In this study, based on cross-sectional CT imaging from adults with (n = 85) and without (n = 56) sacralization, the dimensions of the multifidus (MM), erector spina (ES) and abdominal muscles at the L1–2 and L4–5 intervertebral discus levels were evaluated. The data we obtained revealed that the muscle sizes of the individuals with sacralization were similar to the muscle sizes of the individuals in the control group. In addition, according to Castellvi classification, Type 2b was the most common type of sacralization in our study at 42.35%.
Sacralization, a congenital vertebral anomaly, is a frequently encountered condition in the general population . The relationship between LSTV and low back pain (LBP) is well known and studies on paraspinal muscle dimensions are quite extensive [2, 13, 16]. However, it is a known fact that the reduced muscle mass in the lumbar region not only affects the global sagittal alignment of the spine but also plays a role in the development of LBP [1, 14]. In addition, the muscles of the anterior-lateral abdominal wall play an important role in the spine stability . Studies investigating the relationship between LSTV and both paraspinal and abdominal muscle sizes are limited, regardless of LBP . Therefore, in our study, images of patients who applied with pre-diagnoses such as urinary system stones, intestinal and visceral organ pathologies other than LBP, were examined for sacralization, and paraspinal and abdominal muscle sizes of individuals with sacralization and those in the control group were analyzed and compared.
The presented study differs from previous studies that showed individuals with LSVT to have atrophic musculature. Our data showed that there were statistically similarity in the paraspinal and abdominal muscles between the both groups. There could be two reasons for this. First, hypomobility at the sacralization level is compensated by hypermobility of segments above this level. This hypermobility may have caused individuals with sacralization to have similar muscle sizes to the control group, contrary to expectations, as it required more muscular workload. Second, most of the studies on this subject were conducted by examining the images of patients with LBP [2, 13, 16]. Today, the importance of paraspinal muscle quality in patients with low back pain is widely accepted. Muscle atrophy itself may play an important role in the pathogenesis of LBP. Therefore, studies on images taken for LBP may not only reflect the characteristics of individuals with sacralization. However, a recent study of 46 patients with LSTV reported a reduction in muscle sizes .
Our study revealed a side effect regarding cross-sectional areas of RA and ES in terms of L1-2 measurements. Also revealed a side effect regarding cross-sectional areas of RA, IO and ES in terms of L4-L5 measurements. This corroborates the studies of Becker et al. showing that individuals with LSTV have a different muscle load than the control group.
Our study has some limitations. First, because it was a retrospective study, we could not analyze clinical findings such as pain, activity limitation, and spasm. This prevented us from separating symptomatic and asymptomatic individuals. Second, morphological and degenerative changes in the facet or disc and fat changes in the muscles were not analyzed.