Approach Considerations
Of the different techniques currently available, open discectomy with or without the use of an operating microscope remains the most common technique against which the outcomes of other less-invasive surgical techniques are compared. The most common variation of lumbar discectomy involves a minimally invasive approach. For example, a muscle-splitting paramedian exposure of the lateral lamina and medial facet can be accomplished by sequential dilation with various sized tubes that act as a retractor.
An alternative transspinous minimally invasive approach uses the natural corridor through the spinous process without need for muscle splitting or destruction. [18] There is little evidence that minimally invasive techniques offer superior clinical results, but they usually require a smaller incision and can result in less blood loss. [19, 20]
Conventional Lumbar Discectomy
After the patient is positioned, the operative site is radiographically localized. An intraoperative crosstable lateral radiograph is used to identify the skin incision for the appropriate level. The proposed midline incision site is marked and the surgical field prepared and draped. The incision site is infiltrated with 1% lidocaine mixed with 1:100,000 epinephrine. A midline skin incision is made with a No. 10 scalpel along the previously marked incision. The dissection of the subcutaneous tissues is completed using the monopolar electrocautery.
The subcutaneous tissues are retracted using self-retaining Weitlaner retractors. The lumbodorsal fascia is then identified and opened along the spinous process just off the midline using the monopolar electrocautery. At this stage, the desired spinal level should be confirmed with intraoperative radiography.
The paraspinous muscles are stripped from the spinous processes using a subperiosteal technique down along the lamina to the edge of the facets either bluntly or with monopolar cautery. For a discectomy, exposure to the medial edge of the facet joints is generally adequate. Further lateral dissection can damage the capsule of the facet joint and can potentially lead to instability at that level. At this stage, a self-retaining retractor is used to maintain the exposure. The surgical level can again be confirmed before proceeding with bony removal.
The microscope covered with sterile drapes is brought into the field at this stage. The ligamentum flavum is detached from the inferior surface of the lamina using an angled curette, and a hemilaminotomy is then performed using the combination of the high-speed drill and Kerrison rongeurs. Some undercutting of the medial aspect of the facet joint may need to be performed to achieve adequate lateral exposure to the nerve root and underlying disc.
The thecal sac, along with the nerve root, is then retracted medially, and the underlying disc surface can be seen. The posterior longitudinal ligament and annulus fibrosus is then cut using a No. 11 or 15 scalpel. After cutting open the annulus, disc material may begin to extrude and can be removed using pituitary forceps. When placing the pituitary into the disc space, care must be taken not to insert too deep in case of an incompetent anterior longitudinal ligament that could result in injury to the iliac vessels. Up- and down-angled curettes can be used to help release residual disc fragments or tamp down a central disc bulge.
After the surgeon is satisfied that an adequate amount of disc has been removed, the thecal sac and the nerve root is inspected for residual compression and CSF leak. Some surgeons place steroids (40 mg of methylprednisolone acetate [Depo-Medrol] or 4 mg dexamethasone [Decadron]) over the nerve root at this stage to decrease postsurgical inflammation. Placement of a free fat graft over the thecal sac has also been attempted to prevent adhesion formation. The fascial layer is closed using 2-0 Vicryl, which is important to prevent wound breakdown. The skin layer is closed with a subcuticular 4-0 Monocryl, staples, or skin glue.
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Patient with a large right L4/5 disc herniation
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Trans-spinous laminotomy and discectomy
