Noninferiority of ultrasound-guided lumbar disc block versus fluoroscopy-controlled lumbar discography for diagnosis of discogenic low back pain

Abstract

Introduction: Evaluation of ultrasound (US)-guided disc block used to diagnose discogenic pain, as described in case reports. The study aimed to ascertain the noninferiority of US-guided lumbar disc block to conventional discography in the diagnosis of discogenic low back pain (DLBP).

Material and methods: The reports of 418 patients undergoing lumbar fusion for DLBP were stratified into a US group receiving US-guided lumbar disc block and a control group receiving fluoroscopy (FL)-assistant discography via a propensity-score matched method in a 1 : 1 ratio. The primary endpoint was the confirmatory rate defined as the rate of clinical success following surgery measured by a numerical pain rating scale score ≤ 2 and an Oswestry Disability Index score ≤ 15 at the 1-month follow-up point. Secondary outcomes included needle insertions until contrast given, procedure time, radiation dosages and adverse events.

Results: The confirmatory rates for disc block and discography were 71.8% and 73.2% (difference = -1.3%, 95% confidence interval [CI]: -9.9%, 7.2%, P = 0.353). The lower bound of 95% CI did not cross the noninferiority margin of 10%. There were fewer needle insertions (median 2, IQR: 1-3 vs. 5, IQR: 4-6, P < 0.001), shorter procedure times (8.94 ± 2.28 vs. 16.13 ± 3.39 min, P < 0.001) and lower radiation dosage (1689.56 ± 898.54 vs. 8293.50 ± 1039.09 μGy m² , P < 0.001) in the US group than the control group. No serious adverse events were observed.

Conclusions: US-guided lumbar disc block was not inferior to conventional discography as a diagnostic modality in the evaluation of DLBP being considered for surgery. Given that the sonographic method provided advantages in terms of facilitation of needle insertion, reduced procedure time, and attenuated radiation exposure, it might be an alternative option for surgery decision making.

Keywords: complication; disc block; discogenic low back pain; discography; radiation exposure; ultrasound.

FIGURE 1

Study flow diagram

FIGURE 2

Photograph showing the ultrasound (US)-guided lumbar disc block with fluoroscopy verification. A) The long axis of the facet joints was visualized by placing the US transducer from the midline to the lateral. B) The short-axis image showing the hyper-echoic bony cortex with its acoustic shadowing beneath consisted of the superior articular process (SAP) of L5 and the transverse process (TP) of L5. C) The trajectory of the needle was directed towards the center of the interlaminar space, passing just posterior to the root of the SAP of L5, identified as the “camel’s hump” sign on the transverse US scan, until the TP of L5 just disappeared from view. Fluoroscopic anteroposterior (D) and lateral view (E) verified intradiscal contrast dispersion in disc L4/5 following the US-guided approach

FIGURE 3

Numeric rating scale (NRS) pain scores and Oswestry Disability Index (ODI) scores in both groups over time. Significant reductions in NRS scores (A) and ODI scores (B) after lumbar fusion surgery were observed, compared to the baseline value. There were no between-group differences at the 7-day and 1-month follow-up point