Degenerative Spondylolisthesis with Radicular Pain: Decompression-Only Versus Decompression and Fusion

Descriptions of deformity of the lumbosacral spine comprising slipped vertebrae or defects of the pars interarticularis were first reported in 1782 by Herbiniaux. Since that time, multiple classifications have been proposed to describe spondylolisthesis in terms of pathology related to the pars interarticularis and/or facet anatomy. Degenerative spondylolisthesis has been included in the most commonly used classification scheme used today. Other types include congenital, isthmic, traumatic, pathologic, and postsurgical.

Degenerative spondylolisthesis is most commonly seen in middle-aged women at L4-5, less commonly at L3-4, and rarely at L5-S1. Synovial surfaces of the superior and inferior facets at these levels are biomechanically important because they resist rotation along the coronal plane and anterior slippage along the sagittal plane. The degenerative cascade results in damage to the facet joint and hypermobility, which contributes to spondylolisthesis. Concomitant hypertrophy of the ligamentum flavum and facet joint below an intact posterior neural arch that has slipped forward produces spinal stenosis and resulting clinical neurogenic claudication as the neural elements are compromised. The cause of symptoms is lateral recess stenosis from slippage of the inferior facet forward and central stenosis from disk herniation.

In the process of neural element decompression, the spondylolisthesis can be exacerbated. The management of this disease process in grade I spondylolisthesis is discussed in this chapter, with an emphasis on best evidence.

Case Presentation

A 72-year-old white woman had a 4-year history of progressive low back pain and neurogenic claudication symptoms.

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PMH: Unremarkable
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PSH: Unremarkable
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Exam: Well-developed, well-nourished elderly woman, ambulatory with cane assistance, antalgic gait, normal muscle bulk and tone, motor strength 5/5 in all extremities, normal results on sensory examination, deep tendon reflexes symmetric bilaterally.
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Imaging: Preoperative radiographs showed grade I spondylolisthesis at L3-4 ( Figure 8-1 , A and B ). Magnetic resonance imaging (MRI) of the lumbar spine revealed degenerative Modic end-plate changes at L5-S1; lumbar stenosis at L3-5 secondary to facet arthropathy greater at L3-4 than at L4-5; and a hypertrophic ligamentum flavum. The spondylolisthesis at L3-4 and disk herniation at this level contributed to central and lateral recess stenosis ( Figure 8-1, C through E ) ( Tips from the Masters 8-1 ).

FIGURE 8-1

Preoperative images showing grade I spondylolisthesis at L3-4. A, Anteroposterior radiograph of lumbar spine. B, Sagittal radiograph of lumbar spine. C, T2-weighted sagittal MRI images of the lumbar spine. D, T1-weighted sagittal MRI images of the lumbar spine. E, T2-weighted axial MRI images of the lumbar spine. MRI images show degenerative Modic end-plate changes at L5-S1; lumbar stenosis at L3-5 secondary to facet arthropathy that is greater at L3-4 than at L4-5; and a hypertrophic ligamentum flavum. The spondylolisthesis at L3-4 and disk herniation at this level contribute to central and lateral recess stenosis. Note the hyperintense signal within the facet joints bilaterally, which can indicate instability.

Tips from the Masters 8-1

Look for a high-intensity area within the facet joint complex preoperatively on axial T1-weighted MRI images.

Treatment Options

Observation

Referral to a nutritionist for dietary management to achieve weight loss can be recommended for overweight or obese patients. Physical therapy with instruction in core stabilization exercises, appropriate lifting mechanics, and functional aerobics including water therapy can be instituted. The use of nonsteroidal antiinflammatory medications can be considered if there are no medical contraindications. Referral to a pain management clinic for consideration of epidural steroid injections may also be offered.

Laminectomy Decompression at L3 through L5

Laminectomy decompression at L3 through L5 can relieve neural compression and improve the claudication symptoms. The technique consists of medial facetectomies, which decompress the lateral recess. The MRI scan for the patient described in the Case Presentation revealed high-intensity signals within the facet joint, which raises the concern of instability. Caution should be used in recommending decompression only under these circumstances in patients with significant back pain.

Decompression and Fusion without Instrumentation

Decompression and fusion without instrumentation involves a posterolateral fusion of the transverse processes with local autograft, allograft bone, and demineralized bone matrix. The use of synthetic extenders with bone marrow aspirate has also been shown to lead to good fusion.

Decompression and Fusion with Instrumentation

If decompression and fusion with instrumentation is elected, inclusion of L2 or S1 should be considered. The quality of bone should also be taken into account with long constructs such as these which require that either a laterally directed sacral alar screw or an iliac screw be used to increase the stability of the construct. The use of titanium polyaxial screws and rods are recommended for improved MRI compatibility, more appropriate material elastic modulus, and ease of instrument insertion.

The patient underwent decompression and instrumented fusion from L2 through L5 because of the multiple levels of unstable spondylolisthesis and stenosis ( Figure 8-2 ). Because the L5-S1 segment was transitional and already fused, there was no need to instrument to S1.

Fundamental Technique

After induction of general anesthesia, a gravity-draining Foley catheter is placed and a preoperative antibiotic (usually cefazolin) is given. The patient is turned prone onto an Andrews table, and all pressure points of the face, torso, and extremities are carefully padded. The patient is converted to a kneeling position, and care is taken to make sure the belly hangs free to limit pressure on the inferior vena cava, which aids in minimizing blood loss. Standard landmarks of the iliac crest and palpation up from the sacrum are used to delineate L2 through S1 with a marking pen. Taking radiographs at this time with a needle in place between spinous processes can help in centralizing the incision. The skin is cleansed and draped in sterile fashion. After the skin incision is made, Bovie electrocautery is used to dissect the paraspinal muscles subperiosteally so that the facet capsules and transverse processes are exposed bilaterally at each level. Care is taken not to violate facet capsules that do not need to be fused. Using standard landmarks, pilot holes are drilled, and the pedicles of L2 through S1 are probed and circumferential bone is confirmed with a ball-tip probe. These holes are covered with thrombin-soaked absorbable gelatin sponges. From the preoperative images, it is clear that the neurogenic claudication symptoms in the patient described in the Case Presentation were related primarily to the significant stenosis at L3-4 and less so to that at L4-5. In such cases, bilateral laminectomies from L3 through L5 are performed with decompression centrally and along the lateral recesses at L3-4. Ideally, leaving at least 5 mm and, if possible, 7 mm of the pars interarticularis is recommended to avoid postoperative pars fracture when the patient is upright. When undercutting to achieve a medial facetectomy, an attempt should be made to ensure that 50% of a functional facet joint complex remains, inclusive of a functioning superior facet and inferior facet. A Woodson dental instrument is used to palpate after decompression to ensure that adequate bilateral foraminotomies have been performed. A high-speed drill bur is used to decorticate the transverse processes bilaterally and the facet complexes. Locally harvested bone autograft from the spinous processes, lamina, and facets is morselized and placed in the lateral gutters to achieve posterolateral arthrodesis. Part of the pain experienced by the patient described in the Case Presentation was related to hypermobility at L3 through L5, and posterior instrumentation with a pedicle screw and rod construct provides immediate fixation and symptomatic improvement ( Tips from the Masters 8-2 ). A cross-link can be added to increase the overall rigidity and resist rotational forces.

Tips from the Masters 8-2

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