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

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.