You are in: eMedicine Specialties > Orthopedic Surgery > SPINE Spondylolisthesis, Spondylolysis, and SpondylosisArticle Last Updated: Feb 1, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Amir Vokshoor, MD, Staff Neurosurgeon, Department of Neurosurgery, Spine Surgeon, Diagnostic and Interventional Spinal Care, St. John's Health Center Amir Vokshoor is a member of the following medical societies: Alpha Omega Alpha, American Association of Neurological Surgeons, and American Medical Association Coauthor(s): Ali R Jamali, MD, Assistant Professor of Orthopedic Surgery and Internal Medicine, Department of Orthopedic Surgery, Eastern Virginia Medical School Editors: Lee H Riley III, MD, Chief, Division of Orthopedic Spine Surgery, Assistant Professor, Departments of Orthopedic Surgery and Neurosurgery, Johns Hopkins University; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; William O Shaffer, MD, Associate Professor & Residency Program Director, Department of Orthopedic Surgery, University of Kentucky at Lexington; Dinesh Patel, MD, FACS, Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital; Mary Ann E Keenan, MD, Professor, Vice Chair for Graduate Medical Education, Department of Orthopedic Surgery, University of Pennsylvania School of Medicine; Chief of Neuro-Orthopedics Program, Department of Orthopedic Surgery, Hospital of the University of Pennsylvania Author and Editor Disclosure Synonyms and related keywords: subluxation, spondyloptosis, spine, vertebra, vertebrae, spinal instability, radiculopathy, neurogenic claudication, postural abnormality, gait abnormality, slip progression, back pain INTRODUCTIONSection 2 of 12
  Spondylolisthesis refers to the forward slippage of one vertebral body with respect to the one beneath it. This most commonly occurs at the lumbosacral junction with L5 slipping over S1, but it can occur at higher levels as well. It is classified based on etiology into 5 types: congenital or dysplastic, isthmic, degenerative, traumatic, and pathologic (Wiltse, 1976). Many cases can be managed conservatively. However, in persons with incapacitating symptoms, radiculopathy, neurogenic claudication, postural or gait abnormality resistant to nonoperative measures, and significant slip progression, surgery is indicated. The goal of surgery is to stabilize the spinal segment and decompress the neural elements if needed. History of the ProcedureIn 1854, Killian coined the term spondylolisthesis to describe the gradual slippage of the L5 vertebra due to gravity and posture. In 1858, Lambi demonstrated the neural arch defect (absence or elongation of pars interarticularis) in isthmic spondylolisthesis. Albee and Hibbs separately published their initial work on spinal fusion. Their methods were applied quickly to cases involving trauma, tumors, and, later, scoliosis. In the latter half of the 20th century, spinal fusion was used increasingly to treat degenerative disorders of the spine, including degenerative spondylolisthesis and degenerative scoliosis. ProblemSpondylolisthesis is the forward slippage of one vertebra on another. This may or may not be associated with gross instability of the spine. Some individuals remain asymptomatic even with high-grade slips, but most complain of some discomfort. It may cause any degree of symptoms, from minimal symptoms of occasional low back pain to incapacitating mechanical pain, radiculopathy from nerve root compression, and neurogenic claudication. FrequencyThe incidence of isthmic type (see Etiology for definition) of spondylolisthesis is believed to be approximately 5% based on autopsy studies. Degenerative spondylolisthesis is observed more frequently as the population ages and occurs most frequently at the L4-L5 level. Up to 5.8% of men and 9.1% of women are believed to have this type of listhesis. EtiologyThe etiology of spondylolisthesis is multifactorial. A congential predisposition exists in types 1 and 2, and posture, gravity, rotational forces, and high concentration of stress loading all play parts in the development of the slip. The following scheme of spondylolisthesis types, based on etiology, is adapted from Wiltse et al (1961, 1976):
PathophysiologySpondylolisthesis can be graded based on the amount of vertebral subluxation in the sagittal plane, as adapted from Meyerding (1932):
The dysplastic type occurs from a neural arch defect in the upper sacrum or L5. In this type, 94% of cases are associated with spina bifida occulta. A high rate of nerve root compression at the S1 foramen exists, although the slip may be minimal (ie, grade 1). The pars interarticularis, or isthmus, is the bone between the lamina, pedicle, articular facets, and the transverse process. This portion of the vertebra can resist significant forces during normal motion. The pars may be congenitally defective (eg, in spondylolytic subtype of isthmic spondylolisthesis) or undergo repeated stress under hyperflexion and rotation, resulting in microfractures. If a fibrous nonunion forms from ongoing insult, elongation of the pars and progressive listhesis results. This occurs in the second and third subtypes of type 2 (isthmic) spondylolisthesis. These typically present in the teenage or early adulthood years and are most common at L5-S1. A unilateral pars defect (spondylolysis) may not demonstrate any degree of slippage; thus, a patient may have spondylolysis without spondylolisthesis. The reverse is also true as in the degenerative-type slips described below. Biomechanical factors are significant in the development of spondylolysis leading to spondylolisthesis. Gravitational and postural forces cause the greatest stress at the pars interarticularis. Both lumbar lordosis and rotational forces are also believed to play a role in the development of lytic pars defects and the fatigue of the pars in the young. An association exists between high levels of activity during childhood and the development of pars defects. Genetic factors also play a role. In the degenerative type, intersegmental instability is present as a result of degenerative disc disease and facet arthropathy. These processes are collectively known as spondylosis (ie, acquired age-related degeneration). The slip occurs from progressive spondylosis within this 3-joint motion complex. This typically occurs at L4-5, and elderly females are most commonly affected. The L5 nerve root is usually compressed from lateral recess stenosis as a result of facet and/or ligamentous hypertrophy. In the traumatic type, any part (usually not pars) of the neural arch can be fractured, leading to the unstable vertebral subluxation. Pathologic spondylolisthesis results from generalized bone disease, which causes abnormal mineralization, remodeling, and attenuation of the posterior elements leading to the slip. ClinicalThe clinical presentation differs, depending on the type of slip and the age of the patient. During the early years of life, the presentation is one of mild low back pain that occasionally radiates into the buttocks and posterior thighs, especially during high levels of activity. The symptoms rarely correlate with the degree of slip, although they are attributable to segmental instability. Neurologic signs often correlate with the degree of slippage and involve motor, sensory, and reflex changes corresponding to nerve root impingement (usually S1). Progression of listhesis in these young adults usually occurs in the setting of bilateral pars defects and can be associated with the following physical findings:
The patient with degenerative spondylolisthesis is typically older and presents with back pain, radiculopathy, neurogenic claudication, or a combination of these symptoms. The slip is most common at L4-5 and less common at L3-4. The radicular symptoms often result from lateral recess stenosis from facet and ligamentous hypertrophy and/or disc herniation. The L5 nerve root is affected most commonly and causes weakness of the extensor hallucis longus. Concomitant central stenosis and neurogenic claudication may or may not exist. The cause of claudication symptoms during ambulation is multifactorial. The pain is relieved when the patient flexes the spine by sitting or by leaning on shopping carts. Flexion increases canal size by stretching the protruding ligamentum flavum, reduction of the overriding laminae and facets, and enlargement of the foramina. This relieves the pressure on the exiting nerve roots and, thus, decreases the pain. INDICATIONSSection 3 of 12
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. When evaluating a patient, many factors, such as age, degree of slip, and risk of slip progression, must be considered. 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 higher risk of slip progression:
However, many young patients are treated with 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. Indications for surgical intervention (fusion) are as follows:
RELEVANT ANATOMYSection 4 of 12
In persons with congenital-type spondylolisthesis, dysplastic articular facets predispose the spinal segment to listhesis due to their inability to resist anterior shear stress. The pars may be intact, or it may undergo microfractures. Thus, it may not be the initiator of listhesis in dysplastic types. The risk of slip progression is high. The pars interarticularis, or isthmus, resists significant forces during normal motion. The pars may be congenitally defective (isthmic spondylolisthesis is spondylolysis) or undergo repeated stress under hyperflexion and rotation resulting in microfractures. Lumbar lordosis, gravity, posture, high-intensity activities (eg, gymnastics), and genetic factors all play a role in the slip development. If a fibrous nonunion forms from ongoing insult, elongation of the pars and progressive listhesis results; this is observed in another subtype of type 2 (isthmic) spondylolisthesis. In persons with spondylolysis, 30-50% are believed to progress to spondylolisthesis. The most common location is at L5-S1. Degenerative spondylolisthesis results from intersegmental instability. The pathophysiology of disc degeneration and facet arthropathy has been investigated extensively; however, the nature and etiology of pain generation in the absence of canal or lateral recess stenosis is still debated. Degeneration of the annulus fibrosis results in radial tears through which a posteriorly migrated nucleus pulposus can herniate. Degeneration of the disc may also lead to changes affecting the stability of the spinal motion segment, thus affecting the articular facets. Disc desiccation places greater stress on the facets, which are then subjected to shear forces. The subluxation occurs as a result of progressive facet incompetence. This type most commonly occurs at L4-5 and L3-4. CONTRAINDICATIONSSection 5 of 12
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 coumadin, or antiplatelet therapy, can make the risk of hemorrhage much higher than routinely expected. Antiplatelet therapy should be discontinued 3-5 days prior to the procedure. Coumadin should be stopped 5-7 days prior to the procedure, and a prothrombin time result within 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. WORKUPSection 6 of 12
Lab Studies
Imaging Studies
TREATMENTSection 7 of 12
Medical therapyConservative measures are aimed at symptomatic relief and include the following:
The likelihood of successful nonoperative treatment is high, especially in the younger patients. In older patients with low-grade slips resulting from disc degeneration, traction has been used with some success. The authors recommend that any manipulation or traction be performed under the care of a physician 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 disc disease (ie, multilevel disc desiccation observed on MRI) or even low-grade (typically <25%) slips, and they typically have pain out of proportion to physical or radiographic findings. Back pain in general is a major public health problem and remains a primary cause of disability in this country. Its causes are numerous and no simple diagnostic method exists to exclude structural causes. It is important for any physician who cares for patients with spinal problems to address behavioral and psychosocial factors that may contribute to a patient's disability. Surgical therapyThe goal of surgery 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 disc through arthrodesis (fusion). Fusion Multiple methods exist to achieve intersegmental fusion in the lumbosacral spine. The authors concentrate on the following most widely used methods:
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). 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 reducing the incidence of nonunion and spondylolisthesis progression. The quoted rate of transient or permanent nerve root injury associated with reduction is 5-30%. Preoperative detailsThe surgeon should plan the approach (anterior vs posterior), 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, CT scanning 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, and perioperative and postoperative use of anti-inflammatory medication is not recommended, as they can inhibit fusion. Intraoperative detailsThrough the 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 be observed 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. Decompressive laminectomies and facetectomies are typically initiated with rongeurs (ie, 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. Due to the incompetent pars in type IIa slips, this can be performed with relative ease using large rongeurs. Frequently, the entire loose posterior arch does not need removal, 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 root 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 disc 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 approach; 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. 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 4 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 tightening the entire fixation. 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 are being obtained and demonstrate some promise. The wound is then closed in multiple layers with watertight closure of the lumbodorsal fascia over one or two drains. Postoperative detailsRoutine postoperative laboratory tests should include a hematocrit level assessment. A plain anteroposterior and lateral radiograph of the operated segment(s) is 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 (ie, steroids, Toradol) are to be avoided since 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. Follow-upAfter 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. For excellent patient education resources, visit eMedicine's Back, Ribs, Neck, and Head Center. Also, see eMedicine's patient education article, Back Pain. COMPLICATIONSSection 8 of 12
Specific complications for lumbar fusion from a posterolateral approach include the following:
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. OUTCOME AND PROGNOSISSection 9 of 12
Lumbar fusion is being performed with more frequency across the United States, with considerable regional variation. These variations have been attributed to a multitude of factors, from advancements in instrumentation to the understanding of bone healing. Lack of clearly defined indications for fusion has been another contributing factor. The evidence in support of fusion for spondylolistheses types I, II, IV, and V and iatrogenic spondylolisthesis is strong. Some controversy exists regarding persons with degenerative-type slips (type III), degenerative scoliosis, and mechanical back pain. Very few prospective randomized trials are assessing the long-term outcome of lumbar fusion in these patients. Variables used to evaluate the effectiveness of this procedure have included patient level of function, pain, satisfaction, return to work, and quality of life. Radiographic confirmation of fusion, complications, and cost are other important criteria in the evaluation of the overall outcome. In 1993, Zdeblick et al performed a prospective randomized study, which confirmed that the addition of rigid posterior instrumentation increases the rate of fusion and correlates with less pain and a greater rate of returning to work. In contrast, Franklin et al in 1994 retrospectively evaluated the outcome of lumbar fusion in patients receiving Workers' Compensation in Washington state. They found 68% of patients experienced worsening of back and leg pain, and 56% reported their quality of life had not improved or was worse. They concluded that the use of instrumentation doubled the risk of a second surgical procedure. Ironically, 62% reported they would undergo the surgery again. The influence of psychosocial factors must be considered in any outcome study, and this retrospective study demonstrates that indeed it is difficult to ascertain whether a poor result is due to inappropriate patient selection process, surgical procedure, or failure of outcome measurement. Prospective studies with clearly defined diagnostic categories would probably produce the greatest improvement to the outcome of lumbar fusions. In a prospective study of degenerative slips, Herkowitz showed that an attempted fusion gave better clinical outcomes than decompression alone. The results on isthmic-type spondylolisthesis have been the most promising. Most investigators report a 75-95% rate of good-to-excellent outcome. Most patients undergoing surgery report an improvement in the quality of life and level of pain. Surprisingly, the outcome in most studies does not correlate with the degree of spondylolisthesis or the slip angle. Some long-term follow-up studies support conservative treatment of asymptomatic children and teenagers with spondylolisthesis (type I, type II), regardless of the grade; however, most investigators advocate fusion when the slip is symptomatic, unresponsive to conservative measures, or when it is high grade. FUTURE AND CONTROVERSIESSection 10 of 12
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 that would benefit most from lumbar fusion or particular methods of fusion and fixation. The production of bone morphogenic protein is only one of the promising ventures that undoubtedly will affect the outcome of lumbar fusion. Advances in technology allowing for better instrumentation are here, and more are anticipated. Artificial discs and lordotic tapered cage devices are 2 of these advances undergoing investigations; 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, although long-term studies are not yet available. Osteoinductive pastes and other semisolid mixtures have been introduced to the market; they also promise to enhance the success of this operation. Although the technology continues to improve how surgery is performed, the most challenging task is simply optimal patient selection. As the authors stated earlier, clear indications for fusion must be present in order to optimize outcome, and controversies still exist especially in the treatment of degenerative spondylolisthesis, which 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. MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
Spondylolisthesis, Spondylolysis, and Spondylosis excerpt Article Last Updated: Feb 1, 2008 | |||||||||||||||||||||||||||||||||||
