Lumbar Laminectomy

Samuel M. Davis, MD

Scott D. Boden, MD

Dr. Boden or an immediate family member has received royalties from Osteotech and Medtronic and serves as a board member, owner, officer, or committee member of the American Orthopaedic Association, the Eastern Orthopaedic Association, and the International Society for Study of the Lumbar Spine. Neither Dr. Davis nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.

PATIENT SELECTION

Lumbar spinal stenosis refers to a reduction in the size of the lumbar canal as a result of narrowing in the central canal, the lateral recess, or both. Patients with lumbar stenosis may present with radicular symptoms or reports of neurogenic claudication and classically report back, buttock, or posterior leg pain that worsens with standing and walking.

Indications

The ideal surgical candidate is one who has had a dedicated course of nonsurgical care (ideally, 3- to 6-month minimum) but has not gained satisfactory relief of pain, has a progressive neurologic deficit, or has severe impairment of activities of daily living. Nonsurgical treatments include weight loss, smoking cessation, physical therapy, and injections. A thorough nonsurgical management plan is particularly appropriate and necessary for patients with nontraditional symptoms and/or discordant history, imaging, and physical examination findings. After failed nonsurgical treatment, surgical decompression of the stenotic areas is usually indicated. Patients should also be evaluated for spondylolisthesis or instability because these conditions often require arthrodesis in addition to decompression.

PREOPERATIVE IMAGING

Preoperative imaging should include weight-bearing AP, lateral, and flexion-extension views of the lumbar spine. The images must be scrutinized closely for evidence of spondylolisthesis or instability. Additionally, the spine should be evaluated for osteophytes, asymmetric disk collapse, lateral listhesis, scoliosis, and any bony destruction because these findings may warrant additional workup or surgical procedures. Additional imaging should include MRI, MRI plus CT, or myelogram/CT, depending on the need to highlight neurologic compression and define bony anatomy. For example, a straightforward case of lumbar spinal stenosis can be sufficiently evaluated with a high-quality MRI (Figure 1). On the other hand, if the MRI quality is poor and/or pedicle screws are planned, then a myelogram/CT scan may be the best study. Finally, if the MRI is of good quality but pedicle screws are planned, then a plain CT may help define the bony anatomy. Although MRI is most helpful for visualization
of the neural elements and soft tissues, CT is best to visualize bony pathology, such as ossification of the ligamentum flavum or abnormal pedicular anatomy.

FIGURE 1 Axial T2-weighted MRI of the lumbar spine shows both central and lateral recess stenosis. Note the left facet arthropathy, as evidenced by the high signal intensity in that area.

PROCEDURE

Room Setup/Patient Positioning

The patient can be positioned prone on a Jackson table, a regular operating room table with a bolster under the anterior superior iliac spines and the chest, or a Wilson frame, which allows the abdomen to hang freely, minimizing intra-abdominal venous pressure. The Wilson frame is beneficial because it creates more kyphosis within the lumbar spine, thus making the decompression a little easier, but it may not be as desirable if an arthrodesis is planned. Additional positions include the 90/90 position on an Andrews frame, which is also known as the knee-chest position. The advantage of the 90/90 position is that it decreases intra-abdominal venous pressure, which in turn decreases epidural venous pressure; however, it may also be associated with a higher frequency of complications related to positioning, including compartment syndrome.² Regardless of the specific table used, the abdomen should be free to allow for secondary decompression of the epidural venous plexus.

After positioning, the back should be prepared in a routine sterile fashion. A surgical time-out is performed. All members of the surgical team participate in identification of the patient and the surgical site as well as confirmation of the surgical procedure and preoperative antibiotic administration.

The level(s) to be operated on may be localized percutaneously by one of several methods. We prefer the insertion of two needles near the level estimated by palpation of the iliac crests. The marking needles should be placed slightly off the midline to avoid inadvertent dural puncture. A cross-table lateral radiograph can then be used to approximate the location of the desired incision. The surgical level should be confirmed with a marker or clamp placed directly on a bony structure once the spine is fully exposed to minimize the chance of wrong-level surgery.

SURGICAL TECHNIQUE

Incision and Exposure

A midline incision is made. Two Wheat-lander self-retaining retractors are placed, and the Bovie monopolar electrocautery device is used to dissect through the subcutaneous tissues down to the level of the lumbodorsal fascia. The fascia should be clearly delineated in the midline and no farther laterally than needed to avoid creation of dead space. Clear identification of the fascial layer is done primarily to permit accurate reapproximation during closing to achieve a watertight fascial closure. The spinous process or processes of interest are identified based on the percutaneous localizing needles or an intraoperative lateral radiograph with a marker on a bony landmark. Subperiosteal dissection is undertaken down to the level of the lamina. In an average-size patient, inserting cerebellar retractors for retraction may be useful. In a very large patient, a larger hinged self-retaining retractor may be used. The facets of the level or levels of interest are exposed, taking care not to violate the joint capsule. If uncertainty remains with regard to which level is exposed, the level or levels to be decompressed are accurately identified by inserting two spinal needles into the exposed facets and obtaining an intraoperative lateral radiograph (Figure 2). The facets of interest should be marked with an indelible marking pen. The radiograph is evaluated, and the level is confirmed.

Soft-tissue exposure for decompression should proceed to the lateral aspect of the facet without violating the capsule. The lateral aspect of the pars interarticularis should also be clearly visible. This is critical to avoid excessive thinning of the pars, which places it at risk for iatrogenic fracture.

Decompression

Decompression of the lumbar spine is accomplished in three distinct stages. Stage 1 is the central decompression; stage 2 includes decompression of the lateral recess; and stage 3 involves decompression of the neuroforamina.¹