Introduction When locking intramedullary nails, inserting the distal interlocking screw accurately and quickly with less radiation exposure is very important. The purpose of this randomized control study was to compare radiation exposure and accuracy of distal locking screws between free-hand fiuoroscopic guidance and the use of a distal targeting system (DTS). Materials and methods Inclusion criteria of this study were patients older than 60 years who need an intramedullary nailing due to unstable intertrochanteric and subtrochanteric fracture. The primary outcome was the attempt numbers of image intensifier during the insertion of distal locking screws. Secondary outcomes were operative time and angles between distal locking screws and nail.Results A total of 36 patients participated in the study. Eighteen patients using free-hand fiuoroscopic guidance were assigned to Group I while 18 patients using DTS were assigned to Group II. The number of attempts of image intensifier during distal screw insertion (57.3 ?1.42 vs. 11.5 ?7.41, p< 0.001), ratio of attempt number for distal screws to the total attempts (0.33 ?.21 vs. 0.12 ?.08,/? = 0.001), the number of hand exposure to image intensifier directly (75.0 ?9.55 vs. 13.5 ?19.07, p< 0.001), and the time of radiation exposure during distal screws insertion (42.57 ?.42 s vs. 12.72 ?.10 s, p< 0.001) were significantly lower in Group II compared to those in Group I. And, operation time (96.3 min?18.94 vs. 76.1 min ?14.10, p< 0.001) was also statistically significantly lower in Group II. Both distal locking screws were significantly closer to perpendicular direction to the nail in Group II.Conclusion The attempt number of image intensifier during the insertion of two distal locking screws was significantly reduced with DTS compared with that with free hand fiuoroscopic guidance. Angle between distal locking screws and nail was also more accurate using DTS.
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