Makindo Medical Notes

Related Subjects: |Developmental Dislocation (Dysplasia) of the Hip (DDH) |Slipped Upper Femoral Epiphysis (SUFE) |Perthes disease (Osteochondritis of the Hip) |Avascular Necrosis of Femoral head

About

• Avascular necrosis (AVN) of the femoral head is a condition caused by reduced blood supply to the femoral head, leading to the death of bone tissue.
• Also known as osteonecrosis, it can lead to the collapse of the femoral head and subsequent arthritis of the hip joint.
• It is a progressive condition that, without treatment, results in the destruction of the hip joint.

Aetiology

• Traumatic AVN: Fracture or dislocation of the femoral neck, hip dislocation, and joint injuries can interrupt blood flow to the femoral head.
• Non-Traumatic AVN: Common causes include:
  • Long-term steroid use (e.g., corticosteroids).
  • Excessive alcohol consumption.
  • Sickle cell disease.
  • Gaucher's disease.
  • Lupus erythematosus.
  • Radiation therapy.
  • Decompression sickness (Caisson disease).

Pathophysiology

• AVN occurs due to ischaemia and interruption of blood flow to the femoral head, leading to the death of bone cells.
• This lack of blood supply can result from trauma or medical conditions that impair circulation.
• The dead bone tissue weakens, and the femoral head can collapse, resulting in the joint's structural failure.

Risk Factors

• Chronic steroid use.
• Excessive alcohol intake.
• Trauma (e.g., hip fractures, dislocations).
• Autoimmune diseases (e.g., lupus).
• Sickle cell disease and other hemoglobinopathies.
• Deep-sea diving or high-altitude decompression (causing nitrogen bubbles in blood).

Clinical Presentation

• Early-stage AVN: Often asymptomatic or mild pain in the groin, thigh, or buttock.
• Progressive AVN:
  • Increasing pain in the hip joint, particularly with weight-bearing activities.
  • Limited range of motion and stiffness in the hip joint.
  • As the femoral head collapses, severe pain and functional impairment occur.

Investigations

• X-ray: May show normal results in early stages but later shows femoral head collapse and joint space narrowing.
• MRI: The most sensitive test for detecting early AVN. It can show bone marrow edema and early necrotic changes.
• CT Scan: Useful in assessing the extent of bony collapse.
• Bone Scan: Can show decreased uptake in the area of necrosis (cold spots) in AVN.

Stages of Avascular Necrosis

• Stage I: No visible changes on X-ray; MRI shows early bone changes.
• Stage II: Sclerosis and cyst formation on X-ray, no collapse.
• Stage III: Subchondral fracture ("crescent sign") on X-ray; beginning of femoral head collapse.
• Stage IV: Femoral head collapse with joint space narrowing and early osteoarthritis.

Management

• Conservative Management:
  • Rest and reduced weight-bearing on the affected hip.
  • NSAIDs for pain relief.
  • Bisphosphonates to slow bone loss.
  • Physical therapy to maintain joint mobility and muscle strength.
• Surgical Management:
  • Core Decompression: Surgical drilling to relieve pressure and improve blood flow in early stages.
  • Bone Grafting: Insertion of healthy bone to promote healing.
  • Osteotomy: Repositioning of bone to offload stress on the damaged femoral head.
  • Hip Replacement: Total hip arthroplasty is the definitive treatment for advanced cases with femoral head collapse.

Complications

• Osteoarthritis of the hip joint due to femoral head collapse.
• Joint stiffness and immobility.
• Chronic pain and disability.

Prognosis

• The prognosis depends on the stage at diagnosis and promptness of treatment.
• Early detection and management can slow the progression of the disease.
• Without treatment, most cases of AVN result in femoral head collapse and osteoarthritis requiring hip replacement.

References

• Avascular Necrosis of Femoral Head - NCBI
• American Academy of Orthopaedic Surgeons