The Magnetic Resonance Imaging of the Psoas Muscle Area as the Prognostic Factor for Survival and Adverse Events in Spinal Metastasis Surgery.

Study Design: Retrospective study.

Objective: This study aimed to evaluate the ability of the mortality and adverse events prediction following metastatic spinal surgery of MRI-based cross-sectional psoas muscle area (PMA).

Methods: A retrospective chart review, 120 patients who had undergone metastatic spinal surgery were included. The cross-sectional area identified the PMA under MR-imaging at the L3 or L4 pedicle level, which was classified into 3 tertiles. We used univariate and multivariate cox proportional hazard regression to assess whether PMA was associated with 30-day, 90-day, 1-year, and overall mortality.

Results: The small psoas tertile group populations had a higher mortality rate than the large psoas tertile group. PMA in T1 and T2 had a probability of a higher 90-d mortality rate than PMA in T3 (T1 VS T3: = .29 and T2 VS T3: = .12). The median survival time was 7 months, 9 months, and 10 months in PMA T1, T2, and T3, respectively. PMA in tertile 2 had a significantly higher mortality rate of 38% compared to PMA in tertile 3 (HR 1.38, 95% CI .83-2.32, = .02). Considering PMA as a continuous variable, every 1 mm increment of PMA resulted in the increase survivorship of 1% (HR .99 with 95% CI .99-1).

Conclusion: The MRI-based cross-sectional PMA tends to predict the 90-d mortality rate and overall mortality rate in spinal metastasis patients who underwent spinal surgery. The PMA should be considered one of the prognostic factors in the treatment of metastatic spinal patients.