Geometric profile of the tibial plateau cartilage surface is associated with the risk of non-contact anterior cruciate ligament injury

Statistical shape analysis and computational modeling reveal novel relationships between tibiofemoral bony geometry and knee mechanics in young, female athletes

Young female athletes participating in sports requiring rapid changes of direction are at heightened risk of suffering traumatic knee injury, especially noncontact rupture of the anterior cruciate ligament (ACL). Clinical studies have revealed that geometric features of the tibiofemoral joint are associated with increased risk of suffering noncontact ACL injury. However, the relationship between three-dimensional (3D) tibiofemoral geometry and knee mechanics in young female athletes is not well understood. We developed a statistically augmented computational modeling workflow to determine relationships between 3D geometry of the knee and tibiofemoral kinematics and ACL force in response to an applied loading sequence of compression, valgus, and anterior force, which is known to load the ACL. This workflow included 3D characterization of tibiofemoral bony geometry via principal component analysis and multibody dynamics models incorporating subject-specific knee geometries. A combination of geometric features of both the tibia and the femur that spanned all three anatomical planes was related to increased ACL force and to increased kinematic coupling (i.e., anterior, medial, and distal tibial translations and internal tibial rotation) in response to the applied loads. In contrast, a uniplanar measure of tibiofemoral geometry that is associated with ACL injury risk, sagittal plane slope of the lateral tibial plateau subchondral bone, was not related to ACL force. Thus, our workflow may aid in developing mechanics-based ACL injury screening tools for young, active females based on a unique combination of bony geometric features that are related to increased ACL loading.

Association Between Posterior Tibial Slope and ACL Injury in Pediatric Patients: A Systematic Review and Meta-analysis

BACKGROUND

The posterior tibial slope (PTS) has been proposed to be a radiographic risk factor for anterior cruciate ligament (ACL) injury in adults. However, this has not been well established in pediatric patients.

PURPOSE

This systematic review and meta-analysis was performed to investigate any association between PTS and ACL tears in the pediatric population.

STUDY DESIGN

Systematic review and meta-analysis; Level of evidence, 4.

METHODS

A systematic review was performed to identify studies that examined the relationship between PTS, medial tibial slope (MTS), and lateral tibial slope (LTS) and ACL tears in children and adolescents aged ≤18 years. Full-text observational studies comparing PTS, MTS, and/or LTS values between pediatric (≤18 years of age) patients with and without ACL injury were included in this analysis. Review articles and case series were excluded. The authors calculated the mean difference (MD) via a restricted maximum-likelihood estimator for tau square and a Hartung-Knapp adjustment for random-effects model.

RESULTS

A total of 348 articles were identified in the initial database search, yielding 10 for final inclusion and analysis. There was no statistically significant association between PTS (MD, 1.13°; 95% CI, -0.55° to 2.80°; P = .10), MTS (MD, 0.36°; 95% CI, -0.37° to 1.10°; P = .27), or LTS (MD, 1.41°; 95% CI, -0.20° to 3.02°; P = .075) and risk for ACL injury in this population.

CONCLUSION

The current study found that unlike what has been shown in adult populations, increased PTS may not be a significant risk factor for ACL tears in pediatric and adolescent patents. LTS was the only measured parameter that neared statistical significance, perhaps suggesting a potential role for this measurement in determining ACL risk if further research is done in this population.

Risk Factors for Concomitant Meniscal Injury With Sport-Related Anterior Cruciate Ligament Injury

Background

Previous studies of concomitant meniscal injury in athletes with anterior cruciate ligament (ACL) injury have examined age, sex, body mass index (BMI), injury mechanism, and time from injury to surgery as potential risk factors.

Purpose

To identify additional risk factors for concomitant meniscal injury, including preinjury joint laxity and lower extremity alignment, in athletes with sport-related ACL injury.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

This study included 180 participants aged 13 to 26 years who underwent ACL reconstruction (ACLR) after a first-time ACL injury sustained during participation in sport. Contralateral lower extremity alignment and joint laxity were used as surrogate measures for the injured knee before trauma. Concomitant meniscal tear patterns were identified at the time of ACLR. Sex-specific analyses were conducted.

Results

Concomitant meniscal injury was observed in 60.6% of the subjects. The prevalence of concomitant injury was higher in male than female participants (69.9% vs 54.2%; P = .035) due to a higher prevalence of lateral meniscal injuries (56.2% vs 38.3%; P = .018). Among male patients, there was a significant difference in the prevalence of concomitant lateral meniscal tear according to sport participation (≥9 vs <9 h/week: 67.4% vs 35.7%; P = .032). Among male patients, the likelihood of concomitant injury to both the lateral and medial menisci increased by 28.8% for each 1-mm decrease in navicular drop. Among female patients, the likelihood of concomitant injury to the lateral meniscus increased by 15% per degree increase in genu recurvatum and 14% per degree decrease in standing quadriceps angle, with similar effects on the likelihood of concurrent injury to both the lateral and medial menisci.

Conclusion

Measures of lower extremity alignment and genu recurvatum previously identified as risk factors for ACL injury were also associated with concomitant meniscal injury in female patients while other risk factors, including BMI and joint laxity, were not. Increased time spent participating in sport and navicular drop were associated with concomitant meniscal injury in male patients.

Key Thresholds and Relative Contributions of Knee Geometry, Anteroposterior Laxity, and Body Weight as Risk Factors for Noncontact ACL Injury

Background

Limited data exist regarding the association of tibiofemoral bony and soft tissue geometry and knee laxity with risk of first-time noncontact anterior cruciate ligament (ACL) rupture.

Purpose

To determine associations of tibiofemoral geometry and anteroposterior (AP) knee laxity with risk of first-time noncontact ACL injury in high school and collegiate athletes.

Study Design

Cohort study; Level of evidence, 2.

Methods

Over a 4-year period, noncontact ACL injury events were identified as they occurred in 86 high school and collegiate athletes (59 female, 27 male). Sex- and age-matched control participants were selected from the same team. AP laxity of the uninjured knee was measured using a KT-2000 arthrometer. Magnetic resonance imaging was taken on ipsilateral and contralateral knees, and articular geometries were measured. Sex-specific general additive models were implemented to investigate associations between injury risk and 6 features: ACL volume, meniscus-bone wedge angle in the lateral compartment of the tibia, articular cartilage slope at the middle region of the lateral compartment of the tibia, femoral notch width at the anterior outlet, body weight, and AP displacement of the tibia relative to the femur. Importance scores (in percentages) were calculated to rank the relative contribution of each variable.

Results

In the female cohort, the 2 features with the highest importance scores were tibial cartilage slope (8.6%) and notch width (8.1%). In the male cohort, the 2 top-ranked features were AP laxity (5.6%) and tibial cartilage slope (4.8%). In female patients, injury risk increased by 25.5% with lateral middle cartilage slope becoming more posteroinferior from -6.2° to -2.0° and by 17.5% with lateral meniscus-bone wedge angle increasing from 27.3° to 28.2°. In males, an increase in AP displacement from 12.5 to 14.4 mm in response to a 133-N anterior-directed load was associated with a 16.7% increase in risk.

Conclusion

Of the 6 variables studied, there was no single dominant geometric or laxity risk factor for ACL injury in either the female or male cohort. In males, AP laxity >13 to 14 mm was associated with sharply increased risk of noncontact ACL injury. In females, lateral meniscus-bone wedge angle >28° was associated with a sharply decreased risk of noncontact ACL injury.

Intrinsic Risk Factors for First-Time Noncontact ACL Injury: A Prospective Study of College and High School Athletes

BACKGROUND

A comprehensive understanding of the intrinsic risk factors for anterior cruciate ligament (ACL) disruption is important for identifying individuals at increased risk for suffering this trauma and developing interventions to mitigate risk.

HYPOTHESIS

A variety of risk factors predispose athletes to first-time, noncontact ACL injury and some of these differ between male and female athletes.

STUDY DESIGN

Prospective cohort study with nested case-control sampling.

LEVEL OF EVIDENCE

Level 2.

METHODS

Sport teams at 28 high schools and 8 colleges were monitored prospectively over 4 years, and 109 of 130 athletes who suffered their first noncontact ACL injury participated in the study. At the time of injury, matched control subjects were randomly selected from among the case's teammates and a total of 227 athletes participated. Demographic characteristics, joint laxity, lower extremity alignment, strength, and personality characteristics were measured. The association of each risk factor with injury risk was assessed by conditional logistic regression.

RESULTS

The risk factors that were associated with ACL injury in both male and female athletes included having a parent with prior ACL injury and increases of the following variables: body weight, anterior displacement of the tibia relative to the femur, genu recurvatum, and generalized joint laxity. Risk factors that are unique to female athletes included increased body mass index, increased trunk flexion strength, and prior non-ACL knee injury. The risk factors specific to male athletes were decreased standing quadriceps angle, decreased hip adduction strength, and chronic disease.

CONCLUSION

A diverse set of risk factors predispose both male and female athletes to ACL injury, whereas others appear to be sex-specific.

CLINICAL RELEVANCE

Different approaches for assessing risk and preventing ACL injury are needed for male and female athletes. In addition, personalized prevention strategies may be needed to target the specific characteristics that place an individual at increased risk of suffering this trauma.

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.

Sexual Dimorphisms in Anterior Cruciate Ligament Injury: A Current Concepts Review

Background:

Although most anterior cruciate ligament (ACL) injuries occur in male athletes, female athletes are consistently observed to be at a higher risk for sports-specific ACL injury.

Purpose:

To provide a thorough review of what is known about the sexual dimorphisms in ACL injury to guide treatment and prevention strategies and future research.

Study Design:

Narrative review.

Methods:

We conducted a comprehensive literature search for ACL-related studies published between January 1982 and September 2017 to identify pertinent studies regarding ACL injury epidemiology, prevention strategies, treatment outcomes, and dimorphisms. By performing a broad ACL injury search, we initially identified 11,453 articles. After applying additional qualifiers, we retained articles if they were published in English after 1980 and focused on sex-specific differences in any of 8 different topics: sex-specific reporting, difference in sports, selective training, hormonal effects, genetics, neuromuscular and kinematic control, anatomic differences, and outcomes.

Results:

A total of 122 articles met the inclusion criteria. In sum, the literature review indicated that female athletes are at significantly higher risk for ACL injuries than are their male counterparts, but the exact reasons for this were not clear. Initial studies focused on intrinsic differences between the sexes, whereas recent studies have shifted to focus on extrinsic factors to explain the increased risk. It is likely both intrinsic and extrinsic factors contribute to this increased risk, but further study is needed. In addition to female patients having an increased risk for ACL injuries, they are less likely than are male patients to undergo reconstructive surgery, and they experience worse postsurgical outcomes. Despite this, reconstructive surgery remains the gold standard when knee stability, return to sports, and high functional outcome scores are the goal, but further research is needed to determine why there is disparity in surgical rates and what surgical techniques optimize postsurgical outcomes for female patients.

Conclusion:

Male athletes often predominated the research concerning ACL injury and treatment, and although sex-specific reporting is progressing, it has historically been deficient. ACL injuries, prevention techniques, and ACL reconstruction require further research to maximize the health potential of at-risk female athletes.

Articular cartilage thickness changes differ between males and females 4 years following anterior cruciate ligament reconstruction

Anterior cruciate ligament injury and reconstruction (ACLR) affects articular cartilage thickness profiles about the tibial, femoral, and patellar surfaces; however, it's unclear whether the magnitudes of change in cartilage thickness, as well as the locations and areas over which these changes occur, differ between males and females. This is important to consider as differences exist between the sexes with regard to knee biomechanics, patellofemoral pain, and anatomic alignment, which influence risk of an index and repeated injury. Subjects underwent ACLR with a bone-patella tendon-bone autograft. At 4-year follow-up, they had asymptomatic knees; however, significant ACL injured-to-contralateral normal knee differences in articular cartilage thickness values were observed. Both thickening and thinning of cartilage occurred about the tibiofemoral and patellofemoral joints, relative to matched control subjects with normal knees. Further, the location of the areas and magnitudes of thickening and thinning were different between females and males. Thickening (swelling) of articular cartilage is an early finding associated with the onset of posttraumatic osteoarthritis (PTOA). Therefore, the increases in cartilage thickness that were observed in this cohort may represent early signs of the onset of PTOA that occur prior to the patient developing symptoms and radiographic evidence of this disease. The different locations of areas that underwent a change in cartilage thicknesses between males and females suggest that each sex responds differently to knee ligament trauma, reconstruction, rehabilitation, and return to activity, and indicates that sex-specific analysis should be utilized in studies of PTOA.

The Lateral Femoral Condyle Index Is Not a Risk Factor for Primary Noncontact Anterior Cruciate Ligament Injury

BACKGROUND

The lateral femoral condyle index (LFCI)-a recently developed measure of the sphericity of the lateral femoral condyle-was reported to be a risk factor for anterior cruciate ligament (ACL) injury. However, issues have been raised regarding how the index was measured and regarding the patient group and the knee in which it was measured.

PURPOSE

To investigate the association between the LFCI and the risk of sustaining a primary, noncontact ACL injury, and to examine whether this association was moderated by the posterior-inferior-directed slope of the lateral tibial plateau.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A secondary analysis was conducted of deidentified magnetic resonance images of the uninjured knees of 86 athletes with ACL injury and the corresponding knees of 86 control athletes, matched for sports team, sex, and age. From those images, we measured the LFCI and the posterior-inferior-directed slope of the middle region articular cartilage surface of the tibial plateau's lateral compartment. Conditional logistic regressions were performed to determine whether the LFCI was significantly associated with ACL injury risk and whether the lateral tibial compartment middle cartilage slope moderated this association. Data were analyzed for female and male participants separately as well as for both groups combined.

RESULTS

The LFCI was not found to be significantly associated with experiencing a primary, noncontact ACL injury for all analyses. The lateral tibial slope measure was not found to moderate the association between the LFCI and ACL injury. A conditional logistic regression analysis using the LFCI data of the injured knees, instead of the uninjured knees, of the participants with ACL injury revealed that the LFCI was significantly associated with ACL injury.

CONCLUSION

In this population of athletically active female and male participants, the LFCI was not found to be a risk factor for noncontact ACL injury, regardless of the geometric features of the lateral tibial slope.

Association of Geometric Characteristics of Knee Anatomy (Alpha Angle and Intercondylar Notch Type) With Noncontact ACL Injury

BACKGROUND

The femoral intercondylar notch type and the alpha angle (the angle between the femoral notch roof and the long axis of the femur) are easily measured in clinical settings; however, their associations with anterior cruciate ligament (ACL) injury remain unclear.

HYPOTHESIS/PURPOSE

The purpose was to determine if the alpha angle and the femoral notch type are associated with noncontact ACL injury univariately and in combination with previously identified knee geometric risk factors. We hypothesized that the alpha angle and the femoral notch type are associated with noncontact ACL injury and that the association differs between men and women.

STUDY DESIGN

Case control study; Level of evidence, 3.

METHODS

The alpha angle and the femoral notch type were measured via 3T magnetic resonance imaging (MRI) acquired from 61 women and 25 men with a first-time noncontact ACL injury. Each injured patient was matched with a control participant based on age, sex, and participation on the same sports team. A conditional logistic regression was used to assess univariate associations with ACL injury as well as multivariate associations using MRI-based risk factors of knee geometry identified in previous analyses: femoral intercondylar notch width at the anterior outlet, femoral intercondylar notch anteromedial ridge thickness, volume of the ACL, tibial plateau lateral compartment subchondral bone slope, lateral compartment middle articular cartilage slope, lateral compartment meniscus-cartilage height, lateral compartment meniscus-bone angle, and medial tibial spine volume.

RESULTS

For female athletes, the alpha angle (odds ratio, [OR], 1.82 per 1-degree increase; P = .001), the tibial lateral compartment articular cartilage slope (OR, 1.25 per 1-degree increase in the posterior-inferior directed slope; P = .022), and the femoral notch anteromedial ridge thickness (OR, 3.36 per 1-mm increase; P = .027) were independently associated with ACL disruption. For men, no other variables entered the models after the alpha angle was inputted as the first step (OR, 2.19 per 1-degree increase; P = .010).

CONCLUSION

For women, ACL injury was most strongly associated with increased alpha angle, increased tibial plateau slope, and increased femoral notch ridge thickness. For men, increased alpha angle was the most significant factor associated with ACL injury. The mechanism of injury might be associated with a combination of impingement of the ACL against the bone and increased ligament loading.

Clinical-Grade MRI-Based Methods to Identify Combined Anatomic Factors That Predict ACL Injury Risk in Male and Female Athletes

BACKGROUND

Recently developed multivariate sex-specific statistical models can predict anterior cruciate ligament (ACL) injury risk using various knee anatomic factors. However, screening tools able to identify individuals at an increased injury risk are unlikely to be developed based on these models, given that sophisticated and time-consuming methods were used to measure those factors on research-grade resolution magnetic resonance images (MRIs).

PURPOSE

To determine whether simpler methods, amenable to using clinical-grade resolution MRIs, can identify the same knee anatomic factors previously found to contribute to ACL injury risk using sophisticated methods and research-grade resolution images.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

High-resolution 3-dimensional MRIs previously acquired from 87 patients with primary, noncontact, grade III ACL injury and 87 uninjured matched control participants for a series of published studies were downgraded to clinical-grade resolution images. The 4 knee anatomic factors found to contribute to ACL injury risk in women and in men in these published studies-femoral intercondylar notch width at the anterior outlet of the ACL (NW_O), posterior-inferior directed slope of the middle region articular cartilage surface of the tibial plateau's lateral compartment (L_atT_ibMCS), ACL volume, and tibial plateau's lateral compartment posterior meniscus to subchondral bone wedge angle (L_atT_ibMBA)-were measured using clinical-grade resolution MRI-based methods. Stepwise multivariate conditional logistic regressions were used to identify the combinations of factors most highly associated with an ACL injury risk in women and men separately.

RESULTS

The multivariate model that best predicted ACL injury risk in the female participants included the L_atT_ibMCS and the NW_O. For the male participants, this model included the ACL volume and the L_atT_ibMBA. These results corroborate the previously published results that reported models with the same knee anatomic factors to best predict injury risk in this group of young women and men.

CONCLUSION

Simpler methods using MRIs downgraded to a clinical-grade resolution can identify the same knee anatomic factors previously found to significantly contribute to ACL injury risk using sophisticated methods and research-grade resolution MRIs.

Long-term outcomes of anterior cruciate ligament reconstruction surgery: 2020 OREF clinical research award paper

ACL injuries place the knee at risk for post-traumatic osteoarthritis (PTOA) despite surgical anterior cruciate ligament (ACL) reconstruction. One parameter thought to affect PTOA risk is the initial graft tension. This randomized controlled trial (RCT) was designed to compare outcomes between two graft tensioning protocols that bracket the range commonly used. At 7 years postsurgery, we determined that most outcomes between the two tension groups were not significantly different, that they were inferior to an uninjured matched control group, and that PTOA was progressing in both groups relative to controls. The trial database was also leveraged to gain insight into mechanisms of PTOA following ACL injury. We determined that the inflammatory response at the time of injury undermines one of the joint's lubricating mechanisms. We learned that patients continue to protect their surgical knee 5 years postinjury compared to controls during a jump-pivot activity. We also established that presurgical knee function and mental health were correlated with symptomatic PTOA at 7 years, that there were specific anatomical factors associated with poor outcomes, and that there were no changes in outcomes due to tunnel widening in patients receiving hamstring tendon autografts. We also validated a magnetic resonance imaging technique to noninvasively assess graft strength. In conclusion, the RCT determined that initial graft tensioning does not have a major influence on 7-year outcomes. Therefore, surgeons can reconstruct the ACL using a graft tensioning protocol that is within the window of the two graft tensioning techniques evaluated in this RCT.

A Quantifiable Risk Factor for ACL Injury: Applied Mathematics to Model the Posterolateral Tibial Plateau Surface Geometry

Background:

The mechanism for traumatic ruptures of the native anterior cruciate ligament (ACL) is frequently a noncontact injury involving a valgus moment with internal rotation of the tibia. The abnormal rotation and translation of the lateral femoral condyle posteroinferiorly relative to the lateral tibial plateau is thought to be related to the geometry of the tibial plateau.

Purpose/Hypothesis:

The purpose of the study was to mathematically model the posterior tibial plateau geometry in patients with ACL injuries and compare it with that of matched controls. The hypothesis was that increased convexity and steepness of the posterior aspect of the lateral plateau would subject knees to higher forces, leading to a potentially higher risk of ACL injury.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

We mathematically modeled the posterior curvature of the lateral tibial plateau in 64 patients with ACL injuries and 68 matched controls. Using sagittal magnetic resonance imaging scans of the knee, points on the articular cartilage of the posterolateral tibial plateau were selected and curve-fitted to a power function (y = a × xⁿ). For coefficient a and coefficient n, both variables modulated the shape of the curve, where a larger magnitude represented an increase in slope steepness. Groups were compared using a Mann-Whitney test and α < .05.

Results:

There was a significant difference in surface geometry between the patients with ACL injuries and matched controls. The equation coefficients were significantly larger in the patients with ACL injuries: coefficient a (ACL injury, 0.9 vs control, 0.68; P < .0001) and coefficient n (ACL injury, 0.34 vs control, 0.30; P = .07). For coefficient a, there was a 78.9% sensitivity, 77.5% specificity, and odds ratio of 12.6 (95% CI, 5.5-29.0) for ACL injury using a cutoff coefficient a = .78.

Conclusion:

Patients with ACL injuries had a significantly greater posterolateral plateau slope. The steeper drop off may play a role in higher anterior translation forces, coupled with internal rotation torques on the knee in noncontact injury, which could increase ACL strain and predispose to ACL injury.

Combined Injury to the ACL and Lateral Meniscus Alters the Geometry of Articular Cartilage and Meniscus Soon After Initial Trauma

Combined injury to the anterior cruciate ligament (ACL) and meniscus is associated with earlier onset and increased rates of post-traumatic osteoarthritis compared with isolated ACL injury. However, little is known about the initial changes in joint structure associated with these different types of trauma. We hypothesized that trauma to the ACL and lateral meniscus has an immediate effect on morphometry of the articular cartilage and meniscus about the entire tibial plateau that is more pronounced than an ACL tear without meniscus injury. Subjects underwent magnetic resonance imaging scanning soon after injury and prior to surgery. Those that suffered injury to the ACL and lateral meniscus underwent changes in the lateral compartment (increases in the posterior-inferior directed slopes of the articular cartilage surface, and the wedge angle of the posterior horn of the meniscus) and medial compartment (the cartilage-to-bone height decreased in the region located under the posterior horn of the meniscus, and the thickness of cartilage increased and decreased in the mid and posterior regions of the plateau, respectively). Subjects that suffered an isolated ACL tear did not undergo the same magnitude of change to these articular structures. A majority of the changes in morphometry occurred in the lateral compartment of the knee; however, change in the medial compartment of the knee with a normal appearing meniscus also occurred. Statement of clinical significance: Knee injuries that involve combined trauma to the ACL and meniscus directly affect both compartments of the knee, even if the meniscus and articular cartilage appears normal upon arthroscopic examination. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:759-767, 2020.

3D bone-shape changes and their correlations with cartilage T1ρ and T2 relaxation times and patient-reported outcomes over 3-years after ACL reconstruction

PURPOSE

(1) To identify bone-shape changes from baseline to 3-years after anterior cruciate ligament reconstruction (ACLR). (2) to assess association between changes in bone-shape from baseline to 6-months and changes in cartilage matrix and patient functions and symptoms from baseline to 3-years after ACLR.

METHODS

Bilateral knees of 30 patients with unilateral ACL injuries were scanned at baseline, 6-months, 1-, 2-, and 3-years after ACLR. Bilateral knees of 13 controls were scanned at baseline, 1- and 3-years. Mean T1ρ and T2 values of each cartilage compartment were computed. Bone shape was quantified using statistical shape modeling (SSM) and 3D-MRI. Patient functions and symptoms were evaluated using Knee Injury and Osteoarthritis Outcome Score (KOOS).

RESULTS

Statistically significant changes were observed in Femur 2 (medial femoral condyle [MF] shape), Femur 6 (intercondylar notch width), Tibia 1 (tibia plateau area), and Tibia 7 (medial tibia slope) over 3-years after ACLR. Statistically significant differences were observed between injured and control knees in several modes. Statistically significant correlations were found between changes in bone shape (ΔFemur 6, ΔFemur 8 [trochlea inclination and MF height], ΔTibia 1) from baseline to 6-months and that of cartilage T1ρ and T2 and KOOS from baseline to 3-years after ACLR.

CONCLUSION

Bone shape remodeling occurs after ACLR, and early bone shape changes (within 6 months) correlated with cartilage matrix and patient outcomes at 3-years after ACLR. Bone shape can be a promising imaging biomarker that stratifies patients at high risk for post-traumatic osteoarthritis (PTOA).

RISK FACTORS ASSOCIATED WITH NON-CONTACT ANTERIOR CRUCIATE LIGAMENT INJURY: A SYSTEMATIC REVIEW

BACKGROUND

With the increasing number of individuals participating in sports every year, injury - specifically anterior cruciate ligament (ACL) injury - remains an inherent risk factor for participants. The majority of ACL injuries occur from a non-contact mechanism, and there is a high physical and financial burden associated with injury. Understanding the risk factors for ACL injury may aid in the development of prevention efforts.

PURPOSE

The purpose of this review was to synthesize and appraise existing literature for risk factors associated with non-contact anterior cruciate ligament (ACL) injury in both sexes.

STUDY DESIGN

Systematic review.

METHODS

An electronic literature search was conducted utilizing the MEDLINE database and The Cochrane library for articles available through February 2016. All titles and abstracts were reviewed and full text articles meeting eligibility criteria were assessed in detail to determine inclusion or exclusion. Articles reviewed in full text were reviewed for scientific evidence of risk factors for ACL injury. Results from studies were extracted and initially classified as either intrinsic or extrinsic risk factors, and then further categorized based upon the evidence presented in the studies meeting inclusion criteria. Data extracted from eligible studies included general study characteristics (study design, sample characteristics), methodology, and results for risk factors included.

RESULTS

Principal findings of this systematic review identified the following risk factors for ACL injury in both sexes: degrading weather conditions, decreased intercondylar notch index or width, increased lateral or posterior tibial plateau slope, decreased core and hip strength, and potential genetic influence.

CONCLUSIONS

Neuromuscular and biomechanical risk factors may be addressed through neuromuscular preventative training programs. Though some extrinsic and other inherent physiological factors tend to be non-modifiable, attempts to improve upon those modifiable factors may lead to a decreased incidence of ACL injury.

LEVEL OF EVIDENCE

2a.

Geometric Characteristics of the Knee Are Associated With a Noncontact ACL Injury to the Contralateral Knee After Unilateral ACL Injury in Young Female Athletes

BACKGROUND

Contralateral anterior cruciate ligament (CACL) injury after recovery from a first-time ACL rupture occurs at a high rate in young females; however, little is known about the risk factors associated with bilateral ACL trauma.

HYPOTHESIS

The geometric characteristics of the contralateral knee at the time of the initial ACL injury are associated with risk of suffering a CACL injury in these female athletes.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Sixty-two female athletes who suffered their first noncontact ACL injury while participating in sports at the high school or college level were identified, and geometry of the femoral notch, ACL, tibial spines, tibial subchondral bone, articular cartilage surfaces, and menisci of the contralateral, uninjured, knee was characterized in 3 dimensions. We were unable to contact 7 subjects and followed the remaining 55 until either a CACL injury or an ACL graft injury occurred or, if they were not injured, until the date of last contact (mean, 34 months after their first ACL injury). Cox regression was used to identify risk factors for CACL injury.

RESULTS

Ten (18.2%) females suffered a CACL injury. Decreases of 1 SD in femoral intercondylar notch width (measured at its outlet and anterior attachment of the ACL) were associated with increases in the risk of suffering a CACL injury (hazard ratio = 1.88 and 2.05, respectively). Likewise, 1 SD decreases in medial-lateral width of the lateral tibial spine, height of the medial tibial spine, and thickness of the articular cartilage located at the posterior region of the medial tibial compartment were associated with 3.59-, 1.75-, and 2.15-fold increases in the risk of CACL injury, respectively.

CONCLUSION

After ACL injury, subsequent injury to the CACL is influenced by geometry of the structures that surround the ACL (the femoral notch and tibial spines). This information can be used to identify individuals at increased risk for CACL trauma, who might benefit from targeted risk-reduction interventions.

Relationship between geometry of the extensor mechanism of the knee and risk of anterior cruciate ligament injury

The complex inter-segmental forces that are developed across an extended knee by body weight and contraction of the quadriceps muscle group transmits an anteriorly directed force on the tibia that strain the anterior cruciate ligament (ACL). We hypothesized that a relationship exists between geometry of the knees extensor mechanism and the risk of sustaining a non-contact ACL injury. Geometry of the extensor mechanism was characterized using MRI scans of the knees of 88 subjects that suffered their first non-contact ACL injury and 88 matched control subjects with normal knees that were on the same team. The orientation of the patellar tendon axis was measured relative to the femoral flexion-extension axis to determine the extensor moment arm (EMA), and relative to tibial long axis to measure coronal patellar tendon angle (CPTA) and sagittal patellar tendon angle (SPTA). Associations between these parameters and ACL injury risk were tested with and without adjustment for flexion and internal rotation position of the tibia relative to the femur during MRI data acquisition. After adjustment for internal rotation position of the tibia relative to the femur there were no associations between EMA, CPTA, and SPTA and risk of suffering an ACL injury. However, increased internal rotation position of the tibia relative to the femur was significantly associated with increased risk of ACL injury in female athletes both in univariate analysis (Odds Ratio = 1.16 per degree of internal rotation of the tibia, p = 0.002), as well as after adjustment for EMA, CPTA, and SPTA.: © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:965-973, 2017.

Nonmodifiable risk factors for anterior cruciate ligament injury

PURPOSE OF REVIEW

As anterior cruciate ligament (ACL) injury is becoming increasingly prevalent in the population of active children and young adolescents, it is crucial to be aware of both the modifiable and nonmodifiable factors that place this population at increased ACL injury risk. Historically, there has not been a definitive consensus on all of these risk factors-particularly the nonmodifiable ones.

RECENT FINDINGS

The present review has accumulated the most recent evidence for the nonmodifiable risk factors in ACL injury focusing particularly on female gender, generalized joint laxity, knee recurvatum, increased lateral tibial slope, decreased intercondylar notch width, structural lower extremity valgus, limb length discrepancy, family history, and history of contralateral knee ACL injury.

SUMMARY

Physicians should be aware of the nonmodifiable risk factors for ACL tears in active children and adolescents and should also encourage avoidance of modifiable risk factors in this population. Young athletes with nonmodifiable risk factors are at a particularly increased risk of recurrent injury following ACL reconstruction (ACLR). We believe that a primary extra-articular augmentation via iliotibial band tenodesis at the same time of ACLR may decrease the rate of reinjury for the high risk athlete with multiple nonmodifiable risk factors.

Risk of Noncontact Anterior Cruciate Ligament Injuries Is Not Associated With Slope and Concavity of the Tibial Plateau in Recreational Alpine Skiers: A Magnetic Resonance Imaging-Based Case-Control Study of 121 Patients

BACKGROUND

Anatomic features of the tibial plateau (ie, posterior slope and medial concavity) have been associated with an increased risk of anterior cruciate ligament (ACL) injuries. However, it remains unclear whether these findings translate to ACL injuries sustained during recreational alpine skiing.

PURPOSE

To investigate the association in recreational alpine skiers between prominent morphological features of the tibial plateau (slope and concavity) and the risk of sustaining an ACL injury during a noncontact incident.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Magnetic resonance imaging data of 121 recreational alpine skiers (74 female, 47 male) after a noncontact knee injury were used for this study. Of these patients, 80 (71% female [n = 57]) had a complete unilateral ACL tear (rupture group), and 41 (41% female [n = 17]) had no indications of an ACL injury (intact group). Two blinded independent examiners measured the slopes of the tibial plateau in the sagittal and coronal planes along with the maximum depth of the medial tibial plateau. Measurements were compared between sexes and between groups using t tests. Logistic regression was used to assess the associations between quantified anatomic indices and the risk of ACL injuries.

RESULTS

Within 121 study patients, female skiers had greater odds of an ACL tear compared with male skiers (odds ratio, 3.5; 95% CI, 1.6-7.8; P < .001). Female skiers were more likely to have a greater lateral tibial slope (LTS) (P = .02) and medial tibial slope (MTS) (P = .02) with a shallower medial tibial depth (MTD) (P = .02) compared with male skiers. No differences between sexes were observed in the coronal tibial slope (CTS) (P = .97). Male and female skiers as a combined group showed no associations between quantified anatomic indices and the risk of sustaining an ACL tear (P > .10). Likewise, no significant differences were observed between the intact versus rupture group in any of the quantified anatomic indices (P > .10). Similar findings were observed when the analyses were repeated on male and female skiers separately.

CONCLUSION

Despite differences between sexes in knee anatomy and the injury risk, the sagittal and coronal slopes (LTS, MTS, CTS), as well as the concavity of the medial tibial plateau (MTD), were not associated with the risk of an ACL tear during a noncontact injury among recreational alpine skiers.

Multivariate Analysis of the Risk Factors for First-Time Noncontact ACL Injury in High School and College Athletes: A Prospective Cohort Study With a Nested, Matched Case-Control Analysis

BACKGROUND

Multivariate analysis that identifies the combination of risk factors associated with anterior cruciate ligament (ACL) trauma is important because it provides insight into whether a variable has a direct causal effect on risk or an indirect effect that is mediated by other variables. It can also reveal risk factors that might not be evident in univariate analyses; if a variable's effect is moderated by other variables, its association with risk may be apparent only after adjustment for the other variables. Most important, multivariate analyses can identify combinations of risk factors that are more predictive of risk than individual risk factors.

HYPOTHESIS

A diverse combination of risk factors predispose athletes to first-time noncontact ACL injury, and these relationships are different for male and female athletes.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Athletes competing in organized sports at the high school and college levels participated in this study. Data from injured subjects (109 suffering an ACL injury) and matched controls (227 subjects) from the same athletic team were analyzed with multivariate conditional logistic regression to examine the effects of combinations of variables (demographic characteristics, joint laxity, lower extremity alignment, strength, and personality traits) on the risk of suffering their first ACL injury and to construct risk models.

RESULTS

For male athletes, increases in anterior-posterior displacement of the tibia relative to the femur (knee laxity), posterior knee stiffness, navicular drop, and a decrease in standing quadriceps angle were jointly predictive of suffering an ACL injury. For female athletes the combined effects of having a parent who had suffered an ACL injury and increases in anterior-posterior knee laxity and body mass index were predictive of ACL injury.

CONCLUSION

Multivariate models provided more information about ACL injury risk than individual risk factors. Both male and female risk models included increased anterior-posterior knee laxity as a predictor of ACL injury but were otherwise dissimilar.

Novel measure of articular instability based on contact stress confirms that the anterior cruciate ligament is a critical stabilizer of the lateral compartment

Knee instability following anterior cruciate ligament (ACL) rupture is common, compromising function, and causing cartilage and meniscal damage. In this study, instability at the level of the articular surfaces was characterized with a new measure: articular instability. Articular instability was defined as the change in location of the center of contact stress per unit of applied load. The effect of ACL-deficiency on articular instability was quantified in response to combined abduction and internal rotation moments simulating the clinical pivot shift, which recreates the sensation of instability. Eleven cadaver knees were loaded using a robotic manipulator and tibiofemoral contact stress was measured using a stress transducer. Sectioning the ACL led to pronounced articular instability on the lateral compartment in 4 of 11 knees. In these 4 knees articular instability increased posteriorly up to 403% and increased laterally up to 754%. Factors driving inter-specimen variations in articular instability might include articular morphology, ligamentous laxity, and the applied loads. This novel description of contact mechanics confirms that the ACL prevents sudden changes in the relative position of the lateral articular surfaces. It is applicable to any loading conditions and provides a unique measure to quantify the effects of ACL injury and reconstruction.

Combined anatomic factors predicting risk of anterior cruciate ligament injury for males and females

BACKGROUND

Knee joint geometry has been associated with risk of suffering an anterior cruciate ligament (ACL) injury; however, few studies have utilized multivariate analysis to investigate how different aspects of knee joint geometry combine to influence ACL injury risk.

HYPOTHESES

Combinations of knee geometry measurements are more highly associated with the risk of suffering a noncontact ACL injury than individual measurements, and the most predictive combinations of measurements are different for males and females.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A total of 88 first-time, noncontact, grade III ACL-injured subjects and 88 uninjured matched-control subjects were recruited, and magnetic resonance imaging data were acquired. The geometry of the tibial plateau subchondral bone, articular cartilage, and meniscus; geometry of the tibial spines; and size of the femoral intercondylar notch and ACL were measured. Multivariate conditional logistic regression was used to develop risk models for ACL injury in females and males separately.

RESULTS

For females, the best fitting model included width of the femoral notch at its anterior outlet and the posterior-inferior-directed slope of the lateral compartment articular cartilage surface, where a millimeter decrease in notch width and a degree increase in slope were independently associated with a 50% and 32% increase in risk of ACL injury, respectively. For males, a model that included ACL volume and the lateral compartment posterior meniscus to subchondral bone wedge angle was most highly associated with risk of ACL injury, where a 0.1 cm3 decrease in ACL volume (approximately 8% of the mean value) and a degree decrease in meniscus wedge angle were independently associated with a 43% and 23% increase in risk, correspondingly.

CONCLUSION

Combinations of knee joint geometry measurements provided more information about the risk of noncontact ACL injury than individual measures, and the aspects of geometry that best explained the relationship between knee geometry and the risk of injury were different between males and females. Consequently, a female with both a decreased femoral notch width and an increased posterior-inferior-directed lateral compartment tibial articular cartilage slope combined or a male with a decreased ACL volume and decreased lateral compartment posterior meniscus angle were most at risk for sustaining an ACL injury.

Tibial articular cartilage and meniscus geometries combine to influence female risk of anterior cruciate ligament injury

Tibial plateau subchondral bone geometry has been associated with the risk of sustaining a non-contact ACL injury; however, little is known regarding the influence of the meniscus and articular cartilage interface geometry on risk. We hypothesized that geometries of the tibial plateau articular cartilage surface and meniscus were individually associated with the risk of non-contact ACL injury. In addition, we hypothesized that the associations were independent of the underlying subchondral bone geometry. MRI scans were acquired on 88 subjects that suffered non-contact ACL injuries (27 males, 61 females) and 88 matched control subjects that were selected from the injured subject's teammates and were thus matched on sex, sport, level of play, and exposure to risk of injury. Multivariate analysis of the female data revealed that increased posterior-inferior directed slope of the middle articular cartilage region and decreased height of the posterior horn of the meniscus in the lateral compartment were associated with increased risk of sustaining a first time, non-contact ACL injury, independent of each other and of the slope of the tibial plateau subchondral bone. No measures were independently related to risk of non-contact ACL injury among males.

A decreased volume of the medial tibial spine is associated with an increased risk of suffering an anterior cruciate ligament injury for males but not females

Measurements of tibial plateau subchondral bone and articular cartilage slope have been associated with the risk of suffering anterior cruciate ligament (ACL) injury. Such single-plane measures of the tibial plateau may not sufficiently characterize its complex, three-dimensional geometry and how it relates to knee injury. Further, the tibial spines have not been studied in association with the risk of suffering a non-contact ACL injury. We questioned whether the geometries of the tibial spines are associated with non-contact ACL injury risk, and if this relationship is different for males and females. Bilateral MRI scans were acquired on 88 ACL-injured subjects and 88 control subjects matched for sex, age and sports team. Medial and lateral tibial spine geometries were characterized with measurements of length, width, height, volume and anteroposterior location. Analyses of females revealed no associations between tibial spine geometry and risk of ACL injury. Analyses of males revealed that an increased medial tibial spine volume was associated with a decreased risk of ACL injury (OR = 0.667 per 100 mm(3) increase). Smaller medial spines could provide less resistance to internal rotation and medial translation of the tibia relative to the femur, subsequently increasing ACL strains and risk of ACL injury.

Changes to the articular cartilage thickness profile of the tibia following anterior cruciate ligament injury

OBJECTIVES

We sought to determine if anterior cruciate ligament (ACL)-injured subjects demonstrated side-to-side differences in tibial cartilage thickness soon after injury, and if uninjured-control subjects displayed side-to-side symmetry in cartilage thickness. Second, we aimed to investigate associations between body mass index (BMI), cross-sectional area (CSA) of the proximal tibia, and articular cartilage thickness differences.

METHODS

Bilateral Magnetic Resonance Images (MRIs) were obtained on 88 ACL-injured subjects (27 male; 61 female) a mean 27 days post-injury, and 88 matched uninjured control subjects. Within ACL-injured and uninjured control subjects, side-to-side differences in medial and lateral tibial articular cartilage thickness were analyzed with adjustment for tibial position relative to the femur during MRI acquisition. Associations between tibial CSA and cartilage thickness differences were tested within high and low BMI groups.

RESULTS

Within the medial tibial compartment, ACL-injured females displayed significant increases: mean (confidence interval (CI)) = +0.18 mm (0.17, 0.19) and decreases: mean (CI) = -0.14 mm (-0.13, -0.15) in tibial cartilage thickness within the central and posterior cartilage regions respectively. Adjustment for tibial position revealed a decreased area of significant cartilage thickness differences, though 46% of points maintained significance. In the lateral compartment anterior region, there was a significantly different relationship between cartilage thickness differences and CSA, within high and low BMI groups (BMI group*CSA interaction, P = 0.007). Within the low BMI group, a significant negative correlation between cartilage thickness and CSA was identified (P = 0.03).

CONCLUSIONS

ACL-injured females displayed cartilage thickness differences in the central, and posterior medial tibial cartilage regions. Tibial position effected thickness differences, but did not account for all significant differences.

Increased slope of the lateral tibial plateau subchondral bone is associated with greater risk of noncontact ACL injury in females but not in males: a prospective cohort study with a nested, matched case-control analysis

BACKGROUND

There is an emerging consensus that increased posterior-inferior directed slope of the subchondral bone portion of the tibial plateau is associated with increased risk of suffering an anterior cruciate ligament (ACL) injury; however, most of what is known about this relationship has come from unmatched case-control studies. These observations need to be confirmed in more rigorously designed investigations.

HYPOTHESIS

Increased posterior-inferior directed slope of the medial and lateral tibial plateaus are associated with increased risk of suffering a noncontact ACL injury.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

In sum, 176 athletes competing in organized sports at the college and high school levels participated in the study: 88 suffering their first noncontact ACL injury and 88 matched controls. Magnetic resonance images were acquired, and geometry of the subchondral bone portion of the tibial plateau was characterized on each athlete bilaterally by measuring the medial and lateral tibial plateau slopes, coronal tibial slope, and the depth of the medial tibial plateau. Comparisons between knees of the same person were made with paired t tests, and associations with injury risk were assessed by conditional logistic regression analysis of ACL-injured and control participants.

RESULTS

Controls exhibited side-to-side symmetry of subchondral bone geometry, while the ACL-injured athletes did not, suggesting that the ACL injury may have changed the subchondral bone geometry. Therefore, the uninjured knees of the ACL-injured athletes and the corresponding limbs of their matched controls were used to assess associations with injury risk. Analyses of males and females as a combined group and females as a separate group showed a significant association between ACL injury risk and increased posterior-inferior directed slope of the lateral tibial plateau slope. This relationship was not apparent when males were analyzed as a group. Multivariate analyses indicated that these results were independent of the medial tibial plateau slope, coronal tibial slope, and depth of the medial tibial plateau, which were not associated with ACL injury.

CONCLUSION

There is a 21.7% increased risk of noncontact ACL injury with each degree increase of the lateral tibial plateau slope among females but not among males. The medial tibial plateau slope, coronal tibial slope, and depth of the medial tibial plateau were not associated with risk of injury for females or males.