Deficits in Contralateral Limb Strength Can Overestimate Limb Symmetry Index After Anterior Cruciate Ligament Reconstruction
Thomas E. Moran, Anthony J. Ignozzi, Zachary Burnett, Stephan G. Bodkin, Joseph M. Hart, Brian C. Werner
Abstract
Purpose To evaluate whether contralateral limb strength represents a dynamic, rather than static, data point after anterior cruciate ligament reconstruction (ACL‐R). Methods Patients who underwent isolated ACL‐R at a single institution were identified. Patients completed an institutional Lower‐Extremity Assessment Protocol (LEAP) testing protocol at 6 and 9 months postoperatively. Extension strength and flexion strength of the ipsilateral and contralateral limbs and limb symmetry index (LSI) were compared between the 6‐ and 9‐month testing outcomes. Subgroup analysis compared patients demonstrating less than or greater than 10% change in contralateral limb flexion and extension strength between 6 and 9 months postoperatively. Results A total of 144 subjects were included in this study. On average, contralateral limb flexion and extension strength increased 2‐4% between 6 and 9 months postoperatively. However, the contralateral limb increased >10% from 6 to 9 months in extension and flexion strength in 35/144 (24.3%) and 55/144 (38.2%) of patients, respectively. The cohort with >10% change between 6 and 9 months had significantly weaker contralateral extension and flexion strength at 6 months compared to the cohort that demonstrated <10% change (extension: 2.00 vs 2.39; P < .001; flexion: 0.84 vs 1.08; P < .001), but similar ipsilateral limb performance. Therefore, the >10% change cohort had a significantly greater LSI at 6 months compared to the <10% change cohort (67.3% vs 59.4%; P = .006). No demographic or operative factors correlated with which patients demonstrated >10% flexion or extension strength changes of the contralateral limb. Conclusion A large percentage of patients demonstrate significant changes in their contralateral limb flexion and extension strength between 6 and 9 months postoperatively that result from an initial contralateral limb strength deficit. This may limit the utility of the contralateral limb as a control for comparison to the operative extremity during return to sport assessment.