Abstract
This article presents a practical technique for distal intramedullary nail locking based on fluoroscopic triangulation. Unlike traditional methods, which require precise orientation of the C-arm to obtain perfect circles on radiographs, this approach allows locking to be performed with less radiation exposure and surgical time. The technique does not require additional equipment. It is thus proposed as a safe and efficient technique for distal locking.
How to cite this article
Barroso MM, Blanco JC, de Armas JN, et al. A Trigonometric Technique for Distal Locking of Intramedullary Nails without the Need for Specific Instrumentation. Strategies Trauma Limb Reconstr 2025;20(1):47–49.
Keywords: Blocking screw, Deformity correction, Distal locking, Internal lengthening nail, Intramedullary nail, Limb lengthening, Long bone fracture, PRECICE, Surgical technique
Aim and Background
Intramedullary nails are essential tools for the treatment of long bone fractures and non-unions, limb lengthening, and deformity correction.
Proximal locking with the aid of jigs attached to the nail is usually straightforward. However, distal locking is performed freehand, consuming more surgical time and increasing radiation exposure. Locking is achieved by radiographically visualising perfect circles. Achieving the required C-arm position can be difficult at times due to patient position, particularly to obtain a perfect lateral oriented with the locking bolt holes. Although multiple methods have been described, including techniques to minimise the number of attempts required, difficulties are often encountered.1
We propose a technique based on radioscopic triangulation that may be useful in certain situations and does not require additional tools.
Technique
The described method used in our clinical practice for distal locking is based on geometric triangulation. The leg is placed on a radiolucent table, slightly elevated with respect to the contralateral limb to avoid overlapping in the lateral radiograph. The fluoroscopy machine is brought in from the patient's feet and oriented 30–40º cranially (Fig. 1). This orientation allows the surgeon to maintain the position when obtaining the lateral radiograph in the next step.
Fig. 1.
Fluoroscope position relative to the patient for an AP radiograph, with the body at the feet and at 30–40º of angulation for the surgeon's comfort. The patient's leg is slightly elevated to avoid overlapping with the contralateral leg in the subsequent lateral radiograph
An anteroposterior (AP) radiograph of the nail is then taken, rotating the fluoroscope to obtain a perfect circle of the AP locking hole. Lateral-to-medial locking is at 90 degrees to this. Once this is achieved, the drill is positioned aligned with the lateral-to-medial locking bolt hole, giving the correct craniocaudal orientation (Fig. 2). Next, the fluoroscope is rotated to the lateral plane, leaving space for the surgeon (Fig. 3). This plane shows the AP orientation of the nail. The drill tip is then moved anterior or posterior as required to match the centre of the nail, and the angle of approach changed until the drill bit is parallel with the nail (Fig. 4). It is not necessary to achieve a perfect circle in distal holes on the lateral projection, saving surgical time and radiation exposure time.
Fig. 2.
On the left, the drill bit position with respect to the lateromedial hole in an AP orientation of the nail. On the right, an illustration of the fluoroscope position with the body at the feet and in an oblique direction to the leg
Fig. 3.
Position of the fluoroscope for a lateral radiograph, leaving space for the surgeon
Fig. 4.
On the left, a lateral radiograph showing the drill bit and nail parallel. Note that the circles are not perfect in this plane, since being an oblique projection, the circumferences of the medial and lateral holes overlap. In the centre, the drill is oriented parallel to the nail. On the right, a schematic showing the orientation of the fluoroscope relative to the nail and the surgeon
Being careful not to change position of the drill, the image intensifier is returned to the AP position to confirm the trajectory remains appropriate in this plane, and the hole is drilled. As with other techniques, if perfect orientation is not achieved and the drill bit contacts the nail, the drill driver can be removed, and the bit advanced to the far cortex by careful hammering. Care is taken not to cross the far cortex because of the risk of fracture. Once the position is confirmed, the driver should be reattached, and the far cortex drilled as usual.
This procedure can be repeated for further locking holes as required.
Discussion
There are numerous techniques for performing distal locking of intramedullary nails. Traditionally, the hands-free technique is the most used. It requires a radiolucent viewer and considerable exposure time until perfect circles are achieved and the drill bit is properly oriented. More modern techniques, such as electromagnetic-guided locking (SURESHOT, Smith & Nephew), allow this radiation to be reduced but require specific equipment and are only applied to tibial nails. Moreover, they have not been shown to decrease surgical time when compared to the hands-free method in experienced surgeons.2–4
Other techniques described include the use of laser guides on the fluoroscope that mark the centre of the perfect circle, although they require calibration of the guide on the device with each patient and do not guide the orientation of the drill, only the entry point.5 The “nail-on-nail” technique is based on the use of two parallel nails, one intramedullary and one reference nail for distal locking. However, it requires reaming 1.5 mm more than the diameter of the nail to avoid deformation during nail insertion, as well as the additional cost of using two nails.6 Other techniques, such as endoscopic illumination and augmented reality, while interesting concepts, have not yet been applied in patients.7–9
We propose this technique as an alternative that does not require specific material or a long learning curve and is applicable in any intramedullary nail that offers distal locking.
Conclusion
To our knowledge, the technique explained here has not been previously described. It may be useful in case where difficulties arise with locking bolt insertion during surgery, particularly in orienting the C-arm to achieve perfect circles. In certain scenarios, this technique may be preferred as the initial approach.
Orcid
Muñoz Barroso M https://orcid.org/0009-0006-3505-7869
Cabello Blanco J https://orcid.org/0000-0002-3058-3353
Ron Marqués A https://orcid.org/0009-0004-6436-4572
Gaspar G Morán https://orcid.org/0000-0001-9292-6676
Footnotes
Source of support: Nil
Conflict of interest: None
References
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