1. 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
2. Ardern, et al. Am J Sports Med
3. Ardern, et al. Br J Sports Med
4. Ardern, et al. Am J Sports Med
5. Flanigan, et al. Arthroscopy
6. Lentz, et al. J Orthop Sports Phys Ther
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