Mark A. Knaub and Jeffrey S. Fischgrund

Description

To safely perform decompression of the neural elements in the lumbar spine below the level of the conus medullaris without damage to the neurologic structures.

Key Principles

Decompression of the spinal canal and foramen via laminectomy, partial facetectomy, and foraminotomy can be safely performed without injury to the neurologic structures and dural sac while maintaining the stability of the lumbar motion segments involved.

Expectations

Decompressive laminectomy and facetectomy for spinal stenosis relieves symptoms of neurogenic claudication and radiculopathy in a vast majority of patients. Carefully performed surgery leads to few complications, a short hospital stay, and a rapid improvement in the patient’s symptoms. Patients can expect to return to their activities of daily living in a relatively short period of time.

Indications

Patients with neurogenic claudication or radiculopathy with confirmatory imaging studies documenting spinal stenosis.

Contraindications

• Lack of neural element compromise on imaging studies
  
• Significant instability or deformity on imaging studies
  
• Local skin condition that would put patient at risk for postoperative wound infection (e.g., active eczema, burns, decubitus, or superficial infection)

Special Considerations

Preoperative imaging studies must show evidence of neurologic compression that corresponds to the patient’s symptoms and signs. A complete understanding of the local anatomy contributing to the patient’s stenosis is mandatory to thoroughly decompress the neural elements. Elderly patients should have routine medical evaluation and optimization to lessen the likelihood of perioperative medical complications.

Special Instructions, Position, and Anesthesia

Regional anesthesia via a spinal or general anesthesia can be utilized. The patient is placed in the prone position with the hips and knees flexed. Alternatively, the patient may be placed in a kneeling position. Flexion of the hips allows for straightening of the lumbar lordosis and opening of the interlaminar window, which will make decompression easier. For each of these positions the abdomen should hang free, which decreases the intraabdominal pressure and therefore the central venous pressure, leading to decreased engorgement of the epidural venous plexus. This decreases intraoperative blood loss. Careful positioning of the head and extremities should be employed to avoid iatrogenic neurologic injury or pressure-related problems. Special attention should be given to the eyes/orbits, especially when using general anesthesia.

If spinal anesthesia is employed the puncture must be cranial to the level of planned decompression if possible. A cerebrospinal fluid leak may develop postoperatively if the puncture site is uncovered by the decompression.

Tips, Pearls, and Lessons Learned

Intraoperative imaging is mandatory to confirm the correct level of decompression. The use of anatomic landmarks can be helpful in many cases, but normal variants, such as sacralization of the lowest lumbar segment, may lead to confusion and ultimately to wrong-level surgery. Visualization can be enhanced with an operating microscope or with a combination of loupes and a fiber-optic head light.

Difficulties Encountered

Patients with severe stenosis or synovial cysts often have significant adhesions between the ligamentum flavum and the dural sac. Elderly patients tend to have a thinner, more fragile dural sac. Meticulous surgical technique should be employed to avoid an incidental durotomy.

Key Procedural Steps