Correlation between ultrasound imaging and mechanical and physical properties of lengthened bone: an experimental study in a canine model.

The right tibias of 16 adult mongrel dogs were lengthened 2.5 cm using a uniplanar lengthening device (Orthofix). After the animals were killed in groups of 4 at 3, 6, 9, and 12 weeks postlengthening, ultrasound imaging and mechanical and physical testing was performed. There was a direct relationship between the percentage of intact cortices on ultrasound imaging and the mechanical and physical properties of lengthened bone. However, once 80-90% of all the cortices regained their continuity, the strength of the lengthened bone was only 50-60% that of the control. Ultrasound imaging, therefore, may be useful in predicting the mechanical and physical properties of lengthened bone in the early phases of limb lengthening. Once all the cortices become continuous, however, another method for assessment of the mechanical properties of lengthened bone should be used.