Purpose of the study: The objective of this study was to establish an experimental sheep model for a surgical procedure which has been clinically successful for repairing major loss of bone stock: the Masquelet technique.
Material and methods: A 25 mm bone defect was created in a metatarsal bone then filled with a cement filler. After six weeks, the cement was removed after opening the neoformed pseudosynovial membrane. The cavity was left empty in group 1 (n=6) or filled with a morcelized cancellous autograft harvested from the iliac crests in group 1 (n=6).
Results: The surgery was well tolerated in all animals which were able to used the injured limb the day after the operation. Radiographic images and histological findings 24 weeks after surgery demonstrated that healing had not been achieved in all of the animals in group 1. Inversely, healing was achieved in all animals in group 2 at 24 weeks. Immunohistochemistry of the neoformed pseudosynovial demonstrated :
an abundant vascular network,
presence of cells expressing transcription factor CBFA1,
very few inflammatory CD14+ cells (macrophages),
an extracellular matrix positive for type I collagen.
Conclusion: The sheep metatarsal model is a model of critical size with low morbidity. This model could be used to:
evaluate new therapeutic strategies for bone regeneration in conditions close to clinical situations,
study the role of the membrane in bone repair.
The presence of a pseudosynovial membrane might:
be a barrier against the diffusion of bone morphogenetic proteins outside the lesion and
potentially be a reservoir of stem and vascular cells which could be useful for new technologies.
