FEASIBILITY OF COLOUR DOPPLER ULTRASOUND FOR DETECTION OF INTRAARTICULAR SACROILIAC JOINT INJECTION: A CASE SERIES.

Editor,

We would like to share our experience of colour Doppler ultrasound (CDU) in the detection of correct needle placement for sacroilliac joint (SIJ) injection during interventional procedures for management of low back pain (LBP).

Injection of steroid mixed with local anaesthetic (LA) is a well-recognised method for both diagnostic and therapeutic management of SIJ pain. Several imaging modalities have been used to guide such interventions in SIJ.1 Fluoroscopic guidance is still considered as gold standard to confirm needle placement and spread of the dye. The majority of such imaging techniques involve use of ionising radiation. Ultrasound is however being used increasingly.2 In many interventional pain procedures it is replacing ionising modalities because of the portability allowing the procedure to be performed at bedside without such hazards.3 However, ultrasound has ta potential limitation in viewing the needle trajectory and the spread of the injectate inside the bony SIJ. CDU can overcome this problem by allowing visualisation of the flow of the injectate.4 We thus decided to conduct this case study to find out the utility of CDU.

After obtaining approval from ethical committee and informed consent, 10 adult patients scheduled to undergo SIJ injection were included. After positioning the patients in prone position and using proper aseptic cleaning and draping, a low frequency curvilinear ultrasound transducer was used to localise the target SIJ anatomy. After skin infiltration with LA, a 22-gauge Quincke spinal needle was advanced towards the SIJ under ultrasound guidance. Once the needle was seen to enter the SIJ, colour Doppler mode was activated. A 1.5 mL mixture of steroid and LA was then injected. Positve Doppler signal suggesting the flow within the SIJ along with absence of any overflow outside the bony landmarks were noted (Fig 1). Then an independent observer who was blinded about the study methodology, confirmed the intra-articular placement of the needle fluoroscopically by injecting radioopaque contrast. Efficacy of the injection in providing pain relief, was assessed at follow up.

Fig. 1

Use of color Doppler flow to locate needle placement.

Demographic details of the patients are depicted in Table 1. CDU flow pattern indicated correct intra-articular injection without any extra-articular flow pattern in all our patients. Subsequent fluoroscopy and dye injection also confirmed correct needle placement. Preprocedural visual analog score (VAS) (6.7±1.05) reduced significantly after the injection (2.3±1.03) (p <0.0001) (Table 2) confirming the efficacy of the procedure.

Table 1

Demographic data and Pain scores.

		p value
Age (Years)	55.7±11.81	NA
Male	4	NA
Female	6	NA
Pre-Procedure VAS score	6.7±1.05	<0.0001
Post-Procedure VAS Score	2.3±1.03

VAS: Visual Analog Score. Data expressed as mean±standard deviation or discrete variables wherever application.

Table 2

Techniques used for needle placement and confimation of that.

	Intra-articular Doppler Flow Signal	Extra-Articular Doppler Flow Signal	Subsequent Fluoroscopic Confirmation of Needle Placement
US Doppler Guided Needle placement	Detected in all cases	Not detected in any case	Intra-articular needle placement confirmed in all cases using radioopaque dye.

In this case series, we found that CDU can be used successfully to confirm correct intra-articular placement of needle and subsequent injectate in SIJ.

This utility of CDU has not been reported to date. Arslan et al. used duplex and colour Doppler ultrasound to demonstrate vascularity inside and around the SIJ to diagnose sacroilitis and to monitor the therapeutic response, but they did not perform any SIJ injection using ultrasound.5

We thus strongly propose a well powered randomised controlled trial on this.