Lumbar Laminectomy for the Treatment of Spinal Stenosis

CHAPTER PREVIEW

CHAPTER SYNOPSIS:

Lumbar spinal stenosis is defined as the compression of lumbar spinal nerve roots and is usually seen in the older population. This chapter discusses the pathophysiology, differential diagnosis, imaging modalities, surgical management, postoperative care, and surgical outcomes.

IMPORTANT POINTS:

Indications
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  Neurogenic claudication, radicular leg pain, or both
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  Failure of 6 to 12 weeks of conservative treatment
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  Neurologic deterioration
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  Bladder or bowel changes, or both
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  Worsening leg symptoms
Contraindications
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  Patients not medically stable to undergo general anesthesia
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  Back pain without leg symptoms
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  No evidence of stenosis on imaging studies
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  Active systemic infection or local skin disease
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  Inadequately treated coagulopathies
Complications
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  Hematoma
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  Dural tear
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  Infection
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  Deep vein thrombosis
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  Atelectasis
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  Ileus or urinary retention

CLINICAL/SURGICAL PEARLS:

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All areas of neural compression must be decompressed to prevent recurrence of symptoms.
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Partial discectomy may be necessary to further decompress the nerve root.
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Local bone removed should be saved in the event that bone graft is necessary.
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Perform central decompression initially.
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Evaluate the entire length of the decompression and adequately obtain hemostasis before closure.

CLINICAL/SURGICAL PITFALLS:

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Avoid excessive blood loss by using local subcutaneous epinephrine, controlling mean arterial blood pressure, and using care not to overhydrate the patient with intravenous fluids.
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Maintain the facet joints and facet joint capsules if possible to avoid postoperative pain and instability.
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Avoid damage to the dura by protecting it with a thrombin-soaked neuro pattie and by placing a Woodson elevator or Penfield #3 elevator between the dura and the Kerrison.
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Use care not to remove the pars interarticularis, especially above the L4 level, because this may risk iatrogenic fracture and secondary instability.

VIDEO AVAILABLE:

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Lumbar spinal stenosis produces neural compression resulting in neurogenic claudication in approximately two thirds of patients and radicular leg pain (usually affecting the L5 nerve root) in approximately one third of patients. Patients usually describe a decreased ability to ambulate because of lower extremity symptoms including pain, numbness, tingling, and weakness affecting one or both legs. They often need to sit down, lean forward (shopping cart sign), or both to relieve their leg symptoms. As the population continues to grow older and remain active, the incidence of patients developing symptomatic lumbar spinal stenosis often requiring treatment including surgery is increasing. It must be kept in mind that, in this older population, a greater incidence of vascular, as well as knee and hip arthritic co-morbidities, needs to be taken into treatment consideration.

INDICATIONS AND CONTRAINDICATIONS

As with any spinal surgical condition, a thorough history, physical examination, and appropriately directed imaging studies are the key elements in formulizing an adequate treatment protocol. Initially, nonoperative management is started and may include nonsteroidal anti-inflammatory drugs, and/or other oral medications, physical therapy, chiropractic treatment, altered physical lifestyle, and lumbar epidural injections. If 6 to 12 weeks of nonoperative care fails to provide enough lower extremity symptom relief, then surgical intervention is indicated. Obviously, surgical management would be indicated before a reasonable period of nonoperative management in the face of neurologic deterioration, bladder and/or bowel changes, or worsening leg symptoms. Once a reasonable period of nonoperative management fails to provide adequate relief, and imaging studies reveal spinal stenosis, surgical management is indicated. Imaging studies include plain radiographs including anteroposterior, neutral lateral, and flexion/extension lateral views of the lumbar spine. This will assess bone quality, alignment, and instability if present. Advanced imaging studies include magnetic resonance imaging (MRI), which is the gold standard ( Figs. 16-1 and 16-2 ). Computed tomography myelography in certain scenarios is also extremely beneficial, especially in patients with pacemakers or other implanted metallic devices precluding the use of MRI and in revision cases with instrumentation that may cause scatter, as well as to better evaluate the bony spinal anatomy if needed. Contraindications include patients not medically able to undergo a general anesthetic, a paucity of lower extremity symptoms (back pain and no leg symptoms), and a lack of imaging findings supporting the diagnosis of stenosis. Other uncommon contraindications include an active systemic infection, local skin rash over the posterior lumbar operative site, and bleeding disorders (coagulopathies) not appropriately treated.

SURGICAL TECHNIQUES

Lumbar laminectomy is the time-honored procedure in the surgical management of lumbar spinal stenosis. It provides neurologic decompression of the entire lumbar and sacral nerve rootlets and nerve roots. All areas of neural compression need to be decompressed to provide adequate and long-standing leg symptom relief. Commonly, all three anatomic areas of the lumbar canal need to be decompressed, and include the central canal (spinous process, lamina, and ligamentum flavum), lateral recess (partial facetectomy and lateral ligamentum flavum), and foramen (partial facetectomy and partial removal of the pars interarticularis). At times, a partial discectomy also needs to be performed as well. If any neural compression still exists after surgery, the patient may continue to experience leg symptoms in the immediate postoperative period or at a future time. The procedure starts with an adequate and meticulous exposure. Blood loss should not exceed more than 100 to 200 mL. The use of local subcutaneous epinephrine, keeping the mean arterial blood pressure at a lower level and avoiding overhydrating the patient with intravenous fluids, will help with a lower blood loss. Cell Saver (Haemonetics Corp., Braintree, MA) is seldom needed in nonfusion cases. Dissection with electrocautery is taken to expose the pars interarticularis at every level that is being addressed. If the pars is not exposed, then danger in removing it during the decompression can occur, possibly leading to iatrogenic instability. In addition, the facet joints and especially the facet joint capsules should be maintained as much as possible. Damaging these structures may lead to increased postoperative degeneration, pain, and instability.

Once the exposure is completed, and the appropriate levels are confirmed, attention to neural decompression commences. All lumbar spinal levels producing stenosis need to be included in the surgical decompression. Areas of severe, moderate-to-severe, and usually moderate stenosis need to be addressed. Once the spinous processes are removed, the canal is entered. The lamina can be partially removed with a Leksell rongeur or burr, or both, to decrease the lamina thickness, making further removal with a Kerrison rongeur easier. If bone graft is needed during fusion procedures, the local bone removed should be saved for later reimplantation. The spinal canal is entered at the distal most spinal segment, usually under the inferior aspect of the L5 lamina. The ligamentum flavum is peeled off the underside of the lamina using a curved curette. Once access into the spinal canal is initiated, a Woodson or Penfield elevator can be placed in a cephalad and caudad direction, making sure it can be easily advanced and no adhesions are encountered.

Once entry into the spinal canal is established, Kerrison rongeurs, usually #3, #4 or #5, are used to remove the lamina in a cephalad direction until the entire lamina is removed, as well as the ligamentum flavum between L4 and L5. This process is continued to higher lumbar levels until all spinal levels producing stenosis are decompressed. As the decompression moves forward, advancing a thrombin-soaked neuro pattie between the dura and lamina/ligamentum adds protection against durotomies while the Kerrison rongeur is used. Additional dural protection can be performed by the assistant surgeon placing either a Woodson elevator or Penfield #3 elevator between the dura and the primary surgeon’s Kerrison rongeur.

Some surgeons perform a cephalad-directed central decompression first followed by addressing the lateral recesses and foramen in a caudad direction. By performing the central decompression initially, it allows mild medial dural retraction by the assistant, whereas the primary surgeon can gain access underneath the facet joints and lateral ligamentum flavum so adequate lateral recess decompression can be accomplished. The assistant can use a pattie placed longitudinally and held with a sucker in one hand and a Penfield or Woodson elevator in the other hand, allowing the primary surgeon to remove bone and ligament between the assistant’s instruments with good visualization. Attention not to remove the pars interarticularis is extremely important, especially above L4, where it is narrower, not to produce an iatrogenic pars fracture leading to instability.

Once the lateral recesses are adequately decompressed, the foramen are evaluated utilizing a Woodson, Penfield, or Murphy probe to assess whether a foraminotomy needs to be done. Once completed, the entire length of the decompression is evaluated centrally, in the lateral recesses and the foramen ( Fig. 16-3 ). It is a good idea to perform a Valsalva maneuver to assess for an inadvertent durotomy. All hemostasis should be obtained, and closure is performed. Most surgeons advocate a watertight fascial closure over a subfascial drain. Once the subcutaneous layer is closed, the skin can be closed with either staples or a running 3–0 Prolene to be removed later, or a dissolvable 3–0 Monocryl suture augmented with Steri Strips (3M, St. Paul, MN). After skin closure, 0.5% Marcaine can be injected at the incision site to help with postoperative analgesia.