Ultrasound–CT fusion versus ultrasound guidance for lumbar nerve root block in multilevel lumbar disc herniation: a retrospective comparative cohort study

Ultrasound–CT fusion may improve anatomical orientation during lumbar nerve root block, but its comparative clinical value is uncertain. We compared peri-procedural pain trajectories and workflow between fusion guidance and ultrasound guidance alone in patients with multilevel lumbar disc herniation. This retrospective cohort screened 163 potential patients from January 2023 to June 2024. Of 120 patients who entered a guidance attempt, 115 completed the planned procedure and entered the comparison. All received a unilateral single-target lumbar nerve root block using 3 mL of 1% lidocaine. Routine-care guidance allocation was non-randomised. The principal outcome was the first post-injection, patient-reported leg-pain visual analogue scale (VAS), recorded after completion of injection and before the scheduled 10-min assessment by an independent spine surgeon blinded to the guidance modality. A linear mixed-effects model included group, time, their interaction, baseline VAS, symptom duration, target root and number of herniated levels. Participant-clustered CR2 robust standard errors were used. The analysis included 56 ultrasound-only and 59 fusion-guided procedures. Among 63 planned fusion procedures, first registration succeeded in 55, eight required repeat registration, and final registration succeeded in 60 (95.2%). Three final failures converted to fluoroscopy ( n = 2) or CT ( n = 1), and one patient stopped before injection after successful registration. At the first post-injection assessment, fusion guidance was associated with a lower adjusted VAS score (difference, − 0.87 points, 95% confidence interval [CI], − 1.10 to − 0.64). Differences were not evident at 10 min, 30 min, or 6 months. The fusion group had a 2.48-min longer total procedure time (95% CI, 1.57 to 3.38). No serious complication was recorded. Ultrasound–CT fusion registration was completed in most planned procedures. Fusion guidance was associated with a transiently lower first post-injection VAS score but a longer workflow, without evidence of better later pain or 6-month outcomes. The non-randomised, completed-procedure comparison does not establish diagnostic accuracy or comparative safety. Not applicable. This was a retrospective observational study of routine clinical care.