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Computed Tomography-Based Muscle Attenuation and Electrical Impedance Myography as Indicators of Trunk Muscle Strength Independent of Muscle Size in Older Adults

Anderson, Dennis E. PhD; Bean, Jonathan F. MD, MPH; Holt, Nicole E. MPH; Keel, John C. MD; Bouxsein, Mary L. PhD

American Journal of Physical Medicine & Rehabilitation: July 2014 - Volume 93 - Issue 7 - p 553–561
doi: 10.1097/PHM.0000000000000059
Original Research Articles

Objective: The aim of this study was to examine the associations of computed tomography-based x-ray attenuation and paraspinal electrical impedance myography measures of trunk muscles with absolute and relative (normalized by body weight) trunk extension strength, independent of muscle cross-sectional area.

Design: This is a cross-sectional study of mobility-limited community-dwelling older adults (34 women, 15 men; mean [SD] age, 78.2 [7.2] yrs) recruited from within an existing prospective research cohort. Trunk extension strength, computed tomography-based trunk muscle cross-sectional area and attenuation at L4 level, and paraspinal electrical impedance myography measures were collected.

Results: Attenuation was positively correlated with absolute and relative strength for multiple muscle groups (r = 0.32–0.61, P < 0.05). Paraspinal electrical impedance myography phase was positively correlated with paraspinal attenuation (r = 0.30, P = 0.039) and with relative strength (r = 0.30, P = 0.042). In multivariable linear regressions adjusting for sex and cross-sectional area, attenuations of the anterior abdominal muscles (semipartial r2 = 0.11, P = 0.013) and combined muscles (semipartial r2 = 0.07, P = 0.046) were associated with relative strength.

Conclusions: Although attenuation was associated with relative strength, small effect sizes indicate limited usefulness as clinical measures of muscle strength independent of muscle size. However, there remains a need for additional studies in larger and more diverse groups of subjects.

From the Department of Orthopedics, Beth Israel Deaconess Medical Center, Boston, Massachusetts (DEA, JCK, MLB); Department of Orthopedic Surgery, Harvard Medical School, Boston, Massachusetts (DEA, MLB); Spaulding Rehabilitation Hospital, Boston, Massachusetts (JFB, NEH); Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, Massachusetts (JFB, JCK); and The Spine Center, New England Baptist Hospital, Boston, Massachusetts (JCK).

All correspondence and requests for reprints should be addressed to Dennis E. Anderson, PhD, Department of Orthopedics, Beth Israel Deaconess Medical Center, 330 Brookline Ave, RN115, Boston, MA 02215.

Electrical impedance myography (EIM) measurement equipment was provided by Skulpt, Inc, (formerly Convergence Medical Devices, Inc.) and this equipment is still investigational.

Supported by funds from a Departmental Research Grant Award from the Department of Orthopedics, Beth Israel Deaconess Medical Center, and by the National Institutes of Health through National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) grant R01-AR053986, National Institute of Child Health and Human Development grant K24-HD070966, and National Institute on Aging (NIA) grants T32-AG023480 and R01-AG032052.

The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.

© 2014 by Lippincott Williams & Wilkins