Abstract
BACKGROUND: Distraction osteogenesis (DO) enables gradual bone elongation through controlled osteotomy and distraction. Existing radiographic and index-based assessments face limitations. Callus pattern classification offers predictive value, but its early applicability across age groups and gap lengths remains unclear. METHODS: We retrospectively reviewed 129 patients (155 bone segments) who underwent lower limb DO between 2003 and 2023. Patients had a mean age of 37.3 years (5.6-77). The mean distraction length was 53.2 mm (11-174). Radiographs were graded monthly using modified Li classification, depicting two callus consolidation routes: Route 1 (no presence of type 5/8) and Route 2 (presence of type 5/8). Patients were stratified by age (younger: < 25 years; middle: 25-49 years; older: ≥ 50 years) and distraction length (shorter: < 5 cm; longer: ≥ 5 cm). Outcome measures included parameters such as distraction-consolidation time (DCT), healing index (HI), etc., compared by Mann-Whitney test and analysis of variance. Trends of radiographic progress were analyzed by Loess regression. RESULTS: Route 1 demonstrated favorable healing with significantly lower DCT (300.4 vs 381.6 days; p = 0.002) and HI (70.1 vs 89.1 days/cm; p = 0.021). Younger age patients showed negligible differences between two routes. However, middle and older age groups showed delayed consolidation in Route 2, particularly from the high-intermediate callus density grades, Li classification type 6 and 7, onward (p < 0.05). Long distraction gaps further amplified route-based divergence in the trajectory of consolidation. CONCLUSION: Evolution of callus patterns closely correlate with outcomes of DO. Negative patterns (types 5/8) are associated with delayed healing, particularly in older patients and those with longer distraction lengths. These findings support their use as a timely marker for risk stratification and suggest heightened surveillance or protocol adjustment, such as slowdown of distraction, cyclic distraction-compression dynamization, or additional fixation methods, to optimize outcomes. LEVEL OF EVIDENCE: Level III, retrospective cohort study.