| OBJECTIVE:The three-dimensional method was used to study the relationship between the entry point and the femoral bowing of Chinese subjects.On the basis of this,a three-dimensional simulation experiment was carried out to explore the potential error angle in the opening process of femoral marrow in all aspects,and a method to reduce the error was proposed.METHODS:1.The full-length CT images of both lower limbs of 80 Chinese patients were collected and imported into Mimics 19.0 to construct three-dimensional models.The cFBA and sFBA were measured in Rhinoceros 5.0.Taking the apex of the intercondylar notch as the reference point,the anterior-posterior and medial-lateral distances of the entry point relative to the apex of the intercondylar notch were measured.Finally,the relationship between the position of the entry point and the femoral bowing was analyzed.2.The full-length CT images of both lower limbs of 100 Chinese patients were collected to establish a three-dimensional model of the femur.A three-dimensional simulation experiment was carried out in the software.The potential error angle was measured by setting up different diameters of intramedullary rod inserted into the femoral medullary cavity through different entry point.At the same time,the insertion length of the intramedullary rod and its distance to the femoral isthmus were also measured.RESULTS:1.The proper entry point for males was located at 0.17±1.86mm medially and 12.37±2.39 mm anteriorly to the apex of the intercondylar notch,whereas for females the optimal entry point was located at 0.02±2.00mm medially and 16.13±2.72mm anteriorly to the apex of the intercondylar notch.The anteroposterior distance of the proper entry point was statistically different between males and females(t=-6.570,p=0.000).The cFBA was 1.68±2.29° and the sFBA was 12.66±1.98°.The sFBA was strongly correlated with the anterior-posterior distance of the proper entry point(r=0.718,P=0.000),and cFBA was moderately correlated with the medial-lateral distance of the proper entry point(r=0.406,P=0.000).2.Regardless of the diameter of the intramedullary rod,the error angle caused by the position of the entry point was significantly greater than the error angle caused by the intramedullary rod,which was statistically different with a p-value less than 0.05.In the present study,the intramedullary rod with a diameter of 10 mm and a length of 192.82±28.48 mm caused the smallest error angle by complete insertion of the intramedullary rod into the femoral bone marrow cavity through the ideal entry point.CONCLUSION:1.The location of the entry point was different for Chinese male and female.The optimal entry point for Chinese male was located at 0.17±1.86 mm medially and 12.37±2.39 mm anteriorly to the apex of the intercondylar notch whereas the optimal entry point was located at 0.02±2.00mm medially and 16.13±2.72mm anteriorly to the apex of the intercondylar notch for Chinese females.The surgeon could also accurately calculate the location of the entry point based on the cFBA and sFBA of the femur in each patient.With the apex of the intercondylar notch as the reference point,the lateral distance of the entry point=-0.341×cFBA+0.652 and the anterior-posterior distance of the entry point=1.148 × sFBA-0.281.2.The error caused by the position of entry point was significantly greater than that caused by the intramedullary rod.Based on the results of this study,we recommend using an intramedullary rod with a diameter of 10 mm and a length of 192.82±28.48 mm to completely insert it into the femoral medullary cavity through the intersection of the distal femoral anatomic axis and the femoral articular surface in order to effectively reduce the potential error of intramedullary positioning. |
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