OTA 1997 Posters - Femur Fractures

*The Efficacy of a Radiation Independent Distal Interlocking Aiming Device for the Femur and Tibia. A Comparison to the Free Hand Technique

Christian Krettek, MD, Bernd Könemann, MD, Theodore Miclau, MD, Osana Farouk, MD, Reto Kölbli, MD

Hannover Medical School, Hannover, Germany

Introduction: Current methods of distal interlocking of intramedullary nails have the disadvantage of being dependent upon image intensification. Efforts to develop a radiation-independent system have failed because insertional bending and rotational forces deform the nail. The free hand technique therefore remains the most popular method for distal screw insertion. Recently, radiation-independent proximally mounted aiming devices which compensate for implant deformation have been developed for the femur and tibia. However, the accuracy and reduction of actual fluoroscopy time with such systems has not been determined. The purpose of this study was to prospectively compare the accuracy of screw placement, length of radiation time, and the duration of the nailing procedure with a radiation-independent distal aiming system for the femur and tibia to those using the free hand technique.

Materials and Methods: Twenty paired femurs and twenty paired tibiae from fresh human cadavers were used for this study. On one side, a solid nail used in conjunction with the device, was placed and interlocked with distal screws using a distal aiming system (DAD) and, on the other side, the nail was interlocked using the free hand technique (FHT) with fluoroscopy and a radiolucent drill. The surgeons, prior to instruction, had not previously used the distal aiming device. The surgeon for the femurs was experienced with the FHT and the surgeon for the tibias was previously unfamiliar with the FHT. The procedures were videotaped and the total operating time, the distal screw insertion time, total fluoroscopy time, and distal fluoroscopy time was determined. Drill nail contact was noted. The accuracy of screw placement and the insertion related damage to the screw as measured with a caliper were recorded. Major and minor intraoperative complications were also noted. Statistical analyses were performed with the Wilcox on matched-pairs signed ranks test.

Results: The following times were recorded for the femur and tibia respectively: the total operation time was 19.1 ± 8.4 and 25.4 ± 11. 3 min for the DAD and 20.9 ± 11. 3 and 30.9 ± 14.3 min for the FHT (p=0.9 and 0.03 respectively); the distal locking time was 6.6 ± 2.4 and 16.7 ± 8.6 min for the DAD and 4.8 ± 1.5 and 21.9 ± 5 min for the FHT (p=0.002 and 0.004 respectively); the total fluoroscopy time was 23 ± 17 and 9 ± 5 s for the DAD and 69 ± 34 and 93 ± 34 s for the FHT (p<0.0001 and 0.0001 respectively); and the fluoroscopy time for distal locking was 0 s for both the femur and tibia for the DAD and 37 ± 15.5 and 88 ± 33 s for the FHT (p<0.0001 and 0.0001 respectively). Drill nail contact was more prevalent for the FHT than the DAD in both the femur and tibia groups with significantly increased caliper measured screw damage in the FHT versus the DAD of both groups (p<0.05 and 0.001 respectively). There were no failures in either of the femur groups and one failure each in the tibia groups (1 of 60, or 1.6%). Major complications did not occur with either technique in the femur or tibia. Minor complications occurred in 2 of 20 surgeries in both femoral DAD and FHT groups and in 3 of the 20 surgeries in both tibiae DAD and FHT groups.

Conclusion: Based on the results of this study, distal interlocking screws can be placed with equal success using either a 'radiation-independent' DAD or the FHT. The aiming device, however, decreases insertion related screw damage which could lead to hardware failure. The distal locking time appears to be faster with the FHT in an experienced surgeon's hands and with the DAD for an inexperienced surgeon. Total fluoroscopy and distal locking fluoroscopy times are drastically reduced with the use of a DAD than with the FHT. The authors conclude that distal aiming devices can reduce locking screw damage and eliminate the need for radiation during interlocking screw placement.