Development of a Stable Closed Femoral Fracture Model in Mice

Holstein, Joerg H.; Matthys, Romano; Histing, Tina; Becker, Steven C.; Fiedler, Martin; Garcia, Patric; Meier, Christoph; Pohlemann, Tim; Menger, Michael D.

doi:10.1016/j.jss.2008.02.042

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Volume 153, Issue 1 , Pages 71-75, 1 May 2009

Development of a Stable Closed Femoral Fracture Model in Mice

Joerg H. Holstein, M.D.
- Department of Trauma, Hand, and Reconstructive Surgery, University of Saarland, Homburg/Saar, Germany
- Institute for Clinical and Experimental Surgery, University of Saarland, Homburg/Saar, Germany
- To whom correspondence and reprint requests should be addressed at Department of Trauma, Hand and Reconstructive Surgery, University of Saarland, D-66421 Homburg/Saar, Germany
- These authors contributed equally to this article.
Romano Matthys
- AO Development Institute, Davos, Switzerland
- These authors contributed equally to this article.
Tina Histing, M.D.
- Department of Trauma, Hand, and Reconstructive Surgery, University of Saarland, Homburg/Saar, Germany
- Institute for Clinical and Experimental Surgery, University of Saarland, Homburg/Saar, Germany
Steven C. Becker
- Department of Trauma, Hand, and Reconstructive Surgery, University of Saarland, Homburg/Saar, Germany
- Institute for Clinical and Experimental Surgery, University of Saarland, Homburg/Saar, Germany
Martin Fiedler
- Department of Trauma, Hand, and Reconstructive Surgery, University of Saarland, Homburg/Saar, Germany
- Institute for Clinical and Experimental Surgery, University of Saarland, Homburg/Saar, Germany
Patric Garcia, M.D.
- Department of Trauma, Hand, and Reconstructive Surgery, University of Saarland, Homburg/Saar, Germany
- Institute for Clinical and Experimental Surgery, University of Saarland, Homburg/Saar, Germany
Christoph Meier, M.D.
- Institute for Clinical and Experimental Surgery, University of Saarland, Homburg/Saar, Germany
Tim Pohlemann, M.D.
- Department of Trauma, Hand, and Reconstructive Surgery, University of Saarland, Homburg/Saar, Germany
Michael D. Menger, M.D.
- Institute for Clinical and Experimental Surgery, University of Saarland, Homburg/Saar, Germany

Received 27 December 2007 published online 12 May 2008.

Background

Mice have become of increasing interest as experimental model for fracture studies. Due to their small size, most studies use simple pins for fracture stabilization, although insufficient rigidity of fixation critically affects fracture healing. Herein, we studied whether longitudinal fracture compression by an intramedullary screw represents a standardized, stable osteosynthesis technique in mice, and whether it may accelerate fracture healing.

Materials and methods

A micro-screw (MouseScrew) was constructed, allowing closed fracture stabilization without traumatizing surgery. Fracture stabilization was achieved by longitudinal compression, which was confirmed by biomechanical testing of osteotomized cadaver femora. Bone repair was analyzed histomorphometrically at 2 and 5 wk after surgery.

Results

Ex vivo analyses showed a significantly increased rotational and axial stiffness after screw stabilization (n = 8 each) compared with stabilization techniques using a conventional pin (n = 8 each) or a locking nail (n = 8 each). In the in vivo setting, 2 wk of screw stabilization (n = 8) demonstrated a significantly decreased fibrous tissue formation and an increased cartilage production compared with fractures stabilized by the locking nail (n = 8). After 5 wk callus consisted exclusively of bone in all animals studied without differences between the two stabilization techniques (n = 8 each).

Conclusions

Because prolonged fibrous tissue formation indicates delayed fracture healing, we conclude that the increased stability of the fracture by the use of our newly developed MouseScrew accelerates initial bone repair. Further, this fracture model may represent an ideal tool to study bone repair in mice under conditions of stable fixation.

Key Words: closed murine fracture model, intramedullary screw, fracture healing, biomechanical testing, histomorphometric analysis