The document discusses principles and techniques of internal and external fixation for fractures. It covers the four principles of internal fixation, types of compression, plate fixation techniques like the load screw technique and pre-bending plates, different types of plates and screws. It also discusses external fixation principles like the seven principles of callus distraction, advantages and disadvantages of external fixation, types of external fixators and their functions, dynamization and specific uses in the lower extremity.

1. AO Fixation
Review Questions

2. What are the four AO
Principles of Internal
Fixation?

3. Accurate anatomic reduction
Rigid internal compression fixation
Early and pain free ROM
Atraumatic operative technique

4. What is the difference between Static vs
Dynamic vs Interfragmentary
Compression?

5. Dynamic: achieved with the use of a tension band wire or tension band plate
Static: generated by ‘pre-load’ of lag screws or tubular plates that prevent
separation of two surfaces as long as the functional load produced by limb
performance is less than the preload generated by the screws or plates. The
compression is constant in nature. This can also be accomplished by rigid
external fixation.
Interfragmentary compression usually requires multiple screws. Proximal anchor
screw (perpendicular to the cortex of the bone) and the distal compression
screw (perpendicular to the osteotomy site).

6. Please describe Pauwels principle
(tension band principle)

7. Pauwels principle (tension band principle): an imposed
load applied eccentrically is altered by application of a
‘band’ on the opposing side, canceling out bending
and altering it into pure compression. This principle is
dynamically created by functional limb loading. (ex
putting a plate on the tension side of a fracture)

8. In your own words, describe the
Load Screw Technique

9. This technique is performed by using an offset (eccentric) drilled hole for
the initial screws used to fixation the plate to the fracture fragments.

10. Where is the plate
aligned?

11. The plate is aligned on the
reduced fracture site

12. Where do you drill the thread hole?
near or far from the fracture site?

13. The thread hole is drilled at the
far side of the plate hole or at
the edge of the hole farthest
from the fracture site.

14. How is inter-fragmental compression
created?

15. As the screw is inserted, the head of the screw will
seat itself into the center of the hole in the plate by
shifting the bone fragment in the direction of the
fracture. This motion is countered by a similar shift
from the opposite fragment, and as the two fragments
are pushed toward each other, interfragmental
compression is created.

16. Which screws are used
as load screws?

17. Only the initial two screws adjacent to the
fracture line are used as load screws. This is
the most common application of plate
fixation used in the foot and ankle region.

18. What is the problem
with tubular plates?

19. 1⁄2, 1/3, 1⁄4, tubular plates have great tensile strength
but do not resist against bending.

20. So, how do you create
rigidity?

21. Application of a pate plus interfragmentary
compression with screw is a great way to
created rigidity within the fracture area.

22. What is the purpose of
pre-bending the plate?

23. This is used so the cortex opposite the plate does not gap. The offset holes
are drilled before the plate is bent. The plate is bent slightly at its center.
As the load screws are inserted, the bone fragments are drawn up against
the undersurface of the plate, and the opposite cortices come into contact
before the surface of the fracture that is adjacent to the plate.
As the load screws are tightened, the fragments are drawn closer together
and the gap at the adjacent cortex decreases.
As the gap reduces, the plate is bent back into a straightened position with
even contact and pressure existing along the entire fracture surface.

24. NOTE
The load screw concept and the technique of
pre-bending are fundamental principles for the
creation of axial compression with plate
fixation.

25. What are the different types of plates?

26. - Neutralization
- Buttressing
- Dynamic compression plate
- Limited contact Dynamic compression

27. List the types of Internal Fixation

28. - K wires
- Monofilament wires
- Steinmann pins
- Intramedullary nails (rods)
- Screws
- Staples
- Plates

29. What is a Herbert Bone Screw?

30. Headless screw that is threaded at both
ends

31. Which threads have smaller pitch?
Proximal or Distal?

32. Proximal threads have a smaller pitch
than the distal threads

33. What is the purpose of pitch difference
on both ends?

34. This pitch difference provides
compression between adjacent bony
fragments

35. What is the Herbert Screw Diameter?

36. Screw diameter is 4 mm

37. Which side needs to be tapped on
Herbert screw?

38. Just need to tap the distal threads
(proximal threads are self tapping)

39. What is a Reese Arthrodesis Screw?

40. Reese Arthrodesis Screw

41. How do the threads differ on Reese
Arthrodesis Screw?

42. Clockwise (right handed) screw threads
proximally
Counterclockwise (left handed) threads
distally

43. List the plate sizes and their
respective screws.

44. Semi tubular plate: fits 4.5 mm screws
One third tubular plate: fits 3.5 mm & 4.0 mm
One quarter tubular plate: fits 2.7 mm screw

45. What is the indication for posterior anti-
glide plate?

46. Indicated for Danis-Weber type B
fracture

47. Why?

48. These fractures tend to displace
posteriorly and superiorly
The plate will resist the displacement
and provide some compression

49. External Fixation

50. What are the 7 Principles of
Callus Distraction?

51. (some of these principles are relative to the particular anatomical correction)
1. Preservation of blood supply: Atraumatic cortectomy
2. Rigid external fixation
3. Latency period before distraction: usually 7 – 14 days; allows 1st stage of bone healing to begin
4. Steady rate of distraction: about 1 mm / day
5. Ideal frequency of distraction: about .25 mm per turn (4 turns per day)
6. WB on limb during distraction
7. Post distraction healing time: for every 1 mm of lengthening you must rest for 1 week

52. General Advantages of External
Fixation?

53. - Applicable to closed,
- Open or limited open surgical techniques
- Device can be conformed to the shape of the leg and foot
which will allow multifunctional correction
- Allows acute or gradual lengthening
- Can be adjusted post operatively
- Can be stable enough to permit early weight bearing
Largest role in foot & ankle surgery is with pilon fractures

54. General Disadvantages of External
Fixation?

55. Disliked by patients
Disliked by surgeons
Lengthy treatment time
Increase risk of infection compared to internal fixation (ex: pin
tract infections)

56. What are the 3 different types of
External Fixators?

57. 1. Circular
2. Mono-lateral
3. Hybrid

58. Circular
1. Ilizarov frame
2. Taylor spatial frame
Six color coordinated knobs
Radiographic parameters put into a computer
Knobs are turned to a certain number each day according to the computer calculations
New device
Monolateral
Orthofix
Hidleburg
Hoffman
Hybrid
Combination of the ilizarov and monolateral frames

59. Functions of External Fixators?

60. 1. Compression
2. Distraction
- New bone that is formed is called the regenerate
3. Angulation
4. Translation
5. Rotation

61. What is Dynamization?

62. Dynamization is the process by where stress is
gradually applied to the new bone that has formed so
that the trabecular bone will remodel according to
Wolf’s law making the regenerate strong and suitable
for weight bearing without the device.
This is initially done by loosening up the device
gradually. If the is not done the regenerate will
fracture very easily.

63. What are the different ways to perform
corticotomy?

64. Corticotomy (osteotomy) can be done
differently using
- Osteotome (classic iliazarov method)
- Pre-drilling and osteotome
- Gigli saw method

65. Specific uses of external fixation in the
lower extremity

66. 1. Non-Unions
2. Trauma (pilon fractures, etc)
3. Osteomyelitis (useful when large amounts of bone is resected)
4. Lengthening (tibial, metatarsal)
5. Arthrodesis (ankle, subtalar)
Advantages:
1) Longer lever arm than internal fixation;
2) Post-op adjustability
6. Correct malunions
7. Severe deformities (clubfoot, etc)
8. Joint preservation
1. Realignment of arthritic joints: Supra-malleolar osteotomy to realign the ankle joint
2. The anterolateral aspect of the ankle joint is the most loaded part and is usually
where arthritis will begin
3. Distraction of arthritis joints can decrease pain, though no studies have show that
articular cartilage will regrow.
4. CORA: center of rotation of angulation
Osteotomy at this point will lead to a full realignment of the foot & ankle