Spinal Stenosis with Spondylolisthesis

Published on 11/04/2015 by admin

Filed under Orthopaedics

Last modified 22/04/2025

Print this page

rate 1 star rate 2 star rate 3 star rate 4 star rate 5 star
Your rating: none, Average: 0 (0 votes)

This article have been viewed 2010 times

15 Spinal Stenosis with Spondylolisthesis

Vincent J. Miele, Sumeet Vadera, Edward C. Benzel

KEY POINTS

• In the majority of cases patients with spinal stenosis and degenerative spondylolisthesis may undergo a traditional laminectomy.
• Several factors, including the mobility of the listhesis, character of the slip (lateral listhesis), presence of an associated degenerative scoliosis, and the presence of axial pain are weighted in favor of adjunct fusion.
• If fusion is required, it can be performed with or without instrumentation. Generally, instrumentation increases the morbidity of the patient.
• Factors to consider when deciding on instrumentation include the amount of instability, age of the patient, bone quality, presence of comorbidities, amount of levels requiring decompression, and factors that predict worsening of listhesis (see previous point).
• New technologies, such as biologics used to promote fusion, minimally invasive techniques, and motion preservation technology are promising but have limited data proving efficacy.

Spinal stenosis accompanied by spondylolisthesis is a common diagnosis encountered by the spinal surgeon. Although nonoperative treatment consisting of antiinflammatory medications and epidural steroid injections is effective in some patients, many patients with severe symptoms are not helped by this strategy.1,2 In the group that fails conservative therapy, decompression has been shown to be an effective treatment modality.2–4 Although numerous studies have clearly demonstrated the beneficial effects of decompressive laminectomy, the fear of creating instability often limits this procedure’s application. The concomitant presence of spondylolisthesis increases this likelihood. Controversy also persists regarding the virtues of concomitant spinal fusion in this patient population, which is often elderly. When fusion is chosen, the decision of whether or not to use instrumentation must be made. Fortunately, the management of this condition has evolved over the past several decades and numerous prospective randomized trials have been performed assessing the influence of fusion and instrumentation following decompression.

To treat a patient with spinal stenosis with degenerative spondylolisthesis, the clinician should have a basic knowledge of the epidemiology, diagnosis, and management of this condition. This chapter addresses specific situations in which individuals will have a high incidence of instability and progression of deformity without fusion. In addition, laminectomy without fusion may be considered. It will also discuss certain patient populations in which the better part of valor might be a limited decompression without fusion or a fusion without instrumentation. Finally, new techniques such as the use of biologics, motion preservation devices, and soft tissue stabilization will be discussed.

Part One: Understanding the Condition

Pathophysiology

As the spine ages, the accumulation of years of axial loading and rotational strains may lead to disc degeneration, facet arthrosis with hypertrophy, thickening or buckling of ligamentum flavum, and osteophyte formation. This cascade of degenerative changes can result in the development of central canal or foraminal narrowing with resulting neural compression characterized by low back, buttock, and lower extremity pain.1 They can also result in varying degrees of spinal instability and, depending on the anatomic predisposing factors, the vertebra develops either anterolisthesis or retrolisthesis. Spondylolisthesis, the slippage of one vertebra relative to the adjacent vertebrae, often results from asymmetric degeneration of the disc, the facet joints, or both.

Once degenerative spondylolisthesis begins, the imbalance in stress can lead to an asymmetric deformity, which further aggravates the asymmetric loading and results in a vicious circle that promotes progression of instability. As the listhesis progresses with the narrowing of the intervertebral disc, subsequent changes in the motion segment include spur formation, subchondral sclerosis, ligamentous hypertrophy and ossification, together with hypertrophic facet arthrosis. These secondary changes have a natural tendency to restabilize the motion segment.

The deformity may occur in any of three axes: axial rotation on the vertical axis, lateral translation, and anterior translation in the sagittal plane. The types of spondylolisthesis that can occur are therefore rotatory olisthesis (rotational subluxation of one vertebral body upon another), lateral subluxation, and translatory shift. A listhetic segment is defined as fixed if less than 2-mm translation occurs on flexion/extension radiographs. If a translation occurs that is greater than 2 mm, the listhetic segment is considered mobile.

Degenerative spondylolisthesis is commonly associated with symptomatic stenosis as well as degenerative scoliosis. The primary pathology in degenerative scoliosis is lateral listhesis, coupled with lateral wedging of the vertebral body and angulation secondary to asymmetric degeneration of the facet joints.

Epidemiology

Degenerative spondylolisthesis is a relatively common pathology. A recent study involving a large series in an Asian population reported an overall incidence of 8.7%. It typically is found in individuals older than 50 years. It is also more common in women than men, which is thought to be secondary to the increased ligamentous laxity in the former.

The level L4-L5 is most commonly affected overall by degenerative spondylolisthesis. Anterolisthesis is more common in the lower lumbar segments in females, whereas retrolisthesis in the upper lumbar segments is equally common in both sexes. When disc degeneration occurs, the motion segment often settles into an anterolisthesis.

Natural History

The majority of patients with a history of significant neurogenic claudication or vesicorectal symptoms have been shown to have poor outcomes without intervention. A prospective observational cohort study assessing the long-term outcomes (8- to 10-year follow-up) of patients with lumbar spinal stenosis treated either surgically or nonsurgically has demonstrated increased leg pain relief and greater back-related functional status in patients who initially received surgical treatment. Although degenerative spondylolisthesis has been shown to progress in 25% to 30% of patients, it fortunately rarely progresses to more than 30% of the subjacent vertebra. Some studies have demonstrated that as the pathology progresses and the disc space collapses, back pain can improve spontaneously.

Part Two: Clinical Decision Making

Evaluation

Patients with spinal stenosis and degenerative spondylolisthesis present with neurogenic claudication, radiculopathy, intermittent episodes of axial mechanical back pain, and vesicorectal disorder. L5 is the most commonly associated radiculopathy. This is because for a patient with spondylolisthesis at L4-L5 (the most commonly affected level), the L5 nerve root is usually compressed in the lateral recess. Less frequently, the vertebral body movement causes narrowing of the foramen and L4 nerve root compression. Specifically, this foraminal stenosis is the result of anterosuperior subluxation of the caudad superior articular facet from decreased disc height, hypertrophied ligament and disc material, and osteophyte formation in the posterolateral corner of the vertebral end plate. This can compress the exiting nerve root against the superior pedicle. The origin of the axial mechanical back pain component of the disorder can be primarily discogenic or related to facet degeneration, which is often difficult to distinguish. Generally, if the discomfort is primarily secondary to disc disease, it worsens with forward bending. Additionally, the patient often complains of a catching pain in the low back that tends to climb up the body that occurs when rising from a forward bent posture. The patient also often supports his or her weight by placing his or her hands on the knees and thighs. Pain that arises primarily from the facet joints is often worsened by extension and rotation of the spine and is often associated with paravertebral tenderness.

Obviously, a thorough vascular examination is imperative to identify a peripheral vascular component of the symptoms. A patient presenting with atypical symptoms (e.g., night pain, rest pain) should be evaluated for other etiologies, such as a tumor, acute compression type fracture, or infection.

Imaging Studies

Imaging studies used to evaluate spinal stenosis with degenerative spondylolisthesis should focus on two goals. First, determining the extent of central and foraminal stenosis and secondary neural impingement. Magnetic resonance imaging (MRI) is most useful in this regard and can help differentiate between varying causes of stenosis, such as synovial cysts and ligamentum flavum hypertrophy. If MRI is contraindicated, a computed tomography (CT) myelogram can also be used. This information is needed to design an appropriate strategy to treat the patient’s radicular complaints. Secondly, imaging should focus on quantifying the amount of instability present in the spondylolisthetic segment and specific characteristics that portend an increased risk of progression. This information is necessary when determining how aggressive a decompression should be attempted and if additional stabilization techniques will need to be employed. These studies should include upright weight-bearing anteroposterior and lateral radiographs of the lumbar spine and pelvis, as well as flexion and extension views. An alternative method is to compare standing lateral radiographs with radiographs taken with the patient in supine hyperextension using a pillow. Lack of motion suggests a component of secondary stabilization. Though it is unclear what magnitude of slip is considered unstable, most studies define instability as listhesis greater than 2 mm.

Specific Patient Populations and Situations

Elderly

The aging baby boomer generation is leading a shift in demographics toward a “gray society,” and over the next 25 years a significant proportion of the population in industrialized societies will be over 65 years old. Since both symptomatic spinal stenosis and spondylolisthesis typically appear between the fifth and seventh decades of life (40-60 years), these conditions frequently coexist in this populace, and many patients with these conditions will become surgical candidates. While decompression of disabling lumbar spinal stenosis may lead to a significant improvement in quality of life, concerns about potential medical complications in this sometimes fragile population and uncertainty about the expected outcome of operative treatment make many surgeons apprehensive about big surgeries, such as decompression with arthrodesis.

Some controversy exists as to whether age should be considered an independent risk factor for surgery. Many authors report no difference in outcome or rate of complications between elderly and younger patients of comparable health.7 Therefore advanced age alone should not be a contraindication for surgery. Some studies, on the other hand, have demonstrated that increasing age can be an independent risk factor for surgery, especially if the patient is older than 60 years.5 One such study noted a 41% complication rate (14% major and 27% minor) for patients 41 to 60 years of age and a 64% complication rate (24% major and 40% minor) for those 61 to 85 years of age (27). Pulmonary complications were the most common major complications and genitourinary problems were the most common minor complications. Age more than 60 years was therefore found to be a significant risk factor for perioperative complication.

It has also been reported that decompressive surgery in the elderly population can be effective without the need for supplemental fusion, and many authors therefore do not recommend fusion in patients older than 70 years. This is partly because the risk of developing postoperative instability in this age group appears to be small because of some intrinsic stability afforded by the spondylosis and spondylarthrosis that occur as the spine ages as well as the decreased activity level of this population.5

If decompression without supplemental fusion is performed in this population, care should be taken to limit the number of levels decompressed. It has been shown that the probability of developing postoperative spondylolisthesis increases with the number of levels decompressed; (6% for 2 levels progressing to 15% for 3 or more levels). Other strategies (which will be discussed later in this chapter) that may be employed in the elderly include noninstrumented fusions and minimal bone removal.

Multiple Comorbidities

Patients who have multiple comorbidities, such as cardiac disease, vascular disease, or diabetes have an increased risk for postoperative complications.6,7 The preoperative evaluation and optimization of patients with these conditions is critical. The addition of an arthrodesis increases the length of anesthesia as well as the amount of blood loss. Both of these factors can delay recovery time, and patients with multiple comorbidities are therefore more likely to require an extended rehabilitation period. These factors should all be considered when deciding upon the advisability of supplemental fusion with decompression. Finally, for patients with a limited life expectancy, treatment should be focused on obtaining an immediate improvement in quality of life without subjecting the patient to a prolonged and painful recovery period.

Several studies in the literature have examined the relationship between preoperative comorbidities and postoperative complications. Although there is a link between certain risk factors and postoperative mortality, increasing American Society of Anesthesiology (ASA) physical status class has been shown to be one of the best independent predictors of mortality. Previous studies have reported an increasing rate of postsurgical mortality with increase in the ASA class. In fact, increasing morbidity and mortality rates have been prospectively demonstrated with an increase in the ASA class in a large population where the mortality rate increased from zero to 7.2% from ASA class 1 to ASA class 4, respectively.7

Osteoporosis

Bone quality is a major determinant of success in all fusion procedures, especially those involving instrumentation. A mild spondylolisthesis can progress and become more symptomatic as osteoporosis worsens, as commonly occurs in postmenopausal females. As the vertebrae weaken, the asymmetric load can cause increasing deformity and de novo scoliosis, which can increase the patient’s symptoms.

Osteoporotic bone is a relative contraindication to instrumented fusion because of the difficulty in obtaining and maintaining adequate fixation at the bone–screw interface. Although variations in technique such as the use of larger diameter screws, screw threads with more aggressive pitch to improve pull-out strength, and augmentation of the bone–screw interface with methylmethacrylate have been advocated, failures of fixation are still likely.6

A conundrum thus exists with respect to treatment of symptomatic stenosis in a patient with spondylolisthesis: the structural integrity of an already unstable motion segment can be further compromised by laminectomy, and it can be difficult to reliably achieve fixation with instrumentation. Therefore an already challenging situation can be made more difficult, and care should be taken to minimize disruption of posterior supporting structures during the procedure.

Indications for Fusion

The indications for surgical management are persistent or recurrent back pain with leg pain or neurogenic claudication, leading to a significant reduction in quality of life, despite a reasonable trial of nonsurgical treatment (>3 months); progressive neurologic deficit; and bladder or bowel symptoms resulting from neurologic compression.5 Surgical options vary from decompression alone to fusion with or without instrumentation. More recent additions to the surgical armamentarium include ligament stabilizers and biologic agents. There continues to be a tremendous amount of controversy regarding the efficacy of fusion in degenerative disease resulting in low back pain (LBP).8,9

Lateral Listhesis

Though several forms of degenerative spondylolisthesis commonly occur in association with stenosis, of particular concern is the lateral subluxation of one vertebral body upon another. This requires both minimizing structural disruption during decompression and also close follow-up for progression of deformity if instrumented fusion is not performed.

Concomitant de Novo Scoliosis—Significant Curve and Progressing Curve

Degenerative de novo scoliosis (DDS) refers to the development of spinal curvatures in adults without a previous history of scoliosis. This occurs secondary to degeneration of facet joints, joint capsules, discs, and ligaments, which may create monosegmental or multisegmental instability. The curvatures in DDS are generally slowly progressive and not severe, but are commonly associated with back and radicular leg pain, as well as neurogenic claudication. DDS and stenosis commonly occur in tandem for several reasons. They both have high individual frequency as patients age and therefore commonly occur together. In addition, the scoliotic spine responds to the stresses of being biomechanically compromised with facet arthrosis and ligamentum flavum buckling or thickening, both of which decrease foraminal and central canal diameter.

When nonoperative management of patients with this combination of pathologies fails, decompressive procedures are often required. Patients with DDS who undergo laminectomy commonly require concomitant fusion since removal of the posterior elements can compromise spinal stability. In addition, the traditional aim of surgery is to both decompress the compromised neural elements and to create a balanced and stable spine in both the coronal and sagittal planes. As with other conditions, the surgical morbidity of DDS is significantly greater when the decompressive surgery is combined with fusion.5,6

Consideration must be given to both the magnitude of the DDS curve and whether or not it is progressive. Although slow curve progression may occur without surgery, more significant and rapid progression is likely following decompression without instrumented fusion.

The location and amount of decompression within the DDS curve can influence its stability. For instance, if decompression is performed at the apex of the curve, particularly on its concavity, progression of the curve is more likely than if it occurs further from the apex. Similarly, instability can also be compromised when a decompression is performed at the bottom of a rigid curve, where it transitions to a mobile part of the lumbar spine— for example, at L4-L5 or L5-S1. In this case, the presence of a rigid curve above a decompressed segment may result in translation of the fused segment, causing the spine to fall out of balance.

Axial Pain

Although the progression of spondylolisthesis is usually slow it commonly results in significant axial and radicular pain. One of the most frequent indications for its surgical treatment is intractable pain. As is generally true in spinal surgery, success is more likely with radicular pain than with axial pain. The treatment of axial pain often involves correction or stabilization of the deformity. Thus, fusion with instrumentation is usually required.

Radicular pain accompanying axial back pain is commonly the result of nerve root compression in the concavity of the curve as a result of foraminal narrowing. It may also result from traction of the nerve root in the convexity of the curve. While this type of radicular pain may be treated with decompressive procedures, such as laminectomy or foraminotomy, it can be difficult to assure adequate foraminal decompression within the concavity without distraction via instrumentation.

Nonfusion Decision Making

Laminectomy is the initial surgical treatment for degenerative spondylolisthesis. Several studies have shown the clinical effectiveness of performing a laminectomy, with up to 80% good or excellent outcomes. Degenerative spondylolisthesis may progress beyond 50% following laminectomy without concomitant fusion. Even when the listhesis has not progressed, a revision decompression at the same level often requires significant removal of the remaining facet joints, necessitating instrumented fusion.

Decompressive surgery without instrumented fusion has less perioperative morbidity than when combined with fusion and can be performed in some fragile populations. Two such groups that are an increasing segment of society are the elderly and those with multiple comorbidities. Decompression alone may also be considered in the patient with osteoporotic bones.

Evaluation of these patients should include determining whether the patient has any associated spondylolisthesis—especially lateral listhesis. In addition the magnitude of the curve and signs of progression must be considered. Finally, the patient’s symptoms must be taken into account. Those without a significant axial pain component may be better candidates for decompressive surgery without fusion than patients with axial pain.

Part Three: Management

Nonsurgical

As with the majority of spinal disorders, it is appropriate to attempt a nonsurgical solution first. Most patients with symptomatic spinal stenosis and degenerative spondylolisthesis respond to nonsurgical management and do not require surgery. Conservative treatments for spinal stenosis with degenerative spondylolisthesis include nonsteroidal antiinflammatory drugs, membrane stabilizer medications (e.g., gabapentin, pregabalin), activity modification, and physical therapy.10

The mainstay of physical therapy for this condition emphasizes flexion exercises, back strengthening, and aerobic conditioning. Aerobic conditioning can be somewhat problematic in this population, but exercises performed in flexion, such as stationary bicycle, enlarge the neural foramen and central canal, minimizing the symptoms of neurogenic claudication. Passive modalities such as ultrasound, massage, heat, and spinal manipulation are useful in that they may temporarily improve symptoms, but their efficacy has not been verified by prospective studies with long-term follow-up.10

Surgical

Fusion Options with or without Instrumentation

Although surgical decompression alone often improves symptoms in the patient with spinal stenosis and degenerative spondylolisthesis, numerous studies have demonstrated the benefits of concomitant fusion, either noninstrumented or instrumented.4,5,11 For stabilizing the spine, instrumented fusions are superior to uninstrumented fusions. However, they are not always feasible, especially in the elderly population with osteoporotic bones. When a fusion is desired but instrumentation is contraindicated, the benefit of noninstrumented fusions are that they generally require less dissection and blood loss and require less surgical time under anesthesia.

Decompression and Noninstrumented Posterolateral Fusion

Concomitant fusion improves long-term outcomes when a decompressive laminectomy is performed for spinal stenosis with degenerative spondylolisthesis. The placement of instrumentation increases morbidity, as well. It seems logical that un-instrumented posterolateral fusion could provide a good compromise between the two options.9 Though much of the morbidity associated with preparation of the fusion bed would remain (increased dissection and pain, increased anesthesia time, and blood loss), the additional trauma and time of instrumentation placement would be avoided. Prospective studies of patients with degenerative spondylolisthesis who underwent decompression and uninstrumented dorsolateral fusion versus patients undergoing decompression alone have in fact demonstrated significantly better outcomes. Of note, although this procedure is associated with a high pseudoarthrosis rate (up to 36%), this did not affect patient outcomes. This is thought to be the result of stiffening of the spine and motion restriction due to a stable pseudarthrosis.11,12

The procedure does have some disadvantages. As mentioned above, the patient must still undergo the extensive dissection of the lateral areas over the transverse processes. The fusion itself is negatively impacted by the relatively poor vascularity of the transverse processes as well as the constant intertransverse graft motion during activities of daily living secondary to the intervening juxtaposed paraspinous and quadratus lumborum muscles. Finally, dorsolateral fusion requires consolidation of bone over a fairly large distance (several centimeters) between transverse processes.

Fusion with Biologics

Newer biologics have given the surgeon the advantage of relatively improved fusion rates using less invasive techniques. Numerous prospective randomized studies of recombinant bone morphogenetic proteins (recombinant human bone morphogenetic protein-2 [rhBMP-2] and recombinant human bone morphogenetic protein-7 [rhBMP-7]) have been performed. The safety, effectiveness, and radiographic outcomes of OP-1 (BMP-7) putty with autogenous iliac crest bone graft used for laminectomy and noninstrumented posterolateral fusion for symptomatic lumbar stenosis associated with degenerative spondylolisthesis have been reported and are encouraging.

A prospective randomized controlled multicenter clinical study with a 2-year follow-up has reported clinical success, defined as a 20% improvement in the preoperative Oswestry score. Success was achieved in 85% of patients treated with OP-1 putty versus 64% of patients treated with autograft. In addition, a successful posterolateral fusion was achieved in 55% of patients treated with OP-1 putty and in 40% of patients treated with autograft. Importantly, a 36-item Medical Outcomes Study Short-Form General Health Survey (SF-36). SF-36 scores showed similar clinical improvement in both groups.

A second prospective randomized clinical study has evaluated the use of rhBMP-2 to achieve posterolateral spine fusion in patients with a grade I spondylolisthesis and single level degenerative disc disease that were scheduled to undergo single level posterolateral lumbar arthrodesis. The study compared patients undergoing autogenous iliac crest bone graft with pedicle screw instrumentation, rhBMP-2 with pedicle screw instrumentation, and rhBMP-2 only with no instrumentation. The study demonstrated a radiographic fusion rate of 40% in the autogenous iliac crest bone graft with pedicle screw instrumentation, 100% in patients that received rhBMP-2 with pedicle screw instrumentation, and 100% in the rhBMP-2–only group.13 More importantly, the clinical outcomes improved faster and to a greater degree in the rhBMP-2–only group. The surgical time was significantly less secondary to the elimination of the time required for bone graft harvest and placement of internal fixation.

Decompression and Posterolateral Fusion with Instrumentation

The most effective method of achieving “stability” following decompression is the addition of instrumentation.11 A prospective randomized study comparing the results of decompression and arthrodesis alone with those of decompression and arthrodesis combined with instrumentation has shown that the addition of spinal instrumentation improved the fusion rate (82%, instrumented versus 45%, noninstrumented).4 Although achieving a solid fusion appeared to be less important, since no significant difference was found in clinical outcomes, more recent longer term (5- to 14-year) follow-up studies have reported that patients with pseudarthrosis did not do as well as those that achieved solid fusion.4,11 The complication rates, revision rates, radiographic results, and patient satisfaction at 5-year follow-up were reviewed for patients following segmental posterior instrumented fusion with decompression in patients with lumbar degenerative spondylolisthesis and showed that no patient had a neurologic deficit, evidence of symptomatic pseudarthrosis (i.e., pain, lucency, loose instrumentation), or recurrent stenosis at the fused segment.7

Unfortunately, posterolateral fusion requires a large dissection for the preparation of the fusion bed, which is associated with increased pain, bleeding, time in surgery, and recovery. In addition to this, instrumentation further increases the morbidity of the surgery.12

Facet Fusion

Facet joints normally function by bearing load and allowing motion, while restricting excessive motion. Fusion of the facet can be accomplished with or without instrumentation, and can substantially reduce the pain and morbidity associated with posterolateral fusion. Though studies have demonstrated that instrumented facet fusions can have a 96% fusion rate by CT scan, this is not as strong as a posterolateral fusion, and a functional outcome assessment was not reported.

Uninstrumented facet fusions are becoming more popular because of their simplicity and minimal additional dissection requirement. They can be performed using locally harvested autograft placed into the facet joint or with allograft bone dowels that are currently available from several companies. Unfortunately, no powerful studies are available on the effectiveness of uninstrumented facet fusion in stabilizing the spine.

Because a varying degree of disruption of the facet capsule (which in itself is stabilizing) must occur to perform a facet fusion, a negative to this procedure is that if a fusion does not occur, the spine will have in fact lost stability from the procedure. Additionally, if wide decompressions are performed, the added stress placed on the facet joint can lead to fracture of the thinned pars interarticularis and complete incompetency of the joint. Obviously, if any type of facet fusion is going to be attempted, care should be taken to preserve as much of the pars interarticularis as possible bilaterally.

Fusion with Transforaminal Lumbar Interbody Graft

The addition of interbody support helps to restore the biomechanical advantages of a solid anterior column and provides an increased fusion surface area. These advantages could translate into an increased rate of fusion and improved patient outcomes. Unfortunately, no prospective randomized studies have been performed comparing decompression with transforaminal lumbar interbody fusion to decompression with instrumented posterolateral fusion. Until such a study is performed, it will be more difficult to justify the added dissection and anesthesia time required in an older patient population.

Nonfusion Options

Laminectomy

Many studies have demonstrated the efficacy of dorsal decompression for alleviating the symptoms of spinal stenosis.1–3 Although laminectomy is a relatively well-tolerated procedure, the incidence of postoperative instability (increased translation and loss of alignment) has been reported to be as high as 50% in patients undergoing laminectomy for spinal stenosis and even higher in patients with degenerative spondylolisthesis.5,10

The standard surgical treatment for lumbar spinal stenosis consists of a decompressive laminectomy accompanied by partial medial facetectomy and foraminotomy, as needed. It is important to preserve as much of the facet joint as possible. Similarly, preservation of the pars interarticularis is essential to maintain stability and minimize the need for instrumentation. Therefore it is often helpful to expose and visualize the pars interarticularis in order to avoid its inadvertent disruption during the decompression.

When performed properly, the risk of postoperative instability following this procedure is less than 2% in patients without degenerative scoliosis. The risk of instability increases in patients with degenerative scoliosis, especially as the magnitude of the curve increases. Patients with curves greater than 20 degrees are at a higher risk of curve progression and often require prophylactic fusion. The risk of worsening postoperative spondylolisthesis also increases with the number of levels decompressed, ranging from 6% for 2 levels to 15% for 3 or more levels.

Laminotomy or Interlaminar Fenestration

Interlaminar fenestration or laminotomy can provide significant neural decompression in select patients with minimal structural disruption, and can be especially useful in the treatment of lateral recess stenosis. These procedures emphasize the preservation of stabilizing structures such as the interspinous and supraspinous ligaments, spinous processes, and functionally important parts of facet joints. Interlaminar fenestration is accomplished by trimming bone around the interlaminar spaces of involved segments along with removal of the ligamentum flavum and medial portion of the facet joint. The fenestration extends laterally to decompress affected nerve roots with the preservation of the adjoining laminae, spinous processes, interspinous ligaments, and facet joints.

Foraminotomy

Foraminotomy is often required when the neural foramen is narrowed as a result of disc space collapse or facet arthropathy. As with other decompressive procedures, aggressive foraminotomy can destabilize the spine, especially in the presence of degenerative scoliosis or spondylolisthesis, and can result in an increase in the magnitude of slip or rate of curve progression. Therefore care must be taken to minimize facet disruption by limiting the facetectomy to the medial one third of the facet joint and to preserve the pars interarticularis if possible. Decompression of the nerve root on the concavity of a curve, which often has significant foraminal narrowing, is often challenging and may not be feasible.

Restorative Laminoplasty

Biomechanically, the vertebral arch, supraspinous and interspinous ligaments provide a tethering constraint during anterior flexion and support for the dorsolumbar fascia and muscles. In order for the posterior elements to provide support, the supraspinous and interspinous ligaments with their bony attachments must be intact. It has been demonstrated that extensive laminectomy can lead to instability if these points of attachment are removed.

Spinal canal enlargement by restorative laminoplasty, in which osteotomized vertebral arches are repositioned rather than removed, can provide an acceptable alternative to fusion. Theoretically, this method of decompression could be more effective in preventing postoperative instability than multilevel fenestration, because it involves less extensive dissection of the laminae and facet joints. As an alternative to decompression with fusion, it has been used in patients with both degenerative spondylolisthesis and degenerative scoliosis with 2-year follow-up studies showing no exacerbation of spondylolisthesis or scoliosis, nor the onset of other instability

Whereas favorable results have been demonstrated using laminoplasty, 2-year outcome studies have demonstrated that symptomatic improvement is less likely in patients with degenerative scoliosis, particularly with more severe scoliosis. Notably, the number of restored vertebral arches has not been found to have significant correlations on overall improvement rate. Similarly it has not been shown to be effective in patients with degenerative spondylolisthesis. Its benefit in lateral spondylolisthesis has not been evaluated.

Minimally Invasive Techniques

Minimally invasive surgery (MIS) is becoming more popular in the treatment of many spinal disorders. With these techniques, a decompressive laminectomy, laminotomy, or foraminotomy is performed with minimal tissue dissection via the use of special retractor systems, unilateral approaches, and endoscopes. These techniques can be used to insert spinal instrumentation, or for decompression procedures alone. Although MIS decompression has many theoretical advantages with respect to minimizing tissue disruption and preserving stability, such benefits have not been conclusively proven. In addition, they can be associated with a steep learning curve and prolonged operative time, which may be an important issue in the elderly and medically fragile patient. As with any surgical procedure performed through a small portal, orientation can be difficult, and therefore an unintentionally aggressive facet resection or damage to the pars interarticularis could occur if landmarks are not properly recognized.

Motion-Sparing Technologies

Recently, new technologies have become available that are primarily categorized as “motion preservation devices” but may have some use in minimizing destabilization while decompressing the stenotic patient. The literature is sparse and has mixed results on many of these device’s efficacy. More follow-up is needed to determine their ultimate role and utility in patients with spondylolisthesis.

The goal of surgery with many of these devices is to provide semirigid stabilization, interspinous widening, or both, in an attempt to stabilize the spine, provide for neural decompression, and avoid the need for fusion. They mainly come in two varieties: interspinous process distraction devices and semirigid fixation between pedicle screws. A prospective study of patients with degenerative spondylolisthesis who underwent decompression of the spine, with and without stabilization, using the Graf system (Surgicraft, Worcestershire, UK) reported no statistically significant difference between decompression alone and decompression with stabilization using the Graf system. Additionally, stabilization using the Graf system was not effective in reducing the recurrence of leg symptoms. Another prospective clinical study evaluated whether elastic stabilization with the Dynesys system (Zimmer Spine, Minneapolis, Minn.) provided enough stability to prevent progression of spondylolisthesis after decompression for spinal stenosis with degenerative spondylolisthesis. Radiographically, no significant progression of spondylolisthesis was detected. The authors concluded that in an elderly population with spinal stenosis and associated degenerative spondylolisthesis, dynamic stabilization with this system in addition to decompression results in clinical outcomes similar to those seen with established protocols using decompression and fusion with pedicle screws. Of note, although the implant failure rate was fairly high (17%), none of these instances were clinically symptomatic.

Interspinous distraction devices prevent extension of the instrumented level and try to replicate the relief the patient obtains when they lean forward in flexion. A randomized controlled study of such a device, X STOP (St. Francis Medical Technologies, Alameda, Calif.), in patients with neurogenic claudication and degenerative spondylolisthesis, reported overall clinical success in 63% of the patients treated with the X STOP versus 13% success in the nonsurgical group. A common cause of failure of these devices is that their modulus of elasticity is usually far greater than the adjacent spinous processes, which leads to subsidence of the device into the spinous processes as well as fracture of the bone.

Conclusion

Degenerative spondylolisthesis and spinal stenosis commonly occur in tandem and often cause back and radicular leg pain or neurogenic claudication. It is most common in elderly women at L4-L5. It is also most common in a patient population with multiple comorbidities and poor bone quality. Though many with this condition who undergo laminectomy also require fusion, decompressive surgery without instrumented fusion is an option in select patients and is better tolerated with less perioperative morbidity in this population of medically fragile patients.

The severity of a patient’s symptoms and the presence of any neurological deficits must be taken into account. Evaluation of these patients should include determining the presence or absence of associated degenerative scoliosis and characteristics of the listhesis that portend less stability (lateral listhesis). In patients with an associated scoliosis, the magnitude and progression of the curve must be determined.

While traditional laminectomy can usually be performed without destabilizing the spine, care must be taken to spare the pars interarticularis and as much of the facet(s) as possible. Procedures such as laminotomy, interlaminar fenestration, foraminotomy, and restorative laminoplasty may be sufficient for neural decompression without significantly compromising structural integrity. Likewise, newer minimally invasive techniques have the potential to preserve more structurally important soft tissue. The ultimate role that these procedures play in the surgical treatment of patients with spinal stenosis and degenerative scoliosis remains to be proven.

When decompressive procedures are performed without fusion, a radical decompression should be avoided at the base or apex of a curve in order to minimize risk of curve progression. Curves that are greater than 20 degrees, demonstrate progressive deformity, or fit both criteria, are not good candidates for decompression without fusion. Finally, patients with significant axial pain are less likely to experience improvement in their back pain without concomitant fusion. Recent short-term studies have also shown the efficacy of adding biologics to aid in obtaining a solid fusion. Future technologies, such as dynamic stabilization and interspinous distraction devices, will require long-term prospective studies to prove their role in managing the patient with degenerative scoliosis and spondylolisthesis.

References

1. Sengupta D.K., Herkowitz H.N. Lumbar spinal stenosis. Treatment strategies and indications for surgery. Orthop. Clin. North Am.. 2003;34:281.

2. Katz J.N., Lipson S.J., Larson M.G., et al. The outcome of decompressive laminectomy for degenerative lumbar stenosis. J. Bone Joint Surg. Am.. 1991;73:809.

3. Caputy A.J., Luessenhop A.J. Long-term evaluation of decompressive surgery for degenerative lumbar stenosis. J. Neurosurg.. 1992;77:669.

4. Bridwell K.H., Sedgewick T.A., O’Brien M.F., et al. The role of fusion and instrumentation in the treatment of degenerative spondylolisthesis with spinal stenosis. J. Spinal Disord.. 1993;6:461.

5. Matsunaga S., Ijiri K., Hayashi K. Nonsurgically managed patients with degenerative spondylolisthesis: a 10- to 18-year follow-up study. J. Neurosurg.. 2000;93:194.

6. Benz R.J., Ibrahim Z.G., Afshar P., et al. Predicting complications in elderly patients undergoing lumbar decompression. Clin. Orthop. Relat. Res.. 2001:116.

7. Wang M.Y., Green B.A., Shah S., et al. Complications associated with lumbar stenosis surgery in patients older than 75 years of age. Neurosurg. Focus. 2003;14:e7.

8. Fischgrund J.S. The argument for instrumented decompressive posterolateral fusion for patients with degenerative spondylolisthesis and spinal stenosis. Spine. 2004;29:173.

9. Phillips F.M. The argument for noninstrumented posterolateral fusion for patients with spinal stenosis and degenerative spondylolisthesis. Spine. 2004;29:170.

10. Murphy D.R., Hurwitz E.L., Gregory A.A., Clary R. A non-surgical approach to the management of lumbar spinal stenosis: a prospective observational cohort study. BMC Musculoskelet. Disord.. 2006;7:16.

11. Kornblum M.B., Fischgrund J.S., Herkowitz H.N., et al. Degenerative lumbar spondylolisthesis with spinal stenosis: a prospective long-term study comparing fusion and pseudarthrosis. Spine. 2004;29:726.

12. Ghogawala Z., Benzel E.C., Amin-Hanjani S., et al. Prospective outcomes evaluation after decompression with or without instrumented fusion for lumbar stenosis and degenerative Grade I spondylolisthesis. J Neurosurg Spine. 2004;1:267.

13. Boden S., Kang J., Sandhu H., et al. Use of recombinant human bone morphogenetic protein-2 to achieve posterolateral lumbar spine fusion in humans: A prospective, randomized clinical pilot trial 2002 Volvo Award in clinical studies. Spine. 2002;27:2662.

Related posts:

Default ThumbnailThe Role for Biologics in the Aging Spine A Case Study Approach to the Role of Spinal Deformity Correction in the Aging Spine Embryology of the Spine The Role of Dynamic Stabilization and the Aging Spine Infections of the Cervical Spine Vessel-X