Longitudinal Changes in Quadriceps Morphology over the First Three Months Following Anterior Cruciate Ligament Reconstruction

Abstract

ABSTRACT Purpose Neuromuscular deficits and atrophy following anterior cruciate ligament reconstruction (ACLR) may be accompanied by changes in muscle composition and poor quadriceps muscle quality (QMQ). Quadriceps atrophy occurs following ACLR, but improves within the first three post-operative months, yet this hypertrophy could be attributable to increases in non-contractile tissue (i.e. poor QMQ). The purposes of this study were to evaluate changes in QMQ following ACLR and determine if changes in QMQ and cross-sectional area (CSA) occur in parallel or independently. Methods A longitudinal prospective cohort design was implemented to evaluate QMQ and CSA in 20 individuals with ACLR and 12 healthy controls. Participants completed three testing sessions (baseline/pre-surgery, 1 month, and 3 months) during which ultrasound images were obtained from the vastus lateralis (VL) and rectus femoris (RF). QMQ was calculated as the echo intensity (EI) of each image, with high EI representing poorer QMQ. Anatomical CSA was also obtained from each image. Results RF and VL EI were greater at 1 and 3 months in the ACLR limb compared to baseline and the contralateral limb, and did not change between 1 and 3 months. VL and RF CSA in the ACLR limb were smaller at 1 and 3 months compared to the contralateral limb and controls (VL only), but increased from 1 to 3 months. Changes in QMQ and CSA were not correlated. Conclusions QMQ declines within the first month following ACLR and does not improve by 3 months even though hypertrophy occurs, suggesting that these morphological characteristics change independently following ACLR. Poorer QMQ represents greater concentration of noncontractile tissues within the muscle and potentially contributes to chronic quadriceps dysfunction observed following ACLR.