Asymmetric Cross Sectional Area Size of the Psoas Muscle Seems to be a Key Feature in Patients with L4-5 Lumbar Disc Herniations.

Aim: To determine the relationship between the occurrence of lumbar L4-5 disc herniation (LDH) and the size of psoas muscles.
Material and Methods: The cross-sectional areas (CSAs) of the psoas muscles were measured at the L4-5 disc level on axial MRI of patients with LDH who were admitted to the hospital between 1 January 2020 and 1 June 2020. The patients were divided into three groups according to the involvement side of LDH as the patients without disc (Group I), right side disc (Group II), and left side disc (Group III). The relationship of ipsilateral and the opposite side of the CSA of PM in the control group and the patients with LDHs was analyzed.
Results: This retrospective study included 65 patients (ages between 20 and 70 years) whose mean age is 42, 12. The mean values of the right side cross-sectional area of PM were 12.09 cm2 in Group I (n=18), 12.84 cm2 in Group II (n=20), and 14.15 cm2 in Group III (n=27), The left side values were 12.08 cm2, 13.22 cm2, 14.00 cm2 in Group I, II, and III, respectively. The difference between right and left side CSA of PM is that values of patients with left-sided LDHs were higher than those of the control and right-sided LDH group, and the difference was statistically significant. A strong correlation was observed between the left and right side of the cross-sectional area of psoas muscle at the L4-5 level (p < 0.05).
Conclusion: This study shows that there are reciprocal changes in the cross-sectional area of the psoas muscle in patients with L4-5 lumbar disc herniation.