McPherson, April L.

Weaker hamstrings muscular forces and lower ratio of the hamstrings/quadriceps muscular forces in female athletes have been identified as modifiable risk factors for anterior cruciate ligament (ACL) injuries. However, sex differences in athletes’ ability to react to visual cues (Choice Visual‐Motor Reaction Time: VMRT) and to generate knee muscular forces (rate of force development: RFD) immediately following the visual cues were largely unknown. Therefore, the purpose of the study was to examine sex differences in Choice VMRT and RFD. A total of 50 high school basketball athletes (26F/24 M) participated in the study. Subjects sat in the knee dynamometer chair with their knee secured at 70° of knee flexion and performed knee extension or flexion maximum voluntary isometric contractions immediately after they saw the visual cue: “UP” or “DOWN” arrows, respectively. Choice VMRT was defined as the time between the visual cue and the initiation of muscular force development (>5Newtons). RFD was calculated by dividing the changes in forces over the changes in time at four time points (0–50/100/150/200 ms). Peak muscular forces and RFD were normalized to their body mass. Average of three trials in each direction (flexion and extension) in each leg was used for statistical analyses. Females had significantly slower Choice VMRT (p < 0.001–0.027) and lower knee extension RFD at 100 ms (p = 0.005). In addition, females had significantly higher knee flexion/extension ratio than males in late RFD (150 ms and 200 ms) (p < 0.004). The current study has provided additional sensorimotor characteristics of athletes and sexes in addition to their knee muscular characteristics.

Background: Many studies have investigated factors that predict a return to sport participation after anterior cruciate ligament (ACL) reconstruction, but it is unclear whether the same factors are associated with a return to preinjury level of sport performance. Purpose: To identify factors that contribute to an athlete’s return to preinjury level of performance after ACL reconstruction. Study Design: Cohort study; Level of evidence, 2. Methods: A cohort of 222 patients (132 male, 90 female) who had ACL reconstruction surgery and completed a 12-month postoperative assessment were followed out to a mean 3 years (range, 2-4 years) to determine whether they had returned to their self-reported preinjury levels of sport performance. Rates of return to preinjury performance were calculated. Measures that had been recorded at the 12-month postoperative review—demographic (age, sex), sport activity level (Marx Activity Rating Scale, return to competition sport), knee laxity, limb symmetry (single and triple crossover hop), subjective function/symptoms (International Knee Documentation Committee subjective), and psychological readiness (Anterior Cruciate Ligament Return to Sport After Injury scale)—were compared between patients who returned to their preinjury levels of performance and those who did not. Univariate and multivariate logistic regression models were also used to prospectively determine the association between these measures and return to preinjury level of sport performance. Results: A total of 135 (61%) patients reported that they had returned to their preinjury levels of performance, with return rates similar between males (59%) and females (63%) and between those who had returned to competition at 12 months (62%) and those who had not (60%). There was no significant age difference between patients who returned to their preinjury levels of sport performance and those who did not; however, higher psychological readiness ( P < .0001), greater limb symmetry ( P < .05), higher subjective knee scores ( P = .01), and a higher activity level ( P < .04) were all associated with a return to performance. In the multivariate model, psychological readiness was the only variable that remained a significant predictor (odds ratio = 1.03; 95% CI, 1.01-1.04; P < .0001). Conclusion: A majority of athletes who returned to sport after ACL reconstruction reported that their performance was comparable with preinjury. Having a greater psychological readiness to return during rehabilitation was the most significant predictor of a subsequent return to comparable performance.

Background: Lower psychological readiness to return to sport has been reported for younger patients (≤20 years) who go on to a second anterior cruciate ligament (ACL) injury. However, changes in psychological readiness and specific psychological responses associated with second injury have not been identified. Purpose/Hypothesis: To identify changes in psychological readiness over time associated with a second ACL injury. It was hypothesized that younger patients who suffered a second injury would have smaller changes in psychological readiness to return to sport when compared with those who did not have a second injury. Study Design: Case-control study; Level of evidence, 2. Methods: Patients ≤20 years old at the time of surgery who had a primary ACL reconstruction procedure between June 2014 and June 2016 were recruited for this study. The short version of the Anterior Cruciate Ligament Return to Sport After Injury (ACL-RSI) scale was completed by patients before their ACL reconstruction and repeated at 12 months after surgery to assess psychological readiness to return to sport. The primary outcome of interest was the relationship between the change in psychological readiness and second ACL injuries. Results: Among 115 young patients who returned to sport after ACL reconstruction, 21 (18%) experienced a second ACL injury. Injured patients did not show improvement in their ACL-RSI score between the preoperative assessment and 12-month time point (58.5 vs 60.8 points, P = .60) and had a significantly smaller change when compared with noninjured patients (9.2 vs 24.9 points, P = .01). When compared with the noninjured group, the injured group reported they were more nervous about playing sport, less confident in playing sport without concern for the knee, more frustrated with having to consider the knee with respect to sport, and more fearful of reinjuring the knee by playing sport ( P≤ .05). Conclusion: Injured patients exhibited less improvement in psychological readiness at a group level and reported different psychological characteristics with regard to return to sport at 12 months after ACL reconstruction as monitored by the ACL-RSI scale.

Background: Psychological responses after anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) have been identified as predictors of return to sport but have not been investigated in relation to further injury. Purpose/Hypothesis: To determine whether psychological readiness to return to sport is associated with second ACL injury. It was hypothesized a priori that at both preoperative and 12-month postoperative time points, patients who sustained a second ACL injury would have lower psychological readiness than patients who did not have a second injury. Study Design: Cohort study; Level of evidence, 2. Methods: Patients who had a primary ACLR procedure between June 2014 and June 2016 completed the ACL–Return to Sport after Injury (ACL-RSI) (short version) scale before their ACLR and repeated the scale at 12 months after surgery to assess psychological readiness to return to sport. Patients were followed for a minimum of 2 years (range, 2-4 years) after surgery to determine further injury. The primary outcome was the relationship between ACL-RSI scores and the incidence of second ACL injury. Results: In 329 patients who returned to sport after ACLR, 52 (16%) sustained a second ACL injury. No difference in psychological readiness was observed at the preoperative time point, but patients who sustained a second injury trended toward lower psychological readiness at 12 months compared with noninjured patients (60.9 vs 67.2 points; P = .11). Younger (≤20 years) patients with injury had significantly lower psychological readiness to return to sport than young noninjured patients (60.8 vs 71.5 points; P = .02), but no difference was found in older patients (60.9 vs 64.6 points; P = .58). In younger patients, receiver operating characteristic curve analysis revealed a cutoff score of 76.7 points with 90% sensitivity to identify younger patients who sustained a second ACL injury. Conclusion: Younger patients with lower psychological readiness are at higher risk for a second ACL injury after return to sport.

Background: Clinical management of sport-related concussion typically involves a symptom checklist, clinical examination of mental status, and neurocognitive testing. However, recent studies have identified unresolved, impaired sensorimotor function after athletes return to sport. A review and meta-analysis of all current literature regarding risk of subsequent musculoskeletal (MSK) injury after concussion has yet to be published in the medical literature. Purpose/Hypothesis: To determine the odds that athletes will sustain MSK injury after concussion. It was hypothesized a priori that concussion would increase the risk for MSK injury. Study Design: Systematic review and meta-analysis. Methods: PubMed and Google Scholar were searched from January 2000 to November 2017. Reference lists of the included studies were manually searched. Two reviewers independently searched the literature for studies published in English that reported MSK injury after athletes returned to play following a concussion. Two independent reviewers completed data extraction using PRISMA guidelines and assessed study quality using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies from the National Institutes of Health. Random effects meta-analyses were used to calculate odds ratio (OR) and incidence rate ratio (IRR) of MSK injury after concussion. The primary study outcome of interest was the number of athletes who sustained MSK injury after concussion. Results: Eight studies met inclusion criteria for meta-analysis. Meta-analysis results indicated that athletes who had a concussion had 2 times greater odds of sustaining a MSK injury than athletes without concussion (OR, 2.11; 95% CI, 1.46-3.06). In addition, athletes with concussion demonstrated a higher incidence of MSK injury after return to sport compared with nonconcussed athletes (IRR, 1.67; 95% CI, 1.42-1.96). Further analysis showed that both male and female athletes with concussion were at an increased risk of MSK injury compared with their respective same-sex, nonconcussed controls (OR > 1.56, P < .01). Conclusion: Based on the evidence of higher risk of MSK injuries after concussion, standard clinical assessments for athletes with concussion should include not only physical symptoms and cognitive function before return to sport but also neuromuscular risk factors associated with increased risk for MSK injuries.

Background: Limb asymmetries, as determined through in vivo biomechanical measures, are known risk factors for anterior cruciate ligament (ACL) injury. Previous cadaveric studies have shown a lack of significant differences in ligament strain between contralateral lower extremities when identical kinematics were simulated on specimens. Recent methodological developments have applied in vivo knee kinetics to exert landing forces on cadaveric lower extremities to mimic ACL injury events, but it is unknown whether contralateral limbs fail in a consistent manner during impact simulator testing. Hypothesis: It was hypothesized that contralateral lower extremities would not exhibit side-to-side differences in ligament strains. Furthermore, it was hypothesized that failure loads and failure locations would be independent of limb dominance. Study Design: Controlled laboratory study. Methods: Fourteen pairs of cadaveric lower extremities were obtained from an anatomic donations program (8 female, 6 male; mean ± SD: age, 41.7 ± 8.1 years; mass, 86.8 ± 27.0 kg; body mass index, 29.4 ± 9.0 kg/m 2 ). A mechanical impact simulator was used to re-create the impulse ground-reaction force generated during an in vivo landing task. Ligament strains were recorded by differential variable force transducers implanted on the ACL and medial collateral ligament (MCL). Results: No significant differences were observed in peak ACL or peak MCL strain for 5 loading conditions. Fisher exact tests of independence revealed that limb dominance was independent of both load at failure and failure location. Conclusion: There were no significant differences in ACL and MCL strain values between limb sides during in vitro impact simulation testing. This finding indicates that limb dominance does not influence the failure threshold of the ACL, since there was no significant difference in failure strains. The functional mechanics of the ACL are comparable between contralateral pairs from the same healthy specimen. Clinical Relevance: Injury mechanisms and intra-articular mechanics cannot be ethically studied in an in vivo setting. The current study provides additional insight into limb asymmetry that is observed among athletes in clinical sports medicine settings.