Fracture Fixation Principles and Devices

Fracture fixation is the surgical stabilisation of broken bone so that it can heal in acceptable alignment. Its principles concern how much stability a construct provides and how that stability interacts with the biology of bone healing, while its devices range from plates, screws, and intramedullary nails to external fixators and tension-band wiring.

Definition

Fracture fixation is the use of implants or external devices to reduce and stabilise a fractured bone, providing a defined mechanical environment (absolute or relative stability) that supports either direct (primary) or callus-mediated (secondary) bone healing.

Scope

This topic covers the mechanical and biological principles of internal and external fixation, the main implant types, and the central concept of matching the stability of a construct to the intended healing pathway. It is a reference description of how fixation is conceived and is not operative or treatment instruction for any individual case.

Core questions

• How is reduction achieved and maintained?
• What degree of stability does a given construct provide, and which healing pathway does it favour?
• How is mechanical stability balanced against preservation of the blood supply?
• Which device class best matches the fracture pattern, bone quality, and soft-tissue condition?

Key concepts

• Reduction (open and closed)
• Absolute stability and interfragmentary compression
• Relative stability and bridging fixation
• Plates and screws
• Intramedullary nails
• External fixation
• Tension-band principle
• Working length and construct stiffness

Key theories

Absolute versus relative stability

Constructs that compress fracture fragments and eliminate interfragmentary motion produce direct bone healing without visible callus, whereas constructs that permit controlled micromotion produce callus-mediated (secondary) healing; the surgeon chooses the strategy to match the fracture.

Biological internal fixation

An approach that prioritises preservation of vascularity and the soft-tissue envelope, accepting relative stability and bridging constructs rather than extensive anatomical reconstruction, to reduce the biological cost of fixation.

Mechanisms

Fixation first restores alignment (reduction) and then holds the fragments in a defined mechanical state. Lag screws and compression plates produce interfragmentary compression and absolute stability, under which strain at the fracture site is low enough for direct (primary) bone remodelling without callus. Bridging plates, intramedullary nails, and external fixators provide relative stability, allowing controlled micromotion that stimulates callus formation (secondary healing). Because periosteal and endosteal blood supply is essential to healing, technique increasingly aims to deliver the chosen stability while minimising surgical disruption of vascularity — the biological internal fixation concept articulated by Perren.

Clinical relevance

Fracture fixation is one of the highest-volume areas of trauma surgery, and the principle of matching stability to biology informs how implants are designed and selected. As reference material this entry explains those principles; it does not provide implant selection or operative guidance for individual patients.

Evidence & guidelines

Operative principles in this area are codified in the AO/ASIF manuals and standard operative orthopaedic texts, supplemented by trials and registry data on specific implants and fracture patterns. Because implant technology evolves, device-specific recommendations change over time.

History

Systematic internal fixation was advanced by the AO/ASIF group founded in Switzerland in 1958, which standardised implants and the principle of anatomical reduction with rigid (absolute) stability. Over subsequent decades the emphasis shifted toward biologically oriented fixation that preserves vascularity and accepts relative stability where appropriate, a reorientation summarised in Perren's 2002 account of the scientific basis of biological internal fixation.

Debates

Anatomical rigid fixation versus biological bridging fixation

For many comminuted diaphyseal and metaphyseal fractures, extensive anatomical reconstruction with absolute stability competes with less invasive bridging constructs that preserve blood supply; the optimal balance depends on fracture pattern and remains a matter of operative judgement.

Key figures

• Stephan Perren
• Maurice Müller
• Martin Allgöwer
• Hans Willenegger

Seminal works

• perren-2002
• muller-1991
• ruedi-murphy-2007

Frequently asked questions

What is the difference between absolute and relative stability?

Absolute stability eliminates motion between fracture fragments (typically via compression) and allows direct bone healing without callus; relative stability permits controlled micromotion and heals through callus formation. The construct is chosen to match the fracture and the desired healing pathway.

What does 'biological internal fixation' mean?

It is an approach that prioritises preserving the bone's blood supply and surrounding soft tissue, often using bridging fixation and relative stability rather than extensive exposure and rigid anatomical reconstruction.