Advanced Imaging and 3D Printing

Question 1

In conjunction with myelography, CT can be used to?

Answer 1

Assess spinal cord compression

Question 2

Can you think of any disadvantages of using CT over other imaging modalities?

Answer 2

Heavy sedation/GA
Poor spinal cord differentiation
Poor Infratentorial detail

Question 3

What does a CT struggle to differentiate with the spinal cord?

Answer 3

Grey vs white matter

Question 4

Contrast CT studies
What medium?

Answer 4

A water-soluble intravenous contrast medium

Question 5

Contrast CT studies:
How much is used?

Answer 5

2ml/kg body weight

Question 6

What is the max amount of contrast to be used for contrast CT?

Answer 6

60mls

Question 7

Contrast CT - ionised or non ionised?

Answer 7

Either can be used

Question 8

What will injection of contrast show with contrast CT?

Answer 8

areas of damage to or changes in the integrity of vascular endothelium or blood-brain-barrier.

Question 9

How can damage be seen with contrast CT?

Answer 9

Leakage of contrast

Question 10

Contrast can be used for assessment of compressive spinal cord lesions by performing a CT-myelogram. The same volume as for a myelogram with radiographs should be used (A?) but the contrast should be diluted to B)

Answer 10

A) 0.2-0.3ml/kg body weight
B) 1 in 10 parts

Question 11

In cases of ? (2) plain CT may provide the necessary information for diagnosis

Answer 11

mineralised disc extrusions
haemorrhage

Question 12

MRI is superior to CT for the evaluation of (5)

Answer 12

muscle,
tendons,
intervertebral discs,
spinal cord
cerebral parenchyma.

Question 13

High-field-strength MRI units provide better A) (2) resolution and allow more accurate interpretations than low-field-strength units.

Answer 13

A) spatial and contrast

Question 14

Can you think of any disadvantages to using MRI? (5)

Answer 14

• Financial
• Interpretation
• GA needed
• Time consuming
• No metal in vicinity

Question 15

CARE interpreting MRI - why?

Answer 15

Highly sensitive and non-significant lesions can be found

Question 16

Ultrasound can also be performed postoperatively (e.g., after hemilaminectomy) to check for possible remaining?

Answer 16

Disc material

Question 17

In cases of suspected ? abdominal ultrasound can be used to evaluate the presence of a liver shunt (portosystemic shunt)

Answer 17

Hepatic encephalopathy

Question 18

U/S can be used for confirmation of A) (scanning via persistent fontanelles,) or B) e.g., within the brachial plexus or for intraoperative identification of intramedullary lesions.

Answer 18

A) Hydrocephaluc
B) Soft tissue masses

Question 19

Scintigraphy is an imaging modality only available at specialised centres. It is useful in cases of? (2)

Answer 19

Non-localised pain or multifocal diseases

Question 20

How does scintigraphy work? What is highlighted?

Answer 20

A radiopharmaceutical agent is injected to highlight areas where the blood-brain-barrier has broken down or fails to exclude the injected radionucleotide. Lesions show up as ‘hot spots’.

Question 21

Vertebral screws and bone cement are used for the management of several conditions such as (4)

Answer 21

atlanto-axial instability (C1-C2 subluxation)
caudal cervical spondylomyelopathy (wobbler syndrome)
lumbo-sacral instability
vertebral fracture/luxation.

Question 22

Pitfall of vertebral screw and bone cement

Answer 22

risk of violation of the vertebral canal with screw placement, compromising the intervertebral foramen and / or risking damage to the vertebral artery

Question 23

With the broader availability of 3D printing and what software it is now possible to develop patient-specific drill guides for spinal pedicle screw placement

Answer 23

CAD (Computer Assisted Design)

Question 24

What prep is needed for printed drill guides?

Answer 24

A CT scan of the affected vertebrae needs to be performed first. Using the DICOM images exported in the CAD software optimal screw size and orientation can be determined. Each of the vertebrae can be manipulated in all planes for accurate planning of bicortical pedicle screw placement and it also allows the screw size for each patient to be maximised.

Question 25

Printed drill guides: The material used can vary depending on the printer and is usually made of?

Answer 25

biocompatible resin (methacrylate photopolymer resin).

Question 26

With printed drill guides; once made what needs to happen before surgery?

Answer 26

Sterilise!

Question 27

Advantage of printed drill guides? (6)

Answer 27

planning of the optimal screw trajectory prior to the surgery being performed.
Better fixation
Increased osteosynthesis strength
Reduce surgical time
Reduced morbidity

Question 28

Another field of application of 3D printing in spinal surgery is the development of patient specific 3D printed implants printed on implantable polymers or titanium.

Where can these be used?

Answer 28

These implants can conform to or reproduce the part of the vertebral column that needs to be reinforced or replaced.