Hewett, Timothy E.

Background: Previous work shows that young athletes after anterior cruciate ligament reconstruction (ACLR) demonstrate single-leg (SL) landing movement asymmetries at the time of return to sport (RTS); however, the effect of movement asymmetries on longitudinal knee-related function after ACLR has not been examined. Hypothesis/Purpose: The purpose of this study was to examine the effect of SL drop-landing movement symmetry at the time of RTS on knee-related function 2 years later in young athletes after ACLR. The first hypothesis was that young athletes who demonstrated SL drop-landing asymmetries at RTS would demonstrate decreased knee function 2 years later compared with those who demonstrated symmetric SL drop-landing mechanics. The second hypothesis was that SL drop-landing movement symmetry at RTS would be associated with knee functional recovery 2 years later. Study Design: Cohort study; Level of evidence, 2. Methods: This study included 48 young athletes who had undergone ACLR and were assessed at the time of RTS (77% female; mean [±SD] age at RTS, 17.6 ± 2.6 years) and followed for 2 years after RTS. Three sagittal-plane landing variables of interest were calculated using 3-dimensional motion analysis during an SL drop-landing task at the time of RTS: knee flexion excursion, peak internal knee extension moment, and peak trunk flexion. The limb symmetry index (LSI) was calculated for each landing variable using the following: LSI = (involved/uninvolved) × 100%. The LSI was used to divide the cohort into symmetric (SYM) and asymmetric (ASYM) groups for each landing variable: knee flexion excursion (SYM: LSI ≥ 90% [n = 23]; ASYM: LSI < 85% [n = 18]), peak internal knee extension moment (SYM: LSI ≥ 90% [n = 19]; ASYM: LSI < 85% [n = 22]), and peak trunk flexion (SYM: LSI ≤ 105% [n = 25]; ASYM: LSI > 115% [n = 19]). At 2 years after RTS, knee-related function was evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS), International Knee Documentation Committee (IKDC) subjective knee form, and performance on SL hop tests. Functional recovery was defined based on literature cutoffs for knee-related functional measures. Differences in 2-year function were compared between the symmetry groups using Mann-Whitney U tests because of nonnormality. Logistic regression was used to determine if landing symmetry at the time of RTS would be associated with 2-year knee functional recovery after RTS. Results: The ASYM knee flexion excursion group demonstrated decreased function at 2 years after RTS compared with the SYM group on the KOOS-Pain (ASYM: 93.0 ± 8.2; SYM: 98.4 ± 3.0; P = .008) and the KOOS–Quality of Life (ASYM: 81.6 ± 16.1; SYM: 94.1 ± 9.7; P = .008). Knee flexion excursion was associated with knee functional recovery on the KOOS-Pain and the KOOS–Quality of Life ( P = .033 and P = .012, respectively) at 2 years after RTS, after controlling for the quadriceps strength LSI and graft type. Conclusion: Young athletes after ACLR with asymmetries in knee kinematics at the time of RTS reported decreased self-reported function 2 years later; however, the clinical importance of these differences needs to be further understood.

Hypermobility may be associated with decreased lower extremity proprioception, which in turn may increase injury risk. The prevalence of hypermobility in dancers varies across studies, but joint hypermobility appears to be more common in dancers than in the general population. The purpose of this study was to determine how hypermobility affects eyes-closed single-limb balance as an indirect measure of proprioception in dancers. The secondary aim was to compare hypermobility and balance across dancer affiliation groups. Data were collected from 45 professional dancers, 11 collegiate modern dancers, 227 student dancers, and 15 pre-professional dancers during routine dance screens. Dancer hypermobility status was assessed via an eight-point Beighton-Horan Laxity test. Single-limb balance time, in seconds, was assessed in parallel position with the eyes closed. Hypermobile (HM) and non-hy-permobile (NHM) dancers showed very similar balance times (HM median: 36.5 seconds; NHM median: 33.0 seconds; p = 0.982). Hypermobility was not significantly different between dancer affiliation groups (p = 0.154): 47% in ballet academy students, 27% in collegiate modern dancers, 62% in pre-professional dancers, and 36% in professional dancers. The student, pre-professional, and professional ballet dancers all demonstrated longer balance times than the collegiate modern dancers; however, this difference was only significant between the professional ballet dancers and collegiate modern dancers (p = 0.026). Dancers demonstrated a higher prevalence of hypermobility than what has been reported for the general population. Joint hypermobility did not affect eyes-closed single-limb balance time. Future studies are needed to determine if joint hypermobility affects more sensitive measures of proprioception and risk of injury.

Background Knee injuries are prevalent in cutting, pivoting, and jumping sports. Studies have investigated the effects of exercise-based knee injury prevention programs, however no clinical practice guidelines (CPG) exist. Objective 1) Review the evidence for exercise-based knee injury prevention programs, 2) identify if there are exercise-based knee injury prevention programs that are effective for particular groups of athletes, 3) explore the evidence for dosage and delivery of exercise-based knee injury prevention programs, 4) provide information on how exercise-based knee injury prevention should be implemented. Design Systematic review for CPG development. Setting Multiple. Patients (or Participants) Healthy, active individuals, particularly athletes participating in cutting, pivoting, and jumping sports. Interventions (or Assessment of Risk Factors) A systematic review of literature was performed via PubMed, Scopus, SportDiscus, CINAHL, and the Cochrane databases for relevant articles addressing the effects of an exercise-based knee injury prevention program. The final search was performed in April, 2016 to identify all articles published prior to that point. Main Outcome Measurements The effects and outcomes of exercise-based knee injury prevention programs. Results Thirty-seven studies met the inclusion criteria for this CPG. Exercise-based knee injury prevention programs have a low implementation cost and large relative risk reductions. Clinicians should implement an exercise-based knee injury prevention program for all athletes involved in cutting and pivoting type sports to reduce the number of significant knee injuries. The program should be implemented two to three times per week in the preseason and one to three times per week in the competitive season. It should consist of a combination of plyometric training, strength and power exercises, balance and dynamic stabilization training, core strengthening, technique training, and/or sports-specific drills. Conclusions This CPG will provide evidence based guidance for clinicians in choosing and implementing exercise-based knee injury prevention programs appropriate for the athlete(s) they work with.

Background: The effects of targeted neuromuscular training (TNMT) on movement biomechanics associated with the risk of anterior cruciate ligament (ACL) injuries are currently unknown. Purpose/Hypotheses: To determine the effectiveness of TNMT specifically designed to increase trunk control and hip strength. The hypotheses were that (1) TNMT would decrease biomechanical and neuromuscular factors related to an increased ACL injury risk and (2) TNMT would decrease these biomechanical and neuromuscular factors to a greater extent in athletes identified as being at a high risk for future ACL injuries. Study Design: Controlled laboratory study. Methods: Female athletes who participated in jumping, cutting, and pivoting sports underwent 3-dimensional biomechanical testing before the season and after completing TNMT. During testing, athletes performed 3 different types of tasks: (1) drop vertical jump, (2) single-leg drop, and (3) single-leg cross drop. Analysis of covariance was used to examine the treatment effects of TNMT designed to enhance core and hip strength on biomechanical and neuromuscular characteristics. Differences were also evaluated by risk profile. Differences were considered statistically significant at P < .05. Results: TNMT significantly increased hip external rotation moments and moment impulses, increased peak trunk flexion, and decreased peak trunk extension. Athletes with a high risk before the intervention (risk profile III) had a more significant treatment effect of TNMT than low-risk groups (risk profiles I and II). Conclusion: TNMT significantly improved proximal biomechanics, including increased hip external rotation moments and moment impulses, increased peak trunk flexion, and decreased peak trunk extension. TNMT that focuses exclusively on proximal leg and trunk risk factors is not, however, adequate to induce significant changes in frontal-plane knee loading. Biomechanical changes varied across the risk profile groups, with higher risk groups exhibiting greater improvements in their biomechanics.

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.