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24                 Dorsal Laminectomy





                                  in the Thoracolumbar Region




               Cory Fisher and Andy Shores




               Introduction                                       be placed in the  mid‐abdominal region to help elevate the area of
               Dorsal laminectomy of the thoracolumbar region has been   interest. Once positioned to the surgeon’s discretion, the animal is
               described for treatment of intervertebral disc disease [1–17], frac-  secured in this position using tape. A dorsal midline skin incision
               tures  [12–16],  neoplastic  processes  [12–16,18,19],  cysts  causing   is made for a distance of a minimum of two vertebrae cranial and
               compression to spinal cord [20–22], and other disease processes   caudal to the affected intervertebral disc space. The subcutaneous
               that cause spinal cord compression [23,24]. Dorsal laminectomy is   fat and fascia are incised using blunt/sharp dissection with
               used to access dorsal, lateral and ventral aspects of the spinal canal   Metzenbaum scissors until the deep lumbodorsal fascia is reached.
               depending on the type of dorsal laminectomy appropriate to the   A continuous scalloped incision is made bilaterally around each
               disease  process  [13,14]. Numerous  modifications to the dorsal   spinous process in the superficial and deep external fasciae of the
               laminectomy procedure have been described since Greene’s first   trunk.  Using  periosteal  elevators,  the  epaxial  musculature  is
               report in 1951 [17]. Dorsal laminectomies are classified by the   reflected laterally on both sides to the level of the accessory pro-
               extent of the vertebrae removed. The four types of dorsal laminec-  cess. Gelpi retractors are used to retract the epaxial musculature
               tomies described in veterinary neurosurgery are (listed in order   for better visualization of the dorsal and lateral aspect of the verte-
               from the least amount of bone removed to the most) Funkquist B,   bral column [12,13,19,26]. The spinous processes of the vertebrae
               modified dorsal laminectomy, Funkquist A, and deep dorsal lami-  cranial and caudal to the affected disc space are removed with bone
               nectomy [13–15]. The two most commonly used are the Funkquist   rongeurs [12–14,19]. A laminectomy is performed using a high‐
               B and modified dorsal laminectomy [3]. An osteotomy of the   speed surgical air drill [12–14,19]. Because the dorsal lamina is
               spinous process instead of the traditional ostectomy has also been   thinner than the lateral lamina, frequent pausing of the drilling is
               reported [25]. Unilateral excision of the vertebral arch, including   necessary to assess bone depth at the drilling site [3]. The outer
               the articular processes (facetectomy), accessory process (fora-  cortex of the lamina  normally has a whitish tint. The medullary
               menotomy) and pedicle (pediculectomy), have been performed   bone is recognized by its reddish‐brown color. The inner cortex of
               after osteotomy of the spinous process [25].       the lamina is very thin and also whitish in color [12–14,19]. Small
                 The type of dorsal laminectomy performed is based on the dis-  Lempert or Kerrison ronguers are used to expand the laminectomy
               ease process causing neurological dysfunction. Advanced diagnos-  after entering the canal [3,13, 14]. The extent of bone removal is
               tic imaging (myelography, CT, CT with myelography, or MRI) is   dictated by the lesion of interest and amount of accessibility of the
               used to determine the extent of the disease process. Once the extent   vertebral canal needed (Funkquist A, Funkquist B, or modified
               of the disease process is recognized and classified, the type of dorsal   dorsal laminectomy).
               laminectomy is chosen.                               After completing the decompression and the remainder of an
                                                                  indicated procedure (tumor excision, opening of a subarachnoid
                                                                  diverticulum, removal of scar tissue, etc.), the surgical site is thor-
               Surgical Approach (Video 24.1)                     oughly lavaged with warm physiological saline and either gelatin
               The patient is clipped and aseptically prepared for surgery then   sponge or autogenous fat graft is placed over the laminectomy
               positioned in sternal recumbency with the spinous processes   site  to  prevent  dural adhesions [3, 12]. Synthetic nonabsorbable
               perpendicular to the surgery table. A rolled towel or sandbag may   suture can then be used to span over the laminectomy site or the


               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



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