Posterolateral Decompression

- Discussion:
    - most indicated for unstable burst frx w/ cord impingement along w/dural tear and nerve root entrapment from frx of posterior elements;
    - most effective at the thoracolumbar junction and in the lumbar spine as more direct means of reducing the bony fragments;
    - procedure involves hemilaminectomy and removal of portions of one pedicle w/ high speed burr to allow posterolateral decompression 
          of the dura along its anterior aspect.
    - w/ angled instruments, the bone can be curetted out of the canal or tapped back into the vertebral body;
    - in thoracic spine, where less room is available for cord, this technique may involve increased risk to the neural elements;
    - following decompression, it is necessary to select implant for fixation
          as well as number of levels to be fused;
          - consider pedicle screw implants in lumbar levels to preserve motion, where as hook implants can be used in the thoracic levels (where
                 significantly less motion occurs);
          - rod long / fuse short philosophy: disadvantages;
                 - unclear how long hardware needs to remain in place;
                 - damage to facet capsules usually occurs w/ hook insertion;
                 - facet immobilization may lead to joint fibrosis or degeneration;

- 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 
    - erector spinae (sacrospinalis) is subperiosteally dissected off lumbar spines intervening interspinous ligament, and laminae;
           - erector spinae group consists of the spinalis, longissimus, and the iliocostalis;
           - the multifidus and quadratus lumborum lie below the erector spinae musculature;
    - 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:

- 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 
           - 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

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

Last updated by Data Trace Staff on Tuesday, December 27, 2011 4:04 pm