Abstract:

Background

The proximal humerus is a common site for osteoporotic fractures.The measurement of bone mineral density （BMD） of the proximal humerus is essential for the diagnosis and evaluation of the therapeutic effect of osteoporosis.Dual-energy X-ray Absorptiometry （DXA） is the gold standard for the diagnosis of osteoporosis， but there is no clear threshold for the diagnosis of proximal humerus osteoporosis.Quantitative Computed Tomography （QCT） measures bone trabeculae's volumetric BMD on a two-dimensional CT cross-section.However， when QCT is used to measure BMD， a calibrated body model is required to obtain the lumbar vertebra's bone mineral content （BMC）.However， this body model cannot be used for bone mineral density measurement of the humerus， and this method cannot be used for retrospective bone mineral density measurement.As an advanced technology， Dual-energy Computed Tomography （DECT） has been widely applied in clinical practice， such as virtual noncalcium （VNCa）reconstruction algorithm.It has been used to analyze substances such as iron， calcium， and fat quantitatively.The single energy reconstruction algorithm of energy spectrum purification can also evaluate shoulder joint ligament and rotator cuff structure morphology and continuity.

Objective

To investigate the feasibility of measuring the cortical thickness of the proximal humerus in predicting the local bone mineral density of the proximal humerus combined with the quantitative bone mineral density measurement method of the upper humerus.

Methods

A total of 65 patients （mean age 49.5±15.2 years old， male： female =32：33， right：left=30：35） were included in the retrospective study of shoulder joint orthographic radiographs and dualsource CT images of trauma patients from Shanghai First People's Hospital.Cortical bone thickness （CBT）of the proximal humerus was measured on the program and reconstructed coronal CT images， and the mean value of the cortical index （CBTavg） and the standard value of the cortical index （CBTg） was calculated.The dual-energy CT data of the shoulder joint were imported into Syngo.via post-processing workstation and the middle plane between the greater tubercle plane of the humerus and the surgical neck was taken as the reference plane.The two ends of the articular surface of the humerus head were connected as vertical bisector lines， thus dividing the humeral head into four parts.The relative CT values of calcium （CaCT） and the regular CT value （rCT） between the four components were measured.The correlation between CaCT， rCT， CBTavg， and CBTg was studied.

Results

The average CBTavg-_Xray was （0.6±0.11）cm， and the average CBTavg-_DECT was （0.74±0.11）cm.There were statistical differences between CBTavg-_Xray and CBTavg-_DECT and CBTg-_Xray and CBTg-_DECT （P＜0.001）.There was a correlation between CBTavg-_Xray and CBTavg-_DECT and CBTg_-Xray and CBTg-_DECT.r values were 0.679 and 0.747，respectively， and P values were all ＜ 0.001.CBTavg-_Xray， CBTg-_Xray， CBTavg-_DECT， and CBTg-_DECT were not strongly correlated with CaCT and rCT values in regions 1-4 （r values were all ＜ 0.6）.

Conclusion

The cortical thickness of the proximal humerus had a poor correlation with the bone calcium value of the proximal humerus， so it could not accurately predict the bone calcium value of the proximal humerus.The CaCT and rCT values of the proximal humerus can be measured by dual-energy CT to guide the surgeon in selecting the appropriate internal fixation area.

Key words: Dual-energy CT, Proximal humerus, Cortical bone thickness, Bone mineral density