Experimental Study Of Lag Screw Internal Fixation In The Anterior Column Of The Acetabulum With Computer-assisted Thermoplastic Elastomer Film Localization System

Objective:To assess effects and security of the insertion of the lag screw internal fixation in the anterior column of the acetabulum by Computer-assisted Thermoplastic Elastomer Film Localization System. Providing a new surgical methods for treatment of the anterior column of the acetabulum frature with slight dislocation.Methods:Pelvic specimens of body were marked numbers randomly(No.1~No.10).Each specimen of the left acetabular anterior column for the experimental group, the right side compared with the control group. Experimental group: Put the Pelvic specimens at the fixed base, taken in supine position. Thermoplastic elastomer film(TEF) was placed in hot water tank heated to 65℃. Thermoplastic elastomer film, to be softened, was covered to the pelvic specimens surface. Use the around locked button to make it firmly fixed on the base. After temperature droped and TEF shaped successful, Specimens were disposed of at the CT examination table. Three initial starting point of laser positioning system were defined as the reference plane, and marked by lead tablets. (Fig.2,3). After CT scanning (slice thickness was 3mm), the image data were transmitted to the image processing workstations. In image processing workstation, three-point lead marker were established as reference plane.Set up three-dimensional image and profiles of acetabular anterior column. At three-dimensional image, we designed the retrograde acetabular anterior column lag screw path, determine the optimum point of screw into , best direction of screw implantation in order to determine screw in acetabular anterior column running path. Forward and backward extension of the channel, marked on the TEF surface, positioning surgical screw and a nail virtual coordinates. System were calculated the parameters of the entrance point and virtual exit point of screws in thermoplastic elastomer film,including the length of the screws. Confirm the nail route, simulate the surgical procedures. Put the coordinates of screw point into and virtual nails point out into computer program, the point were projected onto the surface of TEF by Three-dimensional laser positioning point system,and marked it. Fixed with the lag screws by using the Director. The director was adjusted to both the entrance point and virtual exit point of screws. Drillφ2.5mm needle guide,srewed 7.3mm lag hollow screw. Remove the guide pin.After the implantation of screws, checking the location of the screws by X-ray and CT. Control group: put the right side of thses 10 specimens as control group. In order to compare this new technique with the conventional technique, using C-arm fluoroscopy guided for acetabular anterior column lag screw placement. Left lying on the operating table, fixed anterior column of acetabular by lag screw using C-arm fluoroscopy guided.After the implantation of screws, checking the location of the screws by CR and CT. The fluoroscopic times, the radiation exposure time and operation time between beginning of operation and guide-wire insertion were recorded,then Statistical Analysis.Results:The X-ray and CT images confirmed that:all of 10 experimental group's lag screw were accurately implanted in the acetabular anterior column;the control group has a guide-wire into the hip joint. In the experimental group, radiation exposure was totally avoided, and the average operation time was 143.5 seconds, and the average length of the nails was 10.76cm±0.24cm, all the acetabular anterior column lag screw were in the safe area. In the control group ,under the fluoroscopic control, the average fluoroscopic times were 41.7seconds, the average operation time was 792.2 seconds,and the average length of the nails was 10.47cm±0.14cm, one screws (10%) were misplaced. The fluoroscopic times, operation time were reduced significantly when this system was used(P<0.05). Two types of screw fixation at length on non-discriminatory selection(P=0.1039>0.05).Conclusion:Computer-assisted Thermoplastic Elastomer Film Localization System for acetabular anterior column lag screw placement provide precise spatial orientation and path navigation. This new technique can decreasing the fluoroscopic times, operation time significantly and has excellent safety and efficiency. To provid a new method of surgical positioning for clinical treatment of acetabular anterior column without displacement or mildly displaced fracture.