The Surgical Anatomy of Lumbar Medial Branch Neurotomy (Facet Denervation)

University of Otago, Taieri, Otago, New Zealand
Pain Medicine (Impact Factor: 2.3). 10/2004; 5(3):289-98. DOI: 10.1111/j.1526-4637.2004.04042.x
Source: PubMed


To demonstrate the validity of placing electrodes parallel to the target nerve in lumbar radiofrequency neurotomy.
Previous data on the anatomy of the lumbar dorsal rami were reviewed and a demonstration cadaver was prepared. Under direct vision, electrodes were placed on, and parallel to, the L4 medial branch and the L5 dorsal ramus. Photographs were taken to record the placement, and radiographs were taken to illustrate the orientation and location of the electrode in relation to bony landmarks.
In order to lie in contact with, and parallel to, the target nerve, electrodes need to be inserted obliquely from below, so that their active tip crosses the neck of the superior articular process. At typical lumbar levels, the tip should lie opposite the middle two quarters of the superior articular process. At the L5 level, it should lie opposite the middle and posterior thirds of the S1 superior articular process.
If electrodes are placed parallel to the target nerve, the lesions made can be expected to encompass the target nerves. If electrodes are placed perpendicular to the nerve, the nerve may escape coagulation, or be only partially coagulated. Placing the electrode parallel to the nerve has a demonstrated anatomical basis, and has been vindicated clinically. Other techniques lack such a basis, and have not been vindicated clinically. Suboptimal techniques may underlie suboptimal outcomes from lumbar medial branch neurotomy.

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    • "Therefore, the multifidus inserting the same spinous process received innervation from the same medial branch of dorsal ramus, with a same segmental number of the spinous process, even if the origins of multifidus were different [21]. And then, each of the L1-L5 medial branches sent innervating nerves to multifidus via its dorsal surface at each midlamina, or mid-spinous process level of the vertebra with one level below the segmental number of dorsal ramus [6,15,20-22]. For instance, the fascicles of multifidus arise from the spinous process of L4 vertebra are innervated by L4 medial branch around the dorsal surface of L5 midlamina level, and the fascicles of multifidus arise from the spinous process of L5 vertebra are innervated by L5 medial branch around the dorsal surface of S1 midlamina level. "
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    ABSTRACT: To identify the correlations between the location of multifidus atrophy and the level of lumbar radiculopathy. Thirty-seven patients who had unilateral L4 or L5 radiculopathy were divided into 2 groups; the L4 radiculopathy (L4 RAD) group and the L5 radiculopathy (L5 RAD) group. Bilateral lumbar multifidus muscles at the mid-spinous process level of L4 vertebra (L4 MSP), the mid-spinous process level of L5 vertebra (L5 MSP), and the mid-sacral crest level of S1 vertebra (S1 MSC) were detected in T1 axial magnetic resonance imaging. The total muscle cross-sectional area of multifidus muscles (TMCSA) and the pure muscle cross-sectional area of multifidus muscles (PMCSA) were measured by a computerized analysis program, and the ratio of PMCSA to TMCSA (PMCSA/TMCSA) was calculated. There were no significant differences in TMCSA between the involved and the uninvolved sides in both groups. PMCSA was only significantly smaller at the S1 MSC on the involved side as compared with the uninvolved side in the L5 RAD group. The ratio of PMCSA to TMCSA was the lowest at the L5 MSP on the involved side in the L4 RAD group and at the S1 MSC on the involved side in the L5 RAD group. Our findings suggest that the most severe atrophy of multifidus muscle may occur at the mid-spinous process or mid-sacral crest level of the vertebra which is one level below the segmental number of the involved nerve root in patients with a single-level, unilateral lumbar radiculopathy.
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    • "It is innervated by the medial branch of L4 and the dorsal ramus of L5. The L5 dorsal ramus courses along a groove formed between the base of the S1 superior articulating process and the sacral ala [23, 26] (Fig. 1). "
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