Contralateral lower limb radiculopathy by extraforaminal disc herniation following oblique lumbar interbody fusion in degenerative lumbar disorder: illustrative cases

Abstract

BACKGROUND

Contralateral lower limb radiculopathy is a potential early complication of oblique lumbar interbody fusion (OLIF) in degenerative lumbar disorders. Among several pathologies related to contralateral radiculopathy following OLIF, extraforaminal disc herniation during the OLIF procedure is very rare.

OBSERVATIONS

Case 1 is a 68-year-old male underwent L4–5 and L5–6 OLIF for recurrent lumbar canal stenosis–expressed right leg pain and muscle weakness after surgery. Case 2 is a 76-year-old female on whom L4–5 OLIF was performed for L4 degenerative spondylolisthesis and who presented right leg pain and numbness postoperatively. In both patients, OLIF cages were inserted into the posterior part of the disc space or obliquely and the extraforaminal extruded disc compressed opposite exiting nerve roots (L5 root in case 1 and L4 root in case 2) as shown on magnetic resonance imaging (MRI). Surgical decompression with discectomy was required for pain relief and neurological improvement in both cases.

LESSONS

When emerging from new-onset opposite limb radiculopathy attributed to the OLIF procedure, extraforaminal disc herniation should be considered a potential pathology and MRI is useful for early diagnosis and selecting a subsequent management, including surgery.

In the past decade, oblique lumbar interbody fusion (OLIF) has become a popular surgical procedure to address degenerative lumbar spine disorders with many advantages, such as shorter operative time, less blood loss, less muscle damage, indirect decompression, powerful correction of sagittal and coronal alignment, and avoidance of dural tear and neurological complications.

Among various perioperative complications related to the OLIF procedure (i.e., vascular injuries, anterior thigh pain/numbness, peritoneal tear, ileus, and ureter injury), neurological complications including lumbar plexus injury with sensorimotor deficit have been reported as being rare and the incidence in OLIF seems less than in the transpsoas approach (extreme lateral interbody fusion [XLIF]).

Contralateral lower limb radiculopathy is uncommon compared with ipsilateral neurological complications on the approach side; however, it may be a potential neurological complication following lateral interbody fusion both in OLIF and XLIF.

Although so far, several etiologies of contralateral radiculopathy have been supposed in the literature, limited data are available on its incidence, underlying pathologies, and strategies for management and prevention.

Here, we present 2 cases of contralateral lower limb radiculopathy by extraforaminal extruded disc herniation during the OLIF procedure and inspect the pathology and technical demands for avoidance.

Illustrative Cases

Illustrative Case 1

A 68-year-old male with a history of decompression surgery at L4–5 and L5–6 for lumbar canal stenosis has complained of recurrent left lateral leg pain and numbness and intermittent claudication for the past 2 years. Lumbar radiography showed mild degenerative scoliosis, L4 anterior and L5 posterior spondylolisthesis, and previous fenestration at L4–5 and L5–6 (Fig. 1A and B). Magnetic resonance imaging (MRI) confirmed spinal canal stenosis from the lateral recess to the extraforaminal space at these levels (Fig. 1C–E). He underwent spinal fusion with OLIF combined with percutaneous pedicle screw fixation at both levels, and his left leg pain and numbness disappeared immediately after surgery (Fig. 2A and B). However, newly, he felt right leg pain, numbness, and motor weakness in L5 dermatome and innervated muscles (Manual Muscle Test: 2/5 in the tibialis anterior, peroneus longus, and extensor hallucis longus). An OLIF cage of L5–6 was inserted into the posterior part of the disc space (a center of the OLIF cage was located at 55% from the anterior edge of the disc space on sagittal radiography) and rotated 10 degrees posteriorly. MRI revealed an extraforaminal large disc herniation, which compressed the right exiting nerve root (L5 dorsal root ganglion; Fig. 2C). Surgical decompression with discectomy was executed 1 week later (Fig. 2D). Pain relief was immediate and recovery of the neurological deficit was achieved within a few months.

FIG. 1.

Preoperative anteroposterior (A) and lateral (B) radiographs showing mild degenerative scoliosis and grade I spondylolisthesis at L4–5. Preoperative sagittal (C) and axial T2-weighted magnetic resonance (MR) images of L4–5 (D) and L5–6 (E) showing spinal canal stenosis from the lateral recess to the extraforaminal space.

FIG. 2.

Postoperative anteroposterior (A) and lateral (B) radiographs showing posterior placement of the OLIF cage at L5–6. Postoperative axial MR images showing oblique placement of the cage and an extraforaminal disc herniation (arrow), which compressed the right L5 nerve root (C). MR images after discectomy showing complete disappearance of the herniation mass (D).

Illustrative Case 2

A 72-year-old female had complained of severe left leg pain, numbness, and intermittent claudication (within 100 m) due to L4 degenerative spondylolisthesis with severe central and foraminal spinal canal stenosis (Fig. 3). She underwent surgery for L4–5 OLIF, direct decompression by laminectomy, and pedicle screw fixation at the same level (Fig. 4A and B). Although her symptoms decreased soon after the operation, she newly complained of intolerable right medial leg pain, numbness, and gait disturbance. An OLIF cage of L4–5 was inserted into the posterior part of the disc space (a center of the OLIF cage was located at 60% from the anterior edge of the disc space on sagittal radiography) and in the orthogonal direction to the transverse axis. MRI presented an extraforaminal extruded large disc compressing the right exiting nerve root (L4 dorsal root ganglion; Fig. 4C and D). Two weeks later, open discectomy through the Wiltse paraspinal approach was performed and her pain and numbness on the right side disappeared (Fig. 4E).

FIG. 3.

Preoperative anteroposterior (A) and lateral (B) radiographs showing degenerative grade I spondylolisthesis at L4–5. Preoperative sagittal (C) and axial T2-weighted MR images of L4–5 (D) showing severe central and foraminal spinal canal stenosis.

FIG. 4.

Postoperative anteroposterior (A) and lateral (B) radiographs showing posterior placement of the OLIF cage at L4–5. Postoperative axial MRI showing an extraforaminal disc herniation (arrow), which compressed the right L4 nerve root (C and D). MRI after discectomy showing complete disappearance of the herniation mass (E).

Discussion

Observations

OLIF is a minimally invasive lumbar interbody fusion through a retroperitoneal prepsoas approach, which was developed by Mayer¹ in 1997 and has evolved with the use of a tubular retractor by Davis et al.² since 2011. Access to the lumbar disc spaces of L1 to L5 is through an anterolateral corridor between the aorta and the left psoas muscle.

Multiple articles revealed that the XLIF had a considerable risk of ipsilateral lumbosacral plexus injury on the approach side attributed to dissecting a psoas muscle (transpsoas approach)^3–6 and the postoperative neurological complication rate was reported as 36.1% in transient (sensory deficits, 17.1%; motor deficits, 14.1%) and 4% in permanent deficits.⁷

Although an OLIF procedure was described to have a lower risk of ipsilateral lumbar plexus injury compared with XLIF because of the anterior to psoas approach, which can avoid involving the lumbar plexus within the psoas muscle (sensory deficits, 5.1%–13.8%; motor deficits, 0%–4.3%),^8–10 contralateral lower limb radiculopathy seems to occur in an equal incidence both in OLIF and XLIF. Limited literature referred to a postoperative contralateral radiculopathy following the lateral interbody fusion and the incidence was noted as 0.4%–9.3% in the collected nine English-language papers to date.^8,11–18

Several pathologies, such as contralateral extraforaminal disc herniation,¹⁶ fracture of the opposite vertebral osteophyte and endplate,^13,14,16 posterior oblique malposition of the OLIF cage,^{8,11,12,14,17,18} insertion of an excessively wide cage, foraminal stenosis following inappropriate vertebral translation,¹² aggressive curetting of the disc with breaking opposite annulus, and hematoma in the opposite psoas muscle, may cause direct compression or injury to the opposite exiting nerve root. Moreover, overstretch of the nerve root by excessive lift-up of the disc height with a tall cage may cause contralateral radiculopathy.¹²

Among 32 reported cases and the present 2 cases (total of 34 cases) of contralateral radiculopathy following OLIF and XLIF, direct compression injury to the opposite exiting nerve root was established in 9 OLIF and 7 XLIF cases and overstretch of the nerve root was inferred in 1 OLIF case. Contralateral radiculopathy due to extraforaminal disc herniation was seen only in 3 cases (2 present cases in OLIF and 1 case in XLIF¹⁶) and seems very rare as a cause.

The etiology of contralateral radiculopathy was defined in less than half of cases, and in others, an etiology remained unknown. Repeat surgery was performed in 13 of 34 cases to relieve contralateral limb symptoms.^{8,11,13,14,18}

In the present 2 cases, preoperative chief complaints, lateral left leg pain and numbness, disappeared immediately after surgery; however, new-onset contralateral right leg pain with motor weakness emerged postoperatively. Thus, MRI and computed tomography of the lumbar spine were performed immediately, and an extraforaminal large extruded disc without bony fragments was identified to compress the opposite exiting nerve root, which did not exist on preoperative images in both cases. OLIF cages were inserted into the posterior part of the disc space on the sagittal plane (a center of the cage located at 55% from the anterior disc edge in case 1 and at 60% in case 2) and, in addition, rotated 10 degrees posteriorly in case 1. Thus, the tip of the OLIF cages was located just before the right exiting nerve roots at the foraminal outlet. These situations suppose that extraforaminal disc herniation might have occurred during either step of OLIF procedures—that is, during curetting disc cartilage or during insertion of a Cobbs elevator, trial, and OLIF cages. Incomplete curettage of the opposite disc and severe degeneration of the annulus may easily lead to iatrogenic disc herniation during an intradiscal maneuver.

The sagittal position and rotation angle of the inserted OLIF cage are considered critical to avoid direct exiting nerve root injury. An ideal location of the OLIF cage is proposed to be in an anterior part of the disc space, at the junction of the anterior one-third and posterior two-thirds in the sagittal plane and in an orthogonal direction to the transverse axis of the disc, to prevent a cage inserting toward the opposite posterolateral corner of the disc space.¹⁴

During several steps of the OLIF procedure, sufficient resection of disc tissues especially at the opposite posterolateral corner, gentle distraction of narrow and slipped disc space, orthogonal maneuver of all instruments, insertion of the OLIF cage into the anterior portion of the disc space, and selection of the appropriate cage width and height are essential for avoiding contralateral radiculopathy by potential etiologies including extraforaminal disc herniation to maximize many advantages derived from the MIS procedure of OLIF.

Lessons

When emerging from a new-onset opposite limb radiculopathy just after the OLIF procedure, extraforaminal disc herniation should be considered a potential pathology, and MRI is an essential imaging tool for discriminative diagnosis and selecting a subsequent management including surgery. Adequate curetting of disc tissues, gentle handling of surgical tools, and orthogonal insertion of an appropriately sized cage into the anterior disc space are required for the avoidance of procedure-related complications.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: both authors. Acquisition of data: Hattori. Analysis and interpretation of data: Hattori. Drafting of the article: Hattori. Critically revising the article: Hattori. Reviewed submitted version of the manuscript: Hattori. Approved the final version of the manuscript on behalf of both authors: Hattori. Statistical analysis: Hattori. Administrative/technical/material support: Hattori. Study supervision: Hattori.

Supplemental Information

Previous Presentations

These 2 illustrative cases were presented at the 51st Annual Meeting of the Japanese Society for Spine Surgery and Related Research in the poster session on April 21, 2022 (in Yokohama, Kanagawa, Japan).