THIGH MUSCLE SIZE AND STRENGTH AFTER ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION AND REHABILITATION

It is the hypothesis of the senior author (GAA) that thigh circumferen ce measurements are not an accurate reflection of thigh muscle cross-s ectional area or muscle strength after standard rehabilitation followi ng anterior cruciate ligament reconstruction. likewise, normal quadric eps femoris strength is not achieved in these patients despite aggress ive rehabilitation. The purpose of our study was to quantify thigh mus cle size and strength and correlate thigh circumference, muscle cross- sectional area by magnetic resonance imaging (MRI), and isokinetic str ength in our patients. Thirty-three patients with anterior cruciate li gament repair utilizing autografts of iliotibial band (N = 28), semite ndinosus autograft (N = 3), and bone-patellar tendon-bone autograft (N = 2) were retrospectively evaluated 48.7 +/- 6.91 months after surger y. We compared involved operated extremities with uninjured, uninvolve d contralateral extremities, measuring thigh circumference, isokinetic peak torque, and cross-sectional area by MRI. We found a significant 1.8% decrease in thigh circumference, a 10% decrease in average quadri ceps torque, and a 8.6% decrease in quadriceps cross-sectional area by MRI in the involved extremities compared with the uninvolved extremit ies. A positive correlation between MRI cross-sectional area, quadrice ps, and hamstring peak torque was recorded in involved and uninvolved extremities. A positive correlation between thigh circumference, quadr iceps, and hamstring peak torque was found in uninvolved extremities b ut not in operated extremities. The authors concluded that thigh circu mference underestimates atrophy and is not correlated with cross-secti onal thigh muscle area by MRI or strength in operated extremities. Per sistent quadriceps weakness and decreased cross-sectional area at 49 m onths postsurgery and rehabilitation continue to challenge our efforts . The pathophysiology of the decrease in thigh muscle size and quadric eps femoris strength is discussed.