Spinal Disorders: Fundamentals of Diagnosis and Treatment Part 38 pot

Indications for a retroperitoneal lumbotomy L2–L5 spinal deformities lumbar fractures/instabilities degenerative disorders tumors infections Patient Positioning For this approach th

a b

Figure 8 Surgical anatomy for left-sided thoraco-phrenico-lumbotomy

aLandmark for skin incision.bSuperficial dissection.cDissection of the rib for resection (seeFig 6c).dThe rib cartilage

is split and marked with stay sutures.eThe diaphragm is split about 2 cm medial to its rib insertion.fThe medial and lat-eral crus of the diaphragm are transected and marked with stay sutures The segmental vessels are ligated The thoracic exposure is shown inFig 6d, e.

Pitfalls and Complications

Injuries to the thoracic duct can result in a chylothorax

A frequent complication is to accidently open the peritoneal sac during

dissec-tion of the diaphragma This can be avoided when the preparadissec-tion of the two

body cavities is started from the abdominal site and the peritoneum freed from

the diaphragma When taking the diaphragma down to its insertion at the spine,

care has to be taken not to injure the:

) greater splanchnic nerve

) ascending lumbar vein

) sympathetic trunk

) thoracic duct (rarely visible during preparation)

A detailed discussion of the complications associated with this approach is

included in Chapter 39

Anterior-Lateral Retroperitoneal Approach to L2–L5

The anterolateral retroperi-toneal lumbar approach

is easily applicable even

in obese patients

The anterior-lateral retroperitoneal approach to the lumbar spine has been an

established operative technique since the early 1960s This approach can be

car-ried out also from the right side The left sided approach, however, is favored

because the inferior vena cava is less at risk This approach is easy to perform

even in obese patients because the abdomen is hanging to the side and the flank

is exposed

Indications

Indications for this approach are spinal disorders located between L2 and L5

(Table 4):

Table 4 Indications for a retroperitoneal lumbotomy (L2–L5)

) spinal deformities ) lumbar fractures/instabilities

) degenerative disorders ) tumors

) infections

Patient Positioning

For this approach the patient is positioned on the right side similarly to as

per-formed for the thoraco-phrenico-lumbotomy (Fig 7a, b)

Surgical Exposure

Landmarks for Skin Incision

We favor a mini-open approach to the lumbar spine, which necessitates image

intensifier localization of the skin incision With a 6- to 8-cm incision, a two-level

fusion can be done without difficulty when using a retractor frame The skin

inci-sion is done in the fiber direction of the external oblique muscle (Fig 9a)

a b

Figure 9 Surgical anatomy for the anterior-lateral retroperitoneal approach to L2 – L5

aLandmarks for skin incision.b, c, dTranssection of the external oblique, internal oblique and transverse muscles.

eRetraction of the psoas muscle exposing the vertebral column.fMedial retraction of the peritoneal sac exposing the large abdominal vessels Ligation of the segmental vessel.

Superficial Surgical Dissection

A muscle splitting approach

is preferred

After the incision of the skin and the subcutaneous tissue, the three layers of the abdominal wall:

) external oblique muscle (Fig 9b) ) internal oblique muscle (Fig 9c) ) transversus muscle (Fig 9d) are separated in the direction of their fibers

ered with a moistened abdominal towel The paravertebral sympathetic chain

medial to the psoas muscle as well as the ureter need to be identified and

retracted together with the peritoneum carefully in a medial direction The psoas

is mobilized from the spine and retracted posteriorly The genitofemoral nerve

which lies on the anteromedial side of the psoas muscle needs to be preserved

Care has to be taken not to injure the segmental or great vessels anteriorly while

Take care with the iliolumbar vein when retracting the large vessels medially

liberating the spine with sponge sticks Special attention has to be paid to the

ilio-lumbar vein at level L4–L5, which requires ligation if it limits the mobilization of

the common iliac vein In men, the psoas muscle can be very big and covers

almost the whole lateral aspect of the vertebra In these cases, a psoas splitting

approach can be used to approach the intervertebral discs for a fusion [8] The

latter approach is less suited to a complete corpectomy

Wound Closure

Each layer of the abdominal wall needs to be sutured separately Suction drainage

is usually not needed

Pitfalls and Complications

Care has to be taken not to injure the:

) segmental vessels

) ascending lumbar vein

) iliac vein and artery

) genitofemoral nerve on the anteromedial side of the psoas muscle

) paravertebral sympathetic chain

) ureter (slightly attached to the peritoneum)

A detailed description of the management of complications is outlined in

Chap-ter 39

Anterior Lumbar Retroperitoneal Approach

Indications

The anterior lumbar retroperitoneal approach is indicated for spinal pathology

located between S1 and L3 The indications are similar to those for the

lumbo-tomy with the exception that the approach exposes the spine at S1–L2 (Table 4)

Patient Positioning

The patient is positioned supine with both arms abducted The table can be

slightly bent at the level of the pelvis The positioning should be done in a way to

allow the application of a table mounted retractor system, which facilitates the

spinal exposure (Fig 10)

Figure 10 Patient positioning for an anterior retroperito-neal approach

A table mounted retractor facilitates the approach.

Surgical Exposure Landmarks for Skin Incision

Landmarks for the skin incision are the umbilicus, symphysis and iliac wings The umbilicus frequently projects onto the L4 level However, this landmark is largely variable and necessitates image intensifier control to allow for a minimal length skin incision The skin incision lies usually in the midline Approaches to the L3/4 disc space, however, necessitate extending the incision above the level of the umbilicus In these cases, we recommend using a slightly parasagittal inci-sion (Fig 11a)

Superficial Surgical Dissection

After skin incision and dissection of the subcutaneous tissue, the anterior rectus sheath is exposed over a length of 6 – 8 cm and opened 2 cm lateral to the midline (Fig 11b) The underlying rectus muscle is retracted laterally exposing the poste-rior rectus sheath and the arcuate line (Fig 11c) The peritoneal sac is mobilized medially below the arcuate line The peritoneal sac is adherent to the inferior sur-face of the posterior rectus sheath and needs to be liberated from it to allow fur-ther retraction After liberation, the posterior rectus sheath is incised about 2 cm medial to the abdominal wall and the peritoneum can be further retracted over the midline (Fig 11d)

Deep Surgical Dissection

At depth, the bifurcation is often visible with a medial sacral artery and vein Depending on the size of the vessels, a ligation is necessary Coagulation at the disc level should be avoided to preserve the presacral sympathetic plexus In males, damage to the sympathetic plexus may result in a retrograde ejaculation

The L 5/S1 disc is exposed between the bifurcation ( Fig 11e) by slightly mobiliz-ing the vessels to both sides Manipulation at the bifurcation should be done very carefully (if needed) to avoid injuries to the vessels, which are difficult to repair The ascending lumbar vein

is at risk when retracting the

common iliac vein medially

The L 4/5 disc space or levels above are exposed by retracting the left common

iliac vein and artery to the contralateral side (Fig 11e) During this maneuver, great care has to be taken not to tear the ascending lumbar vein from the common iliac vein We recommend exposing the ascending lumbar vein and ligating it before retracting the vessels to the contralateral side The paravertebral sympa-thetic chain lies medial to the psoas muscle and should be mobilized laterally while the ureter together with the peritoneum is retracted medially

a b

Figure 11 Surgical anatomy of the anterior retroperitoneal approach

aLandmarks for skin incision.bExposure of the anterior rectus sheath.cDissection of the posterior rectus sheath close

to the abdominal wall (arcuate line).dExposure of the anterior spinal column.eDeep surgical dissection at the L5/S1

level accessing below the bifurcation.fDeep surgical dissection at the L4/5 level retracting the common iliac artery and

vein medially.

Wound Closure

The posterior rectus sheath should be readapted if possible Interrupted sutures are placed in the anterior rectus sheath using slowly dissolving sutures We do not routinely use a suction drainage

Pitfalls and Complications

Care has to be taken not to injure the:

) segmental vessels ) ascending lumbar vein ) common iliac vein and artery ) paravertebral sympathetic chain ) ureter (slightly attached to the peritoneum) Injury to the sympathetic

chain can result

in retrograde ejaculation

in males

Injuries of the sympathetic chain may result in retrograde ejaculation (in males)

or a sympathectomy syndrome with disturbed capability for vasoconstriction This may result in the feeling of a hot (ipsilateral) or cold (contralateral) leg or foot, respectively Weakness of the abdominal wall particularly in multiparas can result in abdominal herniations and needs to be repaired A detailed description

of the management of complications is provided in Chapter 39

Posterior Approach to the Thoracolumbar Spine

The posterior approach has been the most commonly used access to the spine since the 1950s The exposure is straightforward but the collateral damage to the muscle is not negligible [23, 24, 39, 40] Wiltse et al [68] and Fraser et al [21] have

therefore suggested a so-called “muscle splitting approach” which can be used

when midline exposure is not necessary for decompression, e.g for posterolat-eral fusion of a spondylolisthesis Minimal-access surgery is preferred whenever possible The target level should be determined with image intensifier to expose the spine only as much as is needed

Indications

There are a wide variety of indications for this approach (Table 5):

Table 5 Indications for the posterior approach to the thoracolumbar spine

) spinal stenosis ) thoracolumbar fracture/instability ) disc herniation ) tumors

) painful motion segment degeneration ) infections ) spinal deformities

Patient Positioning

An unobstructed abdomen

is key to successful decompressive surgery

The patient is positioned prone on rubber foam blocks (Fig 12a) A headrest with support for mouth, nose and eyes is used to avoid pressure sores (Fig 12b) It is important that the abdomen is freely hanging and not compressed (Fig 12c) This is particularly important for decompressive surgery where a compressed abdomen can result in congested epidural veins and result in excessive bleeding

a b

c

Figure 12 Patient positioning for a posterior thoracolumbar approach

aRubber foam blocks supporting the patient in prone position.bHeadrest.cPositioning of the patient with free

hang-ing abdomen.

Surgical Exposure

Landmarks for Skin Incision

The landmarks for the posterior approach are:

) spinous processes

) posterior superior iliac spine

) iliac wings

The line drawn between the bilateral posterior superior iliac spine usually

pro-jects to the disc level of L4–L5 (Fig 13a) However, this is unreliable and image

intensifier control is necessary in every case

a b

Figure 13 Surgical anatomy of the posterior thoracolumbar approach

aLandmarks for skin incision.bSuperficial surgical dissection.cDeep surgical dissection.dMuscle retraction with pin-pointed retractors to minimize muscle damage Note the decortication at L4–S1 on the left side as preparation of the bone graft bed.

Superficial Surgical Dissection

After the incision of the skin in the midline above the spinous processes and the dissection of the subcutaneous layers, the thoracolumbar fascia is incised with a cautery knife (Fig 13b) The paraspinal musculature is subperiosteally detached from the spinous process and the laminae Sponges are used to push the paraspi-nal muscles laterally and control bleeding by densely packing the created space between the spinous process and the muscle (Fig 13c) Care has to be taken not

to injure:

) facet joint capsules

Deep Surgical Dissection

In spinal fusion cases, the posterolateral bed has to be prepared for the bone graft Therefore, the multifidus muscle must be detached from the laminae, facet

damage The retractors should be released intermittently (Fig 11d).

Wound Closure

The thoracolumbar fascia needs to be closed over suction drains The fascia

needs to be sutured tightly either by close interrupted or running sutures

Pitfalls and Complications

The posterior access is usually a safe approach to the spine In slim patients,

how-ever, the interlaminar window at L5/S1 can lie very superficially and can be

injured with the cautery knife causing an unintended durotomy

Landmarks for Screw Insertion

Computer assisted surgery provides a false security

in inexperienced hands

Screw fixation has become a standardized technique throughout the entire spine

However, the prerequisite for a safe screw insertion is critically dependent on a

profound knowledge of the surgical anatomy Preoperative planning of the screw

trajectories with CT scans is mandatory if an altered anatomy (e.g in spinal

deformities) is expected Computer assisted surgery [7, 42, 55, 60] does not

com-pensate for insufficient knowledge of the anatomy and can even be dangerous in

inexperienced hands

Cervico-occipital Spine

Screw Placement of the Occiput

Screw insertion must be below the external occipital protuberance

Screw fixation of the occiput should be in the area with the thickest bone, which

is in the midline between the superior nuchal and inferior nuchal line [54]

(Fig 14 ) Above the superior nuchal line, injuries to the intracranial sinus must

be expected There is a wide variation in thickness of the occipital bone [61] The

maximum thickness of the occipital bone ranges from 11.5 to 15.1 mm in males

and from 9.7 to 12.0 mm in females and is found at the level of the external

occipi-tal protuberance [15] Fixation can be done using a Y-plate [26] or bilateral

tita-nium plates [45] The screws are inserted either in the midline or 2 – 3 mm

para-sagittally, respectively The parasagittal cortical bone is substantially thinner and

ranges between 3 and 7 mm [30] The screw holes can be prepared using a drill

guide (2.5 mm) with an adjustable drill penetration depth Initially the depth is

set at 4 mm and is increased incrementally until the distal cortex is penetrated In

areas of the occiput which are thicker than 7 mm, unicortical fixation is as strong

as bicortical fixation [61] The standard screw diameter is 3.5 mm and sometimes

requires pre-taping In case of a cerebrospinal fluid flow from the hole, insertion

of the screw suffices to close the leak

Posterior Atlantoaxial Transarticular Screw Fixation

The vertebral artery

is at risk laterally and the spinal cord medially

Atlantoaxial transarticular screw fixation [27, 28] is a frequent stabilization

tech-nique for degenerative and traumatic disorders (Fig 15a–c) Although lateral

image intensifier control is sufficient, we recommend using a simultaneous