Femoral Neck Stress and Insufficiency Fractures Treatment & Management

Updated: Mar 18, 2020
  • Author: Michael S Wildstein, MD; Chief Editor: William L Jaffe, MD  more...
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Treatment

Approach Considerations

Indications

In 1965, Devas instituted a classification scheme for fatigue fractures, based on prognosis and radiographic appearance. [34] His system split stress fractures into two types: compression and transverse (tension).

Compression fractures are the less serious of the two types and are seen most frequently in younger adults. These fractures are considered stable and may be treated with several days of rest followed by a period of protected weightbearing. Nonoperative management of these fractures necessitates frequent radiographs because late displacement, a potentially catastrophic complication, has been reported in the literature.

In select instances, if athletes with a known compression-type fracture continue to participate in strenuous activities, the lesion may progress to the level of the superior femoral neck and become a complete and, in the worst instance, displaced femoral neck fracture. Situations in which a physician may opt for prophylactic treatment of a compression-type fracture on an expectant basis include those in which patients experience metabolic bone processes that weaken the femoral neck's structural properties.

Transverse fractures, by contrast, are more commonly seen in the elderly population and carry a 10-15% possibility of displacement, with subsequent avascular necrosis (AVN) of the femoral head. A displaced femoral neck is one of the few true orthopedic emergencies, owing to the disastrous outcomes associated with AVN.

Transverse fractures appear on an internally rotated anteroposterior (AP) radiograph as a crack at the superior femoral neck. One can see sclerosis of the underlying bone, along with cortical deficiency. Over a period of days to weeks, these fractures may become complete, and callus formation may become evident over time.

Surgical treatment is warranted for all stress fractures that have progressed to a transverse fracture of the femoral neck. The question then becomes which treatment procedure is more beneficial to the patient. The orthopedist may choose either internal fixation or arthroplasty.

The decision-making process should include consideration of the patient's bone quality, life expectancy, physiologic status, and overall activity level. However, the main factor in deciding which type of repair to undertake should be the likelihood of revision surgery being needed in the future for a failed arthroplasty. For most younger individuals in otherwise good health, this means that internal fixation of the fracture is warranted.

Indications for hemiarthroplasty include such factors as pathologic bone, rheumatoid arthritis, renal failure or other chronic illness, and limited lifespan.

In the elderly population, osteoporosis becomes increasingly prevalent, resulting in decreased bone fatigue strength. When bone fails under physiologic loads in this population, it may be termed an insufficiency fracture. The differentiation between stress and insufficiency fractures lies in the bone's capacity to resist fracture under physiologic strains.

Contraindications

In general, nondisplaced compression-type femoral neck fractures are relative contraindications for surgery. In contrast, tension-type stress fractures demand surgical treatment because they have a high propensity for fracture displacement.

Contraindications for surgical fixation of a tension-type femoral neck fracture are few because this is one of the few true orthopedic surgical emergencies. If a displaced femoral neck fracture occurs, the very real possibility of disruption of blood supply to the femoral head makes surgery necessary.

Absolute contraindications include a medically unstable patient who would be unable to tolerate the stress of surgery and anesthesia. If initial operative fixation is not obtained and osteonecrosis ensues, the patient, when stabilized, will require a hemiarthroplasty as definitive treatment.

Future and controversies

There has been debate over the surgical treatment of transverse-type femoral neck stress fractures in older patients. Given that most individuals who sustain true stress fractures (as distinguished from insufficiency fractures) are young and healthy, only a small number of individuals are affected by this controversy.

The two current methods of fixation are internal fixation and prosthetic replacement. Multiple studies comparing the two fixation modalities for these types of injuries have demonstrated widely varying results. Infection rates, morbidity, mortality, and patient satisfaction have been examined without a definitive answer having been gleaned. Additionally, opponents of prosthetic replacement point out that the cost and potential complications of the components are not justifiable for individuals whose remaining life expectancy might be half that of the implant.

As the population ages and more individuals live longer, healthier lives, this debate is certain to continue. In addition, although the principles of fixation will likely remain the same, how they are applied to an individual today will probably differ from how they are applied a decade from now.

Materials are certain to continue to advance, and with an increasingly active population, the demands placed on the human body and on prosthetics remain to be seen. Only time and experience will bring the answers to these questions.

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Medical Therapy

Nonsurgical therapy is reserved for compression-type fractures or for patients whose medical condition precludes surgery because, unless further trauma is sustained, they are at low risk of displacement. Treatment employs mobilization and limited weightbearing using either crutches or a walker; however, the value of a walking aid, such as a crutch or cane, is only realized when the aid is properly used.

Contrary to common belief, the crutch or cane should be used in the opposite hand from the side of the injury. The device should be used when stepping with the injured extremity, so that the gait mechanics are as follows: injured leg and opposite hand are extended outward, weight is placed on the cane during the weightbearing phase of gait, and a step is taken. When the device is used in this manner, the force across the injured femoral neck decreases.

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Surgical Therapy

If left untreated, a breach of the tension side of the cortical bone makes these fractures potentially unstable. A significant (10-15%) risk of displacement exists in transverse-type fractures, making prompt internal fixation the standard of care for these injuries.

The preferred method of fixation is with multiple percutaneous screws; however, a dynamic hip screw (DHS) or variable-angle hip screw is also appropriate fixation for these injuries. If the fracture is displaced at the time of surgery, a gentle femoral head reduction maneuver should be attempted prior to internal fixation. As a rule, traction should be avoided because it has the potential to increase the displacement of bony fragments.

In elderly patients (>75 years) or patients with insufficiency-type fractures, bipolar hemiarthroplasty is a more desirable method of fixation. With this approach, patients may bear weight immediately without fear of refracture or displacement of fracture fragments. In individuals whose metabolic stature would lead to questionable healing of the fracture, hemiarthroplasty is usually the operation of choice.

Operative details

Preoperative planning involves determination of the neck-shaft angle of the uninjured side so that an appropriately angled DHS plate may be selected. Variable-angle hip screws allow the surgeon intraoperative adjustment of the neck-shaft angle so that the appropriate angle can be selected ("dialed in") even after surgical insertion of the hardware.

If 7.3-mm cannulated screws are used for nondisplaced or minimally displaced fractures, evaluation of the preoperative radiographs—with close attention paid to the alignment of the femoral neck trabeculae across the fracture—ensures proper alignment of the neck with its base. The decision whether to repair or replace the proximal femur is guided by several factors, including, but not limited to, the following:

  • Displacement of the fracture
  • Age and preoperative functionality of the patient
  • Ability to comply with postoperative weightbearing status
  • Age of the fracture
  • Life expectancy of the patient

In the insertion of either screws or a DHS plate, appropriate positioning on a fracture table is paramount. The affected extremity may be placed in a well-padded boot, with care taken not to apply traction to the extremity and thus displace a nondisplaced stress fracture. A radiolucent perineal post is used to facilitate appropriate intraoperative C-arm imaging. The uninjured extremity should be positioned in a well-padded leg holder flexed to 90° at the hip and knee to allow the C-arm to obtain both AP and lateral projections of the femoral neck.

Appropriate radiographic views are essential for proper placement of both screws and DHS implants.

If hemiarthroplasty is elected, then the lateral decubitus position using a hip positioner is preferred by the authors, and a direct lateral approach to the proximal femur is followed, with care taken to preserve the posterior capsule.

The authors' preferred method of fixation for nondisplaced fractures in healthy individuals with good bone stock is percutaneous pinning in situ with 7.3-mm cannulated screws. This represents both the least invasive and the least morbid approach to femoral neck fixation and is most appropriate if the stress fracture remains nondisplaced. Cannulated screws may be inserted percutaneously, minimizing soft-tissue trauma and perioperative blood loss and decreasing the hospital stay for the patient.

In patients in whom the bone stock is questionable, Bonnaire et al demonstrated that DHS stabilization may provide more robust fixation than stabilization with screws. [35] Using a DHS plate allows secondary impaction of the fracture and, if properly placed in a center-center position with a tip apex distance of less than 25 mm, has been shown to reduce the chances of fracture displacement and additional surgical procedures.

The biggest risk with DHS placement is improper position of the hip screw in a superior eccentric position, which increases the likelihood of screw cutout in the osteoporotic heads. [36]

Screws should be placed in a triangular pattern in the femoral neck, with screw shafts abutting cortical bone superiorly in an attempt to prevent varus displacement of the fracture. The three screws should run parallel to one another, and their threads should completely engage the femoral head. Additionally, care must be taken to ensure that the threads of all three screws are not left crossing the fracture line, making compression of fracture fragments impossible.

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Postoperative Care

Patients undergoing internal fixation of a femoral neck stress fracture should follow a rigorous postoperative course. This consists, at first, of the patient getting out of bed to a chair three times per day, starting on the day immediately after surgery. On postoperative days 2 and 3, the patient usually begins with a touchdown physical therapy weightbearing program. The patient is instructed in the use of walking aids, such as crutches or a walker, and continues using such devices for approximately 8-12 weeks.

Ultimately, the patient may return to physical activity, initially on a decreased scale, and the authors recommend that these activities be limited to low-impact ones, such as swimming and road cycling.

If hemiarthroplasty is undertaken, patients may bear weight with the use of assistive devices once this can be tolerated. Hip precautions are advised for at least 6 months postoperatively, and yearly radiographic and clinical evaluation is warranted to ensure proper position of the prosthesis.

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Complications

Although femoral neck stress fractures are not particularly serious in themselves, delayed diagnosis of transverse-type injuries is associated with significant potential for morbidity. Complications include the following:

  • Delayed union
  • Nonunion
  • Malunion
  • Osteonecrosis or AVN 

In the young and active individuals who are at risk for this type of fracture, a missed or delayed diagnosis that results in displacement can lead to an operation with an increased risk of osteonecrosis and the need for secondary reconstructive surgery. Data on missed stress fractures progressing to displaced fractures are scant, but the rate of AVN of the femoral head following displaced femoral neck fracture is 30-35%.

Nonunion of the fracture site occurs 4-33% of the time after internal fixation. However, several studies suggest that the incidence of nonunion in a stably fixed fracture is largely determined by an individual's age and the degree of fracture displacement. The Radiographic Union Score for Hip (RUSH) has been described as a means of identifying femoral neck fracture nonunion. [37]

Should a nonunion result, patients usually experience severe anterior thigh or groin pain and exhibit a classic Trendelenburg gait. The treatment for this complication is almost always reconstructive surgery.

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Long-Term Monitoring

After surgical fixation of a transverse femoral neck stress fracture, radiographs should be obtained periodically to evaluate for healing. After complete resolution of the stress fracture radiographically, the patient may gradually resume his or her preinjury training regimen.

Patients who have undergone fixation of femoral neck stress fractures should be monitored via doctor's office visits over a period of several years. Such monitoring should include periodic radiographs because whereas operative treatment lessens the risk of AVN, sequelae can nonetheless occur up to several years after the operation.

No data support the assertion that prior nondisplaced femoral neck stress fracture is a risk factor for repeat stress fracture.

If a hemiarthroplasty was performed, patients should observe standard hip precautions for the first 6 months postoperatively. A regimen of postoperative physical therapy for assistance with ambulation is customary for the first 4-6 weeks after surgery. Weightbearing is as tolerated on the operative extremity unless a periprosthetic fracture is present; in the latter case, the operating surgeon should assess the stability of the implant and fixation achieved intraoperatively.

Radiographs are taken yearly to assess the position of the prosthesis and to check for evidence of loosening, infection, or both.

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