Although the recovery of strength has been emphasized following ACI, limited information exists regarding the importance of re-establishing neuromuscular control and coordination. Therefore, the purpose of this study was to determine the relationship among functional performance measures and strength 1-year following ACI and mid-term patient-reported outcomes (PROs).
Thirty-three patients (35±9 yrs, 180±38cm, 90±20kgs) who previously underwent ACI to the knee and had a minimum of two year follow-up were included in the study. All included patients had completed functional tests simulating walking, squatting, rising from sitting, stepping-up and stepping-down using the NeuroCom Long Forceplate(Clackamas, OR) and isokinetic strength testing 1 year following ACI. PROs (IKDC, KOOS, WOMAC, Lysholm, VR-36) were also completed annually following surgery. Spearman Rho correlations were used to determine the relationship between function 1 year following surgery and PRO scores at the last available follow-up (5.25±2.19 years).
Measures of neuromuscular control and coordination (rho=0.39-0.69, p<0.05), including directional control during weight-shifting, symmetry while squatting, single-limb balance, lunge force, and side-to-side differences in step-down and lunge impact forces, along with 1-year PRO scores (rho=0.40-0.67, p<0.05) were correlated with subsequent PRO scores. There was no correlation between peak isokinetic strength in flexion or extension, concentrically or eccentrically, and future PRO scores.
The restoration of neuromuscular control and coordination within the first year following ACI may be a more important clinical benchmark than the restoration of strength. In particular, side-to-side asymmetries in the ability/willingness to generate force or eccentrically load the limb were associated with lower PROs at a mean follow-up of 5 years. Likewise, PRO scores at 1-year were correlated with future follow-up scores, suggesting that a patient’s perceived level of function at 1-year may be indicative of his/her overall prognosis. Therefore, particularly low scores should be examined closely to determine strategies for addressing deficits in function or pain.