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Surgery

Disc herniation

Introduction


The prevalence of symptomatic lumbosacral disk herniation is relatively small. It is important to differentiate between the reasonably well-defined entity of sciatica resulting from a herniated intervertebral disk and the less well understood diagnosis of low-back pain. Sciatica is defined as pain radiating down the course of one or more of the roots of the sciatic nerve, extending down the nerve to a point below the knee in one or both legs. Sciatica is merely a symptom, not a specific disease or disorder. The history and physical exam are among the most important tools in differentiating this disease process
Incidence and Epidemiology
A symptomatic herniated disk occurs during the lifetime of approximately 2% of the population. In most cases, sciatica improves spontaneously. When the prevalence of sciatica and the radiculopathy (10% to 25%) is taken into consideration, it is clear that surgical treatment should be entertained for less than 0.5% of the population.
The intervertebral disk ages naturally from nuclear dehydration through a series of inevitable changes. With progressive degeneration, disk material may herniate, causing nerve root compression. Herniation generally occurs between the ages of 30 and 50 years. The exact cause of pain radiating down the leg is controversial. However, it appears that symptomatic lumbar radiculopathy is a result of mechanical contact between the disk and one or more nerve roots or a result of a combination of this contact and yet undetermined biomechanical and vascular factors. Almost 98% of clinically important disk herniations occur at the L5-S1 (most common) or L4-5 levels.

Clinical Features

Symptoms of nerve root encroachment are variable. They depend on the patient's age and medical condition, the degree of root compression, the place on the nerve root or dorsal root ganglion at which the pressure is occurring, and the types of resultant inflammation and/or pathologic changes around and within the nerve root.
The most common neurologic impairments are:
• weakness of ankle and great toe dorsiflexors (L5)
• reduced ankle reflexes (S1)
• sensory deficits in the feet (L5 and S1)
Occasionally, a massive midline disk herniation may compress the entire cauda equina, resulting in bowel or bladder dysfunction, saddle anesthesia and bilateral lower extremity signs.

History and Physical Exam

It is important to obtain a complete history and ascertain whether the patient's chief presenting complaint is low back pain or sciatica. Information about the patient's general health, past medical history, recent febrile illnesses or any recent procedures the patient may have undergone are also important.
Typically, true radiculopathy produces pain radiating below the knee and is associated with numbness or paresthesia following a dermatomal pattern. The pain is often aggravated by coughing, sneezing or a Valsalva maneuver. A careful neurologic exam is essential to identify any subtle motor or sensory deficits.
Nerve root tension signs further suggest the diagnosis. Straight leg raising test is defined as positive if it reproduces the patient's sciatica at less than 60° of leg elevation. Crossed straight leg raising occurs when straight leg raising is performed on the patient's well leg and elicits pain in the leg with sciatica. Crossed straight leg raising is less sensitive, but more specific for lumbar disk herniations, particularly those with a central component. High (L3-L4) disk herniations can be tested with a reverse Lasegue test, which is performed with the patient prone by flexing each knee in turn. This gives rise to pain in the femoral nerve roots which should be aggravated by hip extension. Screening of the hips by testing pain-free range of motion should also be performed.

Diagnosis

Four criteria are often discussed as being necessary in order to diagnose symptomatic lumbosacral disk herniation:
• leg pain that is more prominent than back pain
• a dermatomal pain distribution
• positive nerve tension signs
• imaging studies correlating with neurologic signs
Patients with suspected lumbosacral disk herniation should have motor and sensory exams that elicit objective signs of specific nerve root involvement. If the motor and sensory abnormalities do not conform to the expected nerve root distribution, another diagnosis should be considered. In the absence of any significant or progressive neurological deficits, diagnostic studies should be delayed until four to six weeks following the onset of symptoms. Most patients' pain will resolve spontaneously within this time frame. If symptoms and physical findings persist after conservative therapy, diagnostic studies should be obtained. Historically, myelography has been the radiographic study of choice for the diagnosis of a herniated disk. In recent years, CT and MRI have become the primary imaging modalities for this condition. It is known that approximately 35% of symptomatic individuals have evidence of a disk abnormality by myelogram, CT or MRI, with 20% of those under 60 years of age having imaging evidence of a disk herniation. In asymptomatic individuals over 60 years of age, over 50% will have abnormalities. These tests, however, are not without pitfalls or problems in interpretation.
Radiographic Features
Both CT and MRI are excellent techniques to detect and characterize disk herniations. With desiccation and degeneration of the disk, there will be loss of the high intensity signal in the disk on the T2-weighted images. Displacement of nuclear material into the region of the outer annular fibers will cause a focal contour abnormality of the disk. As long as the disk material is contained by the outer annulus or the posterior longitudinal ligament, it is considered a contained herniation. If it penetrates the outer annular-posterior longitudinal ligament complex, it is call a disk extrusion. If the disk material separates from its disk of origin, it is called a sequestered fragment.

Treatment

The mainstay of treatment remains nonoperative. The majority of patients will improve with limited periods of bed rest (three to five days), NSAIDs, patient education and various exercise regimens. Epidural steroids may be of some benefit. A review of the course of symptomatic lumbar disk herniation reveals that surgery plays mainly a palliative role in its management. Results of long-term comparisons of surgical and nonsurgical treatment groups of patients with herniated disks show no statistically significant differences in outcome. Results appear initially better in the surgical group, but this difference diminishes with time. The major benefit of surgical treatment for a herniated lumbar disk appears to be more rapid relief from sciatic pain than is provided by nonsurgical treatment.

Indications for surgical treatment include:

• impairment of bowel or bladder function
• gross motor weakness
• evidence of increasing impairment of nerve root conduction
• severe sciatic pain persisting or increasing despite 4 to 6 weeks of treatment
• recurrent incapacitating episodes of sciatic pain
The acute massive disk herniation that causes bladder and bowel paralysis appears to be best managed by emergent surgical excision. In the face of progressing motor weakness, it is best to intervene early with surgical excision of the disk herniation. It has been shown that patients with a major neurologic deficit eventually made as much recovery with nonsurgical treatment as they did with surgical treatment. However, many surgeons believe that earlier surgery may accelerate neurologic improvement. Failure of nonsurgical treatment is the most common reason for surgical intervention. Optimal nonsurgical treatment occurs over at least four to six weeks, and not more than three to six months. It results in improvement in the patient's symptoms and signs. When incapacitating symptoms continue for more than four to six weeks, are substantiated by appropriate findings (tension signs with or without neurologic deficit), and are verified by collaborative imaging studies (myelogram, CT, MRI), then surgery may be appropriate, depending on the patient's desires and needs.


Surgical Options


The principal goals of surgical intervention are to relieve neural compression and the consequent radiculopathy, while minimizing complications. The most common currently used approach is a limited laminotomy, with disk fragment excision. This surgery yields similar results whether it is performed using standard techniques, loupe magnification or a surgical microscope. More recently, less invasive percutaneous approaches, in which suction, laser or arthroscopic techniques are used, have been advocated.
Limited excision of a herniated disk for relief of sciatica should provide relief of symptoms in more than 90% of properly selected patients. Results of surgery appear to correlate directly with the degree of disk herniation. More than 90% achieve complete relief of sciatica when a free sequestered disk fragment is found at surgery; approximately 80% when an incomplete herniation is present; and 60% to 70% when there is only a protruding disk.
These results emphasize the importance of appropriate patient selection. The relief of back pain as the predominant symptom is unpredictable and usually is not obtained at surgery. When back pain is not a major component of the patient's symptoms before surgery, it can develop postoperatively. Factors leading to surgical failure as a result of back pain include worker's compensation issues, cigarette smoking and age over 40 years.
The most common complication associated with lumbar disk excision are missed pathology, dural tears, and disk-space infection. Some believe these to be more common with the use of the microscope, but many think these problems are related primarily to the surgeon's level of experience or to underlying medical problems

 

Lumbar laminectomy (open decompression)

Similar to a microdecompression, a lumbar laminectomy (open decompression) is a surgical procedure that is performed to alleviate pain caused by neural impingement. The laminectomy surgery is designed to remove a small portion of the bone over the nerve root and/or disc material from under the nerve root to give the nerve root more space and a better healing environment.


A laminectomy is effective to decrease pain and improve function for patients with lumbar spinal stenosis . Spinal stenosis is a condition that primarily afflicts elderly patients, and is caused by degenerative changes that result in enlargement of the facet joints. The enlarged joints then place pressure on the nerves, and this pressure may be effectively relieved with a lumbar laminectomy.

Laminectomy surgical procedure

The lumbar laminectomy (open decompression) differs from a microdiscectomy in that the incision is longer and there is more muscle stripping.
• First, the back is approached through a two-inch to five-inch long incision in the midline of the back and the left and right back muscles (erector spinae) are dissected off the lamina on both sides and at multiple levels (see Figure 2).
• visualization of the nerve roots.
• The facet joints, which are directly over the nerve roots, may then be undercut (trimmed) to give the nerve roots more room.

Post-operatively, patients are in the hospital for one to three days, and the individual patient's mobilization (return to normal activity) is largely dependent on his/her pre-operative condition and age. Directly following the procedure, patients are encouraged to walk. However, it is recommended that patients avoid excessive bending, lifting or twisting for six weeks in order to avoid pulling on the suture line before it heals.

 

Laminectomy success rate

The success rate of a laminectomy surgery is favorable. Following surgery, approximately 70% to 80% of patients will have significant improvement in their function (ability to perform normal daily activities) and markedly reduced level of pain and discomfort.
The laminectomy surgical results are much better for relief of leg pain caused by spinal stenosis, and not nearly as reliable for relief of lower back pain. Lumbar spinal stenosis is often created by the facet joints becoming arthritic, and much of the back pain is from the arthritis. Although removing the lamina and part of the facet joint can create more room for the nerve roots it does not eliminate the arthritis. Unfortunately, the symptoms may recur after several years as the degenerative process that originally produced the spinal stenosis continues.
In certain instances the success rate of a decompression for spinal stenosis can be enhanced by also fusing a joint. Fusing the joint prevents the spinal stenosis from recurring and can help eliminate pain from an unstable segment. Fusion surgery is especially useful if there is a degenerative spondylolisthesis associated with the stenosis. Generally speaking, if there is multi-level stenosis from a congenitally shallow canal a fusion is not necessary; however, if the stenosis is at one level from an unstable joint (e.g. degenerative spondylolisthesis), then a decompression surgery with a fusion is a more reliable procedure.

Laminectomy risks and complications

The potential risks and complications with a laminectomy procedure include:
• Nerve root damage (1 in 1,000) or bowel/bladder incontinence (1 in 10,000). Paralysis would be extremely unusual since the spinal cord stops at about the T12 or L1 level, and surgery is usually done well below this level.
• 1 to 3% of the time a cerebrospinal fluid leak may be encountered if the dural sac is breached. This does not change the outcome of the surgery, and generally a patient just needs to lie down for about 24 hours to allow the leak to seal.
• Infections happen in about 1% of any elective cases, and although this is a major nuisance and often requires further surgery to clean it up along with IV antibiotics, it generally can be managed and cured effectively.
• Bleeding is an uncommon complication as there are no major blood vessels in the area.
• In approximately 5 to 10% of cases, postoperative instability of the operated level can be encountered. This complication can be minimized by avoiding the pars interarticularis during surgery, as this is an important structure for stability at a level. Weakening or cutting this bony structure can lead to an isthmic spondylolisthesis after surgery. Also, the natural history of a degenerative facet joint may lead it to continue to degenerate on its own and result in a degenerative spondylolisthesis. Either of these conditions can be treated by fusing the affected joint at a later date.

Spinal Fusion

Definition


Fusion literally translates “to join” and in spine surgery this means that 2 vertebrae are joined together to make one. There are many reasons why one would perform a fusion (see below) but in essence the surgeons endeavours to trick the body into thinking that the two bones to be fused are a single bone that has broken and then sets up the right conditions so that in healing the bones heal as one. Just as if you broke your arm, 2 bones with sticky ends would become one. In the arm’s case, a plaster cast is applied to hold things in place until the bones are healed, typically 6 weeks. In the lower back screws, plates, rods, cages and an external brace take the place of the plaster cast, and full fusion occurs after 3 months. The “sticky ends” in the case of the spine are the roughened surfaces of bone. Typically bone graft, usually the marrow, is taken from the hip and placed between the roughened surfaces. When bone healing occurs, new bone comes out of the roughened surfaces and migrates along the transplanted bone to bridge the area to be fused. Ironically, at 3 months all the transplanted bone has been replaced by new bone. Understanding all of the above, it becomes clear that although there are a lot of screws and hardware involved, the operation essentially joins bone to bone and it takes a full 3 months to heal.

Technique


A lumbar fusion is a routine operation. Screws as shown below are placed between the vertebrae that are to be fused. The bone graft is placed around these. These screws are made of titanium and usually stay in for life.

 

ALIF

 

Anterior lumbar interbody fusion, also known as ALIF, is an operation primarily performed for the treatment of low back pain. Often, a lumbar discogram is performed. If the MRI picture showing degeneration of a disk space matches the level of pain produced during the discogram, then surgery will have a good chance of helping the pain.
This operation is mainly attempting to help low back pain, although lower extremity pain is occasionally improved, because the implant into the disk space spreads the vertebral bodies apart, opening the neural foramen through which the nerve roots leave the spinal canal.
This procedure is not a good option if a patient is suffering mainly from lower extremity pain because the nerve roots are not vusialized. A surgery from a posterior approach is a better option. This may be either a posterior lumbar interbody fusion (PLIF) or a pedicle screw fixation.

The initial portion (approach) is usually performed by a vascular surgeon, who exposes the anterior border of the lumbar spine for the neuro or orthopedic surgeon. The pertinent vascular structures in this area are the aorta, vena cava, iliac arteries and iliac veins, as well as the pelvic veins. The ureters are also in the vicinity. Seen here is a typical retractor system, used by the vascular surgeon to expose the anterior aspect of the spine. In the close us view, visible are the iliac arteries, and the anterior body of L5.

Once the front of the spine is exposed, the surgeon finds the midline, by using "C arm" (fluoroscopy), which essentially provides an x ray in real time. The disk interspace is prepared, and then the implant is placed within the disk space. The implant may be a titanium cage (packed with cancellous bone from the iliac crest (hip)), threaded on the outside to prevent backout. It might also be a threaded cadaver bone dowel, taken from the bone bank. On the right, two cages are seen from the front, implanted in a translucent spine model.
Often this operation is a stand alone procedure, and the patient is kept in a lumbar brace for three months postoperatively. On the other hand, it is occasionally necessary, either early or later on, to supplement the ALIF with a posterior lumbar fusion using pedicle screws.


The Alif is often supplemented with a pyramidal plate.

 


 

DISCUSPROTHESE

• When is a disc prosthesis suitable? A disc prosthesis is suitable for patients who are not older than 65, when one lumbar disc is severely degenerated. A prosthesis is also suitable for patients with on-going back problems following an open disc operation. A discography is usually done in advance to determine which disc is causing the pain.


• What does the disc prosthesis procedure involve? The degenerated disc is replaced, and at the same time the normal distance between the two vertebrae is restored. A mobile polyethylene disc is supported on both sides by stainless steel plates. During the procedure, which is performed from the front, the prosthesis is firmly inserted resulting in immediate stability. The prosthesis allows normal motion between the vertebrae. Thus, the adjacent discs are not over-stressed as they are after a fusion operation.

• What post-op care and rehabilitation is required? Two hours after the procedure, the patient can walk to his room. In the majority of cases, there is only minor post-operative pain. Most patients can be discharged three to five days after the operation. The patient is then allowed to sit, walk, drive a car or ride a bike. Six weeks after the procedure there are no more restrictions on physical activities.

• Is this an experimental procedure? This was an experimental procedure, but the Link-Charite disc prosthesis (see picture) has been around for 15 years now. However, only a few spine surgeons have learned the precise technique of this operation. These surgeons experience very few serious complications. In fact, the complication rate in the hands of these very experienced surgeons is less than for a regular fusion operation. In follow-up studies over the last ten years, no signs of wear have been determined and the incidence of loosening is very rare.
• Can complications occur? Very rarely, complications such as vascular problems may occur: However, there is always a vasco-surgeon on standby to control eventual bleeding. The infection rate is very low. Regarding thrombosis, after their post-op check the patient receives anti-coagulative protection for two weeks, and before discharge an ultrasound check is performed to rule out a possible thrombosis.

INCLUSION CRITERIA


* Age between 18 and 60 years
* Diagnosis of Degenerative Disc Disease at the L4/L5 or L5/S1 level
* At least six months of conservative treatment

EXCLUSION CRITERIA


* Previous back surgery (except discectomy, laminotomy or nucleolysis at the same level) or other spinal surgery at any level
* Multiple levels of degeneration
* Osteoporosis, osteopenia or other metabolic bone disease
* Spondylolisthesis, scoliosis or spinal tumor
* History of chronic steroid use
* Pregnancy
* Autoimmune disorder
* Morbid obesity

Examples of disc prosthesis

 

 

 

 

Approach:

The routine approach to lumbar discs is left sided, because the inferior vena cava is an obstacle on the right side. The surgeon stands on the right side of the patient. It is important to have both hips of the patient slightly flexed during the approach in order to have relaxation of the iliac vessels, making it easier for their dissection and retraction. The operative table will be curved in lordosis after the disc exposure.

The skin incision is centred on the umbilicus ;again a fluoroscopic control may be helpful to have a good orientation for dissection. The approach is performed above the linea arcuata and the posterior sheath is an obstacle at the lateral side of the rectus; it has to be divided in order to reach the extraperitoneal fascia. A complete cleavage of the peritoneum from the posterior sheath and from the lateral abdominal wall is performed.

 

 

After this procedure the posterior sheath can be divided and the extraperitoneal cavity can be progressively enlarged with medial retraction of the peritoneum. The psoas muscle is identified as a bulging structure; the dissection on the anterior aspect of the muscle becomes more superficial; dissection should not be carried on deeply between the iliacus and the psoas muscle.

 

 

The common iliac artery is identified along the medial side of the psoas. The approach to the disc is lateral to the vessels and the artery must be gently dissected from the psoas and medially retracted. The common iliac artery is the first element to be identified ; the iliac vein is more deeply situated; it is seen after retraction of the artery and it should also be gently dissected and retracted toward the midline. A complete exposure of the anterior aspect of the disc is possible but that requires an extensive dissection and retraction of the iliac vessels. The dissection may be difficult if adhesions of the vein to the disc are present, and in some cases it may be preferable to expose only the antero-lateral part of the disc in order to avoid any vessel injury.

 

After insertion of the retractor in this antero-lateral situation, it is possible to perform a complete disc resection and vertebral plates decortication under the vessels still protected by the annulus fibrosus. The sympathetic chain lies more laterally along the psoas muscle on the antero-lateral side of the disc. The disc approach is medial and the sympathetic chain is usually not injured during the procedure. The L4 lumbar vessels may be divided to facilitate the retraction of the blood vessels. The division of the ilio-lumbar vein is not necessary.

 

Example of a treated case

 

 
   

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