Costotransversectomy for thoracic disc herniation
It may be used for lateral thoracic disc herniation, Better for soft disc than for calcified central disc.
An extended costotransversectomy approach is a good option for achieving single staged circumferential fusion for correcting unstable thoracic spine due to both traumatic and non-traumatic pathologies 1).
Position
Prone, usually on chest rolls
Equipment
a) microscope (not used for all cases)
b) C-arm
Implants
If post-op instability is anticipated, thoracic pedicle screws and possibly a cage (e.g. for fracture or tumor, not typically for disc herniation)
Neuromonitoring
Blood availability
Type and cross 2 U PRBC
Consent
(in lay terms for the patient—not all-inclusive):
a) procedure: surgery through the back of the chest to remove a small piece of rib to permit removal of the herniated/calcified disc
b) alternatives:nonsurgicalmanagement,surgeryfromthesidethroughthechest
c) complications: spinal cord injury with paralysis, lung complications including pneumothorax or hemothorax (blood or air outside lungs), possible seizures with MEPs.
Surgical technique
The approach can be somewhat difficult due to the infrequent encounter with the anatomy by most neurosurgeons. Be prepared for a “deep, red hole, where everything initially looks the same and the bony anatomy is not easy to define.” With patience and persistence and the help of an anatomic model in the O.R., the surgeon can get his/her bearings. One of the most helpful landmarks is follow- ing the NVB (or just the nerve root) medially to the neural foramen.
In the O.R., before the prep and skin incision, localizing X-rays are obtained; a spinal needle inserted between 2 spinous processes may be used as a marker.
Patient position: the approach is from the side of the pathology/symptoms; for central disc her- niations a right-sided approach reduces risk of injury to artery of Adamkiewicz (located on the left in 80%.
Options:
1. lateral oblique, ≈ 30° elevated from straight prone, a “bean-bag” is good for stabilization. For a thin patient, the surgeon may stand in front of the patient (gives more horizontal angle of view— does not work as well with heavier patients due to mass of skin/muscle in the way laterally)
2. prone on chest rolls: the chest roll on the side of the pathology should be more medial to allow the shoulder and scapula to fall forward out of the way
Skin incision options:
1. curved paramedian skin incision: apex oriented away from the midline along the slight depres- sion demarcating the junction of the lateral border of the paraspinal muscles with the ribs (≈ 6– 7 cm lateral to midline) centered over the interspace of interest extending ≈ 3 vertebral bodies (VB) above and below. The incision is carried through the skin, subcutaneous fat, trapezius, and (for lower 6 thoracic levels, where most thoracic disc herniations occur) the latissimus dorsi, down to the ribs, and this musculocutaneous flap can be reflected medially as a unit
2. midline incision: need to extend 3–4 levels above and below the level of pathology to get an angle low enough to visualize posterior to the facet in order to access the posterior vertebral body. The inferior aspect can be curved laterally towards the side of pathology. Advantage: a lam- inectomy can more easily be performed if needed (if the angle does not provide adequate visual- ization, as a “bail-out” contingency, a facetectomy may be performed, and pedicle may even be removed to access inferior to the disc space. This usually permits easy decompression of the entire thecal sac. In the thoracic spine, stabilization is optional, and if chosen, unilateral pedicle screws and fusion are usually adequate) Rib removal and thoracic exposure: for a simple biopsy or drainage of a small abscess, removal of only 1 rib may suffice.
★ The rib to be removed is from the level inferior to the disc space to be accessed 2) (e.g. remove the T5 rib to access T4–5 disc space). For most other pathologies, 2 or 3 ribs are often removed 3).
To access a VB, the like-numbered rib and the rib below are removed.
There are a number of ligaments attached to the rib: the intercostal neurovascular bundle (NVB) courses medial to the superior costotransverse ligament, which extends from the superior aspect of the rib to the transverse process of the level above. This ligament and the lateral costotransverse lig- ament are divided and the transverse process is rongeured off (the base of which lies on the lamina directly posterior to the pedicle). This exposes the rib anterior to the transverse process. The perios- teum is incised on the rib from the angle of the rib to the costovertebral articulation, and by subper- iosteal dissection around its circumference the pleura is dissected off the anterior surface of the rib. The NVB is dissected from the deep-inferior surface along with the periosteum. The rib is then trans- ected laterally at the angle (≈ 5 cm lateral to the rib head) with rib shears, it is gripped with a clamp, and is rotated while the ligaments (including the radiate ligaments which attach the rib to the both the VB above and the VB below the disc space at the superior and inferior costal facet, respectively, except T1, 11 & 12 which only articulate with their like-numbered VB) are sharply dissected off the rib which is then removed. The removed rib material may be used for fusion substrate except in cases of tumor or infection. The pleura is then dissected from the deep surface of the adjacent ribs and VB (taking care not to injure the segmental vessels and to dissect the sympathetic trunk off the VB with the pleura). The pleura is then retracted laterally with a malleable ribbon or Deaver retractor.
The intervertebral foramen of interest may be located by following the NVB of the rib above prox- imally, the intercostal nerve (the ventral ramus of the nerve root at that level) enters between the two pedicles. The dura may then be exposed by enlarging the neural foramen by removing part of the pedicles with a high-speed drill and Kerrison rongeurs.
Instrumentation/fusion are rarely required for simple discectomy. Instability due to fracture, tumor, or extensive resection (e.g. with total facet takedown) necessitates surgical stabilization, typi- cally with pedicle screws/rods extending 2 levels above and 2 levels below. Prior to closure, check for air leak by filling the opening with saline and having the anesthesiologist apply a Valsalva maneuver. If an air leak is identified, a Cook catheter may be placed into the pleural space through the surgical exposure, or alternatively a chest tube is placed through a separate intercostal incision after the lam- inectomy wound is closed. A post-op CXR is obtained regardless of whether an air leak is identified.