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Tips and Pearls

Femoral Derotation for the Acutely Malrotated Femur Following Intramedullary Nail Fixation

Sloan, Matthew MD, MS; Lim, Daniel MD; Mehta, Samir MD

Author Information
doi: 10.1097/BTO.0000000000000359
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Abstract

Treatment of femoral shaft fractures with intramedullary nails can be a challenging procedure if the fracture site is transverse or comminuted. In these scenarios proper rotation of the femoral shaft can be difficult to discern. Techniques for primary intramedullary nail fixation and intraoperative judgment of rotation in these settings have been discussed previously.1,2

Despite numerous techniques for assessment of rotation intraoperatively, 28% of patients treated with intramedullary nail fixation of femoral shaft fractures demonstrate malrotation of >15 degrees.3 Malrotation of >10 degrees following femoral shaft fracture fixation has been shown to be symptomatic, with reduced functional score and tolerance of daily activities such as climbing stairs.4

There is limited discussion of techniques for derotating the postoperative patient with clinically significant malrotation. We provide a case report of a technique for derotation of the malrotated femoral shaft.

CASE REPORT

Our patient is a 23-year old, otherwise healthy male, with no significant past medical history or family history. He presents 1 week following motor vehicle accident, during which he sustained a right midshaft femur fracture that was subsequently treated with intramedullary nail fixation. Postoperatively the patient was noted to have a clinical examination concerning for external malrotation of the femur. Upon examination, the right foot was externally rotated at rest compared with the contralateral side, and clinical examination for hip rotation demonstrated a 30 to 40 degree internal rotation deficit on the operative side.

Preoperative anteroposterior (AP) and lateral x-ray images of the right lower extremity indicate step-off at the fracture site (Fig. 1). Computed tomographic (CT) scan was obtained of the bilateral femurs to more accurately assess torsion of the femur and malrotation. A horizontal reference line is drawn across the axial cuts using the bed of the CT scanner to compare contralateral limbs. Anteversion is measured as the positive angle up from reference along the axis of the femoral neck. If this angle is negative, it represents relative retroversion of the femoral neck. Next, we continue scrolling to the axial image of each distal femur to demonstrate the greatest prominence of the posterior femoral condyles. Keeping the horizontal reference line constant, a tangential line is drawn across the posterior condyles and defines the angle of relative internal or external rotation. Combined femoral torsion is calculated on each femur as the angle that would be measured at the posterior condyle if the version of the femoral neck were rotated to neutral (eg, a femur with 10 degrees of anteversion at the femoral neck and 30 degrees of external rotation distally would have a combined femoral torsion of 20 degrees external rotation after the femur is internally rotated 10 degrees to position the neck at neutral version). Femoral torsion can then be compared between contralateral sides.

FIGURE 1
FIGURE 1:
Preoperative anteroposterior and lateral x-ray and computed tomographic scan of femur following intramedullary nail fixation.

Anteversion of the right femoral neck measured 10.9 degrees, while the ipsilateral femoral condyles measured external rotation of 39.2 degrees, for a combined femoral torsion of 28.3 degrees of external rotation distally. The left, uninjured side, femoral neck anteversion measured 2.0 degrees, while the contralateral femoral condyles measured 13.7 degrees of internal rotation, for a combined femoral torsion of 15.7 degrees of internal rotation distally (Fig. 1). Comparing the injured and uninjured limbs, the femoral malrotation totaled 44.0 degrees of external rotation in the distal segment.

We discussed the issue with the patient at length, with attention to this substantial malrotation and risk for progressing to symptomatic malunion. Following this discussion, the patient elected to undergo a derotation procedure to improve his femoral torsion. We proceeded to the operating room, ensuring all equipment for adjusting the intramedullary nail was available, as well as 5.0 mm Schanz pins for performing the derotation procedure.

The patient was placed supine on a radiolucent table, and following induction, the patient’s uninjured limb was imaged fluoroscopically with a C-arm. We first obtained a perfect lateral of the knee, then holding the limb completely still, brought the C-arm to the hip and rotated up 75 degrees for an AP view of the femoral neck. Rotating up 75 degrees from a true lateral of the knee takes into account the average 15 degrees of anteversion of the femoral neck. It is the equivalent of rotating up 90 degrees to a true AP of the hip, then rotating back 15 degrees to remove the femoral neck anteversion and view the neck en face (Fig. 2). Both these films were saved for intraoperative comparison following derotation.

FIGURE 2
FIGURE 2:
Fluoroscopic images of uninjured femur preoperatively for intraoperative comparison.

Both lower extremities were then prepped and draped in the usual sterile manner. A 5.0 mm Schanz pin was placed proximally in the femur adjacent to the intramedullary nail in the intertrochanteric region in the sagittal plane. A second 5.0 mm Schanz pin was placed distally in the femur adjacent to the intramedullary nail in the supracondylar region, parallel to the proximal pin. To achieve exact parallel orientation between Schanz pins a sterile level or free-swinging weighted goniometers (available at our hospital) can be used to confirm both pins are placed perpendicular to the floor. If pins are not exactly perpendicular to the floor, the difference must be accounted for during the correction.

Thereafter, adjustment for external malrotation was performed. The distal interlocking screws were removed from the intramedullary nail, then the distal segment was internally rotated until the distal pin measured 40 degrees from the proximal pin, as measured with a sterile goniometer (Fig. 3). Using a sterile level or a free-swinging sterile goniometer attached to the Schanz pin, as correction is performed the degrees of correction are directly measured from the initial perpendicular. Correction continues until measurement confirms derotation equivalent to the value obtained on preoperative CT imaging.

FIGURE 3
FIGURE 3:
Clinical intraoperative view of Schanz pins following derotation maneuver to internally rotate distal segment 40 degrees.

Fluoroscopic images were then obtained of the operative limb in the same manner as the nonoperative limb. First, a perfect lateral of the knee was obtained. Then the C-arm was brought proximally to the hip keeping the leg completely still, and rotated over 75 degrees to obtain an AP of the hip (Fig. 4). This image was compared with the preoperative fluoroscopic images of the uninjured limb. Once adequate derotation of the femur is obtained, the distal interlocking screws were replaced. We are yet to experience a patient who has had difficulty or complication with the derotation maneuver. Most femurs are reamed 1.0-1.5 mm above desired intramedullary nail diameter at index surgery. We believe this allows adequate freedom for rotation and have not experienced significant difficulty or complication from derotation due to the canal being too tight. We have not required exchange to a downsized nail to perform this technique.

FIGURE 4
FIGURE 4:
Fluoroscopic images of injured femur intraoperatively following derotation for comparison with preoperative contralateral images (A). Intraoperative clinical assessment of bilateral femoral rotation (B).

The Schanz pins were removed and all wounds were closed. Final imaging was obtained to confirm alignment before awakening the patient. In addition, clinical examination of internal and external rotation of both limbs was performed to confirm improved femoral torsion (Fig. 4). Following surgery, a postoperative CT of bilateral lower extremities was repeated to confirm adequate radiographic correction of malrotation (Fig. 5). Repeat imaging demonstrated greatly improved femoral torsion, with external rotation of the injured limb within 5 degrees of the uninjured side.

FIGURE 5
FIGURE 5:
Postoperative computed tomography of bilateral lower extremities following derotation of malrotated intramedullary nail fixation of right femur.

The patient did well postoperatively and was discharged home on the second day after surgery.

DISCUSSION

Previous reports focus on the incidence of malrotation following intramedullary fixation of femoral shaft fractures and methods for intraoperative evaluation.1–4 These methods are helpful with regard to prevention of malunion at the index procedure setting. We present this case as a treatment following index surgery malrotation.

A case report was performed by Kent et al5 reviewing a series of patients with malrotation following femoral intramedullary nail. For derotation they reported on 2 cases that had derotation procedures after callus had formed. This was osteotomized through a lateral approach. K-wires were placed proximal and distal to the fracture at the measured preoperative malrotation angle and the femur was derotated about the intramedullary nail until the K-wires became parallel.

In comparison, we detail specific intraoperative fluoroscopic checks to confirm alignment, as well as use of the 5.0 mm Schanz pins, which can be used as levers to rotate the femur about the intramedullary nail. When using K-wires, they cannot be used to lever the fragments into proper rotational alignment. Setting the K-wires parallel to start and rotating a specified angle as we describe is an alternative method to that used by Kent, where the wires were set at a specific angle and then brought into alignment. Finally, we advocate addressing malrotation as early as possible, if noted soon after surgery in order to correct before callus formation and prevent the need for osteotomy. Of note, most femurs are reamed 1.0 to 1.5 mm above desired intramedullary nail diameter at index surgery. We believe this allows adequate freedom for rotation and have not experienced significant difficulty or complication from derotation due to the canal being too tight. We have not required exchange to a downsized nail to perform this technique.

This technique provides a useful option to the surgeon that finds early evidence of significant femoral malrotation.

REFERENCES

1. Sullivan M, Taylor R, Donegan D, et al. Length, alignment, and rotation: operative techniques for intramedullary nailing of the comminuted, diaphyseal femur fracture. UPOJ. 2014;24:31–35.
2. Herscovici D, Scaduto JM. Assessing leg length after fixation of comminuted femur fractures. Clin Orthop Relat Res. 2014;472:2745–2750.
3. Jaarsma RL, Pakvis DF, Verdonschot N, et al. Rotational malalignment after intramedullary nailing of femoral fractures. J Orthop Trauma. 2004;18:403–409.
4. Karaman O, Ayhan E, Kesmezacar H, et al. Rotational malalignment after closed intramedullary nailing of femoral shaft fractures and its influence on daily life. Eur J Orthop Surg Traumatol. 2014;24:1243–1247.
5. Kent ME, Arora A, Owen PJ, et al. Assessment and correction of femoral malrotation following intramedullary nailing of the femur. Acta Orthop Belg. 2010;76:580–584.
Keywords:

femoral malrotation; derotation; intramedullary nail; trauma

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