Experimental Study Of Computer-assisted Thermoplastic Elastomer Film Localization System: Application For Insertion Of Posterior Column Of Acetabulum Screws In Nondisplaced Fractures

Objective: To assess accuracy and effects of the mini-invasive insertion of posterior column of acetabulum screws by computer assisted thermoplastic elastomer film localization system.Methods: 20 half- pelvises of 10 corpses were divided into 10 pairs,each pair from one same corpse,then distribute every two of each pair into the experimental group and the control group, So we get 10 half- pelvises of experimental group and 10 half- pelvises of control group. In a simulated surgical setup, 10 half- pelvises from the experimental group were placed 10 cannulated screws into the posterior column of acetabulum under the guidance of computer assisted thermoplastic elastomer film localization system. In the same time, 10 half- pelvises from the control group were placed 10 cannulated screws into the posterior column of acetabulum under the help of the C-arm X-ray fluoroscopic unit. When the guide pin begin to be drilled,the time recording were started, and it continued until the whole scrow was drilled into the sclerotin,The times of the projection, the length of guide pin which in the sclerotin and the length were also recorded to find the different of the two Methods. Then validate the position of the screws though CR and CT.Results: With the guidance of thermoplastic elastomer film localization system, radiation exposure was totally avoided, 378.2±126.7 seconds were used when one screw was drilled,the length marked on the guide pin under the help of the computer was 104.1±18.7 mm and length of the screw we drilled into the posterior column of acetabulum was 102.0±18.4 mm. Check the position of the screws though CT, None of the 10 cannulated screws were drilled out of the cortical bone, or into the acetabulum or into iliac fossa ,the sciatic nerve were also safe. The position of all screw were suitable through anteroposterior view, 45-degree angle obturator oblique view, 45-degree angle iliac oblique view of CR. All the 10 screws were in the safe area though CT. On the other hand, under the help of the C-arm X-ray fluoroscopic unit, the number of times of projection were 37.1±15.9 times, 1525.4±597.7 seconds were used when one screw was drilled, the length of the guide pin were fathomed as 99.1±18.8 mm and length of the screw we drilled into the posterior column of acetabulum was 97.0±18.6 mm. Check the position of the screws though CT, None of the 10 cannulated screws were drilled out of the cortical bone, or into the acetabulum or into iliac fossa ,the sciatic nerve were also safe. The position of all screw were suitable through anteroposterior view, 45-degree angle obturator oblique view, 45-degree angle iliac oblique view of CR. But 2 screws were tangent with the acetabular rim though CT. Finally we conclude, less times were used with thermoplastic elastomer film localization system than C-arm-assisted, and it also could provide a longer screw through statistical analysis system.Conclusion: Compare with C-arm assisted screw drilling, thermoplastic elastomer film localization system can save operating time, and also can use the sclerotin of the acetabular more effectually. When use this system, we can avoid the radiation exposure to the patient and the staff significantly. What's more, it is totally safe from the radiotelegram.