Elsevier

The Spine Journal

Volume 17, Issue 1, January 2017, Pages 81-87
The Spine Journal

Clinical Study
The fatty degeneration of lumbar paraspinal muscles on computed tomography scan according to age and disc level

https://doi.org/10.1016/j.spinee.2016.08.001Get rights and content

Abstract

Background Context

Spinal degeneration can occur not only in the bone and disc but also in muscles. Fatty infiltration (FI) and decreased volume have been described as characteristic changes that occur in muscle degeneration. Many studies about the lumbar paraspinal muscles have been conducted on patients with spine problems. However, the natural changes of age-dependent degeneration in the paraspinal muscles have not been studied properly.

Purpose

The purpose of this study is to investigate age- and level-dependent changes of the lumbar paraspinal muscles in the population without lumbar spinal symptoms.

Study Design

This study is a retrospective case-control study.

Patient Sample

A total of 887 patients who underwent computed tomography scan for abdomen and pelvis (APCT) between January 2013 and December 2013 were enrolled. After excluding 237 patients with medical history of spine surgery, low back pain, myopathy, muscular dystrophy, infectious disease, vertebral fracture, and deformity, 650 patients were finally subjected to this study.

Outcome Measure

The patients were divided into three age groups: young (20–39 years old), middle (40–59 years old), and old (60–89 years old). The degree of FI was checked twice for multifidus muscle (MF), erector spinae muscle (ES), and psoas muscle (PS) at each disc level from L1 to S1 on APCT by two investigators. The FI was measured as the Hounsfield unit, a mean density (MD) on CT.

Methods

The age differences were compared with the data of the young group, and the level differences were compared with the data of the L1–L2 level. Student t test and intraclass correlation coefficient were checked for statistical analysis.

Results

The gender ratio was not significantly different among the groups. Comparing with the young group, the MD of MF significantly decreased at L5–S1 in the middle group (p<.05), and at L3–L4–L5–S1 in the old group (p<.05). The MD of ES was significantly decreased at all levels in the old group (p<.05) but not significant in the middle group. Comparing with the L1–L2 level, the MD of MF significantly decreased at L5–S1 in the middle group (p<.05) and at L4–L5–S1 in the old group (p<.05). The MD of ES was significantly decreased at L5–S1 in the young and middle groups (p<.05) and at L4–L5–S1 in the old group (p<.01) compared with those at L1–L2. According to the age- and level-dependent changes of MD in the MF and ES, there was a tendency of progressive increase of FI in the muscles with age, which seemed to start from L5–S1 and spread to the upper levels. The age-dependent fatty degeneration appeared wider in the ES than the MF. The level-dependent FI of the ES showed a similar pattern with the MF, but the change of the ES seemed to start earlier in age than the MF at the L5–S1. There was no significant MD change in the PS according to age and level. Intraobserver and interobserver reliabilities were both high across all of the muscles (0.86–0.94 and 0.83–0.92).

Conclusions

As a result, the degree of intramuscular fat infiltration seems to be affected by age, disc level, and muscle type. It seems to be more prominent in the extensor muscles, extending from lower to upper levels.

Introduction

Age-related changes are important medical and socioeconomic concerns of modern society [1]. Spinal degeneration, one of the results of the aging process, can result in a lower quality of life in old age [2]. Studies of degenerative spinal changes to date have focused on the bone and joint of the spine [3]. However, studies on the spinal muscular biomechanics have shown that age-related changes occur not only in the skeletal system but also in the muscles [4], [5], [6], [7], [8]. Fatty infiltration and muscle atrophy have been described as characteristic changes that occur in muscle degeneration [9]. Many studies about the lumbar paraspinal muscles have been conducted on patients with spine problems, which were not designed to understand the muscular changes according to the aging process [10], [11], [12], [13], [14], [15]. Patients with spinal symptoms may have more spinal degeneration than the non-symptomatic population. Therefore, the natural changes of age-dependent degeneration in the paraspinal muscles have not been studied properly. In the present study, we tried to investigate age-dependent changes of the lumbar paraspinal muscles at each lumbar disc level in the population without lumbar spinal symptoms.

Section snippets

Materials and methods

This study was conducted on 887 patients who underwent computed tomography of the abdomen and pelvis (APCT) as a part of regular health checkup at Chung-Ang University Hospital between January 2013 and December 2013. A retrospective study was conducted on 650 patients after excluding 237 patients (63 with previous spinal surgery, 152 with medical record histories of back pain or radicular leg pain, and 22 with other conditions such as myopathy, muscular dystrophy, infectious disease, vertebral

Results

The mean ages and gender ratios (male:female) were 32.7±5.3 and 1:0.8, 53.3±5.2 and 1:0.8, and 77.8±8.1 and 1:1.1 in the young, middle, and old groups, respectively. There was no statistically significant difference in the mean age and gender ratio among the three groups (Table).

Discussion

To date, several imaging studies have analyzed the degenerative changes in the paraspinal muscles. Decreased cross sectional area (CSA) and increased fatty degeneration have been found in the population with chronic back pain or degenerative lumbar kyphosis [11], [13], [17]. In addition, some studies of the muscle degenerations were conducted on patients with postsurgical back pain [18], [19]. However, there was no previous study analyzing muscle degeneration in the population without lumbar

Conclusions

Our data indicate that the paraspinal muscle degeneration can be affected by age, disc level, and muscle type. It seems to be more prominent in the extensor muscles, starting from the lowermost lumbar joint and spreading upwardly. Although our data seem to show that the increased tension stress in the extensors of lower lumbar level is related with the muscle degeneration, more studies are required to confirm the hypothesis.

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    FDA device/drug status: Not applicable.

    Author disclosures: SHL: Non-financial. SWP: Grant: Technology Innovation Program (D, Paid to the author, Advanced Technology Center [ATC], 10048523, Development of fluorography system under 50% irradiation dose with image quality on par with angiographic equipment to global leader in next generation, funded by the Ministry of Trade, Industry & Energy [MI, Korea]), pertaining to the submitted manuscript. YBK: Non-financial. TKN: Non-financial. YSL: Non-financial.

    The disclosure key can be found on the Table of Contents and at www.TheSpineJournalOnline.com.

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