Does The Lengthening Frequency Affect The Outcome of Distraction Osteogenesis? Comparing Two Times a Day with Four Times a Day Lengthening Protocol

Objective: Distraction osteogenesis (DO) is a well-known technique. The traditional method utilized the lengthening frequency of four times a day (QID). Many mechanical factors may affect the DO outcome. However, the effect of distraction frequency has not been proven clinically. Therefore, we aim to investigate whether the BID and QID lengthening frequency affect the healing index and complications of the DO. Materials and Methods: We retrospectively reviewed patients who had undergone DO from 2010 – 2021. The patient was divided into BID and QID groups. Demographics, lengthening outcomes, and complications between the two groups were compared. We used the inverse probability of treatment weighting (IPTW) to determine the effect of treatment. Results: The median healing index (HI) of the patients whose lengthening was done QID is 41.36 (IQR 32.72 - 67.68) days/cm, and BID is 49.12 (IQR 35.28 - 62.54) days/cm, which did not differ significantly. The Odds ratio of achieving HI < 45 days/cm for patients receiving QID lengthening compare to BID is 1.12 (95% CI 0.31-3.99, p = 0.862 ). The IPTW did not show a difference in average treatment effects between QID and BID lengthening. The rates of minor and major complications were not significantly different between the two groups (26.1% in QID group and 32.1% in BID group). Conclusion: The frequency of QID and BID lengthening results in comparable HI and complications for patients who undergo DO. However, prospective research is needed to evaluate the effect of frequency differences in a clinical setting.