Evaluation of the extent of bone healing in mandibular distraction osteogenesis using pre-operative and post-operative imaging pixel value ratio: a cohort study.

BACKGROUND

The pixel value ratio (PVR) is a metric measured on X-ray images that has been used in many studies to assess the time of final external fixator removal. The aim of this study was to investigate the value and potential influencing factors of PVR in the early phase of mandible healing by distraction osteogenesis (DO) in Pierre Robin sequence.

METHODS

We performed a retrospective analysis on 342 Pierre Robin sequence patients with bilateral mandibular lengthening surgery, measured PVRs in the osteotomy position of children before surgery, and monitored PVRs in the early stage of bone regeneration at the 1st, 2nd, and 3rd month respectively after surgery. The potential effects of gender, weight, and age of fixation period were also analyzed.

RESULTS

PVRs before osteotomy and at the 1st, 2nd, and 3rd month afterward were 0.96±0.04 (R) and 0.97±0.05 (L); 0.4±0.1 (R) and 0.42±0.1 (L); 0.68±0.11 (R) and 0.71±0.11 (L); and 0.97±0.04 (R) and 0.98±0.04 (L), respectively, which had significant differences (P<0.001). We found no significant difference in PVRs by gender. In terms of age, there was a significant difference in PVRs between children aged less than 28 days and older than 120 days before surgery. There were also significant differences between those aged less than 28 days and older than 120 days, and children aged 8-28 days and 29-60 days at the 3rd month after surgery. In terms of weight, the PVRs of children with a birth weight less than 4 kg and those with an admission weight less than 2.5 kg were significantly different.

CONCLUSIONS

During the infancy period, the healing process of the mandibular DO focuses on the early healing phase (1-3 months). Our results showed that PVRs gradually increased during the first 3 months after mandibular osteotomy and during the process of DO. Gender had no effect on PVRs, whereas age, birth weight, and admission weight had a greater effect. The results of this study suggest that PVRs can be used as an indicator for the assessment of early lengthening bone growth in patients with mandibular lengthening and for determining whether to remove the distraction osteogenic apparatus.