Greater frequency of distraction accelerates bone formation in open-wedge proximal tibial osteotomy with hemicallotasis

BACKGROUND: In chickens, increased distraction frequency stimulates bone formation in distraction osteogenesis. PATIENTS AND METHODS: We investigated the effect of two different distraction frequencies on bone formation in the distracted portion, and on the time of removal of the fixator, in open-wedge osteotomies of the proximal tibia with hemicallotasis (HCO). The study included 20 consecutive patients (20 knees) who underwent HCO for medial osteoarthrosis of the knee. 10 knees were distracted at a rate of 0.25 mm four times a day (the 4-step group); and the other 10 knees were distracted at a rate of 0.125 mm eight times a day (the 8-step group). RESULTS: There were no significant differences in the preoperative FTAs or the correction angles between the two groups. At all intervals until 6 weeks after the completion of distraction, bone mineral density in the distraction gap was significantly higher in the 8-step group than in the 4-step group. The average time in external fixation was 78 (SD 5) days in the 8-step group as compared to 89 (SD 6) days in the 4-step group, a significantly shorter time. INTERPRETATION: Our findings indicate that an increase in the distraction frequency in HCO provides better bone formation, resulting in a shorter external fixation period.