Operative Treatment of Femur Fractures Using a Greater Trochanteric Entry IM Nail

Jonathan H. Phillips

Fractures of the shaft of the femur are among the most common causes for admission of children to hospitals. Treatment of these fractures accounts for a significant percentage of surgical procedures that are performed to treat pediatric fractures. The incidence of pediatric femur fracture in the United States is approximately 19.15 per 100,000 annually. Higher figures have been quoted in the Scandinavian literature. Management of this injury has undergone a significant evolution in the past decade, with more emphasis given to operative management than previously. Several options exist for surgical management including external fixation, plating, elastic, and more rigid intramedullary (IM) nailing. This chapter describes a technique for antegrade fixation of children’s femur fractures with a nail introduced just lateral to the greater trochanter. It avoids the piriformis fossa and thus has the advantage of reducing the risk of avascular necrosis of the capital femoral physis.

INDICATIONS/CONTRAINDICATIONS

In general, antegrade nailing of children’s femur fractures through the greater trochanter is indicated for treatment of femoral shaft fractures in patients over the age of 8 with a fracture below the lesser trochanter but above the supracondylar area. Comminution and instability are not contraindications because proximal and distal interlocking screws achieve considerable stability of the fracture when treated with this technique. It is a useful alternative to elastic nailing especially in long oblique fractures, which tend to shorten over elastic nails. The described nail’s maximum diameter is 8.5 mm, so a minimal femoral canal diameter of 9 mm is advised. Attempting to insert this nail in canals smaller than 9 mm can lead to comminution, but this can be avoided by reaming of the canal if too tight. With a canal diameter above 9 mm, the nail is inserted without reaming the isthmus. Open fractures, after appropriate debridement, can be stabilized with this nail.

As yet, an upper age limit has not been defined. Though the nail is ideally suited for patients with open physes, it can also be used in the skeletally mature individual. In a heavy, older adolescent with
closed physes, however, consideration should be given to the use of available IM devices used to treat adults with a femoral shaft fracture. This is very much a load-sharing device and is conceived as an internal splint more rigid than elastic nails but not designed for immediate weight bearing.

PREOPERATIVE PLANNING

As in all trauma situations, the child with a femur fracture for whom the use of this nail is being considered should be thoroughly evaluated clinically. Particular emphasis is placed on the diagnosis of any concomitant knee or hip injuries. Preoperative orthogonal radiographs of the injured femur are necessary, and an anteroposterior pelvis radiograph, along with radiographs of the ipsilateral knee, is advisable.

Careful evaluation of the limiting diameter of the IM canal is mandatory. As mentioned above, because the minimum diameter of both the proximal end and the tip of this nail is 8.5 mm, a 9-mm canal is the smallest that can accommodate this device without IM reaming. The nail is usually inserted unreamed, though the IM canal can be reamed if necessary. In the indicated age group (older than 8 years), however, this technique is seldom needed.

Preoperative evaluation of the radiographs for occult fracture comminution will avoid surprises during the operation. It is common to have undisplaced fracture lines around the radiographically obvious fracture, particularly with a spiral fracture pattern. Often, a fracture extension distally toward the supracondylar region or proximally to the trochanters can be diagnosed before becoming clinically evident during nail insertion. As long as these fracture line extensions are recognized, allowance for them can be achieved by modifying the surgical technique. For instance, if there is concern about comminution of the fracture by the nail in a very complex fracture pattern, a mini-open technique with temporary bone clamp stabilization of the fracture during nail insertion may be useful.

Certain fracture patterns are more troublesome for nail insertion. The proximal subtrochanteric fracture typically leads to an underestimation of the degree of displacement in both the axial and the sagittal planes. The deforming force of the psoas muscle pulls the proximal fragment into external rotation and sometimes into marked flexion. With a more “parallel to the ground” approach using reamers and awls, the thin posterior cortex of the intertrochanteric area can be easily breached, causing unnecessary delay and intraoperative revision of the nail’s entry pathway. Thorough preoperative evaluation will usually allow the surgeon to anticipate this potential problem, which can be minimized by placing the patient on the fracture table with flexion of the hip. In addition, starting the entry point for the nail more posteriorly and aiming the guide pin for the proximal entry point anteriorly (toward the ceiling) will be helpful in these proximal femur structures.

For the more distal femoral shaft fracture, the preoperative planning must be especially thorough. Depending on the fracture configuration (transverse, oblique, or spiral), this nail in its present iteration is not suitable for fractures more distal than 4 cm proximal to the distal femoral physis, particularly in a large femur with a capacious distal IM canal in which little stability of the fracture will be achieved, even with a firm distal interlocking screw.

SURGICAL PROCEDURE

After an appropriate preoperative evaluation of any comorbid factors, the patient is taken to the operating room, where a fracture table has been set up and fluoroscopy is available. Preoperative prophylactic antibiotics are given. General anesthesia and complete muscle paralysis are preferable for ease of fracture reduction. A closed reduction of a widely displaced fracture is advisable, as this will greatly simplify instrumenting the femur and passing the nail. During this maneuver, any buttonholing of fracture fragments through the quadriceps may be diminished or actually eliminated. By looking at the fluoroscopic images at this stage, one can get a sense of how much persistent soft-tissue interposition is present and whether a small open reduction incision is likely to be needed. The patient’s foot on the injured side is then placed in the traction boot. The well leg is held abducted flexed and slightly externally rotated in a holder. Under fluoroscopic control, traction is applied to align the fracture linearly. Care must be taken not to overdistract the fracture or apply too much tension; in smaller children, it is especially easy to distract the hip joint, and significantly imaging the hip joint at this point will help avoid this problem. In addition, excessive pressure of the perineum against the fracture table’s perineal post is well recognized as a cause of possible pudendal nerve palsy. The incidence of this complication is minimized by wrapping the post with cotton padding and by not overdistracting with traction. Rotational alignment of the fracture is assessed by matching diameters of the proximal and distal fragments on fluoroscopy and studying the fracture ends interdigitation and the profile of the knee and the proximal femur as seen radiographically.

Assuming the fracture is adequately aligned and the well leg is appropriately positioned for unobstructed fluoroscopic access (Fig. 11-1), the injured, the thigh and adjoining areas are prepped and draped according to the surgeon’s preferences. Any open wounds of the thigh should then be debrided and irrigated. The approach to the entry point in the greater trochanter should be made so that the guide pin for the trochanteric reamer enters the middle of the intertrochanteric portion of the canal (Fig. 11-2).

On the anteroposterior fluoroscopic image, the guide pin should pierce the lateral aspect of the greater trochanter about 5 mm below the tip. The guide pin should not be placed centrally in the apex of the greater trochanter, as this brings the reamer too close to the femoral head vascular supply that is coursing through the piriformis fossa. In addition, the angle of the guide pin to the long axis of the femur should be 30 degrees or so to ensure that the shaft of the nail, when inserted, is medialized in the capacious upper end of the femur. This allows full seating of the threads of the proximal interlocking screw.

A small open incision at the greater trochanter is advisable the first few times a surgeon uses this device so that direct palpation of the trochanter can be made. After familiarity is achieved with this local anatomy, a percutaneous technique is easily achieved (Fig. 11-3); after appropriate positioning of the guide pin, the 9-mm reamer is used to open the lateral cortex of the trochanter, avoiding drilling the calcar as pedestal formation here will block passage of the nail (Fig. 11-4

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