ACL Injury Risk Research Articles

Return to Sport: Does 6-month Functional Testing Predict Second ACL Injuries at Long-term Follow-Up?

Objectives: Following ACL reconstruction, objective measurements of functional testing are often incorporated into the decision-making process with regard to clearance for return to sport (RTS), in order to reduce the risk of second ACL injury. However, there is limited data to assess the predictive value of functional testing to risk of second ACL injury. Therefore, the purpose of this study was to determine whether performance on functional testing following primary ACL reconstruction can predict second ACL injuries. Methods: Patient records were retrospectively analyzed for individuals who presented with an ACL injury at a single institution from 1990-2010. A total of 335 patients who underwent primary ACL reconstruction, had functional testing at the six month ± one month time point postoperatively, and had a minimum of two year post-operative follow-up were included in this study. Functional testing included vertical jump, single leg hop, and triple leg hop. Functional testing is represented as a measure of limb symmetry and was calculated as the involved limb divided by the uninvolved limb providing a percentage relative to the uninvolved limb. Statistical analysis was performed to determine the significance of functional test limb symmetries between those with and without a secondary tear by sex, then by age. Unpaired T-tests with an alpha level less than 0.05 was performed with JMP 13 (SAS Institute Inc., Cary, NC). Group distributions as well as effect sizes were calculated. Results: 335 patients with a mean age of 25 (SD 9.76) at an average time of 9.05 years (SD 3.54) of follow-up after ACL reconstruction met inclusion criteria and underwent statistical analysis (females= 150, male= 185). Of the cohort, 53 patients (18%) experienced second tears (female= 26, male= 27) at an average time of 44.19 months (6.03- 168.4) following ACL reconstruction with 34 occurring on the contralateral side and 19 on the ipsilateral side. Results at six month post ACL reconstruction indicate a significant difference between those who experienced a second ACL injury and those who didn’t with respect to single hop limb symmetry (95% ±7% vs.90% ± 12%, P<0.01). Triple hop limb symmetry was also significantly different between those who suffered a second ACL tear and those who did not (94% ± 6% vs. 90% ±11%, P<0.01). No significant differences were found in limb symmetry of vertical jump. When data was analyzed by sex, significant differences were found in females in the single hop limb symmetry (96% ± 8%, vs. 89% ± 14%, P<0.05) as well as triple hop limb symmetry (95% ± 5% vs. 90% ± 12%, P< 0.05). No significant differences were found in vertical jump for neither females nor males. No significant differences were found when data was categorized by age or sex and age. Conclusion: Overall, at an average of 9.05 years follow-up, 18% of a young and active population of primary ACL reconstructions had a second ACL injury. Contralateral ACL injuries were observed at an increased frequency relative to subsequent ipsilateral ACL tears. Patients with greater limb symmetry on single hop or triple hop functional testing at 6 months are at an increased risk for second ACL tears. When functional testing is used for return-to-sport decisions, physicians should caution patients about the risk of subsequent ACL injury for high performing patients.

Strength and Function Across Maturational Levels in Young Athletes at the Time of Return to Sport After ACL Reconstruction.

The impact of maturation on lower extremity strength and function after anterior cruciate ligament reconstruction (ACLR) may help guide future studies of age-specific rehabilitation. Pediatric ACLR patients would demonstrate higher thigh strength symmetry and knee-related function at return to sport (RTS) compared with adolescent and young adult participants who underwent traditional ACLR. Prospective cohort study. Level 2. A total of 144 young athletes at the time of RTS clearance post-ACLR were classified into 3 maturational groups (pediatric, n = 16 with physeal-sparing ACLR [mean age = 12.3 years; range = 9.2-14.6 years]; adolescent, n = 113 [mean age = 16.5 years; range = 14.1-19.8 years]; young adult, n = 15 [mean age = 22.0 years; range = 20.5-24.9 years]). Quadriceps and hamstring strength were measured using an electromechanical dynamometer. Knee-related function was measured using the International Knee Documentation Committee (IKDC) subjective form and single-leg hop tests. The Limb symmetry Index (LSI) was used in calculations for hop and strength tests. Group differences were compared with Kruskal-Wallis tests and Mann-Whitney U post hoc tests. Proportions of participants meeting literature-recommended RTS criterion cutoffs were compared among the groups using chi-square tests. The pediatric group demonstrated higher quadriceps LSI (P = 0.01), IKDC scores (P < 0.01), single-hop LSI (P < 0.01), and crossover-hop LSI (P = 0.02) compared with the young adult group. In addition, the pediatric group demonstrated higher IKDC scores (P < 0.01) and single-hop LSI (P = 0.02) compared with the adolescent group. The adolescent group demonstrated higher IKDC scores (P < 0.01), single-hop LSI (P = 0.02), and crossover-hop LSI (P = 0.03) compared with the young adult group. The proportions of participants meeting all RTS criterion cutoffs were highest in the pediatric group and lowest in the young adult group (P = 0.03). Young athletes at RTS clearance after pediatric ACLR demonstrated higher quadriceps strength symmetry and knee-related function than adolescents and young adults after traditional ACLR. These findings demonstrate the need for further study regarding the impact of these group differences on longitudinal outcomes after ACLR, including successful RTS and risk of second ACL injury.

Poor Pelvic Control During A Knee Lift Test Is Associated With Increased Risk Of Knee Injuries

PURPOSE: To investigate whether deficits in stance leg, hip and pelvic stability during a standing knee lift test are associated with increased risk of non-contact knee and ankle injuries in youth team sports. METHODS: At baseline, 263 basketball and floorball players (age range 12–21 y.) participated in a standing knee lift test using 3-dimensional motion analysis. The test was a modified version of the Trendelenburg test to assess stance leg and hip stability. Two trials per leg were recorded from each participant and mean value was used in the analysis. The biomechanical variables calculated were peak anterior pelvic tilt angle (APT) and peak lateral pelvic drop angle (LPD). The APT and LPD were categorized into two groups using the median of the cohort: low group (values less than median value) and high group (values larger than median). All new non-contact knee and ankle injuries, as well as match and training exposure, were then recorded for 12 months. Cox regression models were used to calculate hazard ratios (HRs) and 95% CIs. RESULTS: A total of 16 new non-contact knee injuries (of which eight were ACL ruptures, all affecting female players) and 36 new non-contact ankle injuries were registered during the study period. Athletes displaying high lateral pelvic drop angles were at increased risk of knee injuries (adjusted HR for high versus low group 4.22; 95% CI 1.34–13.3). A borderline significant (p=0.05) association was found between high lateral pelvic drop angles and ACL injury risk in female athletes (adjusted HR for high versus low group 8.14; 95% CI 0.97–68.6). No potential ankle injury risk factors were found. A receiver operating characteristic curve analysis for the LPD and knee injuries showed an area under the curve of 0.60, which indicates poor combined sensitivity and specificity of the test. CONCLUSIONS: Poor pelvic control, with increased lateral pelvic drop, is associated with increased risk of non-contact knee injuries among young team sport players. However, the knee lift test cannot predict non-contact knee injuries in youth team sports. Supported by the Finnish Ministry of Education and Culture, and Competitive State Research Financing of the Expert Responsibility area of Tampere University Hospital (Grant 9S047).

Effects Of Stroboscopic Vision On Reactive Strength Index Scores In Female Ncaa Division I Volleyball Players.

It is believed that ACL injury risk is multifaceted and includes structural, biomechanical, and cognitive factors. Recently, it is observed that overreliance on exteroception (visual stimuli) following ACL rehabilitation may increase the risk of re-rupture. There may be utility in using stroboscopic vision as an enhancement to plyometric movements and neuromuscular ACL-prevention programs. PURPOSE: To evaluate the effects of stroboscopic vision on Reactive Strength Index (RSI) scores in female NCAA Division I volleyball players. METHODS: Thirteen female NCAA Division I volleyball players performed three trials of depth jumping across five conditions: (1) 0.38 m - no visual restriction, (2) 0.53 m - no visual restriction, (3) 0.69 m - no visual restriction, (4) 0.38 m - high-frequency stroboscopic vision (H-f), and (5) 0.38 m - low-frequency stroboscopic vision (L-f). For all trials, the RSI, rebound jump height (RJH; m), and ground contact time (GCT; s) were computed from vertical ground reaction force data acquired via a tri-axial force platform. To evaluate the statistical significance of results, a Multivariate General Linear Model Analysis of Variance (GLM ANOVA) was performed using RSI, RJH (m), and GCT (s) as dependent measures. The five depth jump conditions were included as levels within a single condition factor. Statistical significance was set at an alpha level of 0.05. RESULTS: Main effects of depth jump condition were observed for RSI and GCT (s) (p = 0.001), but not for RJH (m) (p = 0.101). Post-hoc comparisons revealed that RSI scores were lower for stroboscopic conditions (H-f: 0.75 ± 0.16; L-f: 0.72 ± 0.16) versus no visual restriction (0.38 m: 0.80 ± 0.17; 0.53 m: 0.79 ± 0.17; 0.69 m: 0.79 ± 0.16). Post-hoc comparisons revealed that GCT (s) was greater for stroboscopic conditions (H-f: 0.47 ± 0.07 s; L-f: 0.49 ± 0.07 s) versus no visual restriction (0.38 m: 0.46 ± 0.07 s; 0.53 m: 0.45 ± 0.07 s; 0.69 m: 0.45 ± 0.07 s). CONCLUSION: Integrating stroboscopic vision into the depth jump movement reduced RSI scores in a sample of female NCAA Division I volleyball players, which was attributable to longer GCTs (s). The results suggest that adding stroboscopic vision to plyometric movements may increase the difficulty of the task from either a cognitive or biophysical perspective.

Radiographic evaluation of posterior tibial slope in ACL deficient Indian patients

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; There are several studies which have investigated various osseous morphologic characteristics as they relate to ACL injury. Tibial slope, notch width, and notch width index are some. However, there does not appear to be consensus across studies. The aim of this study was to validate association between posterior tibial slope (PTS) and ACL injury in an ACL deficient knee of Indian patients.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; This retrospective cum prospective study was done at a tertiary hospital from June 2017 to May 2018. 40 patients were included. Inclusion criteria were documented evidence of ACL tear to the affected knee; no history of osteoarthritis; no history of rheumatoid arthritis; patients voluntarily consented for the use of their radiographs for the study. The assessment was completed with a true lateral view of the knee with full length leg and ankle. The functional tibial slope as described by Julliard et al was used to determine the PTS. The mean and standard deviation (SD) for medial PTS were measured. Demographic data like age, sex were collected and entered into a database.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; 95% of patients were male. Mean age was 29.25. The mean PTS was 13.037 which is reasonably high as compared to normal while the standard deviation was 4.487 reflecting large amount of variation.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; Increased posterior tibial slope can be concluded as a significant risk factor in ACL injury which corroborates the findings of various previously published studies. The findings presented may help identify patients who are at greater risk of ACL injury. &lt;/p&gt;

Sex differences in knee extension rate of torque development and patient-reported function among individuals with anterior cruciate ligament reconstruction

Purpose: Men and women with anterior cruciate ligament reconstruction (ACLR) continue to receive similar rehabilitative care despite evidence that women are more likely to experience poor clinical outcomes, a more than 4 times greater risk for second ACL injury, and a 45% greater risk of developing post-traumatic osteoarthritis (PTOA) when compared to men of similar age and activity level. While the mechanism of PTOA development following ACLR remains unclear, altered knee joint loading characteristics during activities of daily living have been hypothesized as potential contributors to the early stages of this process. Recently, knee extension strength, knee extension rate of torque development (RTD), and patient-reported psychological readiness have been shown to influence lower extremity loading characteristics, but it remains unclear if sex differences are present in these outcome measures. If present, this would help to explain the disparate outcomes experienced by men and women with ACLR. Identification of modifiable outcomes such as knee extension strength characteristics and psychological readiness early after ACLR may provide clinicians with feasible targets for patient-centered intervention within this population. Therefore, the primary purpose of this study was to determine the effect of participant sex on measures of knee extension strength characteristics and psychological readiness among men and women within the first year after ACLR. Methods: Thirty-three women (age= 19.0±4.3 years, time since surgery= 6.8±1.6 months) and 29 men (age= 21.4±6.8 years, time since surgery= 7.4±2.3 months) with a history of ACLR were enrolled in an on-going cohort study from which these data were obtained. Participants were included if they were between the ages of 13 and 40, had a history of ACLR, were within 2 weeks of their final clinical visit to their orthopaedic surgeon, and had not yet returned to sport participation. Participants completed a detailed health history, the ACL Return to Sport After Injury (ACL-RSI) scale, and the International Knee Documentation Committee (IKDC) subjective knee evaluation form after which they performed a bilateral assessment of knee extension maximal voluntary isometric contraction (MVIC) strength using a multimodal dynamometer. After a standardized familiarization protocol, participants completed 3 knee extension MVIC trials during which they were instructed to “kick out as hard and fast as possible” while being provided visual feedback on a nearby monitor. Peak knee extension MVIC torque (Nm) was documented from each trial and normalized to body mass (Nm/kg). Additionally, RTD100 was calculated as the slope of the torque x time curve from contraction initiation to 100ms following contraction initiation (Nm*kg-1*s-1) and RTD200 was calculated as the slope from of the torque x time curve from 100ms to 200ms after contraction initiation (Nm*kg-1*s-1). Participant demographics were compared between the sexes using independent samples t-tests while patient-reported outcome measures and knee extension strength characteristics were compared using ANCOVA with months since surgery as a covariate. Results: There were no significant sex differences in age (p= 0.10), time since surgery (p=0.65), patient-reported knee function (Female= 80.9±11.2, Male= 85.1±9.2; p= 0.11), or psychological readiness for sport (Female= 69.3±23.8, Male= 62.8±24.5; p= 0.25) among participants with ACLR. Female participants displayed lesser involved limb (Female= 1.99±0.53 Nm/kg, Male= 2.71±0.71 Nm/kg; p < 0.001) and contralateral limb (Female= 2.62±0.59 Nm/kg, 3.17±0.52 Nm/kg; p < 0.001) knee extension MVIC torque as well as lesser involved limb knee extension RTD100 (Female= 6.41±2.39 Nm*kg-1*s-1, Male= 8.24±3.17 Nm*kg-1*s-1; p= 0.01) and involved limb RTD200 (Female= 6.62±2.21 Nm*kg-1*s-1, Male= 9.43±3.40 Nm*kg-1*s-1; p < 0.001; Figure 1) when compared to male participants. Conclusions: Our findings indicate that women experience larger magnitude deficits in involved limb knee extension strength and RTD when compared to men during the terminal phase of clinical care following ACLR. This is despite no significant differences in patient-reported knee function or psychological readiness between the sexes. While not perceived as a functional limitation among women with ACLR, persistent quadriceps dysfunction and the associated alterations in lower extremity loading characteristics may set the stage for early degenerative changes in knee joint articular cartilage structure. Early identification of sex-based disparities in modifiable functional outcomes (knee extension strength and RTD) following ACLR may provide clinicians with goals for patient-centered impairment-based rehabilitation strategies to improve lower extremity loading characteristics which are implicated in the early progression of PTOA.

EFFECT OF STATIC ANATOMIC ALIGNMENT ON DYNAMIC LIMB VALGUS DURING SIDE-STEP CUTTING IN UNINJURED ADOLESCENT ATHLETES

BACKGROUND Dynamic limb valgus, combining hip adduction and internal rotation with knee abduction posture and moments, has been implicated in ACL injury. However, the contribution of static lower extremity alignment to dynamic limb valgus is unknown. This study assessed the relationships among lower extremity static alignment and dynamic kinematics and kinetics during side-step cutting in uninjured adolescent athletes. METHODS This prospective study included 88 limbs from 44 uninjured athletes aged 8-15 years (mean 12.3, SD 2.3; 19 (44%) female) who were evaluated during an anticipated 45° side-step cut. 3D lower extremity kinematics and kinetics from a custom 6 degree of freedom model were assessed while standing and during the loading phase of the cut from initial contact to peak knee flexion; 2-3 trials per limb were averaged for analysis. Femoral anteversion was measured for each limb with the participant lying prone. Relationships among static and dynamic measures were investigated using correlation and multiple linear regression. RESULTS In terms of static alignment, more static hip internal rotation and more static knee external rotation (tibia external relative to femur) were associated with more internal hip rotation and external knee rotation dynamically during cutting (r=0.34, p=0.001) (Table 1). Static hip adduction was also related to more external hip rotation and less hip flexion dynamically (p=0.24, p=0.02). More static knee abduction, external hip rotation and hip adduction were associated with higher average knee abduction angles during cutting (r=0.25, p=0.02). However, only static external knee rotation was associated with higher dynamic knee abduction moments (r=0.48, p&lt;0.0001) (Figure 1). During cutting, positive associations were observed between hip flexion, knee flexion, and hip internal rotation (r=0.24, p=0.03). Knee adduction angles were related to more hip flexion, internal hip rotation, and knee external rotation (r=0.25, p=0.02). Additionally, lower peak knee flexion was associated with higher peak ground reaction force and more external knee rotation (r=0.24, p=0.02). Both simple correlation and multiple regression analysis indicated that higher knee abduction moments were related dynamically to higher knee abduction angles, greater knee external rotation, higher hip abduction angles, and greater hip internal rotation (R2=0.72, p&lt;0.001). After considering dynamic metrics, no static measure remained significantly related to knee abduction moments. CONCLUSION/SIGNIFICANCE Static knee rotation was the only anatomic alignment measure associated with knee abduction moments during side-step cutting in uninjured adolescent athletes. Knee abduction moments were influenced more by dynamic posture than static alignment. As knee abduction moments have been implicated in ACL injury, this study supports the notion of dynamic limb valgus, specifically increased knee abduction and hip internal rotation, relating to ACL injury. Motion analysis can be used to identify these risky biomechanical patterns, and neuromuscular training can be used to correct them. Since knee abduction moments are primarily determined by dynamic posture, neuromuscular training can be used to reduce these moments and ACL injury risk. [Figure: see text][Table: see text]

SEX DIFFERENCES IN QUADRICEPS STRENGTH AMONG ADOLESCENTS WITHIN 1 YEAR OF ACL RECONSTRUCTION

Background Female patients with ACLR are 40% less likely to return to preinjury levels of sport after subsequent ACLR when compared to their male counterparts. Additionally, 24-30% of young female athletes who do return to sport will go on to experience a second ACL injury to the ipsilateral or contralateral knee within 2 years of ACLR. Despite these findings, sex-based differences in clinical outcomes following ACLR are not currently well understood within the adolescent population. Involved limb knee extension weakness, contralateral limb knee extension weakness, and between limb strength asymmetry persist months to years following ACLR among adolescent patients. Improvements in unilateral and symmetry-based measures of knee extension strength during and after the rehabilitation process have been linked to improved patient-reported knee related function, lower extremity functional performance, and decreased risk of subsequent ACL injury among individuals with recent ACLR. Currently, there is a lack of evidence describing the role that sex plays in persistent quadriceps weakness. Therefore, the purpose of this study was to investigate the effects of patient sex on unilateral and symmetry-based measures of knee extension strength, and patient-reported knee function among adolescent individuals with ACL reconstruction (ACLR) within the first year after surgery. Methods: Fifty-two male participants (age = 16.8±1.3 years, BMI = 25.6±5.6 kg/m2, time since surgery = 6.3±1.4 months) and 66 female participants (age = 16.7±1.4 years, BMI = 23.9±3.9kg/m2, time since surgery = 6.8±1.7 months) with unilateral ACLR, 4-12 months prior to enrollment were recruited for this multi-site cross-sectional study. Participants completed bilateral knee extension maximal voluntary isometric contraction (MVIC) torque assessments using a multimodal dynamometer with continuous verbal encouragement from the tester and visual feedback on a nearby monitor. Peak knee extension MVIC torque was identified for each of 3 trials and was normalized to body mass (Nm/kg). Limb symmetry indices were also calculated by dividing the MVIC torque obtained for the involved limb by the MVIC torque obtained for the contralateral limb. Participants also completed the International Knee Documentation Committee (IKDC) Subjective Knee Form to assess patient-reported knee function. Sex-based comparisons of quadriceps strength outcomes and IKDC score were made using separate ANCOVAs where time since surgery was utilized as a covariate. Cohen’s d effect sizes and 95% confidence intervals (CI95) were calculated to assess the magnitude of sex difference for all outcome measures. Odds ratios and CI95 were also calculated to assess the odds of an adolescent female achieving clinical threshold for acceptable involved limb quadriceps strength (MVIC = 3.0 Nm/kg), quadriceps limb symmetry (LSI = 90.0%), and patient-reported knee function (IKDC = 90.0). Results: The involved limb (male = 2.08±0.95 Nm/kg, female = 1.69±0.63 Nm/kg, p = 0.01, d = -0.50, CI95 = -0.13 to -0.87) and contralateral limbs (male = 2.75±0.75 Nm/kg, female = 2.31±0.64 Nm/kg, p = 0.001, d = -0.64, CI95 = -0.26 to -1.01) of male participants were stronger when compared to female participants but limb symmetry (male = 74.7±22.6%, female = 74.7±24.6%, p = 0.95, d = 0.00, CI95 = 0.36 to -0.36) and IKDC score (male = 84.4±16.1, female = 79.4±13.7, p = 0.08, d = -0.34, CI95 = 0.03 to -0.71) was not significantly different between the sexes. Male participants were 5.66 times (CI95 = 1.46 to 21.87) more likely to meet the clinical threshold for acceptable involved limb quadriceps strength and 3.52 times (CI95 = 1.54 to 8.05) more likely to report acceptable knee related function. The likelihood of achieving clinically acceptable limb symmetry was not significantly different between the sexes (OR = 1.17, CI95 = 0.48 to 2.83). Conclusion/Significance: Adolescent female patients may experience significantly worse involved limb and contralateral quadriceps weakness when compared to adolescent male patients despite displaying equally poor limb symmetry and patient-reported knee function during the first 12 month following surgery. Given the importance of involved limb quadriceps strength as a predictor of patient-reported function and movement quality, clinicians should incorporate patient education regarding the importance of quadriceps function and recommend progressive lower extremity loading when implementing patient-centered rehabilitation plans that promote safe return to healthy levels of physical activity following ACLR.

QUADRICEPS STRENGTH CHANGES ACROSS THE CONTINUUM OF CARE FOLLOWING ANTERIOR CRUCIATE LIGAMENT INJURY IN ADOLESCENT MALES AND FEMALES

Background: Deficits in quadriceps strength have consistently been observed following anterior cruciate ligament reconstruction (ACL-R) and this deficit is frequently accompanied by altered lower extremity biomechanics that could increase risk of a second ACL injury. Regaining strength is a major focus for rehabilitation; however, it is unclear how quadriceps strength of both the involved (INV) and uninvolved (UnINV) limbs change across the continuum of care. Therefore, the purpose of this study was to examine quadriceps strength from the pre-operative time point until time of return to sport (RTS) in adolescent males and females. Methods: Cohort study design was used. A total of 60 adolescents participated (Males: N = 26, Age = 15.96? 1.23 yr, Ht = 177.14? 8.13 cm, Mass = 76.23? 1.23Kg; Females: N = 34, Age = 15.32? 1.12 yr, Ht = 163.11? 6.30 cm, Mass = 61.39? 7.38Kg) in the study. Participants were included in the study if they: 1) had a primary ACL-R, 2) participated in organized high-risk sports with an intention to return to sports, 3) completed assessments at the pre-operative timepoint (Pre), 12-weeks after surgery (12wk), and at time of RTS, and 4) completed the post-operative rehabilitation program. Five isokinetic repetitions of quadriceps strength (QUADS) of the INV and UnINV limbs were assessed at Pre, 12wk, and RTS, using a Biodex dynamometer (60?/sec). Peak strength was normalized to body weight (BW-1) and averaged across 5 trials. Separate 2 (limb – INV, UnINV) X 3 (time – Pre, 12wk, RTS) repeated measures of ANOVA were performed. With significant interaction, paired t-tests were performed to compare strength between each time point in each limb and between INV and UnINV limbs at each time point. Results: There were significant side by time interactions in adolescent females (F = 6.49, p = 0.002) and males (F=16.57, p &lt; 0.001). Post hoc tests revealed that adolescent females had greater INV RTS QUADS than INV PRE QUADS (p= 0.001) and INV 12wk QUADS (p &lt; 0.001), but no significant differences were observed between any time points in the UnINV limb. Adolescent males demonstrated decreased INV 12wk QUADS compared with INV Pre QUADS (p = 0.032), greater INV RTS QUADS than INV 12wk QUADS (p &lt; 0.001). UnINV 12wk QUADS was lower than UnINV Pre QUADS (p &lt; 0.037) and UnINV RTS QUADS was greater than UnINV Pre QUADS (p &lt; 0.002). In both female and male participants, INV QUADS was significantly less than UnINV QUADS at Pre, 12wk, and RTS time points (Females: p &lt; 0.001, p=0.007, p &lt; 0.001, respectively; Males: p &lt; 0.001, p &lt; 0.001, p &lt; 0.001, respectively). Conclusion/Significance: Quadriceps strength changes differently in adolescent females and males in both the INV and UnINV limbs across the continuum of care following ACL injury. While no changes were observed in UnINV QUADS over time, adolescent females improved INV QUADS from 12wk to RTS without changes in QUADS from Pre to 12wk. Although INV RTS QUADS was greater than INV Pre QUADS, INV RTS QUADS was 27% lower than RTS UnINV QUADS. Since UnINV QUADS is expected to be decreased due to reduced activity compared to that of pre-injury, strengthening the UnINV limb in addition to the INV limb appears to be a priority during rehabilitation. For adolescent males, INV QUADS decreased from Pre to 12wk and returned near to baseline at time of RTS, but not enough to surpass the Pre QUADS. Perhaps, minimizing the reduction of QUADS between the Pre and 12wk time points through an increase of exercise load during the early stages of rehabilitation may help to improve these deficits. Unlike female adolescents, adolescent males improved UnINV strength over time. This improvement may be a compensation of the decreased QUADS of the INV limb as significant deficits of QUADS were present at each time point. [Table: see text][Table: see text]

Concurrent changes in eccentric hamstring strength and knee joint kinematics induced by soccer-specific fatigue

ObjectivesTo investigate the influence of soccer-specific fatigue on concurrent changes in knee joint kinematics and hamstring strength, given the increased risk of injury during the latter stages of match-play and the prevalence of knee joint and hamstring muscular injury. DesignRepeated measures, randomized order trials. SettingLaboratory. ParticipantsTen male professional soccer players. Main outcome measuresReactive inversion, eversion and neutral hop tasks were completed at 15 min intervals during a soccer-specific protocol, with touchdown knee joint kinematics in the frontal and sagittal planes calculated at 200 Hz. In a separate trial, players completed maximal eccentric knee flexions at 160°·s−1 (reflecting average knee angular velocity in the functional task) at 15 min intervals, quantifying peak torque. ResultsAll trials were characterized by knee varus at touchdown, with ∼4° greater mal-alignment elicited over the final 15 min of the protocol (P ≤ 0.05). Peak eccentric hamstring strength was significantly (P = 0.045) reduced throughout the 2nd half. ConclusionsThe coincident impairment of eccentric hamstring strength and increased knee varus at touchdown predisposes the player to injury, supporting epidemiological observations. Knee varus in these elite male players is in marked contrast to the valgus associated with ACL injury risk in female players.

Is ski boot sole abrasion a potential ACL injury risk factor for male and female recreational skiers?

ObjectivesTo evaluate the potential impact of ski boot sole abrasion on the ACL injury risk of recreational skiers.MethodsDuring the past two winter seasons 2016/17 and 2017/18, this retrospective case‐control study was conducted in one Austrian ski area. Among a cohort of 148 ACL‐injured (51.4% females) and 455 uninjured recreational skiers (43.3% females), age, sex, height, weight, and self‐reported skill level were collected by questionnaire, ski length and sidecut radius were notated and sole abrasion of the toe and heel piece of the ski boot was measured using a digital caliper.ResultsACL‐injured skiers showed a higher proportion of female (51.4% vs 43.3%, P < 0.001) and less skilled skiers (48.6% vs 20.9%, P < 0.001), and ski length to height ratio was higher (94.7 ± 3.7 vs 93.8 ± 5.0%, P = 0.019) compared to uninjured skiers. ACL‐injured skiers used ski boots of greater abrasion at the toe (4.8 ± 1.8 vs 2.4 ± 2.5 mm, P < 0.001) and heel piece (5.4 ± 1.8 vs 3.3 ± 2.3 mm, P < 0.001) compared to controls. Multivariate regression analysis revealed, beside female sex (OR 6.0, 95% CI, 3.1‐11.5, P < 0.001), lower skill level (OR 3.2, 95% CI, 1.9‐5.4, P < 0.001) and ski length to height ratio (OR 1.1, 95% CI, 1.0‐1.2, P < 0.001), sole abrasion at the toe (OR 1.8, 95% CI, 1.5‐2.1, P < 0.001) and heel piece (OR 1.4, 95% CI, 1.2‐1.6, P < 0.001) to be independently associated with an ACL injury among recreational alpine skiers.ConclusionsBased on the underlying findings, ski boot sole abrasion was found to be an independent risk factor and may contribute to an increased ACL injury risk.

The Effectiveness of Strengthening of Hip Extensors and Ankle Plantar Flexors in Early Post-Anterior Cruciate Ligament Reconstruction

AbstractBackground: Impaired hip strength may underlie abnormal movement patterns, suggesting that diminished hip strength may increase the risk of ACL injury and re injury after anterior cruciate ligament reconstruction.Aim of Study: To investigate the effect of strengthening of hip extensors and ankle plantar flexors in early Anterior Cruciate Ligament reconstruction on knee effusion, knee function, hip, knee and ankle muscles strength.Methods: The study was conducted on 30 male patients referred from the orthopedic surgeon with early post operative Anteior Cruciate Ligament reconstruction by hamstring graft or patellar tendon graft after acute injuries, their age range from 18-40 years and were randomly assigned into two groups. Group A: Consisted of fifteen patients who had received open kinetic chain strengthening exercises for hip extensors and ankle plantar flexors in addition to the traditional accelerated program. Group B: Consisted of fifteen patients who had received the traditional accelerated program for 6 weeks (three sessions per week), effusion grading scale for effusion to assess effusion, handheld dynamometer to assess muscle power, Westen Ontario and MACmaster universities score and Time Up and Go test for functional assessment.Results: There was no significant difference between both groups for, hip extensors force and (TUG at 3 weeks). There was no significant difference between both groups for knee extensors torque between base line and 3 weeks and the same for plantar flexors force and WOMAC at 3 weeks. There was significant difference between both groups for knee extensors torque between 3 and 6 weeks, WOMAC at 6 weeks, TUG at 6 weeks and plantar flexors force between 3 and 6 weeks.Conclusion: Adding strengthening exercises of hip exten-sors and plantar flexors to the traditional accelerated protocol added more beneficial outcomes in relation to function after 6 weeks.

Fatigue affects quality of movement more in ACL-reconstructed soccer players than in healthy soccer players

PurposeAthletes who meet return to play (RTP) criteria after anterior cruciate ligament reconstruction (ACLR) rehabilitation still have a substantially increased risk of second ACL injury. One of the contributing factors to this increased risk could be that the RTP criteria are often not tested in an ecologically valid environment and in a fatigued state. The purpose of this cross-sectional case-control study was to investigate the influence of neuromuscular fatigue on both movement quantity and quality in fully-rehabilitated soccer players after ACLR and to compare them with healthy soccer players.MethodsACL-reconstructed soccer players (n = 14) and healthy soccer players (n = 19) participated in the study and were matched by playing level and training hours. RTP measurements were performed on the soccer field, in both a non-fatigued and fatigued state. The RTP measurements focussed on both movement quantity (hop tests) and quality [countermovement jump with a Landing Error Scoring System (LESS) score].ResultsMovement quantity did not differ between ACL-reconstructed and healthy soccer players, both expressed in absolute values and the LSI-D/ND (calculated as dominant/non-dominant*100%). However, movement quality decreased more in the ACL-reconstructed soccer players in the fatigued state compared to the non-fatigued state.ConclusionsIdeally, RTP measurements should focus on movement quality and should be conducted on the soccer field in a fatigued state, creating an ecologically valid environment. The LSI-D/ND can be used as an outcome parameter for RTP measurements of movement quantity and should be at least 95%.Level of evidenceTherapeutic, Level III.

Gender specific ACL loading patterns during the fencing lunge: Implications for ACL injury risk

Summary Purpose Determine whether gender differences in ACL loading linked to the aetiology of injures are evident during the fencing lunge. Materials and methods ACL loading was obtained from ten male and ten female fencers using an eight-camera 3D motion capture system and force platform data as they completed simulated lunges. Gender differences in ACL loading parameters were examined using independent samples t tests. Results Peak ACL load and instantaneous rate of loading were significantly larger in female fencers (6.21 N/kg & 511.18 N/kg/s) in comparison to males (4.04 N/kg & 378.77 N/kg/s). Conclusions This investigation indicates that female fencers may be at increased risk from ACL pathologies. Future analyses should seek to investigate and implement strategies aimed at reducing ACL loading in female fencers.

Incidence and Radiological Predictors of Concomitant Meniscal and Cruciate Ligament Injuries in Operative Tibial Plateau Fractures: A Prospective Diagnostic Study

The aim of this prospective study was to determine the incidence of meniscal and cruciate ligament injuries in operative tibial plateau fractures detected using knee arthroscopy, and to identify the radiological predictors observed on CT images. From January 2016 to February 2017, a total of 102 closed tibial plateau fractures were enrolled in this prospective protocol. Each patient underwent arthroscopic examination following the tibial plateau internal fixation. Univariate analysis and multivariable logistic regression were used to assess the association between imaging parameters and soft-tissue injuries. The menisci were traumatically injured in 52.9% of subjects (54 of 102) and the cruciate ligaments injured in 22.5% (23 of 102). Significantly higher injury rates for bucket-handle meniscal tears were observed in Schatzker type VI fractures (P = 0.04). Greater risk of lateral meniscus injury was observed in patients with >6.3 mm of lateral joint depression. Greater risk of ACL injury when the volumetric lateral joint depression was ≤209.5 mm2 and/or with >5.7 mm lateral joint widening. Associated meniscal and ligament injuries were commonly seen among operative tibial plateau fractures. Preoperative CT measurements might help predict a higher risk of meniscus and ACL injury, providing guidance to the surgeon to look for and to be prepared to treat such injuries.

Does brain functional connectivity contribute to musculoskeletal injury? A preliminary prospective analysis of a neural biomarker of ACL injury risk

ObjectivesWe aimed to present a unique prospective neurological dataset for participants who experienced an ACL injury. DesignProspective longitudinal case-control. MethodsHigh school female soccer athletes were evaluated using functional magnetic resonance imaging to capture resting-state brain connectivity prior to their competitive season. Two of these athletes later experienced an ACL injury (ACLI). We matched these ACLI participants with eight teammates who did not go on to sustain an ACL injury (uninjured controls, Con) based on age, grade, sex, height, and weight to examine differences in preseason connectivity. Knee-motor regions of interest (ROIs) were created based on previously published data from which five specific areas were selected as seeds for analysis. Independent-samples t-tests with a false discovery rate correction for multiple comparisons determined differences in connectivity between the ACLI and Con. ResultsThere was significantly greater connectivity between the left primary sensory cortex (a brain region responsible for proprioception) and the right posterior lobe of the cerebellum (a brain region responsible for balance and coordination) for the Con relative to ACLI, t (8)=4.53, p=0.03 (false discovery rate corrected). ConclusionsThese preliminary data indicate that those who do not later sustain an ACL injury exhibit a stronger functional connection between a cortical sensory-motor region and a cerebellar region responsible for balance and coordination. These findings may help to guide development of brain-driven biofeedback training that optimizes and promotes adaptive neuroplasticity to reduce motor coordination errors and injury risk.

Changes in Injury Risk Mechanisms After Soccer-Specific Fatigue in Male Youth Soccer Players

The aim of this study was to examine the acute effects of soccer specific fatigue on muscular and neuromuscular function in male youth soccer players. Elite soccer players (n = 20; age 15.7 ± 0.5 y; body height 177.75 ± 6.61 cm; body mass 67.28 ± 8.29 kg) were measured before and after soccer specific exercise (SAFT90). The reactive strength index (RSI) was determined by a drop jump test, leg stiffness (LS) by a 20 sub-maximal two-legged hopping test, and a functional hamstring to quadriceps strength ratio from isokinetic concentric and eccentric strength of the dominant and non-dominant leg (measured at angular velocities of 1.05 rad · s−1 and 3.14 rad · s−1). Metabolic response to the SAFT90 was determined by blood lactate and perceived exertion was assessed by the Borg scale. After simulated match play, a significant decrease in absolute LS (t = 4.411; p < 0.001; ω2 = 0.48) and relative LS (t = 4.326; p < 0.001; ω2 = 0.49) was observed and the RSI increased significantly (t = 3.806; p = 0.001; ω2 = 0.40). A reduction in LS found after the SAFT90 indicates possible reduction in dynamic knee stabilization. However, if we consider the changes in other observed variables, the present study did not clearly confirm that fatigue induced by a soccer specific protocol increased the risk of ACL and hamstring injury. This may be attributed to the simulated rather than actual match play used in the present study.

Investigation of the Effects of High-Intensity, Intermittent Exercise and Unanticipation on Trunk and Lower Limb Biomechanics During a Side-Cutting Maneuver Using Statistical Parametric Mapping

Whyte, EF, Richter, C, O'Connor, S, and Moran, KA. Investigation of the effects of high-intensity, intermittent exercise and unanticipation on trunk and lower limb biomechanics during a side-cutting maneuver using statistical parametric mapping. J Strength Cond Res 32(6): 1583-1593, 2018-Anterior cruciate ligament (ACL) injuries frequently occur during side-cutting maneuvers when fatigued or reacting to the sporting environment. Trunk and hip biomechanics are proposed to influence ACL loading during these activities. However, the effects of fatigue and unanticipation on the biomechanics of the kinetic chain may be limited by traditional discrete point analysis. We recruited 28 male, varsity, Gaelic footballers (21.7 ± 2.2 years; 178.7 ± 14.6 m; 81.8 ± 11.4 kg) to perform anticipated and unanticipated side-cutting maneuvers before and after a high-intensity, intermittent exercise protocol (HIIP). Statistical parametric mapping (repeated-measures analysis of varience) identified differences in phases of trunk and stance leg biomechanics during weight acceptance. Unanticipation resulted in less trunk flexion (p < 0.001) and greater side flexion away from the direction of cut (p < 0.001). This led to smaller (internal) knee flexor and greater (internal) knee extensor (p = 0.002-0.007), hip adductor (p = 0.005), and hip external rotator (p = 0.007) moments. The HIIP resulted in increased trunk flexion (p < 0.001) and side flexion away from the direction of cut (p = 0.038), resulting in smaller (internal) knee extensor moments (p = 0.006). One interaction effect was noted demonstrating greater hip extensor moments in the unanticipated condition post-HIIP (p = 0.025). Results demonstrate that unanticipation resulted in trunk kinematics considered an ACL injury risk factor. A subsequent increase in frontal and transverse plane hip loading and sagittal plane knee loading was observed, which may increase ACL strain. Conversely, HIIP-induced trunk kinematic alterations resulted in reduced sagittal plane knee and subsequent ACL loading. Therefore, adequate hip and knee control is important during unanticipated side-cutting maneuvers.

Muscle Activation During ACL Injury Risk Movements in Young Female Athletes: A Narrative Review.

Young, adolescent female athletes are at particular high risk of sustaining a non-contact anterior cruciate ligament (ACL) injury during sport. Through the last decades much attention has been directed toward various anatomical and biomechanical risk factors for non-contact ACL injury, and important information have been retrieved about the influence of external loading factors on ACL injury risk during given sports-specific movements. However, much less attention has been given to the aspect of neuromuscular control during such movements and only sparse knowledge exists on the specific muscle activation patterns involved during specific risk conditions. Therefore, the aim of this narrative review was (1) to describe anatomical aspects, strength aspects and biomechanical aspects relevant for the understanding of ACL non-contact injury mechanisms in young female athletes, and (2) to review the existing literature on lower limb muscle activation in relation to risk of non-contact ACL-injury and prevention of ACL injury in young female athletes. Studies investigating muscle activity patterns associated with sports-specific risk situations were identified, comprising cohort studies, intervention studies and prospective studies. Based on the retrieved studies, clear gender-specific differences in muscle activation and coordination were identified demonstrating elevated quadriceps activity and reduced hamstring activity in young female athletes compared to their male counterparts, and suggesting young female athletes to be at elevated risk of non-contact ACL injury. Only few studies (n = 6) examined the effect of preventive exercise-based intervention protocols on lower limb muscle activation during sports-specific movements. A general trend toward enhanced hamstring activation was observed during selected injury risk situations (e.g., sidecutting and drop landings). Only a single study examined the association between muscle activation deficits and ACL injury risk, reporting that low medial hamstring activation and high vastus lateralis activation prior to landing was associated with an elevated incidence of ACL-injury. A majority of studies were performed in adult female athletes. The striking paucity of studies in adolescent female athletes emphasizes the need for increased research activities to examine of lower limb muscle activity in relation to non-contact ACL injury in this high-risk athlete population.

Implicit video feedback produces positive changes in landing mechanics

BackgroundImplicit (IF) and explicit (EF) feedback are two motor learning strategies demonstrated to alter movement patterns. There is conflicting evidence on which strategy produces better outcomes. The purpose of this study was to examine the effects of reduced IF and EF video feedback on lower extremity landing mechanics.MethodsThirty participants (24 ± 2 years, 1.7 ± 0.1 m, 70 ± 11 kg) were randomly assigned to three groups: IF (n = 10), EF (n = 10), and control (CG) (n = 10). They performed twelve box-drop jumps three times a week on the training sessions for six weeks. Only IF and EF groups received video feedback on the training sessions. IF was cued to focus their attention on the overall jump, while EF was cued to focus on position of their knees. 3D lower extremity biomechanics were tested on testing sessions with no feedback. All sessions were at least 24 h apart from another. Testing sessions included baseline testing (pretest), testing after 3 training sessions with 100% feedback (pst1), testing after 6 training sessions with 33.3% feedback (pst2), testing after 6 training sessions with 16.6% feedback (Pst3), and testing 1 month after with no feedback (retention – ret). ANOVA compared differences between groups and time at initial contact and peak for hip flexion (HF, °) and abduction angle (HA, °), hip abduction moment (HAM, Nm/kgm), knee flexion (KF, °) and abduction angle (KA, °), knee abduction moment (KAM, Nm/kgm) and VGRF (N) (p < 0.05).ResultsA significant main effect for group was found between IF and EF groups for HA (IF = − 6.7 ± 4; EF = − 9.4 ± 4.1) and KAM (IF = 0.05 ± 0.2; EF = − 0.07 ± 0.2) at initial contact, and peaks HA (IF = − 3.5 ± 4.5; EF = − 7.9 ± 4.7) and HAM (IF = 1.1 ± 0.6; EF = 0.9 ± 0.4). A significant main effect for time at initial contact for HF (pre = 32.4 ± 3.2; pst2 = 36.9 ± 3.2; pst3 = 37.9 ± 3.7; ret. = 34.1 ± 3.7), HAM (pre = 0.1 ± 0.1; pst1 = 0.04 ± 0.1; pst3 = 0.1 ± 0.01), KA (pre = 0.7 ± 1.1; pst1 = 0.2 ± 1.2; pst3 = 1.7 ± 1), and KAM (pre = 0.003 ± 0.1; pst3 = 0.01 ± 0.1) was found.Discussion/conclusionWe found that implicit feedback produced positive changes in landing mechanics while explicit feedback degraded motor learning. Our results indicate that implicit feedback should be used in programs to lower the ACL injury risk. We suggest that implicit feedback should be frequent in the beginning and not be reduced as much following the acquisition phase.