Mechanical forces as predictors of healing during tibial lengthening by distraction osteogenesis

Direct axial loads were measured weekly during a 15% left tibial lengthening in 21 skeletally mature dogs using three in-line load cells mounted between the rings of an Ilizarov external fixator. The loads increased linearly over time to a maximum at the end of distraction (Week 4). The metaphyseal lengthening sites (mean, 155 N) generated significantly higher loads than diaphyseal sites (mean, 111 N). Stress was calculated by dividing measured load by the computed tomographic-measured cross-sectional area of each distraction osteogenesis site; the metaphyseal and diaphyseal groups demonstrated equal stress at each time point with a maximum of 47 N/cm2 at the end of distraction. Six premature consolidations occurred that demonstrated loads significantly greater than 200 N by Week 2 of distraction. Three nonunions occurred that had significantly lower loads measured by Week 3 of distraction (mean, 60 N or 26 N/cm2).