DUAL-ENERGY X-RAY ABSORPTIOMETRY PREDICTS BONE-FORMATION IN LOWER-LIMB CALLOTASIS LENGTHENING

The rate of regenerate bone mineral content (BMC) acceleration was stu died using dual-energy X-ray absorptiometry (DEXA) in callotasis lengt hening of the lower limb. Eleven youngsters (age range 5-17 years) und ergoing callotasis lengthening for congenital, post-traumatic or post- infective conditions were studied longitudinally. Patients were initia lly scanned once a week until completion of the lengthening phase, and at 2-week intervals thereafter until removal of the fixator. They wer e subsequently followed up at regular intervals on an outpatient basis for up to 2 years after removal of the fixator (average, 14 months). The BMC accretion slopes exhibited by the patients and the rate of new bone formation allowed the identification of three groups. In the fas t formation group, the rate of new bone formation was 0.3-0.6% per day . In the moderate formation group the rate of new bone formation is 0. 1-0.3% per day, while in the poor formation group the rate of new bone formation is <0.1% per day. From the analysis of time graphs, a direc t correlation emerged between early bone formation and subsequent bone mineral content accretion. Measurement of BMC during callotasis lengt hening in the lower limb allows precise monitoring of the process. It may prove useful to prevent complications occurring after removal of t he fixator at an unduly early stage, such as plastic deformation and f racture through the regenerate bone. It may be used to predict the bon e formation rate in a given patient, and to implement measures to try to influence it.