Anterior Cervical Discectomy with Fusion
I. SURGICAL INDICATIONS
The decision to perform anterior cervical discectomy and fusion is based on
three factors: Patient symptoms, findings on physical exam, and
radiographic abnormalities.
A. PATIENT SYMPTOMS
The patient's symptoms are generally categorized into three patterns of
pain. Axial pain is that which occurs along the spine and the overlying
musculature. Referred pain is that which occurs along the scapular and
shoulder region. Radicular pain is that which extends partially or completely
along the length of the arm.
Axial pain is generally vague and is typically similar irrespective of the
underlying problem. Referred pain into the shoulder or scapular region is
also generally vaguely defined. These patterns of pain may be due to
irritability of small nerves along the surface and it is difficult to differentiate
these patterns of pain from soft tissue inflammation such as ligamentous
injuries or tendonitis. Instability of joints or vertebrae in the cervical spine
can also produce similar patterns of referred pain. radicular pain typically
conforms to a specific nerve root distribution or course. radicular pain is
most easily identified as specifically related to nerve root impingement and,
as such, is generally most accurately correlated with a specific abnormality
within the spine.
Ideally, symptoms of radicular pain are clearly present and are greater than
patterns of referred or axial pain.
B. PHYSICAL FINDINGS
Physical findings can generally be divided into three groups: Limitation of
motion, the presence of tenderness, and neurological deficits. While limited
range of motion in the cervical spine is frequently present, it is a very
nonspecific finding and does not reflect any particular abnormality, which
would suggest an indication for performance of an anterior cervical
discectomy fusion. Tenderness is also frequently present and may be
diffusely noted along the musculature, joints, and can be present over the
supraclavicular fossa in patients with complaints of cervical nerve root
irritation.
Compression signs, such as the Spurlings maneuver, are another method of
eliciting tenderness in the patient. These techniques involve compressing the
affected nerve and recreating the symptomatic pain. Radiating pain in the
arms of cervical origin has to be differentiated from compression at the wrist
(carpal tunnel syndrome) and elbow (cubital tunnel syndrome).
neurological deficits are the most specific indicator of nerve root
compression. neurological deficits include loss of a specific reflex, loss of
sensation in a specific area correlating with a particular nerve, or loss of
strength in a muscle or muscles conforming to a particular nerve.
In general, patients are usually not considered for surgical treatment until a
period of six to eight weeks of non-operative care has been attempted. This
treatment would generally include restricted activity, physical therapy or
chiropractic treatment, anti-inflammatory medication, narcotic analgesics
and muscle relaxants, and possibly epidural cortisone injections. Several
factors may indicate a need for more expeditious surgical treatment. These
factors would include incapacitating unremitting pain, progression of a
neurological deficits posing a potential functional impairment, or development
of signs consistent with spinal cord compression or dysfunction.
C. RADIOGRAPHIC ABNORMALITIES
Indications for surgical treatment
radiographically would include the presence of a herniated
discs on MRI, CT
scan or myelography. The
herniated discs should
be of sufficient size that it is placing pressure on a specific nerve
root or the spinal cord. Ideally, the herniation should be compressing upon
a nerve root, which correlates
with the patient's pattern of pain and physical findings. Multiple studies have
indicated that asymptomatic patients may have herniations noted on MRI and CT scan. As such, it is common that patients will be noted to have incidental herniations
present. The presence of a herniated discs should only be considered the source
of a patient's pain when it correlates with the clinical symptoms and physical
findings.
A second indication for surgical
treatment radiographically is the presence of stenosis on MRI,
CT scan, or myelography.
Stenosis is simply narrowing
of the canal resulting in pressure on the spinal cord or nerve
root. Cervical stenosis
is generally the result of degenerative change within the disc, joints, and thickening
of the ligaments. Stenosis may
occur centrally, compressing on the spinal cord, or in the foramina resulting
in compression on a nerve root.
As in the case of herniations, stenosis
should only be considered significant when the affected nerve correlates with
the patient's complaints and physical findings.
II. SURGICAL TECHNIQUE
Anterior cervical discectomy and fusion is best performed using
microsurgical techniques. The advantage of microsurgical techniques include
reduction of tissue trauma, decrease in operative recovery, a reduction of
post surgical scarring, and greater precision with reduced risk of neurological
injury.
Anterior cervical discectomy
and fusion can be performed at one or multiple levels. The patient is positioned
supine. Usually, a 1 to 2-inch oblique incision is made on the left or right,
preferably in a skin crease. The orientation and length of the incision may vary
dependent on the number of levels addressed. Several layers of tissue are bluntly
and sharply separated, including the subcutaneous fat, platysma, deep cervical
fascia, pretracheal fascia, and pre-vertebral fascia. Vital structures such as
the carotid sheath, trachea, and esophagus are retracted. The appropriate level
is marked and verified on x-ray.
The periosteum and longus colli muscles are elevated and retracted. Distraction
pins are inserted into the vertebra above and below the disc space. The disc is
incised and removed along with the cartilage covering the surface of the vertebra
.
The beak off prominent bone along the anterior lower vertebral margin is removed
and saved for later use as bone graft within the cage 
.
This provides better visibility for removal of the remaining desk and spinal canal
decompression. The remainder of the disc and cartilage is removed to the posterior
longitudinal ligament 
.
The ligaments are resected transversely entering the spinal canal 
.
The spinal canal is decompressed by removal off those and ligaments along the
upper and lower vertebra from the left to right foramen 
.
Once decompression of the spinal cord and nerve roots has been achieved, the
depth of the vertebra is measured 
. Fusion is performed by placement of either
bone graft or an implant into the disk space. The graft may be obtained from
a cadaver, allograft, or may be taken from the patient's pelvis, autograft.
With the disk space fully distracted, the graft is impacted into position.
The graft is selected and contour to fit precisely within the disk space. The
bone graft reconstitutes the normal disc height and enlarges the height of
the foramen.
Alternatively, implants, either cylindrical cages or rectangular interbody
spacers can be inserted to achieve fusion. These implants require inclusion
of bone graft, bone substitutes, or bone inducing agents to achieve fusion.
These implants are manufactured from titanium or synthetic material such as
PEEK.
Cervical cages are inserted in the following manner. Following decompression,
the disc is distracted and a guide sleeve inserted for preparation and insertion
of the cage 
.
The disc is then reamed
and tapped through the guide sleeve creating a channel . The cage, filled with
bone graft, is inserted into the channel. The procedure may be repeated at one
or more levels as indicated through the same incision and exposure.
A plate is positioned over the vertebra and two screws are inserted through the
plate into each vertebra to be fused. A locking mechanism is engaged on the plate
securing the screws 
.
A lateral x-ray verifies the position of the cage, plate and screws as well as
the spinal alignment
. Plating is commonly used to increase the rate of fusion
and maintain stability in multiple level fusions, cervical instability, and placement
of a strut graft. Plating may also obviate the need for bracing in one and two
level fusions.
Prior to wound closure all bleeding is meticulously controlled. The platysma
is approximated with suture. The subcutaneous tissue is approximated and sutured
as well. The skin may be sutured, stapled, or closed by adhesives or Steri
strips.
III. POST-OPERATIVE COURSE
Patients are generally maintained
on bedrest for several hours following the surgical procedure. They are typically
advanced to ambulation on the day of surgery. Patients are usually advanced to
a regular diet on a gradual basis and IV fluids are discontinued when they are
able to accept liquids. Most patients are able to swallow liquids with minimal
difficulty but may have trouble with solids for a short time. IV antibiotics are
usually given pre-operatively and for 24 hours post-operatively. If the patient
is independent with ambulation, able to tolerate a regular diet, afebrile and
able to void they are generally discharged on the day following surgery. Patients
may occasionally be discharged on the day of surgery. Patients are generally placed
in a rigid collar after surgery. The collar can be removed in most cases for showering
but should be worn at all times otherwise. Use of a collar may be optional in
cases where instrumentation is used. Patients are advised at the time of discharge
to avoid vigorous activities. Patients are typically prescribed pain medication
to be taken by mouth as needed and occasionally anti-inflammatory medication for
residual nerve root swelling and irritation.
Patients are generally advised to refrain from getting the incision wet for
three days post-operatively. At that time they may shower. It is generally
advisable to avoid submerging the incision in a tub or pool for at least one
week.
Follow-up examinations are typically conducted at one week, one month,
three months, 6 months and 1 year post-operatively.
At approximately 2 months post-operatively patients are referred for
physical therapy and the collar discontinued. This includes a graduated
course of upper extremity and cervical flexibility, strengthening, and
instructions on body mechanics and postural alignment. Patients are
generally advised to increase their recreational and daily activities
commensurate with their progress at physical therapy. Fusion will typically
take 4-6 months to develop and patients should restrict activity during this
time.
IV. OUTCOMES
A. BENEFITS
Appropriately selected patients, as previously described, can generally
expect a high probability of improvement, if not relief, of neck and arm pain
following anterior cervical discectomy and fusion. Review of the last 1,000
surgical cases included 180 anterior cervical fusions. 151 of these cases
were performed at one or two levels for neck and radicular arm symptoms
related to either herniated disc or spondylosis with stenosis. 88 of these
procedures resulted in successful outcomes. Failures included development
of a pseduoarthrosis in 7 patients. Revision of the pseudoarthrosis resulted
in a 71% success rate. Failures included 2 patients experiencing partial
displacement of their graft. Surgical revision resulted in successful outcomes
in both patients.
13 procedures were performed for fracture, instability, or stenosis with
myelography at three or more levels. Successful outcomes occurred in 100%
of these patients as determined by development of a stable fusion, and
stabilization or improvement of neurological function.
Revision of pseudoarthrosis, following surgery performed elsewhere, was
performed in 4 patients. Successful outcomes occurred in 50%.
The remaining three procedures included discectomy and corpectomy for
infection, subsequent revision of a displaced strut graft and revision of a
plate failure.
Although relief of arm or radicular
pain is common, relief of neck pain to the same degree is less predictable.
Although the majority of patients can expect improvement or substantial relief
of pain, some patients may experience continued pain of a substantial degree.
This may be due to the presence of other degenerative changes or milder injuries.
B. COMPLICATIONS
Operative risks include infection, bleeding, neurological injury,
pseudoathrosis and late instability.
Post-operative infection rates for surgical procedures on a national basis are
approximately 1 to 2%. No infections have occurred following anterior
cervical discectomy and fusion in our experience.
Bleeding associated with anterior cervical discectomy and fusion is almost
without exception negligible. Although the potential exists for substantial
blood loss if the carotid artery or jugular vein were injured, this event is
fortunately exceedingly rare. There have been no instances of significant
blood loss in anterior cervical discectomy fusion procedures. Blood loss
during surgical treatment of acute fractures has been greater although no
surgery has resulted in a need for blood transfusion.
Neurological injury is an unlikely operative complication. Most frequently,
post-operative neurological deficits were present pre-operatively.
Occasionally, sensory changes may be noted post-operatively due to
swelling of affected nerve roots. These symptoms are typically temporary
and usually resolve within a matter of several days or weeks. There have
been no procedures resulting in progression of an existing deficit or
development of a new deficit in our experience. Two patients experienced
Homer's Syndrome, which resolved over several months.
Pseudoarthrosis is the most common complication associated with anterior
cervical discectomy and fusion. The exact incidence varies within the
literature, however it is generally felt that the likelihood of pseudoarthrosis
is approximately 10% per level fused in non-instrumented cases.
Fortunately, not all patients are symptomatic and as such no further
treatment may be necessary. In the remaining patients recurring or
persistent symptoms associated with absence of fusion, disc space
narrowing, or increased mobility at the operative level may indicate a need
for revision of the fusion. In our experience pseudoarthrosis has been
documented in 7 patients of 180 procedures performed, 5%.
Pseudoarthrosis occurred equally between patients fused with allograft and
autograph. Pseudoarthrosis was equal among non-instrumented fusions, six
of 133, 4.5%, and instrumented fusions one of 47, 4.2%. However,
instrumentation was performed more frequently in multiple level procedures,
cervical instability, and pseudoarthrosis revision; all procedures associated
with a higher pseudoarthrosis rate. The equal failure rates would indicate a
significant benefit resulting from use of cervical instrumentation.
Infrequently, a graft may shift, requiring repositioning. Two allograft's
displaced partially requiring revision, 1.5%. Instrumentation failure
occurred in three patients, 6%, although fusion appeared to develop
following loss of distraction after plate failure. Two patients experienced
fracture of bone surrounding plate screws resulting in loss of stability and
requiring revision.
The total re-operation rate for all complications, pseudoarthrosis, instrument
failure or graft displacement was 12 of 180 procedures, 6.7%.