Effect Of Time Post Anterior Cruciate Ligament Reconstruction On Knee Extension Strength

Abstract

Isokinetic knee extension (KE) peak torque is used to appraise a patient’s strength post-anterior cruciate ligament (ACL) reconstruction (ACLR). PURPOSE: The purpose of this study was to assess the effect of autograft and biological sex on involved (I) and uninvolved (UI) limb isokinetic KE strength over time post-ACLR. METHODS: An honest broker provided anonymous data from our institution’s ACLR data repository. Primary ACLR patients (N = 444, 18.0 ± 3.0 y at ACLR) 12 to 30 years old were included in the analysis if they had an appraisal between 0 and 12 months post-ACLR, a bone-patella tendon-bone (BTB) or hamstring (HS) autograft, and KE peak torque normalized to body mass for I and UI at 60, 180, 300°·s-1. Separate linear mixed-effects models for I and UI were used to model KE strength over time post-ACLR. Time post-ACLR was a fixed and random effect, biological sex and autograft were fixed effects, and patients were assigned a random intercept and slope. Significance was p < .05. RESULTS: There were 181 and 53 males and 170 and 40 females with HS and BTB, respectively. 444 patients had one observation (0.42 ± 0.15 y post-ACLR) and 221 had two observations (0.60 ± 0.12 y post-ACLR). For UI, there was an effect of autograft (F = 4.32, p = .038) as HS had a 10% [-5, 25] higher KE strength intercept than BTB. For I, there was an effect of autograft (F = 18.53, p < .001), time post-ACLR (F = 27.32, p < .001), and autograft × time post-ACLR (F = 3.90, p = .049). HS had an 18% [3, 33] higher KE strength intercept than BTB. BTB demonstrated a 36%·y-1[7, 64] KE strength improvement rate, but the strength improvement rate for HS was 15%·y-1 [-45, 16] lower than BTB. CONCLUSION: BTB causes greater bilateral KE strength deficits after ACLR compared to HS and the deficit on UI potentially suggests cross-over neural inhibition. BTB demonstrates a greater rate of KE strength improvement over time post-ACLR compared to HS. Biological sex had no effect on KE strength suggesting responses after ACLR are similar for males and females. Better understanding of these responses may lead to improved post-ACLR appraisals and outcome forecasting. More frequent observations over time post-ACLR and nonlinear models may elucidate unique response patterns for autograft, biological sex, and limb.