(Laminectomy
L4-L5)
By
Paul E. Montano
Introduction
Despite a wealth of research
concerning risk factors, pathophysiology, prognostic indicators, and treatment
methods, low back pain continues to be an epidemic, yet poorly understood,
problem. The lifetime prevalence of low back pain is estimated at 50% to 85%. Low
back pain is the most common cause of disability in persons younger than 45 to
65 years of age. Although only 15% to 20% of those affected actually seek medical
attention. Doctors perform 3 common surgeries on the back to relieve nerve root
compression. They are diskectomy, Laminectomy and Fusion decompression. They
often are done in combination with each other. Laminectomy is removal of part
of the lamina above and below an affected nerve. Laminectomy is the removal of
most of the bony arch, or lamina, or a vertebra.
Considerations
Indications:
Relapse of low back pain may or
may not be associated with leg pain. Patients who present with low back and leg
pain quite frequently recall earlier episodes of post-exertional pain limited to the low back. This pattern has led many clinicians to
attribute the initial episode of localized low back pain to early degeneration
of the annulus fibrosus. Another indication for surgery is a progressive loss
of nerve function. For example, you may lose a certain reflex and later begin
to lose strength gradually. If the deficit is severe, you cannot bend a knee or
move a foot, with possible drop foot. Many people may not regain full nerve
function. Early decompression is advised.
Contraindications:
Poor health of patient, chest
pain, extreme obesity, high white blood cell count, infection. Laminectomy
approach for routine thoracic disk herniations should be avoided. Spinal fusion is an option, usually with
patients with demonstrable postramatic, postsurgical, rheumatoid, or neoplastic
instability. Unless there are major neurologic deficit that indicates a need
for immediate surgery, the patient is usually managed conservatively. The
patient is placed on bed rest in a bed with a firm mattress and bed boards.
Tests:
X-ray examination may reveal degeneration
changes, such as disc space narrowing and osteophytosis or Spondylolysis
(usually occurs at the L4-S1 level, but can occur more proximally in the lumbar
spine). CT scans define the bony anatomy in one or two planes are able to
demonstrate the lumbar subarachnoid space well, may demonstrate encroachment of
the canal by hypertrophied lamina, osteophytes, facets, or pedicles, and can
provide excellent visualization of the vertebral canal. MRI scanning with its mulitplanar
imaging capability is currently the preferred modality for establishing a
diagnosis and excluding other conditions. MRI depicts soft tissues including
the cauda equina, spinal cord, ligaments, epidural fat, subarachnoid space, and
intervertebral discs with great details.
Incisions:
Most effective incision the surgeon can use will be when the
patient is placed in kneeling position. The abdomen is free and the
intraabdominal pressure reduced, minimizing epidural venous bleeding. The
patient may also be placed prone on a Wilson frame. With this position there is
some more pressure on the abdomen and the epidural veins are more prominent.
The patient may also be put into lateral position but this causes the surgeon
to have more difficulty in the disc space. With all of these positions the
surgeon will still make the same incision. The incision runs from the center of
the spinous processes of the vertebrae between which the affected disc lies. In
an average sized individual a 3 to 6 cm incision is usually adequate.
Other
Considerations:
Complications of Laminectomy
for disc removal include recurrence of pain due to reherniation of residual
disc fragments or scar formation involving the nerve roots; damage of nerve
roots, resulting in neurologic deficit; tear of the dura, with resulting dural
leak of CSF; and penetration of the anterior annulus during discectomy, with
damage to the great vessels lying anterior to the spine. A lumbar laminectomy emphasizes a minimum of
soft tissue dissection, which enhances early ambulating and recovery. Accurate
placement of the incision is required. Three techniques are employed to place
the incision directly over the affected disc. Notation of the level of the
iliac crest on the plain lumbar spine films, palpation of the last spinous
process, which is S1, and a preoperative lateral Xray with skin marker and or
spinal needle help aid the surgeon in the correct level the surgeon needs to do
surgery.
Incisional
Anatomy:
The incision is made with the
patient in prone position and the incision is over the area of concern midline
incision. An incision about 1 to 1½ inches in length with #10 blade, beginning
at the superior spinous process and extending to the interspinous space. The
dissection is carried down to the spinous process. The deep fascia is incised
off midline to minimize postoperative pain. The adjacent lamina are then
exposed with subperiosteal dissection. The laminar arches are exposed laterally
to the articular facets.
Surgical
Anatomy
The lumbar spine: The lumbar vertebrae are connected by a number
of ligaments. The anterior longitudinal ligament is attached closely to the
anterior surface of the vertebral bodies but less tightly to the intervertebral
bodies. The anterior and posterior ligaments serve as a source of axial
stability to the spine. The ligamentum flavum is attached to the undersurface
of adjacent lamina. This is an elastic structure, which serves to restrict
flexion of the spine. Other spinal ligaments include the intertransverse
ligament, which joins the transverse processes of adjacent vertebrae, and the
interspinous ligaments, which connect the spinous processes. The intervertebral
discs serve as an articulation between adjacent vertebral bodies. The disc has
two basic functions. The first is to act as a shock absorber and the second is
to serve as a site of limited motion between adjacent vertebrae. The lumbar
disc consists of three parts. The cartilaginous plate covers the bone of
adjacent vertebrae and acts as a barrier between the nucleus pulposus and the
adjacent vertebral bodies. The nucleus pulposus is the semigelatinous center of
the disc, which serves as a shock absorber. The annulus fibrosis is a circular
fibrous structure that restrains the lateral forces produced by the compressed
nucleus. The annulus is stronger anteriorly than posteriorly and it is not as
well attached to the posterior ligament as to the anterior. The canal is formed
by the neural arch dorsally and the vertebral bodies and discs ventrally. Nerve
roots leave the canal at each level of the lumbar spine. Normally, as each root
leaves the
dural
sac, it crosses the disc space and enters the lateral recess. The posterior
aspect of the
vertebral
body, the adjacent disc, the medial wall of the pedicle, and the superior facet
form this
space.
The root then passes around the pedicle into the neural foramen, where it
leaves the spine. The nerve root and
dorsal root ganglion is approximately 4 to 7mm in diameter.
Blood
Supply:
The arterial supply to the discs and vertebrae
comes from the lumbar arteries, which arise from the aorta. These vessels
supply each vertebra in a segmental fashion. Radicular enter the dura with each
nerve root. A major branch, the artery of Adamkiewicz, supplies the cord and
may enter as low as the L3 nerve root. The venous drainage is derived from the
internal venous plexus located on the floor of the canal. The plexus also
drains the vertebral bodies in a segmental fashion, through the foramina into
the external venous plexus and ultimately, the vena cava.
Nervous
Supply: The 31 pairs of spinal nerves
correspond to the same number of spinal segments, each segment containing one
pair of nerves. There are 8 cervical pairs, 12 thoracic, 5 lumbar, 5 sacral,
and 1 coccygeal. Each spinal nerve has two roots, one dorsal and one ventral.
The dorsal root contains an area of enlargement called the dorsal root
ganglion. Each spinal nerve forms two branches, these are called rami. The
spinal cord ends around L1-L2.
Patient
Preparation
Anesthesia is induced on the
patient while on the stretcher, with the patient in supine position before he
or she is placed on the operating table. A Wilson frame is placed on the
operating room Jackson table prior to 12 patient arriving to room. Following
induction of anesthesia and with the anesthesiologist permission, the patient
is gently rolled over from the stretcher to the table and up onto the Wilson
frame in prone position. This maneuver should always be performed by at least
four staff people. It is essential that the limbs be protected from torsion and
that the head is kept in strict alignment with the trunk during the move. Make
sure male and female parts are not constricted or pinched in anyway. The arm
restraints are placed. The elbows are comfortably bent and padded to prevent
ulnar nerve injury. Rolled towels are place in the axillary regions to protect
the nerve plexuses and to aid in respiration. The frame is padded and flexed to
the proper height. The safety straps lies above the knees. The knees, lower
legs, and feet are well padded. A small drape
will be placed across the buttocks so that prep solution will not pool. The
surgeon will now identify proper disc space of L4-L5 using C-Arm with AP
Lateral view. Surgeon will use skin marker and a non sterile Kocher and mark
appropriate levels. The skin will be prepped with duraprep. This area usually
will consist of shoulder blades down to buttocks and down to sides of patient.
Four sterile blue towels will now be drapped in a figure of four fashion.
Surgeon and surgeon assistant scrub for surgical procedure.
Surgical
Procedure
Incision: With the patient prepped and
draped the incision will be made over the level of L4 and L5. Local can be
injected over incision line. Begin with a midline incision , beginning at the
superior spinous processes and extending to the interspinous space. The
dissection is carried down to the spinous processes. The deep fascia and
paraspinous muscles are incised off midline to minimize postoperative
pain. The surgeon assistant can aid
in cauterizing any bleeders aid in
suction. These are retracted with Cerebellar retractor placed by surgeon or assistant
(open approach). The two adjacent lamina are the exposed with subperiosteal dissection.
The laminar arches are exposed laterally to the articular facets.
Surgery: The surgeon makes a midline incision over the
affected disc and carries it sharply down to the supraspinous ligament. Care is
taken not to damage the epidural veins. The
supraspinous ligament is incised, and the muscles are dissected subperiosteally
from the spines and laminae of the vertebrae. These are retracted with
Cerebellar Self retaining retractor repositioned
by the surgeon or assistant. Then the
surgeon denudes the laminae and ligamentum flavum with a medium sized straight
curette. A small part of the inferior margin of the lamina is removed with a
rongeur. The ligamentum flavum is
grapsed and incised where it fuses with the interspinous ligament, and this flap
is then sharply removed to expose the dura.After necessary amount of the lamina
has been removed the dura and nerve root are carefully retracted medially with
a nerve root retractor by the surgeon or assist, to expose the underlying posterior longitudinal
ligament. The surgeon assistant is responsible for retraction of the nerve root
and to suction when necessary to keep the
field of view clean (be very attentive to staying very still , and out
of the view of surgeon). Use a Fraser suction tip without covering the thumb
hole so the suction isn’t powerful enough to injure the dura. The surgeon will use an 11 blade to incise
the PL ligament over the intervertebral space in a cruciate fashion. Pituitary and
kerrison rongeurs are then used to remove extruded fragments of disc material.
Surgeon and assistant need to take caution and care not to exceed the distance
to the anterior annulus. If using neuro modulation now is the time to
communicate regarding possible stimulation of nerve. Once the extruded disc material has been
removed, the
inner portion of the disc may be removed. Curettes are used in the
intervertebral disc space to remove all remaining fragments of disc material,
kerrison and pituitary rongeurs could also be used at this time. Care must be taken
not to injure the aorta or vena cava, which lie anterior to the vertebral
column. Prior to wound closure, the wound is irrigated free of debris. Care is
taken to search for additional fragments of nucleus pulposus, both inside and
outside the disc space, with possible foraminotomy. Surgeon assist can aid in any residual bleeding with bipolar coagulation and
suction for greater visualization.
Wound
Closure: The paraspinous
muscles and fascia are approximated with 1 Vicryl CT-1 CR/8. The skin is closed by the surgeon assistant with 4.0 monocryl on
PS-2. The wound is dressed with durmabond and ½ steri tapes and covered with
telfa and 4X4 dressing X1 large tegaderm. The patient is rolled onto the
patient bed with the aid of four people. The patient is taken to recovery room
and monitored for pain and postoperative bleeding. The patient should be able
to demonstrate the movement of feet and hands after surgery.
Paul E. Montano SA-C
Disclaimer: Paul E. Montano,
does not claim or present himself to be, a Medical Doctor or Surgeon MD. Paul
E. Montano is in fact a Surgical Assistant Certified SA-C. Article was written
for a brief simplified example of a common surgical spine procedure. The actual
surgical procedure is much more complex and advanced in nature.
