Predictors of outcomes of conservative management in chronic coccydynia - Results from a prospective clinicoradiological observational study.

Study background: Chronic coccydynia is a difficult pathology to treat due to limited understanding of the etiology and risk factors. Aim of the study was to analyse the clinical and radiological factors associated with poor outcomes in coccydynia. Study design: Prospective observational study. Methods: Patients who visited the spine outpatient department between September 2019 to August 2021 with coccygeal pain of more than two months were included in the study. Lateral radiographs in seated and standing position were done to evaluate their Intercoccygeal angle (ICA), Sacrococcygeal angle (SCA), Basal Angle (BA) and Coccygeal Length. MRI was done for patients who were not relieved with 2 months of conservative treatment. Baseline VAS and ODI scores were documented at the first visit and at six months follow-up to evaluate the outcomes. Results: 168 patients were included - 106 females and 62 males (M:F ratio 1.76) with a mean age of 41.71 years. 109 out of 168 (64.9 %) were obese and 31(18.5 %) were overweight. Type 2 and 4 coccyges were the most commonly seen morphology (67 patients each). Traumatic coccydynia had a better outcome with a mean VAS score of 3.54 compared to 4.36 in the idiopathic group(p < 0.05). Higher Intercoccygeal angle (ICA) was the only radiographic parameter that had coorelation with the outcomes. Mean ICA in good outcomes group was 34.8° (13.2) compared to 42.1° (14.6) in those with poor outcomes(p < 0.05). All 7 patients with pseudoarthrosis had VAS scores reduction of more than 50 %. Conclusion: Type 2 and type 4 were the most common coccyx morphology encountered in patients with chronic coccydynia. Outcomes were better in traumatic group compared to idiopathic group and in those with pseudoarthrosis on MRI. Higher Intercoccygeal angle(ICA) was the only radiographic parameter associated with poor outcome of conservative management.