A dynamic alphanumeric classification system for non-traumatic coccydynia: Further defining clinical and research...

There is a rise in sedentary lifestyle with nearly 1.8 billion adults not meeting the recommended levels of physical activity. This is associated with lengthy sitting hours which is a risk factor that can cause non-traumatic coccydynia. Non-traumatic coccydynia is one of the least understood and challenging diseases. The current classification system is insufficient in finding the cause or forming an effective rehabilitation plan. The study aims to observe coccygeal morphology in the Indian population, compare dynamic sacrococcygeal radiological indices in patients with and without non-traumatic coccydynia, and evaluate the sacropelvic radiological parameters.

A Case-control study was done at tertiary care hospital, 69 participants (33 cases and 36 controls) were enrolled. Main outcome measures were assessed on antero-posterior and dynamic lateral view radiographs of lumbosacral spine with coccyx. These included: coccyx type, subluxation, mobility, measurements of sacrococcygeal-SCA, intercoccygeal-ICA, sacral angle-SA, pelvic tilt-PT, and pelvic incidence-PI. Lacunae in current classification systems led us to propose our dynamic alphanumeric classification which was used to assess the change in type of coccyx on sitting.

Type I coccyx was more common in controls (P = 0.005), type IV & above was more prevalent in cases. Posterior subluxations were statistically significant in cases (P = 0.003). Further using our alphanumeric classification system, change by 1 or more grades on dynamic radiographs is significant in coccydynia (P = 0.003) but change of ≥2 grades was exclusive to non-traumatic coccydynia group.

Nontraumatic coccydynia is a dynamic condition, hence its assessment, classification and treatment should include dynamic radiography. Type III coccyx and higher; change in type of coccyx by ≥ 2 grades; posterior subluxation at the sacrococcygeal/intercoccygeal joint were significantly associated with coccydynia. Sacropelvic parameters were not important causative factors in our study.