Background This study aimed to determine the predictive factors affecting the success of ganglion impar block applied in chronic coccygodynia.

Methods Patients who received ganglion impar block to treat coccygodynia between January 1, 2018 and January 1, 2021 were retrospectively screened. Of the 195 patients, 102 met the final analysis criteria and were included in the study. Demographic data, coccygodynia etiology, coccygodynia symptom duration, history of coccyx fracture, regular opioid use, and presence of other musculoskeletal chronic pain conditions accompanying coccygodynia were obtained from patient records. In addition, coccyx radiography was examined, and coccyx curvature type, permanent subluxation, and posterior spicule presence were evaluated. The criterion for treatment success was set as ≥50% reduction in Numerical Rating Scale pain scores in the third month after treatment.

Results Treatment was successful of the patients in 69.6% (95% CI 60.4% to 78.7%). A significant cut-off value (24.5 months) was determined for coccygodynia symptom duration using receiver operating characteristic analysis. Symptom duration above the cut-off value was defined as prolonged symptom duration. Multivariable logistic regression analysis was performed to determine the predictive factors affecting treatment success in the third month after injection. In the final model, the presence of permanent subluxation (yes vs no), and the prolonged symptom duration (yes vs no) were found to have significant effects on treatment success (OR 9.56, 95% CI 1.44 to 63.40, p=0.02; OR 137.00, 95% CI 19.59 to 958.03, p<0.001).

Conclusion Treatment success of ganglion impar block for coccygodynia is high. However, longer preprocedure symptom duration and the presence of permanent subluxation were associated with a decrease likelihood of treatment success.