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228 Section III: Spinal Procedures

Figure 26.9 Intraoperative image of a completed dorsal laminectomy Figure 26.11 Intraoperative image of a dorsal laminectomy. The cauda
providing visualization of the cauda equina (yellow arrow). The L6 spinous equina is gently retracted while the dorsal annulus is incised (arrow) and
process is cranial to the laminectomy (asterisk) and the facetal joints are discectomy is performed by removing the contents of the disc using curettes
located laterally. The laminectomy can be carefully widened as required or a high‐speed burr. Source: Courtesy of Dr. Laurent Guiot.
using Kerrison rongeurs. Source: Courtesy of Dr. Laurent Guiot.

ligament are excised the patient often develops hyperpnea, tachy-
cardia, and elevated mean arterial blood pressure [53]; these
changes may support the concept of discogenic pain in DLSS.
Discectomy can be accomplished using curettes but some sur-
geons prefer to use a high‐speed drill (power fenestration). In
either instance the cauda equina must be carefully protected. Half
of the disc can be resected while retracting the cauda equina to
one side, then it can be retracted to the opposite side to resect the
other half of the disc (Figure 26.11) [6].
Following adequate decompression, the cauda equina is gener-
ally covered with an autogenous fat graft to prevent the formation
of a laminectomy membrane that may cause recurrence of com-
pression [54].

Variation
In order to decrease the amount of instability created by the dorsal
laminectomy procedure, a partial laminectomy approach has been
described [55]. This limited laminectomy approach involves
Figure 26.10 Intraoperative image of a dorsal laminectomy showing gentle removal of the ligamentum flavum and a laminectomy of only S1.
retraction of the cauda equina to expose the bulging dorsal annulus of the As a result the exposure to the cauda equina is more limited but
intervertebral disc (arrow). Source: Courtesy of Dr. Laurent Guiot.
there is no expected loss of stability. Biomechanical testing of this
laminectomy in conjunction with discectomy has not been done
the L7 nerve root examined using a probe. The L7 nerve root should but one would expect it to be more stable than a standard dorsal
move a few millimeters with minimal traction [7]; if this is not pos- laminectomy. One study of 86 dogs treated with this procedure
sible, further decompression (partial or complete facetectomy, or reported very good outcomes [55].
foraminotomy) is indicated.
The IVD is often visualized as protruding dorsally within the Foraminotomy and Facetectomy
spinal canal and can otherwise be palpated by running a nerve Foraminotomy is an additional procedure that is commonly per-
retractor, ball‐end probe, or other blunt instrument gently under formed to enlarge the L7–S1 foramen in order to decompress the L7
the cauda equina (Figure 26.10). Patient positioning (pelvic limbs nerve root at the point of exit from the vertebral canal. This proce-
forward/flexed spine) can distract the dorsal annulus and may dure attempts to preserve stability by undercutting rather than
artificially decrease intraoperative annular protrusion compared removing the articular processes [2,7,56,57]. If foraminotomy does
with preoperative advanced imaging; this is especially true in dogs not adequately decompress the L7 nerve root, a facetectomy can
with dynamic lesions. With the cauda equina gently retracted also be considered. Facetectomy consists of extending a standard
using a nerve retractor or smooth blunt probe, the dorsal annulus dorsal laminectomy laterally (dorsal to the foramen) by removing a
can be visualized and excised. This allows for fenestration or portion of the articular facets. Unlike foraminotomy, the facetec-
partial discectomy to relieve the compression caused by a pro- tomy procedure has been shown to cause significant instability in
truding IVD. When the dorsal annulus and the dorsal longitudinal normal canine cadaver spines in vitro [58].