Internal Fixation Of The Spine

Question 1

What are the key function of the spine

Answer 1

Biomechanics

1. Motion
2. Weight transfer
3. Protection of neural elements

Question 2

How many pieces of motion are there and what is each function.

Answer 2

4 pieces of motion

Lever - the vertebra is the lever. It is a ridged object that pivots

Fulcrum - together the disc and facet are the fulcrum

Activation - muscles attached to the vertebra via spinous process / transverse process.
- pull in the bone to create movement

Restraint - ligaments are the passive restraint, preventing the spine from exceeding its normal range of motion

Question 3

Functional spinal unit (FSU)

Answer 3

The smallest physiological motion of the spine to exhibit biomechanical characteristics similar to those of the entire spine

Question 4

What is the orientation of the cervical spine?

Answer 4

In the cervical spine the facets are oriented in the axial plane. This allows rotation, lateral bending, extension and flexion. Because of the spine is most mobile of all the spine regions

Question 5

What is the orientation of the thoracic spine?

Answer 5

In the Thoracic spine the facets are oriented in a frontal plane. This orientation, coupled with the spines attachment to the rib cage, limited movement, makes of the Thoracic spine at the least mobile region

The primary motion achieved by the Thoracic is “cat stretch”

Question 6

What is the orientation of the lumbar spine

Answer 6

In the lumbar spine at the facets are oriented in a sagittal plane. Thus, the lumbar spine can achieve flexion and extension with some lateral bending, but minimal rotation

Question 7

What is decompression

Answer 7

Decompression is a procedure to relieve the pressure on the brain, spinal cord, or spinal nerve

Question 8

What are the two forms of decompression and what are the differences between the two

Answer 8

There are two forms of decompression

Direct - involves physically removing the tissue that is exerting pressure on to a neural element

Ex. Removal of a herniation.

Indirect - involves increasing the space of the neural structure by increasing or restoring the height of the disc space

Placing a graft into the inner body space

Question 9

Weight transfer

Answer 9

80% of the weight is transferred through and absorbed by the anterior columns (vertebral bodies and disc)

20% is transferred into Missouri by the posterior elements (lamina and facets)

Question 10

What are the two types of curves in the spine and which region of the spine is each curve associated with

Answer 10

Lordotic - cervical, lumbar

Concave towards the posterior

Kyphotic - Thoracic, sacral

Concave towards the anterior

Question 11

What are the basic steps for a plate and screw constructs

Answer 11

1. Size plate
2. Position and provisionally stabilize the plate
3. Create a pathway for the screws
4. Insert screws
   5 perform final tightening

Question 12

What are the basic steps for a screw and rod constructs.

Answer 12

1. Create a pathway for the screws
2. Insert the screw
3. Connect the screw to the rod
4. Perform final tightening

Question 13

Or the basic steps to a inner body fusion

Answer 13

1. Access the disc
2. Remove the disc
3. Create an osteogenic environment
4. Trial
5. Prepare the spacer
6. Implantation

Question 14

What are the three regions of the screw and what is the function of each region.

Answer 14

Head

Shaft

Tip