Mechanisms and risk factors for noncontact ACL injury in age mature athletes who engage in field or court sports: a summary of the literature since 1980

Tibiofemoral bone configuration is not associated with hamstring muscle strength in male and female patients with ACL reconstruction

PURPOSE

Previous evidence indicated that the tibiofemoral bone configuration might elevate the risk of an anterior cruciate ligament (ACL) injury. Furthermore, a low hamstring-to-quadriceps muscle ratio predisposes especially females to unfavourable knee kinematics. The primary objective of the present study was to investigate sex-specific associations between tibiofemoral bone geometry and isokinetic knee flexion torque in patients with primary ACL injury followed by ACL reconstruction.

METHODS

N = 100 patients (72 = male, 28 = female, age = 31.3 ± 10.2, body mass index = 25.3 ± 3.6) with primary ACL rupture with isokinetic knee flexion torque assessments before and 6 months after ACL reconstruction surgery were analysed. Magnetic resonance imaging scans were analysed for medial posterior tibial slope (MPTS) and lateral posterior tibial slope, notch width index (NWI) and lateral femoral condyle index (LFCI). Additionally, isokinetic knee flexion torque (60°/s) and hamstring-quadriceps ratios were evaluated. Subsequently, functional parameters were correlated with imaging data for gender subgroups.

RESULTS

The findings showed that presurgical isokinetic knee flexion torque was not associated with any marker of femoral or tibial bone geometry. Further, while significant differences were observed between female (0.883 ± 0.31 Nm/kg) and male (1.18 ± 0.35 Nm/kg) patients regarding preoperative normalized knee flexion torque (p < 0.001), no significant sex differences were found for percentage increases in normalized knee flexion torque from presurgery to postsurgery. Generally, female patients demonstrated significantly higher MPTS magnitudes (p < 0.05) and lower LFCI values (p < 0.05) compared to men.

CONCLUSION

The present results demonstrated no association between tibial or femoral bone geometry and muscle strength of the hamstrings in patients with ACL reconstruction, indicating an important mismatch of muscular compensation to deviations in bone geometry. There were no sex-specific differences in tibiofemoral bone parameters.

LEVEL OF EVIDENCE

Level III.

Analysis of the Functional Outcome of Arthroscopic Anterior Cruciate Ligament Reconstruction Using the Central Quadriceps Tendon Graft

INTRODUCTION

Anterior cruciate ligament (ACL) injuries are common, particularly among athletes, and often result in knee instability and decreased functionality. Arthroscopic ACL reconstruction is the standard treatment, typically using a patellar tendon bone graft (PTBG) or hamstring tendon graft (HTG). The central quadriceps tendon graft (QTG) has been proposed as a superior alternative due to its structural properties.

METHODOLOGY

This study involved patients undergoing ACL reconstruction using the central quadriceps tendon graft. Functional outcomes were assessed using the Tegner Lysholm knee score were assessed at preoperative and postoperative intervals of two weeks, three months, and six months. Statistical analysis compared these scores over time.

RESULTS

Among the subjects, 90.6% were male and 9.4% were female. Injuries primarily resulted from sports activities and road traffic accidents (46.9% each). Right-side injuries were more prevalent (65.6%). The mean time from injury to surgery was 9.37 months. The mean graft size was 8.75 mm, and the mean tourniquet time was 105.94 minutes. Preoperative tests showed positive results for anterior drawer, Lachman, and pivot shift tests in most patients, which were negative postoperatively. Significant improvements in knee flexion and Lysholm knee scores were observed. Preoperative knee flexion ranged from 0-100° to 0-120°, improving to 0-120° to 0-130° six months postoperatively. The mean Lysholm knee score improved from 47.06 preoperatively to 93.16 at six months. Excellent outcomes were seen in 78.1% of the patients, with 21.9% achieving good outcomes.

CONCLUSION

The central quadriceps tendon graft is an effective option for ACL reconstruction, offering excellent functional outcomes and low complication rates. It shows promise as a better alternative to traditional graft types, although further research is necessary to confirm these findings.

Dependence on visual information in patients with ACL injury for multi-joint coordination during single-leg squats: a case control study

BACKGROUND

The influence of vision on multi-joint control during dynamic tasks in anterior cruciate ligament (ACL) deficient patients is unknown. Thus, the purpose of this study was to establish a new method for quantifying neuromuscular control by focusing on the variability of multi-joint movement under conditions with different visual information and to determine the cutoff for potential biomarkers of injury risk in ACL deficient individuals.

METHODS

Twenty-three ACL deficient patients and 23 healthy subjects participated in this study. They performed single-leg squats under two different conditions: open eyes (OE) and closed eyes (CE). Multi-joint coordination was calculated with the coupling angle of hip flexion, hip abduction and knee flexion. Non-linear analyses were performed on the coupling angle. Dependence on vision was compared between groups by calculating the CE/OE index for each variable. Cutoff values were calculated using ROC curves with ACL injury as the dependent variable and significant variables as independent variables.

RESULTS

The sample entropy of the coupling angle was increased in all groups under the CE condition (P < 0.001). The CE/OE index of coupling angle variability during the descending phase was higher in ACL deficient limbs than in the limbs of healthy participants (P = 0.036). The CE/OE index of sample entropy was higher in the uninjured limbs of ACL deficient patients than in the limbs of healthy participants (P = 0.027). The cutoff value of the CE/OE index of sample entropy was calculated to be 1.477 (Sensitivity 0.957, specificity 0.478).

CONCLUSION

ACL deficient patients depended on vision to control multiple joint movements not only on the ACL deficient side but also on the uninjured side during single leg squat task. These findings underscore the importance of considering visual dependence in the assessment and rehabilitation of neuromuscular control in ACL deficient individuals.

Anatomic Factors Associated With the Development of an Anterior Cruciate Ligament Rerupture in Men: A Case-Control Study

BACKGROUND

Although several factors are associated with anterior cruciate ligament (ACL) rerupture, the effect of anatomic factors associated with ACL rupture on ACL rerupture development has not been evaluated.

PURPOSE

To determine individual anatomic parameters independently associated with ACL rerupture and the diagnostic values of these parameters.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A total of 91 male patients with ACL rerupture and 182 age-, sex-, body mass index-, and side dominance-matched patients without rerupture who underwent ACL reconstruction with a 5-year follow-up were included. In all, 35 parameters that were previously defined as risk factors for primary ACL rupture were compared between the 2 groups. Uni- and multivariate logistic regression models were created to evaluate independently associated factors. Receiver operating characteristic curve analysis was performed for independently associated parameters to predict sensitivity, specificity, and cutoff values.

RESULTS

The mean ± standard deviation age of patients at the time of index surgery was 26.5 ± 6.7 years. Notch shape index (P = .014), tibial proximal anteroposterior (AP) distance (TPAPD) (P < .001), lateral femoral condylar AP distance (LCAPD)/TPAPD ratio (P < .001), medial meniscal cartilage bone height (P < .001), and lateral meniscal bone angle (P = .004) were found to be significantly different between the 2 groups. Only the LCAPD/TPAPD ratio (odds ratio, 2.713; 95% CI, 1.998-5.480; P < .001) was found to be independently associated with ACL rerupture development. The LCAPD/TPAPD ratio revealed 78.9% sensitivity and 75.5% specificity (area under the curve, 0.815; 95% CI, 0.760-0.870) for values above 1.52.

CONCLUSION

The LCAPD/TPAPD ratio can be used to distinguish patients who are at risk of developing ACL rerupture from patients who are not. In the clinical practice, findings of this study may help to develop surgical and nonsurgical preventive strategies in ACL rerupture development.

Cutting Movement Assessment Scores during Anticipated and Unanticipated 90-Degree Sidestep Cutting Manoeuvres within Female Professional Footballers

Background: ACL injuries present a considerable burden in female football, with highest incidence being related to change of direction (COD) tasks. The aim was to identify if differences existed between an anticipated and unanticipated 90-degree cutting task using the CMAS. Methods: 11 female professional footballers completed twelve 90-degree COD tasks (6 anticipated, 6 unanticipated). Participants performed the unanticipated task in response to a moving football at the start of their acceleration. All COD tasks were filmed and assessed using the CMAS. Results: The CMAS score for the unanticipated COD task (5.53 ± 0.71) was significantly larger than for the anticipated COD task (3.55 ± 0.85, p < 0.012). Excellent intra-rater reliability was observed (ICC = 0.97) for analysis of CMAS scores. Conclusions: Female footballers in this sample demonstrated a greater CMAS score during an unanticipated COD task compared to an anticipated COD task. These athletes are therefore more likely to display ‘high-risk’ movement patterns, thus greater risk of injury. Reacting to a sporting implement, such as a moving ball, may be a contributing factor to these results. Further research into unanticipated COD tasks should be considered to determine why these differences occur and the impact of anticipation on performance.

Individual and Combined Anatomic Risk Factors for the Development of an Anterior Cruciate Ligament Rupture in Men: A Multiple Factor Analysis Case-Control Study

BACKGROUND

No comparative studies have evaluated anatomic risk factors in a large cohort including both patients with anterior cruciate ligament (ACL) ruptures and healthy participants.

PURPOSE

To determine which anatomic parameters are independently associated with an ACL rupture and the diagnostic values of the individual and combined anatomic parameters.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A total of 352 male patients who underwent arthroscopic ACL reconstruction because of a primary ACL rupture and 350 age-, sex-, body mass index-, and side dominance-matched healthy participants were included. Measurements of 32 previously determined parameters and 7 calculations were performed. Between-group differences were calculated. Univariate and multivariate logistic regression models and receiver operating characteristic curve analysis were conducted for the individual and combined independently associated factors.

RESULTS

The mean age and body mass index of all participants were 29.9 ± 7.7 years and 27.2 ± 3.1, respectively. There were significant differences between the groups regarding the notch width (NW), notch shape index, anterior tibial slope, notch width index, NW-eminence width (NW:EW) ratio, notch height, axial lateral wall angle, medial intercondylar ridge thickness, alpha angle, medial tibial depth (MTD), lateral tibial slope (LTS), coronal tibial plateau width, eminence width index, tibial proximal anteroposterior distance (TPAP), lateral condylar anteroposterior distance (LCAP)/TPAP, ACL cross-sectional area, ACL volume, medial and lateral meniscal cartilage height, medial and lateral meniscal cartilage angle (MCA), and medial and lateral meniscal cartilage bone height. The NW:EW ratio (odds ratio [OR], 4.419; P = .017), MTD (OR, 8.617; P = .001), LTS (OR, 2.254; P = .011), LCAP/TPAP (OR, 2.782; P = .037), and medial MCA (OR, 1.318; P = .010) were independently associated with the development of an ACL rupture. Combining the independently associated factors revealed a sensitivity of 93% and a specificity of 94% (area under the curve, 0.968).

CONCLUSION

Patients with ACL ruptures could be distinguished from uninjured controls with high sensitivity and specificity via the combined use of the NW:EW ratio, MTD, LTS, LCAP/TPAP, and medial MCA. In clinical practice, these findings may contribute to the development of preventive strategies for ACL ruptures.

Foot Muscle Strengthening and Lower Limb Injury Prevention

Background and objectives: The active and passive structures of the foot act in unison to not only be compliant enough to assist in ground reaction force attenuation but also resist deformation to provide a stable base of support. A foot that is unable to adjust to the imposed demands during high-intensity sporting activities may alter the moments and forces acting on the joints, increasing the risk of non-contact anterior cruciate ligament ruptures (ACLR) and lateral ankle sprains (LAS). Prophylactic strengthening programs are often used to reduce the risk of these injuries, but at present, very few prophylactic programs include foot-specific strengthening strategies. The aim of this theoretical review is to ascertain the prophylactic role strengthening muscles acting on the foot may have on ACLR and LAS injury risk. Methods: Literature relating to risk factors associated with ACLR and LAS injury and the anatomy and biomechanics of normal foot function was searched. In addition, ACLR and LAS injury prevention programs were also sought. A theoretical, narrative approach was followed to synthesize the information gathered from the articles. Results: The foot segments are governed by the congruity of the articulations and the activity of the foot muscles. As such, there is a coupling effect between shank, calcaneus, midfoot, and hallux movement which play a role in both ACLR and LAS injury risk. Conclusions: Strengthening the muscles acting on the foot may have a significant impact on ACLR and LAS injury risk.

Effects of Percutaneous Electrical Nerve Stimulation on Countermovement Jump and Squat Performance Speed in Male Soccer Players: A Pilot Randomized Clinical Trial

It has been suggested that Percutaneous Electrical Nerve Stimulation (PENS) can increase muscle strength. No previous study has investigated changes in performance in semiprofessional soccer players. This study compares the effects of adding two sessions of PENS to a training program versus the single training program over sport performance attributes (e.g., jump height and squat speed) in healthy soccer players. A cluster-randomized controlled trial was conducted on twenty-three semiprofessional soccer players who were randomized into an experimental (PENS + training program) or control (single training program) group. The training program consisted of endurance and strength exercises separated by 15-min recovery period, three times/week. The experimental group received two single sessions of PENS one-week apart. Flight time and vertical jump height during the countermovement jump and squat performance speed were assessed before and after each session, and 30 days after the last session. Male soccer players receiving the PENS intervention before the training session experienced greater increases in the flight time, and therefore, in vertical jump height, after both sessions, but not one month after than those who did not receive the PENS intervention (F = 4.289, p = 0.003, η 2 p: 0.170). Similarly, soccer players receiving the PENS intervention experienced a greater increase in the squat performance speed after the second session, but not after the first session or one month after (F = 7.947, p < 0.001, η 2 p: 0.275). Adding two sessions of ultrasound-guided PENS before a training strength program improves countermovement jump and squat performance speed in soccer players.

Hamstring Myoelectrical Activity During Three Different Kettlebell Swing Exercises

Del Monte, MJ, Opar, DA, Timmins, RG, Ross, JA, Keogh, JWL, and Lorenzen, C. Hamstring myoelectrical activity during three different kettlebell swing exercises. J Strength Cond Res 34(7): 1953-1958, 2020-Kettlebell exercises have become an increasingly popular form of resistance training and component of lower-body rehabilitative training programs, despite a lack of scientific literature illustrating internal mechanisms and effectiveness of these approaches. Participants (n = 14) performed 3 different styles of kettlebell swings (hip hinge, squat, and double knee extension) and were assessed for medial hamstrings (MHs) and biceps femoris (BF) myoelectrical activity through surface electromyography (sEMG). Bipolar pregelled Ag/AgCl sEMG electrodes (10 mm diameter, 20 mm interelectrode distance) were placed on the participant's dominant limb after correct skin preparation. There was a main effect for swing type (p = 0.004), where the hip hinge swing elicited a greater overall MH and BF sEMG in comparison with the squat swing (mean difference = 3.92; 95% confidence interval [CI] = 1.53-6.32; p = 0.002) and the double knee extension swing (mean difference = 5.32; 95% CI = 0.80-9.83; p = 0.020). Across all swing types, normalized percentage of MH sEMG was significantly higher compared with the BF (mean difference = 9.93; 95% CI = 1.67-18.19; p = 0.022). The hip hinge kettlebell swing produced the greatest amount of hamstring sEMG for the 3 styles of kettlebell swings assessed. These findings have implications for the application of kettlebell swing exercises in strength and conditioning, injury prevention, and rehabilitation programs.

Rate of Force Development Remains Reduced in the Knee Flexors 3 to 9 Months After Anterior Cruciate Ligament Reconstruction Using Medial Hamstring Autografts: A Cross-Sectional Study

BACKGROUND

Anterior cruciate ligament (ACL) rupture is a serious injury with a high prevalence worldwide, and subsequent ACL reconstructions (ACLR) appear to be most commonly performed using hamstring-derived (semitendinosus tendon) autografts. Recovery of maximal muscle strength to ≥90% of the healthy contralateral limb is considered an important criterion for safe return to sports. However, the speed of developing muscular force (ie, the rate of force development [RFD]) is also important for the performance of many types of activities in sports and daily living, yet RFD of the knee extensor and flexor muscles has apparently never been examined in patients who undergo ACLR with hamstring autograft (HA).

PURPOSE

To examine potential deficits in RFD, maximal muscle strength (ie, maximal voluntary isometric contraction [MVIC]), and functional capacity of ACLR-HA limbs in comparison with the healthy contralateral leg and matched healthy controls 3 to 9 months after surgery.

STUDY DESIGN

Cross-sectional study; Level of evidence: 3.

METHODS

A total of 23 young patients who had undergone ACLR-HA 3 to 9 months earlier were matched by age to 14 healthy controls; both groups underwent neuromuscular screening. Knee extensor and flexor MVIC and RFD, as well as functional capacity (single-leg hop for distance [SLHD] test, timed single-leg sit-to-stand [STS] test), were assessed on both limbs. Furthermore, patient-reported knee function (Knee injury and Osteoarthritis Outcome Score) was assessed.

RESULTS

Knee extensor and flexor MVIC and RFD were markedly compromised in ACLR-HA limbs compared with healthy contralateral limbs (MVIC for extensor and flexor, 13% and 26%, respectively; RFD, 14%-17% and 32%-39%) and controls (MVIC, 16% and 31%; RFD, 14%-19% and 30%-41%) (P < .05-.001). Further, ACLR-HA limbs showed reduced functional capacity (reduced SLHD and STS performance) compared with contralateral limbs (SLHD, 11%; STS, 14%) and controls (SLHD, 20%; STS, 31%) (P < .01-.001). Strength (MVIC) and functional (SLHD) parameters were positively related to the duration of time after surgery (P < .05), although this relationship was not observed for RFD and STS.

CONCLUSION

Knee extensor and flexor RFD and maximal strength, as well as functional single-leg performance, remained substantially reduced in ACLR-HA limbs compared with noninjured contralateral limbs and healthy controls 3 to 9 months after reconstructive surgery.

Epidemiological Trends of Anterior Cruciate Ligament Reconstruction in a Canadian Province

OBJECTIVE

To determine epidemiological trends of anterior cruciate ligament reconstruction (ACL-R) in a Canadian province, estimate the national incidence, and compare with internationally published data.

DESIGN

Retrospective review.

SETTING

All hospitals that performed ACL reconstructions in Manitoba between 1980 and 2015.

PARTICIPANT

All patients that underwent ACL-R in Manitoba between 1980 and 2015.

INTERVENTION

This is a retrospective review looking at deidentified, individual-level administrative records of health services used for the entire population of Manitoba (approximately 1.3 million). Codes for ACL and cruciate ligament reconstruction were searched from 1980 to 2015. Patient demographics included age, sex, geographic area of residence, and neighborhood income quintile.

MAIN OUTCOME MEASURES

Trends of ACL reconstructions from 1980 to 2015.

RESULTS

A total of 10 114 ACL-R were performed during the 36-year study period and patients were predominantly male (63.1%). The mean age at ACL-R was 29.5 years (SD 10.0) for males and 28.5 years (SD 11.9) for females, whereas age younger than 40 years accounted for 81.7% of all ACL-R. The incidence of ACL-R increased from 7.56/100 000 inhabitants in 1980 to 48.45/100 000 in 2015. The proportion of females undergoing ACL-R has increased from 29.3% in 1980% to 41.9% in 2015, and female patients now comprise the majority of ACL-R in the under-20 age category.

CONCLUSION

The incidence of ACL-R has significantly increased since 1980; female patients now make up a greater proportion than males of the ACL-R population younger than 20 years. This information can be used to guide resource allocation planning and focus injury prevention initiatives.

The relationship between physical fitness attributes and sports injury in female, team ball sport players: a systematic review

BACKGROUND

Understanding the relationships between physical fitness characteristics and sports injury may assist with the development of injury minimisation programs. The purpose of this systematic review was to investigate the association between physical fitness attributes and sports injury in female, team ball sport players.

METHODS

Four scientific databases (MEDLINE, EMBASE, SPORTDiscus, Scopus) and reference lists of relevant research were searched for eligible studies up to September 2, 2019. Full-text articles examining the relationship between physical fitness and sports injury in female, team ball sport players were included. A modified Downs and Black checklist was used to assess methodological quality. Data synthesis determined summary conclusions based on the number of significant relationships divided by the total relationships investigated and reported as a percentage. Level of certainty was identified for summary conclusions based on level of evidence. Sub-analyses regarding competition level, age, and single injury types were also conducted.

RESULTS

A total of 44 studies were included. Data synthesis revealed no associations (low to moderate certainty) between body composition (1/9; 11%), flexibility (18-20%), and balance (2/8; 25%) and 'any injury' classification. No associations (mostly of moderate certainty) were found between flexibility (0-27%), muscular strength (0-27%), and body composition (14-33%) and various body region injury classifications, whereas mixed summary conclusions were shown for balance (0-48%). Many associations between physical fitness and sports injury were deemed 'unknown' or with an insufficient level of certainty. Sub-analyses revealed no association between strength and noncontact ACL injuries (0/5; 0%) or ankle sprains (0/12; 0%), and between flexibility and ankle sprains (1/5; 20%); however, insufficient certainty of these results exists. Clear associations were concluded between balance and lower body injuries in female, non-elite (10/16; 63%) and junior (9/12; 75%) team ball sport players, with moderate and insufficient certainty of these results, respectively.

CONCLUSION

Limited evidence is available to demonstrate relationships between physical fitness and sports injury in female, team ball sport players. High-quality evidence investigating the multifactorial nature of sports injury, including the interactions physical fitness qualities have with other injury determinants, is needed to better understand the role of physical fitness in minimising sports injuries in female, team ball sport players.

TRIAL REGISTRATION

CRD42017077374 (PROSPERO on September 14, 2017).

Variations in internal structure, composition and protein distribution between intra- and extra-articular knee ligaments and tendons

Tendons and ligaments play key roles in the musculoskeletal system in both man and animals. Both tissues can undergo traumatic injury, age‐related degeneration and chronic disease, causing discomfort, pain and increased susceptibility to wider degenerative joint disease. To date, tendon and ligament ultrastructural biology is relatively under‐studied in healthy, non‐diseased tissues. This information is essential to understand the pathology of these tissues with regard to function‐related injury and to assist with the future development of tissue‐engineered tendon and ligament structures. This study investigated the morphological, compositional and extracellular matrix protein distribution differences between tendons and ligaments around the non‐diseased canine stifle joint. The morphological, structural characteristics of different regions of the periarticular tendons and ligaments (the intra‐articular anterior cruciate ligament, the extra‐articular medial collateral ligament, the positional long digital extensor tendon and energy‐storing superficial digital flexor tendons) were identified using a novel semi‐objective histological scoring analysis and by determining their biochemical composition. Protein distribution of extracellular matrix collagens, proteoglycans and elastic fibre proteins in anterior cruciate ligament and long digital extensor tendon were also determined using immunostaining techniques. The anterior cruciate ligament was found to have significant morphological differences in comparison with the other three tissues, including less compact collagen architecture, differences in cell nuclei phenotype and increased glycosaminoglycan and elastin content. Intra‐ and interobserver differences of histology scoring resulted in an average score 0.7, indicative of good agreement between observers. Statistically significant differences were also found in the extracellular matrix composition in terms of glycosaminoglycan and elastin content, being more prominent in the anterior cruciate ligament than in the other three tissues. A different distribution of several extracellular matrix proteins was also found between long digital extensor tendon and anterior cruciate ligament, with a significantly increased immunostaining of aggrecan and versican in the anterior cruciate ligament. These findings directly relate to the different functions of tendon and ligament and indicate that the intra‐articular anterior cruciate ligament is subjected to more compressive forces, reflecting an adaptive response to normal or increased loads and resulting in different extracellular matrix composition and arrangement to protect the tissue from damage.

Preventive Biomechanics: A Paradigm Shift With a Translational Approach to Injury Prevention

BACKGROUND

Preventive medicine techniques have alleviated billions of dollars' worth of the economic burden in the medical care system through the implementation of vaccinations and screenings before the onset of disease symptoms. Knowledge of biomechanical tendencies has progressed rapidly over the past 20 years such that clinicians can identify, in healthy athletes, the underlying mechanisms that lead to catastrophic injuries such as anterior cruciate ligament (ACL) ruptures. As such, preventive medicine concepts can be applied to noncontact musculoskeletal injuries to reduce the economic burden of sports medicine treatments and enhance the long-term health of athletes.

PURPOSE

To illustrate the practical medical benefits that could be gained from preventive biomechanics applied to the ACL as well as the need and feasibility for the broad implementation of these principles.

STUDY DESIGN

Literature review.

METHODS

The recent literature pertinent to the screening and prevention of musculoskeletal injuries was reviewed and compiled into a clinical commentary on the current state and applicability of preventive biomechanics.

RESULTS

Investigators have identified neuromuscular training protocols that screen for and correct the underlying biomechanical deficits that lead to ACL injuries. The literature shows that when athletes comply with these prescribed training protocols, the incidence of injuries is significantly reduced within that population. Such preventive biomechanics practices employ basic training methods that would be familiar to athletic coaches and have the potential to save billions of dollars in cost in sports medicine.

CONCLUSION

The widespread implementation of preventive biomechanics concepts could profoundly affect the field of sports medicine with a minimum of initial investment.

Mechanisms of ACL injury in professional rugby union: a systematic video analysis of 36 cases

Background

The mechanisms of ACL injury in rugby are not well defined.

Aim

To describe the mechanisms of ACL injury in male professional rugby players using systematic video analysis.

Methods

36 cases from games played in top professional leagues and international matches were analysed. 5 analysts independently assessed all videos to record the estimated frame/time of initial ground contact, frame/time of ACL tear and a range of play specific variables. This included contact versus non-contact ACL injuries, injury timing, joint flexion angles and foot contact with the ground. 37 side-stepping manoeuvres from a control game were analysed to allow comparison of non-injury versus injury situations.

Results

57% of ACL injuries occurred in a contact manner. 2 main scenarios were identified: (1) offensive running and (2) being tackled, indicating that the ball carrier might be at higher risk of ACL injury. The majority of non-contact ACL injuries resulted from a side-stepping manoeuvre. In most non-contact cases, initial ground contact was through heel strike. Statistical assessment of heel strike at initial ground contact versus non-heel strike cases showed a significant difference in injury versus non-injury outcomes, with heel strike associated with higher injury risk. Non-contact ACL injuries had lower median knee flexion angles and a more dorsiflexed ankle when compared with a control group (10° vs 20°, p≤0.001 and 10° vs 0°, p=0.033 respectively).

Conclusions

Over half of ACL injuries in rugby in our analysis resulted from a contact mechanism. For non-contact injuries, lower knee flexion angles and heel-first ground contact in a side-stepping manoeuvre were associated with ACL injury.

An Ecological Study of Anterior Cruciate Ligament Reconstruction, Part 1: Clinical Tests Do Not Correlate With Return-to-Sport Outcomes

BACKGROUND

Additional high-quality prospective studies are needed to better define the objective criteria used in relation to return-to-sport decisions after synthetic (ligament advanced reinforcement system [LARS]) and autograft (hamstring tendon [2ST/2GR]) anterior cruciate ligament (ACL) reconstruction in active populations.

PURPOSE

To prospectively investigate and describe the recovery of objective clinical outcomes after autograft (2ST/2GR) and synthetic (LARS) ACL reconstructions, as well as to investigate the relationship between these clinimetric test outcomes and return-to-sport activity (Tegner activity scale [TAS] score) at 12 and 24 months postoperatively.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 64 patients who underwent ACL reconstruction (32 LARS, 32 2ST/2GR autograft) and 32 healthy reference participants were assessed for joint laxity (KT-1000 arthrometer), clinical outcome (2000 International Knee Documentation Committee [IKDC] knee examination), and activity (TAS score) preoperatively and at 12, 16, 20, and 24 weeks and 12 and 24 months postoperatively.

RESULTS

There was no significant correlation observed between clinical results using the 2000 IKDC knee examination and TAS score at 24 months (r_s = 0.188, P = .137), nor were results for side-to-side difference (r_s = 0.030, P = .814) or absolute KT-1000 arthrometer laxity of the surgical leg at 24 months postoperatively (r_s = 0.076, P = .553) correlated with return-to-sport activity. Nonetheless, return-to-sport rates within the surgical cohort were 81% at 12 months and 83% at 24 months, respectively. No statistically significant differences were observed between physiological laxity of the uninjured knee within the surgical group compared with healthy knees within the reference group (P = .522).

CONCLUSION

The results indicate that although relatively high levels of return-to-sport outcomes were achieved at 24 months compared with those previously reported in the literature, correlations between objective clinical tests and return-to-sport outcomes may not occur. Clinical outcome measures may provide suitable baseline information; however, the results of this study suggest that clinicians may need to place greater emphasis on other outcome measures when seeking to objectively promote safe return to sport.

Vertical stiffness is not related to anterior cruciate ligament elongation in professional rugby union players

Background

Novel research surrounding anterior cruciate ligament (ACL) injury is necessary because ACL injury rates have remained unchanged for several decades. An area of ACL risk mitigation which has not been well researched relates to vertical stiffness. The relationship between increased vertical stiffness and increased ground reaction force suggests that vertical stiffness may be related to ACL injury risk. However, given that increased dynamic knee joint stability has been shown to be associated with vertical stiffness, it is possible that modification of vertical stiffness could help to protect against injury. We aimed to determine whether vertical stiffness is related to measures known to load, or which represent loading of, the ACL.

Methods

This was a cross-sectional observational study of 11 professional Australian rugby players. Knee kinematics and ACL elongation were measured from a 4-dimensional model of a hopping task which simulated the change of direction manoeuvre typically observed when non-contact ACL injury occurs. The model was generated from a CT scan of the participant's knee registered frame by frame to fluoroscopy images of the hopping task. Vertical stiffness was calculated from force plate data.

Results

There was no association found between vertical stiffness and anterior tibial translation (ATT) or ACL elongation (r=−0.05; p=0.89, and r=−0.07; p=0.83, respectively). ATT was related to ACL elongation (r=0.93; p=0.0001).

Conclusions

Vertical stiffness was not associated with ACL loading in this cohort of elite rugby players but a novel method for measuring ACL elongation in vivo was found to have good construct validity.

A Systematic Summary of Systematic Reviews on the Topic of the Anterior Cruciate Ligament

BACKGROUND

There has been a substantial increase in the amount of systematic reviews and meta-analyses published on the anterior cruciate ligament (ACL).

PURPOSE

To quantify the number of systematic reviews and meta-analyses published on the ACL in the past decade and to provide an overall summary of this literature.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A systematic review of all ACL-related systematic reviews and meta-analyses published between January 2004 and September 2014 was performed using PubMed, MEDLINE, and the Cochrane Database. Narrative reviews and non-English articles were excluded.

RESULTS

A total of 1031 articles were found, of which 240 met the inclusion criteria. Included articles were summarized and divided into 17 topics: anatomy, epidemiology, prevention, associated injuries, diagnosis, operative versus nonoperative management, graft choice, surgical technique, fixation methods, computer-assisted surgery, platelet-rich plasma, rehabilitation, return to play, outcomes assessment, arthritis, complications, and miscellaneous.

CONCLUSION

A summary of systematic reviews on the ACL can supply the surgeon with a single source for the most up-to-date synthesis of the literature.

Analyses of Landing Mechanics in Division I Athletes Using the Landing Error Scoring System

BACKGROUND

Injury to the anterior cruciate ligament (ACL) can be detrimental to any athlete, having both short- and long-term health consequences. Examining preseason screening landing mechanics can indicate the likelihood of injury during the season. Furthermore, previous injury is also commonly referred as a predisposing factor for reinjury.

HYPOTHESIS

Players with a history of lower extremity injury would have higher Landing Error Scoring System (LESS) scores than those with no previous injury, and healthy soccer athletes who sustained an injury during the 2014 season would have higher LESS scores than those who remained uninjured.

STUDY DESIGN

Prospective cohort study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Thirty-four Division I male and female soccer athletes (19 men, 15 women; mean age, 19.6 ± 1.2 years; mean height, 172.4 ± 8.7 cm; mean weight, 70.8 ± 9.1 kg). An a priori sample size estimation for a power of 0.80 (80%) and an alpha error of 0.05 with an estimated effect size of 0.6 for a sample of 30 participants was attained. Participants performed a drop-landing task and were scored on their landing mechanics using the LESS. Lower extremity injuries were tracked during the season. LESS scores between those with and without a history of injury and those who were injured and uninjured during the season were compared using 2 separate 1-way analyses of variance.

RESULTS

No statistically significant differences (F(1,33) = 0.47, P = 0.50) existed between LESS scores in athletes who had a previous injury history compared with those with no injury history. No statistically significant differences (F(1,20) = 0.05, P = 0.83) existed between LESS scores in healthy athletes who were injured during the 2014 season compared with those healthy athletes who were uninjured.

CONCLUSION

No differences were present between athletes with and without a history of lower extremity injury. The majority of healthy participants who were injured during the season had similar LESS scores to those who remained uninjured, suggesting that the LESS may not be able to identify atypical landing mechanics in this group of athletes.

Biomechanical and neuromuscular characteristics of male athletes: implications for the development of anterior cruciate ligament injury prevention programs

Prevention of anterior cruciate ligament (ACL) injury is likely the most effective strategy to reduce undesired health consequences including reconstruction surgery, long-term rehabilitation, and pre-mature osteoarthritis occurrence. A thorough understanding of mechanisms and risk factors of ACL injury is crucial to develop effective prevention programs, especially for biomechanical and neuromuscular modifiable risk factors. Historically, the available evidence regarding ACL risk factors has mainly involved female athletes or has compared male and female athletes without an intra-group comparison for male athletes. Therefore, the principal purpose of this article was to review existing evidence regarding the investigation of biomechanical and neuromuscular characteristics that may imply aberrant knee kinematics and kinetics that would place the male athlete at risk of ACL injury. Biomechanical evidence related to knee kinematics and kinetics was reviewed by different planes (sagittal and frontal/coronal), tasks (single-leg landing and cutting), situation (anticipated and unanticipated), foot positioning, playing surface, and fatigued status. Neuromuscular evidence potentially related to ACL injury was reviewed. Recommendations for prevention programs for ACL injuries in male athletes were developed based on the synthesis of the biomechanical and neuromuscular characteristics. The recommendations suggest performing exercises with multi-plane biomechanical components including single-leg maneuvers in dynamic movements, reaction to and decision making in unexpected situations, appropriate foot positioning, and consideration of playing surface condition, as well as enhancing neuromuscular aspects such as fatigue, proprioception, muscle activation, and inter-joint coordination.

Mechanisms of anterior cruciate ligament injuries in elite women's netball: a systematic video analysis

This study involved a systematic video analysis of 16 anterior cruciate ligament (ACL) injuries sustained by elite-level netball players during televised games in order to describe the game situation, the movement patterns involved, the player's behaviour, and a potential injury mechanism. Eight of the ACL injuries were classified as "indirect contact" and eight as "non-contact". Two common scenarios were identified. In Scenario A the player was jumping to receive or intercept a pass and whilst competing for the ball experienced a perturbation in the air. As a result the player's landing was unbalanced with loading occurring predominantly on the knee of the injured side. In Scenario B the player was generally in a good position at ground contact, but then noticeably altered the alignment of the trunk before the landing was completed. This involved rotating and laterally flexing the trunk without altering the alignment of the feet. Apparent knee valgus collapse on the knee of the injured side was observed in 3/6 Scenario A cases and 5/6 Scenario B cases. Players may benefit from landing training programmes that incorporate tasks that use a ball and include decision-making components or require players to learn to cope with being unbalanced.

Medial and lateral hamstrings and quadriceps co-activation affects knee joint kinematics and ACL elongation: a pilot study

Background

Many injury prevention and rehabilitation programs aim to train hamstring and quadriceps co-activation to constrain excessive anterior tibial translation and protect the anterior cruciate ligament (ACL) from injury. However, despite strong clinical belief in its efficacy, primary evidence supporting training co-activation of the hamstrings and quadriceps muscles for ACL injury prevention and rehabilitation is quite limited. Therefore, the purpose of the study presented in this paper was to determine if hamstring-quadriceps co-activation alters knee joint kinematics, and also establish if it affects ACL elongation.

Methods

A computed tomography (CT) scan from each participant’s dominant leg was acquired prior to performing two step-ups under fluoroscopy: one with ‘natural’ hamstring-quadriceps co-activation, one with deliberate co-activation. Electromyography was used to confirm increased motor unit recruitment. The CT scan was registered to fluoroscopy for 4-D modeling, and knee joint kinematics subsequently measured. Anterior cruciate ligament attachments were mapped to the 4-D models and its length was assumed from the distance between attachments. Anterior cruciate ligament elongation was derived from the change in distance between those points as they moved relative to each other.

Results

Reduced ACL elongation as well as knee joint rotation, abduction, translation, and distraction was observed for the step up with increased co-activation. A relationship was shown to exist for change in ACL length with knee abduction (r = 0.91; p ≤ 0.001), with distraction (r = −0.70; p = 0.02 for relationship with compression), and with anterior tibial translation (r = 0.52; p = 0.01). However, ACL elongation was not associated with internal rotation or medial translation. Medial hamstring-quadriceps co-activation was associated with a shorter ACL (r = −0.71; p = 0.01), and lateral hamstring-quadriceps co-activation was related to ACL elongation (r = 0.46; p = 0.05).

Conclusion

Net co-activation of the hamstrings and quadriceps muscles will likely reduce ACL elongation provided that the proportion of medial hamstring-quadriceps co-activation exceeds lateral.

Assessment of gastrocnemius tensiomyographic neuromuscular characteristics as risk factors for anterior cruciate ligament injury in male soccer players

PURPOSE

There is a large number of publications evaluating neuromuscular risk factors for anterior cruciate ligament (ACL) injury in athletes. However, most of them have involved the female athlete and, in addition, the gastrocnemius muscles have been less investigated by far compared with the quadriceps and hamstring. The purpose of this study was to investigate the role of the gastrocnemius muscles as neuromuscular risk factors for ACL injury in male soccer players, through tensiomyography (TMG).

METHODS

All competitive male soccer players with confirmed ACL tear included in this study underwent resting TMG assessment of gastrocnemius medialis (GM) and gastrocnemius lateralis muscles of the uninjured side. The same values were obtained from a sex-, and sports level-matched control group in both sides. The maximal displacement (D m), delay time (T d), contraction time (T c), sustained time (T s), and half-relaxation time (T r) were obtained for both muscles. TMG values of the uninjured side in ACL-injured group were compared with the mean values between both sides in the control subjects.

RESULTS

There were no significant between-group differences in demographic characteristics. Most TMG parameters of the gastrocnemius muscles were not significantly different between the two groups. Only the GM-T r (p = 0.02) and GM-D m (p = 0.006) were significantly higher in the ACL-injured group compared with control group.

CONCLUSIONS

Neuromuscular characteristics in terms of mechanical and contractile properties of the gastrocnemius muscles may not be significant risk factors for ACL injury in male soccer players.

Assessment of neuromuscular risk factors for anterior cruciate ligament injury through tensiomyography in male soccer players

PURPOSE

To investigate the role of mechanical and contractile properties of skeletal muscles of the thigh, assessed through tensiomyography (TMG), as risk factors for anterior cruciate ligament (ACL) injury in male soccer players.

METHODS

Male soccer players with confirmed ACL tear included in this study underwent resting TMG assessment of thigh muscles of the uninjured side. The same values were obtained from a sex-, sports level-matched control group in both sides. The maximal displacement (Dm), delay time (Td), contraction time (Tc), sustained time (Ts), and half-relaxation time (Tr) were obtained for the following muscles in all subjects: vastus medialis (VM), vastus laterals (VL), rectus femoris (RF), semitendinosus (ST), and biceps femoris (BF). TMG values of the uninjured side in ACL-injured group were compared to mean values between both sides in the control subjects.

RESULTS

There were 40 ACL-injured and 38 control individuals. The vast majority of TMG parameters were higher in the uninjured side of ACL-injured individuals compared to the control group. The VL-Tr, RF-Tc, RF-Ts, RF-Tr, and BF-Dm values were significantly higher in the uninjured side compared to the control group. Quadriceps muscles demonstrated more significant between-group differences than hamstring muscles. Specifically, RF was the muscle where most significant between-group differences were found.

CONCLUSIONS

Resistance to fatigue and muscle stiffness in the hamstring muscles may be risk factors for ACL injury in male soccer players. In addition, a predominant impairment in TMG characteristics of the quadriceps over hamstrings may indicate an altered muscular co-contraction (imbalance) between both muscle groups, which might be another risk factor for ACL injury in this population. These findings should be taken into account when screening athletes at high risk of ACL injury and also to design adequate prevention programs for ACL injury in male soccer players.

Hamstrings strength imbalance in professional football (soccer) players in Australia

The aim of this study was to describe the isokinetic thigh muscle strength profile of professional male football players in Australia. Concentric (60° and 240°·s(-1)) and eccentric (30° and 120°·s(-1)) hamstrings and quadriceps isokinetic strength was measured with a HUMAC NORM dynamometer. The primary variables were bilateral concentric and eccentric hamstring and quadriceps peak torque ratios, concentric hamstring-quadriceps peak torque ratios, and mixed ratios (eccentric hamstring 30°·s(-1) ÷ concentric quadriceps 240°·s(-1)). Hamstring strength imbalance was defined as deficits in any 2 of: bilateral concentric hamstring peak torque ratio <0.86, bilateral eccentric hamstring peak torque ratio <0.86, concentric hamstring-quadriceps ratio <0.47, and mixed ratio <0.80. Fifty-five strength tests involving 42 players were conducted. Ten players (24%) were identified as having hamstring strength imbalance. Athletes with strength imbalance had significantly reduced concentric and eccentric bilateral hamstring peak torque ratios at all angular velocities tested; and reduced eccentric quadriceps peak torque (30°·s(-1)) in their stance leg, compared with those without strength imbalance. Approximately, 1 in 4 players had preseason hamstring strength imbalance; and all strength deficits were observed in the stance leg. Concentric and eccentric hamstrings strength imbalance may impact in-season football performance and could have implications for the future risk of injury.

Elastin content is high in the canine cruciate ligament and is associated with degeneration

Cruciate ligaments (CLs) are primary stabilisers of the knee joint and canine cranial cruciate ligament disease (CCLD) and rupture is a common injury. Elastin fibres, composed of an elastin core and fibrillin containing microfibrils, are traditionally considered minor components of the ligament extracellular matrix (ECM). However, their content and distribution in CLs is unknown. The purposes of this study were to determine the elastin content of canine CLs and to ascertain its relationship to other biochemical components and histological architecture. Macroscopically normal CLs were harvested from Greyhounds (n=11), a breed with a low risk of CCLD. Elastin, collagen and sulfated glycosaminoglycan content were measured and histological scoring systems were developed to quantify ECM changes using a modified Vasseur score (mVS) and oxytalan fibre (bundles of microfibrils) staining. Elastin contents were 9.86 ± 3.97% dry weight in the cranial CL and 10.79 ± 4.37% in the caudal CL, respectively, and did not alter with advancing histological degeneration. All CLs demonstrated mild degenerative changes, with an average mVS score of 11.9 ± 3.3 (maximum 24). Increasing degeneration of the ligament ECM showed a positive correlation (r=0.690, P<0.001) with increased oxytalan fibre staining within the ECM. Elastin is an abundant protein in CLs forming a greater proportion of the ligament ECM than previously reported. The appearance of oxytalan fibres in degenerative CL ECM may reflect an adaptive or reparative response to normal or increased loads. This finding is important for future therapeutic or ligament replacement strategies associated with cranial CL injury.