Experimental studies on the effect of osteotomy technique on the bone regeneration in distraction osteogenesis.

The objective of the experiment was to study the effect of osteotomy technique on the course of bone regeneration in distraction osteogenesis in sheep. Thirty five merino sheep were divided into 5 groups of 7 sheep each, depending on the osteotomy technique: subcutaneous corticotomy, open corticotomy, Cattaneo corticotomy, open osteotomy and osteoclasia. Formation of regenerate and its remodeling was assessed, based on roentgenograms and morphological examination (bone sections, histological evaluation, SEM, superficial X-ray analysis). Irrespective from the osteotomy technique applied, in all experimental groups, regenerates filling the distraction gap were obtained. Analysis of bone sections and histological slides indicated the most advanced osteogenesis processes in the osteoclasia group. SEM examination and X-ray microanalysis confirmed not only the presence of mature bone tissue structures in this group, but also showed a mineralization close to that of a healthy bone. Osteogenesis was the slowest in the group of subcutaneous corticotomy. The observed histological picture and analysis of elemental composition indicate a normal course of distraction osteogenesis in this group, but its consecutive phases proceed with a certain delay, compared to the remaining groups. With a good deal of caution, it can be assumed that the delay of osteogenesis in the group of subcutaneous corticotomy in the 14th post-operative week was ca. 3 weeks compared to the osteoclasia group. In all experimental groups, few cartilaginous nodules were observed in regenerates 5 weeks and, in few cases, 9 weeks old. Ossification in such places was indirect, cartilage-based. In the remaining regions direct, membrane-based ossification prevailed. Direct apposition bone lamellae on islands of fibrous bone tissue was observed in regenerates aged 9 and 14 weeks, especially in periosteal regions. The intensity and rate of formation of new bone tissue varied between the experimental groups, based on roentgenological analysis and histological evaluation. Complex morphological studies on the course of regeneration in sheep showed the most advanced remodeling and mineralization of bone tissue in animals subject to osteoclasia.