Ultrasound-guided retro-neural transforaminal injection with fluoroscopic confirmation for zoster-associated pain: a retrospective propensity score-matched analysis.

OBJECTIVES

This study aimed to evaluate the efficacy and safety of an ultrasound (US)-guided lumbar transforaminal steroid injection (TFI) using the retro-neural approach for relieving acute zoster-associated pain (ZAP) in the lower extremities.

METHODS

A total of 72 patients who underwent US-guided retro-neural TFI were retrospectively stratified as the US cohort. Furthermore, 1:1 propensity score matching was performed to select controls who underwent fluoroscopy (FL)-guided procedures. The primary endpoint was visual analog scale (VAS) pain scores at 1 month after the procedure. Secondary outcomes included sensory blockade, procedure duration, radiation exposure, adverse events, rescue analgesic use, post-herpetic neuralgia (PHN) incidence, and European Quality of Life Five-Dimension questionnaire (EQ-5D) score.

RESULTS

At 1 month, the US cohort reported a mean VAS score of 33.52 ± 14.30 mm with a mean difference of 1.04 mm compared to the FL cohort, indicating non-inferiority as the upper limit of the 95% confidence interval of 4.36 mm fell within the non-inferior margin of 10 mm. PHN occurred in 16.7% and 13.9% of cases in the US and FL cohorts at 3 months after rash onset (p = 0.796), respectively. Both cohorts showed similar improvements in 3-month VAS scores (p = 0.310), rescue analgesics (all p > 0.05), and EQ-5D scores (all p > 0.05). Compared to the FL cohort, the US approach was associated with a wider anesthetic dermatome [3.25 (IQR: 2.75, 3.75) vs. 3 (IQR: 2.5, 3.5) levels for 3 mL of therapeutic injectate, p = 0.031], fewer needle insertions [1 (IQR: 0, 2) vs. 2.5 (IQR: 1.5, 3.5), p = 0.005], shorter procedure duration (14.09 ± 3.58 vs. 19.70 ± 4.84 min, p < 0.001), and less radiation exposure (1,226.89 ± 377.28 vs. 5,607.50 ± 1,391.38 µGy·m2, p < 0.001). No serious adverse events were observed.

CONCLUSIONS

US-assisted lumbar retro-neural RFI was statistically non-inferior to conventional procedures under FL guidance for treating ZAP in the lower extremities. It provided the benefits of fewer needle attempts, a shorter procedure duration, and decreased radiation exposure, supporting its use in clinical routine practice.