Longitudinal Assessment of Quadriceps Muscle Morphology Before and After Anterior Cruciate Ligament Reconstruction and Its Associations With Patient-Reported Outcomes

Abstract

Background: Reductions in muscle size are common after anterior cruciate ligament reconstruction (ACLR) and may contribute to suboptimal patient outcomes. However, few studies have quantified postoperative alterations in muscle quality and evaluated its associations with patient-reported function. Hypotheses: Rectus femoris cross-sectional area (CSA) will decrease postoperatively but improve at return to activity (RTA), rectus femoris muscle quality (percentage fat [PF]) will increase postoperatively and be greater at RTA compared with preoperative values, and rectus femoris CSA and PF will be associated with International Knee Documentation Committee (IKDC) scores at both postoperative time points. Study Design: Case series. Level of Evidence: Level 4. Methods: A total of 26 individuals who sustained an ACL injury and underwent reconstructive surgery were evaluated preoperatively (T0), 9 weeks post-ACLR (T1), and at RTA. Rectus femoris CSA and PF were evaluated bilaterally via ultrasound imaging, and patient-reported function was assessed using the IKDC score. Results: Bilateral reductions in rectus femoris CSA were noted from T0 to T1 ( P < 0.01). Only the uninvolved limb returned to preoperative CSA ( P = 0.80), as the involved limb failed to return to preoperative levels at RTA ( P = 0.04). No significant changes in rectus femoris PF were observed across time points ( P > 0.05). Lesser PF ( P < 0.01) but not CSA ( P = 0.75) was associated with higher IKDC score at T1. Lesser PF ( P = 0.04) and greater CSA ( P = 0.05) was associated with higher IKDC score at RTA. Conclusion: Substantial atrophy occurs bilaterally after ACLR, and the involved limb does not return to preoperative muscle size despite the patient completing rehabilitation. Quadriceps muscle morphology is associated with patient-reported function and may be an important rehabilitation target after ACLR. Clinical Relevance: Quadriceps atrophy and poor muscle quality may contribute to suboptimal patient functioning and quadriceps dysfunction and may be important in RTA decision making. Assessing muscle morphology using ultrasound may be a feasible and clinically beneficial tool in patients after ACLR.

Arthrogenic Muscle Inhibition Following Anterior Cruciate Ligament Injury

“…In addition, this study demonstrated slightly smaller vasti muscle volumes compared with a normative database (<1 SD) 83 of uninjured individuals. These findings appear to be supported by several investigations [84][85][86] reporting no between-limb differences in rectus femoris CSA or volume after ACL injury. However, volumetric differences do not appear to be uniform between muscles or within a single muscle, as the collective evidence of individual muscle impairments is conflicting.…”

“…A 21% reduction in rectus femoris CSA has been observed in the injured limb and to a lesser degree in the contralateral limb (12%) 9 weeks after surgery. 84 Likewise, an increase in quadriceps volume asymmetry has been observed from presurgery (6% asymmetry) to 4 (19% asymmetry) and 12 (17% asymmetry) weeks post-ACLR. 88 Small-to-large deficits in quadriceps CSA and volume appear to persist from 6 months to 5 years post-ACLR.…”

“…For example, greater intramuscular fat content associate with worse subjective knee function among individuals recovering from ACLR. 62,84 These data suggest that evaluation of intramuscular fat content by means of ultrasound imaging may serve as a useful clinical measure. Previous studies have also reported acute 92 and persistent 93 atrophy among type IIa and IIx muscle fibers in the vastus lateralis following ACLR.…”

“…87 Large magnitude deficits in quadriceps CSA and volume are observed compared with the contralateral limb from 1 to 3 months following ACLR. 82 Several studies 84,88 have reported a decrease in muscle size from presurgery to 4, 9, and 12 weeks after ACLR providing clear evidence of quadriceps atrophy during the early months of recovery. A 21% reduction in rectus femoris CSA has been observed in the injured limb and to a lesser degree in the contralateral limb (12%) 9 weeks after surgery.…”

“…29,41,82 Although some evidence appears to indicate a recovery of muscle size over time, 82 large magnitude asymmetries remain present more than a year later. 89 Several studies 77,84 have described atrophy occurring at 7 and 9 months after ACLR near the time patients are traditionally cleared for unrestricted physical activity. In contrast, another study 77 actually observed a continued decrease in muscle volumes of the rectus femoris (5%), vastus lateralis (3%), and vastus medialis (6%) from presurgery to 7 months.…”