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

OBJECTIVES

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.

MATERIALS AND

METHODS

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.

RESULTS

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).

CONCLUSION

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.

KEY POINTS: 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.