Diaphyseal femur fractures (DFF) are a relatively common injury with an incidence of nearly 18.4 per 100,000 people.1 The treatment for DFF is overwhelmingly performed with intramedullary nails (IMNs). IMNs require locking both proximally and distally with screws. For retrograde femoral nails, the distal locking screws are routinely placed using the aiming arm of the insertion jig, and vice versa for antegrade nails. However, the locking holes opposite the insertion end require placement via a free-hand technique. This free-hand technique is typically performed using a “perfect circles” method. It requires careful coordination between the surgeon and the fluoroscopy technician. Treating DFFs with IMNs has been shown to use significantly more radiation than other methods, and furthermore, the majority of the exposure comes during the placement of the free-handed locking screws.2 To decrease operative time and radiation exposure, multiple manufacturers have created guides, extended aiming arms, and other tools to help place these locking screws more efficiently and with less radiation exposure.3,4 However, these guides tend to be cumbersome, expensive, and inaccurate which limits their widespread use.

The perfect circle technique remains the most used free-hand locking crew insertion method. In this paper, we describe a simple trick to perform this technique more efficiently. It requires no more equipment than the standard image intensifier augmented with a centered laser pointer. With this trick, we anticipate decreased errors in screw placement and reduced operative and fluoroscopic time.

TECHNIQUE

Once the femur is reduced appropriately, the retrograde or antegrade IMN is inserted into the femur in standard manner. The insertion end of the nail is locked with the standard attached aiming arm in a typical manner. Attention is then directed to the free end of the nail requiring locking. We then move the image intensifier to obtain perfect circles of the locking holes by rotating and abducting/adducting the femur as required. It is at this point we change from our standard procedure. We ensure the centered laser pointer on the image intensifier is in the “on” position and is functional. We then center the perfect circle in the absolute center of the viewing monitor. Next, we point our scalpel at the center of the locking hole under fluoroscopic guidance. We then move the image intensifier’s laser to the tip of the scalpel, which now marks the center of the locking hole (Fig. 1). The laser pointer is now in the exact trajectory of the intended locking screw with a laser dot on the skin in the correct place to make a skin incision.

FIGURE 1:

A perfect circle x-ray is obtained with the scalpel in the center of the locking hole, the laser is then moved to the tip of the scalpel. This will place the locking hole in the absolute center of the viewing monitor.

We then use a scalpel and make a skin incision over the laser point on the skin. Blunt dissection is then used to dissect down to the bone and then the appropriate drill is inserted into the incision. The drill is then placed in the center of the locking hole in typical perfect circles manner. We then move the drill to be in-line with the c-arm beam and adjust it so that the laser pointer is in the center of the back of the drill. Now that the laser is colinear with the drill, we are ensured that the drill hole will be in the exact right position for the locking screw (Fig. 2). Complete the locking of the nail by finishing your drill hole, measuring, and placing the appropriately sized interlocking screw (Fig. 3). See supplemental video part 1 to 3 for complete technique (Supplemental Digital Content 1, https://links.lww.com/TIO/A69, Supplemental Digital Content 2, https://links.lww.com/TIO/A70, Supplemental Digital Content 3, https://links.lww.com/TIO/A71).

FIGURE 2:

This image demonstrates how the drill, drill tip, and screwdriver are perfectly aligned with the laser of the image intensifier.

FIGURE 3:

The final result is a successfully placed locking screw.

COMPLICATIONS

The perfect circle technique works well but can result in extensive radiation exposure and operative time. A study by Sanders et al2 demonstrated radiation exposure to the surgeon was 2.6× more when a free-handed technique was used for placing locking screws in femoral IMNs. Additional complications include errantly placed screws and damage to the implant. Errantly placed locking screws can end up outside of the locking hole, which defeats the purpose of the screw. Also, drilling off-axis can widen the near cortex and lead to off-axis placement of screws, which, compromises the mechanical integrity of the screw-bone interface and screw-device integrity, respectively. Lastly, the improper trajectory of the drill tip can damage the IMN which can lead to implant damage or failure.

These complications have led manufacturers to create extended aiming arms and tools to help assist in the placement of these locking screws. These devices are not universally available and can have a significant financial burden. Numerous studies have shown no significant difference in operative time or the success of screw placement.3,4

EXPECTED OUTCOMES

Using our adaptation to the traditional perfect circle technique is an easy maneuver that can lead to increased success. The primary advantage of this trick is that it easily facilitates free-hand placement of locking screws. In addition, it quickly helps find the correct drill trajectory and screw path. This technique is simple and reproducible and requires no additional large equipment. It is not limited to any particular manufactured nail or anatomic location. This maneuver should be in all orthopedic surgeon’s armamentarium.

REFERENCES 1. Conway D, Albright P, Eliezer E, et al. The burden of femoral shaft fractures in Tanzania. Injury. 2019;50:1371–1375. 2. Sanders R, Koval KJ, DiPasquale T, et al. Exposure of the orthopaedic surgeon to radiation. J Bone Joint Surg Am. 1993;75:326–330. 3. Ehlinger M, Dillman G, Czekaj J, et al. Distal targeting device for long Gamma nail(®). Monocentric observational study. Orthop Traumatol Surg Res. 2013;99:799–804. 4. Yoo JI, Jeong H, Na J, et al. Comparison of intraoperative radiation exposure with and without use of distal targeting device: a randomized control study. Arch Orthop Trauma Surg. 2019;139:1579–1586.