• Kazushi Takayama, Teruo Kita, Hiroaki Nakamura, Fumiaki Kanematsu, Toshiya Yasunami, Hideki Sakanaka, and Yoshiki Yamano.
• *Department of Orthopaedic Surgery, Seikeikai Hospital, Osaka, Japan †Department of Orthopaedic Surgery,Saiseikai Nakatsu Hospital, Osaka, Japan ‡Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka, Japan.
• Spine. 2015 Sep 1.

Study DesignA cross-sectional imaging study of paraspinal muscle degeneration using a new index for easy evaluation.ObjectiveTo examine the natural progression of age-related changes in the lumbar paraspinal muscles, and to verify the validity of our new index for evaluating paraspinal muscle degeneration SUMMARY OF BACKGROUND DATA.: Measurement of paraspinal muscle morphology is an effective method for reflecting atrophy and fat infiltration, but it is complicated to perform. Therefore, we focused on the groove between lumbar paraspinal muscles as a simple index for evaluating paraspinal muscle degeneration.MethodsA total of 160 subjects aged 10 to 88 years (10 male and 10 female subjects in each decade) with lumbar lordosis of more than 20° were included. Body mass index (BMI) was calculated. Sagittal T2-weighted magnetic resonance imaging (MRI) was used to measure lumbar lordosis, while axial T2-weighted MRI was used to measure cross-sectional area (CSA) and fat infiltration rate of the paraspinal muscles at the intervertebral disc level from L1 to L5. To quantify the depth of the groove between the paraspinal muscles, our own image index, lumbar indentation value (LIV: equal to the length of the bulge of the muscle to the attachment of the spinous process), also was measured. We then determined the correlation between LIV and paraspinal muscle degeneration.ResultsThere were no significant differences in BMI and lumbar lordosis between age groups. CSA of the paraspinal muscles tended to decrease with age, and fat infiltration rate increased with age. There was a negative correlation between CSA and fat infiltration rate at all levels (r = -0.474 to -0.634). LIV decreased significantly with age and strongly correlated with CSA at all levels (r = 0.709-0.789).ConclusionOur new index is a simple and effective parameter for evaluating paraspinal muscle degeneration associated with aging.Level Of Evidence4.

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