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150 Section III: Spinal Procedures

dorsal laminectomies, variable amounts of the articular facets on stabilize the head and neck. It may also be advantageous to slightly
one or both sides are removed. Extensive bilateral facetectomy is elevate the head and neck. Figure 16.4 demonstrates a patient pre-
generally avoided as the degree of resultant vertebral instability pro- pared and positioned for a dorsal cervical procedure. The cervical
duced can risk subsequent vertebral fracture/luxation. vertebral column is positioned either neutrally or somewhat flexed;
The choice between a complete dorsal laminectomy and a more extension (often misnamed “dorsiflexion”) is avoided, as this would
limited hemilaminectomy is based on the location of the target potentially narrow the interarcuate spaces. The thoracic limbs are
lesion relative to the dural tube, and the amount of space needed for placed cranially, or in some cases secured after crossing them ven-
both visualization and ability to introduce and utilize instruments tral to the neck (the latter has been advocated for approaches to the
within that space. The precision of preoperative imaging studies caudal cervical and cranial thoracic vertebrae as it may help abduct
determines the planned approach. However, it is not uncommon for the scapulae and provide more working room for dissection) [9].
planned hemilaminectomies to be expanded into more complete Landmarks for making the skin incision are somewhat limited.
dorsal laminectomies based on intraoperative findings. Figures 16.1, Cranially, the external occipital protuberance, wings of the atlas and
16.2 and 16.3 show examples of lesions that required either a hemi- possibly the spinous process of the axis may be palpable, and cau-
laminectomy or dorsal laminetomy in the cervical region. dally one may be able to identify the spinous process of T1 and pos-
sibly C7. Because of the extensive musculature that needs to be
Dorsal Surgical Approach incised and retracted to expose the dorsal aspect of the vertebral
Regardless of whether a complete dorsal laminectomy or hemilami- column, a liberal midline incision is generally required to achieve
nectomy is planned, the initial approach is the same. The patient is adequate visualization. The cranial and caudal limits of the inci-
positioned in sternal recumbency. The head, neck, and vertebral sion are initially guided by the longitudinal location of the lesion
column are positioned so as to minimize any rotation left or (i.e., cranial cervical, mid‐cervical, or caudal cervical), and the inci-
right, the introduction of any scoliosis, and to avoid increased pres- sion can be lengthened as needed once deeper landmarks are iden-
sure on the jugular veins (that leads to increased vertebral venous tified. The epaxial musculature has a rich blood supply and even
sinus pressure and greater risk for intraoperative hemorrhage). with nearly perfect midline dissection, there can be substantial
Traditionally, towels and sandbags are used for this positioning, but hemorrhage. A combination of monopolar and bipolar electrocau-
I prefer the use of vacuum positioners. Adhesive tape can be added tery combined with tamponade usually controls most bleeding.
cranial and caudal to the surgically prepared field to further Occasionally one can visualize and grasp a bleeding vessel with a

B

A

C

Figure 16.1 (A) Transverse CT image of a foraminal cervical disc extrusion (arrow) in a chondrodystrophic patient. (B) Sagittal T2‐weighted MRI of a
foraminal disc extrusion in a Great Dane at C4–C5. (C) Transverse T2‐weighted MRI of same patient as in (B) showing foraminal intervertebral disc extru-
sion (arrow). Both patients required a cervical hemilaminectomy for adequate decompression.