Pros of the contralateral (over-the-top) approach to intra/extraforaminal lumbar disc herniations at the L5-S1 level

INTRODUCTION

There is a 7–12% incidence of intra/extraforaminal lumbar disc herniations (IELDH).[1] One out of five patients will require surgery. Multiple operative approaches have been suggested for resection of IELDH. These include the unilateral interlaminar approach (warranting varying degrees of facet joint removal),[2,6,8] the transmuscular extraforaminal procedure,[4] various endoscopic approaches,[7] the endoscopic transiliac procedure, and the contralateral interlaminar approach.[8] Here, we have specifically focused on the safety/efficacy of the contralateral interlaminar approach to L5-S1 intra/extraforaminal L5-S1 disc herniations that critically avoid disrupting/removing none of a normal facet, or <30% of a spondylotic facet joint, thus averting instability. We treated all patients with FELDH at the L5-S1 level, with preforaminal discs with/without extension into the spinal canal, or for patients with purely intraforaminal discs, utilizing the contralateral interlaminar approach [Figures 1-4].

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Figure 1:: (a) The presurgical T2 axial MRI arrow showed an extraforaminal disc herniation at the L5-S1 level with compression of the L5 root (white arrow). (b) The postsurgical T2 axial MRI images showed the disc herniation removed without violation of the facet joint (white arrow).

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Figure 2:: (a) The presurgical T2 axial MRI image and white arrow pointed to the left extruded disc herniation and (b) the presurgical T2 axial MRI showed a yellow arrow pointing to a purely intraforaminal disc herniation. (c) The postsurgical axial T2 MRI images showed removal of the left extruded disc herniation and (d) the postsurgical axial T2 MRI images showed the right intraforaminal disc herniation removed without facet violation.

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Figure 3:: (a) The axial MRI images show a preforaminal and intraforaminal disc herniation (white arrow). (b) The sagittal T2 MRI showed cranial extension of the disc herniation (white arrow).

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Figure 4:: (a) On the presurgical axial T2 MRI images at the L3-L4 level, the white arrow showed the correct extraforaminal trajectory indicating there would be no need for facet joint drilling, (b) the presurgical axial T2 MRI images at the L4-L5 level that included measurement of the facet joint complex, indicated possible facet joint removal, would be necessitated with an extraforaminal approach (i.e., 22.7 mm and 9.2 mm). Note, the white arrow indicated the appropriate extraforaminal trajectory, (c) on the presurgical sagittal T2 MRI, the white arrows pointed to an intraforaminal disc herniation at the L3-L4 and L4-L5 levels.

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Results of the contralateral interlaminar approach

As noted, contralateral IELDHs at L5-S1 typically require no facet resection, or <30% of facet joint removal if significant spondylosis is present. This procedure affords adequate decompression of the foraminal/far lateral nerve root, thus enabling safer removal of the extrinsically compressing disc herniation without damaging the nerve root itself [Table 1]. [2,8] Therefore, in summary, this approach at the L5-S1 level to IELDH provides adequate exposure of the L5 intraforaminal/extraforaminal nerve root for the careful removal of these disc herniations without risking damage to the nerve root, or significantly compromising the ipsilateral facet joint and, thus, stability, compared to the ipsilateral approach [Figures 5 and 6].

Table 1:: Focused literature review for surgical techniques to remove intraforaminal/extraforaminal lumbar disc herniations.

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Figure 5:: The ipsilateral approach to an intraforaminal herniated lumbar disk does not require exposure below the spinous process. However, it is limited laterally by the facet joints, thus making part of the disc herniation not directly/readily accessible. The red arrow indicated the surgical trajectory. The black lines delimitate the initial surgical exposition to approach the hernia. (Figure 5 by Dr-Andrea Ciuffi).

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Figure 6:: The contralateral approach allows for the development of a surgical corridor below the spinous process that with appropriate angulation between the dural sac and the distal facet joints, allows for direct access to the intraforaminal herniated disk. The red arrow indicated the surgical trajectory. The black lines delimitate the initial surgical exposition to approach the hernia. (Figure 6 by Dr. Andrea Ciuffi).

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ALTERNATIVE APPROACHES TO INTRAFORAMINAL/EXTRAFORAMINAL LUMBAR DISC HERNIATIONS

CONCLUSION

There are multiple pros and cons for the different alternative approaches to resect IELDH. The ipsilateral interlaminar or the unilateral full facetectomy approaches, respectively, require partial versus total facet joint resection, and increase the risk of postoperative spinal instability.[7,8] The intertransverse route often requires too much medial/lateral facet removal that weakens the pars interarticularis making it more susceptible to fracture, and therefore, instability. Wiltse’s purely extraforaminal approach does not typically adequately access more proximal foraminal discs herniations, and thus has more limited applicability. As discussed here, uniquely for L5-S1 intraforaminal/extraforaminal discs herniations, the contralateral interlaminar approach is optimal. It either warrants no facet resection, or at most in the presence of significant spondylosis <30% medial facet removal. The resultant adequate visualization foraminally/ far laterally exiting nerve root allows for safer exposure and removal of the IELDH.