In 1933, the term facet joint syndrome was described as pain induced during twist or rotation of the lumbosacral area [8
]. Nevertheless, radiological findings associated with the clinical diagnosis of facet joint syndrome are absent. Consequently, a block of the medial branch of the dorsal ramus of spinal nerve or a block of the facet joint itself using CT or C-arm fluoroscopy has been performed for the diagnosis and treatment of the disease [2,9,10
]. The use of ultrasonography has recently been increasing in the field of musculoskeletal disorders. It is an advantageous method for dynamically assessing sites on a real-time basis and in cost-effective manner. Ultrasonography has emerged as an alternative method for lumbar facet nerve block using previous diagnostic equipment. However, the accuracy of facet nerve block using ultrasonography has not been proven, and thus its effectiveness is still controversial.
Ultrasonography usage for block procedures was first reported in 1978 by la Grange et al. [11
], which attempted a brachial plexus nerve block using Doppler ultrasound. Afterward, the usefulness of the application of ultrasonography for peripheral nerve block or local anesthesia was reported in several studies [3,12,13
]. In comparison with previous diagnostic devices, ultrasonography attracts attention because of several key advantages. First, there is no exposure to radiation involved. Although the radiation dose during the nerve block by CT or C-arm fluoroscopy is not large, physicians are exposed to many procedures, and thus when the total radiation dose for one year is examined, it becomes more significant, and the risk of irradiation hand damage rises for the surgeons involved [14
]. Lee et al. [15
] reported on a hand lesion that was damaged due to irradiation in this way. Second, additional equipment for protection against radiation is not required and the size of the equipment is small, so it can be moved easily and is thus able to be performed in outpatient clinics. Despite such advantages, the acoustic impedance of bone is high, and thus it does have limitations for imaging spinal structures. In addition, the reproducibility among doctors is low [16
Greher et al. [5
] reported a target point for facet nerve block as a ultrasonographic landmark, which was defined as lying on the upper edge of the transverse process and in the groove at the base of the superior articular process, where the medial branch traverses the upper edge of the transverse process. Ha et al. [6
] performed facet joint block using the spinous process, the lamina, and the facet joint as landmarks. Previous studies have reported relatively high success rates for lumbar facet block using ultrasonography [4-6
]. However, ultrasound-guided identification for facet nerve block has not been fully described. Ha et al. [6
] reported improvement of symptoms after facet joint block, but they did not evaluated needle placement using radiological images in regard to the accuracy of lumbar facet nerve block.
To identify different spinal levels, most previous studies have applied spinous process as ultrasonic landmarks on posterior sagittal sonograms [4-6
]. Yet it is not easy to identify different spinal levels using the spinous process as an ultrasonic landmark. Author's work suggests that ultrasound-guided longitudinal facet view obtained by curved tranducer seems to be a promising guidance technique for identifying different spinal segments. The facet joint is a better ultrasonic landmark for identification of anatomical level compared with the spinous process, and the accurate location could be determined by counting the facet joint from the lumbosacral facet joint toward cephalic direction. This study has reason, therefore, to compare accuracy between the ultrasonography and lumbar facet nerve block. Eighty-seven segments (91.6%) could be guided successfully for facet nerve block by ultrasound.
The limitations of this study were as follows; firstly, there was 8.4% failure rate of the accuracy of lumbar facet nerve block using ultrasound guidance. To overcome this problem, we performed double blocks at the L5 medial branch and L4 medial branch to screen patients for L4-5 facet denervation. There is a dual innervation to each lumbar facet joint. That is, each facet is innervated by the medial branches of the posterior rami of the spinal nerves above and below the joint. Thus, the L4-5 facet is innervated by the L5 medial branch (coursing over the L5 transverse process) and the L4 medial branch (coursing over the L4 transverse process). Facet nerve block using fluoroscopic guidance was repeated if a patient had no improvement in terms of their back pain. A second limitation is that the medial branch of the facet joint was not examined neurologically to assess whether or not the location of the needles was accurate. Further investigation should consider this point, in order to clarify the location of needles more accurately for the medial branch of facet joint.