Distraction Osteogenesis in the Combined and Sequential Use of Transosseous and Intramedullary Osteosynthesis: Experimental Study

Background. The methods of “lengthening over the nail” (LON) and the sequential use of the external fixation and nailing in the option “lengthening and then the nail” (LATN) are characterized by ignoring non-observance of the formulated by G.A. Ilizarov is the most important condition for optimizing the osteogenesis process, namely, the preservation of medullary blood supply and osteogenic bone marrow tissue. At the same time, in clinical practice, there was no negative effect of the intramedullary nail on the formation of the regenerate. In experimental studies, the activation of periosteal bone formation during LON is noted. But the active periosteal bone formation detected in clinical practice with a sequential technique has not been confirmed by experimental studies.

The aim of the study was to compare the organotypical rebuilding of the distraction regenerate during tibial lengthening in rabbits according to Ilizarov, over the intramedullary fixator and with the sequential use of the external fixation and nailing.

Materials and Methods. The study was carried out on 54 mature rabbits of the Soviet Chinchilla breed, which were divided into 3 groups of 18 animals. In Gr-1 (control), the tibia was lengthened by 1 cm in a mini-Ilizarov apparatus at a rate of 1 mm per day for 4 sessions step. In Gr-2, the LATN technique was modeled. After the end of lengthening, an intramedullary fixator was implanted installed, the apparatus with the presence of wires only in the base supports was kept as an imitation of blocking the intramedullary fixator. In Gr-3, lengthening was performed over the intramedullary fixator; at the end of lengthening, the wires were left only in the base supports. The fixation period was is 30 days. The total duration of the experiment is 45 days. On the 10th, 15th, 20th, 30th, 45th day X-ray, CT and morphological studies were performed during the experiment.

Results. In the experimental groups, a more pronounced periosteal bone formation in the area of regenerates was noted, while in Gr-3 (LON) cortical plates were formed mainly from the periosteal component, and in Gr-2 (LATN) wide cortical plates were formed from the intermediate and periosteal areas. In this group, the maximum densitometric density values are noted. Endosteal bone formation was preserved in all groups.

Conclusion. The LON and LATN techniques, when compared with the classical Ilizarov lengthening, do not demonstrate any deficiency in the organotypical rebuilding of the bone tissue of the regenerates. All zones of bone formation are present, including endosteal, with intense periosteal bone formation. The most powerful bone structures are formed with the sequential use of the external fixation and nailing (LATN) in the form of the formation of wide cortical plates due to the intermediate and periosteal zones of the regenerate.