Diagnosis of Femoral Neck Fractures in Patients with a Femoral Shaft Fracture: Improvement with a Standard Protocol

Tornetta, Paul III MD; Kain, Michael Sean Hillegass MD; Creevy, William R. MD

Journal of Bone & Joint Surgery - American Volume:
doi: 10.2106/JBJS.F.00297
Scientific Articles
Abstract

Background: An ipsilateral fracture of the femoral neck is seen in association with 1% to 9% of femoral shaft fractures, and 20% to 50% of these injuries are missed initially. Recognition of an associated femoral neck fracture prior to stabilization of the femoral shaft fracture is imperative to avoid or minimize complications of displacement and osteonecrosis.

Methods: A protocol to look for a femoral neck fracture in all patients with a femoral shaft fracture was instituted at a single level-I trauma center. This protocol consisted of a dedicated anteroposterior internal rotation plain radiograph, a fine (2-mm) cut computed tomographic scan through the femoral neck, and an intraoperative fluoroscopic lateral radiograph prior to fixation as well as postoperative anteroposterior and lateral radiographs of the hip in the operating room prior to awakening the patient. A chi-square analysis comparing pre-protocol and post-protocol fracture prevalences was used to assess the relative risk of missing an associated femoral neck fracture.

Results: Two hundred and sixty-eight consecutive patients with a femoral shaft fracture formed the basis of the study group. Of 254 who were followed for at least two months, sixteen were identified as having an associated ipsilateral femoral neck fracture with use of the protocol. Thirteen associated femoral neck fractures were identified before the patient entered the operating room for definitive fixation, and twelve of them were identified with the fine-cut computed tomographic scan. One fracture was identified intraoperatively. There was one iatrogenic fracture and one delayed diagnosis of a femoral neck fracture. With this protocol, we reduced the delay in diagnosis by 91% as compared with our experience in the year prior to the initiation of the protocol.

Conclusions: In the presence of a femoral shaft fracture, evaluation of the femoral neck with fine-cut computed tomography and dedicated internal rotation hip radiographs significantly improves the ability to diagnose an associated femoral neck fracture.

Level of Evidence: Diagnostic Level II. See Instructions to Authors for a complete description of levels of evidence.

Author Information

1 Department of Orthopaedics, Boston Medical Center, 850 Harrison Avenue, Dowling 2 North, Boston, MA 02118. E-mail address for P. Tornetta: ptornetta@pol.net. E-mail address for M.S.H. Kain: mikain@bmc.org

Article Outline

Afemoral neck fracture occurs in association with 1% to 9% of blunt femoral shaft fractures1-3. These injuries typically occur in association with fractures with substantial comminution, a reflection of the high energy required to cause failure of the femoral neck in a young patient. In a recent review of 722 reported cases of ipsilateral traumatic injury of the femoral neck and shaft, Alho reported that, on the average, 30% of these injuries were not identified during the initial assessment1. Although iatrogenic fractures of the femoral neck can occur during antegrade femoral nailing4, a recent report by Riemer et al. noted a 31% prevalence of “clandestine” or missed injuries in a series of patients who had been treated with plate fixation for a femoral shaft fracture2. This percentage is similar to that seen in series of femoral shaft fractures treated with intramedullary nailing and supports the notion that these fractures are most likely present from the time of injury. Somewhere between 25% and 60% of ipsilateral femoral neck fractures are nondisplaced at presentation, strengthening the contention that delayed diagnosis is more common than iatrogenic fracture5. Because the complications of osteonecrosis of the femoral head and nonunion of the femoral neck are more severe than those of the management of the femoral shaft fracture, attention to the neck injury is paramount3,5. Prompt recognition and treatment of the femoral neck fracture provides the best chance to obtain a good result and prevent late displacement, osteonecrosis, and femoral neck nonunion3,6,7. The purpose of this study was to report on the impact of a diagnostic protocol designed to reduce the delay in diagnosis of an ipsilateral fracture of the femoral neck in patients with a femoral shaft fracture.

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Materials and Methods

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Over a one-year period at a single level-I center, seven (9%) of eighty-two patients with a femoral shaft fracture had an associated femoral neck fracture. Four of those fractures were not diagnosed during the preoperative work-up or the operative session; they were detected only after the patient had left the operating room. Three of these four fractures were displaced when they were diagnosed and required repeat surgical intervention. During this time, the work-up for a femoral neck fracture was left to the treating surgical team without a standardized protocol. On the basis of the delayed diagnosis of these injuries, a best-practice protocol was developed by the attending trauma surgeons for the evaluation of the femoral neck in patients with a femoral shaft fracture. This protocol includes a preoperative anteroposterior internal rotation plain radiograph of the hip, a fine (2-mm) cut computed tomo-graphic scan through the femoral neck (as a part of the initial trauma scan), and an intraoperative fluoroscopic lateral evaluation of the hip just prior to fixation of the femoral shaft. In addition, postoperative anteroposterior and lateral radiographs of the hip are made in the operating room, to specifically evaluate the femoral neck, before the patient is awakened. At the time of follow-up, all patients were asked about the presence of hip pain, and anteroposterior and lateral radiographs of the femur were made with the hip visualized on all images. Any mention of hip pain prompted evaluation with a plain tomo-gram. All images were evaluated by the surgeon of record and were reviewed again by the senior author (P.T.) the following morning.

By two months, all patients were bearing at least 50% of their weight on the affected lower limb.

Approval from our institutional review board was obtained for this retrospective review of the results of this protocol.

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Results

A consecutive series of 268 patients with a femoral shaft fracture was seen after institution of the protocol. Two hundred and fifty-four patients were followed for a minimum of two months, which we assumed to be a sufficient amount of time for a missed fracture to be visible on radiographs and diagnosed. Nineteen (7.5%) of the 254 patients had an ipsilateral femoral neck fracture. These patients included fourteen men and five women with an average age of thirty-five years (range, nineteen to fifty-six years). Three patients were referred to our center specifically for management of the associated femoral neck and shaft fractures—i.e., the diagnosis had already been made before they were seen at our institution; one of those fractures had displaced after intramedullary nailing, and the other two were minimally displaced and had been identified preoperatively. Sixteen fractures presented primarily, after the patient was taken to our institution from the injury scene, and were evaluated with the standardized protocol. The protocol was used for all patients who were seen with a femoral shaft fracture at our institution after the protocol was instituted. Of the sixteen fractures, thirteen were identified preoperatively, one was identified intraoperatively, one was classified as iatrogenic, and one was not identified even though the guidelines of the protocol had been followed.

The one nondisplaced iatrogenic fracture was diagnosed six weeks postoperatively with plain tomography. As dictated by the protocol, a plain tomogram was made in the clinic because the patient reported having hip pain while walking. Careful review of the preoperative and postoperative hip radiographs and preoperative fine-cut computed tomography scan still did not identify the fracture. During antegrade intramedullary nailing of the femoral shaft fracture, the surgeon noted that the piriformis starting portal was difficult to create and that the narrow sharp awl needed to be struck harder than is normally necessary to breach the cortex. Thus, the femoral neck fracture is believed to have been an intraoperative iatrogenic fracture (Figs. 1-A and 1-B).

One patient had a delay in diagnosis; i.e., the femoral neck fracture was diagnosed after the first operative session. In retrospect, this fracture was visible on two of the computed tomography cuts as a nondisplaced unicortical crack and was not visible on the plain radiographs made preoperatively or postoperatively. Even in retrospect, we doubt that the crack would have been identified as a fracture preoperatively and therefore we are counting it as a missed fracture. It was visible as a minimally displaced fracture on radiographs made one week after the surgery, but it was not recognized by the radiologist or the physicians in the rehabilitation facility. It was displaced when the patient was seen in the orthopaedic clinic at three weeks (Figs. 2-A, 2-B, and 2-C).

One femoral neck fracture was identified in the operating room after antegrade nailing and was treated with screws placed around the nail during the same operative session. We are unsure if this was an iatrogenic injury or if it was a nondis-placed fracture that was made more evident by the nailing procedure.

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The other thirteen fractures were diagnosed preoperatively and were treated during the first operative session. Computed tomographic scanning was the best screening tool in this group of patients as it identified twelve of the thirteen fractures, whereas eight of the thirteen fractures were visible on the dedicated preoperative internal rotation hip radiographs. These eight fractures included the one for which the computed tomographic scan was nondiagnostic. In that case, the computed tomographic scan was of poor quality as the patient had moved, creating substandard, blurred images.

A chi-square analysis comparing the group of patients with a femoral shaft fracture who were screened with the protocol with the group of eighty-two patients with a femoral shaft fracture who were screened without the protocol demonstrated a significant difference in the detection of an associated femoral neck fracture (p = 0.018; Table I). At our institution, the protocol reduced the rate of delay in diagnosis of an associated femoral neck fracture by 91% (confidence interval, 27% to 99.9%).

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Discussion

It is imperative that femoral neck fractures be diagnosed and managed early. Their common association with blunt femoral shaft fractures requires a high index of suspicion on the part of the treating surgeon. Although this association is well known and up to 9% of femoral shaft fractures may be associated with an ipsilateral femoral neck fracture, several authors have reported a high prevalence of late diagnosis (20% to 50%)1,8-14. Similarly, during a one-year period at our institution, four of seven femoral neck fractures associated with a femoral shaft fracture were diagnosed postoperatively, after the patient had been taken out of the operating room. This was during a time when the preoperative and postoperative work-up for the injury was left to the discretion of the treating surgeon and no consistent regimen was followed. After a review of these cases, a best-practice policy was adopted; this included a dedicated anteroposterior internal rotation hip radiograph and a fine-cut computed tomographic scan of the hip made preoperatively, intraoperative lateral fluoroscopy, and postoperative plain anteroposterior and lateral radiographs of the hip made in the operating room immediately after management of the femoral shaft was completed.

It has been demonstrated that evaluation of these fractures with plain radiographs can be nondiagnostic 19% to 50% of the time when the majority of the fractures are minimally or nondisplaced15. The use of a computed tomographic scan as a screening tool was initially reported by Hughes et al., in a single case report16, and was later validated by Yang et al.15, who reported that fourteen of 152 femoral shaft fractures were associated with an ipsilateral femoral neck fracture. Of these fourteen fractures, eight were not seen on plain radiographs, but six were seen retrospectively on abdominal computed tomographic scans reset to bone windows. The other two fractures were thought to be iatrogenic.

Riemer et al. made a specific recommendation that immediate postoperative hip radiographs be part of the regular evaluation of patients treated for femoral shaft fracture2. This was based on the cases of ten patients who had an ipsilateral femoral neck fracture that was not diagnosed preoperatively; those cases accounted for 31% of the patients with this constellation of injuries in their series of more than 500 patients with a femoral shaft fracture. It is important to note that, in their series, the femoral shaft fractures were treated with plate fixation, minimizing the possibility of iatrogenic fracture of the femoral neck.

We adopted these recommendations, with the modification of performing the computed tomography of the femoral neck with use of fine cuts (of 2 mm). These images are obtained, as a matter of protocol, as part of the initial trauma abdomen-pelvis computed tomographic scan for patients with a femoral shaft fracture. The step of making postoperative hip radiographs in the operating room was added to avoid a delay in recognizing iatrogenic fractures or the displacement of unrecognized fractures. We believe that iatrogenic fractures or the displacement of unrecognized fractures could occur during antegrade nailing (through a starting portal) or retrograde nailing (by axial loading during nail placement); both situations had been observed during the prior year.

The protocol that we described was effective in identifying fourteen of sixteen fractures. Thirteen were diagnosed preoperatively, and one was identified after nailing but during the initial operative session. We consider one of the two remaining fractures to be iatrogenic and the other to be a delay in diagnosis. Thus, with this protocol, we were able to reduce the risk of delaying the diagnosis of an associated femoral neck fracture by 91%. However, we still had a delay in diagnosis of one nondisplaced fracture.

Of the different components of the protocol, the fine-cut computed tomographic scan was the most helpful. The preoperative dedicated internal rotation hip radiograph allowed us to identify only one fracture that we had missed on the computed tomographic scan. In that case, the computed tomographic scan was thought to be of poor quality as a result of patient movement artifact.

Identification of an associated femoral neck fracture preoperatively is critical for preoperative planning for patients with a femoral shaft fracture. Most authors have recommended separate fixation of the femoral neck and the femoral shaft, with the most attention paid to the reduction and fixation of the femoral neck fracture5,8,9,17,18. The use of preoperative computed tomography and postoperative hip radiographs in the operating room is valuable for identifying nondis-placed and iatrogenic femoral neck fractures and for reducing the risk of delaying the diagnosis of an associated femoral neck fracture10,15. ▪

Disclosure: The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Investigation performed at the Department of Orthopaedics, Boston Medical Center, Boston, Massachusetts

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