Death of femoral head bone cells is known as femoral head necrosis. The term necrosis means cell death. Most affected patients are under 40 years of age. This fact is very important as it is an active age and patients often stop playing sports, have difficulty in simple activities such as climbing stairs or even quit their professional activity. Treatment of this disease can significantly improve the lives of these patients.
Femoral head necrosis is also known by other names, such as osteonecrosis, aseptic necrosis or avascular femoral head necrosis. It weakens the femoral head, which suffers microfractures and usually deforms progressively. Most cases of extensive femoral head necrosis result in joint destruction within three to five years. It is eight times more common in men than women and 30 to 50% of patients have bilateral disease (on both sides). Approximately 10% of hip arthroplasty (hip prosthesis) is performed as a consequence of this disease.
Although better known in the femoral head, other bones may also be affected by bone necrosis, including the distal femur (knee), proximal humerus (shoulder), jaw, vertebra, and foot and hand bones.
The list of possible causes of femoral head necrosis is extensive, but in about 80% of patients the cause is alcohol intake or corticosteroid medications (corticosteroids or glucocorticoids).
The mechanism by which these causes lead to bone necrosis is variable, including direct damage to vessels, elevation of intraosseous pressure, and direct cell damage. The result is disruption of blood supply and death of femoral head bone cells. The weakened femoral head eventually collapses and deforms in most patients with necrosis in more than 50% of the femoral head.
The following are the most common causes of femoral head necrosis:
Use of corticosteroids (corticosteroids or glucocorticoids)
Corticoid medications are used to treat many diseases, especially rheumatic, skin and tumor chemotherapies. Some examples of this medication include: prednisone, prednisolone, dexamethasone, hydrocortisone, cortisone, among others. Oral and injectable corticosteroids have been associated with femoral head necrosis. Despite being one of the most common causes of femoral head necrosis, it still has a low incidence of this complication considering the large number of patients using corticosteroids. These medications cause fat microemboli that clog the bone arteries. In addition, they cause venous flow obstruction, increasing intraosseous pressure. Patients on chronic corticoid use are at higher risk. Nevertheless, the use of high doses for short periods may also cause femoral head necrosis.
Alcohol intake can cause femoral head necrosis by mechanisms similar to corticosteroid medications. The risk is dose dependent, and it is estimated that ingesting 400 to 1000 ml of alcohol per week increases the risk by about 10 times, while intakes greater than 1000 ml per week increase the risk by about 18 times.
Millimeter vessels (retinacular vessels) leave the trochanteric region and pass on the surface of the femoral neck to nourish the femoral head. These vessels can be injured in femoral neck fractures and hip dislocations (dislocation), with consequent bone death (necrosis). Femoral head osteonecrosis may take up to 5 years after fracture to cause symptoms.
We cited above the three most common causes of femoral head necrosis. However, there are many other possible causes, including the following:
- Kidney, bone marrow or other organ transplantation;
- HIV infection;
- Systemic lupus erythematosus;
- Sickle cell anemia;
- Gaucher’s disease.
Pain is the most common symptom of femoral head necrosis. The pain may be located in the “groin”, gluteal region, thigh or knee. Most patients experience worsening pain with activity and movement, but may also experience pain at rest or waking up with pain. Lameness (limping) happens in more advanced cases, with patients often needing crutches. Most patients only seek care when the disease is already at an advanced stage. A high index of suspicion should be had in patients with risk factors such as corticoid use and high alcohol intake.
Imaging tests are important for the diagnosis of necrosis and to assist in the indication of treatment.
Most cases can be diagnosed with hip radiographs (x-ray), these exams will show cysts and more opaque areas on the femoral head. In later stages, deformation of the femoral head is identified, followed by loss of hip cartilage (hip arthrosis as a consequence of femoral head necrosis).
Bone scintigraphy and especially magnetic nuclear resonance may diagnose femoral head necrosis earlier. Thus, these tests are useful in patients whose radiography was not able to give the diagnosis and necrosis is suspected. MRI may also eventually be useful for calculating the extent of femoral head necrosis and guiding treatment. These tests may also help differentiate femoral head necrosis from others such as transient hip osteoporosis and femoral head failure fracture. It is not uncommon for hip imaging to demonstrate femoral head osteonecrosis in patients without symptoms who underwent the study for other reasons.
Laboratory tests may help identify the cause of femoral head necrosis in some patients.
The treatment of femoral head necrosis is determined by jointly analyzing symptoms and physical examination with imaging tests. The presence of pain, age, general health status, associated diseases, lesion size, and location in the femoral head will determine treatment.
In general we can classify the treatment as non-surgical, surgical with hip preservation and surgical with arthroplasty (hip prosthesis). The decision on the best alternative will depend on the analysis of the factors previously mentioned and it may often be necessary to change the treatment modality, for example from non-surgical to surgical treatment.
Non surgical treatment
This treatment alone is indicated in the minority of cases and includes analgesic medications, rest, use of canes or crutches. Some scientific work has shown good results for some patients with osteoporosis medications called bisphosphonates (eg alendronate). However, there is no definitive evidence that these medications alter the evolution of femoral head osteonecrosis.
Surgeries that preserve the natural hip
Surgeries that preserve the natural hip are indicated in the early stages of the disease, usually before the femoral head is deformed or there is already arthrosis (cartilage wear). These surgeries aim to cure femoral head necrosis or to slow the course of the disease. The following procedures are examples of these surgeries:
- Femoral head decompression;
- Bone graft with joint opening;
- Ostecondral graft;
- Vascularized bone graft;
Hip arthroplasty (hip prosthesis)
Hip arthroplasty is an alternative for patients in later stages or those who have not responded to other forms of treatment.
Other forms of treatment
The developments in stem cell research promises other alternatives for treatment of necrosis with the preservation of the femoral head. New medications that help replace necrotic (dead) bone with living bone are also under study.