The Utility of Objective Strength and Functional Performance to Predict Subjective Outcomes After Anterior Cruciate Ligament Reconstruction

Abstract

Background:Many clinicians release patients to return to activity after anterior cruciate ligament reconstruction (ACLR) based on time from surgery despite deficits in muscle strength and function. It is unclear whether symmetry or unilateral performance is the best predictor of subjective outcomes after ACLR.Purpose:To determine physical performance predictors of patient-reported outcomes after reconstruction.Study Design:Cross-sectional study; Level of evidence, 3.Methods:A total of 88 participants (49 males, 39 females; mean ± SD height, 174.0 ± 9.6 cm; weight, 76.1 ± 18.5 kg; age, 19.4 ± 3.7 years) who underwent primary, unilateral ACLR volunteered for this study. Participants had undergone reconstruction a mean of 6.9 ± 1.8 months (range, 5.0-14.1 months) before the study. All participants underwent strength testing as well as hop testing and then completed the International Knee Documentation Committee (IKDC) and Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaires. Stepwise linear regression models were used for symmetry and unilateral performance to identify the proportion of variance explained in the IKDC score, KOOS total score, KOOS-sport subscale, and time from surgery, as well as receiver operating characteristic (ROC) curve analyses on those variables that explained the most variance in patient-reported outcomes to determine cutoff thresholds.Results:No significant correlations were found between time from surgery and objective performance. The only significant predictors of IKDC score were single-hop limb symmetry index (LSI) and age (R 2 = 0.177) and unilateral triple-hop performance and age (R 2 = 0.228). The cutoff for single-hop symmetry was 0.92 (area under the curve [AUC], 0.703; P = .012), and the cutoff for normalized triple-hop distance was 3.93 (AUC, 0.726; P = .005). When stratified by age, the cutoff for single-hop symmetry was 0.81 (AUC, 0.721; P = .051) for younger patients (age <19.1 years) and was not significant for older patients (age ≥19.1 years). The cutoff for normalized triple-hop distance was 3.85 (AUC, 0.832; P = .005) in older patients and was not significant for younger patients. The only significant predictors of KOOS-sport subscale were single-hop LSI (R 2 = 0.140) and normalized knee extensor power at 180 deg/s (R 2 = 0.096). When subjective outcomes were predicted based on KOOS-sport subscale, the cutoff for single-hop symmetry was 0.85 (AUC, 0.692; P = .018).Conclusion:Hopping performance is the most predictive functional variable of subjective outcomes after reconstruction. Single-hop symmetry was most important for younger patients and unilateral triple-hop distance was most important for older patients. Clinicians should consider hopping performance when making return-to-activity decisions after ACLR.

Hop Testing Lacks Strong Association With Key Outcome Variables After Primary Anterior Cruciate Ligament Reconstruction: A Systematic Review

“…The OCEBM level for each study can be found in Table 2. Overall, 9 studies** (42.9%) were rated level 2 (cohort study), 4 studies 29,37,63,66 (19%) were rated level 3 (case-control study), and 8 studies 3,5,15,19,23,28,36,61 (38.1%) were rated level 4 (case series). There were no disagreements between the authors on study level rating.…”

“…We found 4 studies (261 patients) that performed correlation analysis between the KOOS 7,17,37,55 and at least 1 hop test. Correlations varied based on KOOS subsection and when hop testing was performed after ACLR.…”

Measures of Agility and Single-Legged Balance as Clinical Assessments in Patients With Anterior Cruciate Ligament Reconstruction and Healthy Individuals

“…This task requires patients with ACLR to use both limbs as they accelerate and decelerate in various directions. Given the known limb asymmetries in this population, 16 the Agility T Test may have exposed compensatory patterns as reflected in the group's slower times, requiring an equal number of cuts by both limbs. We did not observe differences in the unilateral measures of agility (17-hop and mat-hopping tasks).…”

“…15 However, much sporting activity is performed in a single-legged (SL) stance, stressing the importance of unilateral testing. For unilateral testing, establishing limb symmetry indexes for agility tasks, similar to strength tests, 16 may provide additional information that informs decision making for the return to physical activity after ACLR.…”

Poor functional performance 1 year after ACL reconstruction increases the risk of early osteoarthritis progression

“…Functional performance may possess differing relationships with change in individual early OA features and PROs. Functional performance deficits at the time of return to sport (RTS) are often associated with worse PROs 2–3 years after ACL injury,16 24–28 with few studies evaluating the change in PROs beyond 3 years, due to cross-sectional design. It is this change in PROs and structural outcomes that equates to the problematic accelerated trajectory of symptomatic OA in young adults post-ACLR.…”