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27 Lumbar Disc Arthroplasty
Fig. 27.1 (a) The Charite artificial disc. (b) Anteroposterior radiograph of Charitie disc placed at L4-L5. (c)
Postoperative lateral radiograph at L4-L5 of Charitie artificial disc
359
Fig. 27.2 (a) ProDisc-L artificial disc. (b) Activ-L artificial disc
preservation in the lumbar spine and limitation of
Indications and Patient Selection
adjacent segment degeneration (ASD) has been
supported in the literature. The systematic review
of ASD which demonstrated a rate of 14% in
lumbar fusion revealed a rate of only 1% (7/595
patients across 4 studies) in TDR with an approximate average follow-up of 10 years [9].
There are currently only two FDA-approved
lumbar artificial discs (ProDisc-L, DePuy Synthes;
Activ-L, Aesculap) that are marketed and available
in the United States. Lumbar TDR is used primarily to treat discogenic (i.e., axial, mechanical) LBP
[
8]. Given the controversy surrounding the surgi-
cal treatment of DDD in general, many insurance
carriers do not provide coverage for fusion or
L-TDR which has affected the utilization of lumbar arthroplasty devices [
7, 18].
The ideal indications for the treatment of DDD
with L-TDR include relatively young patient
(ideally age 18–60 years) suffering mechanical
LBP (pain exacerbated by activity and somewhat
relieved with rest) and imaging (generally MRI)
revealing an isolated degenerative, desiccated,
and spondylotic disc with little or no facet disease. The patient should have failed a minimum
of 6 months of nonoperative treatment. Clinically,
the evaluation and medical therapies utilized in
working up a patient for consideration of L-TDR
are similar to that of any other lumbar surgery.
The surgeon must focus on the details of the pain
itself (location, symmetry, timing, radiation,
exacerbating and ameliorating factors, etc.).
360
T. Atkins et al.
Beyond a mandatory thorough neurologic exam,
specific attention must be given to range of
motion, posture, and gait [
also been concern with using lumbar disc arthroplasty in multilevel disease. It has been the experience of these authors that multilevel patients
can do well. In a study by Hannibal et al., they
compared one-level and two-level ProDisc
arthroplasty patients. They found no statistically
significant difference in disability, functional, or
satisfaction scores between the two groups [
There are two categories of contraindications:
(1) painful conditions not corrected by the
implant (central stenosis, facet arthropathy, +/−
foraminal stenosis, herniated nucleus pulposus
with radiculopathy) and (2) conditions that may
destabilize the spine (scoliosis, spondylolisthesis, spondylolysis, compromise of the posterior
elements, osteoporosis T-score < −1.0) [19].
Although facet disease is a strong relative contraindication for this surgery, many do not consider
foraminal stenosis a contraindication. The disc
space increases with the prosthesis which often
causes indirect decompression of the foramen
[19]. For patients with the aforementioned contraindications, fusion procedures remain the gold
standard.
3, 7, 18, 19]. There has
20].
Preoperative Considerations and Contraindications
The evaluation of a patient with low back pain
should be thorough and systematic. As with any
musculoskeletal pathology, the evaluation should
begin with a comprehensive history and physical
exam. It is important to ask the patient when they
experience the pain and what aggravates/alleviates the symptoms. Is the pain worse with flexing
the low back or extending it? Are there radicular
symptoms which radiate down the legs or is this
isolated to the low back? What other therapies
have they attempted? Many patients will have
already tried exercise (yoga, home stretching,
etc.) or even formal physical therapy.
It is important to assess the type of pain and
the length of pain when assessing a new patient.
Approximately 80–90% of low back pain resolves
after 12 weeks with no invasive therapy required
[21]. It was initially believed that resting and limiting range of motion was the best treatment of
acute low back pain. Hagen et al. conducted a
Cochrane review of all clinical trials comparing
rest vs early active motion for the treatment of
low back pain [22]. The review showed that there
was a decreased level of pain and increased functional level in the early motion group. It is therefore advisable to begin flexibility and strength
training in the acute period of low back pain.
Formal physical therapy which focuses on
strengthening core muscle groups has been
shown to improve discogenic back pain [23]. In
addition to therapy, nonsteroidal antiinflammatory medications have also been shown
to help alleviate symptoms. Some patients have
already tried corticosteroid injections, and it is
important to understand where these were placed
in the spine and what level of relief they provided. There are many other non-spine pathologies that can cause a similar type of pain. It is
important to ask questions which would help rule
out these other causes. Some of the more common conditions that can cause such pain include
Crohn’s disease, abdominal aortic aneurysm,
nephrolithiasis, pancreatic disease, ovarian
pathology, and tumors. In our practice patients
also get evaluated by a rheumatologist to rule out
inflammatory arthropathy such as rheumatoid
arthritis, psoriatic arthritis, and Lyme arthritis. If
the pain is not well explained by the spine, make
sure your patient is receiving the appropriate
work-up for these other conditions.
The next step in evaluating these patients is a
physical exam. The initial examination should
include inspection of the back to look for any
obvious deformity or overlying skin conditions.
A standard neurologic exam should be performed
to assess for strength and sensation in all extremities. Unlike facet arthropathy which causes low
back pain with extension, discogenic back pain
typically causes pain with flexion. Also, in this
population the straight leg raise is negative. In
most patients, the pain is reproducible with low
back palpation. They also frequently have
decreased range of motion as well as an antalgic
gait. It is vital to have the patients stand and point
27 Lumbar Disc Arthroplasty
361
to the location of their pain. Waddell signs and
other psychological overlay components of the
history should also be defined.
Radiographic evaluation should include plain
radiographs of the lumbar spine, with a strong
recommendation to obtain standing scoliosis
films, as well as CT of the lumbar spine. These
will serve to help identify degenerative levels but
more importantly will rule out other confounding
pathologies such as spondylolisthesis, significant
facet disease, ankylosing spondylitis, Baastrup
syndrome, sagittal imbalance, or scoliotic deformity. These bony images will also help to identify patients that are likely to have osteoporosis
who might warrant further investigation with
DEXA scan. Lumbar MRI is the key imaging
modality for identifying the pathology that is best
suited for treatment with L-TDR. A degenerative
disc (most frequently at L4-L5, L5-S1) can be
identified by a loss of height relative to other disc
levels, a loss of T2 hyperintense signal (desiccation of the nucleus pulposus), annular defects,
and Modic changes in the surrounding endplates
including endplate changes on T1/T2 and especially STIR signal changes. MRI will also allow
the surgeon to rule out other pathologies not well
suited to treatment by TDR including: disc herniations in areas difficult to assess via an anterior
approach, facet arthropathy, clinically significant
central and lateral recess stenosis, or less common pathologies such as neoplastic, infectious,
or intradural processes [
7, 19].
Despite the many advantages of advanced
imaging described above, it is often difficult to
assess if the pathology seen on imaging is truly
symptomatic or if the main generator of pain is
elsewhere. Boden obtained an MRI in a large
cohort of subjects that had no back pain symptoms
[
4]. Of the patients <60 years old, 20% had pathol-
ogy read by blinded neuroradiologists. In the
60+-year-old group, 57% were read as having
spine pathology. Similarly, a study by Borenstein
et al. showed that incidental spine pathology found
on MRI in asymptomatic patients was not predictive of low back pain at 7-year follow-up [
24].
Unfortunately, when it comes to the spine,
often the severity of the pathology as seen on classical imaging (MRI, CT, etc.) does not correlate
with the severity of symptoms. This is particularly
true when it comes to discogenic pain. It would
therefore be useful to have a way to assess the
level of pain associated with the pathology seen
on imaging.
Provocative discography is an example of
functional imaging that has been used to help
correlate prior imaging with symptoms but
remains a controversial study in the diagnosis of
symptomatic DDD [
2, 25]. During discography
individual discs are pressurized using a needle
inserted under fluoroscopic guidance and a saline,
radiopaque dye combination. If the low back pain
is reproduced with this exam, then this may indicate that this particular disc is causing all or a
portion of the low back symptoms. The utility of
this modality is controversial. A study by
Carragee et al. seeking to evaluate the validity of
provocative discography in diagnosing true discogenic pain could only establish a positive predictive value of 50–60% and postulated that
discography may actually accelerate degenerative changes in the disc [25]. In a prospective
study Derby et al. performed discograms on a
large cohort of patients with significant disc herniation (Grade III on the Dallas Discogram scale)
[26]. One group had low back pain prior to the
study and one group did not. In the group with no
back pain prior to the study, 100% of the patients
had a negative or pain-free response to discography. In the symptomatic group, 52% of patients
had a negative discogram despite having clinical
back pain. Interestingly, this study also showed
that the positive discogram group had lower pain
tolerance than the other groups which could certainly be a confounder. In addition, it has been
shown in this study, as well as in prior studies,
that there is less of a correlation between low
back pain and lower grade tears (Grades 1 and 2)
which is why only Grade 3 tears were ultimately
considered. Despite the conflicting evidence on
the utility of this diagnostic test, many surgeons
still use it as part of a multifaceted approach to
assessing low back pain.
Patients who have undergone prior discectomy at the pathologic level remain candidates
for L-TDR; however, previous (failed) fusion at
the level in question is a contraindication. Patients
362
T. Atkins et al.
with inadequate bone quality (osteopenia with a
DEXA T-score between −1.5 and −2.0 should be
considered a relative contraindication, while a
T-score less than −2.5 is an absolute contraindication) are at significant risk for implant subsidence or displacement. Similar to any anterior
spinal approach, there are other relative contraindications related to practical or anatomic limitations often best left to the discretion of the
approach surgeon. These include but are not limited to morbid obesity, pregnancy, multiple prior
abdominal surgeries, certain abnormalities of the
genitourinary system, and abdominal aortic or
iliac aneurysm [3, 18, 19].
Surgical Technique
Appropriate patient preparation prior to surgery
is imperative. The patient is given a prescription
for two doses of magnesium citrate for bowel
preparation 1.5 days prior to surgery. Thirty-six
hours prior to surgery, the patient drinks the first
dose and is started on a clear liquid diet. The second dose is taken 12 h prior to surgery. For male
patients they are given the option of sperm donation prior to surgery.
Under general anesthesia the patient is positioned supine on a radiolucent operating table
taking routine care to protect and pad all pressure
points. A Foley catheter is required to decompress the urinary bladder to optimize the working
corridor. Ureter stents are placed in patients with
a history of prior abdominal surgery or in patients
who have only one kidney for whatever reason.
They are also routinely placed in patients undergoing replacements from L1 to L3 given the
proximity of the ureters to the operative field.
The surgeon should be careful not to position the
patient in too much extension as this can lead to
postoperative facet irritation syndrome.
Preoperatively, pulse oximeters are placed on
bilateral great toes. If a discrepancy between these
devices occurs during the surgery, the retractors are
temporarily released allowing the left lower extremity to again be fully perfused. Neuromonitoring is
not routinely used in our practice, but in more complex patients, it can be considered.
Anteroposterior (AP) and lateral fluoroscopy
are utilized to identify the level of the replacement as well as the optimal angle of approach.
The goal is for the spinous processes to be equidistant from the medial wall of each pedicle, in
other words, eliminating all torsional rotation of
the spine. Fine adjustments to the patient’s position are made using rolled blue towels or inflatable pads.
The lateral view is then obtained to determine
the appropriate vertebral levels aiding in the positioning of the incision. Once the positioning is
complete and the level is determined, the abdominal and pelvic area are prepped and draped in the
normal sterile fashion. We feel that the iliac wing
should be prepped into the field so that, in the
unlikely event that the arthroplasty must be abandoned, the iliac crest can be used as autologous
bone graft for fusion.
In most circumstances, and certainly in upper
lumbar or multilevel surgery, an access vascular
surgery is used. This reduces operative time and
reduces the amount of retraction time on the great
vessels. The skin incision and approach are best
decided by the approach surgeon (typically a
general or vascular surgeon). Options include a
midline or para-midline vertical incision for
transperitoneal or anterior mini-open retroperitoneal approach (more common). For L5-S1 a
transverse incision may be utilized. A left-sided
approach is most common given the greater
safety and ease in mobilizing the aorta as opposed
to the inferior vena cava or iliac veins. However,
right-sided approach may be considered for
males when done at L5-S1 to avoid disruption of
the superior hypogastric plexus and potential
resultant retrograde ejaculation.
Because of the downward slope of the L5-S1
vertebra, a more distal incision is required to
accommodate the necessary angle. In general the
L4-L5 disc is within a few centimeters of the
umbilicus. The incision is carried down to the
rectus sheath. The left rectus sheath is incised in
line with the incision exposing the medial aspect
of the left rectus abdominal muscle. The edge of
this muscle belly is lifted to expose the dorsal
fascia and arcuate line being careful to preserve
the inferior epigastric vessels. This layer is
27 Lumbar Disc Arthroplasty
363
incised revealing the peritoneum. This is the
plane that will be utilized for this surgery.
Sweeping along this plane toward the left, retroperitoneal fat will be observed, and eventually
the left psoas muscle will be identified
(Fig. 27.3a). The genitofemoral nerve can be
identified on the psoas lying just medial to the
common iliac artery. The iliac vein is dorsal to
the artery. All soft tissue structures should be
retracted medially. The middle sacral veins
should be ligated prior to addressing the disc
space. If the level desired is proximal to the L5S1 disc space, then the great vessels must be
mobilized by bluntly developing a plane between
the psoas and iliac vessels. In this approach the
iliolumbar vein must be identified and ligated
before mobilizing the great vessels.
Once the anterior spine has been reached, the
adjacent visceral and vascular structures are
safely mobilized and retracted (Fig. 27.3b). The
correct spinal level is confirmed by lateral fluoroscopy. The midline must be meticulously identified by anatomic landmarks and AP fluoroscopy.
The surgeon can either make a Bovie mark, or a
small osteotome can be used to make a superficial indentation. A wide annulotomy is performed. This is followed by near-total discectomy
using standard technique of curettes, pituitary,
and Kerrison rongeurs (Fig. 27.3c). The discectomy is facilitated by interbody distractors to
open the disc space as well as ultimate resection
of the posterior annulus and posterior longitudinal ligament. Special attention is given to removal
of the cartilaginous endplates while maintaining
the integrity of the bony endplates. Any posterior
osteophytes or extruded disc material should be
removed. Following discectomy, only the lateral
annulus should remain fully intact bilaterally.
The posterior annulus should be resected to aid in
disc space mobilization. The posterior longitudinal ligament does not need to be resected except
in circumstances requiring removal of extruded
disc material. Retained lateral disc material is at
risk of displacement into the foramen with placement of the device and should be thoroughly
removed.
Using AP and lateral fluoroscopy, as well as
tactile feel, the disc space is measured for height,
Fig. 27.3 (a) Intraoperative image showing mobilization
of the retroperitoneal space below the umbilicus. (b)
Exposure at the L4-L5 disc space. There is wide exposure
from the left to right side. The aorta (A) and left common
iliac vessel (CI) is protected. (c) Complete discectomy has
been performed from left to right side. (d) Placement of a
Charite artificial disc at L4-L5. (e) Final in situ position of
the Charite artificial disc
364
T. Atkins et al.
degree of lordosis, and footprint (depending on
the specifics of the device in use). Each device
has its own nuanced surgical technique but typically involves the following steps. The disc space
is sized and then trialed, followed by midline keel
cutting (if necessary for the device in use) and
ultimately placement of the device itself
(Fig. 27.3d–e). Once the implants are impacted
into place, the alignment of the spine should
again be confirmed with intraoperative fluoroscopy. Again, strict adherence to midline placement is an absolute necessity for best device
function. Ideal AP position of the device on lateral fluoroscopy places the device’s center of
rotation approximately 1–2 mm posterior to the
sagittal midline of the vertebral body. The integrity of the vertebral bodies should be assessed as
fractures can occur during insertion. If any fractures are observed or there are any other concerns
regarding the stability of the implants or bony
structures, then the implant should be removed
and an interbody fusion should be performed.
For multilevel surgery, the most distal disc
space is typically addressed first, and then one
works proximally to allow for collinear alignment of the spine. In multilevel surgery, if there is
concern that the implant may not be able to be
placed after the adjacent levels are complete, then
trial implants should be used first to assure the
ability to place all implants. Once all levels are
mobilized and trialed, the hardware can again be
inserted starting most distally and working proximally to assure optimal alignment.
All soft tissue structures, including the sympathetic chain, great vessels, ureters, and retroperitoneal structures, should be thoroughly
investigated for any signs of iatrogenic injury. All
soft tissue bleeding should be controlled by electrocautery, and any bony bleeding should be controlled with bone wax. This is critically important
to minimize the risk of postoperative retroperitoneal hematoma formation. Occasionally, epidural
bleeding is induced, usually from distraction, and
it should be controlled by applying a small
amount of Surgiflo (Ethicon, Somerville, NJ
USA) hemostatic agent or an equivalent product.
The lower extremity pulses should be reevaluated
immediately prior to the end of the case.
The wound is then irrigated thoroughly and
closed in routine fashion. A Gore-Tex patch may
be placed over the anterior annulotomy to provide a dissection plane for revision exposure if
reoperation proves necessary.
Illustrative Cases
Case 1
History
The patient is a 45-year-old female who presents
to the clinic for progressively severe mechanical
lower back pain which is exacerbated by physical
activity and relieved by rest. She has a history of
right microdiscectomy at L5-S1 2 year prior to
presentation. The patient has undergone maximal
nonsurgical management including physical therapy, epidural steroid injections, and selective
nerve root block. Despite this, her pain remains
intolerable even on a regimen of chronic narcotic
therapy centered on fentanyl patches.
Physical Examination
Physical examination reveals healthy-appearing
female with appropriate appearance for age and a
BMI of 26. Neurologic exam revealed normal
motor, sensory, and reflexes of the lower extremity. Her gait is normal. She has slight restriction
in forward flexion at the waist. Her lower back
reveals a well-healed paramedian scar from her
microdiscectomy and very mild tenderness to
deep palpation of the lower back symmetrically
just off midline.
Imaging
Imaging includes MRI of the lumbar spine
without contrast which demonstrates her previous laminotomy defect, without any evidence
of recurrent or residual disc herniation at L5-S1
(Fig. 27.4a). There is, however, a broad-based
disc bulge at L4-L5 not resulting in any foraminal or central stenosis. Both L4-L5 and L5-S1
disc levels appear degenerative owing to mild
loss of height as well as loss of T2 hyperintense signal within the nucleus pulposus.
Provocative discography is performed reveal-
27 Lumbar Disc Arthroplasty
Fig. 27.4 (a) Sagittal
T2 MRI showing no
recurrent disc
degeneration and disc
degeneration at L4-L5
and L5-S1. (b)
Anteroposterior
discography at L4-L5
and L5-S1 revealing disc
degeneration at L4-L5
and L5-S1. Provocative
pain response was
positive at both levels
but negative at L3-L4
that served as a control
level. (c) Lateral
discography. L4-L5 and
L5-S1 show abnormal
degeneration, while
L3-L4 has normal
morphology. (d)
Postoperative lateral
radiograph following
L4-L5 and L5-S1
Charite disc replacement
365
ing mild/moderate annular degeneration at
L5-S1 and a posterior annular tear at L4-L5
(Fig. 27.4b, c). Reproduction of the patient’s
pain with injection is concordant at L4-L5 and
L5-S1 with L3-L4 serving as a negative control
(Fig. 27.4b, c).
Treatment
Following appropriate explanation of associated
risks and benefits, the patient elects to proceed
with (off-label indication) two-level Charite total
disc replacement at L4-L5 and L5-S1 (Fig. 27.4d).
Surgery is performed with the assistance of a vascular surgeon for anterior access. There are no
intraoperative complications. Estimated blood
loss is 150 mL. Total operating room time is 2 h
and 55 min. The patient undergoes routine postoperative care on a neurosurgical floor and is discharged to home in good condition on
postoperative day 4.
Outcome
The patient returns to the clinic for routine postoperative follow-up at 6 and 12 weeks, as well as
6, 12, and 24 months following her date of surgery. She reports an excellent functional recovery
with significant diminution of pain. By 24 months
she is off all narcotic medications and has
increased her activity level. She reports that she is
regularly jogging and lifting weights without
limitation. Upright AP and lateral and flexion/
extension radiographs at 24 months post-op show
good disc placement with maintenance of normal
lumbar vertebral motion (Fig. 27.4d).
Case 2
History
This patient was a 33-year-old female who first
presented to the clinic with low back pain. She
366
T. Atkins et al.
worked as a manual laborer which required heavy
lifting and a significant amount of bending and
twisting. Over the last several years, the pain had
intensified such that it was becoming difficult to
work. The pain was primarily in her lower back,
but also was present in her buttock and upper
thighs. She denied any weakness or difficulty
with coordination in either lower extremity. She
had failed physical therapy and epidural corticosteroid injection.
Physical Examination
The physical examination was unremarkable. No
Waddell signs were present and she was neurologically intact.
Imaging
The MRI showed disc disease at L3-L4, L4-L5,
and L5-S1 (Fig. 27.5a, b). In addition to the MRI,
discography was performed to assess for the
presence of discogenic pain. The exam was positive for pathology at L4-L5 and L5-S1.
Treatment
Ultimately, it is the combination of history, physical exam, and all imaging studies that drives the
decision to operate and at what levels. Given this
patient’s overall picture, it was determined to perform a three-level lumbar TDR on L3-S1. The
procedure proceeded with no intraoperative complications, and the implants were placed in good
alignment (Fig.
the procedure well and was discharged home on
postoperative day 3.
27.5c, d). The patient tolerated
Outcome
Over the next several months, her incisions
healed well and the incisional pain improved.
She had significant improvement in her low back
pain which was present preoperatively. After a
period of activity restriction, she was able to get
back to working which meant bending over to lift
objects which she tolerated well. This operation
not only provided pain relief and a stable mechanical solution to her problem, but it also allowed
for the range of motion necessary for a young
patient to get back to her physically demanding
livelihood. This example case demonstrates that
in the right patient, TDR in the lumbar spine can
be highly efficacious and allows patients to return
to an acceptable activity level.
Technical Pearls
• Be sure the patient’s spine is in neutral posi-
tion on the operative table at the start of the
case. An inflatable pillow may be placed in the
low lumbar region and utilized to gain better
access to a collapsed disc space.
• True AP and lateral fluoroscopic views are a
necessity as the midline and AP position of
the replacement disc is more crucial to success
than when using standard interbody fusion
cages.
• Take special care to preserve autonomic
nerves in dissection around L5-S1 to avoid the
complication of retrograde ejaculation in male
patients by minimizing use of Bovie electro-
cautery in the prevertebral space.
• Do not violate the bony endplates at the dis-
cectomy site; to do so increases the risk of
device subsidence and ultimate failure.
• Be sure all lateral disc material except for a
thin rim of annulus is removed prior to placing
distractors, trials, or the graft in order to avoid
displacing fragments into the foramina.
• Complete the near-total discectomy in a piece-
meal fashion, checking for retained disc mate-
rial in between each of the sizing/trialing/keel
cutting steps.
• Resecting the posterior longitudinal ligament
will allow for the best mobilizing of the disc
space and creation of the anatomic height and
lordotic curve. Parallel distractors help expe-
dite this process.
• The lateral annulus should not be released for
mobilization purposes.
• Proper sizing of the replacement disc which
maximizes endplate coverage will benefit the
maintenance of lordosis and proper vertebral
motion, as well as minimize subsidence and
may help avoid heterotopic ossification or off-
midline placement.
• Avoid “overstuffing” the disc space with an
oversized disc as this can limit motion. When
27 Lumbar Disc Arthroplasty
367
Fig. 27.5 (a) T1-weighted axial image from a preopera-
tive MRI showing minimal central stenosis. (b)
T2-weighted sagittal image from a preoperative MRI
showing minimal disc herniation or canal stenosis at all
levels being considered for TDR. (c) Postoperative antero-
choosing between two heights, generally choose
the smaller size.
In some cases, coronal realignment is required
which can add a level of complexity to the case.
For these situations we suggest the use of a
3.5 mm AO reconstruction plate (DePuy Synthes
Spine, Raynham, Massachusetts). A ball-spike
posterior radiograph following L3-L4, L4-L5, and L5-S1
ProDisc-L placement. The discs are well aligned in the
midline and the overall coronal balance is excellent. (d)
Postoperative lateral radiograph following L3-L4, L4-L5,
and L5-S1 ProDisc-L placement showing good restoration of disc height and sagittal alignment
pusher can be used to manually obtain the appropriate coronal alignment, and the plate can be
applied over the anterolateral vertebral bodies to
secure the reduction. At this point, the endplates
can be modified with a chisel in such a way to
allow for appropriate alignment with the use of
the implant alone. Through a process of trial and
error using the trial implants, the bony anatomy
368
T. Atkins et al.
can be modified to assure adequate coronal (and
also sagittal) alignment. Once this is achieved,
the final implant is inserted and the 3.5 mm plate
is removed. Vertebral body pin distractors can
also be used to achieve coronal and sagittal alignment. However, in our experience, these devices
do not always reproduce anatomic alignment
which is ultimately the goal. If these devices are
to be used, caution should be taken to assure anatomic alignment with the help of intraoperative
fluoroscopy.
Complications and Strategies for Avoidance
Generic complications of any spine operation
also exist for L-TDR including neurologic
injury, hematoma formation due to inadequate
hemostasis, and postoperative infection.
Furthermore, L-TDR entails the risks and complications unique to anterior spine approaches:
postoperative ileus, abdominal visceral or vascular injury including injury to iliac vessels, and
injury to the autonomic nerves of the superior
hypogastric plexus which can result in retrograde ejaculation in males [3, 12]. The most
feared and dangerous complications include
major vascular injury. The risk of this complication is low, particularly if an experienced access
surgeon is utilized. The ureters are also at risk
with this exposure, so liberal use of ureter stents
should be employed. The exposure becomes
significantly more difficult in patients with a
BMI of 35 or greater. In our own practice we do
not offer TDR surgery to these patients. Surgery
should not be performed on individuals with
dermatological issues that affect the abdominal
skin such as eczema, psoriasis, or intertrigo.
Intraoperative complications during discectomy and implant placement can be minimized
by meticulous technique. Particular care should
be take when placing and tensioning distractor
devices in the interspace. Using parallel distractors with the largest surface area possible can
help minimize this risk. Fluoroscopy can be helpful in preventing these iatrogenic problems. If
they are encountered, the TDR should be aban-
doned and a fusion should be performed.
Although rare, occasionally an intraoperative
durotomy is encountered. Depending on the size
and location, a primary repair can be attempted
or a sealant can be utilized. Given our experience,
we recommend not doing a primary repair in
most cases. Usually the use of a sealant and the
application of a fat or muscle patch is enough to
control the leak, which will resolve over time.
Normal durotomy care should be carried out
postoperatively. Some patients have a significant
concavity to their endplates. This is important to
identify since keeled devices, even large keels, do
not work. In these cases spiked implants can be
utilized to overcome this problem.
Unique risks associated with L-TDR include
subsidence of the disc replacement into the vertebral body, dislocation of the device from the
disc space, or undesired ankylosis and fusion
across the disc space (heterotopic ossification).
The former two complications can be minimized
with proper surgical technique. The primary
means to avoid these complications include preservation of the bony endplates and proper sizing
and positioning of the replacement disc. A disc
that is too short risks dislocation, whereas a disc
that has too small of a footprint risks either dislocation or subsidence. Additionally, the risk of
subsidence increases significantly in patients
with osteopenia or osteoporosis. In any patient in
whom these conditions are suspected, such as
female over the age of 50 or those with a positive
family history, a preoperative DEXA scan is
required. If subsidence occurs and the implant
appears stable, then revision surgery is not
always necessary. A brace to limit mobility
should be worn for 6–8 weeks in these patients.
If there is a fracture through the vertebral body
or the implant is extruded anteriorly, then a revision surgery is usually indicated.
The complication of failure to maintain
motion across the disc space due to fusion is
largely an issue of patient selection. Patients at
risk for undesired fusion or ankylosis are those
older than 60 or those with more diffuse multilevel
degenerative/spondylotic change in the lumbar
spine.