Innovative Approach To Distraction Osteogenesis Using A Novel External Fixator Design. In Vivo Experimental Rabbit Model

Distraction osteogenesis, bone lengthening, is an established surgical technique for bone lengthening. The procedure involves making osteotomies, in the bone, and using a device to gradually separate, or “distract”, the bone fragments. New Zealand white male rabbits underwent distraction osteogenesis on the right tibia and lengthening by means of external fixators at two different time points ; a speed of 1.4 mm/day in 15 days and 2.1 mm/day in 10 days. The regenerated callus was carrefully removed and were subjected to biological and physicochemical analyses such as Scanning Electron Microscope (SEM), Fourier Transform Infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (RMN) analyses. For the period of five weeks, FTIR results showed that the mineral phases of the regenerated tissue of two groups were made up of biological apatite crystals, which are defined as a phosphocalcium carbonated. This IR spectra confirmed the presence of phosphate (PO ₄ ^-3 ), hydroxyl (OH)- and carbonate (CO ₃ ^-2 ) groups. NMR demonstrated that PO ₄ ^3- group of the regenerated bone has practically a homogeneous and unique environment: chain PO ₄ - PO ₄ which represents the skeleton of the bone mineralization. SEM showed that at the same period of elongation: endost appearance evolved to more homogeneous appearance similar to healthy bone. However, the fast-lengthening group presented less homogeneous appearance, and a less hard cortical tissue formation also, the haversian aspect was incomplete. Histological analyses demonstrated that ossification was taken place according to three modalities: endochondral, endoconjunctive and transchondroid. As conclusion, the bone rearrangement during rapid lengthening is delayed while for the slow lengthening group the regenerated bone is strongly ossified. The lamellae are organised into concentric circles, which surround a vertical Haversian canal.