Research And Application Of The Reduction Frame For The Unstable Pelvic Fracture

BackgroundThe unstable pelvic fracture was defined as the pelvic fracture with partially or totally displacement of the hemipelvis, the managements methods of which included early open reduction and internal fixation and external fixation. Traditional treatment of unstable pelvic fractures require extensive surgical exposure of the deep structures, which are associated with many post-operative complications, such as the wound healing problems, the vessels or nerves injuries and the wound infection. Although the risk of causing vessels or nerves injuries was relatively low during traditional closed reduction method, the anatomical reduction was difficult to reach accordingly. Computer assisted orthopaedic surgery (CAOS) might provide a new clue for us. CAOS put together the computer aided imaging process, robot and orthopaedics surgery to locate and present the anatomy of human body precisely and decrease the associated injuries to the lowest level. The purpose of this study was to design a reduction frame for the unstable pelvic fracture in order to reduce the displaced semipelvis precisely according to the pre-defined procedure and route.Objective(1) Based on the characteristics of the unstable pelvic fractures, the optimal reduction route leading to the anatomical reduction of the pelvis could be established.(2) Based on the reduction route for the unstable pelvic fractures, a reduction frame for the unstable pelvic fracture was designed and produced accordingly, the accuracy of which was verified in the model and clinical studies.Methods(1) Using CAD softwares to reconstruct the pelvic models, and analyze and design the reduction route for the unstable pelvic fractures. A measurement method to calculating the rotational and translational displacements could be established. Based on this method, the optimal reduction route could be set up using the Mimics and 3-Matic softwares.(2) Based on the optimal reduction route for the unstable pelvic fracture and the Starr frame, the reduction frame could be designed and produced, which could incorporate the displacements parameters.(3) Verify the efficacy of the reduction frame. Based on the actual situations of unstable pelvic fractures patients, the reduction frame was used to perform the anatomical reduction according to the previous established clinical route.Results(1) The rotational and translational displacements of the semipelvis could be calculated using the established measurement method and be divided into two orthogonal axes and an arbitrary axis.(2) Based on the basic concept of the RCM (Remote center of motion) mechanism, the reduction frame could be designed according to the circular-prismatic-joint RCM mechanism; the reduction route of the unstable pelvic fractures could be established.(3) The experiments of the pelvic modeds and the clinical applications were performed to verify the efficacy of the frame. The translational and rotational accuracy of the frame was less than 5 mm and 4 degrees, respectively.ConclusionThe established frame could be used as a useful tool for reducing the unstable pelvic fracture according to the calculations results of the rotational and translational displacements using the CAD softwares, and the anatomical reduction of the unstable pelvic fracture could be achieved accoringly.