Objectives: This study was designed to investigate the morphology, thickness and cellularity of the growth plate during callus distraction performed in the immediate vicinity of the growth plate.
Methods: Lengthening of the right tibia by 25% was carried out on 24 beagle dogs by callus distraction. Distraction was started at the fifth postoperative day with a distraction rate of 0.5 mm twice a day. A control group of six dogs underwent tibial osteotomy and external fixation without distraction. Half of the dogs of both groups were sacrificed at the end of the distraction phase of 25 days (Group A) and the remaining 15 dogs after an additional consolidation period of 25 days (Group B). The tibia and femur was removed from the distracted right leg and from the left control side of each animal and longitudinal sections were cut and stained with Pentachrome. The thickness and cellularity of the regeneration zone, the proliferation zone and the hypertrophic zone were determined for the proximal tibial and the distal femoral epiphysis.
Results: During the distraction phase the thickness of the proximal tibial growth plate and its cellularity were reduced on the distraction side. During the consolidation phase there was a slight recovery in the proximal tibial growth plate.
Conclusions: Callus distraction leads to a temporary reduction in growth of the affected physis.