| Reserch backgroundIntertrochanteric femoral fracture occurs from the base of femoral neck to small protuberance level. It is predilection in the elderly, more osteoporosis-related. As the society ages, the incidence of fractures is rising year by year. As the conservative treatment of intertrochanteric fractures has many complications, during the 20th century 60s, the AO/ASIF school of the rises, internal fixation of intertrochanteric fractures has become the preferred treatment. With the constant improvement of internal fixation devices, intramedullary fixation system from the Gamma nail, PFN developed to PFNA.SYNTHES company produced AO anti-rotation-type proximal femoral nail (PFNA) for osteoporosis in elderly patients, can effectively improve the stability of and well to prevent rotation and collapse, and a marked increase in anti-cut out of the region, have a greater advantage for patients with osteoporosis. But with the ongoing clinical and found that the proximal diameter and larger, frequently leading to surgery in the proximal femur in patients with splitting, resulting in surgical failure. Thus, South Korea, Japan and China, some scholars PFNA proximal diameter of 17mm questioned the suitability of such specifications PFNA Asian populations. For the design of Asian-type PFNA, it is necessary to study the Anatomic of proximal femoral medullary cavity of Asia.In foreign countries people study by Measurement of specimens, X-ray CT or MRI. Measurement of specimens is restricted by the quantity of specimens, and the cost is high. Although X-ray measurement is easy to carryout, during the process of X-ray film,due to the impact of many factors, it is difficult to-get the standard lateral X-ray film wllich can be used to comparable analysis.In addition, because the boundary between cortical bone and cancellous bone in X-ray film is uncertainty, which will also affect the accuracy measurement of the medullary cavity of proximal femoral.And CT,MRI was arranged in two-dimensional layer-by-layer images, anatomical landmark is not clear, which often miss some important information.The technology of Three-dimensional digital reconstruction can reconstruct the original space from two-dimensional layer-by-layer images,and show objects in three-dimensional images.This method is missing less information, and the object can be observe from any angle and direction. Thus digital technology can provide a new idea and technique for the proximal femoral medullary cavity study. This subject is the rear to carry out digital three-dimensional reconstruction of CT image data, and apply the computer software tools for measuring it. At the same time, the use of PFNA data provided by SYNTHES, PFNA reconstructed patterns, simulated surgical steps to import it into reconstructed proximal femur in computer, proximal femur was observed match up with our sexual relationship.Object1,Based on normal adult proximal femur CT image data, using three-dimensional reconstruction of digital technology, reconstruct proximal femur in the software of MimiCS10.0, measure anatomical data of proximal femoral medullary cavity and then describe the morphological characteristics of proximal femoral medullary cavity.2,Analysis the relevance of height, gender, age with the diameter of femoral medullary cavity, and compare the measured data with foreign-related data, analyze morphological features of proximal femoral people.3,To explore the matching relationship of proximal femur of Chinese and PFNA produced by SYNTHES, and recommend appropriate program for the preliminary design of the PFNA for Chinese people.Method1. Subjects and Image Acquisition1.1 Experimental Data From July 2008 to September 2009, at the Southen Hospital,120 cases were selected in 189 patients with CT examination of hip joints, including 55 male cases,65 female cases., Excluding the femur lesion,unilateral femoral were choose into analyze. Age from 16 to 86 years, mean 46 years old; height 147cm～185cm, males 158cm～185cm, an average of 170.7cm, female height 147cm～169cm, an average of 159.7cm.1.2 Device Hardware:GE's 16-row CT. Software:3D modeling software mimics1.3 Scanning Requirements Patients with supine on the CT bed central, rotating pairs of lower limbs to take a neutral position. The ambit is 10cm from the centrage of the joint space. Scanning condition:120kV,300mAs, Scanning parallleters:the width of collimating device is 0.75mm;thickness is 0.75mm;slice thickness is 0.625mm;the Pitch is 0.75mm.The time of scanning one slice is 200ms;the total time of scanning is10～12s.The data of seanning images are conserved in PC by DICOM. Scan from the femoral head on the set 1cm, down to 0.75mm scan spacing between the isthmus below 20 mm, thickness of 0.75mm.2. Experimental methods2.1 Three-dimensional reconstruction CT image data was saved in DICM format after scanned and stored, the image repository via the USB port for incoming mobile hard disk, and then spread to a small mobile hard disk data on your computer to be post-processing within the working platform. The CT image data was input into Mimics software, and thus reconstruct the formation of three-dimensional solid model-of the proximal femur.2.2 Measurement of the object Measure the vertices of small protuberance at the top of 20mm (T+20),10 mm (T+10), small protuberance vertices (T) and below 20 mm (T-20), isthmus of the medullary cavity diameter (Figure below). Unit within the parameters of measurement of bone marrow were measured at the required level of use of computers 0mm thickness of cut, measured stump diameter of medullary cavity.2.3 To reconstruct PFNA with UG software and match it with the proximal femur. According to data provided by SYNTHES of PFNA, using UG software, reconstruct it in three-dimensional view. The reconstructed PFNA proximal diameters of 17.5mm,17mm,16.5mm,16mm, and the main nail angle were 5°,6°,in total of 8 kinds of specifications PFNA Model. And then import the PFNA model into the proximal femur from simulate surgical procedures, make sure that the PFNA centerline axis overlaps with the femur and Its full access to the greater trochanter of the proximal. And to observe this process, whether there is any plane PFNA overlap with the lateral proximal femur Cortical, overlaps are recorded as(+).3. Statistical analysisUsing statistical software SPSS13.0 for date analyzing, data records was depicted by the mean±standard deviation (X±s) The height, age, sex and various indicators of examination were analyzed by correlation. Chi-square test was used to compare ratio data, the independent sample t test was used to compare with two sets of data. Tangent rate and height, gender-related sex-related regression analysis was used to compare.Result1.Measurement data1.1 There exit significant difference in the medullary cavity diameter 20 mm above the lesser trochanter midpoint (T+20) plane between men and women group, the average diameter were (44.79±5.42) mm and (39.79±4.96) mm(t=5.270,P< 0.001); And 10mm above the lesser trochanter midpoint plane(T+10) of medullary cavity diameter were (34.00±3.64)mm and (32.06±3.29)mm, also exit significant difference(t=2.963, P<0.01); In the lesser trochanter midpoint plane, they were (26.93±3.71)mm and (24.18±3.31)mm, and there exit significant difference(t= 4.292, P<0.001). In the plane 20mm under the lesser trochanter midpoint(T-20), the average medullary cavity diameter were (18.65±2.96)mm and (18.21±2.60)mm and there are no significant difference between two groups(t=0.864, P>0.05). In the isthmus plane, the average medullary cavity diameter were (10.19±1.44)mm and (10.15±1.05) mm and there are no significant difference between two groups(t =0.864,P>0.05).1.2 The correlation between canal diameter, the expansion score and age, height.Analyzing the correlation between canal diameter, the expansion score and the data, the results suggest that there exit significant difference when using simple correlation analysis of available data in each experimental group, and it were positively correlated with height (p＜0.01) but not correlated with age (p>0.05). using partial correlation analysis shows that height were positively correlated with the data strongly, except for MCFI (p<0.05). The age were also positively correlated with the data, but for CFI, MCFI and DCFI (p<0.05)2. False positive rate after the prosthesis import2.1 Proximal diameter of 17.5mm,17mm,16.5mm,16mm, main nail angle were 6°of PFNA prosthesis model, the positive cases were 35 cases,21 cases,12 cases,3 cases, the positive rates were 29.2%,17.5%,10%,2.5%. there are significant difference between groups (χ2=36.94,p<0.001).Proximal diameter of 17.5mm,17mm,16.5mm,16mm, main nail angle were 5°of PFNA prosthesis model, the positive cases were 27 cases,15 cases,7 cases,2 cases, the positive rates were 22.5%,12.5%,5.8%,1.7%. there are significant difference between groups (χ2=31.31,p<0.001).2.2 Men and women group import the standard PFNA the positive rate were lower in men than females, there were significant differences (χ2=4.97,p<0.05) Simply reduce the angle without changing the nail prosthesis diameter proximal the positive rate decreased, but there is no statistical significance, that is, it not means that just to change the angle nail can reduce the positive rate. At the same time to change the main nail angle and the proximal diameter, the positive rate decreased significantly, there were statistically significant.Conclusion1. This study proposes a new measurement way of the proximal femoral medullary cavity anatomy. It is feasible to make the three-dimensional reconstruction of the normal proximal femora on the basis of the CT sectional images:We could obtain satisfactory morphous and boundary in the three-dimensional model of the normal proximal femora. Compared with traditional methods, the model of the normal proximal femora image has good Stereoacuity.We can observe it from any angle and direction, remove dodge Part and show the Part we want to see by vitrifieation management.2. Inner diameter of the proximal femur of both sexes there was a significant difference for men bigger than women in medullary cavity diameter and the isthmus was no significant difference between the two. There was a significant difference between in the inside diameter of the proximal femoral medullary cavity of people in China with Europe and the United States. Full study of femoral marrow morphologic features people need to line measurement of large sample test.3. Femoral medullary cavity diameter and height, age was positively correlated. People with different height and femur length in, its femur marrow cavity diameter of the isthmus is relatively fixed, but as age increased, the incidence of osteoporosis and its femur marrow cavity was in the increasing trend.4. The proximal diameter of PFNA produced by SYNTHES is Relatively coarse, which does not match wll with Chinese proximal femur, when it applied to patients with intertrochanteric fractures,it is easily result in a higher risk of fracturing of proximal femoral during surgery.5. Treatment of the relatively short stature of female patients with intertrochanteric fractures, in order to prevent the intraoperative occurrence of greater trochanter splitting, preoperative need to be fully measured to assess their marrow diameter, and design appropriate surgical programs.6. The PFNA prosthesis, which main nail lateral angle of 5°, its top is often prominent in the pyriform fossa during importing process, and that may result in postoperative long-term hip pain.As a result, the lateral angle should be chosen between the 6°～5°when making a designation.
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