Application Of Navigational Template For Proximal Femoral Corrective Osteotomy In The Treatment Of Developmental Dislocation Of Hip

Background：Developmental dislocation of the hip (DDH) is a spectrum of disorders ofdevelopment of the hip that present in different forms at different ages. The common etiologyis excessive laxity of the hip capsule with a failure to maintain the femoral head within theacetabulum. The main pathological change of developmental dysplasia of the hip thefollowing change after dislocation, acetabular bone lack excitation of femoral head,acetabular bone gradually grow down, femoral head develop slow, neck of femur becomewiden short, anteversion angle become large, articular capsule become thick, ambient musclecontracture, adductor tension, so add positioning difficult, in the end appearance crispationmalformation. The therapeutic principle of developmental dysplasia of the hip is earlydiagnosis, early treatment. The more early treatment, the better the effect, and can cut downcomplication probability in long-term. The operation plan was usually designed according toX-ray and age of the children. However, the surgeons can not evaluate the diseasecomprehensive because of the limitations of X-ray. Rapid prototype production, which hasbeen developed for more than a decade and has been widely used in the medical field foryears. Its outstanding feature is the layered stack, which excels at creating complex entitieswith high accuracy. It has been previously reported that anatomical models can be producedusing rapid prototype technology. Nowadays, reverse engineering and rapid prototypingtechnique have showed its advantages in designing the operation plan.Objective：This study aimed to detective the application of reverse engineering and rapidprototyping technique in designing template for derotational femoral shortening osteotomy inDDH. Methods：CT scans of eleven patients of DDH were performed. The image data weretransferred into Mimics software, and after reconstruction of the three-dimensional models offemur and saving in.stl format, the three-dimensional models were imported into Imageware12.0software to determine the three-dimensional plane of reference. The best kirschner wirechannel of derotational femoral shortening osteotomy was extracted according to the reverseengineering principle. The template was designed according to the anatomic features of thefemoral surface, and the optimal osteotomy channel and the template were overlapped as thenavigational template, which was manufactured by rapid prototyping. The template wasplaced distally on the external femur, and the location for kirschner wires insertion wasdefined by the navigation template. The accuracy of screws placement were confirmed withpostoperative X ray and CT scanning.Results：The digital navigational template had been established and used in the elevencases, After twelve to eighteen months of follow up, there were no major complicationsrelated to the osteotomy such as redislocation or avascular necrosis. The actual femoralanteversion angles corresponded almost exactly to the planned corrective angles in all cases.Conclusion：A novel method of derotational femoral shortening osteotomy using reverseengineering and rapid prototyping has been developed, the navigational template is found tobe highly accuracy and has great expectation.