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Trans-sacral Fusion of Spondylolisthesis at L5-S1

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Patient History

The patient is a 49-year-old-male mechanic, who presents with a 1-year history of axial low back pain and primarily right leg sciatica. He describes his pain as 50% back pain and 50% leg pain.

His back pain is exacerbated by mechanical-type activities including sitting, standing, bending forward, lifting, and twisting, whereas standing and walking worsens his leg pain. He reports weakness of his right foot and great toe dorsiflexion, as well as some difficulty walking stairs on his right leg.

His pre-operative assessment scores are VAS back 8/10, VAS leg 9/10, and an Oswestry Disability Index (ODI) of 46. He has been disabled from his work for approximately 3-months.

Nonsteroidal anti-inflammatory drugs, oral opioid narcotics, and muscle relaxants only partially control his pain.

Vikas Mehta, MD*
Zhaomin Zheng, MD*
Budong Chen, MD*
*UCLA Comprehensive Spine Center, Los Angeles, CA

Farbod Asgardzadie, MD
Assistant Professor, Neurosurgery
Loma Linda University School of Medicine
Loma Linda, CA


The patient is a healthy 5'11" male who weighs 205 pounds. Vital signs are normal. His musculoskeletal examination was significant for left trunk tilt, antalgic gait, right leg limp, visible listhetic crease in his trunk near L5-S1, as well as pain on deep pressure in that region. There is no visible atrophy of arm or leg musculature.

His neurological examination revealed weakness of the right extensor hallucis 4/5 and right gastrocnemius 5-/5 with subjective pin numbness and decreased 2-point discrimination in the right L5 distribution. He has a positive straight leg raise and crossed-leg raise sign.

Prior Treatment

He completed a comprehensive 4-month physical therapy program involving Pilates, core strengthening, and weight loss of 15 pounds that provided moderate pain control.

He has had numerous transforaminal, translaminar, and facet cortisone injections at L5-S1 with only transient relief.

After an extensive discussion regarding management options, both nonsurgical and surgical, the patient decided to pursue surgery.


AP and lateral x-rays revealed a mobile spondylolisthesis at L5-S1, which reduced from 30% to 15% between flexion and extension. There was a significant loss of intervertebral disc height and loss of lordosis with a vacuum sign (Figure 1).

Lateral x-ray, L5-S1 spondylolisthesis
Figure 1

Pre-operative MRI imaging of the lumbar spine again demonstrated a grade 1.5 spondylolisthesis at L5-S1 with a moderate-sized broad disc bulge, bilateral facet hypertrophy with increased T2 signal in the joints, as well as synovial cysts, and bilateral pars fractures (Figure 2).

MRIs, L5-S1 spondylolisthesis
Figure 2


Spondylolisthesis at L5-S1.

Suggest Treatment

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Selected Treatment

After induction of general endotracheal anesthesia, the patient was positioned prone on a radiolucent Jackson 4-point frame. Two GE-9800 fluoroscopic image intensifiers were positioned to provide biplanar lumbar imaging.

Left paramedian paracoccygeal and bilateral Wiltse-type paramedian L5-S1 incisions were marked and pre-anesthetized with .25% Marcaine® and 1:200,000 epinephrine under fluoroscopic guidance.

The paramedian Wiltse incisions were then incised with finger dissection carried down to the level of the transverse process-facet junctions at L5-S1 bilaterally. Under biplanar fluoroscopic control, #11 Jamshidi® needles were used to cannulate the L5 and S1 pedicles. These were exchanged for K-wires over which cannulated 6.5mm pedicle screws from PathFinder® (Abbott Spine) minimally invasive pedicle screw fixation were placed.

Using the extender sleeves, the reduction tools were used to reduce the anterolisthesis at L5-S1 and restore alignment of the 2 vertebral bodies. In addition, moderate distraction was applied across the L5 and S1 screws to partially unlock the facets and increase intervertebral height. The screws were temporarily locked to the rod to maintain this reduction.

The 1.5cm paramedian coccygeal incision was incised and finger dissection completed to palpate the anterior periosteal surface of the coccyx and sacrum. The blunt initial dilator from the AxiaLIF™ (TranS1®, Inc., Wilmington, NC) trans-sacral system was used to dissect the pre-sacral space superiorly under biplanar fluoroscopic control to the level of the S1-S2 junction. The blunt central core was exchanged for a Steinman pin, which was docked and passed through the sacrum cranially to the level of the L5-S1 disc space.

The bony dilators were serially exchanged and inserted into the sacrum to secure a working channel into the L5-S1 disc space with biplanar fluoroscopic confirmation of trajectory and position. Nitinol radial cutters were used to complete a full axial discectomy and debridement of the L5 and S1 endplates. A large kit of bone morphogenic protein (INFUSE®, Medtronic, Memphis, TN) mixed with 15cc of synthetic calcium-triphosphate / collagen composite (Vitoss®, Orthovita, Inc., Malvern, PA), and 3cc of local bone obtained from sacral reaming was packed through a funnel into the L5-S1 disc space.

The K-wire was advanced into L5 and the final pathway reamed over this trajectory. A 45mm AxiaLIF cage, with moderate distractive ability, was passed over the K-wire through the L5-S1 disc space. As the AxiaLIF cage was threaded across the L5-S1 space, the L5 PathFinder screws were unlocked to allow for distraction across the space by the trans-sacral cage. The AxiaLIF cage was locked into place at L5 and S1 achieving approximately an 8 to 9mm restoration of disc height.

The PathFinder screws were also counter-torqued and locked with the extension sleeves removed. The final construct was confirmed under fluoroscopic control (Figures 3A, 3B).

Solid arthrodesis with TranS1 AxiaLIF implant
Figure 3A

Solid arthrodesis with TranS1 AxiaLIF implant
Figure 3B

A small tubular, minimally invasive portal (METRx™, Medtronic, Memphis, TN) was inserted and docked at the right L5-S1 laminofacet junction under fluoroscopic guidance. Using an operating microscope, a right L5-S1 laminotomy, medial facetectomy, foraminotomy, and discectomy were completed with excellent decompression of the exiting right L5 and traversing S1 roots.

All wounds were then copiously irrigated and closed with interrupted Vicryl sutures subcutaneously. Dermabond® (Ethicon, Inc.) was used to seal small skin incisions.

Total operative time was 2-hours with a blood loss of less than 20cc.


Financial Disclosure
Larry T. Khoo, MD serves as a consultant and clinical educator to TranS1®, Inc.



Postoperatively, the patient remained at his neurological baseline with resolution of his prior sciatic symptoms. He was discharged 36-hours after surgery on oral narcotics and muscle relaxants.

His recovery was uneventful and he completed a 3-month course of additional core strengthening and rehabilitation. He returned to work at 5-months postop. At 1-year, CT control imaging, along with flexion-extension imaging revealed solid arthrodesis at the L5-S1 level (Figures 4A, 4B). His 1-year assessment scores were VAS back 1/10, VAS leg 0/10, and ODI 19.

Solid arthrodesis with TranS1 AxiaLIF implant
Figure 4A

Solid arthrodesis with TranS1 AxiaLIF implant
Figure 4B

Case Discussion

Dynamic radiculopathy is a frequent complaint of middle-aged patients with histories of prior spondylolysis and spondylolisthesis. The case presented by Dr. Khoo illustrates such an occurrence.

Fracture of the pars interarticularis results in loss of functional stability in the tripod structural components of the lumbar spine; anterior disc space and posterior facet joints. Lumbar discs resist 80% of compressive loads. While the lumbar facet joints only experience 20% of compressive load, their integrity is important in reducing shear stress experienced by the anterior disc. Repetitive spinal stresses, under these circumstances, results in accelerated disc degeneration - loss of disc height, anterior translation of cephalic on caudal vertebra (lithesis), and consequential foraminal stenosis and nerve root irritation. Typical histories delivered by patients in these circumstances suggest a long-term experience of lower back pain with recent onset of leg pain. With the increased incidence of spondylolysis at the L5 level, grade I to grade II spondylolisthesis and L5 or combined L5-S1 radiculopathy are also quite common. Dr. Khoo's patient has a complaint of increasing pain with activity and on examination there is evidence of motor weakness and functional limitation. The Visual Analog Scale and Oswestry Disability Index also suggest a heightened level of dysfunction associated with these presenting complaints.

Nonoperative care is recommended as the initial treatment for all patients with symptoms of low back and / or leg pain. Failure to respond to nonoperative modalities - core strengthening, flexibility, oral pharmaceuticals, with improved functional capacity - should lead to consideration of more aggressive treatment options. Choice of additional treatment options is frequently tempered by the treating physician's experience and skill set. Patients with significant complaints of leg pain in a radicular distribution are often offered injection therapies in the form of epidural steroids or, perhaps, selective nerve root blocks. Lack of symptom improvement following extensive physical therapy and multiple injections gives cause for contemplation of operative intervention. Imaging studies - plain radiographs and MRI - illustrate isolated degeneration of the L5-S1 motion segment; grade I spondylolisthesis with L5 nerve root compression. When considering surgical intervention, patient benefit is more favorably predicted in situations where history, physical examination, and imaging studies correlate. Unfortunately, there is limited level-I data to suggest one surgical procedure over another as the treatment of choice. On the basis of critical thinking, lack of level-I data should default to community standard and surgeon experience in a well-informed patient.

In recent years, less invasive surgical procedures have gained greater prominence on the surgeon's list of potential treatment options. In cases of dynamic radiculopathy, the goal of any procedure is decompression of neural elements and stabilization of the motion segment. Decompression alone, in the face of hypermobility, has been shown to increase segmental motion and potentially exacerbate instability. The surgeon's choice of procedures in this case does address the reviewer's ultimate goal of treating dynamic radiculopathy. The pericoccygeal approach to L5-S1 makes anatomic sense, but has not been readily accepted by a large proportion of spine surgeons. Utilization of this approach, in conjunction with less invasive posterior instrumentation and decompression, has merit when selecting a minimally invasive treatment option for this patient. However, considering the options presented in this case report the reviewer would have chosen "other." This reviewer has experience with similar cases and thus far has opted for anterior interbody fusion with indirect decompression, interbody device and anterior instrumentation followed by percutaneous posterior pedicle screw instrumentation under the same anesthesia. Dr. Khoo has presented a very provocative argument for consideration of the pericoccygeal approach to anterior column support for those surgeons adopting less invasive surgical options.


Aryan HE, Newman CB, Gold JJ, Acosta FL Jr, Coover C, Ames CP. Percutaneous axial lumbar interbody fusion (AxiaLIF) of the L5-S1 segment: initial clinical and radiographic experience. Minim Invasive Neurosurg. 2008 Aug;51(4):225-30.


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