Hip Osteonecrosis - Causes, Symptoms, Diagnosis, and Treatment

What Is Hip Osteonecrosis?

Hip osteonecrosis, also known as avascular necrosis, is characterized by the gradual process of death of the thigh bone tissue due to a disrupted blood supply to the hip bone and hip joint. The interrupted normal vascular supply to a section of the head of the femur bone can cause the bone to break into tiny pieces, finally leading to its collapse along with hip joint destruction. This is a very gradual process taking approximately months to years to show its adverse effects.

What Are the Causes of Hip Osteonecrosis?

The exact cause of hip osteonecrosis is unknown, but multiple predisposing factors have been identified that can lead to the development of the condition.

• Traumatic Injury- Fractures of the hips, hip joint dislocations, or radiation injury to the bone marrow elements of the bone can result in damage to the extraosseous vascular supply, thereby disrupting the blood supply to the bone.

• Alcohol Overuse- Excessive consumption of alcohol has been attributed as one of the main risk factors in the development of the condition. Fatty acids can be deposited in the blood vessels, thereby elevating the cortisone levels due to alcohol abuse. This results in reduced blood supply to the section of the bone.

• Long-Term Corticosteroid Consumption- High doses of alcohol consumed for a longer period of time can serve as a major risk factor for the condition.

• Certain Medical Diseases- Sickle cell anemia, Caisson’s disease (decompression caused in scuba diving leading to the formation of nitrogen bubbles in the arterioles, thereby occluding them), systemic lupus erythematosus, sarcoidosis, Crohn’s disease, Cushing's disease, leukemias, rheumatoid arthritis, vasculitis, pancreatitis, thrombosis, and Gaucher’s disease are some of the medical conditions that have been found to be associated with the condition.

• Smoking, Pregnancy, and a Few Viral Infections - Have also been found to be associated with hip osteonecrosis in a few cases.

• Genetic Predisposition - It is also seen in some cases.

What Is the Pathogenesis of Hip Osteonecrosis?

• Traumatic injury to the femoral head of the bone causes damage to the femoral artery supplying the femur bone leading to the death of the bone cells that are present in the bony matrix. This further results in the weakening of the bone structure, causing the collapse of the femur bone and polyarthritis of the hip joint.

• The pathogenesis of hip avascular necrosis in cases that occurs from the influence of predisposing factors is the result of intravascular coagulation. The intravascular coagulation causes venous thrombosis, subsequently leading to occluded arterial supply. This, in turn, raises the intraosseous pressure leading to the disrupted blood supply to the head of the femur bone, eventually causing bone cell death and bone collapse with arthritic joint pathologies.

What Is the Epidemiology of Hip Osteonecrosis?

The incidence rate of the disease is estimated to be approximately 20,000 to 30,000 new cases yearly in the United States of America. Males are more frequently involved than females. The disease is more commonly seen in the age group of the 3rd to 5th decades of life. The condition has a tendency to occur bilaterally.

What Are the Symptoms of Hip Osteonecrosis?

• Hip pain is typically the first symptom reported by the patients.

• The pain onset is often insidious.

• Continuous dull, throbbing ache or pain in the groin region is the most common symptom reported.

• This dull aching pain is transferred to the thigh bone and buttocks.

• With the progression of the disease, it becomes tough to stand and apply pressure on the affected side of the hip.

• There is restricted hip movement on the affected side with severe pain in the hips on continuous standing posture or climbing stairs.

• The disease usually takes months to years for its course to progress.

How Is Hip Osteonecrosis Diagnosed?

• Complete Health Checkup: The first and foremost thing to do by a healthcare clinician is to perform a complete health checkup of the patient, including their proper medical history.

• Imaging Procedures: Like x-rays and magnetic resonance imaging should be performed to evaluate the disease.

  • X-Rays- It is recommended to detect any signs of fracture in the bone or arthritic changes in the hip joint.

  • Magnetic Resonance Imaging (MRI)- It is recommended if the radiograph shows negative findings and the condition is still suspected.

How Is Hip Osteonecrosis Classified?

• The avascular osteonecrosis of the hip is classified into four stages based on the Ficat and Arlet classification.

• This staging system makes use of radiographs, MRIs, and clinical signs and symptoms to classify the osteonecrosisofthe femoral head of the hip.

Ficat and Arlet Classification:

• Stage 0

  • Radiographic Findings: Normal.

  • Magnetic Resonance Imaging (MRI): No pathology detected.

  • Clinical Symptoms: Absent.

• Stage I

  • Radiographic Findings: Mild osteopenia is detected or normal x-ray findings.

  • Magnetic Resonance Imaging (MRI): Bone marrow edema may be possibly seen.

  • Clinical Symptoms: Pain possibly present in the groin region.

• Stage II

  • Radiographic Findings: Marked osteopenia with the presence of subchondral cysts and sclerosis with joint space collapse.

  • Magnetic Resonance Imaging (MRI): Marks the geographical area of involvement of the head of femur bone.

  • Clinical Symptoms: Pain in the groin and thigh region with restricted hip movement, stiffness, and pain while climbing stairs or even standing.

• Stage III

  • Radiographic Findings: The crescent sign is observed with the collapse of the joint space, degenerative changes of the hip joint along with loss of morphological anatomy of the femur head.

  • Magnetic Resonance Imaging (MRI): Similar finding to x-ray.

  • Clinical Symptoms: Pain in the groin region that is referred to as knee, limp is seen, and difficulty in performing routine activities like climbing stairs.

• Stage IV

  • Radiographic Findings: An end-stage disease with extensive destruction of the joint followed by complete closure of the joint space. Femoral bone collapse.

  • Magnetic Resonance Imaging (MRI): Similar to the radiographic findings.

  • Clinical Symptoms: Severe pain, joint stiffness, and gait are altered with pain even at rest.

What Is the Treatment of Hip Osteonecrosis?

The management of osteonecrosis of the hip includes both conservative and surgical procedures.

Non-operative Management Includes:

• Ice packs.

• Heat therapy.

• Proper rest is recommended.

• Nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the symptom of pain.

• Bisphosphonate therapy.

• Physiotherapy to increase hip joint mobility and motion.

Surgical Management Includes:

• Core decompression of the femoral bone by drilling small holes (cores) in the lesional bone to improve the vascular supply to the bone. Stem cell injections can also be included in this procedure.

• Bone grafts can be used to accelerate the healing process.

• Hip Joint replacement (in this procedure, the diseased part of the hip joint is removed by the surgeon, and an artificial joint is inserted).

• Hip arthroplasty (total hip replacement).

Conclusion

Hip osteonecrosis has a very high morbidity rate if the condition is left untreated. Therefore, a team of healthcare professionals should work in coordination to treat the patient effectively. The disease should be diagnosed properly by correlating the clinical features with the imaging findings in order to best manage the condition at the earliest. The patient should be educated about the risk factors of the disease to better judge their medical condition and act accordingly.