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Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2013)

22.10. - 25.10.2013, Berlin

The role of mechanical strains in callus tissue patterning during large bone defect healing

Meeting Abstract

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  • presenting/speaker Sara Checa - Julius Wolff Institut, Charité - Universitätsmedizin Berlin, Berlin, Germany
  • Georg N. Duda - Julius Wolff Institut, Charité - Universitätsmedizin Berlin, Berlin, Germany

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2013). Berlin, 22.-25.10.2013. Düsseldorf: German Medical Science GMS Publishing House; 2013. DocIN22-371

doi: 10.3205/13dkou011, urn:nbn:de:0183-13dkou0118

Published: October 23, 2013

© 2013 Checa et al.
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Outline

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Objective: Mechanical constraints influence bone healing. Using computer models, ranges beneficial for the formation of bone have been identified. Although, non-union cases are of most clinical relevance, most studies have concentrated on uneventful healing conditions.

It remains unknown whether the local mechanical signals in the callus region influence healing in large bone defects or whether alterations in biological aspects overwrite the influence of mechanics. The aim of this study was to investigate whether the mechanical conditions within the gap region can explain the specific tissue patterns observed during healing in a large bone defect.

Methods: 2D axisymmetric finite element models of an osteotomy leading to uneventful healing (1 mm gap) and non-union (5 mm gap) in the rat femur were developed. The finite element models represented the healing situation immediately after surgery. Histological images were used to compare the local mechanical signals with tissue patterning.

Results and conclusion: The hydrostatic pressure distribution resembled the closure of the medullary canal. Figure 1 [Fig. 1]

While in the 1 mm gap model large hydrostatic pressures were present in the whole gap region, the same level of hydrostatic pressure was only present close to the cortical ends and closing the medullary canal in the 5 mm gap model. Interestingly, although in the gap region, minimum principal strain levels were lower in the large compared to the normal size defect; in the periosteal region, minimum principal strain levels were independent of gap size. Experimentally, in this region, intramembraneous ossification occurs in both animal models.

Large bone defect healing is clinically highly relevant. As a treatment strategy, tissue engineering techniques based on scaffolds are currently being investigated. Among other factors, those strategies are currently limited by a lack of understanding of how the local mechanical conditions influence the healing process in such compromised conditions. We have shown that tissue patterning relates to the local mechanical conditions within the callus. The knowledge gained from these studies will be used in the future for the design of scaffolds to promote regeneration.