Heterogeneity of quadriceps muscles atrophy following anterior cruciate ligament reconstruction: A longitudinal MRI study.

OBJECTIVES

This study used MRI to longitudinally assess the differences in atrophy among individual quadriceps muscles and the association between muscle volume and strength recovery following ACL reconstruction (ACLR).

DESIGN

Longitudinal within-subject.

SETTING

Laboratory.

PARTICIPANTS

13 subjects with unilateral ACLR.

MAIN OUTCOME MEASURES: MRI and isokinetic strength of bilateral quadriceps muscles were acquired at 6 months and 1 year post-ACLR. The volumes of the 4 quadriceps muscles (vastus medialis, VM; vastus lateralis, VL, vastus intermedius, VI; rectus femoris, RF) were measured. The degree of atrophy for each muscle was calculated as % difference of the uninjured leg.

RESULTS

At both time points, all 4 quadriceps muscles of the ACLR legs were significantly smaller than the uninjured legs (P < 0.001), with greater atrophy in VM/VL than VI/RF (P ≤ 0.045). None of the 4 quadriceps muscles of the ACLR legs showed significant volumetric changes over time (P > 0.171). Quadriceps volume and strength recovery in the ACLR legs were not significantly correlated (r = 0.50, P = 0.09).

CONCLUSIONS

Persistent quadriceps atrophy was found 1 year post-ACLR with greater atrophy in VL/VM than VI/RF. Limited and heterogeneous muscle hypertrophy over time and the lack of strong association between hypertrophy and strength recovery highlight the need for rehabilitation promoting both morphological and functional recovery.