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31 Trans-sacral Lumbar Interbody Fusion
421
far enough into the sacrum to ensure the outer
diameter of the 10 mm dilator sheath is placed
completely within the sacral cortex. Once the
10 mm dilator with sheath is docked into the
sacrum, its body is carefully removed, leaving
the dilator sheath behind.
A 9 mm cannulated drill is then inserted over
the guide pin to create a channel within the L5–
S1 disc space by rotating the drill in a clockwise
direction (Fig. 31.10). Biplanar fluoroscopy
should be used at all times while drilling [6, 13].
The discectomy is performed using a variety
of disc cutters of different configurations and
sizes. The loop cutters are designed to debulk the
nucleus pulposus and lightly abrade the end
plates. Tight disc cutters are designed to debulk
the nucleus and lightly abrade end plates in tight
disc spaces (less than 2.5 mm). Multiple tissue
extractors are used to remove the disc material.
In addition, end plate rasps are available to scrape
the remaining tissue and cartilage off the vertebral end plates. They provide aggressive end
plate preparation, increasing blood supply and
providing the necessary fusion bed, similar to a
curette. A trigger system on the loop cutters
allows tip angle adjustment to match the angle of
the end plate.
The discectomy can be thought of as a twostep process, utilizing cutters for the first step
and end plate rasps for the second step. We recommend starting with the L5 portion of the disc
and using small radial cutters and then moving
up to large radial cutters for the center of the
disc space. This should be followed by small
and large radial down cutters for the S1 portion
of the disc space. We recommend using small
cutters in the direction of least constraint first
(Fig. 31.11) [4, 13].
Fig. 31.10 The use of the 9 mm cannulated drill
Fig. 31.11 (a) The use of fluoroscopy to confirm accurate position of the disc cutters prior to beginning the discectomy.
(b) The circular area of discectomy with avoidance of the annulus
422
G. Majeed and F. Asgarzadie
Each cutter should be utilized twice. Use the
first pass to remove the nucleus pulposus and
the second pass to prepare the end plates.
Several tissue extractors should be used to
remove the loosened disc material (Fig. 31.12).
This sequence should be continued until the tissue extractors come out clean. The disc space
should be irrigated and suctioned prior to bone
grafting.
Bone grafting is performed before drilling
into the L5 vertebral body to avoid packing the
defect with bone graft material (Fig. 31.13).
A beveled bone graft inserter is advanced through
the working cannula into the intended disc space.
Approximately 2–3 cc of bone graft per tube is
inserted into the distal end of the inserter. The
bone graft material is then slowly pushed into the
disc space with the plunger. Care should be taken
not to advance the beveled edge of the tube into
the L5 vertebral body. The beveled tip allows for
rotational delivery. One should be careful not to
deliver bone graft material directly posterior in
patients who have had a prior discectomy at the
same level [1, 4].
Fig. 31.12 (a) A tissue extractor and a disc cutter with extracted disc material placed on the surgical field. (b) The use
of several disc extractors to remove loosened disc material
Fig. 31.13 Bone grafting performed through the beveled bone graft inserter
31 Trans-sacral Lumbar Interbody Fusion
423
For improved bony fusion, the graft material
should have osteoconductive, osteoinductive,
and osteogenic properties. Several options are
available. The bone recovered during the creation
of the intervertebral tract can be mixed with
osteoconductive matrices (bone graft extenders)
with or without osteoinductive properties. Iliac
crest autograft can also be obtained minimally
invasively and combined with other agents.
Approximately 5–8 cc of graft is used. Bone marrow aspirate is also a valid option. This is normally harvested from the iliac crest or the
vertebral body. The aspirate should then be combined with matrix, ceramic, or allograft chips.
Using the appropriate bone graft material is
imperative for good bony fusion and long-term
stability [1, 8, 9, 13, 15, 22].
After insertion of the bone graft material, the
beveled guide pin is reinserted. The 10 mm dilator sheath is removed. A 12 mm dilator with
sheath is passed over the guide pin. The 12 mm
dilator is subsequently removed, leaving the
sheath in place. A 10.5 mm drill is then used to
drill past the S1 end plate. Care should be taken
not to remove any of the bone graft material during removal of the drill.
The beveled guide pin is reinserted and tapped
into the inferior end plate of L5. A 12 mm dilator
tamp is then used to advance the 12 mm dilator
tamp and sheath into the L5 vertebral body so
that sheath is flushed against the end plate of L5.
The 10.5 mm drill is then used to drill 10–15 mm
into the L5 vertebral body. Fluoroscopy should be
used to verify depth at all times. A dilator trial is
then used to select the appropriate size implant.
At this point a conformable tip tubular retractor
can be inserted and docked into place. It is a lightweight option which offers rigidity due to its inner
metal liner and conformability due to its radiopaque silicone tip. The outside liner which is a
continuation of the silicone tip offers proper lubrication due to its hydrophilic coating. The conformable tip tubular retractor has been demonstrated to
minimize bowel perforations near the promontory.
The assembled implant construct consisting of
the appropriately sized S1 anchor, distraction rod,
and L5 anchor is inserted into the conformable tip
tubular retractor until the superior end is engaged
with the sacrum. At this point, clockwise rotation
is applied to insert the implant into the L5 and S1
vertebral body (Fig. 31.14). Please note that the
waist section between the anchors should be in
the L5/S1 disc space to allow for distraction.
The distraction driver is then used to obtain
the desired amount of distraction as deemed necessary. The varying diameter allows the rod to
have two different thread pitches. This allows for
dynamic axial distraction upon implantation with
restoration of disc height and the potential for
indirect decompression of the neural foramen [6].
The final step involves insertion of the fixation rod. We recommend using fluoroscopy to
ensure that the L5 anchor does not advance during this step. Proper fixation can be confirmed
using fluoroscopy as the tip of the fixation rod
will be seen protruding from the superior end of
the L5 anchor.
The next step involves insertion of the fixation
rod (Fig. 31.14). This brings the entire construct
together and provides bending stability at the
L5–S1 section of the implant [13]. Upon completion, the retractor is removed. The wound
should be thoroughly irrigated followed by a layered closure.
Posterior instrumentation can be applied
either before or after the trans-sacral approach.
The type of approach used is based solely upon
the surgeon’s preference.
Fig. 31.14 Insertion of the fixation rod
424
G. Majeed and F. Asgarzadie
Illustrative Case
History
A 45-year-old female who presented with low
back pain and bilateral S1 radiculopathy for
2 years. Worsening of radicular symptoms noted
with movement. No saddle anesthesia, bowel/
bladder dysfunction noted. No reported history of
trauma noted.
Physical Exam
General: NAD, overweight
GCS 15, alert and oriented
Muscle strength: 5/5 muscle strength noted
except in B/L planar flexor 4+/5
Sensation: mildly diminished to light touch
Left > Right S1 dermatomal distribution
Rectal tone: Intact, + perianal sensation to
pinprick noted
Imaging
Flexion/extension lumbar spine radiographs:
Grade 2 isthmic spondylolisthesis at L5–S1 noted
(Fig. 31.15a)
Treatment
The patient was deemed suitable for the transsacral approach and underwent L5–S1 pedicle
screw placement through a minimally invasive
approach with subsequent reduction of the spondylolisthesis followed by trans-sacral rod
implantation to “lock” the reduction in place.
The postoperative films clearly illustrate satisfactory placement of the trans-sacral implant
along with restoration of disc height post-distraction (Fig. 31.15b).
Outcome
She had a benign postoperative course and serial
postoperative imaging revealed excellent bony
fusion.
Technical Pearls
• A preoperative MRI visualizing the most cau-
dal point of the coccyx or a CT scan with rectal
contrast improves the accuracy of the opera-
tive trajectory and allows the surgeon to avoid
important neurovascular structures [13, 14].
Fig. 31.15 (a, b) Pre- and postoperative films after L5–S1 trans-sacral fusion and pedicle screw fixation
31 Trans-sacral Lumbar Interbody Fusion
425
• Preoperative imaging should be carefully
reviewed to identify any neurovascular anomalies in the midline safe zone.
• The preoperative imaging should also be used
to check for rectal adherence to the sacrum
and accurately assess the height of the disc
space [13, 14, 16].
• Proper patient positioning is extremely important for the success of this procedure. The
appropriate amount of lumbar lordosis should
be achieved preoperatively by placing pillows
under the hips to elevate the sacrum prop with
pads under the hips to elevate the sacrum and
the patient’s legs apart.
• Complete bowel prep prior to surgery gives
the additional benefit of the bowel being
empty and flexible, so it moves forward easily and helps to decrease the risk of bowel
injury.
• If a bowel retractor is used, proper dissection
with the curved dissector is critical to its successful deployment.
• When deploying the retractor system, be
mindful of the amount of contrast injected as
too much contrast could result in overinflation
and eventual rupture of the retractor system.
• Proper lumbar lordosis should be ensured
prior to draping and confirmed by fluoroscopy
if needed.
• During patient positioning the thighs can be
spread apart by placing pillows between the
legs to allow enough working room to drop
the hand during initial access to keep the tip of
the blunt dissecting tool in contact with the
anterior surface of the sacrum.
• To minimize the risk of incision-related bowel
injury, the coccyx can be used as a rigid backstop. Direct bowel injury with the incision can
also be avoided by incising the skin only and
never “hubbing” the skin knife.
• The trajectory and placement of the beveled
guide pin should be confirmed with fluoroscopy. If the guide pin is improperly positioned,
it should be removed completely and repositioned again under fluoroscopic guidance until
the proper trajectory is achieved.
• When removing the dissecting tool back over the
guide pin, careful attention should be paid not to
disengage the guide pin inadvertently. This can
be avoided by using an extension attachment
prior to removal of the dissecting tool.
• When removing the drill, continue rotating it
in a clockwise direction. This allows bone
pieces to remain in the flutes of the drill during
removal. These pieces can be later used as part
of the bone graft.
• Fluoroscopy should be used to confirm accurate position of the disc cutters prior to beginning the discectomy. It should be ensured
that the cutters are not going too far anterior
or posterior to ensure the integrity of the
annulus.
• The flexible blade of the radial cutter should
be retracted into the cutter sleeve prior to
insertion and removal from the disc space.
• In patients with a history of discectomy, the
bevel of the bone graft inserter should be
aimed anteriorly and laterally to avoid accidental spillage into the spinal canal.
Complications
According to a large retrospective study, the
trans-sacral approach had an overall complication rate of 1.3%.
Some of the complications associated with this
procedure are the following: infection, bleeding
complications, bowel/rectal perforation, vascular
injury, neurological injury, hardware failure, and
osseous fracture.
The most serious complication associated
with this approach is injury to the rectum or
other surrounding abdominal structures. The
rate of bowel perforation with the trans-sacral
approach has been reported to be between 0.4%
and 2.9%. Lindley et al. [6] showed that in their
study of 68 patients who underwent a transsacral fusion, rectal perforation occurred in 2%
of the study population. It is important to note
that one of the patients who developed rectal
injury in the previously mentioned study had
preexisting risk factors (prior abdominal surgeries, pelvic inflammatory disease, and undisclosed diverticulitis) making her susceptible to
bowel injury.
426
G. Majeed and F. Asgarzadie
Strategies for Avoidance of Complications
Detailed preoperative evaluation should be performed on all patients being considered for the
trans-sacral approach. Preexisting risk factors
that may compromise the access route through
the pre-sacral space or cause adhesions of the
bowel to the sacrum such as Crohn’s disease,
ulcerative colitis, and previous pelvic or bowel
surgery, prior radiation treatment to the sacral
and/or pre-sacral contents should be identified.
A midline sacral trajectory should be identified
which would allow for a relatively clear pathway
toward the L5–S1 disc space avoiding intra-abdominal and neurovascular structures. Preoperative
MRI of the lumbosacral spine with images that
include the tip of the coccyx should be carefully
evaluated to determine the patient’s suitability for
surgery. While advancing the dissecting tool, AP
and lateral fluoroscopy should constantly be utilized to ensure proper midline trajectory.
Conclusion
We believe that the trans-sacral approach is a
viable option for fusion across the lumbosacral
spine and is especially useful for patients with
lumbosacral pseudoarthrosis as well as Grade 1
or 2 spondylolisthesis. In conjunction with posterior stabilization techniques, the trans-sacral
approach offers a muscle-sparing circumferential
fusion construct at L5–S1 and effectively
decreases range of motion in axial torsion, lateral
bending, and flexion-extension. Patient selection
and perioperative planning are extremely important for the success of this surgery and for minimizing the risk of complications.
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Sacroiliac Joint Fusion
Sharon C. Yson, Jonathan N. Sembrano,
and David W. Polly Jr.
Introduction
The sacroiliac joint (SIJ) is a complex joint that is
mobile and innervated and transmits significant
loads and degenerates with aging. Its range of
motion is reportedly small with just 2.5° of rotation and less than a millimeter of translation [1].
The exact pattern of innervation is debated.
Hilton’s law suggests that any nerve crossing a
joint may innervate that joint. In the case of the
SIJ, there are many possibilities, both dorsal and
ventral. There are pain receptors within the joint
as well [2–4]. Load transmission from the trunk
to the lower extremity occurs through the sacroiliac joint. As with all other diarthrodial joints,
the SIJ can and does develop degenerative joint
changes that may or may not be symptomatic.
Approximately 15% of low back pain can be
attributed to SIJ pathology [5]. There is a wide
spectrum of treatment available. This ranges
from benign neglect to active physical therapy,
passive manual therapy, use of a sacroiliac belt,
injections, radiofrequency ablation, and surgical
32
fusion. The role of imaging to diagnose SIJ pain
is unclear. Typically it is used to rule out tumors
or infections and, perhaps more importantly, to
rule out spinal or hip problems. There is great
overlap in pain perception between the sacroiliac
joint, hip, and lumbar spine [5] (Fig. 32.1).
Therefore, lumbar spine and hip imaging should
be strongly considered prior to committing to a
diagnosis of SIJ pain. MRI may be useful in the
workup for inflammatory arthritides (e.g., ankylosing spondylitis) [6].
The burden of disease for SIJ pain is high, perhaps even more disabling than hip and knee
osteoarthritis requiring total joint replacement,
spinal stenosis requiring decompression, and
degenerative spondylolisthesis requiring surgical
treatment [7]. In addition, chronic nonsurgical
management is likewise expensive. There is no
compelling data that if left untreated, SIJ pain
and disability will resolve. The purpose of this
chapter is to review the diagnostic protocol to
determine when patients have symptomatic SIJ
disease, specific indications for surgery, and
technical points regarding surgical options and
how to reduce complications.
S.C. Yson, MD (*) • J.N. Sembrano, MD
D.W. Polly Jr., MD
Department of Orthopaedic Surgery, University of
Minnesota, 2450 Riverside Ave S R200, Minneapolis,
MN 55454, USA
e-mail: scyson@umn.edu; sembr001@umn.edu;
pollydw@umn.edu
© Springer International Publishing AG 2017
L.T. Holly, P.A. Anderson (eds.), Essentials of Spinal Stabilization,
DOI 10.1007/978-3-319-59713-3_32
Indications and Patient Selection
The best algorithm to determine if the SIJ is a
pain generator involves physical exam and diagnostic injections. There are six provocative tests
commonly used. Reproduction of usual pain is a
429
430
S.C. Yson et al.
positive sign. On applicable tests, these should be
done on both sides: (1) distraction test, (2) compression test, (3) flexion abduction external rotation (FABER) test, (4) thigh thrust test, (5) sacral
thrust test, and (6) Gaenslen’s test (see Figs. 32.2,
32.3, 32.4, 32.5, 32.6, and 32.7).
Multiple studies have shown that if three or
more of these provocative maneuvers are positive, there is an 82–94% probability that pain is
coming from the SIJ [8–10]. Additional useful
Fig. 32.1 A pelvis Ferguson view of a patient who initially complained of low back pain. She eventually underwent lumbosacral fusion, sacroiliac joint fusion, and hip
arthroplasty. This highlights the difficulty of determining
the pain generator for some patients who come to clinic
for low back pain
tests include the Fortin finger sign (if pain is
localized enough that patient can point to it with
a finger and if this area is at or around the posterior superior iliac spine [PSIS]) and tenderness
over the PSIS.
Intra-articular sacroiliac injection with an
anesthetic agent is the currently accepted gold
standard for confirming a diagnosis of SIJ pain if
suspected based on physical exam. Based on
recent studies, it is generally accepted that >50%
reduction of pain after a local anesthetic injection
is indicative of sacroiliac joint dysfunction [11,
12]. Cases with obvious spinal or hip joint etiol-
ogy of their pain based on examination and imaging studies do not need to undergo an SIJ injection.
Furthermore, those with pain localization above
the anatomic L5 level, pinpoint midline pain (e.g.,
tailbone pain), diffuse body pain, or zero positive
provocative test results likewise are not recommended to undergo an injection, as the likelihood
of SIJ pain is very low, and a false- positive injection response may only lead to unnecessary and
unsuccessful interventions. If surgery is contemplated, a second or confirmatory injection may be
considered, especially if there is still some doubt
as to the diagnosis or if the first injection response
was not convincingly positive. The authors generally aim for at least two positive injections prior to
recommending surgery.
Fig. 32.2 Distraction
(gapping) test. This is
performed with the
patient supine while the
examiner, with arms
crossed, places hands
over ASIS. Force is
applied laterally and
posteriorly over both
contact areas
32 Sacroiliac Joint Fusion
Fig. 32.3 Compression
(approximation) test.
Best done with patient
on side-lying position
with the affected joint
up. Examiner stands
behind the patient, puts
both hands over the iliac
crest, and applies a
downward force to stress
the posterior sacroiliac
ligaments
Fig. 32.4 Flexion
abduction external
rotation (FABER) test.
Patient is positioned
supine while examiner
flexes, abducts, and
externally rotates the hip
to bring the foot over the
contralateral knee.
Examiner then exerts a
downward force on
medial ipsilateral knee
431
An important step when evaluating SIJ pain is
to evaluate other potentially painful structures.
Ruling out the hip joint is done by physical exam
and imaging. The most sensitive physical exam
maneuver is probably loaded internal rotation.
Although hip pain is usually felt anteriorly in the
groin, a small number of hip patients will present
with primary buttock pain which can be confused
with SIJ-mediated pain. Femoroacetabular
impingement (FAI) may be reproduced by pas-
sive flexion, adduction, and internal rotation (hip
impingement sign) and may be helpful to identify
labral tears or bony impingement. Groin pain on
resisted active hip flexion (Stinchfield test) may
signal intra-articular hip pathology. Clear radiographic joint loss or findings suggestive of bony
impingement (i.e., pistol grip deformity of proximal femur, crossover sign of acetabulum) on a
pelvis AP radiograph also are suggestive. The
definitive test to rule out hip pathology is an