An Objective and Reliable Method for Identifying Sarcopenia in Lumbar Spine Surgery Patients: Using Morphometric Measurements on Computed Tomography Imaging

STUDY DESIGN: A retrospective observational study. PURPOSE: Establish a quantifiable and reproducible measure of sarcopenia in patients undergoing lumbar spine surgery based on morphometric measurements from readily available preoperative computed tomography (CT) imaging. OVERVIEW OF LITERATURE: Sarcopenia—the loss of skeletal muscle mass—has been linked with poor outcomes in several surgical disciplines; however, a reliable and quantifiable measure of sarcopenia for future assessment of outcomes in spinal surgery patients has not been established. METHODS: A cohort of 90 lumbar spine fusion patients were compared with 295 young, healthy patients obtained from a trauma da¬tabase. Cross-sectional vertebral body (VB) area, as well as the areas of the psoas and paravertebral muscles at mid-point of pedicles at L3 and L4 for both cohorts, was measured using axial CT imaging. Total muscle area-to-VB area ratio was calculated along with intraclass correlation coefficients for interobserver and intraobserver reliability. Finally, T-scores were calculated to help identify those patients with considerably diminished muscle-to-VB area ratios. RESULTS: Both muscle mass and VB areas were considerably larger in males compared with those in females, and the ratio of these two measures was not enough to account for large differences. Thus, a gender-based comparison was made between spine patients and healthy control patients to establish T-scores that would help identify those patients with sarcopenia. The ratio for paravertebral muscle area-to-VB area at the L4 level was the only measure with good interobserver reliability, whereas the other three of the four ratios were moderate. All measurements had excellent correlations for intraobserver reliability. CONCLUSIONS: We postulate that a patient with a T-score <−1 for total paravertebral muscle area-to-VB area ratio at the L4 level is the most reliable method of all our measurements that can be used to diagnose a patient undergoing lumbar spine surgery with sarcopenia.