Adjacent Level Degeneration: Lumbar Disc Degeneration Adjacent to Previous Fusion
This surgeon is a consultant of Medtronic, but received no compensation for this case discussion.
The patient is a 62-year-old female who is retired. In 2000, she underwent successful L4-L5 anterior posterior fusion. She now presents with progressively worsening pain described as 50% back and 50% bilateral legs (posterior thighs, calves, and feet). Pain is worse when standing and relieved when seated. Her walking tolerance is a quarter-of-a-mile.
She has a history of mild hypertension with no other significant issues. Her Oswestry Disability Index (ODI) is 38 and Visual Analog Score (VAS) is 6/10.
Prior treatment includes extensive physical therapy. She also performs a trunk stabilization program at home.
She reports pain with 70-degrees flexion and 10-degrees extension in her lumbar spine. Neurologically, she is intact with no nerve tension signs. Otherwise, her exam is normal.
Figure 1A, an anteroposterior x-ray, demonstrates loss of disc height with osteophyte formation and no coronal deformity. The lateral x-ray (Fig. 1B) shows loss of disc height, osteophytes, no spondylolisthesis, and L3-L4 lordosis of 12-degrees. The flexion x-ray (Fig 1C) reveals a 6 mm spondylolisthesis and L3-L4 kyphosis of 3-degrees.
Figure 1A. AP x-ray
Figure 2A demonstrates solid fusion at L4-L5 and vacuum disc at L3-L4. The axial CT scan (Fig. 2B) shows hypertrophic facet joints and severe spinal stenosis at L3-L4.
Figure 2A. Sagittal CT scan
Figure 2B. Axial CT scan
Severe central spinal stenosis and degenerative disc disease presents at L3-L4 (Fig. 3A), moderate foraminal stenosis at L3-L4 (Fig. 3B), and severe lateral recess stenosis at L3-L4 (Fig. 3B).
Figure 3A. Sagittal MRI
Figure 3B. Sagittal MRI
Figure 3C. Axial MRI
Neurogenic claudication and mechanical back pain due to degenerative disease at L3-L4 with severe stenosis.
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The patient underwent a right-sided approach, L3-L4 DLIF, posterior laminotomy with pedicle screw fixation, and facet fusion with local autograft. An interbody device was used and previous posterior instrumentation at L4-L5 was removed.
Fusion was performed due to:
- L3-L4 disc was hypermobile on flexion view
- CT scan evidence of a vacuum disc
- Hypertrophic facet joints with severe degeneration and stenosis
- Significant back pain
Pedicle screw fixation provides excellent stability and increases fusion rates. Interbody fusion increases stability in non-collapsed disc spaces, restores lordosis, and increases fusion potential.
ALIF allows ideal disc preparation and enables large graft insertion to restore lordosis. In the hands of an experienced approach surgeon, the risks of an anterior retroperitoneal approach can be minimized. These risks include vascular injury, intestinal injury, ileus, incision-related hernia, and retrograde ejaculation. Previously, the patient underwent an anterior left-sided retroperitoneal approach to L4-L5. Therefore, there was potential for scarring of the retroperitoneal space and vessels anterior to the spine.
Benefits of the direct lateral approach include:
- Excellent disc space preparation and insertion of large interbody grafts without requiring mobilization of the vessels from the anterior aspect of the spine.
- Excellent foraminal distraction for insertion of large grafts that rest laterally on the apophyseal ring.
- Interbody grafts are less likely to contact nerve roots, which should be buried within the muscle and protected by the retractor in this approach.
- DLIF can be performed from either the right or left side.
- DLIF requires less mobilization of the peritoneum than ALIF (reduces risk for intestinal injury or ileus).
- Anterior and posterior longitudinal ligaments are preserved (stability).
Surgical technique can minimize risks associated with the direct lateral approach:
- Lumbar plexus injury (requires nerve monitoring)
- Psoas injury (retraction of psoas muscle fibers rather than removal)
- Genitofemoral nerve or vascular injury (direct visualization during approach)
TLIF may afford a posterior-only approach, however disc space preparation, including the amount of disc removed and the ability to remove endplate cartilage without violating the bony endplate, is less than ideal with TLIF (as compared to ALIF and DLIF).
In addition, the size of TLIF grafts is smaller than other options and decreases restoration of lordosis and potential for fusion. There is a risk of nerve injury from retraction during graft insertion and post-operative inflammation.
In our practice, ALIF is the gold standard for disc space preparation and large graft insertion. DLIF has become an excellent option for L4-L5 and cephalad. DLIF disc space preparation and capacity for insertion of large grafts is good for correction of coronal and sagittal deformities and has been very successful.
We've found that TLIF at L5-S1 is a good option for patients who are elderly, obese, when a single incision benefits, and in some elderly patient cases of L4-L5 degenerative spondylolisthesis where ALIF may be complicated by aortic calcification.
Figure 4: After DLIF and prior to posterior incision. The marker x-ray demonstrates excellent restoration of disc height and lordosis from the graft and interbody device.
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Figure 5A is one-year post-op and details bridging bone in the interbody space; the hardware is intact. The lateral view (Fig. 5B) also demonstrates bridging bone in the interbody space with L3-L4 lordosis of 16-degrees.
Figure 5A. AP x-ray
Figure 5B. Lateral x-ray
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The patient left the hospital at post-op day 4. At her two month follow-up, she reported 4/10 described as mild intermittent pain. Four months post-op, the patient reported no pain. Sixteen months after surgery she reported her pain a 2/10 and mild intermittent back pain. Her Oswestry Disability Index was 4.
Doctor Watkins' case is an excellent illustration of the DLIF or extreme lateral approach. The case is of a 62-year-old woman with a previous L4-L5 fusion who now has adjacent level degenerative changes at L3-L4. The patient had surgery 10 years previously. Excellent results are noted at 16 months in regards to lower back pain and leg pain. Radiographic results indicate a solid lumbar fusion.
The discussion notes several surgical options; including, a (1) posterolateral arthrodesis with pedicle screws L3-L4, (2) PLIF at L3-L4, (3) ALIF with posterior pedicle screws, and (4) DLIF at L3-4 with posterior pedicle screws. A laminectomy and fusion extension with a posterolateral arthrodesis is probably the simplest approach. Surgery requires only one incision. There is no need to reposition the patient. The stenosis is addressed directly. On the down side, there may be scarring from the previous surgery and the rate of fusion may be lower with a posterolateral arthrodesis alone. The addition of a posterior interbody fusion may improve the fusion rates but carries some increased morbidity especially in terms of a lumbar radiculitis.
A previous posterior surgery fusion extension is an excellent use of the DLIF approach because there is no scar tissue to deal with in accessing the disc space. Disadvantages of the DLIF approach include the need to reposition the patient, use of a separate incision, and increased morbidity related to the procedure, such as proximal post-operative iliopsoas weakness and anterior thigh pain. A posterior approach, dissection, and pedicle screw placement is still necessary. Additionally, the procedure depends on indirect decompression for stenosis and presumed radiculopathy.
The authors demonstrate the DLIF procedure and posterior pedicle screws work in this patient. There are multiple surgical options. Demonstrating one approach as superior is difficult and the choice of the approach may ultimately lie with the surgeon's skills.