Sagittal Spinopelvic and Coccygeal Alignment in Sitting and Standing Positions in Coccydynia (Coccydynia)

Sagittal Radiographic Analysis of Spinopelvic and Coccygeal Alignment in Sitting and Standing Positions in Patients With Coccydynia

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.

Study Overview

• Status: Completed
• Conditions: Coccydynia; Morphological Analysis and Classification; Sagittal Balance

Detailed Description

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.

• Study Type: Observational
• Enrollment (Actual): 50

Contacts and Locations

Study Locations

• Turkey
  • Istanbul, Turkey, 34752
    • Fatih Sultan Mehmet Training and Research Hospital
  • İstanbul, Turkey, 34098
    • Fatih Sultan Mehmet Training and Research Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

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.

Description

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

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
Coccydynia; Coccydynia patients

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Sacral Slope (SS)	Sacral slope will be measured on standardized lateral radiographs in both standing and sitting positions.	At baseline (single time point)
Pelvic Tilt (PT)	Pelvic tilt will be measured on sagittal radiographs in both standing and sitting positions.	At baseline (single time point)
Pelvic Incidence (PI)	Pelvic Incidence will be measured on sagittal radiographs in both standing and sitting positions.	At baseline (single time point)
Spinosacral Angle (SSA)	Spinosacral Angle will be measured on sagittal radiographs in both standing and sitting positions.	At baseline (single time point)
Sacral Kyphosis (SK)	Sacral Kyphosis will be measured on sagittal radiographs in both standing and sitting positions.	At baseline (single time point)
Sacral Table Angle (STA)	Sacral Table Angle will be measured on sagittal radiographs in both standing and sitting positions.	At baseline (single time point)
Thoracic Kyphosis (TK)	Thoracic Kyphosis will be measured on sagittal radiographs in both standing and sitting positions.	At baseline (single time point)
Lumbar Lordosis (LL)	Lumbar Lordosis will be measured on sagittal radiographs in both standing and sitting positions.	At baseline (single time point)
Sagittal Vertical Axis (SVA)	Sagittal Vertical Axis will be measured on sagittal radiographs in both standing and sitting positions.	At baseline (single time point)
Thoracolumbar Angle (TPA-T1PA)	Thoracolumbar Angle will be measured on sagittal radiographs in both standing and sitting positions.	At baseline (single time point)
Coccygeal Morphology- Vertebral Segment Number	Coccygeal features will be evaluated	At baseline (single time point)
Coccygeal Morphology- sacrococcygeal joint fusion	Coccygeal features will be evaluated	At baseline (single time point)
Coccygeal Morphology- intercoccygeal joint fusion	Coccygeal features will be evaluated	At baseline (single time point)
Coccygeal Morphology- segmental angulation	Coccygeal features will be evaluated	At baseline (single time point)
Coccygeal Morphology- presence of coccygeal spicules	Coccygeal features will be evaluated	At baseline (single time point)
Coccygeal Morphometry Type	Classification (Type 1-5)	At baseline (single time point)
Coccygeal Mobility	Coccygeal mobility will be assessed by measuring the angular difference of the coccyx between the standing and sitting positions on lateral radiographs. The change in coccygeal angle reflects the degree of coccygeal movement during postural transition.	At baseline (single time point)
Sacrococcygeal Angle (SKA)	SKA will be measured using the angle between the sacral axis and first coccygeal segment on lateral radiographs.	At baseline (single time point)
Intercoccygeal Angle (IKA)	IKA will be measured as the angle between coccygeal segments	At baseline (single time point)
Coccygeal Height (KY)	The vertical height of the coccyx from the tip to the base will be measured in the sagittal plane. ertical height of the coccyx from the tip to the base will be measured in the sagittal plane. Vertical height of the coccyx from the tip to the base will be measured in the sagittal plane.	At baseline (single time point)
Sacral Height (SY)	Vertical sacral height will be assessed from the superior to the inferior sacral end on the lateral radiograph. ertical height of the coccyx from the tip to the base will be measured in the sagittal plane. Vertical height of the coccyx from the tip to the base will be measured in the sagittal plane.	At baseline (single time point)
Sacrococcygeal Height (SKY)	Combined vertical height from sacral promontory to coccyx.	At baseline (single time point)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Clinical Assessment- Pain severity	Unit of Measure: Units on a Numeric Rating Scale (0-10) Description: Pain severity will be assessed using the Numeric Rating Scale (NRS), where 0 indicates no pain and 10 indicates the worst imaginable pain.	At baseline (single time point)
Clinical Assessment - Quality of Life (SF-12)	Unit of Measure: SF-12 Score (0-100) Description: General health-related quality of life will be evaluated using the 12-Item Short Form Survey (SF-12).	At baseline (single time point)
Clinical Assessment - Disability - Oswestry Disability Index (ODI) Score	Unit of Measure: Score (0-100) Description: Functional disability related to low back pain will be assessed using the Oswestry Disability Index (ODI). The ODI is a validated questionnaire consisting of 10 sections, each scored from 0 to 5. The total score is converted to a percentage, with higher scores indicating greater disability.	At baseline (single time point)

Collaborators and Investigators

• Sponsor: Fatih Sultan Mehmet Training and Research Hospital
• Investigators: Principal Investigator: Aslinur Keles, MD., PhD, Fatih Sultan Mehmet Training and Research Hospital

Study record dates

Study Major Dates

• Study Start (Actual): August 1, 2024
• Primary Completion (Actual): January 10, 2025
• Study Completion (Actual): May 25, 2025

Study Registration Dates

• First Submitted: June 3, 2025
• First Submitted That Met QC Criteria: July 19, 2025
• First Posted (Actual): July 22, 2025

Study Record Updates

• Last Update Posted (Actual): July 22, 2025
• Last Update Submitted That Met QC Criteria: July 19, 2025
• Last Verified: July 1, 2025

More Information

Terms related to this study

• Keywords: coccydynia; sagittal plane; Coccygeal morphometry; spinopelvic morphometry; os coccygis
• Other Study ID Numbers: 2024/4-4/6

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: undecided

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No