Appendix 1
The surgical technique involved in a posterior VCR is quite demanding and requires the
operating team to be well-versed in spinal deformity surgical techniques. In revision
patients and even some primary patients, a preoperative 3-D CT scan is helpful to
understand posterior vertebral column pathoanatomy prior to surgery.
We positioned patients on the OSI (Orthopedic Systems Inc.) “Jackson” operative frame,
either the open frame with adjustable pads or for very small patients, the closed frame
utilizing chest rolls. All patients that had undergone preoperative halo-gravity traction (n
= 27) were positioned with their halo in a lessened amount of traction weight. We
strongly mandate using spinal cord monitoring, including motor tract monitoring.
Intraoperative NMEP data was unobtainable in three patients in this series. All three had
prior surgery, while two out of three had prior intradural surgery. The inability to obtain
spinal cord monitoring data does lead us to seriously consider whether we can obtain
adequate correction via a less invasive procedure than a VCR. However, if a VCR is still
indicated because of the severity and/or stiffness of the deformity, then multiple wake-up
tests will have to be performed during the operation to assess neurologic integrity. In
addition, if there are monitoring changes that do not respond favorably to operative
interventions, temporary rods are placed to stabilize the spine and the patient is awakened
from anesthesia and surgery aborted.
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Because of the length of these surgeries and the potential for substantial bleeding, we
believe it imperative to minimize blood loss during these surgeries. This is performed not
only with careful subperiosteal stripping of the posterior vertebral elements, but also with
the use of adjunctive antifibrinolytics such as aprotinin (Trasylol, Bayer HealthCare
Pharmaceuticals, Montville, NJ) or tranexamic acid. We used aprotinin in all pediatric
patients (n = 31) during their procedure. While the use in adults was initially performed,
it is no longer administered to any patient due to the risk of renal failure as recently
documented in the cardiac literature [14].
One surgeon (LGL) performed all surgeries in this series. Following exposure, we
performed posterior column ligament and facet releases/osteotomies (Ponté-type
osteotomies in previously unfused spines and Smith-Petersen osteotomies in previously
fused regions) [4]. These often were performed at the apex of scoliosis or kyphoscoliosis
deformities to provide additional release and also to aid in apical pedicle screw fixation.
Secure pedicle screw fixation was then obtained for the appropriate levels to be included
in the definitive instrumentation and fusion. Pedicle fixation provided stability to the
spinal column above and below the resection area, which is imperative in preventing
and/or treating spinal subluxation which is a real risk with these procedures. All pedicle
screws in this series were placed using the free hand technique espoused by Kim and
Lenke et al using anatomic landmarks and a special blunt, curved gearshift [9].
In the thoracic spine, we removed 5 to 6 cm of the medial rib associated with the level to
be resected prior to the laminectomy to avoid canal intrusion. In primary procedures,
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dissection above the periosteum and around the lateral aspect of the pedicles and
vertebral body was performed using Penfield elevators. We held the soft tissues and the
anterior vasculature from harm’s way with either malleable retractors or special lateral
wall vertebral body elevators (pedicle subtraction osteotomy (PSO) tool set®, Medtronic
Spinal and Biologics, Memphis, TN). In revision cases, a subperiosteal dissection was
performed due to previous scarring, with a similar approach in order to gain
circumferential access to the vertebra(e) to be resected. In both circumstances, the
segmental vessels were kept lateral in a soft tissue cuff and were not violated.
We then performed a wide laminectomy centrally over the apical level(s) to be resected.
Typically, the entire lamina of the level to be resected was removed, the lamina cephalad
to the pedicles above and caudad to the pedicles below. Normally for a one-level
resection, a posterior column laminectomy will result in a 4 to 5 cm exposure of the dura
and neural elements. Next, we encircled the pedicles to be resected and began removal of
the vertebral body. Prior to removing the anterior body, a temporary, stabilizing rod was
placed and attached to at least two or three pedicle screws both above and below the
resection area. In most deformities a unilateral rod was used, but for severe angular
kyphotic or kyphoscoliotic deformities, we recommend bilateral rods to prevent spinal
subluxation. The vertebral body resection began by gaining access to the cancellous bone
of the vertebral body through a lateral pedicle-body entrance. Next, we curetted the
cancellous bone of the body, saving it for bone graft. For a scoliosis or kyphoscoliosis
deformity, resecting the apical concave pedicle can be quite challenging since it is
cortical, and in a pure scoliosis deformity, the entire spinal cord/dural sac is resting on the
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medial concave pedicle. We therefore use a small high-speed burr (we prefer the Midas
Rex® AM8 [Medtronic, Fort Worth, TX]) to carefully burr away the cortical bone along
this concave region. We prefer to perform the concave resection of the pedicle prior to
the convex removal so there is no bleeding into this dependent concave region. This also
allows the concave spinal cord to drift somewhat more medial and remove tension prior
to going to the convexity for completion of the corpectomy. We removed the entire body
except for the anterior shell to keep a thin rim of bone intact on the anterior longitudinal
ligament (ALL) for fusion.
We then performed discectomies above and below using curettes. The last part of the
vertebra to be resected was the posterior vertebral body wall or floor of the spinal canal.
Here it is essential to control epidural bleeding with the judicious use of bipolar
cauterization, topical hemostatic agents such as FloSeal® (Baxter U.S., Deerfield, IL),
Gelfoam® (Pharmacia, Kalamazoo, MI), and cottonoids. This posterior vertebral wall
must be removed in its entirety; we used reverse-angled curettes, Woodson elevators, or a
specialized posterior wall impactor (PSO tool set®, Medtronic Spinal and Biologics,
Memphis, TN) to impale the posterior wall into the ventral defect that had been created.
It is imperative that the ventral spinal cord is completely free of any bony prominences to
avoid impingement during closure. This is especially true at the disc levels, specifically
above but also below, as there tends to be osteophytic lipping in that region which can
cause ventral cord compression if not removed.
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The spinal column was always shortened, not lengthened, with convex compression
performed as the main correcting technique. This was accomplished either with
individual pedicle screws in primary cases where a good bony grip of the vertebrae was
found, or in a construct-to-construct closure mechanism utilizing dominoes at the apex of
the resected area. It is imperative to compress slowly as subluxation and/or dural
impingement can occur at any time. In any deformity that has a degree of kyphosis (GK,
AK and KS), we placed an anteriorly based structural cage to prevent over-shortening of
the deformity and to act as a hinge to provide further kyphosis correction. Following
closure of the deformity and shortening by approximately 1.5 to 2 cm, appropriate cage
templates are utilized to place a slightly loose cage into the anterior column so there is 1
to 2 mm of space between the inferior and superior endplates above and below the cage.
Further compression is performed posteriorly to lock the cage and pivot on it as well.
Once closure was completed, we implanted a permanent contralateral rod with
appropriate correction maneuvers. The temporary closing rod was then removed and a
permanent, final rod placed on the contralateral side. Appropriate compression and
distraction forces, in situ contouring, and other correction techniques may be performed
always being mindful of any resultant affect on the resected area with respect to
subluxation or dural impingement. Next, we confirmed adequate alignment with
intraoperative radiographs. We then decorticated the spine and used copious amounts of
local graft obtained from the resection procedure. To cover the laminectomy defect, the
ribs were split in half longitudinally with the cancellous surface placed along the entire
laminectomy defect from the lamina above to the lamina below. This created a rib
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“bridge” of bone to protect the dura as well as to provide a posterior only fusion. The rib
was held in place with sutures or a crosslink if there was room and if it did not create a
prominence. To confirm the absence of impingement, we performed a final
circumferential check of the exposed dura.
Thirty-seven of these procedures were performed in a single stage with the remaining six
treated with a two-stage procedure. We feel that one should begin the VCR portion
within 5 to 6 hours into the surgical procedure. If this is not the case, then typically we
will place temporary rods into the screw fixation points and return another day to
complete the VCR procedure. The overall goal is to perform the entire procedure in less
than a 10 to 12-hour operative time if this is performed in one setting.
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