Sarcopenia, or age-related loss of muscle mass, is measurable by computed tomography (CT). In elderly trauma patients, increased mortality is associated with decreased psoas muscle cross-sectional area (P-Area) on abdominal CT. Fall is the leading cause of injury in the elderly, and head CT is more often obtained. Masseter muscle cross-sectional area (M-Area) is readily measured on head CT. Hypothesizing that M-Area is a satisfactory surrogate for P-Area, we compared the two as markers of sarcopenia and increased mortality in elderly trauma patients.
All blunt-injured patients aged 65 years or older admitted to our trauma center during 2010 were included. Two-year postdischarge mortality was identified by matching records to county, state, and national death indices. Bilateral M-Area was measured on admission head CT at 2 cm below the zygomatic arch. Bilateral P-Area was measured on abdominal CT at the fourth vertebral body. Average M-Area and P-Area values were calculated for each patient. Cox proportional hazards models evaluated the relationship of M-Area and P-Area with mortality. Model predictive performance was calculated using concordance statistics.
Among 487 patients, 357 with M-Area and 226 with P-Area were identified. Females had smaller M-Area (3.43 cm2 vs 4.18 cm2; p < 0.050) and P-Area (6.50 cm2 vs 10.9 cm2; p < 0.050) than males. Masseter muscle cross-sectional area correlated with P-Area (rho, 0.38; p < 0.001). Adjusted Cox regression models revealed decreased survival associated with declining M-Area (hazard ratio, 0.76; 95% confidence interval, 0.60–0.96) and P-Area (hazard ratio, 0.68; 95% confidence interval, 0.46–1.00). Masseter muscle cross-sectional area and P-Area discriminated equally well in best-fit models.
In elderly trauma patients, M-Area is an equally valid and more readily available marker of sarcopenia and 2-year mortality than P-Area. Future study should validate M-Area as a metric to identify at-risk patients who may benefit from early intervention.
Prognostic study, level III.
From the Trauma Service (J.D.W., R.Y.D., P.R.L., J.B.B., S.R.S., M.J.S., C.B.S., V.B.), Scripps Mercy Hospital, San Diego, California.
Submitted: July 28, 2016, Revised: September 8, 2016, Accepted: September 10, 2016, Published online: November 4, 2016.
This study was presented at the 75th annual meeting of the American Association for the Surgery of Trauma, September 14–17, 2016, in Waikoloa, Hawaii.
Address for reprints: Steven R. Shackford, MD, Trauma Service (MER62), Scripps Mercy Hospital, 4077 Fifth Avenue, San Diego, CA 92103; email: firstname.lastname@example.org.