Spondylolisthesis, Spondylolysis, and Spondylosis Treatment & Management

The goal of surgery is to stabilize the segment with listhesis and decompress any of the neural elements under pressure. Restoration of normal sagittal alignment must also be achieved. In evaluating a patient, many factors must be considered, including age, degree of slip, and risk of slip progression. Thus, each patient's treatment algorithm should be individualized to achieve optimal outcome.

The indications for spinal fusion clearly differ in the pediatric and adult populations. For the younger population, the following factors are known to correlate with a higher risk of slip progression:

• Younger age (< 15 years)
• High-grade listhesis (>30%)
• Female sex
• Ligamentous laxity
• Type 1 (dysplastic) slip
• Lumbosacral hypermobility

However, many young patients are treated by means of immobilization or activity modification alone, with a significant success rate. In the absence of high-grade slips, minimal symptomatology, and lack of slip progression, fusion is generally not indicated in this population.

Before surgery is considered for adult patients presenting with degenerative spondylolisthesis, minimal neurologic signs, or mechanical back pain alone, conservative measures should be exhausted, and a thorough evaluation of social and psychological factors should be undertaken. ^[15]

Indications for surgical intervention (fusion) are as follows:

• Neurologic signs - Radiculopathy (unresponsive to conservative measures), myelopathy, neurogenic claudication
• Any high-grade slip (>50%)
• Type 1 and type 2 slips, with evidence of instability, progression of listhesis, or lack of response to conservative measures
• Traumatic spondylolisthesis
• Iatrogenic spondylolisthesis
• Type 3 (degenerative) listhesis with gross instability and incapacitating pain
• Postural deformity and gait abnormality

Surgery is contraindicated if the patient is in poor medical health and if the operative risk is not outweighed by the potential benefits.

Anticoagulation with warfarin, or antiplatelet therapy, can make the risk of hemorrhage much higher than routinely expected. Antiplatelet therapy should be discontinued 3-5 days before the procedure. Warfarin should be stopped 5-7 days before the procedure, and a prothrombin time (PT) within the reference range should be achieved before surgery.

Smoking significantly decreases the chance for a successful fusion. Some surgeons prefer that a patient commit to smoking cessation up to one month before the surgical procedure.

Correction of the listhesis is associated with risk of neurologic injury, both transient and permanent. Some surgeons prefer to fuse the spine in place rather than to reduce the subluxation. In persons with higher-grade spondylolisthesis, use of interbody grafts is associated with a high rate of complications. However, the use of these devices adds to the stability of the spinal segment, helps with the reduction of the deformity, and helps achieve sagittal balance, thus ensuring better outcome.

As the understanding of spinal instability and biology of bone healing increases, we will be able to better define the population of patients with spondylolisthesis who would benefit most from lumbar fusion or particular methods of fusion and fixation.

Production of bone morphogenic protein (BMP) is a promising venture that undoubtedly will affect the outcome of lumbar fusion. Advances in technology have led to better instrumentation, and further advances are anticipated. Artificial disks and lordotic tapered cage devices are under investigation; they clearly will affect the technical aspects of the operation. The use of bone-growth stimulators is a potentially useful tool for higher fusion rates, though there is a need for long-term data. Osteoinductive pastes and other semisolid mixtures have been introduced to the market; they also promise to enhance the success of this operation.

Although technology continues to improve the performance of surgical treatment, the most challenging task is simply optimal patient selection. As stated previously, clear indications for fusion must be present in order to optimize outcome, and controversies still exist, especially in the treatment of degenerative spondylolisthesis, that must be resolved in a methodic and scientific manner. Prospective randomized studies with independent evaluators probably will produce the greatest improvement to the outcome of lumbar fusions.

Conservative measures are aimed at symptomatic relief and include the following:

• Activity modification, bedrest during acute severe exacerbations
• Analgesics (ie, nonsteroidal anti-inflammatory drugs [NSAIDs])
• Bracing
• Therapeutic strengthening and stretching exercises

The likelihood of success with nonoperative treatment is high, especially in younger patients. In older patients who have low-grade slips resulting from disk degeneration, traction has been used with some success. The authors recommend that any manipulation or traction be performed under the care of a clinician and a physical therapist.

One of the challenging tasks is to treat patients with severe back pain and marginally abnormal radiographs. Such patients may have degenerative disk disease (eg, multilevel disk desiccation observed on magnetic resonance imaging [MRI]) or even low-grade (typically < 25%) slips, and they typically experience pain that is out of proportion to the physical or radiographic findings.

Back pain in general is a major public health problem and remains a primary cause of disability in the United States. Its causes are numerous, and no simple diagnostic method exists for excluding structural causes. It is important for any clinician who cares for patients with spinal problems to address behavioral and psychosocial factors that may contribute to a patient's disability.

The goal of surgical treatment in this setting is to decompress the neural elements and immobilize the unstable segment or segments of the spinal column. This is usually performed with elimination of motion across the facet joint and the intervertebral disk through arthrodesis (fusion). ^{[4, 8]}  (See the images below.)

The SPORT (Spine Patient Outcomes Research Trial) study analyzed the cost-effectiveness of surgery versus nonoperative care in patients with spinal stenosis, degenerative spondylolisthesis, and intervertebral disk herniation. ^[16]  In this trial, surgical therapy overall improved health and provided better value over 4 years as compared with nonoperative care.

Aspects of surgical treatment

Fusion

Multiple methods exist for achieving intersegmental fusion in the lumbosacral spine. ^[17]  The authors concentrate on the three most widely used methods, as follows:

• Posterolateral (intertransverse) fusion
• Lumbar interbody fusion
• Pars repair

Most surgeons use the intertransverse or transverse process/sacral ala arthrodesis with the use of iliac crest autograft alone or in conjunction with allograft. This may be performed over one or multiple levels with high success rates (up to 90%) of fusion. Some surgeons prefer a two-level fusion (ie, L4>S1) for treating high-grade (>50%) listheses. Segmental spinal instrumentation allows rigid fixation of the fused segments and the possibility of performing reduction of the segment with listhesis. There is some evidence to suggest that recombinant human BMP (rhBMP) is a safe and effective grafting material for the treatment of lumbar spondylolisthesis. ^[18]

Biomechanically, lumbar interbody fusion increases the stability of the spinal segment by placing structural bone graft in compression in the anterior and middle columns and increases the overall surface area of the bony fusion. ^[19] It can be done with posterior (ie, posterior lumbar interbody fusion [PLIF]) or anterior (ie, anterior lumbar interbody fusion [ALIF]) approaches. A growing number of surgeons use interbody grafts to augment their posterolateral fusion techniques to achieve higher rates (>95%) of arthrodesis. It should be noted that grade 2 or higher slips are predisposed to higher rates of graft complications.

In low-grade lytic slips, the pars can be directly repaired with a Scott wiring technique or the Van Dam modification. This preserves segmental motion and has successfully been used to fuse the pseudarthrosis at the pars in selected patients.

Dean et al studied 58 patients who underwent anterior cervical decompression and fusion, with an iliac crest structural graft, for degenerative spondylolisthesis from 1974 to 2003; they were evaluated for neurologic improvement and osseous fusion. The investigators found that the average neurologic improvement was 1.5 Nurick grades and that the overall fusion rate was 92%. ^{[20, 21]}

Fixation

Although the use of spinal instrumentation in skeletally immature patients is considered optional by some surgeons for some patients with isthmic-type spondylolisthesis, most spinal surgeons believe that rigid fixation is needed to achieve a solid fusion reliably. For degenerative-type slips, fixation has been shown to achieve higher rates of solid arthrodesis.

Decompression

Usually in degenerative or traumatic spondylolisthesis, decompression of the neural elements, both centrally and laterally, over the nerve roots is indicated. Optimal decompression is usually achieved through a posterior laminectomy and total facetectomy with radical decompression of the nerve root (ie, Gill procedure).

In a study by Schaeren et al, decompression and dynamic stabilization showed excellent results, after a follow-up of at least 4 years, in elderly patients with spinal stenosis and degenerative spondylolisthesis. Patient satisfaction was high, with 95% stating they would undergo the procedure again. ^[3]

Reduction

Some surgeons attempt to reduce the spondylolisthesis in order improve the overall sagittal alignment and spinal biomechanics. This has the benefit of improving standing posture and placing less strain on the posterior fusion mass and spinal hardware, thus reducing the incidence of nonunion and spondylolisthesis progression. The quoted rate of transient or permanent nerve-root injury associated with reduction is 5-30%.

Preparation for surgery

The surgeon should plan the approach (anterior vs posterior); determine the methods of fusion (ie, iliac crest autograft) and fixation (ie, transpedicular screws); and discuss the risks, benefits, and alternatives of each decision with the patient. Patients can require blood transfusions after spinal fusion and should be given the option of predonating their blood for an autologous transfusion. Some surgeons use blood salvage systems that collect the patient's blood lost during surgery for return to the patient in order to try to minimize the need for transfusion.

Recent plain radiographs with flexion and extension views help define the grade of spondylolisthesis and help with the operative approach. Although most spine surgeons are familiar with pedicle screw placement in the lumbosacral region, computed tomography (CT) helps determine the diameter and trajectory of each pedicle and can be a useful adjunct to preoperative imaging. This is especially useful in correction of listhesis in thoracic and upper lumbar vertebrae (ie, in traumatic spondylolisthesis).

The use of perioperative antibiotics is mandatory. Studies have demonstrated a lower rate of infection with a single dose of cefazolin given within 30 minutes of the incision. For patients with true allergy to beta-lactams, alternative coverage with macrolides or aminoglycosides can be achieved.

Smoking is associated with a high (up to 50%) nonunion rate, and the cessation of smoking is an essential part of the patient's commitment to the success of the operation.

Antiplatelet therapy should be discontinued 3-5 days prior to the procedure. Perioperative and postoperative use of anti-inflammatory medication is not recommended, because they can inhibit fusion.

Operative details

Depending on the symptoms (pure nerve-root compression vs mechanical pain due to segmental instability), different operative techniques are available. Simple minimally invasive microdecompression via a very small incision is often successful in low-grade slips with only single-root involvement. This operation can be performed through a miniopen microscopic or endoscopic approach; this releases the pressure on the traversing and exiting roots through subarticular decompression in the lateral recess. The more classical approach for a definitive posterior fusion and instrumentation is described below.

Via a posterior midline approach, the lumbodorsal fascia is divided, and a subperiosteal dissection of erector spinae muscles is performed over the posterior elements of the involved vertebrae (typically L5 and S1).

Some surgeons prefer the harvesting of iliac crest autograft prior to the fascial opening. This can be performed through the same incision on one or both iliac crests in lumbosacral fusion operations. The fascia overlying the crest is opened. Care is taken to preserve the integrity of the sacroiliac joints. The thickest area for obtaining cancellous bone is decorticated, and multiple gouges are used to retrieve the autograft. Hemostasis is obtained, and the fascia is closed over a drain.

In type IIa (lytic) slips, the spondylolysis can often be observed on palpation with the hypermobility of the L5 posterior elements and the incompetent pars. The lateral exposure is extended past the lateral facets and to the transverse processes. Self-retaining retractor systems hold the entire exposure accessible to the surgeon. The intertransverse plane is cleaned, and a fusion bed for the bone graft is prepared. In fusions involving the sacrum (most lytic types), the sacral ala should be exposed, and the alo-transverse plane is used for the posterolateral fusion.

More minimally invasive solutions would involve approaching each facet via a muscle-splitting approach (sparing the midline structures) and directly decompressing the lateral recess directly. This can be combined with minimally invasive fusion and instrumentation of the affected segment. Percutaneous or miniopen instrumentation has also been used with great success.

Decompressive laminectomies and facetectomies are typically initiated with rongeurs (eg, the Leksell rongeur) and completed with high-speed drills. The Gill laminectomy involves complete removal of the posterior elements of L5 and both articular facets. Because of the incompetent pars in type IIa slips, this can be performed with relative ease using large rongeurs.

Frequently, the entire loose posterior arch need not be removed, but the ever-present remnant that is attached to the pedicle must be removed to ensure adequate decompression of the L5 root. Preserving the posterior arch and grafting across the pars defect resulted in better fusion rates in the Nachemson series. All bone is typically saved and mixed with the cancellous autograft.

After the nerve roots are identified, decompressive foraminotomies are performed, following the course of the nerve roots through their respective foramina. Depending on the grade of the slip, the exiting nerve root (L5 root in most slips) takes a sharp angle during its course and may be kinked as it exits in the L5-S1 foramen. Distraction and partial reduction of the slip can lessen the amount of stretch that the slip places on the nerve root. However, reports quote an up to 30% rate of nerve-root injury resulting from attempted reduction.

Some advocate radical excision of the intervertebral disk to help with the reduction as well as placement of an interbody graft. The risk of transient nerve-root injury is slightly higher with this maneuver (reduction); however, the immediate support afforded by the anterior column support increases the rate of fusion, helps with distraction and reduction, and relieves the acute course of the exiting root. In low-grade slips, especially those of the degenerative type, the restoration of foraminal height provided by the interbody graft helps with the exiting nerve-root symptoms.

After adequate decompression of the involved nerve roots, the lateral recesses are inspected, and the medial walls of the pedicles are palpated. Introductory holes are drilled in each of the four pedicles, while a probe ensures that the medial wall remains intact. Depending on the instrumentation used, the holes are enlarged and probed; under fluoroscopic guidance, the holes are tapped, and transpedicular screws are placed. The interconnecting rods or plates, depending on the system, are then attached.

At this point, the final distraction and reduction can be achieved before the entire fixation is tightened. The wound is irrigated copiously. Some advocate the use of antibiotics in the irrigation; no studies have suggested a lower infection rate as a result of this practice.

The high-speed drill is then used to decorticate the surfaces used for fusion, which are typically the lateral part of the lateral facets, the transverse processes, and the sacral ala. The bone graft is then laid along the prepared fusion bed and compressed. Some surgeons use a variety of pastes with osteoinductive properties to hold the fusion graft and enhance the success of fusion. Long-term results on these materials appear promising. The wound is then closed in multiple layers with watertight closure of the lumbodorsal fascia over one or two drains.

A number of minimally invasive and robotic-assisted approaches have been described as well. ^{[22, 23, 24]}

Routine postoperative laboratory tests should include assessment of the hematocrit. Plain anteroposterior and lateral radiographs of the operated segment(s) are recommended. The use of postoperative braces is dependent on surgeon preference.

The patient is mobilized within 24 hours. Adequate pain relief is essential for deep breathing and early ambulation. Involvement of therapists in the patient's initial activities helps encourage and reassure the patient.

Anti-inflammatory medications (eg, steroids or ketorolac) are to be avoided, in that they may interfere with the fusion effort. If the nerve root is injured from traction or manipulation, a short course of tapered steroid therapy is warranted.

Specific complications of lumbar fusion performed via a posterolateral approach include the following:

• Injury to the nerve root - The risk is low (< 1%) but increases with more radical facetectomy and PLIF application; more commonly, transient neuropraxia from excessive retraction results in PLIF correction of high-grade spondylolisthesis
• Cerebrospinal fluid leak - The risk is reported at 2-10%, depending on the series; the highest risks are in revisions and in elderly persons with severe stenosis and friable dura
• Failure or lack of fusion and/or pseudoarthrosis - This complication occurs in 5-25% of cases; the risk is highest when interbody grafts are placed as standalone devices and lowest with the addition of posterolateral fixation with pedicle screws; smoking increases the failure rate by as much as 50%
• Failure of fixation - This complication is rare (0.5-3%) and includes interbody graft expulsion or fracture, pedicle screw pullout, fracture, or migration (usually out of the lateral pedicular wall)

General surgical complications, such as hemorrhage and infection, occur in 1-5% of patients. A risk exists of injuring retroperitoneal structures such as the iliac vessels, the sympathetic chain, or the hypogastric nerves. This risk is obviously higher with anterior approaches (ie, ALIF) but also has been observed during radical excision of the anterior annulus fibrosis and PLIF procedures.

After the routine postoperative check in 4-6 weeks, plain radiographs should be performed to evaluate the fusion and fixation if used. The patient is expected to have mild discomfort during normal motion for the first few weeks. High-level athletic activity should be avoided for up to 3 months for the fusion to heal completely.