Context: Study of muscle volumes in patients after anterior cruciate ligament (ACL) injury and reconstruction (ACL-R) is largely limited to cross-sectional assessment of the thigh musculature, which may inadequately describe posttraumatic and postsurgical muscle function. No studies have prospectively examined the influence of ACL injury and reconstruction on lower-extremity muscle volumes. Objective: Assess magnetic resonance imaging-derived lower-extremity muscle volumes, and quantify quadriceps strength and activation in patients following ACL injury and reconstruction. Design: Prospective case series. Setting: Research laboratory and magnetic resonance imaging facility. Patients (or Other Participants): Four patients (2 men and 2 women; age = 27.4 (7.4) y, height = 169.2 (8.1) cm, and mass = 74.3 (18.5) kg) scheduled for ACL-R. Intervention(s): Thirty-five muscle volumes were obtained from a bilateral lower-extremity magnetic resonance imaging before and after ACL-R. Main Outcome Measures: Muscle volumes expressed relative to (1) a normative database presurgery and postsurgery, (2) limb symmetry presurgery and postsurgery, and (3) percentage change presurgery to postsurgery. Quadriceps function was quantified by normalized knee extension maximal voluntary isometric contraction torque and central activation ratio. Results: Involved vastus lateralis and tibialis anterior were consistently smaller than healthy individuals (z < −1 SD) presurgery and postsurgery in all patients. Involved rectus femoris and vastus lateralis were more than 15% smaller than the contralateral limb presurgery, whereas the involved rectus femoris, gracilis, vastus medialis, vastus intermedius, and vastus lateralis muscle volumes exceeded 20% asymmetry postoperatively. Involved gracilis and semitendinosus atrophied more than 30% from presurgery to postsurgery. Involved maximal voluntary isometric contraction torque and central activation ratio increased by 12.7% and 12.5%, respectively, yet strength remained 33.2% asymmetric postsurgery. Conclusions: Adaptations in lower-extremity muscle volumes are present following ACL injury and reconstruction. Anterior thigh and shank muscles were smaller than healthy individuals, and large asymmetries in quadriceps volumes were observed presurgery and postsurgery. Selective atrophy of the semitendinosus and gracilis occurred following surgery. Volumetric deficits of the quadriceps musculature may exist despite improvements in muscle strength and activation.
Grant E. Norte, Katherine R. Knaus, Chris Kuenze, Geoffrey G. Handsfield, Craig H. Meyer, Silvia S. Blemker and Joseph M. Hart
Mark A. Feger, Luke Donovan, C. Collin Herb, Geoffrey G. Handsfield, Silvia S. Blemker, Joseph M. Hart, Susan A. Saliba, Mark F. Abel, Joseph S. Park and Jay Hertel
Context: Patients with chronic ankle instability (CAI) have demonstrated atrophy of foot and ankle musculature and deficits in ankle strength. The effect of rehabilitation on muscle morphology and ankle strength has not previously been investigated in patients with CAI. Objective: Our objective was to analyze the effect of impairment-based rehabilitation on intrinsic and extrinsic foot and ankle muscle volumes and strength in patients with CAI. Design: Controlled laboratory study. Setting: Laboratory. Patients: Five young adults with CAI. Intervention: Twelve sessions of supervised impairment-based rehabilitation that included range of motion, strength, balance, and functional exercises. Main Outcome Measures: Measures of extrinsic and intrinsic foot muscle volume and ankle strength measured before and after 4 weeks of supervised rehabilitation. Novel fast-acquisition magnetic resonance imaging was used to scan from above the femoral condyles through the entire foot. The perimeter of each muscle was outlined on each axial slice and then the 2-dimensional area was multiplied by the slice thickness (5 mm) to calculate muscle volume. Plantar flexion, dorsiflexion, inversion, and eversion isometric strength were measured using a hand-held dynamometer. Results: Rehabilitation resulted in hypertrophy of all extrinsic foot muscles except for the flexor hallucis longus and peroneals. Large improvements were seen in inversion, eversion, and plantar flexion strength following rehabilitation. Effect sizes for significant differences following rehabilitation were all large and ranged from 1.54 to 3.35. No significant differences were identified for intrinsic foot muscle volumes. Conclusion: Preliminary results suggest that impairment-based rehabilitation for CAI can induce hypertrophy of extrinsic foot and ankle musculature with corresponding increases in ankle strength.