| Objective: Proximal femoral nail anti-rotation(PFNA) has been widely used for treatment of intertrochanteric fractures. But its compatibility with the anatomical shape of femoral marrow cavity has also been controversial. With image processing software, this study analyzed CT images of adult femoral shaft and measured diameter of femoral marrow cavity on the traverse section of different directions, and analyzed measured data of multiply samples. Changes of diameter of proximal femoral medullary cavity were observed for the presence of statistical significance, and the change rule of minimum diameter position was found out. According to the measured data, the compatibility between PFNA and medullary cavity was analyzed to further improve the design and clinical application of PFNA.Methods: 60 cases of patients were given CT scan on the whole femur, where 50 cases conformed to the inclusion criteria. There were 25 male and 25 female patients, aging from 50 to 90 years. MIMICS10.01 was used to process femoral CT data. Anatomical parameters of proximal femur were measured, including the distance from great trochanter vertex to small trochanter and the distance from great trochanter vertex to femoral condyle. Several sections were taken from the level of small trochanter to femoral isthmus with an interval of 1 cm. On each section, diameters of 8 directions were measured. According to the measured data, the distribution law was analyzed. And statistical software was used for measured value in male and female group to test their differences. The ratios were calculated to summarize whether there was clinical significance. By comparing between anatomic parameters and PFNA parameters, their compatibility was measured.Results: 1. The distance from great trochanter vertex to small trochanter: range of value a in male group was 4.80-6.40 cm while 4.70-5.50 cm in female group. Average value was 5.456 cm in male group and 4.976 cm in female group, and there were statistical differences between two groups. 2. The minimum diameter of the medullary cavity: there were no obvious differences between men and women in distribution of minimum diameter of the medullary cavity and the average value of 50 samples was 10.718 mm. 3. Then distance between the minimum diameter of the medullary cavity and great trochanter vertex: average value was 17.424 cm in men and 16.886 cm in women. The value was lager in men than women. 4. Range of value K was 38.88%-46.92%. There were no obviously statistical differences between two groups. 5. The minimum diameter of the medullary cavity: The minimum diameter of medullary cavity was 8.19-14.18 mm in male group and 8.99-12.61 mm in female group. There were no statistical differences between two groups in minimum diameter of the medullary cavity and the overall average was 10.72 mm.Conclusion: 1. There is a certain proportion relation between the plane of the minimum diameter of elderly femoral marrow cavity and length of femoral shaft. The distribution of this proportion value is relatively concentrated. The position of the minimum diameter is lower in male group than in the female group. 2. The vast majority(82%) of the minimum diameter of medullary cavity appeared in direction of D0, namely the direction of femoral coronary diameter. It is confirmed that inner diameter of the medullary cavity in X film of lower limb at neutral position reflects the minimum value of medullary cavity. Therefore, it is meaningful to select X film of lower limb at neutral position to assess the diameter of the medullary cavity and to select specifications of the main nail. 3. There are a certain number of patients(distribution rate is 10%) with minimum diameter of the medullary cavity less than 9mm in clinical. Considering PFNA must pass the plane of the minimum diameter, it is requirement to use main nail with smaller diameter. |
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