Design Of Custom-made Navigational Template Of Hip Joint And Pilot Research In Hip Arthroplasty

Objective:This study developing a novel custom-made navigational template by computer-aided technology and rapid prototyping(RP) technology, the objective of this article is to provide a new method and effective auxiliary means for the femoral head and acetabular prosthesis accurate orientation in total hip resurfacing arthroplasty (THRA) and total hip arthroplasty (THA).Methods:①We collected9cadaveric specimens raw CT data by DICOM format, these date were loaded-into Mimics10.01software, then, we reconstructed the proximal femur3D anatomical model after pretreated these date.②The position of the femoral head template’s drill guide was chosen as the anatomical axis of the femoral neck which was defined by the ligature between the center of the femoral head and another point on the centerline of proximal femoral neck. And the final direction of the drill guide was confirmed by a small valgus angle. The surface of the template was constructed as the inverse of the femoral neck surface. Then each template was formed from acrylate resin by using rapid prototyping (RP) technique.③The harris fossa navigation template’s surface was designed to conform to the unique contours of the cadaveric Harris fossa on the basis of reverse engineering (RE) principle. The direction of the drill guide was chosen as the acetabular central axis which was defined by the contralateral acetabular center of rotation, anteversion and abduction angles. Then each template was formed from acrylate resin by using rapid prototyping (RP) technique.④All surgeries were performed in a laboratory, after exposing as necessary and cleaning the soft tissue, the navigational template was matched to the femoral head and the harris fossa surface accurately, a locating wire was implanted into the femoral head and the bottom of the Harris fossa as the expected channel of prosthetic implantation. We removed the template, followed the guide pin with the hollow acetabular reamer to polish the acetabular and shaped the prosthetic socket at the expected angle we had calculated. The acetabular prosthesis could be installed along the track that had been ground.⑤The positions of the locating wire and the acetabular prosthesis after the surgeries were evaluated by x-ray and CT scan. The measurement indices are as follows:(1) the anteversion angle;(2) the abduction angle of the acetabulum;(3) the height of the acetabular center;(4) The horizontal location of the acetabular center. All data were measured and presented in the form of mean±standard deviation (SD). T-test was performed by using Prism6.0software.Results:①The novel femoral template had a near-perfect fit with the femoral neck and no significant free motion was found, they performed a optimal stability and guidance, and guide the femoral locating wire implanted to the desired position.②Postoperative statistic analysis of medical imaging revealed that the femoral locating wires were through the center of the femoral head, have no obvious horizontal and lateral offset, express slight valgus position to the femoral neck anatomical axis, achieve the desired implant requirements.③Harris fossa navigation template performed optimum geometric similarity to the Harris fossa surface, had a near-perfect fit each other, performed a optimal stability and guidance, and guide the acetabular prosthesis implanted to the desired position.④Postoperative of medical imaging revealed that the locating wire is perpendicular to the acetabular cup opening. And the average deviation of anteversion and abduction angles between acetabular cup and contralateral acetabulum shows the goal of closely mimicking the normal anatomy of the hip joint was achieved perfectly. Conclusions:①The proximal femoral anatomic axis and HJC can be precisely calculated based on computer aided and reverse engineering, and the acetabular axis can be accurately calculated by means of triangular function.②The novel custom-made navigation template has the best geometric similarity with different individuals of the anatomical characteristics of the Harris fossa and femoral head, The best template can assist the acetabular cup and femoral prosthesis implanted to the desired position.③The novel custom-made navigation template must be an excellent medium for preoperative planning and intraoperative technique, The method provides a new and effective supplementary means for the positioning and orientation of femoral and acetabular prosthesis, and embodies the development tendency of individualized treatment and digital orthopedics.