Proactive, preoperative planning and decision-making regarding anterior and
posterior element resection is vital to concise, effective, and safe spinal
reconstructive surgery. On the basis of the preoperative clinical findings and
imaging, the surgeon creates an operative plan that addresses the various
details of anesthetic management; neurologic monitoring; patient positioning;
patient safety issues; surgical approach; soft-tissue handling; management of
the vascular, hollow viscus, gastrointestinal, and/or genitoureteral
structures; surgical margins; neurologic pathology; and anatomic
considerations regarding fixation and deformity correction. This surgical plan
is shared with the anesthetic and surgical team members with an emphasis on
anticipated intervals of demand, anticipated blood loss, thermoregulation,
positioning needs, and anticipated intervals of increased neurologic and
vascular risk. Collaboration regarding the proactive management of blood loss
and any associated coagulopathy has dramatically reduced the total blood loss,
occurrence of coagulopathy, and associated morbidity in our patients
undergoing complex spinal
reconstruction1.
Figures 1-A, 1-B, and 1-C
present drawings of a surgical tactic and the associated steps for a typical
patient with planned surgical resection of a chest wall sarcoma.
A two-team multidisciplinary approach, including both spinal and
microvascular surgeons, improves outcomes because of the highly specialized
nature of the role of each team. Hence, in our collaborative environment, we
share a review of preoperative radiographs, axial imaging, and a documented
preoperative surgical plan among the various members of the surgical team to
enhance communication regarding potential errors during access and/or pedicle
ablation. It is important to recognize that the segmental vessels are not
present cephalad to T4, and even at T4 they can be quite aberrant; hence, the
decision regarding which rib to mobilize, cephalad or caudad to the defect, is
critical to the efficient conduct of the operation.
For harvest, both anterior and posterior approaches have been used;
however, we prefer to approach the spine through a thoracotomy incision. The
sequence of approaches depends on the pathologic process affecting the spine.
For reconstructions that do not involve tumor or reconstructions that do not
necessitate an anterior approach, a separate posterior flank approach is used.
In the typical tumor patient, an initial posterior approach allows resection
of the diseased vertebral elements and/or preparation of the pedicles for en
bloc resection of the anterior column. With the patient remaining in the prone
position, posterior stabilization is accomplished with use of a rod-screw
construct that spans the defect. The posterior construct is provisionally
tightened, but final tightening and the addition of cross-links is not
performed until after the anterior reconstruction and rib graft have been
completed. During the posterior procedure, and again after the rib is in
place, the spinal defect is shortened in order to impact the anterior
bone-implant interface and enhance spinal cord blood flow. The patient is
prepared again and draped in a lateral decubitus position, such that both the
anterior rib cage and the posterior spinal wound are accessible. The choice of
right or left-sided approach should be dictated by the location of the disease
(i.e., the tumor anatomy), great vessels, and adjacent organs. After a
thoracotomy at the appropriate level to access the diseased segments,
resection of the vertebral bodies is performed and followed by reconstruction
with the autograft.
CRITICAL CONCEPTSINDICATIONS:Segmental spinal defects following resection of extensive amounts of the
anterior and/or posterior elements for tumor. The minimal defect that can be
effectively spanned is 1.5 vertebral bodies (i.e., 4 to 5 cm), while the
maximal defect spanned depends on the rib anatomy of the patient, but is
typically 25 cm.Segmental spinal instability caused by neuropathic conditions.Segmental spinal instability caused by osteolysis of the anterior column
because of infection after staged débridement and appropriately
directed antibiotic therapy.CONTRAINDICATIONS:Placement of a vascularized graft into an area with residual tumor from an
incomplete or subtotal tumor resection.Placement of a vascularized graft into an osseous bed with residual
pyogenic or granulomatous infection.PITFALLS:A multidisciplinary team, including surgeons with established microvascular
skills, is critical to obtaining reliable vascularized tissue and an optimal
result.AUTHOR UPDATE:Our technique has not been modified since the publication of the clinical
series.
CRITICAL CONCEPTS
INDICATIONS:
Segmental spinal defects following resection of extensive amounts of the
anterior and/or posterior elements for tumor. The minimal defect that can be
effectively spanned is 1.5 vertebral bodies (i.e., 4 to 5 cm), while the
maximal defect spanned depends on the rib anatomy of the patient, but is
typically 25 cm.Segmental spinal instability caused by neuropathic conditions.Segmental spinal instability caused by osteolysis of the anterior column
because of infection after staged débridement and appropriately
directed antibiotic therapy.
Segmental spinal defects following resection of extensive amounts of the
anterior and/or posterior elements for tumor. The minimal defect that can be
effectively spanned is 1.5 vertebral bodies (i.e., 4 to 5 cm), while the
maximal defect spanned depends on the rib anatomy of the patient, but is
typically 25 cm.
Segmental spinal instability caused by neuropathic conditions.
Segmental spinal instability caused by osteolysis of the anterior column
because of infection after staged débridement and appropriately
directed antibiotic therapy.
CONTRAINDICATIONS:
Placement of a vascularized graft into an area with residual tumor from an
incomplete or subtotal tumor resection.Placement of a vascularized graft into an osseous bed with residual
pyogenic or granulomatous infection.
Placement of a vascularized graft into an area with residual tumor from an
incomplete or subtotal tumor resection.
Placement of a vascularized graft into an osseous bed with residual
pyogenic or granulomatous infection.
PITFALLS:
A multidisciplinary team, including surgeons with established microvascular
skills, is critical to obtaining reliable vascularized tissue and an optimal
result.
AUTHOR UPDATE:
Our technique has not been modified since the publication of the clinical
series.
Once the anterior aspect of the spine is stabilized, preparation is made
for the pedicled vascularized rib graft. The midline gap in the posterior
osseous elements (i.e., the length of resection) is measured to determine the
length of rib to harvest. It is important to span two spinous processes
cephalad and caudad to the resection with the rib graft; the intent is that
fusion will be enhanced between the rib and spinous processes. The average
length of harvestable rib in our patients is 25 cm. The rib chosen for
posterior pedicle grafting is typically one segment cephalad to the most
cephalad rib of the thoracotomy site (Figs.
2-A and 2-B). A Doppler probe is used to identify the vascular
pedicle at the costovertebral junction. Once the pedicle has been identified
and protected, the intercostal muscles superior and inferior to the rib are
divided with electrocautery, leaving a cuff of intercostal muscle on the
harvested rib. The dissection is then carried back to the proximal
neurovascular bundle, typically with the use of loop magnification and
microvascular surgical technique. This extraperiosteal dissection encourages
maintenance of blood flow to the graft. Throughout this exposure, the vascular
pedicle running on the inferior border of the rib must be identified and
protected; in this manner, the rib is mobilized back to the pedicle. The
pedicle is then protected while the rib is transected approximately 3 cm from
the rib head as it abuts the body. This step is critical because the rib head
in the middle and upper thoracic spine typically sits immediately over the
cephalad portion of the neural foramen, and dissection too medially could
cause a dural tear. Again, most typically, the intercostal nerve is transected
sharply and the end is buried back into soft tissue at approximately 2 to 3 cm
from the foramen. It is important to use bipolar cautery in the neurovascular
foramen to avoid conduction of electrical current in an afferent fashion.
Careful recognition of the depth and contents of the neural canal is
critical.
Next, the periosteum of the rib is divided circumferentially at the level
of the costovertebral junction. While protecting the vascular pedicle, the rib
is osteotomized at this level (Fig.
3). The length of rib needed is then determined, and the rib is
osteotomized at the appropriate length (after adding 2 to 3 cm to be on the
safe side) distally (Fig. 4).
The intercostal vessels are ligated and divided at the distal osteotomy site,
but they are preserved proximally. The segment of rib graft is then rotated
90° on its vascular pedicle and is positioned within the posterior column
defect, while ensuring that the pedicle has not become twisted, kinked, or
otherwise compromised (Fig. 5).
The pedicled graft must be passed through the posterolateral
"window" of communication between the chest and abdominal cavity
and the posterolateral aspect of the spine, deep to the erector spinae
muscles. If rotation of the rib is not feasible, shortening of the stump at
the costovertebral margin is performed to allow more room for transposition.
If the rib still does not transpose to the posterior position through the
posterolateral window because of its length, a partial osteotomy is performed
on its concave, or pleural, surface, and the rib is cracked and folded over
itself, and passed posteriorly. When an osteotomy is performed, the periosteal
sleeve is carefully preserved on the dorsal surface of the rib.
After bringing the rib posteriorly, the periosteum of the pleural surface
is elevated transversely at multiple well-spaced locations while preserving
the vascular pedicle, and unicortical osteotomies are performed at the rib
only. The rib is then cracked at each of these locations to
"straighten" it into a more linear form
(Figs. 6-A, 6-B, and 6-C).
Periosteal tissue is then removed from the ends of the rib, in order to
facilitate contact with the posterior vertebral bone. Following completion and
tightening of the instrumentation, typically a Capner gouge is used to create
flutes of bone and accomplish decortication of the inferior articular process,
the dorsal lamina, and the base of the pedicle. The neurovascular bundle is
protected with an elevator during these maneuvers to avoid injury. With the
laminar bone fluted, we typically incise the periosteum on the surface away
from the neurovascular bundle and use either a burr or an orbital rongeur to
disrupt the cortex on the surface of the rib that is adjacent to the spinous
processes. We then place a perforating towel clamp through the remainder of
the rib and affix the rib to the spinous processes with an absorbable
monofilament suture such as PDS (polydioxanone) or number-1 Vicryl
(polyglactin; Ethicon, Somerville, New Jersey). In placing the suture and
decorticating the surface, we pay attention to not disrupt the neurovascular
bundle and again not encircle the neurovascular bundle with the suture. The
remainder of the graft is then draped across the dorsal aspect of the defect,
and typically an intercalary suture is required to secure the graft to the rod
and keep it from deforming the dorsal dural tube. The caudal end of the graft
is then decorticated and fixed in a similar manner
(Figs. 7-A, 7-B, and 7-C).
In a recent review of our compiled patient data, the mean time of harvest,
rib preparation, and insetting is approximately one hour and fifteen
minutes2. Closure of
the thoracotomy and posterior spinal wounds is accomplished in a standard
manner following placement of drains and a chest tube.
In Figures 8-A, 8-B, and
8-C, images of a representative patient demonstrate bone-healing
and rib-graft incorporation. The posterior placement of a pedicled
vascularized rib graft offers a unique biologic solution to the complicated
problem of extensive posterior column resection.