CT-guided injection in coccydynia: outcome prediction using MRI findings and CT-injection characteristics

To analyze pain relief for chronic coccydynia after CT-guided, pericoccygeal ropivacaine and triamcinolone injection over time and to investigate possible imaging predictors of successful and maintained pain relief.

In this retrospective study, chronic coccydynia patients receiving CT-guided pericoccygeal injections with ropivacaine and triamcinolone were assessed for pain relief post-injection, using a numeric rating scale (NRS, 0-10) and percentage pain reduction (PPR, %). Patients were followed up until pain recurrence. Two radiologists assessed MRI findings prior to, and contrast distribution during CT injection. Imaging predictors for successful pain relief at 1 month (PPR ≥ 50%) combined with maintained pain relief for at least 3 months post-injection were investigated using logistic regression analysis.

63 patients (mean age 44.6 ± 12.5 years) were evaluated. Average pain dropped from initially 6.3 to 3.0 (average PPR 53.2 ± 37.5%) 15 min post-injection, and to 2.9 (average PPR 55.2 ± 41.4%) one month post-injection (all p < 0.001). One month post-injection, 41 patients (65%) reported PPR ≥ 50%. Pain relief persisted on average for 6 months. Three months post-injection, 32/63 patients (50.8%) reported maintained pain relief. Fluid-sensitive sequence (FSS)-hyperintensity of the sacro-/intercoccygeal synchondrosis, coccyx subluxation and a bony spicule were the only significant predictors (odds ratios: 3.5-5.1) of successful and maintained pain relief (all p ≤ 0.031).

CT-guided pericoccygeal injection with ropivacaine and triamcinolone allowed successful pain relief in 65% of chronic coccydynia patients, with a PPR of 55% and persistence of 26 weeks on average. Odds of successful and maintained pain relief increased with the presence of a bony spicule, subluxation and FSS-hyperintensity of the synchondrosis.

Question Imaging predictors of successful pain relief in chronic coccydynia patients receiving pericoccygeal ropivacaine and triamcinolone injections are unknown. Findings A bony spicule, subluxation, and sacro-/intercoccygeal fluid-sensitive sequence hyperintensity on MRI were significant predictors of successful pain relief for ≥ 3 months. CT-contrast distribution did not influence pain relief. Clinical relevance CT-guided pericoccygeal injections with ropivacaine and triamcinolone offer successful pain relief in chronic coccydynia; the presence of a bony spicule, subluxation, and sacro-/intercoccygeal fluid-sensitive sequence hyperintensity was predictive of pain relief.