Idiopathic Femoral Head Necrosis

Question 1

Epidemiology

Answer 1

• Average age affected is 35 to 50
• Males > Females
• Bilateral hip involvement in ~80% cases
• Multifocal osteonecrosis possible [3% cases]

Question 2

Etiology

Answer 2

Idiopathic:
- Many nontraumatic causes that ultimately lead to Intravascular Coagulation
- Coagulation of intraosseous microcirc -> Venous thrombosis -> Retrograde arterial occlusion -> Intraosseous HTN -> Decreased blood flow to femoral head -> AVN femur head -> Chondral fracture and collapse

Some non-traumatic causes can include:
- Alcoholism
- Sickle Cell disease
- SLE
- Exogenous and Endogenous steroids [Corticosteroid abuser]
- Infection [viruses - CMV, Hep, HIV, Rubella]
- Caisson disease
- Hypercoagulable states
- Transplant patient

Question 3

Classification

Answer 3

Modified FICAT classification:
- Stage 0: Normal Radio | Normal MRI and Bone scan
- Stage I: Normal Radio | Abnormal MRI and/or Bone scan [edema]
- Stage II: Cystic or Sclerosis changes [without crescent sign] Radio | Abnormal MRI and/or Bone scan
- Stage III: Crescent Sign [Subchondral collapse] Radio | Abnormal MRI and/or Bone scan
- Stage IV: Flattening of Femoral head [without degen changes] Radio | Abnormal MRI and/or Bone scan
- Stage V: Narrowing of Joint space Radio | Abnormal MRI and/or Bone scan
- Stage VI: Advanced degenerative changes Radio | Abnormal MRI and/or Bone scan

Question 4

Presentation

Answer 4

Insidious onset:
- Pain
- Pain with stairs, inclines and impact
- Pain common in anterior hip
- Groin pain
- Antalgic gait

Physical Exam:
- Advanced stages shows limited motion, particularly internal rotation
- Click sound may be heard while standing
- Groin pain

Question 5

Imaging

Answer 5

Radiographs:
- AP hip
- Frog Lateral of hip
- AP and Lateral of contralateral hip
- Classifications based largely on these findings

MRI:
- Highest sensitivity and specificity
- T1: dark
- T2: focal brightness [marrow edema]
- Order when radiographs negative but suspection of Osteonecrosis still present
- Bone marrow edema on MRI is predictive of worsening pain and future progression of disease

Bone scan [SPECT may show vascular integritiy]

Question 6

Treatment

Answer 6

Non-Operative:
- Bisphosphonates
- Precollapse AVN indication [FICAT stages 0-II]

Operative:
- Core Decompression with/without bone grafting [before Stage III]: relieves intraosseous HTN and gives less pain symptoms. stims angiogenesis healing | Basically make one hole or poke holes multiple times
- Rotational Osteotomy [small lesions that can be rotated away from a weaight bearing surface]: Valgus flexion for anterolateral disease | Varus rotational for medial disease
- Curettage and bone grafting [precollapse, 2 main approaches to place bone graft in necrotic area]
- THR [Uncemented]: in younger patients with crescent or more advanced head collapse, irreversible etiology, patients > 40 years with large lesions
- Hemiarthroplasty of Hip joint