Case Report on Contralateral Neural Complications following OLIF

Summary

We report a rare case of contralateral L4 nerve root compression following oblique lumbar interbody fusion (OLIF). Imaging confirmed the impingement was caused by cage malposition and a fractured osteophyte. Urgent transforaminal lumbar interbody fusion (TLIF) revision successfully decompressed the nerve, resulting in complete neurological recovery.

Abstract

Oblique Lumbar Interbody Fusion (OLIF) is widely used minimally invasive techniques for lumbar degenerative diseases. While neurological complications are recognized, they predominantly affect the ipsilateral lumbar plexus. Contralateral L4 nerve root compression is an exceptionally rare and often overlooked complication, with limited understanding of its biomechanical mechanisms and sparse radiological evidence linking symptoms to specific causes. A 61-year-old female underwent L3/4 and L4/5 OLIF via a left retroperitoneal approach for degenerative spondylolisthesis and spinal stenosis. Postoperatively, she developed right lower extremity pain and quadriceps weakness. Imaging revealed a malpositioned interbody cage and a fractured L4 osteophyte fragment compressing the contralateral L4 nerve root. Revision surgery via a transforaminal lumbar interbody fusion (TLIF) approach successfully removed the fragment and decompressed the nerve, leading to complete symptom resolution at 5-month follow-up. This case provides direct radiological and intraoperative confirmation of contralateral L4 nerve root compression due to cage malposition and osteophyte fracture—a rarely documented mechanism. Contributing factors likely included asymmetric cage placement and potential patient positioning inaccuracies. The report underscores the importance of precise surgical techniques, including rigorous fluoroscopic verification, optimal patient positioning, and consideration of intraoperative navigation to prevent such complications. Prompt postoperative imaging and timely intervention are crucial for managing unexpected neurological deficits. This case demonstrates that timely revision surgery successfully resolved the contralateral neurological deficits, resulting in complete functional recovery at 5-month follow-up. Enhanced awareness and adherence to preventive strategies can significantly reduce the incidence of this serious, yet preventable, complication in lateral access lumbar surgery.

Introduction

Oblique Lumbar Interbody Fusion (OLIF) is a recognized minimally invasive approach for the management of lumbar degenerative diseases¹. The advantages of this approach, such as decreased intraoperative blood loss, preservation of posterior musculature, and expedited recovery, have led to its increasing popularity^2,3,4. Neurological complications continue to be a significant concern linked to this approach^5,6. Most reported cases involve the ipsilateral lumbar plexus and are generally transient, resulting from psoas retraction, instrumentation, or stretch-related neurapraxia^7,8. Contralateral L4 nerve root involvement is notably rare and frequently overlooked in clinical practice and the literature⁹.

Prior research has predominantly concentrated on ipsilateral neuropathies, highlighting established mechanisms including prolonged psoas manipulation and excessive retraction pressure^10,11. Reports of contralateral L4 nerve root compression are limited, and the biomechanical mechanisms involved are not well understood¹². Hypothesized contributing factors, including asymmetric or oblique cage placement, improper patient positioning, and inaccurate fluoroscopic alignment, are seldom supported by direct radiological evidence that connects them to nerve compression¹³. The existing gap in literature has restricted awareness and impeded the formulation of targeted preventive strategies⁴.

This report presents a rare instance of radiologically confirmed contralateral L4 nerve root compression subsequent to OLIF, establishing a direct causal relationship through clinical, imaging, and intraoperative correlation. This study clarifies the mechanical mechanisms involved and outlines essential preventive strategies, focusing on precise patient positioning, stringent fluoroscopic monitoring, and the application of intraoperative navigation. Additionally, we examine principles for postoperative management, emphasizing the importance of timely diagnosis and intervention. This experience is shared to enhance awareness of this preventable complication and to emphasize the necessity of precision and vigilance in all phases of minimally invasive spinal fusion.

Case Presentation:
A 61-year-old female presented with a 3-year history of recurrent low back pain accompanied by bilateral calf pain, which had suddenly worsened over the past 3 months without an apparent cause. Preoperative functional assessments revealed a Visual Analog Scale (VAS) score of 7/10 for back pain and 6/10 for leg pain, with an Oswestry Disability Index (ODI) of 62%. Physical examination revealed obvious tenderness and a step-like feeling at the L4-5 level. Neurological examination prior to surgery was unremarkable, with full motor strength (5/5) in bilateral lower extremities, intact sensation to light touch and pinprick, and normal deep tendon reflexes. Plain X-ray images of the lumbar spine revealed mild forward slippage of L4, which manifested as instability in the lumbar dynamic position, scoliosis, and degenerative change with osteoporosis. Lumbar MRI showed an I-degree spondylolisthesis of L4 and spinal canal stenosis at the L3/4 and L4/5 levels (Figure 1). The diagnosis was lumbar instability accompanied by L4 degenerative spondylolisthesis (I degree) and spinal canal stenosis. Strict conservative treatment for more than 3 months was unsuccessful, and oblique lateral lumbar interbody fusion was necessary. She underwent a lateral interbody fusion (L3/4 and L4/5) through a left retroperitoneal approach under general anesthesia (Figure 2A,B). Immediately postoperatively, she gradually started complaining of right lower extremity pain accompanied by right weakness of the quadriceps muscle. CT showed the L4 osteophyte fracture and a small bone fragment located in the right neural foramen of L4/5 level (asterisks; Figure 2F). The patient returned to the operating room 3 days after the first operation and underwent a TLIF on the right at L4/5 and posterior fixation (Figure 3A,B). More specifically the fractured osteophyte was found to compress the L4 nerve root and was removed uneventfully (Figure 3C). Postoperatively, the aching pain disappeared, and the numbness improved, allowing her to ambulate without pain. At the 5-month follow-up, her back pain and right calf numbness had completely resolved. This clinical improvement was reflected in her functional scores: the VAS score for back pain decreased to 1/10, the VAS score for leg pain decreased to 1/10, and the ODI improved significantly to 12%.

Diagnosis, Assessment, and Plan:
Based on clinical presentation, physical examination findings, and imaging studies, the patient was diagnosed with lumbar instability accompanied by L4 degenerative spondylolisthesis (Grade I) and multilevel spinal canal stenosis at L3-4 and L4/5. The rationale for imaging included assessment of structural instability, degree of neural compression, and surgical planning.

Differential diagnosis considerations included isolated spinal stenosis without instability, degenerative disc disease without spondylolisthesis, and facet joint arthropathy. However, the combination of dynamic instability on flexion-extension radiographs, significant canal stenosis on MRI, and clinical symptom correlation confirmed the primary diagnosis.

The treatment plan consisted of oblique lateral lumbar interbody fusion (OLIF) at L3/4 and L4/5 levels via a left retroperitoneal approach. The rationale for this approach included the ability to achieve indirect decompression through disc height restoration, placement of large footprint interbody cages for stability, and avoidance of posterior muscle dissection. The patient was counseled regarding potential complications, including vascular injury, neurological deficits, and the possibility of revision surgery. Written informed consent was obtained after thorough discussion of risks, benefits, and alternatives, including posterior lumbar interbody fusion (PLIF) or transforaminal lumbar interbody fusion (TLIF).

Protocol

1. Preoperative preparation

1. The patient was admitted 1 day prior to surgery for preoperative assessment and preparation. Obtain laboratory studies, including complete blood count, coagulation profile, and basic metabolic panel. Confirm all values are within normal limits. Instruct the patient to fast for 8 h before the procedure. Prophylactic antibiotics (cefazolin 2 g intravenously) were administered 30 min prior to skin incision.

2. Intraoperative management

1. Patient positioning and setup
   1. Induce general anesthesia via endotracheal intubation. The patient was positioned in the right lateral decubitus position on a radiolucent operating table with the left side up to allow access to the retroperitoneal corridor. An axillary roll was placed under the dependent axilla to prevent brachial plexus injury.
   2. The hips and knees were flexed to relax the psoas muscle. The patient was secured to the table using tape and padding to prevent movement during the procedure. Care was taken to ensure the pelvis was perpendicular to the table and the spine was parallel to the floor to maintain proper anatomical alignment (Figure 4).
   3. Intraoperative C-arm fluoroscopy imaging was obtained in both anteroposterior (AP) and lateral projections to confirm appropriate positioning and to identify the target disc spaces at L3-4 and L4-5. The skin was marked at the anticipated incision sites based on fluoroscopic guidance.
2. Surgical approach and disc space preparation
   1. A longitudinal skin incision approximately 4-5 cm in length was made centered over the L4 vertebral body using a standard #10 surgical scalpel blade. Dissection was carried through the subcutaneous tissue and external oblique, internal oblique, and transversus abdominis muscles using a combination of blunt and sharp dissection. The retroperitoneal space was entered via careful blunt dissection, and the peritoneum was gently mobilized anteriorly and protected using surgical retractors to expose the lateral aspect of the lumbar spine.
   2. Under direct visualization following the clearance of overlying retroperitoneal fat, the psoas muscle was identified and retracted posteriorly using sequential dilators, followed by placement of a retractor system. Intraoperative fluoroscopy was used to confirm the proper positioning of the retractor at the L3-4 disc space. The segmental vessels were carefully exposed and identified via blunt dissection of the prevertebral soft tissue, and were protected throughout the procedure
   3. The annulus fibrosus was incised, and discectomy was performed using a combination of pituitary rongeurs, curettes, and shavers to remove the nucleus pulposus and cartilaginous endplates. Care was taken to preserve the anterior longitudinal ligament and contralateral annulus. To prepare the disc space for fusion, angled curettes and rasps were used to meticulously scrape the remaining cartilaginous endplates until bleeding subchondral bone was exposed, taking care not to violate the bony endplates.
3. Cage insertion at L3-4 and L4-5
   1. To ensure reproducible cage placement, smooth trial spacers of sequentially increasing heights were first impacted into the disc space under fluoroscopy until adequate annular tension and satisfactory disc height restoration were confirmed. Subsequently, an appropriately sized cage (45 mm in length and 12 mm in height) was tightly packed with autologous local bone and allograft material.
   2. The prepared cage was then introduced orthogonally into the L3-4 disc space and advanced across the midline using gentle mallet taps. Finally, the optimal position was verified via anteroposterior (AP) and lateral fluoroscopy, ensuring that the cage symmetrically spanned the bilateral cortical rims on the AP view to prevent subsidence, and was situated in the anterior-middle third of the disc space on the lateral view to maximize lumbar lordosis.
   3. The same procedure was repeated at the L4-5 level. Sequential dilators were repositioned, and the L4-5 disc space was accessed, prepared, and an interbody cage was inserted following the same technique. Final fluoroscopic images were obtained to document cage positioning at both levels.
4. Wound closure
   1. The retractor system was removed, and hemostasis was achieved. The retroperitoneal space was copiously irrigated with a vancomycin solution (1 g of vancomycin powder dissolved in 500 mL) to prevent surgical site infection. The wound was closed in layers using 2-0 absorbable sutures for the muscle and fascial layers, followed by subcuticular closure of the skin using 3-0 absorbable sutures. Sterile dressings were applied.

3. Postoperative assessment

1. Postoperative course and complications
   1. The patient was transferred to the recovery room in stable condition. However, immediately upon awakening from anesthesia in the Post-Anesthesia Care Unit (PACU), she began complaining of new-onset severe right lower extremity pain radiating down the anterior thigh, accompanied by weakness of the right psoas and quadriceps muscles (motor strength 3/5). This represented a contralateral neurological deficit, as the surgical approach had been from the left side.
2. Postoperative imaging and diagnosis
   1. Due to unexpected neurological symptoms, urgent postoperative CT imaging was obtained. The CT scan revealed malposition of the L4-5 interbody cage, with the posterior margin located inside the posterior margin of the vertebral body rather than flush with it (Figure 2A-B). More critically, the imaging demonstrated a fractured L4 osteophyte fragment that had migrated into the right neural foramen at the L4-5 level, causing compression of the right L4 nerve root (Figure 2F, asterisks). Postoperative MRI confirmed compression of the right L4 nerve root (Figure 2C-D).

4. Revision surgery

1. Given the radiological confirmation of mechanical nerve compression and progressive neurological deficit, the decision was made to proceed with urgent revision surgery. The patient returned to the operating room 3 days after the initial procedure.
2. A posterior midline approach was utilized for the revision. The patient was positioned prone on a Jackson table. A standard midline incision was made, and subperiosteal dissection exposed the right L4-5 facet joint and neural foramen. A right-sided transforaminal lumbar interbody fusion (TLIF) approach was performed with partial facetectomy and laminotomy to access the neural foramen.
3. The fractured osteophyte fragment was identified compressing the right L4 nerve root and was carefully removed using micro-instruments under microscopic visualization (Figure 3). Complete decompression of the nerve root was confirmed by direct visualization and gentle probing. Posterior pedicle screw instrumentation was placed at L3, L4, and L5 bilaterally to provide additional stability. Final fluoroscopic images confirmed appropriate hardware positioning and neural decompression (Figure 3A-B).

5. Postoperative recovery

1. Immediately following revision surgery, the patient reported significant improvement in right lower extremity pain. Motor strength in the right quadriceps gradually improved over the subsequent days. She was mobilized with physical therapy assistance on postoperative day 1 after revision. The patient was discharged on postoperative day 5 with instructions for gradual activity progression and outpatient physical therapy.

Results

Following the correct execution of the revision decompression procedure, the patient experienced complete resolution of contralateral neurological symptoms. Immediate postoperative assessment revealed a significant reduction in right anterior thigh pain. Motor strength in the right quadriceps improved from 3/5 preoperatively to 4/5 at hospital discharge and continued to improve to 5/5 (normal) by the 6-week follow-up visit.

Postoperative CT imaging obtained after revision surgery demonstrated ...

Discussion

OLIF is a recognized minimally invasive technique for addressing lumbar degenerative diseases, providing notable benefits including decreased blood loss, maintenance of posterior musculature, and expedited recovery^1,4. The benefits arise from the procedure's lateral approach, which preserves the anterior longitudinal ligament and minimizes soft tissue damage, thereby decreasing postoperative pain and length of hospital stay. Most neurological complications ty...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Absorbable sutures	Ethicon (Johnson & Johnson)	VCP316H	Wound closure (muscle and fascial layers)
Bone graft material	Medtronic	93-5000	Filled in interbody cage
C-arm fluoroscopy system	Siemens Healthineers	Cios Alpha	Intraoperative imaging
Cefazolin	Shandong Luokang Pharmaceutical	H20023691	Prophylactic antibiotic
Computed Tomography (CT) scanner	GE Healthcare	Revolution CT	Pre- and postoperative imaging
Interbody cage system	Shanghai San You Medical Device	CoRoent	OLIF interbody fusion
Magnetic Resonance Imaging (MRI) scanner	Siemens Healthineers	MAGNETOM Vida	Pre- and postoperative imaging
Pedicle screw system	Shanghai San You Medical Device	Adena-Zina System	Posterior fixation
Retractor system	Medtronic	963-001	Psoas retraction and exposure
Spinal surgical instruments (curettes, rongeurs, shavers, retractor)	Shanghai San You Medical Device	CoRoent	Discectomy and decompression
Surgical Scalpel Blade	Swann-Morton, Sheffield, UK	Size #10 (Carbon steel)	Skin incision and soft tissue dissection
Vancomycin Hydrochloride for Injection, USP (1 g/vial)	Hospira, Inc. (Pfizer)	NDC 0409-6531-02	Reconstituted in 500 mL of normal saline (2 mg/mL) for intraoperative retroperitoneal irrigation to prevent surgical site infection.
X-ray imaging system	Philips Healthcare	DigitalDiagnost C90	Pre- and postoperative plain radiographs