The treatment of segmental defects of long bones is one of the most difficult problems in traumatology. Distraction osteogenesis principals pionored in 1951 year by Dr. Ilizarov has a gained major popularity in the world.

In this experimental study, bifocal distraction osteogenesis (Group-1) was compared with monofocal distraction osteogenesis (Group-2) in dogs. Fourteen dogs were divided into two equal groups: In both groups, a two- centimeter-long segment of bone was resected from the diaphysis of the left tibial shaft. In group-1, proximal corticotomy was applied by preserving distal bone segmental defect. In the second group, the segmental defect was immediately closed. Bone transport and distraction were performed at 0.5 mm rate every 12 hours for 20 days after a latency period of 7 days. All cases were euthanized at 87^th day.

Results were evaluated with clinical, radiographical, and histological examinations. Clinically; distraction applications in group-2 was performed more easier than that of bone transport in group-1.

Radiographical and histopathologic evaluations were made according to the criteria described by Helple et al. and Lane et al. Statistical analysis was performed using Mann-Whitney U test. Radiographical and histopathological examinations revaled that there was not a statistically significant difference between the proximal area of groups 1 and 2 (p>0.05), whereas significant difference (p<0.01) was observed between the distal area of group 1 and group 2.

In conclusion, bone segmental defects up to 2 cm of the tibia can be successfully completed through both distraction osteogenesis taking into account an additional operation and inability of distal union in bifocal distraction osteogenesis and prematur bone consolidation in monofocal distraction osteogenesis in dogs