Osteonecrosis of the Femoral Head/Avascular Necrosis of the Femoral Head/Femoral Head Necrosis
What is osteonecrosis of the femoral head?
Osteonecrosis of the femoral head is a serious disease of the hip that results from an interruption in the blood supply to the femoral head. The disruption in the blood supply leads to the localized death (necrosis) of bone cells in the subchondral femoral head. Ultimately, the condition leads to a collapse of the necrotic segment of the femoral head.
Osteonecrosis of the femoral head in adults can be referred to as a lifestyle disease. As in the case of myocardial infarction (heart attack), some of the main risk factors include smoking, elevated blood fat levels and excessive alcohol consumption. While the exact prevalence of the disease is unknown, estimates indicate that several thousand new cases are diagnosed in Germany every year!
Most of these patients are between 35 and 45-years-old. The incidence of the disease is higher in men than women. The ultimate destruction of the subchondral femoral head leads to an enormous reduction in the quality of the lives of those affected. In 30-70% of all cases, the disease develops in both hips.
| What happens to the bone? The flow of blood in the arteries that normally supply the femoral head is disrupted. The disruption in the blood flow leads to bone cell necrosis. The normal flow of blood to the bones of the hip supplies them with oxygen, minerals and other nourishing substances. The consequences of disruption in this supply of blood are profound. The central task of the bone cells is to ensure the continuous build up and reduction of bone mass so as to enable the bone to respond to continuously changing compressive loads. Necrotic hip bone tissue is no longer capable of sustaining this natural process. The trabeculae inside the bone, which are important for ensuring the stability and the shape of the femoral head, are no longer renewed. Lacking sufficient stability, the portions of the necrotic bone collapse. This creates a hole in the subchondral bone of the hip, which can lead to serious damage to the cartilage in the hip joint above the hole. This damage sets the stage for hip osteoarthritis. The result is serious and irreversible damage to the bone and the joint. The problem with osteonecrosis of the femoral head is its proximity to the joint and the damage that it can then do to the joint. Bone infarcts that occur inside the bone and at a good distance from joints - and which sometimes turn up by chance on x-rays - are usually of little significance. |
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| Start film about femoral head necrosis. |
Does age play a role?
A similar condition in children, known as Perthes disease, is generally less threatening because the bones of children continue to grow and are otherwise outfitted with a remarkable capacity to repair themselves. The chances of spontaneous healing are accordingly much higher in children. Adults suffering from osteonecrosis of the femoral no longer have this capacity. It is very unlikely that conservative treatment will lead to a significant repair of the necrotic bone.
What are the causes of osteonecrosis of the femoral head?
The most common causes of femoral head necrosis in adults include:
- Traumatic injuries involving damage to the blood vessels that supply the femoral head (e.g. fractures of the femoral neck)
- Excessive alcohol consumption
- Radiation
- Excessive corticoid steroid use
- Cytostatic agents
- Decompression sickness (e.g. affecting divers and miners)
- Metabolic bone diseases that disrupt blood flow to the femoral head (elevated bile acids, diabetes-induced elevated blood sugar levels, dyslipidosis)
- Kidney disease
- Coagulopathy (blood clotting disorder)
- Blood cell tumors
Despite the availability of a wide array of modern diagnostic methods and extensive research, not all of the causes of osteonecrosis of the femoral head are known. We often treat patients at our clinic who show all of the signs of osteonecrosis of the femoral head while showing none of the above-mentioned conditions.
What are the early symptoms?
The condition is usually asymptomatic during its early stages. This is commonly followed by a stage of non-specific signs and symptoms. Ultimately, patients present with a limited range of motion and intense hip pain that is made worse by weight bearing and forced internal rotation.
Many patients are asymptomatic until the collapse of the necrotic femoral head. This is why the condition is often not diagnosed and treated on time.
How is osteonecrosis of the femoral head diagnosed?
We confer with our patients about their symptoms and the various risk factors associated with the disease. This careful history of the hip pain is followed up by a meticulous physical examination of the hip joint.
Thanks to our experience, we are usually able to properly assess the symptoms and quickly introduce the necessary treatment.
The examination criteria include:
The hip joint's range of motion
- The way the hip joint's movement feels
- Points of pain in the hip joint
- Points at which hip pain can be elicited
- Strength and mass of the buttock and thigh muscles surrounding the hip
- Patient gait
- We also have access to various diagnostic imaging procedures. X-rays and magnetic resonance imaging (MRI) allow us to confirm a hip diagnosis.
- X-ray Diagnostics
Digital x-rays permit a low-radiation examination of the hip joint. This diagnostic procedure is not suitable for arriving at a diagnosis of a very early stage of osteonecrosis of the femoral head. An x-ray will only show changes in the bone structure. The disintegration of the trabeculae does not occur until weeks after the actual necrosis, i.e. the death of the bone cells as a result of the disrupted blood supply. This is why the signs of osteonecrosis of the femoral head do not appear on an x-ray during the disease's initial phase.
MRI Diagnostics
The use of multiple resonance imaging (MRI) does permit an early diagnosis of osteonecrosis of the femoral head. It is also the only diagnostic method that enables the physician to detect the disease at a stage that is early enough to allow for effective treatment, for instance, involving the complete conservation of the bone or at least the preservation of an intact hip joint.
Like x-rays, computed tomography offers no more than a visualization of the changes to the bone, and is therefore helpful only when it comes to examining later stages of the disease.
All three of these imaging procedures are helpful when it comes to assessing the nature and extent of the condition and drafting a needs-based treatment plan.
What are the various stages of osteonecrosis of the femoral head?
- ARCO 0: all imaging procedures yield negative results.
- ARCO I: MRI and bone scintigraphy show necrosis.
- ARCO II: x-rays and CT show slight decalcification and MRI shows typical necrotic zone.
- ARCO III: x-rays and CT show a subchondral fracture line (femoral head deformation begins).
- ARCO IV: signs of hip joint wear (secondary osteoarthritis)
What is used as a basis for selecting a course of treatment?
An evaluation of the ARCO stage is indispensable for determining the proper treatment.
The age of the patient and the extent and precise location of the disease are also critical factors. In contrast to children suffering from Perthes disease, adult patients have no chances of spontaneous healing. The state of the hip joint, the general health of the patient, and the presence of any other diseases will also be considered when selecting a course of treatment.
The chances of significant recovery are higher in patients showing early stages of the disease and lower in patients showing advanced stages.
What forms of treatment are available?
- Conservative Treatment
- Physical therapy to reduce mechanical stress, resting the hip joint (special braces), refraining from playing sports
- Hyperbaric oxygen therapy (during the early stages of the disease)
- Hip Surgery
- Pridie drilling
- Autologous cartilage-bone transplantation
- Osteotomy (e.g. varisation osteotomy for Perthes disease)
- Hip replacement
What diseases are to be distinguished from osteonecrosis of the femoral head?
- Inflammation-related forms of femoral head necrosis (septic femoral head necrosis)
- Osteomyelitis
- Malignant femoral head tumors or neoplasia (rare malignant tumors of the femoral head include clear cell carcinoma)
- Benign femoral head tumors
- Osteoarthritis-induced bone cyst formation
Summary
Osteonecrosis of the femoral head is a serious bone disease that affects the hip joint. The disease leads to the localized destruction of the bone in the subchondral femoral head. In adults, it is sometimes described as a lifestyle disease. As in the case of myocardial infarction (heart attack) the risk factors for osteonecrosis of the femoral head include smoking, elevated blood fat levels and excessive alcohol consumption. While the exact prevalence of the disease is unknown, estimates indicate that several thousand new cases are diagnosed in Germany every year. There are various known causes of osteonecrosis of the femoral head. The condition is primarily observed in individuals between 35 and 45-years-old. The incidence of the disease is higher in men than women. The destruction of the femoral head leads to an enormous reduction in the quality of the lives of those affected. In 30-70% of all cases, the disease develops in both hips.
