Correcting varus malreduction in extracapsular fractures of the neck of the femur using a temporary external fixator

Background

Extracapsular fractures of the femoral neck are increasingly being managed with cephalomedullary nails (CMNs).¹ Varus malreduction is a recognised complication of such devices, leading to reduced offset and defunctioning of the abductors, and increasing of the moment arm across the fracture, risking gait disturbance, non-union and metalwork failure. We describe a simple and efficient method for both correcting and maintaining the varus deformity while the surgeon and assistant prepare the femur and position the CMN, using two Schanz pins and a single external fixator bar.

Technique

After routine setup and preparation of the patient on the traction table, place a 4.5mm Schanz pin through the greater trochanter into the anterior femoral head (Fig 1). Applying a force in the caudal direction allows correction of the varus deformity (Fig 2). A second Schanz pin is subsequently placed from lateral to medial in the distal femur, slightly anterior or posterior to the medullary canal. With the reduction initially obtained and held by hand, these pins can then be linked with a single external fixator bar, thereby maintaining the deformity correction (Fig 3). Following this, the CMN can be inserted in the standard technique and locked proximally (Figs 4–6), before removal of the temporary external fixator and distal locking of the nail (Fig 7).

Figure 1.

Insertion of proximal Schanz pin

Figure 2.

Correction of varus deformity with caudally directed force

Figure 3.

The external fixator in action

Figure 4.

Insertion of shaft guidewire

Figure 6.

Insertion of the blade prior to Schanz pin removal

Figure 7.

Nail and blade in situ with varus angulation corrected

Figure 5.

Insertion of the neck guidewire

Discussion

Several techniques have been described to help surgeons reduce the risk of varus malreduction,^2–4 and modern CMNs are designed with a lateral bend to allow trochanteric entry and avoid varus. However, these focus on entry point and rely on the surgeon achieving a good closed reduction. In some cases (eg severely comminuted or reverse oblique fractures), this correction is unachievable, and closed and open reduction techniques might be required, increasing operative time, blood loss and infection risk. Our method eliminates varus malalignment as well as freeing up the hands of both the surgeon and the assistant to insert the fixation device. We have described this technique using a long CMN but it could equally be applied to a short CMN.