Reliability and validity of measurement of cross-sectional area ratio of psoas muscle for evaluating sarcopenia: A comparison of CT and MRI — The International Society for the Study of the Lumbar Spine
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Reliability and validity of measurement of cross-sectional area ratio of psoas muscle for evaluating sarcopenia: A comparison of CT and MRI (#1051)

Chang-Hoon Jeon 1 , Nam-Su Chung 1 , Han-Dong Lee 1 , Hee-Woong Chung 1 , Ki-Hoon Park 1 , Ha-Seung Yoon 1
  1. Ajou University School of Medicine, Suwon, Kyonggi, South Korea

Introduction: Sarcopenia is defined as low muscle mass combined with a loss of muscle strength or physical performance. Sarcopenia is a poor prognostic facttor in various areas of spinal disases. The psoas muscle (PM) cross-sectional area ratio (CSAR) is a definite indicator of sarcopenia. Numerous studies have shown that a lower CSAR of PM is related to a poor prognosis. However, there is no standard way to measure CSAR of PM. Earlier studies were measured at different levels (L2-3 to L4-5) and different imaging modalities (CT vs. MRI). The purpose of our study was to analyze the difference in CSAR of PM between CT and MRI, as well as the intra- and inter-observer reliability between two imaging modalities.

Methods: We retrospectively analyzed 30 patients who had done both a lumbar CT and a lumbar MRI. We measured the cross sectional areas (CSA) of both the PM and core structures (inter verebral discs and vertebral bodies) at L2-3, L3, L3-4, L4, and L4-5. Two experienced surgeons measured twice, one month apart. The CSAR of PM was calculated by dividing the CSA of PM by the CSA of the core structure. The paired t-test was used to compare the CSAR of PM between CT and MRI. Intra- and inter-observer reliabilities of CT and MRI were analyzed using intra-class correlation methods.

Results: CSAR of PM on both sides of all levels were larger on MRI. At the lower level (L4 and L4-5), the differences between CT and MRI were much larger and statistically significant (P < 0.05). The intra-and inter-observer reliabilities of CT for CSAR of PM were 0.757-0.954 and 0.885-962 (good to excellent), respectively. The intra-and inter-observer reliabilities of MR for CSAR of PM were 0.701-0.975 and 0.864-0.967 (moderate to excellent), respectively.

Discussion: The CSAR of PM was significantly larger on MRI than on CT, especially at the lower levels. The intra- and inter-observer reliability was higher in CT scans than in MRI scans. When evaluating sacopenia using the CSAR of PM  it would be better to measure CSAR of PM in the upper lumbar region using CT.

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