A model for intramembranous ossification during fracture healing

J Orthop Res. 2002 Sep;20(5):1091-8. doi: 10.1016/S0736-0266(02)00017-7.


We have developed a method to study the molecular basis of intramembranous fracture healing. Unlike intramedullary rods that permit rotation of the fractured bone segments, our murine model relies on an external fixation device to provide stabilization. In this study we compare stabilized fracture callus tissues with callus tissues from non-stabilized fractures during the inflammatory, soft callus, hard callus, and remodeling stages of healing. Histological analyses indicate that stabilized fractures heal with virtually no evidence of cartilage whereas non-stabilized fractures produce abundant cartilage at the fracture site. Expression patterns of collagen type IIa (colIIa) and osteocalcin (oc) reveal that mesenchymal cells at the fracture site commit to either a chondrogenic or an osteogenic lineage during the earliest stages of healing. The mechanical environment influences this cell fate decision, since mesenchymal cells in a stabilized fracture express oc and fail to express colIIa. Future studies will use this murine model of intramembranous fracture healing to explore, at a molecular level, how the mechanical environment exerts its influence on healing of a fracture.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bone Remodeling / physiology
  • Bony Callus / pathology
  • Bony Callus / physiology*
  • Collagen Type II / genetics
  • Collagen Type II / metabolism
  • External Fixators
  • Fracture Fixation*
  • Fracture Healing / physiology*
  • In Situ Hybridization
  • Mice
  • Mice, Inbred Strains
  • Models, Animal
  • Osteocalcin / genetics
  • Osteocalcin / metabolism
  • Osteogenesis / physiology*
  • RNA, Messenger / metabolism


  • Collagen Type II
  • RNA, Messenger
  • Osteocalcin