MRI-Based 3D Shape Analysis of Thigh Muscles: Patients with Chronic Obstructive Pulmonary Disease Versus Healthy Adults

Abstract

Because lower limb muscles differ in architecture and function, the systemic effects of chronic obstructive pulmonary disease (COPD) and related disuse may result in regional abnormalities. The purpose of this study was to investigate the differences between patients with COPD and healthy controls in three-dimensional shape and size measurements of individual thigh muscles. Twenty patients with COPD and 20 healthy adults (aged 55-79 years) underwent magnetic resonance imaging of the thighs. After manual segmentation of individual knee extensor and flexor muscles, the three-dimensional shape of each muscle was obtained using specialized software. Eight shape descriptors were computed both globally (for the whole muscle) and regionally (for portions of the muscle). A two-tailed t test with a modified Bonferroni correction was used to compare group differences. Compared to the thigh muscles of healthy subjects, vastus intermedius and semimembranosus showed the most shape abnormalities in the COPD group (P < .01). Greater regional shape anomalies in the COPD group were found in the middle to proximal regions of all knee extensor muscles and the middle region of the semimembranosus muscle, compared to those of the control group (P < .01). In the COPD group, more shape abnormalities were found in the knee extensors than in the knee flexors (P < .01). A non-uniform distribution of atrophy and size changes was found across knee extensors and flexors in patients with COPD. Further research is required to investigate the underlying mechanisms of regional morphologic abnormalities of the thigh muscles and the increased susceptibility of the knee extensors to atrophy-related anatomic anomalies in COPD.