Healing of rabbit tibial fractures using external fixation. Effects of removal of the fixation device.

Bone healing after external fixation of rabbit tibial osteotomies was studied in order to throw light on the problem of the optimal time for removal of external fixation. The animals were divided into various groups according to different periods of time for removal of external fixation and sacrifice. The strength and stiffness of the healing bones at 12 weeks were greater in tibiae where the external fixator was removed at 4, 6 or 9 weeks than in those with the continuous presence of the fixator for 12 weeks. Although fixation is essential in the early healing period, it seems that bone healing is stimulated by the removal of the fixation after a certain period of time. The optimum time for removal of external fixation in the rabbit tibia was at 6 weeks of healing, when the bone had regained normal stiffness and about 50 per cent of normal strength. The clinical relevance of this investigation is that it might be rational to remove the external fixator before bone healing has been completed. If it is felt that healing is not secure when the fixator is removed, a tibial brace might subsequently be used for a short period.