The effects of mechanical immobilization on sutural development in the growing rabbit

Methyl-2-cyanoacrylate was used to mechanically immobilize the coronal suture unilaterally in a series of New Zealand white rabbits at varying ages. The animals were separated into groups; some were sacrificed at 30 day and some at 60 days postoperatively. Amalgam markers were placed in the parietal and frontal bones across the coronal suture, and were measured immediately after surgery and at the time of sacrifice to confirm mechanical immobility. The animals were studied radiographically and histologically in order to document the presence or absence of sutural bone union. Based on the results of this study, it appears that immobilization of the coronal suture results in the formation of an ectocranial periosteal bone bridge in rabbits less than 8 weeks of age. Bone union was not found in animals older than 8 weeks of age. This age-related difference in response is believed to be due to decreased periosteal depository activity on the ectocranial surface of the calvaria once the brain ceases to expand actively. Furthermore, bone union or synostosis was never seen within or across the internal portion of the sutural ligament. It is suggested, therefore, that sutural immobilization at young ages in the rabbit does not result in sutural synostosis and that the term "periosteal bone bridge" should be used when referring to this biological response.