Correlation of multifidus degeneration with sex, age and side of herniation in patients with lumbar disc herniation

Abstract Objective The aim of this study was to determine the relationship between multifidus degeneration and sex, age and side of protrusion in patients with lumbar disc herniation(LDH). Methods Data were collected from September 2015 to September 2022 from patients with L4/5 and L5/S1 LDH. A total of 104 patients (62 males and 42 females) were included in this study, and there were 35 and 69 cases of L4/5 and L5/S1 LDH, respectively. Patients were divided into 4 groups according to age: group 1 (20–29), group 2 (30–39), group 3 (40–49) and group 4 (50–59). Magnetic resonance spectroscopy analysis was used to observe the fat fraction (FF) and functional cross-sectional area (f-CSA) of the defatted multifidus muscle of the protruding side (affected side) and the nonprotruding side (healthy side) of the L4/5 and L5/S1 gaps to evaluate the relationship between multifidus degeneration and sex, age and protruding side in patients with LDH. Results Between sexes, the FF of the multifidus muscle was significantly greater in women than in men, regardless of whether it was on the affected or healthy side of the L4/5 segment or on the affected or healthy side of the L5/S1 segment (P < 0.05). Between age groups, there was a significantly positive relationship between the change in FF (%) of the multifidus muscle in patients with LDH and age, with increasing fatty infiltration of the multifidus increasing with age (P < 0.05); notably, there was a significant difference between group 4 and the remaining three groups but no significant difference between groups 1, 2 and 3. The f-CSA of the multifidus (cm 2 ) was negatively correlated with age, with the f-CSA of the multifidus becoming more atrophic with increasing age; specifically, there was a significant difference between group 1 and the other three groups (P < 0.05) but not between groups 2, 3 and 4. Regarding the side of the herniated disc, (1) the differences in FF and f-CSA at the L4/5 and L5/S1 levels were not statistically significant between the affected side and the healthy side in patients with lumbar disc herniation at the L4/5 segment (P > 0.05); (2) the differences in FF and f-CSA at the L5/S1 level were not statistically significant between the affected side and the healthy side in patients with LDH at the L5/S1 segment (P > 0.05); (3) the difference between FF at the L4/5 level and f-CSA and FF at the L5/S1 level was not statistically significant (P > 0.05); and (4) the f-CSA at the L5/S1 level was significantly greater on the healthy side than on the affected side (P < 0.05). Conclusion The proportion of lipoatrophy in female patients with L4/5 and L5/S1 disc herniations was greater than that in male patients. Lipoatrophy of the multifidus muscle increased with age and was significantly worse in patients over 50 years of age. The f-CSA of the multifidus muscle was negatively related to age, and the f-CSA of the multifidus muscle became more atrophic with increasing age. A comparison of degeneration showed no significant difference between the L4/5 patients and the L5/S1 patients in terms of f-CSA atrophy on the affected side of the herniated disc compared to the healthy side.