Tips and Pearls
Orthopedic surgeons are cautious about performing distal interlocks of an intramedullary nail. Various authors have used different targeting devices to perform distal locking.1,2 We describe an easy and reproducible technique to perform distal locking, one that lends itself to confirmation during the process. The concept relies on the availability of 2 nails of the same length. In India, local-made intramedullary nails are not separately packaged, hence same length nails are available in a set.
The chosen nail is mounted onto the aiming device. Another same length nail is placed parallel and at the same level as in Figure 1. Distal holes will always overlap.
After nail insertion, using the sleeves and second nail, locking site is determined on the limb. Take care to keep the outside nail parallel to the nail inside the bone. The level of the distal holes corresponds to the holes of the outside nail.
Through a stab, drill a unicortical hole roughly at the center of the bone felt by moving the drill bit. Use a K-wire to feel the nail and the distal hole. The wire once in the hole will slide over the anterior and posterior surface of the nail. Once in the locking hole, K-wire moves when hit by the guide wire confirming the position. Using the direction of the K-wire drill the far cortex. Push the guide wire maximally into the nail and mark the junction with the nail using a Kocher forceps. Insert the locking screw till no more would go in. The screw will jam the guide wire confirming the position. Now slightly unscrew the bolt, withdraw the wire, and complete the locking. Double check the process by reinserting the guide wire, which will stay proud as the locking bolt will not allow it to go in all the way. This is helped by the Kocher forceps used in the previous step. Similar steps can be carried out for the second screw.
Techniques to perform locking without using radiation have been described in the past. The difference in our technique is that there is no need for extra jigs and also provides the means of confirming the locking bolt position. There is a learning curve for this technique, however, we have used it over many years and have experience of over 1000 procedures, with successful results.
The author would like to thank Dr Harsimran Singh who provided the pictures to go along with this article.
1. Krettek C, Konemann B, Miclau T, et al. A new mechanical aiming device for the placement of distal interlocking screws in femoral nails. Arch Orthop Trauma Surg. 1998;117:147–152
2. Pardiwala D, Prabhu V, Dudhniwala G, et al. The AO distal locking aiming device: an evaluation of efficacy and learning curve. Injury. 2001;32:713–718