Background Facet joint-mediated pain has been identified as a common cause of lumbar pain. Steroid injections are currently made to treat them, they are usually performed under fluoroscopy or computed tomography guidance. Ultrasound (US) is also appropriate to study facet joints and some studies showed feasibility and efficacy of facet joint injections performed under US-guidance through a transversal approach. On a longitudinal view, facet joints are easy-to-identify as a series of lumps with the joint capsule appearing as a thin hypoechoic line that envelops the joint.
Objectives Considering the good visibility of these joints and their capsule on the longitudinal view, we studied the feasibility of US-guided facet joint injections using a longitudinal inline approach.
Methods Patients referred to our rheumatology department to receive facet joint injections under fluoroscopy were included. To realize the injection, we first located the accurate lumbar level on a longitudinal median view going through the spinous processes. Facet joints were identified as previously described placing the probe 2–3 cm away from the median line. Then, the needle was inserted to reach the hypoechoic line corresponding to the capsule or, if not visible, the top of the lump formed by the inferior articular process of the superior vertebra overlying the superior articular process of the vertebra below it. When we obtained the bone contact, we injected iodinated contrast medium followed by cortivazol. Finally, we made a lumbar X-ray to analyze the needle position and the quality of the arthrography.
The first objective was to assess the number of injections realized in front of the joint. For secondary objectives, we assessed the number of accurate arthrography, the duration of the procedure and the occurrence of adverse events. During US examination, the visibility of the capsule and the presence of osteophytes were collected.
Results Thirty-eight patients have been included by two operators. We excluded four patients because of a poor visibility of the spinal structures. Mean age was 58,4 years (range, 30–82) and mean BMI was 25,2 kg/m2 (range, 18–34). US showed osteophytes in 42% and the joint capsule was inconstantly visible (25%). One-hundred and forty-four injections were performed (72 at the L4-L5 level and 72 at the L5-S1 level) and 141 X-ray were analyzed. One-hundred and twenty-three injections (87%) were accurately realized in front of the joint, i.e. in front of the inferior articular process of the superior vertebra. However, a proper arthrogram was obtained in only 35 cases (25%). Mean procedure duration was 8.5 minutes for four injections. Six patients (18%) reported transient pain exacerbation and no severe complication occurred during the first month after the procedure.
Conclusions With a longitudinal inline approach, US-guided facet joint injections were feasible and 87% injections were realized right in front of the joint. However, we obtained a correct arthrogram in only 25%. The depth of the target-point, the inconstant visualization of the capsule and the obliquity of the needle probably explain this result. Additional studies will be necessary to improve the accuracy of the technique.
Disclosure of Interest None declared