CASE On physical examination, Mr. Q had right hip extension to 0°, flexion to 110°, external rotation to 50°, and internal rotation to neutral; he also had positive impingement and subspine impingement tests, a painful arc of motion from 12 to 4 o’clock, tenderness over the hip adductor, and pain with resisted hip adduction. He did not walk with a limp.
Diagnostic studies included plain radiographs, which demonstrated that the joint space was well preserved. We identified subtle anatomical abnormalities on the femoral head-neck junction, known as a cam deformity. Magnetic resonance imaging (MRI) revealed an anterior superior labral tear with cartilage delamination.
Stress fractures affect runners, military recruits
In addition to long-distance runners who have recently increased the frequency, duration, or intensity of training,5,6 military recruits have a higher incidence of stress fractures due to the rapid onset of intensive training. Stress fractures can also occur in patients who do not have a history of intense activity but have metabolically weakened bone, in some cases as a result of an eating disorder.7
Patients with femoral neck stress fractures typically present with activity-related anterior groin pain that is relieved by rest; initially, they may be only mildly affected, but the condition worsens in those who continue to “work through the pain.” By the time such individuals seek treatment, they almost always have pain with weight bearing and an antalgic gait.
Symptoms consistent with a femoral neck stress fracture can be further evaluated with plain radiographs. However, x-rays are often negative for up to 4 weeks after the onset of pain.8 In cases in which radiographs are negative but the physical exam is suggestive of a stress fracture, MRI—which can detect an abnormality within a day or 2 of injury8,9—should be used to confirm the diagnosis (FIGURE 1).
FIGURE 1
MRI reveals a femoral neck stress fracture
Treatment. A complete femoral neck fracture portends impending displacement and requires emergent evaluation by an orthopedist, and superior neck changes, also known as tension-sided stress fractures, require urgent treatment with percutaneous screw fixation.9 However, compression-sided, or inferior, stress fractures can be treated with restricted weight bearing and activity modification. Gradual resumption of activity is allowed only after the patient has been asymptomatic for 6 weeks; recurrent pain indicates residual stress reaction, and signals that activities should be abated.
Osteonecrosis has many causes
Necrosis of the femoral head is a debilitating and progressive condition primarily affecting patients between the ages of 20 and 50 years.10 It has multiple (and diverse) causes, including trauma, steroids, alcohol, smoking, lupus, sickle cell anemia, and coagulopathies, as well as scuba diving. But about 20% of cases have no apparent cause.11,12
Patients with osteonecrosis of the hip typically present with groin pain, often described as a deep, intermittent ache that interferes with activities of daily living. Exam findings depend on the stage of presentation. Early on, pain will occur only with extreme ROM; in advanced cases, ROM is restricted and pain occurs even with limited motion.
Femoral head collapse due to loss of the structural integrity of the subchondral bone—which occurs in 80% of cases12—is thought to be caused by decreased blood flow. Plain radiography can confirm a diagnosis of osteonecrosis in patients with advanced disease, but MRI is useful for evaluating patients with earlier clinical presentations.
Treatment of osteonecrosis is dictated by the stage of the disease, but remains controversial because no intervention has been shown to prevent progression in all cases.12 All patients should be referred to a specialist. Those without collapse or cartilage damage can be treated surgically with core decompression, possibly with additional vascularized bone grafting,13,14 while those with more advanced disease typically require a total hip replacement at a relatively young age. Results for total hip replacement in patients with osteonecrosis are thought to be inferior to hip replacement in patients with osteoarthritis, although comparison is difficult because of the differences in age and activity levels in these 2 groups.15,16
Femoral acetabular impingement can occur on the cam or pincer side
FAI pathology can exist on either the femoral (cam) or acetabular (pincer) side,17 or both.18 In pure cam impingement, the anterior femoral neck loses its normal concave anatomy and develops a “bump,” which impinges on the anterosuperior labrum during hip flexion, causing labral tears and delamination of the adjacent cartilage.