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Wheeless' Textbook of Orthopaedics

Diskectomy



- See:
      - Percutaneous Discectomy:
      - Postop Orders for Diskectomy

- Positioning:
    - position patient in modified kneeling position to allow abdomen to hang free, which minimizes epidural venous dilation and bleeding;
    - identify the spinous processes of L3, L4, L5, and S1;

- Standard Posterior Approach:
    - longitudinal incision over the spinous processes of involved level;
    - after noting precise location of tips of spinous processes, incise superficial fascia, lumbodorsal fascia, & supraspinous ligament 
           longitudinally;
    - erector spinae (sacrospinalis) is subperiosteally dissected off lumbar spines intervening interspinous ligament, and laminae;
   - move periosteal elevator proximally and laterally to place erector spinae under tension;
    - using cautery,  subperiosteally strip muscles off lateral surface of spinous process, again moving in a distal to proximal direction;
            - pack each segment w/ sponge after exposure to lessen bleeding;
    - place the end of elevator at junction of spinous process & lamina at the next higher (more proximal) level & continue the dissection;
           - if exposure in opposite direction is attempted, dissection will tend to follow direction of the fibers into the muscle, creating more 
                hemorrage;
    - expose the posterior surface of the laminae and the articular facets;
    - retract muscles laterally using crank retractor;

- Laminotomy:
    - at appropriate level,  ligamentum flavum is incised and cut away with part adjacent laminae, as necessary to expose the extra dural space;
    - denude the lamina and ligamentum flavum with a curet;
    - ligamentum flava must be very carefully incised since Dura may lie immediately adjacent;
           - ligamentum itself may be as much as 5 mm thick;
           - avoid damaging the dura and the contained nerve roots;
   - remove the flap of ligamentum flavum by sharp dissection;
   - grasp the ligamentum flavum with an Allis or Kocher clamp and incise it w/ bayonet pointed knife where it fuses w/ interspinous ligament;
           - during dissection of the ligament keep the point of the knife in view so that the dura will not be nicked;
   - w/ angulated Kerison rongeur carefully remove small shelving portion of ligamentum flavum left laterally;
   - w/ S1 disc herniations:
           - lumbrosacral interspace is large enough to permit expsosure & removal of herniated nucleus pulpsus w/o removal of any bone;
           - if more exposure is needed, remove a small part of the inferior margin of the 5th lumbar lamina; (the lamina which is superior 
                  to the disc)

- Nerve Root Identification:
    - if there is any question as to the position of root, remove lamina until pedicle is visible;
           - this should allow idenification of the upper and lower roots;
           - occassionally nerve root adheres to fragment or to underlying ligamentous structures and will require sharp dissection from these 
                   structures;
   - retract nerve root medially so that underlying extruded fragment or bulging posterior longitudinal ligament can be seen;
           - retract the dura medially and identify the nerve root;
   - if root is compressed by a large extruded fragment, it will commonly be displaced posteriorly;
   - once the nerve root has been identified, apply cottonoid patties to tamponade the epidural veins both caudad and cephalad once the 
           nerve root has been identified and retracted;
           - minimize packing around the nerve root;
           - early packing may displace fragments from view;

- Diskectomy:
    - retract root or dura, identify any bleeding veins & use bipolar cautery;
    - note that excessive medial retraction may injure cauda equina;
    - hold nerve w/ nerve root retractor & expose herniated fragment or posterior longitudinal ligament & anulus;
    - inadequate exposure:
            - if herniation is upward or downward, further removal of bone from lamina and facet edges may be required;
    - w/ large herniation:
            - sacrifice more facet to allow more lateral exposure rather than risk root injury;
            - w/ lateral exposure, nerve root can be elevated which allows herniated fragment to be teased from beneath the nerve root &
                     cauda equina;
    - if disc herniation is not found;
            - palpate posterior longitudinal ligament & seek defect or hole in ligamentous structures;
            - searching in root axilla helps ensure that fragments that have migrated inferiorly are not missed;
            - if no pathology is found, follow the root around pedicle or even outside canal to search for laterally displaced fragments;
            - if disc is entered to remove degenerated fragments, anterior part of annulus must be left intact to avoid damaging the IVC or Aorta;
             - herniated nucleus pulposus may be covered by a layer of posterior longitudinal ligament or may have ruptured thru this structure;
             - if ligament is intact, incise it & remove loose fragments;
             - tear or hole in annulus is then be identifiable in most instances



- Post Operative Management



Lumbar disc surgery: results of the Prospective Lumbar Discectomy Study of the Joint Section on Disorders of the Spine and Peripheral Nerves of the American Association of Neurological Surgeons and the Congress of Neurological Surgeons

The development of low-back pain after excision of a lumbar disc.

The use of dexamethasone in primary lumbar disc surgery. A prospective, randomized, double-blind study.

Should fusion accompany lumbar diskectomy? A medium-term answer.

Interbody fusion and instrumentation.

Titanium-mesh block replacement of the intervertebral disk.



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Friday, April 13, 2012 2:08 pm