双能量X线骨质密度测量仪监测小儿下肢骨延长骨矿物质的变化

目的　在儿童骨延长的患儿中 ,为了能够有效地控制骨延长的速率 ,达到骨延长的目的 ,采用双能量X线骨质密度测量仪 (dualenergyX Rayabsorptiometry ,DEXA)监测延长断端骨矿含量 (bonemineralcontent,BMC)的变化。方法　 30例患儿中有 5 0处下肢作了骨延长术 ,平均年龄10 .9岁 (5～ 17岁 ) ,引起短肢的病因不同。术后 7～ 10d开始行骨延长 ,每次延长 0 .2 5mm ,每天 4次。牵引延长期间每周扫描一次 ,拆除外固定器后每 2周扫描一次到术后 2年。DEXA扫描的分辨率是 1mm× 1mm ,扫描速度 30mm/s。比较不同延长时期中骨矿含量的变化。分析不同病因和不同外固定器之间骨矿含量变化的差别。结果　不同固定器之间骨矿含量的差别无著性意义。根据骨延长区BMC增加速率 ,将患儿分为快速组、一般组和慢速组。快速组每日BMC增加速率为 0 .3%～ 0 .6 % ,新骨生长快速 ;一般组每日BMC增加 0 .1%～ 0 .3% ,新骨中速生长 ;慢速组每日增加 <0 .1% ,新骨生成缓慢。骨矿化速率与原发病因相关。结论　DEXA能动态监测骨延长中新生骨的骨矿含量的变化 ,根据骨矿含量变化的程度 ,能够调整骨延长的速率 ,从而达到预期骨延长的目的。

Dual energy X-ray absorptiometry monitor bone mineralization in lower limb lengthening of children

Objective To monitor the rate of bone mineral content (BMC) accretion of the bone regenerate in callotasis lengthening of the lower limb of children with dual energy X ray absorptiometry (DEXA).Methods Thirty patients with a total of 50 limb segments were studied. The average age was 10.9 years (ranged from 5 to 17 years). Distraction lengthening was applied 7 to 10 days after the initial corticotomy at the average rate of 0.25 ?mm four times daily. All limb segments were scanned longitudinally with DEXA. The BMC changes of the callotasis gap and the original bone adjacent to the gap were monitored and compared with controls taken from the contralateral limb. BMC changes were recorded as absolute changes and percentage changes of the original pre lengthened bone segment in different phases including the pre lengthening phase, the lengthening phase, the consolidation phase and after the frame removal for up to 2 years.Results There were no statistically significant differences in BMC of the distraction gap between the Ilizarov and Orthofix fixators groups. On the rate of bone mineralization, three groups of results can be identified. The first group had fast increase in the gap BMC at a rate of 0.3 to 0.6 % per day in the lengthening phase with a corresponding slower and mild decrease in the BMC of the original bone. The second group showed intermediate changes and the distraction gap increased its bone mineral content at a rate of 0.1 to 0.3% per day. The third group had very slow increase in the gap BMC of < 0.1% per day and an associated rapid and significant drop of the BMC of the original bone. It appeared that the primary etiology and age had a most significant effect on the bone mineral accretion in callotasis.Conclusion DEXA can help to monitor quantitatively the progress of the regenerated bone during distraction lengthening in children and assist in adjusting the distraction rate and time of removal of the external fixator.