Page 195 - Zoo Animal Learning and Training

23 Thoracolumbar Lateral Corpectomy

Pierre Moissonnier

Definition and Initial Description of the floor of the vertebral canal at the approached site, enabling
The goal of surgical management of disc herniation is to decompress the removal of extruded/protruded disc material with minimal
the spinal cord by complete removal of herniated disc material manipulation of the spinal cord [13,14]. During the procedure, a
[1,2]. The ideal surgical technique should provide adequate expo- power‐assisted disc fenestration [15] is also performed to prevent
sure to allow removal of the disc material without trauma to the further postoperative disc extrusion [16–19] (see Chapter 22).
spinal cord and without significant postoperative intervertebral Lateral corpectomy was initially described in 15 dogs [13]. Since
instability [3]. In the thoracolumbar region, laminectomy [4–6], then, studies assessing neurological outcome [16,17] as well as the
hemilaminectomy [7,8], mini‐hemilaminectomy/pediculectomy degree of decompression and the biomechanical effects of TLLC on
[9,10], and partial pediculectomy [11] allow exposure of the dorso- vertebral column motion [20,21] have provided a better under-
lateral to lateroventral aspects of the vertebral canal, which corre- standing of the technique and its indications. TLLC can also be
spond to the usual location of acute extruded disc material. In performed in cats to treat chronic (or subacute), ventrally located
patients with a chronic history and patients with disc protrusion, disc herniations or when adhesions are present between the disc
disc removal is technically demanding because of its hard encapsu- material and the dura mater [22,23].
lated nature, ventral (or ventrolateral) location, and adhesion to the
dura mater or to the venous sinus. In these instances, the disc is
often wrapped laterally around the spinal cord, precluding direct Technical Aspects
visualization or access to the disc material via standard hemilami-
nectomy. Inadequate exposure can lead to incomplete removal of Surgical Approaches for Lateral Corpectomy
extruded material or protruding annulus and carries a high risk of In the thoracolumbar area, both dorsolateral [24] and ventrolateral
iatrogenic spinal cord trauma while attempting to remove the her- [25] approaches for TLLC have been described. Since the objective of
niated disc, possibly worsening the patient’s neurological status. TLLC is to remove the floor of the vertebral canal via the vertebral body,
Hemilami nectomy did not initially result in a better outcome com- a ventrolateral approach seems most appropriate. This conclusion
pared with conservative treatment in 36 large‐breed dogs with type was reached in a 2007 study [26] that evaluated the completeness
II (annular) disc protrusion; however, nearly half of the dogs treated of thoracolumbar disc fenestration. Through a dorsal approach, the
conservatively deteriorated within a year [12]. In fact, 9 of 36 dogs paraspinal musculature limits access to the vertebral bodies and limits
treated conservatively were euthanized due to progressive hindlimb the dorsomedial angle needed by the instrumentation to complete the
paresis, while long‐term deterioration of the neurological grade was corpectomy. In contrast, the ventrolateral approach is made ventral
not observed in dogs treated surgically [12]. This suggests that to the paraspinal muscles and dorsal to the ribs and/or transverse
although neurological deficits may remain, surgical decompression process, establishing direct access to the lateral annulus and adjacent
is useful in the management of degenerative annular protrusion [12]. vertebral bodies. The transverse processes and/or the rib heads may be
In order to limit the surgical approach to disc material and to partially removed to improve access to the vertebral body if desired.
limit the iatrogenic trauma associated with its removal, the thora- In the thoracic region, TLLC can be used as part of the surgical
columbar lateral corpectomy (TLLC) technique was developed treatment for spinal deformities to obtain ventral decompression
[13]. TLLC involves the partial removal of adjacent thoracic and/or before realignment of the vertebra [27]. An intercostal thoracotomy
lumbar vertebral bodies that support the extruded/protruded disc provides access to the thoracic vertebral bodies but requires the
material inside the vertebral canal. As such, some authors refer to it transection of the vertebral segmental arteries. Although it is an
as a partial lateral corpectomy [14]. TLLC provides access to most infrequent site for disc herniation, this approach has been used by

Current Techniques in Canine and Feline Neurosurgery, First Edition. Edited by Andy Shores and Brigitte A. Brisson.
© 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/shores/neurosurgery

199