Knee Function, Strength, and Maintenance of Preinjury Sports Participation in Young Athletes after Anterior Cruciate Ligament Reconstruction Matthew P. Ithurburn, PT, DPT, OCS1, Mark V. Paterno, PT, PhD, MBA, SCS2, Staci Thomas, MS2, Timothy E. Hewett, PhD3, Laura C. Schmitt, PT, PhD1,4 1School of Health and Rehabilitation Sciences, The Ohio State University, Columbus, OH; 2Division of Occupational Therapy and Physical Therapy and Division of Sports Medicine, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH; 3Biomechanics and Sports Medicine Research, Mayo Clinic, Rochester, MN; 4Division of Physical Therapy, The Ohio State University, Columbus, OH Logistic Regression Results Level of Sports Participation Collected for Preinjury and 1 Year Post-RTS: Introduction Predictor from RTS *Odds Ratio (95% CI); P-value Involved Limb SH Distance 5.33 (0.81, 35.19); p=.082 Uninvolved Limb SH Distance 6.24 (0.99, 39.50); p=.052 Involved Limb TH Distance 1.96 (1.07, 3.61); p=.029 Uninvolved Limb TH Distance 2.07 (1.12, 3.81); p=.020 Involved Limb CH Distance 1.74 (1.01, 3.04); p=.049 Uninvolved Limb CH Distance 1.59 (0.94, 2.74); p=.086 Tegner Activity Rating Scale: 11-point categorical scale Higher scores indicate higher activity levels Reliable and responsive to change after ACLR Return-to-sport (RTS) outcomes following ACLR are poor Pre-injury sports: 31% at 1 year [1]; 41% at 2 years [2]; 63% at any time [3] Competitive sports: 33-44% [3,4] Factors associated with successful RTS following ACLR Higher confidence/less fear of injury [1,2,5,6] Higher knee function, performance, and strength [2,4,6] Less knee pain, symptoms, and instability [5,6] The association between knee function and strength and successful maintenance of pre-injury sports participation over time in young high-level athletes after ACLR has not been studied previously Purpose: To examine differences in knee function and strength at the time of RTS between young athletes after ACLR who maintain pre-injury sports participation one-year post-RTS and those who do not Hypothesis: Young athletes after ACLR who maintain pre-injury sports participation one-year post-RTS will demonstrate higher self-reported knee function, higher knee functional performance, and higher strength than those who do not Statistical Analyses: Divided into 2 groups based on preinjury and 1 year post-RTS Tegner scores Maintained preinjury sports participation (1 year Tegner ≥ Preinjury Tegner) Did not maintain preinjury sports participation (1 year Tegner < Preinjury Tegner) Group differences in RTS function and strength data compared using Mann Whitney U tests (data non-normality) Ability of RTS function/strength data to predict maintenance of preinjury sports participation examined using logistic regression RTS - return-to-sport; SH - single-hop; TH - triple-hop; CH - crossover-hop; *Odds ratios of successful RTS status with every 0.5 leg lengths increase in distance hopped; CI - confidence interval Discussion A low proportion (57%) of young athletes maintained pre-injury sports participation 1 year post-RTS after ACLR Consistent with previous studies [1-4] Those who successfully maintained preinjury sports participation over 1 year demonstrated higher single-leg hop test absolute performance at the time of RTS on both the involved and uninvolved limbs However, the groups did not differ in LSIs for single-leg hop tests or strength measures at the time of RTS Previous studies have demonstrated that more symmetric single-leg hop test performance was associated with successful RTS [2,4] Did not examine the role of fear of additional injury or lack of confidence Did not compare individuals that sustained 2nd ACL injury with the sports participation maintenance groups Results Maintained sports participation Did not maintain sports participation Sustained 2nd ACL injury Maintained Did Not p Gender Distribution, n Male Female 17 (26%) 49 (74%) 7 (27%) 19 (73%) .909 Graft Type Hamstring autograft BPTB autograft Allograft 29 (44%) 32 (48%) 5 (8%) 17 (65%) 8 (31%) 1 (4%) .177 Age at RTS 17.4 ± 2.8 17.5 ± 2.5 .813 Time from Surgery to RTS (months) 8.2 ± 2.6 8.2 ± 1.2 .972 Methods N=66 57% Excluded from group analyses 115 individuals participating in the ACL REconstruction Long-term outcomes in Adolescents and Young adults (RELAY) Study after primary, unilateral ACLR and recently cleared to RTS N=26 23% Age* Gender Time from Surgery to Baseline Testing (RTS)* Graft Type Pre-Injury Tegner Score* 17.1 ± 2.5 years 88 Female 27 Male 8.2 ± 2.4 months 57 HS 50 BPTB 8 ALLO 8.8 ± .77 N=23 20% RTS Self-Reported Function and Single-Leg Hop Test Performance Future Directions *Mean ± SD; RTS - return-to-sport; HS - hamstring autograft; BPTB - patellar tendon autograft; ALLO - allograft Data Collected at the Time of RTS: Self-reported knee function: Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales: Pain, Symptoms, Activities of Daily Living, Quality of Life, Sport Knee functional performance: Single-leg hop tests for distance (Fig. 1) Single-hop (SH), triple-hop (TH), crossover-hop (CH) Involved and uninvolved limbs; normalized to height Quadriceps and hamstring muscle strength: Isokinetic at 180°/second and 300°/second (Fig. 2) Involved and uninvolved limbs; normalized to mass Limb-symmetry indices (LSI) were calculated for strength measures and hop tests using: Examining the impact of other clinical factors (fear and confidence; landing mechanics/movement quality) on successful maintenance of sports participation in young athletes Examining the interactions among function, strength, and sports participation after ACLR Comprehensively evaluating clinical cutoffs/criteria for successful maintenance of sports participation in young athletes after ACLR p=.091 p=.061 No differences between groups (all p>.05) p=.019 p=.008 p=.057 p=.041 RTS Quadriceps and Hamstring Muscle Strength Figure 1. Single-leg hop tests. Acknowledgments This work was funded by support from the National Institutes of Health grant F32-AR055844, the National Football League Charities Medical Research Grants 2007, 2008, 2009, 2011, and the Foundation for Physical Therapy References No differences between groups (all p>.05) No differences between groups (all p>.05) 1. Ardern, et al. Am J Sports Med. 2013. 2. Ardern, et al. Am J Sports Med. 2015. 3. Ardern, et al. Br J Sports Med. 2011. 4. Ardern, et al. Am J Sports Med. 2011. 5. Flanigan, et al. Arthroscopy. 2012. 6. Lentz, et al. J Orthop Sports Phys Ther. 2012. Figure 2. Quadriceps and hamstring muscle strength testing. LSI = (involved value / uninvolved value) x 100% ** No Group Differences in LSI for Single-Leg Hop Tests or Strength Measures