 15 years. Equally concerning, woman are 2 to 8 times more likely to experience ACL injuries than men, which represents a major knowledge gap.

Materials and Methods

A comprehensive literature search was performed in December 2021 using structured search terms related to prevalence, risk factors, disease progression, and treatment of ACL injury and reconstruction. The literature search was conducted independently by two researchers using PubMed, Cochrane, and Embase databases, with inclusion of articles with military, civilian, and sex relevance, and exclusion of most papers with a publication date greater than 10 years. The resources used for the review reflect the most current data, knowledge, and recommendations associated with research and clinical findings from reliable international sources.

Results

Currently, there is no effective system-based drug therapy that creates a “permissive environment” to reduce synovial and cartilage stress after ACL injury and reconstruction and prevent secondary complications. We argue that progress in this area has been hampered by researchers and clinicians failing to recognize that (1) an ACL injury is a system’s failure that affects the whole joint, (2) the early molecular events define and perpetuate different injury phenotypes, (3) male and female responses may be different and have a molecular basis, (4) the female phenotype continues to be under-represented in basic and clinical research, and (5) the variable outcomes may be perpetuated by the trauma of surgery itself. The early molecular events after ACL injury are characterized by an overexpression of joint inflammation, immune dysfunction, and trauma-induced synovial stress. We are developing an upstream adenosine, lidocaine, and magnesium therapy to blunt these early molecular events and expedite healing with less arthrofibrosis and early PTOA complications.

Conclusions

ACL injuries continue to be a major concern among military personnel and civilians and represent a significant loss in command readiness and quality of life. The lack of predictability in outcomes after ACL repair or reconstruction underscores the need for new joint protection therapies. The male–female disparity requires urgent investigation.

Testing a Quaternion Conversion Method to Determine Human Three-Dimensional Tibiofemoral Angles During an In Vitro Simulated Jump Landing

Lower limb joint kinematics have been measured in laboratory settings using fixed camera-based motion capture systems; however, recently inertial measurement units (IMUs) have been developed as an alternative. The purpose of this study was to test a quaternion conversion (QC) method for calculating the three orthogonal knee angles during the high velocities associated with a jump landing using commercially available IMUs. Nine cadaveric knee specimens were instrumented with APDM Opal IMUs to measure knee kinematics in one-legged 3-4× bodyweight simulated jump landings, four of which were used in establishing the parameters (training) for the new method and five for validation (testing). We compared the angles obtained from the QC method to those obtained from a commercially available sensor and algorithm (APDM Opal) with those calculated from an active marker motion capture system. Results showed a significant difference between both IMU methods and the motion capture data in the majority of orthogonal angles (p < 0.01), though the differences between the QC method and Certus system in the testing set for flexion and rotation angles were smaller than the APDM Opal algorithm, indicating an improvement. Additionally, in all three directions, both the limits of agreement and root-mean-square error between the QC method and the motion capture system were smaller than between the commercial algorithm and the motion capture.

Disrupted knee - disrupted me: a strenuous process of regaining balance in the aftermath of an anterior cruciate ligament injury

Background

Individuals describe both short and long term consequences after an anterior cruciate ligament (ACL) injury. Functional impairments are well documented while psychological, social and contextual factors need to be further investigated. By the use of a qualitative method incorporating a biopsychosocial lens, we aimed to explore individuals’ experiences of living and coping with an ACL rupture with a specific focus on experiences significant to overall life, activity in daily living and physical activity more than one year after injury.

Methods

Twelve participants were chosen strategically by a purposive sampling. Four men and eight women (19–41 years) with an ACL rupture 2–25 years ago, were included. Semi-structured interviews were used and analysed with qualitative content analysis.

Results

The results consisted of one overarching theme: ‘A strenuous process towards regaining balance’ which built on three categories ‘Disrupted knee’, ‘Disrupted me’ and ‘Moving forward with new insights’. The overarching theme captures the participants’ experiences of a strenuous process towards regaining both physical and mental balance in the aftermath of an ACL injury. The results illuminate how participants were forced to cope with a physically ‘disrupted knee’, as well as facing mental challenges, identity challenges and a ‘disrupted me’. By gradual acceptance and re-orientation they were moving forward with new insights – although still struggling with the consequences of the injury.

Conclusions

Individuals with an ACL injury experience both physical, psychological, and social challenges several years after injury. In addition to the functional impairments, diverse psychological, social and contextual ‘disruptions’ and struggles may also be present and influence the rehabilitation process. It is important that physiotherapists identify individuals who face such challenges and individually tailor the rehabilitation and support. A biopsychosocial approach is recommended in the clinical practice and future studies focusing on psychosocial processes in the context of ACL rehabilitation are warranted.

Influence of the site of injury on the spontaneous healing response in a rat model of total rupture of the anterior cruciate ligament

AIM

The healing ability of the anterior cruciate ligament (ACL) injury is very poor; however, it has recently been shown to undergo self-healing with conservative treatments. In this study, we evaluated the influence of the site of injury on the healing process after complete transverse tear of ACL using a rat model.

MATERIALS AND METHODS

A total of 58 skeletally mature Wistar rats were randomly assigned to various ACL injury groups: controlled abnormal movement-mid-portion (CAM-MP), controlled abnormal movement-femoral side (CAM-FS), ACL transection-mid-portion (ACLT-MP), or ACL transection-femoral side (ACLT-FS) injury groups. The ACL was completely transected in the mid-portion in the ACLT-MP and CAM-MP groups, and on the femoral side in the ACLT-FS and CAM-FS groups. Both CAM groups underwent extra-articular braking to control for abnormal tibial translation. The animals were allowed full cage activity until sacrifice postoperatively for histological and biomechanical assessment.

RESULTS

Significant differences were found in the ratios of residual ligament lengths between the CAM-MP and CAM-FS groups, demonstrating the validity of each model. Spontaneous healing of the injured ACL was observed in the CAM-MP and CAM-FS groups but not in the ACLT-MP and ACLT-FS groups. The mechanical strength of the healing ACL did not differ between the CAM-MP and CAM-FS groups 8 weeks after injury; however, the former had better mechanical strength than the latter 12 weeks after the injury.

CONCLUSION

ACL injuries in the mid-portion and on the femoral side may be treated with conservative therapy for spontaneous healing.

Influence of sidestepping expertise and core stability on knee joint loading during change of direction

The aims of this study were twofold: first, to compare core stability and knee joint loading between sidestepping experts and nonexperts; secondly, to determine core predictors of knee joint loading. Thirteen handball male players (experts) and 14 karatekas (nonexperts) performed six unanticipated 45° sidestepping manoeuvers, while trunk and pelvis 3D kinematics as well as ground reaction forces were measured, and peak knee abduction moment (PKAM) was determined. Student t-tests enabled a comparison of both groups and a linear mixed model approach was used to identify PKAM predictors. Sidestepping experts demonstrated significantly lower pelvis rotation towards the new movement direction at the initial contact than nonexperts (4.9° vs. 10.8°) and higher PKAM (0.539 vs. 0.321 Nm/kg-bwt). Trunk medial lean, trunk axial rotation and pelvis anterior tilt at the initial contact predicted PKAM, while trunk axial rotation, pelvis medial lean and posterior ground reaction force predicted PKAM during the weight acceptance phase. Despite higher PKAM, handball players might not be at a higher risk of anterior cruciate ligament injury as the knee joint loading remained at a relatively low level during this sidestepping task. Core stability, in its three dimensions, is a key determinant of knee joint loading.

Familial Predisposition to Anterior Cruciate Ligament Injury: A Systematic Review with Meta-analysis

BACKGROUND

Having a family history of anterior cruciate ligament (ACL) injury has been investigated in the literature but few studies have focused on this factor specifically or reported their outcomes by sex.

OBJECTIVE

We aimed to systematically review family history as a risk factor for sustaining a primary ACL injury and the impact it has on ACL graft rupture or contralateral ACL injury in male and female individuals.

METHODS

A literature search was completed in seven databases from inception until March 2021 to investigate primary and subsequent ACL injuries in those with a family history of ACL injury. Articles were screened by prespecified inclusion criteria, and the methodological quality of each study was determined. Study results were combined using an odds ratio (OR) meta-analysis. Subgroup analysis was also completed by sex for primary ACL injury, as well as by graft rupture and contralateral ACL injury for subsequent ACL injuries.

RESULTS

Twelve studies were acquired for systematic review and meta-analysis. Four studies that investigated primary ACL injury, seven that investigated ACL graft and/or contralateral ACL ruptures and one study that investigated both primary and subsequent ACL injury. Having a family history of ACL injury increased the odds of injury across all outcomes. Those with a family history had a 2.5 times greater odds for sustaining a primary ACL injury (OR 2.53 [95% confidence interval [CI] 1.96-3.28, p < 0.001)]. There was no significant difference of injury odds for primary ACL injury when analysed by sex. Family history of ACL injury was found to increase the odds of subsequent ACL injury by 2.38 (95% CI 1.64-3.46, p < 0.001) and was significant for both graft ruptures (OR 1.80 [95% CI 1.20-2.71, p = 0.005]) and contralateral ACL injuries (OR 2.28 [95% CI 1.28-4.04, p = 0.005]). When compared directly, the odds of sustaining a graft rupture versus a contralateral ACL injury were similar for those with a family history. Outcomes were not frequently reported by sex for subsequent ACL injuries.

CONCLUSIONS

Having a family history of ACL injury more than doubles the odds of sustaining a primary or subsequent ACL injury. However, if a family history of ACL injury is present, the sex of the athlete does not increase the risk for primary injury nor is there a difference in the risk for a subsequent graft rupture compared to a contralateral ACL injury.

CLINICAL TRIAL REGISTRATION

PROSPERO: CRD42020186472.

Vertical Drop Jump Biomechanics of Patients With a 3- to 10-Year History of Youth Sport-Related Anterior Cruciate Ligament Reconstruction

Background

A better understanding of movement biomechanics after anterior cruciate ligament reconstruction (ACLR) could inform injury prevention, knee injury rehabilitation, and osteoarthritis prevention strategies.

Purpose

To investigate differences in vertical drop jump (VDJ) biomechanics between patients with a 3- to 10-year history of youth sport-related ACLR and uninjured peers of a similar age, sex, and sport.

Study Design

Cross-sectional study. Level of evidence III.

Methods

Lower limb kinematics and bilateral ground-reaction forces (GRFs) were recorded for participants performing 10 VDJs. Joint angles and GRF data were analyzed, and statistical analysis was performed using 2 multivariate models. Dependent variables included sagittal (ankle, knee, and hip) and coronal (knee and hip) angles at initial contact and maximum knee flexion, the rate of change of coronal knee angles (35%-90% of the support phase; ie, slopes of linear regression lines), and vertical and mediolateral GRFs (normalized to body weight [BW]). Fixed effects included group, sex, and time since injury. Participant clusters, defined by sex and sport, were considered as random effects.

Results

Participants included 48 patients with a history of ACLR and 48 uninjured age-, sex-, and sport-matched controls (median age, 22 years [range, 18-26 years]; 67% female). Patients with ACLR demonstrated steeper negative coronal knee angle slopes (β = -0.04 deg/% [95% CI, -0.07 to -0.00 deg/%]; P = .025). A longer time since injury was associated with reduced knee flexion (β = -0.2° [95% CI, -0.3° to -0.0°]; P = .014) and hip flexion (β = -0.1° [95% CI, -0.2° to -0.0°]; P = .018). Regardless of ACLR history, women displayed greater knee valgus at initial contact (β = 2.1° [95% CI, 0.4° to 3.8°]; P = .017), greater coronal knee angle slopes (β = 0.05 deg/% [95% CI, 0.02 to 0.09 deg/%]; P = .004), and larger vertical GRFs (landing: β = -0.34 BW [95% CI, -0.61 to -0.07 BW]; P = .014) (pushoff: β = -0.20 BW [95% CI, -0.32 to -0.08 BW]; P = .001).

Conclusion

Women and patients with a 3- to 10-year history of ACLR demonstrated VDJ biomechanics that may be associated with knee motion control challenges.

Clinical Relevance

It is important to consider knee motion control during activities such as VDJs when developing injury prevention and rehabilitation interventions aimed at improving joint health after youth sport-related ACLR.

Second Generation of Tissue-Engineered Ligament Substitutes for Torn ACL Replacement: Adaptations for Clinical Applications

The anterior cruciate ligament (ACL) of the knee joint is one of the strongest ligaments of the body and is often the target of traumatic injuries. Unfortunately, its healing potential is limited, and the surgical options for its replacement are frequently associated with clinical issues. A bioengineered ACL (bACL) was developed using a collagen matrix, seeded with autologous cells and successfully grafted and integrated into goat knee joints. We hypothesize that, in order to reduce the cost and simplify the model, an acellular bACL can be used as a substitute for a torn ACL, and bone plugs can be replaced by endobuttons to fix the bACL in situ. First, acellular bACLs were successfully grafted in the goat model with 18% recovery of ultimate tensile strength 6 months after implantation (94 N/mm² vs. 520). Second, a bACL with endobuttons was produced and tested in an exvivo bovine knee model. The natural collagen scaffold of the bACL contributes to supporting host cell migration, growth and differentiation in situ post-implantation. Bone plugs were replaced by endobuttons to design a second generation of bACLs that offer more versatility as biocompatible grafts for torn ACL replacement in humans. A robust collagen bACL will allow solving therapeutic issues currently encountered by orthopedic surgeons such as donor-site morbidity, graft failure and post-traumatic osteoarthritis.