Biomechanical analysis by finite element method and evaluation of geometrical properties from two and three dimensional images of femur in the dog

The understanding of the proximal femoral geometry is very important to develop of new prosthesis design and evaluate of bone-implant alignment on the total hip arthroplasty studies. The morphometric studies on dog femora are limited regarding implant design in veterinary medicine, although the femur is an important bone in dog orthopedics with functional and morphological properties. To investigate of differences on the measurements of canine proximal femora between the x-ray and three dimensional model images has aimed in this study. Second aim of this study has also investigated the differences on breed characteristics of geometrical and biomechanical properties of proximal femora between the German shepherd and Kangal dogs which have common hip problems and body conformation differences.The cleaned femora of 21 dogs (11 Anatolian shepherd dogs,10 German shepherd dogs) were used in this study. The X-ray images were obtained on cranio-caudal and medio-lateral positions. The sectional images were also obtained with computed tomography. The three-dimensional solid models were also created by using these images with computer. The some measurements were obtained from proximal femora both with computer-generated three-dimensional models and two-dimensional images. The biomechanical simulation with finite element method on three-dimensional models of femora was also generated.There were some differences on the measurements of position of femoral head and medullary canal of proximal femora between the x-ray and 3D methods. But, there were no differences between two methods at inclination angle and canal flare index which have more important data for designing of implant. The proximal femoral geometry may be evaluated more valid by three-dimensional measuring method, although the both methods may effective to this evaluation when used together. Beside, any difference was not observed on the shape of medullary canal and placement of isthmus region of the proximal femora between the Kangal and German shepherd dog. The mean values of canal flare index were observed 2.44-2.64 as medio-laterally, 1.52-1.59 as cranio-caudaly. The mean values of position of proximal and distal isthmus indices were also observed as 39.59-40.43 and 42.84-46.54, relatively. Related with femoral head position, there was an important diffirence between the inclination angle of Kangal and German Shepherd dogs. The mean angle was observed as 145o and 149o on German shepherd and Kangal dogs, relatively. In proportionally, the femoral head of Anatolian shepherd dog has located on more proximal than femoral head of German shepherd dog, but the distance between the center of femoral head and the anatomical axis of bone was similar in both breeds. There were no differences between the results of biomechanical simulations of dog breeds. However, the postoperative fracture risk may increase because of unexpected loads on different parts if the same type of prosthesis is used in different neck geometry.