AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Future And Controversies
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Future And Controversies
• References

The intervertebral disk is a complex structure that has been the focus of much attention in clinical practice. The prevalence of low back and neck pain, which are thought to be associated with degenerative changes in the disk, represent major epidemiological problems. In the United States, back pain is the second leading symptom that prompts visits to physicians. As many as 80% of adults in the United States experience at least one episode of low back pain during their lifetime, and 5% experience chronic problems.

Age-related changes and degeneration

Of all connective tissues, the intervertebral disk undergoes the most serious age-related changes. By the third decade of life, the nucleus pulposus becomes replaced with fibrocartilage, and the distinction between the nucleus and the annulus becomes blurred. The proteoglycan, water, and noncollagenous protein concentrations decrease, while the collagen concentration increases. The increase in collagen concentration is more pronounced in the nucleus and in the posterior quadrants of the disk. It is more pronounced with age and as one proceeds more caudally in the lumbar spine, in a process similar to the Wolff law.

Biochemically, aging increases the ratio of keratin sulfate to chondroitin sulfate, and it also changes the proportion of chondroitin-4-sulfate to chondroitin-6-sulfate, with a parallel decrease in water content. Proteoglycan synthesis decreases, which decreases the osmotic swelling and the traffic of oxygen and nutrients to the disk. Because of this decreased traffic, breakdown products of link and noncollagenous proteins stagnate in the disk. Nonenzymatic glycosylation of these breakdown products accounts for the brown discoloration of the aging connective tissues.

Differentiating aging from degeneration is difficult. According to Pearce et al, "Aging and degeneration may represent successive stages within a single process that occurs in all individuals but at markedly different rates."¹ Aging and degeneration have in common decreased water and proteoglycan content in the disks, combined with increased collagen.

Cascade of degenerative changes

This cascade of degenerative changes can be subdivided into 3 stages: dysfunction, instability, and restabilization. The duration of the stages varies greatly, and distinguishing the signs and symptoms from one stage to the next is difficult.

Dysfunction involves outer annular tears and separation of the endplate, cartilage destruction, and facet synovial reaction. The symptoms of dysfunction are low back pain or neck pain, often localized but sometimes referred, and painful movement. The signs are local tenderness, contracted muscles, hypomobility, and painful extension of the back, neck, or both. Results of a neurological examination are usually normal.

The dysfunction stage is followed by the instability stage, in which disk resorption and loss of disk space height occur. Facet capsular laxity may develop, leading to subluxation. The symptoms are those of dysfunction (ie, "giving way" of the back, a "catch" in the back with movement, and pain with standing after flexion). The signs are abnormal movement (ie, during inspection or palpation), including observation of a catch, sway, or shift when standing erect after flexion.

In the stage of restabilization, the progressive degenerative changes lead to osteophyte formation and stenosis. The symptoms are low back pain of decreasing severity. The signs are muscle tenderness, stiffness, reduced movement, and scoliosis.

Related eMedicine topics:
Lumbar (Intervertebral) Disk Disorders
Diskitis
Lumbar Degenerative Disk Disease

Related Medscape topics:
Specialty Site Orthopaedics
Resource Center Spinal Disorders
Resource Center Back Pain

INDICATIONS

Section 3 of 10  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Future And Controversies
• References

Lumbar surgery is indicated in patients with severe spinal stenosis, in those with intractable pain, and in patients in whom an appropriate 6- to 12-month nonoperative course of treatment fails. Surgery is elective, except in the presence of bowel and bladder symptoms or cauda equina syndrome.

In elective cases, other conservative modalities should have been tried and observed to fail. The patient should be prepared for the operation from a psychological viewpoint. Instability is present at 1 or 2 levels (as mentioned above in the instability phase of degenerative changes).

In the case of cervical disk disease with radiculopathy, the indications for surgical treatment are intractable pain, progressive motor or sensory deficit, or symptoms refractory in a reasonable period of nonoperative therapy. When the symptoms and signs correlate with radiographic evidence of root compression, various groups report a greater than 90% likelihood of a favorable outcome with both anterior and posterior approaches to surgery.

In the case of cervical disk disease with myelopathy, because the natural history is a stepwise worsening course, early surgery to decompress the spinal cord is recommended to arrest progression if the clinical and radiographic changes are well correlated. The best results for myelopathy occur when surgery was performed within 6 months of the onset of symptoms. Some series show improvement of greater than 70% with surgery in patients with myelopathy.

RELEVANT ANATOMY

Section 4 of 10  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Future And Controversies
• References

Cervical, lumbar, and thoracic vertebrae anatomy

The spine is composed of 7 cervical, 12 thoracic, 5 lumbar, and a fused set of sacral and vestigial coccygeal vertebrae. Spine stability is the result of 3 columns in 1 as described by Dennis. Fracture or loss of 2 columns results in instability. The anterior column consists of the anterior longitudinal ligament and the anterior portion of the vertebral body. The middle column consists of the posterior wall of the vertebral body and the posterior longitudinal ligament. The posterior column is formed by the posterior bony arch; this consists of transverse processes, facets, laminae, and spinous processes.

Intervertebral disks form one quarter of the total length of the spinal column. Each vertebra has the potential for 6° of freedom, translation in all 3 axes of movement, and rotation around each axis. Not all vertebrae are created equal; the cervical vertebrae have the greatest freedom of flexion, extension, lateral rotation, and lateral flexion. This is because they are larger, they have concave lower and convex upper vertebral body surfaces, and they have transversely aligned facet joints.

Thoracic vertebrae have restricted flexion, extension, and rotation but freer lateral flexion because they are attached to the rib cage, are smaller, have flatter vertebral surfaces, have frontally aligned facet joints, and have larger overlapped spinous processes. The lumbar spine has good flexion and extension and free lateral flexion because its disks are large, the spinous processes are posteriorly directed, and the facet joints are sagittally directed. Lateral lumbar rotation is limited because of facet alignment.

CONTRAINDICATIONS

Section 5 of 10  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Future And Controversies
• References

Relative contraindications to spine fusion include smoking, morbid obesity, active infection, and severe medical or psychological problems.

WORKUP

Section 6 of 10  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Future And Controversies
• References

Lab Studies

• Seronegative spondyloarthropathies (SNSAs) are a common cause of back pain and should be excluded.
• Order HLA-B27 (class 1 histocompatibility HLA) testing to assess for ankylosing spondylitis (AS), reactive arthritis (formerly called Reiter syndrome), psoriatic arthritis, and inflammatory bowel–associated arthritis. AS is an inflammatory disease of unknown etiology that affects an estimated 350,000 persons in the United States and 600,000 in Europe, primarily white males in the second through fourth decades of life. Worldwide, the prevalence is 0.9%. Genetic linkage to HLA-B27 has been established. In the United States, 0.1-0.2% of whites are estimated to have AS. HLA-B27 is extremely rare in African Americans.
• Serum immunoglobulin A levels are elevated in some patients.
• Inflammatory causes of low back pain can be ruled out with testing for acute phase reactants, such as the erythrocyte sedimentation rate, C- reactive protein level, CBC count, and platelet count.
• Rheumatoid factor testing and antinuclear antibody testing are good screening tools for autoimmune disorders.
• In rare cases, gout and the presence of calcium pyrophosphate dehydrate may need to be excluded by checking serum uric acid levels and performing synovial fluid analysis to check for crystals.

Imaging Studies

• Magnetic resonance imaging
• • Raymond Damadian, MD, discovered the basis for MRI and published a milestone paper in 1971 in the journal Science. He showed that relaxation times between normal and abnormal tissues of the same type are markedly different, as are relaxation times between different types of normal tissues.
  • The FONAR company was incorporated in 1978 and produced the first open MRI in 1982. In 1996, FONAR introduced the Stand-Up MRI, the whole-body MRI scanner with the ability to perform Position Imaging. Patients can be scanned standing, sitting, bending, or laying down. With its unique ability to scan patients in weightbearing postures, the FONAR Stand-Up MRI has identified pathologies that had previously remained undetected on conventional recumbency MRI scanners. Lumbar degenerative disk disease with disk herniations that would be missed in a recumbent position can be visualized on stand-up images. Because of its unique geometric design, the FONAR Stand-Up MRI is spacious and nonclaustrophobic. Nothing is in front of patients' faces or over their heads to create a closed-in feeling. Patients typically sit comfortably watching a 42-inch television throughout the scanning procedure.
  • MRI can be used to differentiate between the nucleus and the annulus, and hence, it allows delineation of contained and noncontained disk herniations.
  • MRI can show annular tears and the posterior longitudinal ligament. Therefore, it can be used to classify the herniation from simple annular bulging to extruded and free-fragment disk herniations.
  • The vertebral bodies adjacent to degenerating disks undergo changes, which Modic described as type 1 and type 2 changes. Some hypothesize that trauma to the intervertebral disks releases chemical substances that increase the diffusion resistance through an autoimmune mechanism. As the diffusion coefficient increases, the endplate undergoes sclerosis and the adjacent bone marrow exhibits an inflammatory response (ie, as it is infiltrated by fibrovascular tissue). These Modic type 1 changes lead to diminished intensity on T1-weighted images and increased intensity on T2-weighted images. The inflammatory response destroys the marrow of the adjacent vertebral endplates, which is replaced by fat. These Modic type 2 changes lead to increased signal intensity on T1-weighted images and the same or increased intensity on T2-weighted images.
• CT scanning
• • In the absence of MRI, CT scanning is accurate in diagnosing disk herniations because the disk herniated material, the perineural fat, and the adjacent posterolateral margins of the bony vertebrae can be contrasted. However, MRI remains the image modality of choice for diagnosing lateral herniations.
  • CT scanning offers several advantages over MRI. Among them, the cost of CT scanning is lower, it is less stressful for claustrophobic patients, and it is better for detection of subtle bony changes (eg, spondylolysis and early degenerative changes of the facet joints). CT scanning is also better for assessing bony fusion integrity after fusion.
  • Gundry and Heithoff established criteria for the CT diagnosis of disk herniation with associated neural impingement.² First, the disk protrusion must be focal and asymmetric, often dorsolateral in position, directly underlying the nerve root traversing that disk. Second, nerve root compression and/or displacement should be demonstrable. Third, postimpingement swelling of the affected nerve root is often present caudal to the herniation. This results in enlargement of the nerve and blurring of its margin because of edema, inflammatory exudates, or prominence of the adjacent epidural veins.
• Lumbar diskography
• • Diskography is controversial. Some spine specialists who do not believe diskogenic pain is clinically significant problem believe it has no value. The value of diskography for determining the source of pain or for determining whether surgery is necessary is not scientifically proven. Some other physicians use diskography in several clinical situations, including (1) to evaluate equivocal abnormalities seen on myelographs, CT scans, or MRIs; (2) to try to select a symptomatic disk among multilevel abnormalities; (3) to diagnose a lateral disk herniation; (4) to subjectively support the existence of diskogenic pain; (5) to select fusion levels; and (6) to evaluate the spine after surgery. These uses are not scientifically established.
  • Diskography is a procedure that aims to subjectively evaluate whether a disk is painful under certain conditions. The diskogram is less about the anatomy of the disk and more about its pathophysiology. A disk that looks abnormal on an MRI may not be painful, and a minimally disrupted disk on an MRI may be associated with severe pain on a diskogram.
  • Abnormal disks accept more than 1.5 mL of normal saline or contrast material, with a spongy endpoint during injection. In abnormal disks, contrast medium extends beyond the nucleus pulposus through annular tears or through a radial fissure. Because the outer annulus is richly innervated by the recurrent meningeal nerve, the anterior primary ramus, the mixed spinal nerve, and the gray ramus communicans, the pressure of contrast provokes pain.
  • When the pressure of the contrast material reaches the part of the disk in contact with the nerve root, radicular pain may be provoked.
  • The potential complications or adverse effects from diskography include exacerbation of pain, contrast agent allergy, nerve root injury, and chemical or bacterial diskitis.
• Diskography is a controversial procedure. Its validity has been questioned on the grounds of technical errors and on the presence of false-positive results. Opponents of the procedure believe the false-positive results are the result of psychosocial factors and/or neurophysiological phenomena, such as central hyperalgesia in patients with chronic pain. The existence of clinically significant diskogenic pain is also questioned.
• Proponents of diskography believe it is the only method to diagnose diskogenic pain. They advocate strict selection criteria for patients and strict criteria for a positive result from diskograms.
• CT diskography
  • This procedure should be performed within 4 hours of an initial diskography.
  • Clinical applications include (1) determining if the disk herniation is contained, protruded, extruded, or sequestrated and (2) distinguishing between mass effects from scar tissue or disk material in the spine after spinal surgery.
• Combination of imaging modalities
  • A combination of imaging modalities may be necessary to adequately evaluate cervical stenosis and nerve root compression.
  • Plain cervical radiographs provide important information regarding alignment, degenerative bony changes, and deformities. Dynamic flexion/extension images are important to determine sagittal balance and the presence of osseous instability.
  • MRI has become the study of choice in the initial evaluation of patients with neck pain after plain radiography. MRI provides images in multiple planes, is noninvasive, and is excellent for studying intrinsic cord disease.
  • Myelography with postmyelography CT scanning is excellent for evaluating nerve root compression. With reconstructions, it also provides excellent details of the bony anatomy in multiple planes.

Diagnostic Procedures

• Selective nerve root blocks
• • Transforaminal selective nerve root blocks (SNRBs) have been used as both subjective diagnostic and therapeutic interventions for lumbar spinal stenotic levels. When MRIs show evidence of multilevel degenerative disk disease, SNRB can be used as a tool to try to determine if a specific nerve root is affected. The procedure involves injection of anesthetic and contrast at the nerve root level of choice under fluoroscopic guidance. This creates an area of hypoesthesia in the respective dermatome.
  • Anderberg et al investigated the correlation of SNRBs with MRI findings and clinical symptoms in cervical spines with multilevel degenerative disk disease. The results showed a 60% correlation with the most severe areas of MRI degeneration. In areas of neurological deficit, dermatomal radicular pain showed a 28% correlation with SNRB results.³
  • SNRB can sometimes be a helpful tool together with clinical findings/history and MRI of the cervical spine for preoperative investigations in patients with multilevel degenerative disk disease who present with radicular pain.

TREATMENT

Section 7 of 10  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Future And Controversies
• References

Medical therapy

Conservative treatment includes back education and back school, exercise, medications, physical modalities, and injections.

Back education and back school

The goal is to teach patients how to help themselves manage their back pain. First, knowledge of normal spine anatomy and biomechanics, together with the mechanisms of injury, is taught. Then, the diagnosis is explained to the patient, making use of spine models. The neutral or balanced position, which differs from patient to patient, is sought.

Back school teaches the patient basic body mechanics, such as the correct posture for standing, standing at a desk or drawing board, sitting, brushing teeth, washing the face, pushing and pulling a weight, lifting a weight, getting in and out of bed, sleeping, getting into a car, and sitting in a car. Back school also teaches patients the proper and improper behaviors when their back is painful in case they have to sit, bend forward, lie down, cough, or sneeze.

Exercise

Different types of exercises are prescribed, depending on each patient's diagnosis. Floor exercises consist of abdominal bracing, modified sit-ups, double-knee-to-chest or low back stretches, seat lifts, mountain and sag exercises, knee-to-elbow exercises, hamstring stretches, extension exercises, and extension flexibility exercises. Swimming exercises are some of the best activities for back pain. Aerobic exercises improve endurance if performed regularly (ie, >3 times/wk). Relaxation exercises are good for relieving muscular tension that may aggravate back pain.

Medications

These include muscle relaxants, nonsteroidal anti-inflammatory drugs, and analgesics.

Physical modalities

These include the use of ice packs, heating pads, electrical stimulation, phonophoresis, iontophoresis, relaxation, and biofeedback.

Injections

Epidural steroid injections are most commonly used for therapeutic purposes. The type and dosage of steroid varies widely. Methylprednisolone (80-120 mg) mixed with normal saline to achieve a volume of 8-10 mL is an effective and safe volume and dosage. In some centers, 2-3 injections are given over a 1- to 2-week course, but the long-term results do not appear to be any different from those achieved with a single injection.

The response to epidural injections is variable, and many authorities believe the injections are only of short-term value. Even if a favorable response occurs, no more than 4 injections should be given annually. Immediate pain relief may be achieved by adding 4-6 mg of preservative-free morphine to the epidural steroid injection. Pruritus is a reliable sign of epidural placement.

Patients should be observed for 24 hours for respiratory depression or urinary retention following morphine epidural steroid injections, even though these are uncommon adverse effects. If morphine is to be avoided, lidocaine or bupivacaine can be used in combination with the steroid to achieve immediate pain control, albeit of short duration.

Surgical therapy

Surgical treatment is used in approximately 5% of the patients and includes lumbar surgeries and cervical surgeries.

Lumbar surgeries

The most common lumbar surgical procedures for degenerative disk disease fall in 2 categories. For the first, decompression involves removal of bone or disk material from around a compressed nerve root to relieve pinching of the nerves and provide more room for the nerves to recover. This is performed through laminectomy and diskectomy. For the second, lumbar spinal fusion involves using a bone graft to fuse one or more vertebrae and stop the motion at a painful vertebral segment. This, in turn, should stop or decrease the pain generated from the joint.

Lumbar diskectomy

During surgery, the affected level is identified through a posterior midline approach. The incision in the ligamentum flavum is started in the midline, where it is tented away from the dura. The ligamentum flavum is excised in one piece to expose the interlaminar space on one side. The opening is widened by excising portions of lamina. Difficulty in retracting the root suggests that it is compressed by a disk herniation or entrapped in a narrowed lateral recess.

Once the nerve root is identified, it is retracted and a cruciate incision is made in the bulging annulus. The loose fragments of the disk are extracted with pituitary rongeurs. The nerve root should be freely mobile and easily retracted, otherwise it may still be compressed or lateral stenosis may be present. In the latter case, the lateral recess and the neural foramen should be enlarged (see below, Lumbar laminectomy for one-level central and lateral stenosis). A free fat graft is placed over the exposed dura to prevent adhesions.

After surgery, a neurological examination is performed in the recovery room, and the findings serve as a baseline. A urine catheter is used if difficulties with micturition arise. Postoperatively, the patient may stand and walk for increasing periods. The patient can usually go home 1-5 days after surgery. Some surgeons also perform the lumbar diskectomy as an outpatient procedure.

Low back exercises (pelvic tilting and half sit-ups) are started at this point. Follow-up initially occurs at 2- to 6-week intervals. Light work is started at 2-8 weeks and heavy work at 12-16 weeks.

Lumbar laminotomy for one-level central and lateral stenosis

The surgical operation involves an approach to the stenotic level through a one-level bilateral minimal partial laminotomy. A gauge is inserted into the lateral canal to determine its size. The medial third of the inferior articular process is removed with an osteotome or rongeur. The medial and anterior parts of the superior articular process are removed with a power tool, a Kerrison rongeur, or an osteotome and mallet. For lateral stenosis, removal of more of the superior articular process until the lateral canal diameter is 6 mm is usually necessary. At the end of the procedure, a free fat graft is placed between the dura and the posterior muscles to prevent adhesions.

Lumbar laminectomy for central and lateral stenosis at several levels

If conservative measures fail, the operation is essentially the same as for one-level stenosis. The dura is often exposed just above or just below the lesion through a normal interlaminar space. The aperture is then widened as described above, and the medial portions of inferior and superior facets are removed. The exposure is then lengthened longitudinally with a Kerrison rongeur, taking care to not injure the dura. The laminectomy should be as short as possible. However, a long laminectomy does not make the spine unstable, provided the lateral two thirds of all the facet joints are preserved.

Postoperative care is the same as after diskectomy, but these patients usually experience less postoperative discomfort.

Approximately 70-80% of patients who undergo laminectomies have significant improvement in their function and markedly reduced levels of pain and discomfort. The laminectomy surgical results are much better for relief of leg pain caused by spinal stenosis than for relief of lower back pain.

The risks and complications of laminectomies are (1) nerve root damage (1 case in 1,000); (2) bowel/bladder incontinence (1 case in 10,000); (3) cerebrospinal fluid leakage (1-3%); (4) infections (1%); (5) postoperative instability at the operated level (5-10%); and (6) general anesthetic complications such as myocardial infarction, blood clots, stroke, pneumonia, or pulmonary embolism.

Lumbar spinal posterolateral gutter fusion

This type of spinal fusion involves placing bone graft material in the posterolateral portion of the spine (a region just adjacent to the spine).

During surgery, a bone graft is harvested from the posterior iliac crest. The posterior articular and transverse processes are completely denuded of periosteum with an elevator. The additional stripping provides more bare bone and stimulates more new bone formation. A sharp, curved gouge is used to raise "shingles" of corticocancellous bone on the posterior surface of the transverse process.

Alternatively, a high-speed burr can be used to achieve decortication. The same technique is used for shingling and denuding the upper and posterior surface of the sacrum, for obtaining a free cancellous bone graft. The graft is then placed over and between the denuded surfaces. The large back muscles that attach to the transverse processes are elevated in order to create a bed on which to lay the bone graft. The back muscles are then laid back over the bone graft, and the created tension holds the bone graft in place. Finally, a free fat graft is placed and sutured over the exposed dura to prevent encroachment on to the bone graft.

Postoperative care is for approximately 5-10 days. A back brace is usually applied.

The 2 key factors under a patient's control that determine whether a fusion solidifies are (1) smoking cessation and (2) limited motion.

The risks of this type of surgery are nonunion, infection, bleeding, and solid union with no reduction of back pain. The nonunion rates are 10-40%. Risks of nonunion are prior surgery, smoking, obesity, multilevel fusion surgery, and previous radiation therapy for cancer. Infection and bleeding have an occurrence rate of 1-3%.

Posterior lumbar interbody fusion

The advantage of posterior lumbar interbody fusion (PLIF) over the anterior interbody fusion is that either decompression or diskectomy can be performed through the same approach. Unlike the posterolateral gutter fusion, the PLIF achieves spinal fusion by inserting a bone graft directly into the disk space. An oversized bone graft is harvested from the posterior iliac crest through a transverse incision. The ligamentum flavum is completely excised.

When the operation is for disk disease, the interlaminar space is widened by removal of the superior and inferior margins of the adjacent laminae, partial medial facetectomy, and retraction with a laminar spreader. A rectangle of annulus is excised. The bony ledge of the superior margin of the lower vertebral body is removed, clearing the way to the diseased disk. The endplates and disk material are then removed. Blocks of corticocancellous bone taken from the iliac crest are cut to the measured size of the disk space and jammed into place. The same maneuver is repeated on the opposite side. Finally, a free fat graft is sutured to the nearby soft tissues to cover the dura.

Postoperatively, braces are optional.

The PLIF has several disadvantages. First, not as much of the disk space can be removed with a posterior approach. Second, an anterior approach provides for a much more comprehensive evacuation of the disk space and, hence, increased surface area available for fusion. Third, a much larger bone graft can be inserted from an anterior approach. Fourth, in cases of spinal deformity (eg, isthmic spondylolisthesis), a posterior approach alone is more difficult to reduce the deformity. Finally, although the risk is small, insertion of a bone graft posteriorly may allow it to retropulse back into the canal and create neural compression.

The major risk for this type of surgery is nonunion. The rates of nonunion are 5-10%, lower than that for posterolateral gutter fusion.

Anterior lumbar interbody fusion

Anterior lumbar interbody fusion (ALIF) is similar to PLIF, except that in ALIF the disk space is fused by approaching the spine through the abdomen instead of through the back.

During surgery, an anterior retroperitoneal or transperitoneal approach is made, and the main vessels are retracted to the side. A flap of the anterior longitudinal ligament and anterior annulus fibrosus is raised with a scalpel. The disk material is removed piecemeal with curettes and pituitary rongeurs as far as the posterior longitudinal ligament. When the disk is completely cleared posteriorly and laterally, the endplates are excised to bleeding cancellous bone with osteotomes. When bleeding is controlled, iliac crest grafts are punched into the space. The flap of anterior ligament and annulus are replaced and sutured.

Postoperatively, oral intake is delayed until bowel sounds return or flatus is passed. The care is similar to that for other fusions.

The ALIF approach has the advantage that unlike the PLIF or the posterolateral gutter approaches, both the back muscles and nerves remain undisturbed. Another advantage is that placing the graft in the front of the spine puts it in compression, and bone in compression tends to fuse better, according to the Wolff law. However, because of the reliance on compression for achieving solid fusion, osteoporosis is a contraindication for ALIF.

Major risks of ALIF are blood loss from damage to the major blood vessels (eg, aorta, vena cava), with quoted rates of 1-15% and, in men, retrograde ejaculation. The other risks are nonunion (5-10%), infection, and bleeding (1-3%).

Transforaminal lumbar interbody fusion

Transforaminal lumbar interbody fusion (TLIF) has become an increasingly popular treatment for lumbar degenerative disk disease, spondylolisthesis, degenerative adult scoliosis, spinal stenosis, and recurrent disk herniation.

TLIF was developed by Harms; the approach to the spine is posterior, with access to the disk via a path through the far lateral portion of the vertebral foramen. This allows complete removal of the disk and placement of an interbody support transforaminally with reduced risk of nerve injury while permitting posterior decompression and interbody fusion.

TLIF is a modification of PLIF that has been used since the 1940s for degenerative disk disease. It offers good exposure with decreased risk, especially in repeat cases of spine surgery in which the presence of scar tissue makes PLIF very difficult. PLIF permits good posterior decompression; however, the disk is not removed and the segment is not efficiently immobilized. TLIF is also a viable alternative to anteroposterior circumferential and anterior lumbar interbody fusion. The approach is either unilateral or bilateral laminectomy with an inferior facetectomy, diskectomy, arthrodesis, pedicle screw fixation, and insertion of titanium or carbon fiber cages with autologous bone. The fusion can be single level or multilevel. The goal is anterior column support and fusion.

The results in a number of published series have shown excellent outcomes with few complications. Complications include cerebrospinal fluid leaks, transient neurological complications, and minor wound infections. In some series, radiographic fusion was demonstrated in 74-93% of patients, with no deaths or major hardware failure. Of these patients, 90% said they would have the procedure again. TLIF has become a safe technique for interbody support with good clinical outcome.

Preoperative care and postoperative care are the same as for PLIF.

Spine fusion instrumentation

Bone tends to fuse better in an environment with as little motion as possible. The role of spine fusion instrumentation is to decrease motion at the segment undergoing fusion and to provide additional spinal stability.

The 3 major types of spine surgery instrumentation are pedicle screws, anterior interbody cages, and posterior lumbar cages. Pedicle screws provide a means of gripping onto a vertebral segment and limiting its motion. Anterior interbody cages are devices inserted into the lumbar disk space through an anterior approach. They can be made of allograft bone, titanium, or carbon/polyetheretherketone (PEEK) (radiolucent cages). Posterior lumbar cages are also made to be inserted into the lumbar disk space, but they are modified to be inserted through a posterior approach. They can be made from the same materials as the anterior cages.

Total disk arthroplasty

This procedure has been used for lumbar diskogenic pain, with and without radicular symptoms. The ProDisc prosthesis has been used for both single and multilevel degenerative disease. Bertagnoli et al, in a 2-year study of patients older than 60 years, showed a 94% satisfaction rate with the ProDisc therapy. Patients also showed a decrease in radicular pain. Patients with decreased bone mineral density underwent a vertebroplasty before insertion of the ProDisc.^{4, 5} However, the accuracy of certain studies on ProDisc are currently being challenged.⁶

Tropiano et al showed that the sex of the patient and whether surgery was multilevel did not affect the outcome, but prior lumbar surgery or age younger than 45 years was associated with slightly worse outcomes.⁷

Complications were very few and included a unilateral foot drop, implant subsidence, and loss of vibration and proprioception. These complications were mainly seen in patients with circumferential spinal stenosis.

Artificial disk replacement has shown results similar to fusion in the short term, but long-term results are not known.

Smoking versus not smoking and the risk of pseudoarthrosis (surgical nonunion) after fusion procedures

Smoking is well known to impede bone and wound healing. Brown et al investigated the rate of pseudoarthrosis in persons who smoke and in persons who do not smoke who had undergone a 2-level laminectomy and fusion of the lumbar spine over a 1-year period. Of 100 patients, 40% of those who smoked and 8% of those who did not smoke developed a pseudoarthrosis. The results clearly show that smoking causes a significant increased risk for pseudoarthrosis in spine fusions and is a major contraindication for surgery.

Cervical surgeries

The goal of surgery for cervical radiculopathy is to adequately decompress the nerve roots. The options available are (1) anterior cervical diskectomy (ACD), (2) ACD and fusion (ACDF), (3) ACDF with internal fixation (plating), and (4) posterior foraminotomy. The choice of the appropriate procedure depends on a number of factors, including the location of the neural compression, the presence of deformity or instability, and potential morbidity. In general, anterior pathology, such as a centrally herniated disk and anterior osteophytes, is treated anteriorly, and posterior pathology, such as posterolateral osteophytes/disk herniations, may be treated with a posterior approach.

The goal of surgery for degenerative cervical disk disease with myelopathy is to adequately decompress the spinal cord. Literature regarding spondylotic myelopathy does not clearly demonstrate the superiority of either the anterior approach or the posterior approach. Options for surgery include (1) single- or multiple-level ACDFs, (2) single- or multiple-level anterior corpectomy with fusion, (3) laminectomy with or without fusion, and (4) laminoplasty. The choice of approach is based on the location of the pathology, the risks and benefits of each procedure, and the geometry of the spinal canal.

Anterior cervical diskectomy

ACD involves performing a decompression of the nerve roots through an anterior diskectomy. An area of controversy is whether an interbody fusion is necessary after a single-level ACD. Although initially ACD involved fusion procedures, complications, including graft and donor site complications, prompted some surgeons to perform a simple diskectomy. Diskectomy may be considered for patients with normal cervical lordosis, minimal axial pain, and abnormalities limited to one level. A high frequency of improvement has been reported in the literature with diskectomy alone, although most surgeons now routinely use fusion.

Possible risks and complications of ACD include (1) nerve root damage, (2) damage to the spinal cord (approximately 1 case in 10,000), (3) bleeding, (4) infection, (5) graft dislodgment, (6) damage to the trachea or esophagus, and (7) continued pain. Damage to the recurrent laryngeal nerve during the procedure may cause hoarseness, and retraction of the esophagus sometimes causes temporary difficulty with swallowing.

ACD and fusion

An interbody fusion usually avoids recurrent radiculopathy from foraminal narrowing and the possibility of developing late kyphosis from disk-space collapse. A combination of diskectomy and fusion should be performed in all patients, especially if multiple levels are involved or if instability is documented at any level. The complications involved with not performing a fusion are much higher than the small risk of complications associated with fusion.

For single-level fusion, autologous bone results in a fusion rate of 95%. To prevent donor-site complications, alternatives include the use of allograft bank bone, bovine cancellous bone, and synthetic materials. The main risk of a fusion surgery is that it does not result in fusion. In general, allograft bone does not heal quite as well as autograft bone, but both yield good results when used in the anterior cervical spine.

If a graft is used without instrumentation, the risk of graft dislodgment or extrusion is 1-2%. If this happens, another operation is performed to reinsert the bone graft, and instrumentation (plating) can be used to hold it in place.

ACDF with internal fixation (plating)

Plating can be helpful in patients who require procedures in multiple levels, with documented instability, in persons who smoke, patients with a prior history of nonunion, and those with a previous fusion adjacent to the level to be fused. In addition, with a plate, no brace is needed, allowing an earlier return to work and resumption of daily activities.

Kaiser et al found the overall fusion rate for 522 patients for 1-level ACDF with allograft bone and anterior plate to be 96%. This rate decreased to 91% when performed over 2 levels. The rates for 1- and 2-level fusions without anterior fixation were, respectively, 90% and 72%. The improved fusion rates and low complications associated with anterior cervical plating are good arguments for its use in the treatment of degenerative cervical disk disease.⁸

Posterior cervical foraminotomy

Nerve root decompression may be accomplished posteriorly by performing a foraminotomy. The keyhole approach, developed by Scoville to decompress nerve roots, involves removal of one or more hemilaminae with removal of osteophytes and disk fragments. This is used most commonly in soft posterolateral disk herniations, thus obviating the need for a fusion. High success rates have been reported.

Single- or multiple-level ACDFs

ACDFs at single or multiple levels may be performed for myelopathy when the pathology is limited to the disk spaces and does not involve the vertebral bodies. Although multilevel corpectomy is also an option in these cases, multilevel ACDFs have the advantage of segmental fixation and restoration of lordosis.

Single- or multiple-level cervical corpectomy with fusion

A corpectomy is the removal of a vertebral body and the disk spaces at either end in an effort to completely decompress the cervical canal.

With multiple areas of spondylotic compression of the spinal cord, corpectomy with strut grafting may be performed. With multilevel corpectomy, anterior strut fusion is necessary to prevent kyphotic deformity and restore stability. Anterior plating is recommended for corpectomy and multilevel procedures to reduce the risk of graft extrusion and pseudoarthrosis. As the length of the fusion increases, the rates of both graft- and instrumentation-related complications increase. In such cases, posterior stabilization is recommended to improve stability and fusion rates and reduce graft- and instrumentation-related complications.

A corpectomy is a more technically difficult surgery to perform. The risks are similar to those for diskectomies, but because a corpectomy is a more extensive procedure than a diskectomy, the risks are greater. The most worrisome risk is compromise of the spinal cord leading to quadriplegia. To decrease this risk, spinal cord function can be monitored during surgery using somatosensory evoked potentials.

Another risk is compromising the vertebral artery, which can cause a stroke.

Cervical laminectomy with or without fusion

Laminectomy is sometimes needed if patients have congenital cervical stenosis or if the disease process involves more than 3 levels or multiple discontinuous levels. In patients with kyphosis, anterior fusion may be needed to prevent further progression of the kyphotic deformity. If most of the compression of the spinal cord is posterior, laminectomy can sometimes be used.

As with cervical corpectomy, the main risk with cervical posterior laminectomy is deterioration in neurological function after surgery. Use of intraoperative somatosensory evoked potentials can decrease this risk. Other risks include dural tear, infection, bleeding, increased pain, and instability in the spinal column.

If a laminectomy is performed, a fusion is recommended to prevent kyphotic progression. Other indications for posterior fusion include evidence of instability on preoperative dynamic radiographs, failure of anterior fusion, or decompression involving bilateral facetectomy. Most of the experience with posterior fusion has been with autologous bone from spinous processes or the iliac crest, but allograft bone has been used.

Cervical laminoplasty

The laminoplasty technique was primarily developed by the Japanese for treatment of ossification of the posterior longitudinal ligament. It involves osteoplastic enlargement of the spinal canal by performing the laminectomy on one side to create a "door." The goal of this procedure is to reduce the postlaminectomy instability discussed previously. Although infrequently used, successful treatment of cervical spondylosis has been reported using this technique.

Cervical keyhole foraminotomy

The posterolateral keyhole foraminotomy is indicated for posterolateral disk herniations with radicular pain. It is an efficient way of decompressing a lateral soft disk without the risks of an anterior approach. A bone graft is not needed. Use of an operative microscope helps achieve good outcomes. Burke and Caputy describe a rigid endoscopic approach with a smaller incision, less postoperative pain, and fewer complications.

Chen et al compared spine segment flexibility after the keyhole procedure with an ACDF and anterior foraminotomy with a diskectomy and showed a minor increase in motion with the keyhole foraminotomy.⁹

Silveri et al in a 6-year long-term follow-up study showed excellent results with preoperative pain relief in all the patients and no significant complications. Preoperative and postoperative care is the same as with ACDFs.¹⁰

COMPLICATIONS

Section 8 of 10  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Future And Controversies
• References

The complications of lumbar disk surgery were described above. Other complications include cauda equina syndrome, thrombophlebitis, pulmonary embolism, wound infection, pyogenic spondylitis, postoperative diskitis, dural tears, nerve root injury, cerebrospinal fluid fistula, laceration of the abdominal vessels, and injury to abdominal viscera. Paralysis, stroke, and death, although rare, are possible.

Two types of postfusion stenosis are described. The most common type is above the fusion, secondary to degenerative changes, and the second type is deep to the fusion, secondary to new bone formation. The degenerative stenosis above the fusion is relieved by decompression through a bilateral laminectomy. The stenosis beneath the fusion requires exposure of the dura above the fusion and removal of the central portion of the fusion mass in a caudal direction.

The most commonly seen lesions in the previously operated back are lateral spinal stenosis (58%), central spinal stenosis (7%), arachnoiditis (16%), recurrent disk herniation (12%), and epidural fibrosis (8%). Arachnoiditis, intraspinal fibrosis and epidural adhesions may benefit from epidural steroid injections or from a caudal block. If an operation is again undertaken, the distortion of the anatomy, the scar tissue posterior to the dura, and the adhesions between the dura increase the risk of opening of the dura and damaging nerves or blood vessels.

The possible sources of pain in the previously operated spine are many, and frequently they coexist. Possibilities include persistent or recurring disk herniation, diskogenic pain, instability, pseudoarthrosis, lateral recess stenosis, painful motion segment adjacent to a fused motion segment, posterior joint syndrome, sacroiliac joint syndrome, myofascial syndrome, deconditioning of lumbar paraspinal muscles, arachnoiditis, epidural fibrosis, pain at the bone graft donor site, and psychological magnification and causation of pain.

A number of complications associated with ACD have been reported in the literature. Fortunately, the occurrence of serious complications is rare (3%). Injury to the recurrent laryngeal nerve, especially with right-sided approaches, is the most common complication, although it may be transient. Other structures at risk include the trachea, esophagus, carotid artery, sympathetic chain, and the vertebral artery, if the decompression is carried too far laterally. Spinal cord or nerve root injury is the most serious complication but is relatively rare (0.2%) in the hands of experienced surgeons. The C5 nerve root is sensitive to trauma. Other less frequent complications include infections, cerebrospinal fluid leak, and dural tears.

Graft complications after ACD and fusion include collapse, displacement, and pseudoarthrosis. The rate of graft displacement is reported to be as high as 8%. Graft placement under compression and use of plates may reduce this complication rate. Graft collapse is more frequent in patients with osteoporosis. Allograft is preferable if any question exists regarding the quality of the autologous bone. Pseudoarthrosis rates of 5% for one level and 12-15% for multiple levels have been reported.

Complications reported for ACDF with internal fixation (plating) include hardware failure, screw pullout, or breakage with esophageal perforation. The most serious complications of foraminotomy are nerve root injuries (4%).

Worsening of symptoms with laminectomy for myelopathy occurs in 3-5% of cases. Postlaminectomy instability and kyphosis have been reported in the range of 10-22%. The role of facetectomy in postoperative instability has been documented in the literature through laboratory and clinical data. Facetectomies of more than 50% cause a significant loss of stability in flexion and torsion compared with an intact spine. Progressive postlaminectomy kyphosis may require anterior corpectomy/strut grafting with instrumentation and, possibly, posterior instrumentation.

FUTURE AND CONTROVERSIES

Section 9 of 10  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Future And Controversies
• References

Chemonucleolysis with chymopapain or collagenase

The posterolateral extradural approach with a 2-plane image intensifier avoids penetrating the dura and causing leakage of chymopapain into the subarachnoid space. Because anaphylactic shock is a potential complication, cardiopulmonary monitoring is used. Additionally, an intravenous line is established; hydrocortisone, epinephrine, aminophylline, and diphenhydramine should be available, and an anesthetist should be present with intubation and ventilation equipment.

The use of contrast material is kept to a minimum, and the chymopapain must be refrigerated until the time of use. The dose is 4000 U or 2 mL per disk.

Postoperatively, the patient should be as active as possible. A stiff canvas corset, oral analgesics, and anti-inflammatory drugs are prescribed. Many patients require a few days of in-hospital care.

Because of complications and effectiveness problems, chymopapain injection is rarely performed in current practice.

Automated percutaneous lumbar diskectomy

Onik and associates introduced automated percutaneous lumbar diskectomy (APLD) in 1985. This procedure is safer than chymopapain intradiskal injection. It allows debulking of the central disk material by placement of a needle and the use of an automated suction/cutting device. At this time, no clear evidence suggests that APLD is more effective than noninvasive methods of treating disk herniation.

Arthroscopic microdiskectomy

With arthroscopic microdiskectomy (AMD), the surgeon can visualize the nerve root and annulus with an endoscope. Disk fragments in the posterior disk area can be removed using manual and automated instrumentation. Biportal AMD has been attempted for improved surgical control (similar to joint arthroscopy), but this variant carries more risk of injury of the nerve root on the contralateral side.

APLD and AMD are primarily recommended for contained disk herniations when noninvasive methods have failed, although attempts have been made to address noncontained lateral disk herniations using AMD instead of the usual paralateral surgical approach.

Microendoscopic diskectomy

This diskectomy uses a posterior approach identical to standard lumbar diskectomy or microdiskectomy. A cannula is docked under the lamina under fluoroscopic guidance and laminotomy. Ligament removal and diskectomy are then performed using an endoscope. Migrated disk fragments are accessible with this technique.

Intradiskal electrothermal annuloplasty

Intradiskal electrothermal annuloplasty (IDET) is a minimally invasive outpatient surgical procedure. After the intervertebral disk is accessed under fluoroscopic guidance, an electrothermal catheter (heating wire) is passed into the posterior annulus of the painful lumbar disk.

Candidates for IDET include patients with back pain caused by small herniations, internal disk tears, or mild disk degeneration, limited to 1 or 2 levels. IDET is performed after 6 months of conservative treatment has failed.

Factors predicting successful outcome with IDET are (1) single-level disk disease, (2) good catheter placement at the time of the procedure, and (3) an absence of secondary gain issues (eg, financial gain from pending litigation or workers' compensation).

IDET is a very safe procedure with a very low risk of complications. Disk-space infection and nerve injury occur in less than 1% of the patients.

Artificial disks

The main objective of an artificial disk is to replace a painful disk while maintaining the natural anatomical structure of the spine. The procedure is an alternative to lumbar fusion. The Charite disk has recently been approved for use in the United States and has been used in a number of European countries for many years. Random enrollment for trials of the ProDisc are complete. However, the accuracy of certain studies on ProDisc are currently being challenged.⁶The Maverick and Flexicore lumbar disks are actively enrolling patients with single-level disease.

The current indications for implantation of an artificial disk are quite similar to indications for lumbar spine fusion and include (1) degenerative disk disease (typically at a single level), (2) age of 18-60 years, (3) major symptom of lower back pain rather than leg pain, (4) minimum of 6 months of conservative treatment, and (5) patient is a candidate for spine surgery (eg, lumbar fusion).

The 2 types of artificial disks are (1) a total disk prosthesis, designed to replace a full disk, and (2) a nuclear prosthesis, designed to replace the soft inner core of a disk. The outer shell of the disk is made of metal, and the inner core is made of rubber polyethylene.

In some European countries, artificial disks have been used for approximately 10 years. The product used most commonly is the SB Charite prosthesis. Although no studies have examined the long-term effectiveness of this product, short-term and intermediate results have generally been favorable.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Future And Controversies
• References

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Article Last Updated: May 16, 2008