Spinal Disorders: Fundamentals of Diagnosis and Treatment Part 37 potx

Indications for the posterior approach to the cranio-cervical-thoracic spine C0–T spondylotic radiculopathy cervical fracture/instability spondylotic myelopathy chronic dens fracture

Identify and regularly

check the pulsation

of the carotid artery

level localization The structures at risk during this approach have been listed

above A deleterious pitfall is the risk of unintentionally retracting the carotid artery medially instead of laterally Therefore, the pulse of this artery must be

palpated to ensure that the artery is indeed lateral

The overall risk of operative complications remains small but significant [72]

In 450 cases of anterior cervical discectomy, the rates of recurrent nerve palsy and Horner’s syndrome were 1.3 % and 1.1 %, respectively [9] However, the true rate of nerve root injury based on laryngoscopy is substantially higher (24 %) [34] Apfelbaum suggested monitoring endotracheal tube (ET) cuff pressure and release of the pressure after retractor replacement or repositioning has been used, which enables the ET to be recentered within the larynx [4] The natural

history of a recurrent nerve lesion is benign [34] Complete recovery of vocal

cord function was documented in 26 (93 %) of 28 patients who had undergone a

thyroidectomy [46] Dysphagia is a not uncommon problem after anterior

cal spine surgery Overall the incidence of dysphagia 2 years after anterior cervi-cal spine surgery was 13.6 % based on the analysis of 348 cases [43] Risk factors for long-term dysphagia after anterior cervical spine surgery include gender, revision surgery, and multilevel surgery The use of instrumentation, higher lev-els, or corpectomy versus discectomy did not significantly increase the

preva-lence of dysphagia [43] Vertebral artery injury is a rare (0.3 %) complication in

cervical discectomy [10] However, in a report on 185 corpectomies, the vertebral artery was injured in four patients [18]

Posterior Approach to the Cervical Spine

The anterior and posterior approaches are both frequently used to approach the cervical spine in a variety of disorders [58] However, usually the anterior approach is preferred because of the minimal collateral soft-tissue damage The posterior approach necessitates dissecting the neck muscles, which can be related to persistent postoperative neck pain

Indications

The posterior approach to the cervical spine is predominantly indicated in cases with multisegmental degenerative changes or with craniocervical disorders (Table 2):

Table 2 Indications for the posterior approach to the cranio-cervical-thoracic spine (C0–T)

) spondylotic radiculopathy ) cervical fracture/instability ) spondylotic myelopathy ) chronic dens fractures ) cervical instability in rheumatoid arthritis ) tumors

) multisegmental degenerative changes ) infections ) spinal deformities

Patient Positioning

A Mayfield clamp

is preferred for the headrest/fixation

The positioning of the patient in the prone position is best accomplished using a

Mayfield head clamp ( Fig 3) The clamp is applied before turning the patient into the prone position This fixation avoids pressure sores on the face, which are not infrequent when using other types of headrest (e.g the horseshoe type) We use

a carbon fiber clamp, which allows for anteroposterior imaging The shoulders

Figure 3 Patient positioning for posterior cervical spine surgery

Positioning of the patient with a Mayfield clamp and electrodes on the head for neuromonitoring.

and arms (parallel to the body) are pulled down using nylon tapes to expose the

cervical spine as much as possible A footrest allows the whole table to be tilted

head up, which accommodates the surgical approach

Surgical Exposure

Landmarks for Skin Incision

The landmarks of skin incision are:

) external occipital protuberance

) spinous processes C2–C7

The skin incision is along the midline from the external occipital protuberance

towards caudal depending on the target region When a short level exposure is

attempted, image intensifier control is recommended to avoid unnecessary

detachment of the posterior spinal muscles (Fig 4a)

Superficial Surgical Dissection

After skin incision and splitting of the subcutaneous tissue, the superficial

surgi-cal dissection should first identify the nuchal ligament With a diathermy knife

the muscles are detached subperiosteally from the spinous process The

superfi-cial muscle layer consists of (Fig 4b):

) trapezius muscle

) posterior serratus muscle

) splenius capitis muscle

a b

Figure 4 Surgical anatomy of the posterior cervical approach

aLandmark for skin incision.bSuperficial and intermediate muscle layers.cExposure of the craniocervical junction with osteotomy of the spinous process for osteoligamentous muscle detachment.dSurgical anatomy at the craniocervical junction.

The posterior cervical

exposure can lead

to significant bleeding

The intermediate muscle layer consists of:

) semispinalis capitis muscle After sharp detachment the muscles are pushed laterally as one conglomerate with sponge rolls using a Cobb raspatory Dissection of each muscle layer is unnecessary In some patients, heavy bleeding is encountered which has to be borne in mind when performing this approach Dense packing of the space between the spinous process and the laterally retracted muscles helps to control the bleeding When the spine is exposed the bleeding usually stops, i.e bleeding vessels can easily be identified and coagulated During the superficial dissection

care has to be taken not to injure the greater occipital nerve ( Fig 4b),

necessitat-ing a midline approach

Deep Surgical Dissection

For exposure of the craniocervical junction, it is recommended to osteotomize

with a chisel (or oscillating saw) the muscle insertion of the deep muscle layer from

the spinous process of C2 (Fig 4c) The deep muscle layer consists of cranially:

) rectus capitis posterior major and minor muscle

) oblique capitis inferior muscle

and caudally:

) multifidus muscle

) semispinalis cervicis muscle

The rationale for an osseous detachment is the better refixation of these muscles

to counteract postoperative kyphosis

Exposure of the atlantoaxial joint jeopardizes the 2nd cervical nerve

When exposing the craniocervical junction (Fig 4d), care has to be taken not

to injure the:

) vertebral artery

) second cervical nerve (greater occipital nerve)

) third cervical nerve

The vertebral artery turns around the lateral mass of the atlas from lateral to

medial and disappears into the foramen magnum through the atlanto-occipital

membrane The second cervical nerve exits the spinal canal medial to the facet

joint, crosses that joint posteriorly in a horizontal direction and curves around the

oblique capitis inferior muscle before it runs cranially to innervate the occipital

skin The third cervical nerve exits the foramen and separates the posterior ramus,

which runs medial to the second cervical nerve on its course to the occiput

Wound Closure

In cases in which the insertion of the neck muscles has been detached from the

tip of the spinous process with an osteoligamentous flap, a transosseous suture of

the detached muscle is done with a slowly dissolving suture The wound is closed

with one or two subfascial suction drainages The fascia, subcutaneous tissue and

skin are sutured in separate layers

Pitfalls and Complications

Exposure of C1 can cause vertebral artery injury

The vertebral artery is at risk when a sublaminar wire is passed around the arch of

C1 It is therefore mandatory to start in the midline to subperiosteally liberate the

atlanto-occipital membrane from the bone with a blunt probe before the wire is

passed with a wire passer (Dechamps) During the exposure of the atlantoaxial

joint, the second cervical nerve is endangered because of its horizontal course over

the posterior aspect The craniocervical junction is highly vascularized by a large

venous plexus Blind coagulation may jeopardize the second or third cervical nerve

Right-Sided Thoracotomy

The thoracotomy approach for the treatment of spinal disorders has been

pio-neered by Capener [12] and Hodgson [19, 31, 32] Today, it has become a

stan-If not determined by the

pathology, the right sided

approach is preferred

dard approach for the treatment of thoracic spinal disorders including defor-mity, tumor or infection In deformity surgery, the approach is always on the side of the apex of the curve, i.e a sided thoracotomy is chosen for a right-sided curve In cases in which the spinal pathology does not dictate the side of

the thoracotomy, the right side is preferred because of the contralateral position

of the aorta

Indications

The indication for a thoracotomy is a spinal pathology located between T4 and T10 (Table 3):

Table 3 Indications for a thoracotomy (T4–T11) and thoraco-phrenico-lumbotomy (T9–L5)

) spinal deformities ) thoracic fractures/instabilities ) degenerative disorders ) tumors

) infections

Patient Positioning

The patient is positioned in a left-sided decubitus position on a soft rubber

mat-tress Alternatively, a vacuum mattress can be used which is helpful in large

patients and better stabilizes the patient Both arms are positioned at 90 degrees elevation and flexion of the elbow (Fig 5a, b) The legs are positioned straight with the right leg on top of the left leg We use a foam rubber block with a cavity for the lower leg The right leg can then easily be positioned on top of the block The symphysis and the sacrum are supported by pads to avoid the patient rolling over

Surgical Exposure Landmarks for Skin Incision

Double-check the correct

side of the thoracotomy

A deleterious complication is a wrong side thoracotomy Therefore, it is manda-tory to double-check the side of the thoracotomy at the beginning of the sur-gery

Image intensifier control

optimizes the spinal access

Furthermore, it is of great importance to center the incision over the pathol-ogy and correctly select the target rib or the intercostal space The relationship between the intercostal space and the vertebral level is dependent on how oblique

or horizontal the ribs curve to the sternum (Fig 6a ) As a rule of thumb, the rib

resected determines the highest vertebral level which can be reached (e.g resec-tion of the 7th rib allows T7 to be reached) It best exposes the vertebra two levels below the origin of the resected rib (e.g resection of the 7th rib allows the best exposure of T9) This is crucial when a mini-open exposure is attempted Because

of the variant forms of the ribcage, we recommend checking the correct level with an image intensifier Nothing jeopardizes the success of an operation so much as an inappropriate exposure

Superficial and Intermediate Surgical Dissection

The skin incision ranges from the lateral border of the paraspinous musculature

to the sternocostal junction of the rib which has to be resected After the incision

of the subcutaneous tissue, the latissimus dorsi muscle and the anterior serratus muscle also have to be divided over the course of the target rib with a diathermy

b

Figure 5 Patient positioning for right-sided thoracotomy

aAnterior view.bPosterior view.

knife It is recommended to only partially transect the latissimus dorsi muscle

and lift it off the ribcage with a Hohman retractor (Fig 6b) When exposing the

anterior part of the ribcage, care should be taken to spare the:

) long thoracic nerve (innervates the serratus muscle)

Therefore, the serratus muscle should be dissected as far distally as possible This

is particularly important when high thoracic levels are exposed

The periosteum of the rib is dissected in the middle of the rib and liberated

with a blunt dissector A rib stripper is used to further liberate the rib The rib is

cut with a rib cutter as far posteriorly and anteriorly as possible to allow for a

good exposure When a thoracotomy is done with preservation of the rib, the

intercostal muscle layer is cut in the lower half to preserve the neurovascular

bundle which lies directly below the inferior edge

a b

Figure 6 Surgical anatomy for right-sided thoracotomy

aLandmark for skin incision.bSuperficial dissection.cDissection of the rib for resection.dExposure of the anterior spi-nal column.eDeep surgical dissection with ligation of the segmental vessels.fInsertion of a thorax drain and closure of the thorax.

Deep Surgical Dissection

The parietal pleura is picked up with anatomical tweezers and opened with

scis-sors Depending on the necessary exposure, the anesthetist may then deflate the

lung The intercostal space is widened with a rib spreader (Fig 6d) The lung can

be covered with an abdominal towel and retracted The anterior vertebral

col-umn becomes visible The parietal pleura is lifted off the vertebral colcol-umn with

anatomical tweezers and opened to expose the segmental vessels (Fig 6e) The

segmental vessels are mobilized with an overhold and ligated 3 – 4 cm anterior to

the rib head In severe spinal deformities the segmental vessel can first be

clamped to see whether a ligation has an influence on the blood supply of the

spi-nal cord, which would result in a decrease in evoked potentials

(neuromonito-ring) A sponge stick is used to further expose the vertebral bodies and

interver-tebral discs

Wound Closure

Close the parietal pleura whenever possible

The parietal pleura is sutured whenever possible and it is attempted to cover the

implant with pleura Before closing, one or two thorax drains are inserted We

recommend using large rather than small drains particularly when significant

bleeding has occurred Small drains are easily blocked by blood coagula The

skin is incised about one level below the target intercostal level in order to allow

for an anatomical closure when removing the drain A large towel clamp is

inserted through the wound to pick up the drain and pull out the drain from the

inside The drain is manually placed at the apex of the thorax rather anteriorly

Depending on the bleeding, we prefer to insert a second drain, which is placed

over the spine posteriorly A rib approximator is used to narrow the ribs and fix

them with a suture running around both ribs including the intercostal soft tissue

but avoiding the neurovascular bundle (Fig 6f) We recommend placing all

sutures first before tightening them At this stage, the anesthetist is asked to

rein-flate the lung Care has to be taken that all parts of the lung are inrein-flated to avoid

atelectasis If parts of the lung are not inflatable, a gentle manual massage of the

lung tissue usually resolves this problem The muscle and soft tissue layers

cover-ing the ribcage are sutured sequentially

Pitfalls and Complications

We have already mentioned the deleterious pitfall of opening the thorax on the

wrong site (wrong site surgery) The anterior approach to the spine carries a

higher risk of serious complications than the posterior route for obvious reasons

The most frequent problems associated with this approach are:

) access through an intercostal space too high or too low in relation to the

main pathology

) injury to the lung when incising the rib bed or opening the pleura

) injury to segmental vessels when exposing the spine

) injury to the azygos vein and aorta

) dissection into the intervertebral foramen

Details on the handling of complications associated with this approach are

cov-ered in Chapter 39

Left-Sided Thoraco-Phrenico-Lumbotomy

This approach gives

excellent access to the

thoracolumbar junction

This approach was introduced to spinal surgery by Hodgson mainly in the con-text of spinal tuberculosis [31, 32] Similarly to a thoracotomy, an approach to the thoracolumbar junction is possible from the left as well as from the right side When the pathology does not dictate the side of the approach, an access from the

left side is preferred because the liver and the inferior vena cava are not

hinder-ing the approach [11]

Indications

If not determined by the

pathology, the right sided

approach is preferred

The indication for a thoraco-phrenico-lumbotomy is a spinal pathology located between T9 and L5 and similar to those of a thoracotomy (Table 3)

Patient Positioning

The patient is positioned on the right side inversely to a right-sided thoracotomy (Fig 7a, b) The table can be slightly bent above the level of the pelvis to increase the distance between pelvis and ribcage

Surgical Exposure Landmarks for Skin Incision

Depending on the target level, it is usually recommended to resect the 10th rib (T10–L5) In cases with more proximal pathology, the 9th rib can be resected (T10–L5) (Fig 8a)

Superficial Surgical Dissection

After the incision of the skin and the subcutaneous tissue at the thoracolumbar junction, the superficial muscle layer is exposed consisting of (Fig 8b):

) serratus anterior muscle ) latissimus dorsi muscle ) external oblique muscle Whenever possible the muscles should be split in the direction of the fibers

Intermediate Surgical Dissection

We recommend starting with the retroperitoneal approach After splitting the external oblique muscle, the internal oblique and transversus muscles are split With sponge sticks the peritoneal sac is mobilized to the midline and freed from the diaphragma In a next step, the 9th or 10th rib is resected similarly to the method described above (Fig 6c) The anterior resection is done close to the osseous-cartilage transition of the rib The costal cartilage is split and the diaphragma is transected circumferentially about 2 cm medial to its insertion

at the thorax wall It is strongly recommended to use holding sutures bilateral

to the transection to allow for a better orientation during diaphragma repair (Fig 8d, e)

b

Figure 7 Patient positioning for left-sided thoraco-phrenico-lumbotomy

aAnterior view.bPosterior view.

Deep Surgical Dissection

The left crus of the diaphragma is transected about 2 cm above the medial and

lateral arcuate ligament The parietal pleura is incised at the thoracic level as

described above The attachments of the psoas muscle need to be mobilized

pos-teriorly The vertebrae and intervertebral discs are further exposed with sponge

sticks and rasps The segmental vessels need to be ligated at the target level

Wound Closure

At the thoracic level, the parietal pleura needs to be sutured The repair of the

diaphragma is facilitated when bilateral stay sutures were used during prior