Background: Current anterior cruciate ligament reconstruction (ACLR) guidelines utilize single-leg hop tests (SLHTs) to assist in return-to-sport decision making. A limb symmetry index (LSI) of ≥90% is often required; however, after ACLR, most youth athletes cannot achieve this standard. Reporting the performance of age-matched normative controls will allow clinicians to compare post-ACLR performance with noninjured peers, improving the utility of SLHTs. The purpose of this study was to report hop test LSI within healthy youth athletes and determine whether athlete performance surpasses post-ACLR requirements. Hypothesis: The LSI for the majority of healthy youth athletes will be ≥90%. Study Design: Cross-sectional cohort study. Level of Evidence: Level 3. Methods: Each participant performed a single hop (SH), triple hop (TrH), crossover hop (CrH), and timed hop (TiH). A 3-trial mean was utilized to calculate an LSI (nondominant/dominant leg [self-reported kicking leg]) for each hop. The frequency of pass/fail at ≥90% LSI was calculated. Pearson correlation coefficients analyzed the relationship between the different hops, and a 2-way analysis of variance determined the effects of age and sex on LSI. Results: A total of 340 participants (54% male; mean age, 10.9 ± 1.5 years; range, 8-14 years) were included. The mean LSI was >95% for each SLHT (SH, 97.9% [SD, 0.7]; TrH, 96.6% [SD, 0.6]; CrH, 96.8% [SD, 0.8]; TiH, 96.5% [SD, 0.6]). When analyzed as a test battery, only 45% of participants achieved this standard. Significantly weak to moderate correlations existed among hop tests ( P < 0.01; r = 0.342-0.520). Age and sex had no effect on LSI ( P < 0.05). Conclusion: While the mean LSI in our sample was >95% for each individual hop test, participant performance across all SLHT components varied, such that less than half of healthy athletes could achieve ≥90% LSI across all hops. Clinical Relevance: Current guidelines require ≥90% LSI on SLHTs. The majority of healthy youth athletes could not achieve this standard, which questions the validity of this LSI threshold in youth athletes after ACLR.

Background: The incidence of anterior cruciate ligament (ACL) injury and surgical reconstruction in youth athletes is increasing. In the United States, most athletes elect to undergo ACL reconstruction (ACLR), with the goal of returning to their previous level of athletic performance. Although surgery and rehabilitation address the underlying impairments in knee stability and function, recent literature indicates psychological or emotional factors, such as fear or confidence, may be contributing factors limiting successful return to play. The Anterior Cruciate Ligament Return to Sport after Injury (ACL-RSI) is a 12-item scale designed to assess an athlete’s psychological readiness to return to sports across three separate domains (emotions, confidence in performance and risk appraisal). In adults, the ACL-RSI is reliable and valid, and several studies have documented that athletes with higher scores are more likely to successfully return to their pre-injury level of sports participation. The predictive abilities of this scale, have led many experts to advocate for the ACL-RSI to be used as part of rehabilitation guidelines, in order to identify those athletes that may benefit from a modified course of post-operative rehabilitation or additional emotional or psychological support. Although the information from the ACL-RSI is valuable in adults, the utility of this scale has never been explored within the pediatric population. Thus, the purpose of this study is to evaluate the utility of the ACL-RSI within the pediatric population and establish normative values among healthy children. Hypothesis: As all of these subjects were currently healthy, we hypothesized that mean scores should demonstrate a positive skew towards higher levels of confidence (ceiling effect) with values of 80-100 on each question. Methods: A group of 84 healthy, youth athletes between the ages of 8-14, completed the ACL-RSI. All subjects were currently involved in competitive sports at the time of participation. The athletes were instructed to complete the 12-item ACL-RSI questionnaire and were able to seek assistance from parents as necessary. Each item is scored on a scale ranging from 0-100 and a total score is calculated from summing all responses and expressing them a percentage of 100%. Higher scores indicate a greater degree of athletic confidence or more positive psychological response to injury. Mean and variability measures for each question and total score were calculated and compared to existing literature. Results: A total of 83 subjects (mean age 11.1 ± 1.2) completed the questionnaire in full. There were slightly more females (n=46, 54.8%) than males. The majority of participants were White (70%), African American (13%) or more than one race (10%). The most frequent primary sport was soccer (38%), followed by baseball (27%) and basketball (26%). The mean ACL-RSI score for the entire sample was 79.9 (SD 14.1). Individual question analysis revealed lower than expected mean scores (<80%) with large standard deviations for 7 out of 12 questions. (Table 1) With the exception of only question #1 and #12, responses demonstrated such large variability that both the maximum and minimum (0-100) scores were selected, indicating both ceiling and floor effects. (Table 1) Conclusions/Significance: The mean ACL-RSI score (79.9) within this group of uninjured pediatric athletes was similar to previous values for post-ACLR adults that successfully return to sports. However, it was surprising that the mean score wasn’t higher, as this was a healthy population of un-injured youth athletes, and we hypothesized that our data would demonstrate a positive skew towards the upper range of this scale. Response ranges including 0 (indicating either high fear or severe lack of confidence) within nearly all questions was unexpected. Additionally, there were particularly low mean scores and high variability within 7 of the 12 questions. All of these factors raise the suspicion that children may not fully comprehend the material or have difficulty interpreting the response system of the ACL-RSI and thus calls into question the validity of this scale in youth athletes. Similar to other research efforts that have modified adult outcome scales to be utilized within the pediatric population, our results support further exploration of the utility of the ACL-RSI within pediatric athletes and may possibly suggest that a pediatric specific version should be created. [Table: see text]

Background: The incidence of anterior cruciate ligament reconstruction (ACLR) in youth athletes is rising. Current rehabilitation guidelines recommend the use of a battery of single leg hop tests (SLHT) to assess performance and assist in return to sport (RTS) decision making. Although there is agreement on the use of SLHT, the level of required limb symmetry varies. Historically, values of 85-90% were acceptable; however, some experts are now advocating for more strict values of 95 to >100%. While higher performance thresholds are logical, and some data suggests reduced potential for reinjury using these more conservative criteria, previous literature shows that <25% of youth athletes can achieve =90% symmetry more than 1 year after ACLR. Furthermore, no studies have reported normal SLHT symmetry among youth athletes, making it difficult to compare post-rehabilitation values to non-injured peers. The purpose of this study was to report limb symmetry in SLHT performance in healthy youth athletes. Methods: This was a single episode cross-sectional study of youth athletes between the ages of 8-14 years-old. In order to be eligible for the study, all subjects had to be without any history of ACLR, no current lower extremity injuries, and presently participating in organized competitive sports. All data was collected on-site during practice or games. Consent, demographics, injury history, and sports participation information was obtained prior to testing. Each subject was instructed in a single hop (SH), triple hop (TrH), crossover hop (CH) and timed hop (TH) test and allowed 3-5 practice repetitions. (Figure 1) Successful trials required a controlled landing, with 2 second hold, as previously described. Distance from starting line to the heel was recorded in centimeters for the SH, TrH and CH. TH was recorded in seconds. Limb symmetry index (LSI) of non-dominant to dominant leg (self-reported kicking leg) was calculated for each hop. Descriptive statistics and frequency of pass/fail at 90% LSI threshold were calculated. The relationship between the different components of the SLHT were analyzed with Pearson Correlation Coefficient, while a two-way ANOVA was utilized to analyze whether age and sex affected LSI performance. Results: A total of 347 athletes were screened and met the inclusion criteria. After excluding those with incomplete data, a total of 340 subjects (54% male (n=184); mean age 10.9±1.5 years) were included in the analysis. The sample was heavily Caucasian (85%), with a mean height and weight of 146.6 cm ± 11.2 and 40.7 kg ± 10.8 respectively. Although most subjects identified as multisport athletes, the top self-reported primary sports were soccer (52%, n=178), basketball (22%, n=73), and baseball (10%, n=34). The mean LSI was >95% for each SLHT as follows (mean, standard error): SH=97.9% (0.7), TrH=96.6% (0.6), CH=96.8% (0.8), and TH=96.5% (0.6). When analyzed as a test battery, requiring the subject to achieve =90% LSI on all four components of the SLHT, only 45% of subjects were able to achieve this level of symmetry. (Figure 2) Pearson analysis revealed statistically significant (p<0.01) weak to moderate (r=0.342-0.520) correlations among all hop tests. (Table 1) There were no significant effects (p<0.05) for either age or sex on LSI for any of the individual hop tests. Conclusions/Significance: SLHT are commonly utilized as a battery, requiring an athlete to achieve a threshold of LSI (e.g. 90%) on each hop to satisfy RTS criteria. Although the mean LSI in our sample was >95% for each individual component of the SLHT, subject performance across all SLHT components varied, such that less than half of healthy athletes could achieve a standard of 90% LSI when applied as a test battery. These results question the validity of requiring >90% LSI on the SLHT battery in youth athletes after ACLR and highlights the need for further research into the use and interpretation of SLHT during RTS decision making. Tables and Figures: [Figure: see text][Figure: see text][Table: see text]

Background: Limb dominance implies asymmetrical performance due to preferential strength or motor control within a single limb. While dominance may be easy to define and quantify within the upper extremity, there is currently no consensus as to whether limb dominance exists within the lower limbs, and if it does, how to best define it. While objective differences in limb performance would be the gold-standard for the identification of limb dominance, these methods may not be feasible within injured athletes. Several methods of identifying perceived limb dominance utilizing subjective reporting have been described; however, limb dominance may be task dependent and reports analyzing the correlation between objective and subjective performance are limited, particularly among adolescent athletes. Purpose: The purpose of this study was to test the agreement between performance-based and self-reported measures of limb dominance in three different single leg hopping tasks. Methods: These data were prospectively collected as part of a large cross-sectional study of healthy youth athletes aged 8-16 years-old. Self-selected limb dominance was determined by asking the following question: “Which leg would you use to kick a ball as far as you could?”. Each subject performed a series of single leg hops and 3-trial means of the single hop for distance (SH), timed hop (TH), and vertical hop (VH) were used for analysis. Paired samples t-test or Wilcoxon-Signed Rank test were utilized to identify differences in limb performance for each of the hop tests. Associations between self-selected and performance-based measures of limb dominance were analyzed using Chi-square. Results: A total of 352 subjects (55% male(n=191), mean age=11.1) were included. There was a small but statistically significant difference in side-to-side performance for all hop tests with a mean difference of 2.58cm(p<0.001) for SH, 0.13s(p<0.001) for TH and 0.29cm(p=0.03) for VH. There was limited agreement between self-selected and performance-based limb dominance across all hop tests (55%SH, 54%VH, and 66%TH). Similarly, Chi-square analysis revealed no associations (p>0.05) between self-selected and performance-based limb dominance across all hop test constructs. Conclusions: Although a single limb did perform better on all hop tests, the mean differences were small, and likely not clinically relevant. Perceived limb dominance did not predict performance regardless of hopping task. These findings illustrate that equality of performance can be considered normal for young athletes recovering from lower extremity injury. This information also brings into question the appropriateness of holding the perceived dominant limb to higher standards or accepting lower standards for the non-dominant limb. Tables and Figures: [Table: see text][Figure: see text] References: Goekeler A, Welling W, Benjaminse A. A critical analysis of limb symmetry indices of hop tests in athletes after anterior cruciate ligament reconstruction: a case control study. Orthop Traumatol Surg Res. 2017;103(6):947-951. doi: 10.1016/j.otsr.2017.02.015 Losciale JM, Zdeb RM, Ledbetter L, Reiman MP, Sell TC. The Association Between Passing Return-to-Sport Criteria and Second Anterior Cruciate Ligament Injury Risk: A Systematic Review With Meta-analysis. Journal of Orthopaedic & Sports Physical Therapy. 2019;49(2):43-54. doi:10.2519/jospt.2019.8190 Mulrey CR, Shultz SJ, Ford KR, Nguyen A-D, Taylor JB. Methods of Identifying Limb Dominance in Adolescent Female Basketball Players. Clinical Journal of Sport Medicine. 2018;Publish Ahead of Print. doi:10.1097/jsm.0000000000000589 van Melick N, Meddeler BM, Hoogeboom TJ, Maria W. G. Nijhuis-Van Der Sanden, Cingel REHV. How to determine leg dominance: The agreement between self-reported and observed performance in healthy adults. Plos One. 2017;12(12). doi:10.1371/journal.pone.0189876 Velotta, J. & Weyer, J. & Ramirez, A. & Winstead, J. & Bahamonde, Rafael. Relationship between leg dominance tests and type of task. Portugese J Sport Sci. 2011;11(1035-1038). Wellsandt E, Failla MJ, Snyder-Mackler L. Limb symmetry indexes can overestimate knee function after anterior cruciate ligament injury. J Orthop Sports Phys Ther. 2017;47(5):334-338.

Background: Most experts recommend utilizing single leg hop tests to help determine an athlete’s readiness to return to sports after anterior cruciate ligament reconstruction (ACLR). A limb symmetry index (LSI =involved limb/uninvolved limb) of ≥90% is typically required by most contemporary protocols. However, limb symmetry may underestimate continued post-operative deficits due to performance declines within the uninvolved limb after ACLR. Additionally, LSI may not accurately identify those at risk of repeat injury, and doesn’t assist in ensuring maximal patient effort. Comparing height normalized hop distances to uninjured controls has been suggested as an additional criteria to better recognize performance deficits after ACLR. Purpose: To characterize single leg hop test performance in a large group of healthy youth athletes and determine the relationships of sex or age on hop performance. Methods: This was a cross-sectional study of healthy youth athletes aged 8-14 years-old, who were currently participating in organized sports. Using their dominant leg, each subject performed a triple hop (TrH) in which they quickly hopped on one leg three times, achieving maximal linear distance, while holding their balance after the last hop. Distance from starting line to the heel was recorded in centimeters. Each subject’s hop distance was normalized to body height and served as the dependent variable. A two-way ANOVA analyzed any effects of age and sex. A-priori alpha was set at p≤0.05. Results: A total of 340 subjects (Male [n=184], mean age 10.9±1.5 years) were included. Across the entire sample, mean TrH distance was 2.2 times body height. ANOVA demonstrated no differences for main effect of sex (mean TrH/height, Males=2.2, Females=2.1, p=0.212). (Figure 1) Main effect of age was significant (p<0.001) with Bonferroni post-hoc analysis indicating 13 year-olds normalized TrH distance (2.6 times body height) was greater than all other age groups (8 yrs=1.9, 9yrs=2.0, 10yrs=2.1, 11yrs=2.2, 12yrs=2.3). (Figure 2) The 12 year-old performance was significantly greater than 8-9 year-olds only (2.3 vs 1.9-2.0). Conclusions: When normalized to body height, TrH performance increases around the ages of 12-13 years. Regardless of sex, athletes aged 8-11 can be expected to TrH approximately 2 times body height, while athletes near age 13 should have TrH values of 2.6 times body height. Due to post-operative deconditioning within the healthy limb, the use of age-matched hopping norms in addition to LSI may offer better determination of functional recovery or effort. As performance changes with age, future research should focus on establishing normative performance in older subjects. Figures/Tables: [Figure: see text][Figure: see text]