Lumbar Laminectomy

Illustrative Case

A 72-year-old male with multilevel L2-5 stenosis presented with neurogenic claudicating back and bilateral leg pain refractory to conservative treatment (Figure 19-1).

Figure 19-1 ▪ Anteroposterior and lateral x-ray showing multilevel spondylosis but no significant deformity or listhesis. There appears to be an autofusion at L1-2.

Radiologic Assessment

On upright x-ray, identify instability, such as significant scoliosis, degenerative spondylolisthesis, or lateral listhesis that may require fusion.
Evaluate on the MRI
- If there is a superimposed disk herniation that may require a diskectomy in addition to laminectomy.
- If there is a synovial cyst, which during decompression can look similar to a nerve root. Often we recommend fusion in the presence of a significant synovial cyst, especially in the presence of synovitic joints, in order to prevent postoperative instability and recurrent cyst formation.
- If the stenosis is central, lateral recess, foraminal, or a combination of the three.
  - Foraminal stenosis is best assessed on parasagittal T1 and T2 views (Figure 19-2).
  - Central and lateral recess stenosis is best assessed on axial T2 MRI (Figure 19-3).
- Also note the tightest areas of compression that may have dural adhesions or deficiencies increasing the risk of an incidental durotomy.

Figure 19-2 ▪ T2 midsagittal MRI demonstrates disk morphology, alignment when recumbent, and, to a certain extent, central canal stenosis. Left and right, T2 parasagittal MRI best demonstrates foraminal stenosis to varying degrees from L3 to S1.

Figure 19-3 ▪ Axial T2 MRI best demonstrates central and lateral recess stenosis, in this case at L2-3, L3-4, and L4-5.

Positioning

We generally use a Jackson frame, which allows the abdomen to hang free, thus reducing bleeding from the epidural venous plexus.
- In contrast to fusion, we do not necessarily try to increase lordosis during positioning. On the other hand, if positioned excessively hypolordotic, areas that are stenotic in normal upright posture may be partially relieved of compression and thus not identified as targets of decompression at the time of surgery. Therefore, we try to mimic the neutral upright lateral x-ray alignment, because this will be the physiologic position in which the completed decompression needs to provide adequate room for the roots and cauda equina.
Alternatively, a Wilson frame on the Jackson can be used, which decreases lordosis and opens up the interlaminar space. However, this strategy is more useful for microdiskectomy than laminectomy, where relieving bony stenosis may not be a primary goal, and the hypolordotic position can facilitate surgery by requiring less bone removal to access the herniated disk.

Localization

A sufficient incision usually spans from the mid- to cephalad portion of the pedicle above the target disk level to the bottom of the pedicle below the target disk level. Smaller or larger incisions may be used depending on patient body habitus (Figure 19-4).

Figure 19-4 ▪ Estimated incision localization with needles. The needles span from the midpoint of the L4 pedicle to the L4-5 disk space. Based on this x-ray, the appropriate incision for an L3-5 decompression would span about 5 mm caudal to the top needle, to about a 1 cm caudal to the bottom needle.

Approach

Midline incision is made and strict subperiosteal dissection is performed down to the medial facet joints.
A second x-ray is then taken, with needles ideally on the facet joint(s) of the motion segment(s) to be decompressed (Figure 19-5).

Figure 19-5 ▪ Second localization x-ray with spinal needles at L3-4 and L4-5 facet joints. These correspond to the disk levels being decompressed.
The facet capsules are carefully left intact.
Identify the lateral border of the pars, especially at the cephalad level, to ensure that the pars stays intact after laminectomy.
Adequate exposure of the pars allows the surgeon to define limits of the decompression without causing an iatrogenic pars fracture (Figure 19-6).

Figure 19-6 ▪ Diagram showing the extent of exposure needed to complete a one motion segment laminectomy (eg, L4-5). The L4 and L5 pars, as well as the L4-5 facet joint are clearly seen.

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