下肢旋转角度对髋部骨密度测量的影响

目的通过对下肢不同旋转角度下的髋部骨密度(bonemineraldensity,BMD)的测量,了解下肢旋转角度的变化对髋部BMD测量的影响。方法选择40例女性,平均年龄60.7岁(45～85岁),平均身高161.8cm(150～175cm),平均体重67.4kg(48～80kg)。进行机器质量控制后,在下肢中立位、15°内旋、30°内旋状态下分别测量髋部BMD,每一角度测量后,均要求受试者下测量床,然后再重新上测量床摆体位。分析比较不同旋转角度下的髋部BMD变化。结果随着下肢旋转角度的改变,髋部BMD测量值均有明显的变化。其中在Ward's三角区域和股骨粗隆区域的BMD变化明显大于股骨颈BMD改变。从中立位到15°内旋及15°内旋到30°内旋时,股骨颈、Ward's三角和股骨粗隆BMD值均有显著变化(P<0.01)。而从中立位到30°内旋时,髋部BMD值增高,但其相关系数较低(r=0.36～0.4,P>0.05)。结论髋部BMD测量的精度明显受下肢旋转角度变化的影响;富含松质骨区域的BMD改变更易受下肢旋转角度变化的影响;良好的测量前定位和下肢固定,对提高髋部测量精度具有重要意义。

Effect of femoral rotation on hip bone mineral density measurement

OBJECTIVE: To measure hip bone mineral density (BMD) on different femoral rotations and to identify the influence of femoral rotation during hip densitometry. METHODS: Forty women were recruited at the out-department of orthopedic, with the average age of 60.7 years (45-85 years), the average height of 161.8 cm (150-175 cm), and the average weight of 67.4 kg (48-80 kg). BMD measurement of hip was done in neutral position (0 degrees), 15 degrees and 30 degrees of internal rotation under quality control of DXA machine. All the subjects were asked to get down scan table and reposition after each measuring in different rotation. RESULTS: Hip BMD of proximal femur (femoral neck, Ward's area and trochanter region) have significant variations in measurement (P < 0.01) among neutral position, 15 degrees and 30 degrees of internal rotation. There were more BMD change at the cancellous region (Ward's triangle and trochanter region) than at cortical bone area (femoral neck region). Statistical analysis showed a significant positive correlation for hip BMD change between neutral degrees to 15 degrees of internal rotation and 15 degrees to 30 degrees of internal rotation. But no correlation between neutral degrees to 30 degrees of internal rotation for hip BMD change. CONCLUSIONS: Femoral rotation was shown to have a significant effect on hip BMD measurements. Cortical bone region of hip have a less BMD change than cancellous bone region. Proper positioning of the femur during scan can improve precision significantly.