Investigation of the Morphology of Psoas Major and Quadratus Lumborum Muscles in Sacralized Individuals

This study aimed to evaluate the morphological characteristics of the Psoas Major (PMa) and Quadratus Lumborum (QL) muscles in individuals with lumbosacral transitional vertebra (LSTV) anomalies and to compare the muscle cross-sectional areas (CSA) of these individuals with a control group without LSTV. In this retrospective study, computed tomography (CT) images of 108 individuals aged between 18 and 65 years were analyzed. Participants were divided into two groups based on the presence of sacralization: 54 individuals with sacralization formed the "sacralization group," and 54 individuals without LSTV comprised the control group. Sacralization cases were subclassified according to the Castellvi classification. PMa and QL muscle CSAs were measured bilaterally at the L4 vertebral level using ImageJ software. Data were analyzed with SPSS version 22.0. The sacralization group exhibited significantly larger left PMa CSA (12.56 cm², P=0.001), left QL CSA (6.25 cm², P=0.004), and right QL CSA (6.48 cm², P=0.026) compared to the control group. Male participants had significantly larger PMa and QL CSAs than females (P0.05). However, a weak negative correlation was observed between age and PMa CSA (right PMa: P=0.013, r=-0.237; left PMa: P=0.007, r=-0.257). The observed increase in CSA of PMa and QL muscles in individuals with sacralization suggests that this anatomical variation may influence muscle morphology. These morphological changes could impact lumbar and pelvic function and should be considered during clinical evaluations.