Principle of absolute stability

Principle of absolute
stability
Suthorn Bavonratanavech M.D.
Bumrungrad Hospital


Out come
- Understand the definition of absolute
stability & its effect on fracture healing
- Understand the mechanical & biological
requirements to achieve absolute stability
- Understand clinical indications for
absolute stability


Definition
• Rigidity : ability of the implant
to withstand deformation

• Stability : lack of motion
between fracture fragments


Stability
• Stability is a spectrum from zero
(absolute) to instability

• Absolute stability : no movement between
the fracture fragments

• Relative stability : some motion between

the fracture fragments



Absolute stability
- Effective abolish of fracture site
movement
- Reduces the strain at the fracture site,
such that external callus will not form…


Absolute Stability :
How?
No motion
between fracture surfaces
under functional load


Absolute stability
Anatomic reduction


Absolute stability
Anatomic reduction
maximal friction


Absolute stability
Anatomic reduction
maximal friction

Interfragmentary compression


Absolute stability
Anatomic reduction
maximal friction
Interfragmentary compression
Pre-Loading


Absolute stability

• Interfragmentary Compression
– Maintain close contact between two
fragments
– Compression produced is larger than
the traction produce by function

• Friction  counteract shear force


Biological requirements
- Preservation of blood
supply
- Anatomical reduction, ie,
no gap


Methods to produce Absolute

Stability
• Interfragmentary compression
• Lag Screw Technique
• Compression plate
• Tension Band Fixation


Lag Screw
Interfragmentary Compression
Gliding hole

Thread hole


Absolute Stability by plate fixation
•Anatomical
reduction
•Compression by:
Compression plate


Dynamic Compression Plate


Compression by overbending
Diaphysis:
in order to compress opposite
cortex plate must be prebent

No pre bend of plate


Mechanical improvements
pre-bending for bilateral compression


Absolute stability  no motion
 direct bone healing  heal
without callus


Primary (Direct) Bone Healing
Internal
remodelling
replaces dead
structures
remodelling osteons
Osteoclast

Vessel

osteoblast


Primary (Direct) Bone Healing


Primary (Direct) Bone Healing
• Fracture gradually

disappears
• Minimal periosteal callus


Dynamic compression
Tension band