Background Image
Previous Page  16 / 20 Next Page
Basic version Information
Show Menu
Previous Page 16 / 20 Next Page
Page Background

Spine Surgery

What are the basic requirements?

Essential equipment includes an image

guidance device, modified instruments,

a light source (direct light or endoscopic

assisted) and an optional access portal.

The two main methods of image guidance

used are fluoroscopy and Computer

Assisted Operative Surgery (CAOS).

The advantage of fluoroscopy is that it

is relatively inexpensive, widely available,

simple to use and provides immediate

imaging feedback which may be in

multiple planes. Its main disadvantage is

the increased risk of radiation exposure.

CAOS remains an expensive technology

because of costly hardware and software,

but the principal benefit is the limitation

of radiation exposure. CAOS requires

the use of a special device to register the

position of the spine (this is called a

dynamic reference array) that is typically

attached to both the spine and the base

of modified instruments. Recent significant

advances in computer software technology,

modification of specialised instruments and

enhanced metallurgy of implants have greatly

improved the precision of the screws that

are inserted and fixed into the spine (pedicle

and facet screws) to within sub-millimetre

accuracy. Additionally, CAOS has the unique

ability to educate surgeons regarding the

quality of their technique and therefore

allow for the improvement of accuracy and

reproducibility of the surgical procedure.

Different types of spinal devices

When the front of the spine (anterior spine)

is approached and exposed, a complete

discectomy and/or vertebral body excision

(or corpectomy) is performed followed

by the placement of an implant (interbody

device) used to stabilise the disc. In patients

with disabling low back pain secondary to

disc degeneration, FDA approved motion

preserving devices or total disc replacements

(e.g. the Charite III from Depuy, Johnson and

Johnson, and the Prodisc-L from Synthes-

Stratec Switzerland), are being routinely used

to successfully treat this condition.

The aim of Minimal Access Spinal

Surgery (MASS) is the reduction

of ‘collateral damage’ to muscles,

ligaments and soft tissue associated

with traditional spinal surgery whilst

obtaining the same clinical outcomes

of traditional open procedures.The

technique has been developed to

complement Minimal Invasive Spinal

Surgery (MISS) as the latter does

not allow for direct visualisation

of the spine. In that regard, these

two techniques DO NOT alter the

indications or goals of surgery.

There are a number of real patient benefits

associated with MASS which include:

• Early discharge from hospital

• Enhanced rehabilitation and early return

to activities and work

• Improved mobilisation

• Minimised respiratory difficulties

• Reduced blood loss

• Reduced post-operative incisional pain

There is also a clear reduction in direct and

indirect healthcare costs when employing

MISS or MASS techniques.

How is MASS performed and what

are the various indications for its use?

An interbody fusion is inserted into the

defect followed by the placing of a locking

metal plate or rod.The rod spans and

therefore neutralises the compressive forces

across the interbody device allowing fusion

to occur.The development of cannulated

systems and image guidance has allowed

for the ease of insertion of locking screws

to hold the metal plate or rod rigidly against

the spine. Cannulated screws are inserted

over carefully placed K-wires.This requires

meticulous planning and the surgeon needs

to possess superior three-dimensional

spacial awareness. Supplementary fixation

from behind (posterior) may be required

for those patients where improved

biomechanics is essential to restore

damaged posterior structures such as

ligaments or joints.This procedure can be

performed using MASS or MISS techniques.

Spinal Fusion

The two main techniques for posterior

percutaneous spinal fixation are pedicle

screws and facet screws.When treating

lumbar degenerative disc disease, both

techniques have been developed to

complement Anterior Lumbar Interbody

Fusion (ALIF) in order to perform a

circumferential or 360 degree fusion with

minimal patient morbidity. Currently, the

most widely used percutaneous pedicle

screw system is the Sextant

TM

(Medtronic

Inc, Minneapolis, MN), but many other

systems are now commercially available

for screw insertion either percutaneously

or using MASS techniques.

MASS techniques are also being increasingly

practised when performing Posterior

Lumbar Interbody Fusions (PLIF) and

Transforaminal Interbody Fusions (TLIF).

An access portal consisting of a tubular

retractor (e.g. Quadrant

TM

, Medtronic Inc,

Minneapolis, MN) is used in a minimal

access muscle splitting approach. Direct

visualisation can be accomplished using a

surgical microscope, endoscope or loupes.

The access channel created then allows for

an effortless insertion of pedicle screws and

interbody cages with minimal disruption to

the posterior lumbar tissues. Decompression

of bony and ligament blockage of the spinal

canal that results in back pain and sciatica

(lumbar spinal stenosis) and disc herniations

can also be easily performed using tubular

retractors, (e.g. METRx

TM

, Medtronic Inc,

Minneapolis, MN).The blunting of modified

sharp instruments allows the surgeon to

slip past the nerve root whilst minimising

soft tissue retraction.

Minimal Access

Spinal Surgery

Fig 1a and 1b.

Antero-posterior plain

radiographs of the whole spine

showing successful anterior

thoracic scoliosis correction and

fusion using MASS technique.

Fig 1c shows a well healed 10cm

wound.

16