Screws and plates

Question 1

When are screw and plates used as a fixation technique?

Answer 1

Forearm fractures

Around joint

Question 2

Why are screws and plates no longer used to fix long bone fractures throughout the body?

Answer 2

Improvements in intramedullary nails and external fixators makes these methods a safer and more reliable choice

Question 3

What causes fractures around joints where complete reconstruction of the cancellous bone is not possible?

Answer 3

Particularly violent fractures
Soft bone found after a delay of a few days between injury and surgery
If the bone is unnaturally soft (may be in old age)

Question 4

What is osteosynthesis?

Answer 4

Reconstruction of a fractured bone by surgical and mechanical means

Question 5

What is the risk in trying complete anatomical restoration in complex fractures with many fragments?

Answer 5

Damaging the blood supply to the fragments

Question 6

What is a ‘bridging technique’?

Answer 6

When the 2 main bony shaft fragments are linked by means of a plate to restore bone length and alignment - small fragments are left unfixed but their blood supply is left undisturbed and they retain the potential to heal as part of the overall healing of bone

Question 7

Why doW plates have limited capabilities to resist an applied load when stressed in certain directions?

Answer 7

Because they are flat and relatively thin (for practical reasons)

Question 8

What is the aim of plate fixation?

Answer 8

To achieve load sharing between plate and bone until the healing bone is strong enough to take all the load efficiently

Question 9

What would cause a plate to be more prone to bending?

Answer 9

If the plate takes most of the load - defect or gap at fracture site - fractured bone inaccurately reassembled

Question 10

What is stress reversal?

Answer 10

When the plate bends back and forwards as the incomplete bone-plate construct is loaded

Question 11

What is stress reversal likely to cause?

Answer 11

Early fatigue failure of the plate

Question 12

What 5 factors should be considered to minimise the stress reversal?

Answer 12

Plates + screws + bone should be as stable as possible
Limit damage to blood supply (so heals quicker)
Place plate in position relative to the bone so it is minimally stressed
Place plate relative to the soft tissues so uninjured tissues are not damaged (blood supply)
Plate should be made of materials that are as strong as poss

Question 13

When is the use of plates indicated?

Answer 13

When anatomical alignment must be restored accurately
When screws alone are inadequate
When load sharing can be achieved with confidence

Question 14

What can be done if it is not certain that load sharing can be achieved with confidence?

Answer 14

A bone graft (preferably autogenous) to accelerate healing before the plate becomes at risk of fatigue failure

Question 15

What is an autogenous graft?

Answer 15

A graft taken from elsewhere on the patient

Question 16

What areas of the body are plates commonly used in?

Answer 16

Around joints
Forearm (as bones rotate about each other)
On the pelvis (esp around acetabulum)
On the face and jaw

Question 17

Why would a plate be placed on the tension side of a fracture opposite to where the muscles remain in tact?

Answer 17

So it is less likely to fail

Question 18

What is eccentric loading?

Answer 18

When bones are not always loaded evenly along their axes

Question 19

What leads to eccentric loading in a fracture?

Answer 19

When the soft tissues are stripped off one side of the bone while remaining intact on the other - produces a tendency for a loaded bone to distort more on one side than the other

Question 20

Why might it not be possible to put the plate on the tension side of the fracture?

Answer 20

Need to respect the blood supply

Risk of tethering mobile structures such as tendons

Question 21

Why are plates contoured so they are bent slightly more concave than the bone?

Answer 21

To encourage compression of the bone opposite the site of attachment of the plate - aids in load sharing and forces the rough fracture fragments together across the whole cross-sec - aids stability

Question 22

What is the disadvantage of all plating techniques?

Answer 22

There must be a lot of soft tissue stripping which further damages the blood supply to already damaged areas - delay healing and risk developing an infection