Ultrasound anatomy of the nerves supplying the cervical zygapophyseal joints: an exploratory study.

BACKGROUND AND OBJECTIVES: Nerve blocks and radiofrequency neurotomy of the nerves supplying the cervical zygapophyseal joints are validated tools for diagnosis and treatment of chronic neck pain, respectively. Unlike fluoroscopy, ultrasound may allow visualization of the target nerves, thereby potentially improving diagnostic accuracy and therapeutic efficacy of the procedures. The aims of this exploratory study were to determine the ultrasound visibility of the target nerves in chronic neck pain patients and to describe the variability of their course in relation to the fluoroscopically used bony landmarks.
METHODS: Fifty patients with chronic neck pain were studied. Sonographic visibility of the nerves and the bony target of fluoroscopically guided blocks were determined. The craniocaudal distance between the nerves and their corresponding fluoroscopic targets was measured.
RESULTS: Successful visualization of the nerves varied from 96% for the third occipital nerve to 84% for the medial branch of C6. The great exception was the medial branch of C7, which was visualized in 32%. The bony targets could be identified in all patients, with exception of C7, which was identified in 92%. The craniocaudal distance of each nerve to the corresponding bony target varied, the upper limit of the range being 2.2 mm at C4, the lower limit 1.0 mm at C7.
CONCLUSIONS: The medial branches and their relation to the fluoroscopically used bony targets were mostly visualized by ultrasound, with the exception of the medial branch of C7 and, to a lesser extent, the bony target of C7. The nerve location may be distant from the fluoroscope's target. These findings justify further studies to investigate the validity of ultrasound guided blocks for invasive diagnosis/treatment of cervical zygapophyseal joint pain.