A mechanical distal aiming device for distal locking in femoral nails.

Although the free hand technique remains the most popular method for distal interlocking screw insertion, proximally mounted radiation independent devices that compensate for implant deformation recently have been developed for the femur. However, the benefits of such systems have not been determined. This study prospectively compared the duration of the nailing procedure, the length of radiation time, and the accuracy of interlocking screw placement when using a radiation independent distal aiming system with those using the free hand technique. In 20 paired intact anatomic specimen femurs, one surgeon experienced only in the free hand technique performed statically locked intramedullary nailing using the two methods. For the aiming system and free hand technique, respectively, the total operation time was 19.1 +/- 8.4 minutes versus 20.9 +/- 11.3 minutes, the distal locking time was 6.6 +/- 2.4 minutes versus 4.8 +/- 1.5 minutes, the total fluoroscopy time was 23 +/- 17 seconds versus 69 +/- 34 seconds, and the distal locking fluoroscopy time was 0 versus 37 +/- 15.5 seconds. There were no failures in either group. Drill nail contact and distal screw damage were greater with the free hand technique. This study suggests that the main advantages of the aiming arm compared with the free hand technique include the elimination of radiation during distal interlocking and more precise screw placement with decreased insertion related hardware damage.