This observational cross-sectional study aims to investigate the differences in spinopelvic and coccygeal morphometric parameters in standing and sitting positions among patients diagnosed with coccydynia. A total of 50 adult patients (aged 25-65 years) diagnosed with coccydynia based on clinical evaluation and imaging findings were included. Lateral radiographs were obtained in both standing and sitting positions. Radiological assessments included spinopelvic parameters such as sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), sacral table angle (STA), and sacral kyphosis (SK), along with coccygeal morphology based on the Postacchini-Massobrio classification. The study further aimed to explore whether these morphometric differences are associated with the presence of low back pain and to assess variations across different coccygeal morphology types.

Coccydynia is a condition characterized by pain in the coccygeal region, often exacerbated by sitting and postural changes. While its etiology is multifactorial, anatomical variations in coccygeal and spinopelvic alignment may play a significant role in symptom development. Despite increasing attention to coccygeal mobility and morphology in radiological evaluations, the relationship between coccygeal type, spinopelvic alignment, and posture-specific morphometric changes has not been fully clarified.

This observational cross-sectional study was designed to evaluate morphometric parameters of the sacropelvic and coccygeal regions in both standing and sitting positions in patients diagnosed with coccydynia. The study included 50 adult patients (42 female, 8 male) aged between 25 and 65 years who were diagnosed with coccydynia based on clinical findings and radiological confirmation. Lateral radiographs were obtained in both weight-bearing and seated positions to allow for comparative measurement.

The following radiological parameters were assessed: thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), thoracopelvic angle and its modification (TPA-T1PA), sacral slope (SE), pelvic incidence (PI), pelvic tilt (PT), spinosacral angle (SSA), sacral table angle (STA), and sacral kyphosis (SK). Coccygeal features were evaluated based on vertebral segment number, sacrococcygeal and intercoccygeal joint fusion, segmental angulation, and mobility status. Morphological types were categorized using the modified Postacchini-Massobrio classification. The presence of coccygeal spicules and their frequency across types were recorded. Dynamic morphometric assessments included sacrococcygeal angle (SKA), intercoccygeal angle (IKA), coccygeal height (KY), sacral height (SY), and sacrococcygeal height (SKY). Mobility was determined by comparing the angular displacement between standing and sitting radiographs and classified as normal, hypermobile, hypomobile, or posterior luxation, depending on the flexion-extension response and translation under load.The study aimed to investigate the changes in these parameters between postures and explore whether these variations are associated with the presence of low back pain and functional impairment. Additionally, differences among coccygeal morphology subgroups in terms of spinopelvic parameters were analyzed.

Inclusion Criteria:

Patients aged between 25 and 65 years

Clinically diagnosed with coccydynia

Provided informed consent to participate in the study

Exclusion Criteria:

Presence of any disease that may cause spinal malalignment

Any hip- or knee-related condition that may lead to spinal malalignment

History of surgery involving the cervical, thoracic, lumbar, or coccygeal spine

patients aged 25 to 65 years who presented to the University of Health Sciences Fatih Sultan Mehmet Training and Research Hospital with a preliminary diagnosis of coccydynia and were clinically confirmed were consecutively enrolled.

Patients with a history of spinal trauma, surgery, congenital deformities, malignancy, or rheumatological disease were excluded.

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