MRI-based assessment of lower extremity muscle volumes in patients with knee osteoarthritis

Abstract

Purpose: To describe lower extremity muscle volumes in patients with knee joint osteoarthritis. Methods: Seven patients with radiographic evidence of knee joint osteoarthritis (6M, 1F, 47±9yrs, 183±5cm, 99±21kg) were scanned on a 3T Siemens Trio MRI scanner. Axial images were acquired for the lower extremity ranging from the ankle to the thoracic vertebre. Thirty-four lower extremity muscles were manually segmented using a semi-automated program written in Matlab. Individual muscle volumes were normalized to patient height and mass. Normalized volumes for each muscle were converted to z-scores relative to a database of volumes collected from normal healthy volunteers. The z-scores were averaged across the patients and means, 95% confidence intervals calculated. Results: On average, the vastus lateralis (z=-4.1, [%CI=4.5,3.8]) rectus femoris (z=-2.2, [-2.6, -1.9]) pectineus (z=-2.5 [-3.0, -1.9]) and obterator externus (z=-2.1 [-2.6, -1.6]) volumes were all more than 2 standard deviations below the corresponding muscle volume means of the healthy group. The vastus intermedius (z=1.4, [0.5, 2.4]) and obterator internus (z=2.0, [0.7, 3.2]) were the only muscles that were on average larger than healthy control with confidence intervals not crossing zero (Fig 1) Conclusions: Patterns of lower extremity muscle deficits include the quadriceps and deep hip muscles that adduct the thigh however, portions of deep hip and thigh musculature may experience an adaptive compensation in patients with chronic knee osteoarthritis. Disclosure: This study is supported by a grant from the Wallis H Coulter Foundation.