GUIDED TISSUE REGENERATION IN LONG BONES USING BIOLOGICAL MEMBRANES

Abstract

Purpose: To assess the use of abdominal aorta cryopreserved allografts as guided regeneration membranes in long bone defects.

Materials and methods: This is a prospective randomized blind study of 10 White New Zealand rabbits. 10 mm-long diaphyseal defects were created in both radii: on one side the defect was separated from the surrounding tissue by means of a tube-shaped cryopreserved aortic allograft; the contralateral radius (control) was left to develop spontaneously with no membrane. The animals were put down after 6, 12, 24 and 30 months. A whole range of different studies were made: x-rays, CT, MRI, morphodensitometric techniques and optical and electronic microscopy.

Results: No complete bone regeneration was observed in any of the controls. In 9 out of the 10 defects for which an aortic allograft was used complete bone regeneration was achieved as well as a restoration of continuity with a corticomedullary pattern. A progressive increase in density and thickness was observed in the regenerated cortex, which reached values similar to those of normal bone. A gradual reduction of the medullary/cortical thickness index was also detected.

Discussion: The microscopic images taken suggest that cryopreserved arterial allografts used in guided regeneration behave like barrier membranes and as osteoinductive agents because of the osteoblastic differenciation of endothelial and/or muscular cells and/or ossification secondary to proteic changes in the extracellular matrix of the artery. This could be regarded as the application of artery calcification and ossification (usually associated with arteriosclerosis, ageing, diabetes and renal failure) to the regeneration of bone defects.

Conclusions: It is possible to use cryopreserved aortic allografts as osteostimulating membranes in the guided regeneration of bone defects.