INTRODUCTION: Obesity has been reported to be associated with disc degeneration and low back pain. However, no reports have compared the body composition of patients with lumbar degenerative spine disease (DSD) and healthy adults without low back pain. This study aimed to compare the body composition and disc degeneration between patients with lumbar DSD who underwent instrumentation surgery and healthy adults without low back pain.
METHODS: Body composition and disc degeneration were compared among 27 healthy volunteers (15 males and 12 females) with an average age of 53 years (29-68) and 54 randomly selected age- and sex-matched patients from 223 patients who underwent instrumentation surgery for lumbar DSD between January 2020 and March 2023 at our institution. Body composition was measured by whole-body dual-energy X-ray absorptiometry (DXA). Trunk lean mass (kg/m2), trunk fat mass (kg/m2), lower limb lean mass (kg/m2), and lower limb fat mass (kg/m2) were compared for body composition. Lean mass and fat mass were divided by the square of height. The Intervertebral disc degeneration was evaluated using the Pfirrmann classification of lumbar spine MRI, with the grade of the most severely degenerated intervertebral disc among the five intervertebral discs from L1/2 to L5/S as the grade of the case. Oswestry Disability Index (ODI) and Roland-Morris Disability Questionnaire (RDQ) were used to evaluate low back pain. Wilcoxon rank-sum and chi-square tests were used for statistical analysis, with P < 0.05 indicating a significant difference.
RESULTS: Trunk lean mass of healthy adults and patients with lumbar DSD was 7.7 vs 8.8 (P=0.0005); trunk fat mass was 3.3 vs 4.2 (P=0.0124), lower limb fat mass was 2.0 vs 2.4 (P=0.1291); and lower limb lean mass was 5.1 vs 5.4 (P=0.1622). The Pfirrman classification was as follows: in healthy adults, there were five cases (18.5%) with grade III, 19 cases (70.4%) with grade IV, and three cases (11.1%) with grade V. In patients with lumbar DSD, there were one case (1.9%) with grade III, 28 cases (51.9%) with grade IV, and 25 cases (46.3%) with grade V (P=0.0008). The ODI was 2.7% in healthy adults and 50.4% in patients with lumbar DSD (P<0.0001). The RDQ were 0.2 for healthy adults and patients with lumbar DSD was 13.6 (P<0.0001).
DISCUSSION: Patients with lumbar DSD had significantly higher trunk lean mass and trunk fat mass than healthy adults without low back pain. However, there were no significant differences in lower limb lean mass or lower limb fat mass. Also, a higher prevalence of significant (grade V) disc degeneration was found in patients with lumbar DSD than in the healthy adults. This data suggest that intervertebral disc degeneration is significantly more advanced in patients with lumbar DSD. The prevalence of lumbar DSD and the progression of lumbar disc degeneration are associated with higher trunk lean mass and fat mass.