Bates, Nathaniel A.

Background: The reported rate of second anterior cruciate ligament (ACL) injuries (20%-30%), including graft failure and contralateral ACL tears, after ACL reconstruction (ACLR) or nonoperative therapy indicates that multiple factors may predispose patients to subsequent ACL injuries. Purpose: To determine the incidence of second ACL injuries in a population-based cohort over a 10-year observation period (2001-2010) and to identify factors that contribute to the risk of second injuries. Study Design: Descriptive epidemiological study. Methods: International Classification of Diseases, 9th Revision (ICD-9) codes relevant to the diagnosis of an ACL tear and the procedure code for ACLR were utilized to search the Rochester Epidemiology Project, a multidisciplinary county database, between the years of 2001 and 2010. The complete medical records for all cases were reviewed to confirm diagnosis and treatment details. A total of 914 unique patients with 1019 acute, isolated ACL tears were identified. These patients were stratified by primary and secondary tears, sex, age, activity level, side of injury, sex × side of injury, and graft type of reconstruction. Results: Second ACL tears were recorded in 141 (13.8%) of the 914 patients diagnosed with an ACL tear in Olmsted County, Minnesota, USA, from 2001 to 2010; 50.4% of these occurred in the contralateral knee. A noncontact mechanism was responsible for 76.4% of all ACL injuries. A second ACL injury was influenced by factors of sex × age group, treatment type × age group, and treatment type × activity level. Nonparametric analysis of graft disruption × graft type demonstrated that a higher prevalence of second ACL tears occurred with allografts compared with hamstring autografts ( P = .0054) and patellar tendon autografts ( P = .0001). Conclusion: The incidence of second ACL tears in this population-based cohort was 13.8%, and half occurred to the ACL of the contralateral knee. Statistically, second ACL injuries differed by sex, occurring in female patients younger than 25 years and male patients aged 26 to 45 years. Allografts continued to be associated with a greater risk of second ACL injuries compared with hamstring and patellar tendon autografts. Nonoperative treatment carried more risk of contralateral tears than ACLR.

Background: Second anterior cruciate ligament (ACL) tears after reconstruction occur at a reported rate of 20% to 30%. This high frequency indicates that there may be factors that predispose an athlete to graft failure and ACL tears of the contralateral knee. Purpose: To determine the incidence of second ACL injuries in a geographic population-based cohort over a 10-year observation period. Study Design: Descriptive epidemiological study. Methods: International Classification of Diseases, 9th Revision (ICD-9) codes relevant to the diagnosis of an ACL tear and the procedure code for ACL reconstruction were searched across the Rochester Epidemiology Project, a multidisciplinary county database, between the years of 1990 and 2000. This cohort of patients was tracked for subsequent ACL injuries through December 31, 2015. The authors identified 1041 patients with acute, isolated ACL tears. These patients were stratified by primary and secondary tears, sex, age, activity level, side of injury, sex by side of injury, and graft type. Results: Of the 1041 unique patients with a diagnosed ACL tear in Olmsted County, Minnesota, from 1990 to 2000, there were 66 (6.0%) second ACL tears; 66.7% of these tears occurred on the contralateral side. A second ACL injury was influenced by graft type ( P < .0001), election of ACL reconstruction ( P = .0060), and sex by side of injury ( P = .0072). Nonparametric analysis of graft disruption by graft type demonstrated a higher prevalence of second ACL tears with allografts compared with hamstring ( P = .0499) or patellar tendon autografts ( P = .0012). Conclusion: The incidence of second ACL tears in this population-based cohort was 6.0%, with 66.7% of these tears occurring on the contralateral side from the original injury. There was a high population incidence of second ACL injuries in female patients younger than age 20 years. The utilization of patellar tendon autografts significantly reduced the risk of second ACL injuries compared with allografts or hamstring autografts in this cohort.

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.

Background: Tibial slope angle is a nonmodifiable risk factor for anterior cruciate ligament (ACL) injury. However, the mechanical role of varying tibial slopes during athletic tasks has yet to be clinically quantified. Purpose: To examine the influence of posterior tibial slope on knee joint loading during controlled, in vitro simulation of the knee joint articulations during athletic tasks. Study Design: Descriptive laboratory study. Methods: A 6 degree of freedom robotic manipulator positionally maneuvered cadaveric knee joints from 12 unique specimens with varying tibial slopes (range, −7.7° to 7.7°) through drop vertical jump and sidestep cutting tasks that were derived from 3-dimensional in vivo motion recordings. Internal knee joint torques and forces were recorded throughout simulation and were linearly correlated with tibial slope. Results: The mean (±SD) posterior tibial slope angle was 2.2° ± 4.3° in the lateral compartment and 2.3° ± 3.3° in the medial compartment. For simulated drop vertical jumps, lateral compartment tibial slope angle expressed moderate, direct correlations with peak internally generated knee adduction ( r = 0.60-0.65), flexion ( r = 0.64-0.66), lateral ( r = 0.57-0.69), and external rotation torques ( r = 0.47-0.72) as well as inverse correlations with peak abduction ( r = −0.42 to −0.61) and internal rotation torques ( r = −0.39 to −0.79). Only frontal plane torques were correlated during sidestep cutting simulations. For simulated drop vertical jumps, medial compartment tibial slope angle expressed moderate, direct correlations with peak internally generated knee flexion torque ( r = 0.64-0.69) and lateral knee force ( r = 0.55-0.74) as well as inverse correlations with peak external torque ( r = −0.34 to −0.67) and medial knee force ( r = −0.58 to −0.59). These moderate correlations were also present during simulated sidestep cutting. Conclusion: The investigation supported the theory that increased posterior tibial slope would lead to greater magnitude knee joint moments, specifically, internally generated knee adduction and flexion torques. Clinical Relevance: The knee torques that positively correlated with increased tibial slope angle in this investigation are associated with heightened risk of ACL injury. Therefore, the present data indicated that a higher posterior tibial slope is correlated to increased knee loads that are associated with heightened risk of ACL injury.

Background: Anterior cruciate ligament (ACL) injuries are physically and financially devastating but affect a relatively small percentage of the population. Prospective identification of risk factors for ACL injury necessitates a large sample size; therefore, study of this injury would benefit from a multicenter approach. Purpose: To determine the reliability of kinematic and kinetic measures of a single-leg cross drop task across 3 institutions. Study Design: Controlled laboratory study. Methods: Twenty-five female high school volleyball players participated in this study. Three-dimensional motion data of each participant performing the single-leg cross drop were collected at 3 institutions over a period of 4 weeks. Coefficients of multiple correlation were calculated to assess the reliability of kinematic and kinetic measures during the landing phase of the movement. Results: Between-centers reliability for kinematic waveforms in the frontal and sagittal planes was good, but moderate in the transverse plane. Between-centers reliability for kinetic waveforms was good in the sagittal, frontal, and transverse planes. Conclusion: Based on these findings, the single-leg cross drop task has moderate to good reliability of kinematic and kinetic measures across institutions after implementation of a standardized testing protocol. Clinical Relevance: Multicenter collaborations can increase study numbers and generalize results, which is beneficial for studies of relatively rare phenomena, such as ACL injury. An important step is to determine the reliability of risk assessments across institutions before a multicenter collaboration can be initiated.

Background: The medial collateral (MCL) and anterior cruciate ligaments (ACL) are, respectively, the primary and secondary ligamentous restraints against knee abduction, which is a component of the valgus collapse often associated with ACL rupture during athletic tasks. Despite this correlation in function, MCL ruptures occur concomitantly in only 20% to 40% of ACL injuries. Hypothesis/Purpose: The purpose of this investigation was to determine how athletic tasks load the knee joint in a manner that could lead to ACL failure without concomitant MCL failure. It was hypothesized that (1) the ACL would provide greater overall contribution to intact knee forces than the MCL during simulated motion tasks and (2) the ACL would show greater relative peak strain compared with the MCL during simulated motion tasks. Study Design: Controlled laboratory study. Methods: A 6-degrees-of-freedom robotic manipulator articulated 18 cadaveric knees through simulations of kinematics recorded from in vivo drop vertical jump and sidestep cutting tasks. Specimens were articulated in the intact-knee and isolated-ligament conditions. After simulation, each ACL and MCL was failed in uniaxial tension along its fiber orientations. Results: During a drop vertical jump simulation, the ACL experienced greater peak strain than the MCL (6.1% vs 0.4%; P < .01). The isolated ACL expressed greater peak anterior force (4.8% vs 0.3% body weight; P < .01), medial force (1.6% vs 0.4% body weight; P < .01), flexion torque (8.4 vs 0.4 N·m; P < .01), abduction torque (2.6 vs 0.3 N·m; P < .01), and adduction torque (0.5 vs 0.0 N·m; P = .03) than the isolated MCL. During failure testing, ACL specimens preferentially loaded in the anteromedial bundle failed at 637 N, while MCL failure occurred at 776 N. Conclusion: During controlled physiologic athletic tasks, the ACL provides greater contributions to knee restraint than the MCL, which is generally unstrained and minimally loaded. Clinical Relevance: Current findings support that multiplanar loading during athletic tasks preferentially loads the ACL over the MCL, leaving the ACL more susceptible to injury. An enhanced understanding of joint loading during in vivo tasks may provide insight that enhances the efficacy of injury prevention protocols.