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Principles of Fracture fixation

Updated: Jun 4, 2021

Principles of fracture fixation by Josefa Bizzarro, Pietro Regazzoni.


All contents of this study guide are owned by AO Foundation/AO Trauma and cannot be used for any other than private purposes. This work may only be used for your private education.

How to use this handout?

The left column is the information as given during the lecture. The column at the right gives you space to make personal notes.

Learning outcomes At the end of this lecture you will be able to: • Outline the four principles of fracture fixation

The four AO principles The four AO principles of fracture fixation are

1. Fracture reduction to restore anatomical relationships

2. Fracture fixation providing absolute or relative stability as the “personality” of fracture, patient and injury requires.

3. Preservation of blood supply to soft tissues and bone.

4. Early and safe mobilization of the injured part and the patient as a whole.

1. Fracture reduction

What does fracture reduction mean?

There are two forms of displacement:

1. Translational displacement:

a. Medial or lateral and posterior or anterior

b. Shortening or lengthening

2.Rotational displacement:

a. Internal or external rotational malaligment

b. Valgus or varus malaligment

c. Flexion or extension malalignment

Why fracture reduction?

Example 1

On the x-rays we can see a fracture fixed with an intramedullary nail that looks reduced on the lateral view. On the AP view however we can see that there is some valgus angulation of the distal fragment.

Example 2

This fracture was not treated operatively and has healed with varus, antecurvatum, and shortening malunion

Aim of reduction

Some fractures are reduced to restore

1. the bony anatomy and morphology. Perfect or anatomical reduction is required. 2. the relationship between the proximal and distal main fragments.

Length, alignment and rotation are restored. This is functional reduction.

Reduction methods

The decision, which reduction method should be used, depends on the location of the fracture: 1. Meta- and diaphyseal fractures usually need functional reduction. 2. Joint fractures need anatomical reduction.

Reduction of diaphyseal fractures

  • The functional anatomy is restored (length, alignment, and rotational axis).

  • The load-bearing axis of the extremity is restored (especially important in the lower limb).

  • An exception is the forearm which functions as a single articular unit

Reduction of articular fractures

1. The joint surface is restored anatomically. Gaps and steps in the articular surface must be avoided. 

  • “Steps” means that there is a difference between the levels of two main articular fragments. 

  • “Gaps” means that there is some space between two adjacent main articular fragments.

2. The axial alignment is restored.

If after insertion of the two compression screws there remains a fracture gap, a third screw can be inserted in compression mode on either side. Before this screw is tightened, the compression screw already placed in the same fragment needs to be loosened. After the third screw is fully tightened, the first screw is re-tightened and additional screws are inserted in neutral mode.

2. Fracture fixation

What does fracture fixation mean?

Goal of fracture fixation

1. To maintain the reduction

2. To create adequate stability which:

  • • Allows early and optimal function of the injured limb

  • • Minimizes pain

The main goal of internal fixation is to achieve prompt and, if possible, full function of the injured limb. Although reliable fracture healing is only one element in functional recovery, its mechanics, biomechanics, and biology are essential for a good outcome.

Absolute stability

  • There is no movement at fracture site.

  • It is achieved by interfragmentary compression, eg. lag screws, compression plate

  • There is no callus formation. Direct bone healing is achieved.

When is absolute stability required?

How is absolute stability achieved?

Which fixation techniques are used?

Relative stability

  • Movement at fracture site

  • There is no interfragmentary compression at fracture site. It is achieved by splinting or bridging, eg. elastic nails

  • There is callus formation. Indirect bone healing is achieved.

When is relative stability required?

How is relative stability achieved?

Which fixation techniques are used?

3. Preservation of blood supply

To what does "Preservation of blood supply" refer to?

Care for the soft tissues

  • Evaluation of limb swelling

  • Consideration for staged procedure is important: 

Primary stabilization → external fixation 

Secondary stabilization → definitive fixation

  • Careful reduction procedure 

Increases infection rate se efforts for perfect reduction are risky 

I Increases infection rate

  • Minimal invasive surgery

  • Nursing care of patient with fractures 

Care during transfer and positioning 

Taking care of body temperature - In old and young patients

- During long surgeries

  • Intraoperative nursing care 

- Use of atraumatic soft-tissue forceps and retractors 

- Use of atraumatic soft-tissue forceps and retractors  rs 

- Irrigate wound regularly 

- Cover wound with wet pads

4. Early and safe mobilization

What does this mean?

Postoperative care

  • Immediately after surgery 

- Elevation of the limb

Immediately after the operation, the treated extremity is positioned above the level of the heart to minimize swelling.

Following osteosynthesis of the upper extremity, the limb is either placed on a cushion or elevated in a bag. When the latter is used, flexion of the elbow should not exceed 75°. After any procedure, pressure, malpositioning, and deformity must be prevented. In particular, the medial epicondyle of the elbow (ulnar nerve) and the head of the fibula (fibular nerve) must be well padded.

During follow-up treatment, not only look at the x-rays but also at the injured limb. Pain, swelling, and tenderness are signs of either instability or infection.

-  Early joint motion: Use of CPM machines

CPM (continuous passive motion) machines are used to provide a continuous but passive (without force of the patient) motion for limbs where after surgery (knee or elbow) stiffness of the limb might be expected.

- Partial weight bearing 

- Adequate pain control 

- Thrombosis prophylaxis 

- Early recognition of complications

Postoperative management is not limited to the time spent in hospital, but must be carried on at home, at work and during leisure and sport. To achieve this three postoperative phases are recognized:

1. Immediately after surgery emphasis is on pain control, mobilization, thrombosis prophylaxis, and early recognition of complications.

2. When the patient leaves the hospital, attention is centered upon integration into the home and into the professional and social environment. Good mobilization is important.

3. Treatment is finished. The patient returns to his/her preoperative capabilities.

Apply the plate and press it firmly against the bone by inserting a standard bicortical screw in the hole closest to the fracture in buttress mode.

Source : AO

The AO is a medically-guided, not-for-profit organization, a global network of surgeons, and the world's leading education, innovation, and research organization specializing in the surgical treatment of trauma and musculoskeletal disorders.

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