Ultrasonographic appearance of regenerate bone in limb lengthening.

The appearance of regenerate bone during the process of limb lengthening using a mono-axial device was studied using radiographs and ultrasound scanning in nine patients. The corticotomy site initially appeared as a sonolucent area. Poorly organized echogenic foci were detectable 2 weeks after the distraction was begun. After 4 weeks, these areas became aligned. At 7-8 weeks, a clear impression of a new cortical margin was seen. The formation of a medullary canal started at this point, progressing to a radiographically evident canal. Ultrasound scanning can reduce considerably exposure to ionising radiation in patients undergoing limb lengthening. Accurate measurements are possible in the early stages, and ossification can be monitored. Axial deviation can be seen but not evaluated. The maturity of the regenerate bone still has to be assessed clinically.