In this study, 10 adult male dogs (15-25 kg) were used. The dogs were randomized into two groups. Lenghthening of 30 % of the left tibia was performed in each dog by callus distraction after osteotomy and application of an ilizarov fixator. Distraction was started at the seventh postoperative day with a distraction rate of 0.5 mm twice a day. Culture-expanded autologous MSCs and platelet-rich plasma (PRP) and PRP were injected into distraction callus at the misdle and the end of the distraction periods. At the end of the distraction period, ilizarov fixator was replaced by interlocking nail to allow consolidation periods as twice the lengthening period. The dogs were killed at the end of the consolidation phase. The tibia was removed from the distracted left leg and after tissue processing longitudinal sections were cut and stained with hematoxyline & eosin. Histologically the area of new bone trabeculation was more advanced for the MSCs/PRP group, with less intervening fibrovascular intermediate zone in the bony regenerate. These findings suggest that MSCs seems to be very effective in early bony consolidation in distraction osteogenesis. The use of MSCs may allow a shortened period of consolidation and therefore permit earlier device removal.

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