A new model to study healing of a complex femur fracture with concurrent soft tissue injury in sheep

Wullschleger, Martin E., Steck, Roland, Matthys, Romano, Webster, John D., Woodruff, Maria A., Epari, Devakar R., Ito, Keita and Schuetz, Michael A. (2013) A new model to study healing of a complex femur fracture with concurrent soft tissue injury in sheep. Open Journal of Orthopedics, 3 2: 62-68. doi:10.4236/ojo.2013.32012

Author Wullschleger, Martin E.
Steck, Roland
Matthys, Romano
Webster, John D.
Woodruff, Maria A.
Epari, Devakar R.
Ito, Keita
Schuetz, Michael A.
Title A new model to study healing of a complex femur fracture with concurrent soft tissue injury in sheep
Journal name Open Journal of Orthopedics   Check publisher's open access policy
ISSN 2164-3008
Publication date 2013-06
Sub-type Article (original research)
DOI 10.4236/ojo.2013.32012
Open Access Status DOI
Volume 3
Issue 2
Start page 62
End page 68
Total pages 7
Place of publication Irvine, CA, United States
Publisher Scientific Research Publishing
Collection year 2014
Language eng
Formatted abstract
High energy bone fractures resulting from impact trauma are often accompanied by subcutaneous soft tissue injuries, even if the skin remains intact. There is evidence that such closed soft tissue injuries affect the healing of bone fractures, and vice versa. Despite this knowledge, most impact trauma studies in animals have focussed on bone fractures or soft tissue trauma in isolation. However, given the simultaneous impact on both tissues a better understanding of the interaction between these two injuries is necessary to optimise clinical treatment. The aim of this study was therefore to develop a new experimental model and characterise, for the first time, the healing of a complex fracture with concurrent closed soft tissue trauma in sheep. A pendulum impact device was designed to deliver a defined and standardised impact to the distal thigh of sheep, causing a reproducible contusion injury to the subcutaneous soft tissues. In a subsequent procedure, a reproducible femoral butterfly fracture (AO C3-type) was created at the sheep’s femur, which was initially stabilised for 5 days by an external fixator construct to allow for soft tissue swelling to recede, and ultimately in a bridging construct using locking plates. The combined injuries were applied to twelve sheep and the healing observed for four or eight weeks (six animals per group) until sacrifice. The pendulum impact led to a moderate to severe circumferential soft tissue injury with significant bruising, haematomas and partial muscle disruptions. Posttraumatic measurements showed elevated intra-compartmental pressure and circulatory tissue breakdown markers, with recovery to normal, pre-injury values within four days. Clinically, no neurovascular deficiencies were observed. Bi-weekly radiological analysis of the healing fractures showed progressive callus healing over time, with the average number of callus bridges increasing from 0.4 at two weeks to 4.2 at eight weeks. Biomechanical testing after sacrifice showed in- creasing torsional stiffness between four and eight weeks healing time from 10% to 100%, and increasing ultimate torsional strength from 10% to 64% (relative to the contralateral control limb). Our results demonstrate the robust healing of a complex femur fracture in the presence of a severe soft tissue contusion injury in sheep and demonstrate the establishment of a clinically relevant experimental model, for research aimed at improving the treatment of bone fractures accompanied by closed soft tissue injuries.
Keyword Fracture
Large animal model
Soft tissue injury
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Non HERDC
School of Medicine Publications
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Created: Wed, 02 Apr 2014, 18:14:33 EST by Martin Wullschleger on behalf of Surgery - Royal Brisbane and Women's Hospital