The Effect of Lumbosacral Transitional Vertebrae (LSTV) on Paraspinal Muscle Volume in Patients with Low Back Pain

To determine if psoas, multifidus, and erector spina muscle volume at intervertebral disc levels differ in patients with lumbosacral transitional vertebrae (LSTV) and low back pain (LBP), and in LBP patients without LSTV. This retrospective study included 101 patients that underwent lumbar spinal MRI due to LBP. The patients were divided into two groups according to the presence of LSTV, as those with LSTV (LSTV group) and those without LSTV (control group). Those in the LSTV group were classified according to Castellvi classification, and whether or not LSTV was bilateral or unilateral. The lumbar lordosis angle was measured using sagittal T2-weighted MR images. Axial T2-weighted images were used to bilaterally measure psoas, multifidus, and erector spina muscle volume at intervertebral disc levels. Among the 101 participants, 33 were male (32.7%) and 68 were female (67.3%). Left multifidus muscle volume at the L4-5 level was significantly lower in the LSTV group than in the control group (p = 0.033). Right and left erector spina muscle volume at the L5-S1 level was significantly lower in the LSTV group than in the control group (right side: p = 0.010; left side: p = 0.003). The mean lumbar lordosis angle was 47.54 ± 12.69° in the LSTV group, versus 35.34 ± 11.53° in the control group (p < 0.001). There were not any significant differences in psoas, multifidus, or erector spina muscle volume between the patients with unilateral and bilateral LSTV (p > 0.05). The present findings indicate that paraspinal muscle volume can be used to understand LSTV symptomatology.