technical aspects of percutaneous vertebroplasty & kyphoplasty

Technical Aspects of PercutaneousVP and KP procedures

The Neurosurgeon’s perspective

M o h a m e d M o h i E l d i nProfessor of Neurosurgery

Cairo UniversityEgypt

Vertebral AugmentationVertebroplasty

(1984): Injection of material (usually PMMA cement) into vertebral body

Kyphoplasty

(1998): Injection after manipulation involving cavity creation

Pain associated with

Compression vertebral fractures

• Primary osteoporosis• steroid-induced osteoporosis• Neoplastic-induced fracture• Sub-acute traumatic collapse• Vertebral angiomas • Symptomatic microfracture [MRI] • Lytic lesion [CT] without loss of vertebral height

Predictors of fracture

19.2% a second fracture within one year

24% a further fracture within a year

Percutaneous VP and KP Simple procedures

However, must be treated with respect, as its application, without appropriate preparation

and physician knowledge, can quickly produce increased pain, permanent neurologic injury,

and even death

Local

GeneralNeurolepto

AnaesthesiaAnaesthesia

Election will depend on surgeon’s experience and characteristics of patient.

The three steps of vertebroplasty: 1. placement of a guide wire

2. insertion of a working cannula 3. injection of cement filler

The five steps of kyphoplasty: 1. placement of a guide wire

2. insertion of a working cannula 3. reaming working channels beyond the cannula tips4. balloon insertion, inflation, deflation, and removal

5. injection of void filler

Transpedicular Approach

Bilateral Transpedicular Approach

Unilateral Transpedicular Vertebroplasty

Injection of bone cement (methyl-methacrylate)

Kyphoplasty

Parapedicular Approach(lateral to pedicle and above the

transverse process)

This avoids the exiting nerve root (courses under the pedicle)The needle entry site along the lateral aspect of the vertebra

Does not allow local pressure after needle removal, the chance for bleeding higher than with the transpedicular approach

Lateral Extrapedicular Approach utilizes Effective Pedicle

(the rib-pedicle complex)

The instrument must also be angulated more toward the midline to avoid lateral penetration

of the vertebral body

Anterior Cervical Approach

Manual displacement of the carotid–jugular complex and guide needle insertion

Needle position can be confirmed with CT.

Typical biplane configuration

Combined CT and mobile fluoroscopy SETUP

The skin incision is 1 cm lateral of entry point

for L1 to L4, and 2 cm lateral for L5

Starting point of right transpedicular access between 1 and 3 o’clock

Starting point of left transpedicular access between 9 and 11 o’clock

Ending points for transpedicular access

Convergence towards the midline, which however should not be crossed

Safety for injection

Pictorial of trajectory ‘‘stopping points’’

to ensure safe placement of the Jamshidi needle

Safety for cement injection

The tip at the junction of the anterior and middle third of the vertebra away from the large venous

confluence in the posterior of the vertebra

The second needle

The white line shows its trajectory

predict the ultimate needle tract

make adjustments

Cement injection is the last step in all levels

It is important to fill the anterior 2/3–3/4

of the vertebral body

Cement should reach or cross the midline to reinforce both halves of the vertebra (white

arrows)

A Unipedicular VP

shows distribution of cement into

both halves of the vertebra

Inflatable ballon in the midline of the fractured body

Tip of the guide pin over the center of the vertebral body

Kyphoplasty – “The Good”

• A modification of the vertebroplasty procedure to:– restore vertebral

body height– Low risk of clinically

evident cement extravasation.

Kyphoplasty – “The Bad”

• There is still a risk of extravasation• Close analysis of literature indicates height

restorations as an insignificant result.

Kyphoplasty – “The Ugly”

• The big question, “Is this cost justified (when compared to vertebroplasty) for the added safety?”

• Most studies are retrospective analyses. This is an area ripe for further analysis10.

Pearls and Pitfalls

Cement Extrusion

Kyphoplasty with small amount of anterior(white arrow) and lateral (black arrow) cement extrusion

rarely associated with clinical sequelae

However, leakage may be significant !!

To prevent rare significant neurologic deficit associated with PVP, intact posterior vertebral body cortex is one

of the most important prerequisite that must be thoroughly confirmed preoperatively

Cement too liquid when injected tracked backward along the needle path leaving

cement in the soft tissues

In myeloma and osteolytic metastases

Complete destruction of the posterior cortical wall

Special techniques in cases ofmyeloma and osteolytic metastases

• The risk of cement leakage is greater,– the egg-shell technique should be preferred to the

conventional balloon kyphoplasty technique • Pedicles are may be affected by osteolysis,

making transpedicular access no longer safe– a contralateral single approach via a still intact pedicle

or – an extrapedicular approach can be chosen.

• The possibility of dislocation of the cement block has to be taken into account if the anterior cortical substance is missing

Pre Post 1y 3y

Dislocation of the cement

Vertebroplasty of T12 with osteolysis and unknown primary tumor with ventral dislocation of the cement

beginning after 3 weeks

9 months 2 years 3 weeksIntraop.

Cement dislodgement 6 months after the percutaneous vertebroplasty

C7 & T1 Visualization fluoroscopically impossible

shoulders

very small epidural leak of cement (CT guided PV)

Tumor migration with cement injection

Leakage into inferior disc(No clinical consequence)

Cement leak into the disc space (black arrow).

The cement was allowed to harden and the cannula exchanged over a wire so that

subsequent cement injection could take place

The severe collapse

extreme compression of T12 with residual marrow space

Height restoration with traction

A bilateral transpedicular approachPedicle of collapsed vertebra seen

Trajectory through the lower aspect of the pedicle parallel to the residual endplates to access the

anterior part of the vertebral body

The amount of cement into an extremely collapsed vertebra much smaller than is usually used for less collapsed vertebrae

Digital subtraction venogram

The contrast leak is not predictive of where the cement go. Also, the contrast obscures detection of early cement leak

Difficult Reductions: Balloon does not inflate adequately

Using the Bone Curette• in older fractures• a specially designed curette retracted and

advanced to score the bone in the region. • The curette is removed, and balloon inflation

is again attempted.

Standard balloons, eccentric expansion with risk of blowout of the vertebral walls or endplates

a directional balloon tamp may be desired

Vertebral Body Breakthrough: EggshellTechnique of Containing Bone Cement

Partial loss of reduction after balloons deflated … Lordoplasty

(indirect reduction maneuver)

Sacroplasty

Sacral insufficiency fracturesBest performed under CT guidance.

Burst fracture of L1

With good reduction one month after instrumentation removal

(18 months posttrauma)

Developments…..

• Calcium phosphate in young patients with traumatic fractures

• Prophylaxis by adding chemotherapy agents or radioactive isotopes to the cement in tumour

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