AO Philosophy and Evolution

AO development

In 1958 a small group of Swiss surgeons founded the AO (Arbeitsgemeinschaft für Osteosynthesefragen/Association for the Study of Internal Fixation) to improve the care of patients with musculoskeletal injuries. Even though the value of operative fracture fixation had been recognized earlier, implementation and acceptance were difficult at the time. Albin Lambotte introduced stable internal fixation options, while Gehard Küntscher advanced intramedullary nailing, and the value of traction and motion was emphasized by Lorenz Böhler. 

Inspired by the concepts in operative fracture fixation, the early AO group with Maurice E. Müller, Martin Allgöwer, Robert Schneider, and Hans Willenegger were determined to apply them clinically. Surgical innovation, technical development, basic research, and teaching evolved to improve functional outcome after musculoskeletal injuries. Their determination in writing and teaching progressed to a worldwide organization—the AO Foundation.

Original AO principles 

The understanding of patients and fracture factors influencing fracture management remains the key concept until today. The original management objectives were:

  1. Restoration of anatomy
  2. Stable fracture fixation
  3. Preservation of blood supply
  4. Early mobilization of the limb and patient

These concepts were adapted slightly to the increased understanding of soft-tissue problems. The differentiation between absolute and relative fracture fixation have also evolved over the past decades. Absolute stability remains the treatment goals in articular fractures, but relative stability is often the preferred option in multifragmentary diaphyseal fractures. Simple diaphyseal fractures treatment should result in anatomic restoration. 

Fig 1 1

Early AO Course (1960) with Maurice Müller instructing.

 Today's AO principles

The key concepts today are remarkably similar to the early AO publications from 1962. Minimal access surgery, computer-aided navigation and internal fixators evolved and contributed to new treatment options, but biology will always stay the same. The new principles include:

  1. Fracture reduction and fixation to restore anatomical relationships
  2. Fracture fixation providing absolute or relative stability as the "personality" of the fracture, the patient, and the injury requires
  3. Preservation of the blood supply to soft tissues and bone by gentle reduction techniques and careful handling
  4. Early and safe mobilization and rehabilitation of the injured part and the patient as a whole

Available learning resources

Recorded lectures—requires Flash Player plug-in

video violation of ao principles  Violation of AO principles.
Lecturer: Suthorn Bavonratanavech.
Duration: 11:45 minutes.
Level of knowledge: Intermediate.

Webinar—requires Flash Player plug-in

webinar aotrauma QandA All you have ever wanted to know about AOTrauma and were afraid to ask
Consultants: Nikolaus Renner, Claude Martin
Duration: 01: 08 hours.
Level of knowledge: Basic.

Suggested readings

Rüedi TP, Buckley RE, Moran CG. AO Principles of Fracture Management. 2nd ed. Stuttgart New York: Georg Thieme Verlag; 2007.

Wagner M, Frigg R. AO Manual of Fracture Management Stuttgart and New York: Georg Thieme Verlag; 2006.

Please note that AOTrauma members have free access to the e-Book of the AO Manual of Fracture Management in the member-restricted areas of the AO Trauma Website. In case of further questions please contact

Schlich T. Surgery, Science and Industry: A Revolution in Fracture Care, 1950s - 1990s. Hampshire New York: Palgrave Macmillan; 2002