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CHAPTER 36/MINIMALLY INVASIVE PROCEDURES FOR ANTERIOR COLUMN FUSION AND RECONSTRUCTION / 353
TABLE 36-1. Minimally invasive access surgery for lumbar
fusion and disc reconstruction
Laparoscopic anterior lumbar interbody fusion (22,23)
Percutaneous posterolateral interbody fusion (12)
Mini-open microsurgical posterolateral fusion (13)
Mini-anterior lumbar interbody fusion (24)
Mini-open total disc replacement (26)
GENERAL PRINCIPLES
Disc degeneration may lead to clinical symptoms of
pain (“discogenic” low back pain). However, low back
pain due to disc degeneration is usually “multifactorial”.
Whereas young patients may present with pure discogenic back pain, the majority of patients present with a
mixture of discogenic, arthrogenic, and musculoligamentous symptoms. Surgical procedures to deal with these
symptoms have common goals: the excision or elimination of pain source(s), the elimination of biomechanical
pain generating mechanisms, the restoration and retention of the physiologic se gmental curvature, as w ell as the
restoration of disc and foraminal height, especially in
cases with lateral recess or foraminal stenosis. There is no
doubt that these goals can be most reliably achieved by
360° or 270° fusion of one or several lumbar segments.
Using this technique, all potential pain sources (disc, end
plates, facet joints, facet joint capsules) are excised.
Pathologic load patterns due to loss in disc height (“vertical instability”) as well as macroinstabilities (e.g.,
degenerative spondylolisthesis) are eliminated by the
fusion (Fig. 36-1). Disturbances of lumbar cur vature in
the sagittal (kyphosis, hyperlordosis) as well as frontal
(degenerative lumbar scoliosis, segmental tilt) plane can
be reduced and maintained by posterior instrumentation.
Disc height and foraminal height can be restored in cases
with root symptoms associated with low back pain. Thus
spinal fusion is the only “curative” salvage procedure to
treat degenerative low back pain.
TABLE 36-2. Lumbar spine ar throplasty procedures
Total disc replacement
SB Charite disc (30)
Prodisc (26,31)
Acroflex (32)
Nucleus replacement
Mechanical
Prosthetic disc nucleus (33)
Spiral nucleoplasty (34)
Biological
Autologeous disc chondrocyte transplantation
(ADCT) (35)
Posterior Augmentation
Graf ligaments (36)
Dynesys (37)
Wallis (38)
A
B
FIG. 36-1. Lateral X-ray of the lumbar spine. A: Preoperative–degenerative spondylolisthesis grade I. B: Postopera-
tive–restoration of physiologic curvature with reduction and
270° lumbar fusion.
LUMBAR FUSION
The controversial discussion on the role of lumbar
fusion is the result of an obvious discrepancy betw een the
technical achievement of the surgical goals (discussed
previously) and the clinical outcome. The majority of
undesired side effects, complications, and poor outcome
is determined or influenced by the surgical approach to
the target area (4,5).
The main prognostic factors for outcome of lumbar
fusion surgery are patient selection and surgical technique (7,10,11).
354 /SECTION V/SPECIFIC CLINICAL ENTITIES
Patient Selection
The reader is referred elsewhere in the text (Chapters
28–35, 39, 45) to information on the current “state-ofthe-art” treatment of degenerative lo w back pain. There is
consensus that spinal fusion in degenerative conditions of
the lumbar spine should be the last therapeutic step when
noninvasive or semi-invasive conservative measures have
failed. However, there is neither consensus on the identification of lumbar levels to be fused nor on the type of
fusion (7,8,11,12). The most frequently used techniques
are listed in Table 36-3.
Less Invasive Techniques for Lumbar Fusion
Microsurgical Posterolateral Fusion (13)
Posterolateral fusion has been the most widespread
fusion technique for the past 25 years. It has been performed without instrumentation (11,14) or with instrumention (15), with varying clinical success and fusion
rates. Decortication of laminae, facet joints, and transverse
processes is followed by the application of autograft or
allograft bone “posterolaterally” in order to achiev e a solid
bone bridge between adjacent segments. It is the easiest
technique in fusion surgery, however, it also is the most
traumatizing technique because of damage to the paravertebral muscles during the approach (16–18) (Fig. 36-2).
Unacceptably high pseudoarthrosis rates have limited
the popularity of this fusion among spine surgeons in
Europe (6,11,19).
In 1998 McCulloch described a microsurgical modification of the “classic” posterolateral/intertransverse lumbar fusion (13). Based on his experience with microsurgical discectomy, McCulloch described a minimally
invasive paramedian approach to the intertransverse area.
Soft-tissue dissection is reduced to a minimum. Preservation of a “soft tissue envelope” (paraspinal muscles, intertransverse ligament and muscle) is presumed to provide a
vascularized bed for autologous bone graft. Decortication
of the facet joints and the transverse processes is performed with high-speed drills. The use of autologous
bone graft is recommended.
The clinical results described by McCulloch revealed
the advantages of this minimal invasive technique: In a
series of 22 patients with single-level degenerative disc
disease, microsurgical posterolateral fusion was per-
TABLE 36-3. Spinal fusion techniques
Posterolateral (intertransverse) 180° posterior
TLIF/PLIF 270° posterior
Percutaneous PLIF 180° anterior
ALIF 180° anterior
Posterior/ALIF 270° posterior/anterior
ALIF, anterior lumbar interbody fusion; PLIF, posterior lumbar interbody fusion; TLIF, transforaminal lumbar interbody
fusion.
FIG. 36-2. X-ray lumbar spine, frontal view. Shaded area is
necessary for muscle retraction for posterolateral L4-5 fusion.
formed. Follow-up after 2 years showed good and excellent results in 86.4% of the patients. The average hospital
stay was less than 3 da ys, the a v erage intraoperati ve b lood
loss less than 300 cc. There w as only one pseudoarthrosis
(13). In a similar series of 22 patients with degenerative
spondylolisthesis and acquired spinal stenosis, the rate of
satisfactory results was 91%. The pseudoarthrosis rate
however was 14% (13).
Although this technique has not become very popular,
it seems to be a reasonable alternative to the “classic”
posterolateral type of fusion performed through the
Wiltse approach.
Minimal Invasive Anterior Approaches for Interbody
Fusion
In 1990 Obenchain first described a laparoscopic approach to the L5/S1 disc (20). This “ke y” publication triggered the development of a variety of less invasive anterior accesses to the lumbar spine that dominated the last
decade. Laparoscopic surgery was associated with a variety of technical pitfalls and hazards and has never
reached the status of a “routine-procedure” (21–23).
However, the need for less invasive anterior approaches
was obvious, since 360° or 270° fusion achieves the highest fusion rates of all techniques (5,10,24). In 1997, I
described two “mini-open” access techniques to the lum-
CHAPTER 36/MINIMALLY INVASIVE PROCEDURES FOR ANTERIOR COLUMN FUSION AND RECONSTRUCTION / 355
bar levels for anterior interbody fusion (24). They were
based on the application of microsurgical philosophy to
the well-known standard anterior approaches.
Lateral Retroperitoneal Access to L2-L5
Monosegmental as well as multisegmental anterior
fusion can be performed through a standard anterior approach to the lumbar levels L2-L5. With this technique,
the abdominal muscle layers are cut, irrespective of their
orientation, and the lumbar segment(s) are approached
anterior to the psoas muscle (25).
Microsur gical (Mini-Open) Access
The mini-open anterior lumbar interbody fusion
(ALIF) technique (mini-ALIF) has been described extensively (9,24), so only the basic principles are repeated
here:
The patient is placed in a right lateral position (Fig. 36-
3). The approach is from the left side. The operating tab le
is tilted slightly posteriorly (20° to 40°) which facilitates
the access to the lumbar spine through a small skin incision, even in very obese patients, since all abdominal
contents and fat tissue “fall-away” anterior from the surgical field. The retroperitoneal cavity is entered through
a 4 cm skin incision that is directed obliquely parallel to
the direction of the external oblique abdominal muscle.
The use of a bright head lamp (Xenon light source) and
optical aids (surgical microscope, loupes) is recommended in special situations (e.g., obese patients, reoperation). The muscle layers (external oblique, internal
oblique, transversus abdominus) are exposed by a blunt,
muscle-splitting technique. The peritoneal sac is bluntly
dissected from the psoas muscle and the disc space is
exposed anterior and medial to the psoas muscle. The
anterior circumference of the disc space is exposed from
the midline to approximately 2 cm lateral to the insertion
of the anterior longitudinal ligament. This requires a
small splitting (1 to 1.5 cm) of the medial insertions of
the psoas. The anterolateral circumference of the disc
space is exposed bluntly and kept free from surrounding
tissue by insertion of frame-type retractors that are
anchored in the adjacent vertebral bodies or by an external frame holder.
Fusion Technique
The type of anterior fusion performed is optional once
the target area is exposed. All types of fusion techniques
are possible (autologous bone graft, vertical cages with
bank bone or autologous bone, femoral ring grafts, standalone ALIF cages, etc.) (Fig. 36-4A, B).
A
FIG. 36-3. Positioning of an obese patient for mini-open
retroperitoneal approach to L2-L5.
B
FIG. 36-4. A: A 360° instrumental fusion at L5-S1 with autologous bone graft. B: Both anterior approaches were done
through a 6 cm skin incision at L4-5 with vertical titanium
cage.
356 /SECTION V/SPECIFIC CLINICAL ENTITIES
Midline Retroperitoneal or Transperitoneal Access to
the Lumbosacral Junction
The conventional approach to the lumbosacral junction
is either through a midline longitudinal or transverse skin
incision using a transperitoneal route or through a pararectal retroperitoneal approach. The patient is placed in a
supine neutral position with the surgeon standing either
on the left or right side of the patient
Mini-Open Access to L5-S1
Mini-open access to L5-S1 is performed through a 4
cm transverse or longitudinal skin incision in the midline
and a mini-laparotomy. Patient positioning has been modified with the patient in a supine position with the legs
abducted so that the surgeon can stand between the
patient’s legs.
Thus, the visual axis of the surgeon is parallel to the
L5-S1 intervertebral space. The level of the skin incision
can be marked in two different ways: in slim patients, the
abdominal wall is slightly indented with a blunt metal
marker and a lateral fluoroscopy is used to sho w the position of the marker over the L5-S1 disc space. In obese
patients, the orientation and anterior border of the lumbosacral junction is identified by lateral fluoroscopy and
a “corridor line” is drawn from there onto the abdomen.
The transverse skin incision is placed 2 cm caudad to the
corridor line (8).
The rectus sheath is exposed and split in the midline.
L5-S1 can be approached through a retroperitoneal route
either from the left or from the right side. To mobilize and
shift the peritoneal sac, it is necessary to incise the posterior rectus sheath. In obese patients and in patients with
previous abdominal surgery, a transperitoneal route is
recommended. Dissection of the prevertebral part of the
peritoneum should generally be from the right to the left.
Electrocautery should be avoided to minimize the risk of
injury to the superior hypogastric plexus and retrograde
ejaculation in men. The anterior circumference of L5-S1
is exposed between the common iliac veins. The median
sacral vessels need to be either ligated or coagulated with
bipolar electrocautery and dissected. L5-S1 is exposed
with the help of special retractors. The options for fusion
are the same as in the levels L2-L5.
Minimal Invasive Midline Accesses for Total Disc
Replacement
Total disc replacement for the treatment of painful
degenerated lumbar disc is an alternative to lumbar
fusion (26,27). The principles of minimal invasive access
surgery can be applied to this new technology (26,28).
However, total disc replacement requires a midline
approach to all lumbar segments. This mandates a modification of the approach to the L4-5 and more proximal
levels. The surgical approach technique for L4-5, L3-4,
and L2-3 is described subsequently.
Positioning of the patient and localization of the level
are performed as previously described. Care must be
taken to place the patient in a neutral supine position
without hyperextension to prevent hyperlordosis that
complicates implantation of the artif icial disc.
L4-5 Level
A small transverse skin incision is centered over L4-5
or placed slightly left of the midline (28). The rectus
sheath is exposed and can be split either longitudinally in
the midline or transversely on the left side. In slim
patients, midline splitting of the sheath can provide sufficient exposure to begin the retroperitoneal dissection
from left to right (discussed previously). In obese patients, it is advisable to mobilize the rectus muscle circumferentially and begin the retroperitoneal dissection
lateral to the muscle belly after incision of the posterior
rectus sheath. It is important to f irst mobilize the common iliac artery and to identify the iliolumbar vein
beneath the psoas muscle. Mobilization of the common
iliac artery is performed with finger dissection and small
peanut swabs. The iliolumbar vein must be identified, ligated, and cut before the common iliac vein is mobilized
tow ard the midline (9,28). Once the vessels are mobilized
toward the midline, the disc space can be palpated with
the tip of the index finger. The segmental vessels of L4 on
the left side then need to be identified and ligated if necessary (Fig. 36-5).
Thus, the anterior portion of L4-5 can be exposed and
the retractor system can be inserted. Sharp retractor
blades or pins should not be used since they could cause
vascular injury (28,29).
Results
Results of mini-open anterior fusion have already been
described (5,8,9). The combination of mini-open anterior
fusion with pedicle instrumentation produces excellent
and good results in 75% to 85% of the patients (5,8). The
pseudoarthrosis rate is 3% and the rate of complications
due to the anterior approach is 5.2%. Perioperative morbidity is extremely low with clinical results that seem to
be comparable to conventional fusion techniques.
L3-4 Level
The approach to L3-4 is performed the same way as for
L4-5 except that a curved longitudinal incision is recommended if the L3-4 disc is at the level of the umbilicus.
Usually the iliolumbar vein does not need to be identified, but the segmental vessels at L3 and L4 on the left
must be ligated before the aorta and the vena cava are
mobilized from left to right. Rarely, the L3-4 disc can be
approached between the aorta and the vena cava. In this
CHAPTER 36/MINIMALLY INVASIVE PROCEDURES FOR ANTERIOR COLUMN FUSION AND RECONSTRUCTION / 357
FIG. 36-6. The Prodisc implant (Spine Solutions, Inc., New
York, NY), modular design: two metal end plates, ultra–highmolecular-weight polyethylene inlay.
FIG. 36-5. Vessels to be identified for the midline approach
at L4-5 as seen on three-dimensional computed tomography–angiography (l.il.v., left iliolumbar vein; l.c.i.v., left common iliac vein; xx, left segmental vessels L4).
case, the segmental vein(s) on the left and the segmental
artery(s) on the right side must be ligated (26).
L2-3 Level
The approach to L2-3 for total disc replacement is
rarely necessary since symptomatic disc degeneration at
this segment is unusual. The skin incision is located at the
level of or cranial to the umbilicus. A transperitoneal
approach is recommended since retroperitoneal dissection is difficult. Care must be taken to avoid dissection
through the mesenterium. The mesentery and small intestine are pushed cranially to the right and the prevertebral
peritoneum is split in the midline. Care must be taken to
avoid the renal artery.
Minimal Invasive Implantation of the Prodisc Implant
36-7A, B). This trial implant deter mines the size, height,
and degree of lordosis of the final implant. Once it is
placed in the correct position, a groove is chiseled in the
adjacent vertebral bodies for the two keels of the implant.
After removal of the trial implant, the end plates of the
modular total disc are implanted, the disc space is distracted, and a polyethylene insert is implanted (Fig. 368A,B).
A
The Prodisc Total Disc (Spine Solutions, Inc., New
York, NY) is the only implant that can be inserted
through the minimal invasive approaches described in
this chapter (Fig. 36-6). Once the anterior circumference
of the disc space is exposed, the midline is marked and
verified through anteroposterior fluoroscopy . A rectangular window is made in the disc space and the anterior
annulus fibrosus is removed. The nucleus and the cartilaginous end plates are carefully removed with curettes.
Preservation of the subchondral bone is of paramount
importance. The trial implant can then be inserted (Fig.
B
FIG. 36-7. A: Tr ial implant to determine size, height, and lordosis angle. B: Lateral X-ray, trial implant in place at L5-S1.
358 /SECTION V/SPECIFIC CLINICAL ENTITIES
A
B
FIG. 36-8. X-ray postoperative lumbar spine. A: Implant in
place (lateral view). B: Skin incision.
CONCLUSION
Minimally invasive surgical approaches for spinal
fusion or reconstruction in degenerative diseases have
been popularized within the last 10 years. Preoperative
planning and modification of surgical strategies with
innovative instruments and implants are key factors for
performing safe and successful surgery. A vascular or
general surgeon is extremely helpful in providing access
to the surgical target area. The main advantages of minimal access surgery are the reduction in perioperative
morbidity and the possibility of early and aggressive
mobilization and rehabilitation of the patient. Although
experience is still limited, disc replacement is a new and
exciting application of less invasive surgical approaches.
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CHAPTER 37
Degenerative Disc Disease: Complications of Surgery
Scott L. Blumenthal and Donna D. Ohnmeiss
Many strategies for the surgical management of symptomatic disc degeneration have been developed. Potential
advantages and disadvantages are associated with each of
them. The development of fusion cages and artificial discs
has brought renewed interest in surgery for symptomatic
degenerative disc disease. The effectiveness of some of
these techniques and devices is still in question. Another
important issue is the safety of these devices and of the
operative techniques required for them. In this chapter we
will focus on the complications associated with lumbar
fusion, particularly interbody fusion, artificial disc replacement, and intradiscal electrothermal therapy (IDET) used in
the treatment of symptomatic disc degeneration. In order to
focus this review on current techniques and instrumentation, the majority of the literature reviewed will cover the
period from approximately 1990 to 2002. We tried to
include information dealing specifically with the treatment
of symptomatic degenerative disc disease; however, many
articles involved a mixed group of diagnoses.
OVERVIEW OF POTENTIAL COMPLICATIONS
With most of the procedures discussed in this chapter,
complications directly related to the surgery may arise
from several sources. The greatest potential for complications is related to technical problems ex ecuting the surgery,
poor implant selection, device failure, and poor patient
selection. Technical problems can be grouped based on the
operative approach used. With anterior lumbar interbody
fusion, the most readily recognized risk is injury to the
great vessels. This may occur by tearing or puncturing one
of the structures with an instrument or during retraction.
Other complications associated with anterior spine surgery
include damage to the sympathetic chain resulting in temporary or permanent sexual dysfunction, urologic problems, or altered sensation in the lower extremities. When
placing devices from the anterior approach, one must be
aware of the depth of the implant to avoid impingement of
neural elements either directly by the device or by pushing
disc tissue into the canal.
Posterior interbody fusion is also associated with
potential significant complications. Injury to neural
structures can result from making direct contact with an
instrument or from retraction. Typically, bone must be
removed from the posterior elements in order to gain
access to the disc space, which has the potential to create
or contribute to instability of the operated spinal segment.
As with the anterior approach, the surgeon must be
acutely a ware of the depth of implants or bone graft since
aggressive insertion of implants or graft can result in significant vascular injury. Other complications associated
with posterior spine surgery include damage to the posterior musculature from dissection and retraction of these
tissues. Also, screws placed posteriorly can penetrate the
cortical bone of the pedicle injuring neural structures.
In surgeries using autogenous iliac crest bone graft,
there are complications related to the donor site. These
include injury to neural or vascular structures, fracture,
infections, and persistent pain.
ANTERIOR APPROACHES TO THE LUMBAR
SPINE
Interest in the anterior approach to the lumbar spine has
increased dramatically in recent years due to the introduction of fusion cages, laparoscopic fusion techniques, and
disc replacement. In this section we will review general
complications as well as complications associated with specific devices implanted using an anterior approach.
Vascular Injuries
The risk of significant vascular complications during
anterior lumbar interbody fusion is related to the proxim-
360
CHAPTER 37/DEGENERATIVE DISC DISEASE: COMPLICATIONS OF SURGERY / 361
ity of the vena cava and aorta to the disc spaces. These
structures are at greatest risk during the exposure of the
disc space, but can also be injured by blunt contact or
retraction during the placement of devices or bone graft.
There is a great deal of individual variation with regard to
the level of the vessel bifurcation that determines the
approach. Surgery can either be above the bifurcation,
below it, or in some cases between the vessels. Weiner at
al. investigated v ariation in v ascular anatom y with respect
to anterior lumbar interbody fusion (1). They reported
that in about 60% of cases, the vascular anatom y w as predictable and the lumbosacral disc could be accessed
below the bifurcation. In 30% of cases, there were minor
variations in vascular anatomy, which did not significantly alter the approach to the spine. In the remaining
10% of cases, a significantly different approach to the
disc was required due to variation in vascular anatomy.
The altered surgical approach inv olved w orking above the
bifurcation. In all of these cases, the operated level was a
functional lumbosacral level above a fixed transitional
vertebra.
One study reported the results of a retrospective revie w
of 105 consecutive cases in which the retroperitoneal
approach was used to gain access to the lumbar spine (2).
These authors reported that the overall incidence of vascular complications was 15.6% (16/105). This included
tears of the common iliac vein (10.5%), the inferior vena
cava (3.8%), and the iliolumbar vein (0.9%). The authors
found that the complication rate was almost twice as
great with the hypogastric paramedian approach as with
the anterolateral approach. The majority of complications
occurred during the surgical exposure. Fortunately, these
complications resulted in only one case of deep vein
thrombosis, and there were no cases of pulmonary
embolism or catastrophic blood loss.
In a detailed review of general surgery complication in
anterior spinal fusion, the rate of vascular injury was
found to be 6.6% (3). In two cases, venous injury
occurred during the exposure of the disc space, and in
one case, the injury occurred during g raft placement. In
all three cases, the problem was addressed intraoperatively with no serious sequelae. The other vascular injury
occurred during the exposure in a case to revise or
remove a malpositioned cage. That injury was attributed
to dense adhesions that had formed after the initial
surgery. There was significant blood loss and the surgery
was abandoned.
The risk of vascular injury was of particular concern as
laparoscopic fusion was being developed. With this procedure, injury to a major vessel has the potential for more
severe consequence since it cannot be repaired directly.
There was concern about whether or not the endoscopic
procedure could be rapidly converted to an open procedure to repair a damaged vessel before the situation
became critical. Tears of vessels have been reported during laparoscopic fusion (4). In the cases requiring con-
version to an open surgery, the vascular injury was
addressed without serious sequelae. It was reported that
among six cases converted to an open procedure due to
iliac vein laceration or excessive bleeding, only one
patient received a blood transfusion. When performing
laparoscopic fusion, one must be acutely a w are of the risk
of vascular injury and have a plan to convert to an open
procedure if needed. The equipment necessary for quick
and safe conversion to an open procedure must be readily
available.
Based on a review of abdominal vascular studies,
Vraney et al. suggested that the L4-5 disc could be
accessed laparoscopically in only approximately onethird of patients (5). The limiting factor was the location
of the bifurcation of the great vessels with respect to the
L4-5 disc space. The risk of vascular complications was
thought to be too great in the remaining cases. However,
Regan et al. reported that by varying the approach to the
disc, to either above the bifurcation, below the bifurcation, or between the vessels, the disc space could be
assessed in all cases and no patient had been denied a
laparoscopic fusion based on the location of the vessel
bifurcation (6).
A rare vascular complication of anterior lumbar interbody fusion is occlusion of the common iliac artery. This
has been discussed in a few case reports (7–10). One case
of aortic thrombosis following anterior-posterior fusion
has been reported (11). The patient’s condition continued
to deteriorate after intensive treatment and she died 8
days after the spine surgery. In such cases, the vascular
occlusion is usually caused by direct pressure of the vascular structures by the retractors. Vascular complications
may be more likely or more severe in patients with risk
factors such as smoking and vascular calcification.
Sexual Dysfunction
Retrograde ejaculation can occur with anterior spine
surgery as a result of injury to the superior hypogastric
plexus which is responsible for closing the bladder neck
during ejaculation. This complication can be permanent; however, it typically resolves in 3 to 6 months
after surgery, although it has been reported to take
longer in some cases. The incidence and outcome of
sexual dysfunction were studied in detail in a series of
41 men who underwent anterior lumbar interbody
fusion using a retroperitoneal approach (12). The
authors reported that 8% of the patients experienced retrograde ejaculation, but none had any alteration in
attaining erection or achieving orgasm. Among the four
patients in that study with retrograde ejaculation, two
were permanent, one could not ejaculate for six months
and had reduced ability to ejaculate thereafter, and the
status of the other patient was unknown. In another
study of complications related to anterior spine surgery,
9.6% of 31 male patients reported sexual dysfunction
362 /SECTION V/SPECIFIC CLINICAL ENTITIES
(two with retrograde ejaculation and one with repor ted
impotence) following anterior spine surgery (3). Although impotence has been reported as a direct complication of anterior spine surgery, it is not very likely (3)
since the parasympathetic plexus, which is responsible
for erection, is located deep within the pelvis and should
not be at risk during anterior spine surgery.
Ureteral Injury
Ureteral injury from blunt trauma can occur during
anterior approaches to the lumbar spine. If not identified
and addressed intraoperativel y, the patient can experience
severe abdominal pain from a large collection of urine in
the abdomen. A few cases of ureteral injury related to
anterior spine surgery have been reported (13–15). Bladder dysfunction from injury to the parasympathetic presacral nerve during the anterior portion of a combined
anterior-posterior fusion has been reported (16). The
patient was treated with self-catheterization and she ultimately regained bladder control in 3 months.
Neural Injury
Injury to the cauda equina or nerve roots may occur
during anterior spinal surgery. This can be the result of
passing instruments too deeply into the disc space, placing devices or bone graft too far posteriorly, by pushing
disc tissue into the canal space, or by stretching the roots
by over-distraction of the disc space.
In a cadaveric study, Taylor et al. investigated the
occurrence of foraminal violation and nerve root impingement related to the use of anteriorly placed interbody fusion cages (17). Although the number of samples
was small, the authors concluded that the occurrence of
foraminal violation or neural impingement was reduced if
a device was placed directl y in the midline. The incidence
of impingement was increased when the devices were
placed 10% off midline, and increased further when the
devices were placed 20% off midline.
Several studies ha v e reported that the lateral placement
of cages can cause disc tissue to be displaced posteriorly,
resulting in nerve root compression (18,19). Patients with
this complication generally complain of severe radicular
pain immediately following surgery. Imaging can sometimes be difficult to interpret due to artifact from the
metal cages. In a nonrandomized study comparing open
to laparoscopic fusion using BAK cages, disc herniation
was the only complication that was more common in the
laparoscopic fusion group, occurring in 2.8% of cases
(4).
Sympathetic sensory changes can occur and may result
in a “warm leg”, temperature variation, dysesthesia, discoloration, or swelling of the leg or foot (3,20). These
patients should be evaluated carefully to rule out possible
arterial complications. If the problem is not vascular, the
altered sensations generally resolve over the course of
several months.
Papastefanou et al. reported two cases of femoral nerve
palsy due to patient positioning during anterior lumbar
interbody fusion (21). The patients’ symptoms resolved
in 3 to 6 months. The authors attributed the injury to the
patients being positioned intraoperatively with the spine
and hip immobilized in a position of maximum stretch of
the psoas muscle, compressing the femoral nerve.
COMPLICATIONS REPORTED IN VARIOUS
ANTERIOR FUSION STUDIES
The reported incidence and types of complications
related to anterior spine surgery vary greatly. This ma y be
due to the different types of procedure performed, the
type of graft or device used , the skill and e xperience le v el
of the spine and access surgeons, the associated patient
comorbidities present, and other factors. Presented herein
is a review of complications reported in some studies of
anterior lumbar spine surgery. The review deals primarily
with publications since 1990 and those involving patients
with symptomatic disc degeneration.
Newman and Grinstead reported a series of 36 patients
undergoing anterior interbody fusion with autogenous
graft specifically for discogenic pain (22). Complications
in their series included one each of pulmonary embolism,
retrograde ejaculation, donor-site wound hematoma, and
graft extrusion. There were no vascular complications,
although 16.7% of patients received a blood transfusion.
Reoperation occurred in 8.3% of patients from extruded
graft, symptomatic pseudoarthrosis, or for disc herniation
above the fusion.
In one of the largest series of anterior lumbar interbody
fusions, Kuslich et al. reported on 591 patients in whom
BAK cages packed with autogenous iliac crest graft were
used as a stand-alone device (23). The data w ere collected
from the multicenter United States Food and Drug
Administration Investigational Device Exemption (FDA
IDE) trial. The incidence of complications reported in
that series included neurologic injury (2.0%), superficial
infection (3.1%), ileus (3.1%), new radicular pain (1.3%),
retrograde ejaculation (4% of males), hematoma/seroma
(1.5%), vessel damage/bleeding (1.7%), atelectasis/pneumonia (1.9%), urologic complications (1.4%), wound
problems (1.2%), phlebitis/pulmonary embolism (0.7%),
fatigue fracture of the S1 vertebral body (1.3%), and
other complications (0.3%). In 0.8% of the study group,
implant migration required reoperation. In an additional
1.5% there was implant migration not requiring reoperation. The authors did not provide data for the total reoperation rate in the patients undergoing anterior fusion
with the cages. There were no cases of device failure,
death, major paralysis, or deep infections. The low complication rate in this series was very impressive, since it
represented the initial experience using this implant.