Femoral Neck Stress and Insufficiency Fractures


Background

Femoral neck stress fractures are a common cause of hip pain in select populations. Chronic, repetitive activity that is common to runners and military recruits predisposes these populations to femoral neck stress fractures. These injuries must be differentiated from insufficiency fractures, which, though similar in appearance and presentation, result from an entirely different pathophysiology and occur in a different population.

The femoral neck area is subjected to large compressive and shear forces associated with ambulation. Even in the most sedentary individual, the daily cyclic loading of the hip and femoral neck produces high stresses on the bony trabeculae in this anatomic region. In long-distance runners and other high-performance athletes, the forces across the femoral neck are multiplied exponentially because the athletes' training regimens place tremendous physical burdens on this relatively small bridge of bone, which connects the femoral head to the diaphysis.

The greatest physical symptom that stress fractures manifest is pain in the hip, groin, or anterior thigh. Such pain can severely limit an athlete's ability to train, compete, and, ultimately, ambulate if the problem progresses undiagnosed. The ultimate result of an untreated stress fracture can be a complete fracture (possibly displaced) of the femoral neck. Even isolated, this injury could be devastating to a performance athlete. The sequelae of this fracture include avascular necrosis (AVN) of the femoral head and fracture nonunion, both of which can adversely impact athletic careers.

The pain associated with femoral neck stress fractures can be both irritating and disabling to these high-performance individuals. Because the onset of this pathologic entity is insidious and because the results of conventional radiography are frequently equivocal, the diagnosis of femoral neck stress fractures can be missed. Whereas the treatment of stress fractures of the femoral neck is often straightforward, undetected stress fractures can lead to serious complications.

The first description of femoral neck stress fractures in the literature was published in 1936 by Asal in Archiv für Klinische Chirurgie. Since then, numerous articles have recognized these fractures as difficult entities to treat. In 1963, Ernst recorded what was at the time the largest series of femoral neck fractures and described the resulting disability in military servicemen. [1Although the geneses of acutely traumatic fractures are different from those of stress fractures, the treatments are similar

Since the first descriptions of the vascular anatomy of the femoral neck, orthopedists have recognized the importance of prompt reduction of femoral neck fractures in preventing AVN of the femoral head. Closed reduction and impaction of the fracture parts, followed by immobilization in a spica cast application, with the injured extremity in internal rotation, were adopted by numerous orthopedists of the time.

It was not until 1931, however, that the first methods of internal fixation were publicly described by Smith-Petersen. [2The medical community was hesitant to accept internal fixation, but this method of treatment nonetheless came into wide use and remained so until the 1970s.

Seven years after Smith-Petersen introduced internal fixation, Moore described a multiple-pin fixation technique, which was followed shortly thereafter by the Thompson femoral endoprosthesis. The varied methods of treatment sparked great debate over whether replacing the entire femoral head or simply fixing the neck fracture was more beneficial.

The idea that impacting fracture fragments was the key aspect in healing led to the development of the Pugh nail and the Richards screw, in the 1950s and 1960s. Both of these modalities were designed around a sliding fixation process whereby fracture fragments can compress against each other.

Finally, Judet described another method of treatment that has not been practiced widely but still deserves mention: the quadratus femoris muscle pedicle graft. With this technique, a vascularized bone graft is placed across the posterior femoral neck and into the femoral head to prevent the complication of AVN.

Anatomy

Vascular

The femoral head derives its blood supply from three terminal arterial branches. The lateral epiphyseal artery (an ascending branch off of the medical femoral circumflex artery of the profunda femoris) is the predominant source of blood flow, and its distribution to the head is largely skewed toward the subchondral bone of the femoral articular cartilage.

Two accessory arteries supply the remaining 10% of femoral head circulation: the inferior metaphyseal artery (the ascending branch of the lateral femoral circumflex artery) and the medial epiphyseal artery of the ligamentum teres. The latter vessel originates from the obturator artery.

The vascular anatomy of the femoral neck is especially important because fractures of this region can have devastating effects on the already tenuous blood supply to this area. The severity of the vascular disruption generally correlates with the degree of displacement of the fracture.

Bone

By midadolescence, the femoral epiphysis is usually closed, providing a reasonable anatomic picture of the femoral head and neck. The neck-shaft angle, which is approximately 130°, is relatively constant between the sexes. Femoral anteversion is estimated at 10.4° and remains unchanged even after skeletal maturity is reached.

A fairly large synovial membrane encloses the femoral head and a good portion of the anterior femoral neck. The greater trochanter, a large, posteriorly located, bony prominence, serves as the major attachment for the external rotators; it also provides a definitive surgical landmark for the insertion of numerous femoral internal-fixation devices.

Pathophysiology

A closer look at the genesis of a stress fracture in the femoral neck reveals that the damage manifested on the physical level derives not from a traumatic event per se but, rather, from a metabolic derangement.

Bone initially responds to increased mechanical loading by increasing resorption. Resorption is normally counterbalanced by an equal but opposite, osteoblast-mediated metabolic repair. Under situations of extraordinarily high levels of training, such as those faced by military personnel and elite athletes, bone resorption begins to exceed the bone's capacity to remodel.

Additionally, pharmacologic (glucocorticoids), nutritional (vitamin D and calcium deficiency), and other (postmenopausal, hyperparathyroid) states can adversely affect osteoblasts' ability to keep pace with osteoclastic resorption. If this metabolic imbalance persists, microfractures develop that eventually weaken bone to the point of a complete fracture.

Etiology

Femoral neck stress fractures in young, otherwise healthy individuals are related to the inability of bony trabeculae weakened by osteoporosis to withstand physical stresses. Unusually high physical demands on normal bone over the long term can lead to mechanical failure of the bone trabeculae. [3The phenomenon is seen with exercise beyond the point of muscle fatigue, [4alterations of ground reactive forces that yield abnormal stress patterns in bone, and increased muscular contractions.

In contrast, insufficiency fractures of the femoral neck are the result of normal stresses of everyday activity placed on structurally compromised bone. Thus, insufficiency fractures occur in individuals who have concomitant metabolic derangements, such as hyperparathyroidism and renal failure, or menopause. [5]

At least one example of a crossover group exists: amenorrheic female athletes. Because of their lack of body fat, female distance runners often temporarily halt their menstrual cycle. As a result, they become hypoestrogenic and, therefore, physiologically similar to postmenopausal females.

Estrogen is an essential factor in the development and maintenance of bone strength; in its absence, bones become brittle and osteopenic. This places these female athletes in a sort of double jeopardy, producing characteristics that contribute to stress fractures and causing a background hypoestrogenic state that predisposes these women to insufficiency fractures.

Epidemiology

Femoral neck stress fractures occur most commonly in two subsets of the population. The first subset comprises elite distance runners, [678910military recruits, [111213and dancers. [14The true prevalence of fractures in this group is difficult to pinpoint because such patients with hip pain and femoral neck stress fractures who never present to a physician and whose fractures go on to heal spontaneously are never identified.

Data from several military hip fracture studies by Stoneham and Morgan in Britain and Volpin et al in Israel place the prevalence at 0.2-4.7% in patients without a history of a single traumatic episode. [1516The prevalence of stress fractures in the general population may be surmised to be far less than that demonstrated in these two groups.

The second subset comprises hypoestrogenic (postmenopausal) women and individuals with pathologic entities resulting in osteopenia (eg, osteoporosisPaget diseasehyperparathyroidism). Fractures in this group are termed insufficiency fractures, because bone quality is insufficient to support the diurnal physiologic demands placed on it.

Femoral neck stress fractures in children are exceedingly rare [17and should be far down on the list of differential diagnoses, behind such conditions as slipped capital femoral epiphysisLegg-Calve-Perthes disease, infection, and transient synovitis. To date, there have been very few reports of this entity in the English literature. [1819Whereas Blickenstaff et al claimed in a 1966 article to have found only compression-side stress fractures of the femoral neck in children, Lehman et al reported on a tension-side stress fracture in a child of 14 years. [2021]

Prognosis

The prognosis for femoral neck stress fractures depends largely on the classification of the fracture. [22 Patients with compression-type injuries historically fare very well, with the patient recovering full preinjury function after diligent adherence to a physician-prescribed plan of limited weightbearing and walking with an aid.

Patients with transverse-type fractures, if they are identified early and if the only radiographic abnormality is sclerotic changes, tend to recover well after internal fixation. Potential lasting effects of surgical management include hip pain and nonunion or malunion of the fracture. The worst prognosis exists for transverse fractures that are inherently unstable because of mechanical reasons and that can progress to complete displaced fractures. [23The rate of nonunion and AVN in these cases is as high as 35%, according to some authors.



History and Physical Examination

Although femoral neck stress fractures are relatively uncommon in the general population, they must be part of any thorough physician's differential diagnosis for an athlete presenting with anterior hip or groin pain.

A history of insidious hip or groin pain that is directly related to an increase in the level or duration of athletic activity and that is relieved by rest is typical. Early diagnosis is often difficult because of the lack of an identifiable traumatic event, which tends to dissuade primary care physicians from obtaining radiographs. Even the astute physician ordering hip films upon first presentation may overlook this diagnosis because fracture callus is not evident early in the process.

A bone scan may be helpful in cases where suspicion is high but radiographic findings are equivocal. The higher degree of sensitivity of bone scanning is useful in detecting stress fractures and other forms of periosteal injury without complete fracture.

In patients presenting with hip pain and negative findings during the initial workup, obtaining plain radiographs of the ipsilateral knee also should be considered. Referred pain along the course of the anterior branch of the obturator nerve may manifest as ipsilateral hip pain and should be in the clinician's differential diagnosis, especially in younger patients.

Magnetic resonance imaging (MRI), though costly, offers increased specificity in the detection of stress fractures. The importance of early detection cannot be underestimated, because the interval between the onset of symptoms and the diagnosis often dictates whether an injury can be treated with rest and protected weightbearing or if surgical intervention is required to reduce a displaced neck fracture.

Case Study

A 29-year-old male had spent 6 months training for a marathon by running approximately 45 miles per week. He mentioned to one of his fellow runners that he had recently noticed a mild ache in his right groin. On the advice of his friend, the man took a few days off from running, and the pain resolved without further treatment.

While running in the marathon the following week, the patient developed the same ache, which not only persisted but also increased so greatly that he had to cease running at mile 14. He was driven home by a friend; upon arrival at his house, he was unable to bear weight on the right leg. At his friend's insistence, the patient traveled to an emergency department (ED), where he was seen by a physician. No films were obtained at that time, because the patient had full, painless range of motion (ROM); he was instructed to take ibuprofen and was sent home without a walking aid.

The following day, the patient went to his primary care physician and obtained a referral to a physiotherapist. Following 3 weeks of therapy, he was still unable to comfortably bear weight. He returned to the ED one night the following week because his pain had persisted. The patient was told to ice the groin and was given a prescription for a cyclooxygenase-2 (COX-2) inhibitor, but he did not receive a radiograph.

The patient continued his physiotherapy for an additional 3 weeks without improvement of his symptoms, at which time his primary care physician referred him to a local orthopedic surgeon.

Upon physical examination, the patient had approximately 1.5 cm of shortening on the affected side, with severely limited ROM at the hip. A radiograph confirmed a basicervical fracture of the femoral neck, with a neck-shaft angle of 90°. MRI suggested the development of a fibrous nonunion.

The patient was taken to the operating room for open reduction and internal fixation (ORIF). A subtrochanteric osteotomy for correction of the varus deformity of the femoral neck also was contemplated, but gentle traction restored enough neck-shaft angle to permit placement of a dynamic hip screw (DHS).

At 6 months postoperatively, the fracture was thought to be sufficiently healed to allow unprotected weightbearing. At 8 months postoperatively, the patient had resumed low-impact activities, such as cycling and swimming. After more than 3 years, he had resumed recreational running without difficulty.

This case is classic in its presentation. A young male distance athlete with insidious onset of hip pain, which was likely a stress fracture of the femoral neck, went undiagnosed despite several visits to the doctor. Only after obtaining appropriate imaging studies was the truly serious nature of the patient's symptoms revealed.



Laboratory Studies

No particular laboratory studies aid in the diagnosis of this disorder; however, a prudent part of the preoperative workup is the ordering of standard laboratory tests (eg, blood chemistries, hemoglobin and hematocrit values, and coagulation profile). When an insufficiency fracture is suspected, the medical workup should include a search for metabolic abnormalities, including abnormal calcium, phosphate, and alkaline phosphatase values.

If septic arthritis of the hip is suspected, assessment of the C-reactive protein (CRP) level, the erythrocyte sedimentation rate (ESR), and the white blood cell (WBC) count with differential is indicated to help rule out an infectious process.

Plain Radiography

Plain radiography remains the initial imaging examination in the evaluation of suspected hip disease. A standard hip radiographic series includes an anteroposterior (AP) view of the pelvis and cone-down AP and frog-leg lateral views of the affected hip.

The AP view of the pelvis allows evaluation of the contralateral hip for concomitant disease and can be used to exclude osseous or articular abnormalities of the pelvis (eg, sacroiliitis, sacral stress fractures, pubic ring fractures) that could present clinically as hip pain. The AP views of the pelvis and hip are obtained with the feet internally rotated.

The frog-leg lateral view of a hip is obtained with the radiographic beam oriented in the AP direction and with the hip abducted. A groin lateral view of the hip can be used instead in cases of an acute femoral neck fracture or displaced fracture, because the affected hip remains in a neutral position. In this examination, the opposite leg is abducted and elevated and the radiographic beam is oriented parallel to the table, with 20° cephalad angulation.

In the case of a compression-type fracture, the inferior aspect of the femoral neck demonstrates cortical thickening with a hazy, radiolucent center. This radiographic picture may be easily confused with that of an osteoid osteoma if an adequate history is not obtained from the patient.

Transverse-type fractures appear much differently on radiography, the first sign being a faint line of sclerosis across the femoral neck. (See the images below.) If left untreated, these transverse fractures may easily progress to complete neck fractures, with significant displacement and varus angulation.

Anteroposterior and lateral images of a 54-year-olAnteroposterior and lateral images of a 54-year-old woman with a 2-month history of right groin pain with ambulation. Note sclerosis of the right femoral neck running perpendicular to trabeculae.
Anteroposterior and lateral images of a 54-year-olAnteroposterior and lateral images of a 54-year-old woman with a 2-month history of right groin pain with ambulation. Note sclerosis of the right femoral neck running perpendicular to trabeculae.
Anteroposterior and lateral images of a 54-year-olAnteroposterior and lateral images of a 54-year-old woman with a 2-month history of right groin pain with ambulation. Note sclerosis of the right femoral neck running perpendicular to trabeculae.
Anteroposterior and lateral images of a 54-year-olAnteroposterior and lateral images of a 54-year-old woman with a 2-month history of right groin pain with ambulation. Note sclerosis of the right femoral neck running perpendicular to trabeculae.

Bone Scanning

Because of its sensitivity in detecting periosteal injury, bone scanning has been very helpful in the absence of conventional radiographic findings. [24 In the presence of stress fractures, bone scanning demonstrates focal increased uptake of the radiotracer, at the fracture site. This represents an area of increased bone turnover. One drawback to this modality, however, is that findings on scintigraphy are often negative during the first 24 hours after stress fracture.

The positive predictive value of radionuclide imaging in diagnosing femoral neck stress pathology approaches 68%.

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is comparable to radiography in sensitivity and has the added advantage of being more specific for stress fractures; accordingly, it has become the modality of choice for detecting stress pathology. [25262728 In several studies, both the sensitivity and the specificity of MRI for femoral neck stress fractures were 100%. With this increased specificity, however, comes a higher price tag.

Besides being less invasive than bone scanning (because it does not require the injection of a radiotracer), MRI provides much more information about the surrounding soft tissues. MRI has been shown to be effective in differentiating stress fracture from malignancy or infection.

Diagnostic MRI of a femoral neck stress fracture yields decreased signal intensity on T1-weighted images and increased signal intensity on T2, as well as short tau inversion recovery (STIR) images with or without a low signal fracture line.

In a retrospective review of 156 consecutive fatigure-type femoral neck stress injuries in 127 US Army soldiers over a 24-month period, Rohena-Quinquilla et al proposed an MRI classification system for these injuries that is based on patient management and return-to-duty time. [29]

Computed Tomography

Computed tomography (CT) is typically not regarded as a first- or second-line imaging modality for these fractures, but it may be considered when other modalities yield equivocal results. [



Approach Considerations

Indications

In 1965, Devas instituted a classification scheme for fatigue fractures, based on prognosis and radiographic appearance. [31His 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.

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.

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. [32Using 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. [33]

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.

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.

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. [34]

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.

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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