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Scientific Articles   |    
A New Interpretation of the Mechanism of Ankle Fracture
Naoki Haraguchi, MD1; Robert S. Armiger, MSBME2
1 Department of Orthopaedic Surgery, West Tokyo Metropolitan Police Hospital, 4-8-1 Nishimotomachi, Kokubunji-shi, Tokyo 185-0023, Japan. E-mail address: naokihg@aol.com
2 Applied Physics Laboratory, The Johns Hopkins University, 11100 Johns Hopkins Road, Laurel, MD 20723-6099
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Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.
Investigation performed at the Department of Orthopaedic Surgery, The Johns Hopkins University, Baltimore, Maryland

The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2009 Apr 01;91(4):821-829. doi: 10.2106/JBJS.G.01288
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Abstract

Background: Researchers have found it difficult to recreate a Lauge-Hansen supination-external rotation-type ankle fracture in experimental settings. We hypothesized that a pronation-external rotation mechanism could cause both distal, short oblique and high fibular fractures and that the fracture type would be affected by associated, laterally directed forces applied to the foot.

Methlods: Twenty-three cadaver ankles were subjected to fracture loading that replicated the Lauge-Hansen pronation-external rotation mechanism with or without applying an external lateral force. In Phase I, an axial load was applied to fifteen specimens mounted on a materials testing machine. Each foot was rotated externally to failure. In Phase II, eight specimens were tested according to the Phase-I protocol, but external forces were applied laterally at the foot to increase the abduction moment at the ankle. Load and position versus time curves were recorded and were correlated with video image data to establish the sequence of failure of specific anatomic structures.

Results: Eight specimens tested in Phase I sustained an oblique fracture of the distal end of the fibula with both medial and posterior injuries that occurred after the fibular fracture. Increasing the external lateral force and hence the abduction moment within the ankle (Phase II) resulted in three of eight specimens sustaining a high fibular fracture with a reversed fracture line (anterosuperior to posteroinferior) and/or a comminuted high fibular fracture. The distribution of traditional pronation-external rotation-type fractures differed significantly between Phase I and Phase II (p = 0.032).

Conclusions: This study generated counterexamples to the Lauge-Hansen classification system by showing that a short oblique fracture of the distal end of the fibula can occur with the foot in the pronated position. Furthermore, a high fibular fracture was recreated by increasing the abduction moment at the ankle.

Clinical Relevance: The pattern of ankle fracture is related directly to the applied loads, including specifically the combination of the external rotational moment and the abduction moment. The results of the current study could provide the basis for a more straightforward classification of ankle fractures based on applied loads.

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    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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