B. Lussier
Clinical Sciences, Faculty of Veterinary Medicine, University of Montreal, Saint-Hyacinthe, QC, Canada
A fracture is a failure of a rigid structure called bone. Fracture is the result of a force that exceeds the resistance of bone. If we examine the force/deformation curve, the curve is characterized by a zone of elastic deformation, a zone of plastic deformation and finally, structural failure.
The slope of the area characterized by elastic deformation is called Young’s modulus of elasticity. Cortical bone, just like glass, can withstand a great amount of force with minimal displacement. Eventually, it shatters!
There are 5 types of forces that can apply to bone and that with act on a fracture once it is reduced: traction, compression, angulation, rotation, shear. The goal of fracture fixation is to make the inventory of the forces responsible for the loss of reduction of fractures and then, neutralize them!
Compression, Traction, Angulation, Rotation, Shear
To neutralize the different forces that act of a fracture, several implants can be used. Here is a non-exhaustive list of implants/devices and the forces they can neutralize.
|
|
Compression
|
Traction
|
Angulation
|
Rotation
|
Shear
|
|
Cast
|
–
|
–
|
+
|
+/–
|
–
|
|
Pins
|
–
|
–
|
+
|
–
|
+/–
|
|
Multiple pins
|
–
|
–
|
+
|
+/–
|
+/–
|
|
Pin/plate construct
|
+
|
+
|
+
|
+
|
+
|
|
Cerclage
|
–
|
–
|
–
|
+
|
+
|
|
Tension band wire
|
–
|
+
|
–
|
–
|
–
|
|
Diverging K-wires
|
–
|
+
|
–
|
+/–
|
–
|
|
External fixator
|
+
|
+
|
+
|
+
|
+
|
|
Bone plate
|
+
|
+
|
+
|
+
|
+
|
|
Locking plates/devices
|
+
|
+
|
+
|
+
|
+
|
|
LC-DCP, ALPS, PAX, FIXIN, SPO
|
+
|
+
|
+
|
+
|
+
|
|
Interlocking nail
|
+
|
+
|
+
|
+
|
+
|
Practical Application of These Principles
Case 1
- Closed transverse diaphyseal fracture of the tibia
- Forces to neutralize
- Implants/devices
- Multiple IM pins
- IM pin and external fixator
- Interlocking nail
Case 2
- Closed long oblique/spiral diaphyseal fracture of the femur
- Forces to neutralize
- Implants/devices
- Shear +++cerclage wires
- Implants devices
- Combination of
- Cerclages and IM pin
- Cerclages and plate/screws
- Cerclages and external fixator
Case 3
- Closed comminuted diaphyseal femoral fracture
- Forces to neutralize
- Implants/devices
- Shear +++
- Plate, locking devices, interlocking nail, external fixator
- Pin/plate construct
- Implants devices
- Combination of
- Cerclages and IM pin
- Cerclages and plate/screws
- Cerclages and external fixator
Case 4
- Closed long oblique distal diaphyseal fracture of the humerus
- Forces to neutralize
- Implants/device
- Shear +++
Case 5
- Closed short oblique proximal diaphyseal fracture of the tibia
- Forces to neutralize
- Implants/device
- Shear +++
- No cerclages…
Case 6
- Salter Harris type II of the distal femur
- Forces to neutralize
- Implants/device
- Shear -
Case 7
- Femoral trochanteric osteotomy
- Forces to neutralize
- Implants/device
- Shear +