Osteonecrosis Of The Hip

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Modern Study Review (AI-Generated)

High-Yield Summary

Osteonecrosis of the hip (ONFH) primarily affects young adults aged 30-50 and is characterized by progressive femoral head collapse leading to secondary osteoarthritis. Early diagnosis with MRI is critical, as intervention before collapse improves outcomes. Current management balances head-preserving procedures in early stages against arthroplasty in advanced disease, with lesion size and patient factors guiding treatment choice.

Key Diagnostic Findings

AspectDetails
AnatomyFemoral head subchondral bone and marrow affected by ischemia leading to osteocyte death
Clinical PresentationInsidious onset groin pain, limited hip ROM, often in young adults (30-50 years)
Imaging– Early: MRI (gold standard) shows bone marrow edema and necrosis
– X-rays: sclerosis, cysts, crescent sign, collapse, secondary arthritis
Classification SystemsFicat Classification:
0: Asymptomatic, MRI positive
I: Normal X-ray
II: Sclerosis/cysts
III: Crescent sign, subchondral collapse
IV: Osteoarthritis

University of Pennsylvania:
0: Asymptomatic, MRI positive
I: Normal X-ray
II: Sclerosis/cysts
III: Crescent sign only
IV: Subchondral collapse
V: Early arthritis
VI: Late arthritis
(A, B, C denote lesion size)

Current Gold Standard Treatment

Stage / Lesion SizeTreatment Approach
Pre-collapse (Ficat I-II)– Core decompression (best for small, central lesions)
– Vascularized bone grafting (young, <55 years, no steroids)
– Osteotomy (if lesion <30% or <200° necrotic arc)
Early collapse (Ficat III)– Limited success with core decompression and osteotomy
– Consider vascularized grafting cautiously
Advanced collapse (Ficat IV or >30% lesion)– Total hip arthroplasty (THA) is gold standard
– Head-preserving procedures generally fail in large lesions or late stages

Modern Complications & Outcomes

  • Progression to Collapse: Occurs in ~80% without intervention; early treatment improves survival of femoral head.
  • Failure Rates: Higher in young, active patients; corticosteroid use and large lesion size worsen prognosis.
  • Complications of Surgery: Include donor site morbidity (vascularized graft), nonunion (osteotomy), infection, and persistent pain.
  • Long-Term Outcomes: THA provides reliable pain relief and function in advanced disease; head-preserving procedures aim to delay arthroplasty but have variable success.
  • Emerging Therapies: Biologic adjuncts (stem cells, growth factors) under investigation to improve bone remodeling and vascularization.

Classic Clinical Notes

Osteonecrosis of the Hip

  • Often in young patients (30-50)
  • Natural history (we think) is that of progressive collapse (in 80%)
  • Higher failure rate in these young patients with this diagnosis, even when accounting for age and activity level; ? necrotic bone with altered remodeling?
  • Pathophysiology is not well understood. Four hypotheses exist – none are particularly solid:
    1. Direct cellular mechanisms – death of osteocytes
    2. Extraosseous arterial mechanisms – reduction in blood flow to the head
    3. Extraosseous venous mechanisms – venous stasis
    4. Intraosseous extravascular mechanisms – inflammatory marrow edema
    5. In truth, the disease is probably multifactorial, and there is a concept of “multiple hits” of multiple insults, superimposed on what might be a genetic susceptibility.

Classification

Ficat ClassificationUniversity of Pennsylvania Classification
0 – asymptomatic, normal x-rays – abnormal MRI0 – asymptomatic, normal x-rays, abnormal MRI
I – normal x-raysI – normal x-rays
II – sclerosis or cystic lesionsII – sclerosis or cystic lesions
III – crescent sign with subchondral collapseIII – crescent sign only
IV – osteoarthrosisIV – subchondral collapse
V – early arthritis
VI – late arthritis * A, B, C depending on size of lesion (For any given stage)

Head Preserving Treatment

Core Decompression

  • Good results in Ficat I and II; moderate in Ficat III (47% survival)

  • Probably best for Ficat I and II, small, central lesions in young, non-obese patient not on steroids

  • Success rate is closer to 20% in post-collapse

Osteotomy

  • To move the diseased part of the head into a less weightbearing area

  • Critical size is 30% or 200° combined necrotic arc angle on AP and lateral – beyond this, don’t try osteotomy!

  • Probably effective only for Ficat I and II, and very early stage III hips.

Nonvascularized Grafting

  • Structural grafting through the core decompression track

  • Cancellous and cortical grafting through femoral neck and head

  • Osteochondral grafting

Vascularized Grafting

  • Decompresses the femoral head, provides structural support, removes dead bone, increases vascularization, and provides additional cancellous bone

  • In general, best for young patients with early disease (like all the rest)

  • Patients over 55 are not candidates, as are patients on continued corticosteroids

  • Still has somewhat limited results in hips with more than 30% head involvement

In general – when the lesion is >200° combined necrotic angle or greater than 30% head involvement, the head preserving techniques have not been very successful (including vascularized grafting)

Last Updated on January 24, 2026 by orthonet

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