Avascular Necrosis: Causes and Treatment

Coleman D. Fowble, M.D.

Midlands Orthopaedics, P.A.

Columbia, SC

Introduction

• DefinitionLoss of blood flow to the bone leading to death of

the cellular components of bone.

Avascular Necrosis

• AVN• Osteonecrosis• Aseptic necrosis• Ischemic necrosis• Bone infarction

Bones Affected

• Femoral head – most common by far• Shoulder – humeral head• Odontoid (Neck)• Scaphoid (Wrist)• Lunate (Wrist)• Talus (Ankle)

Examples

Treatment

• Frustrating• Staging very subjective in lower stages

Etiologies

• Trauma• Alcohol• Steroids• Diving (Caisson’s Disease)• Sickle Cell• Idiopathic (up to 30% of cases)

Symptoms

• Pain• Decreased range of motion

Risk Factors

• Alcoholism• Pancreatitis• Diabetes• Gout

Staging

• Initially radiographic staging• Revised with advancement of MRI

Classification

• FicatOriginal x-ray classification of hip

• Other classifications exist for talus, scaphoid, etc.

Stage 0

• No clinical symptoms• No radiographic abnormalities• Microscopic diagnosis

Stage I

• May or may not have symptoms• Radiographs and CT are normal• MRI is abnormal as is bone scan• Microscopic exam confirms diagnosis

Stage II

• Patient is symptomatic• X-rays show osteopenia, sclerosis, cysts• No subchondral lucency or collapse• MRI confirms diagnosis

Stage III

• X-rays show subchondral lucency and collapseCrescent sign

• Shape of femoral head is preserved• Subclassified by extent of crescent

IIIa 15% of headIIIb 15-30% of aheadIIIc greater than 30%

Stage IV

• Flattening or collapse of head on x-ray• Loss of joint space• Subclassified by extent of collapse like Stage III

IVaIVbIVc

MRI Stage IV

Stage V

• Arthritic changes evident on x-rays with loss of joint space and spurring

• May affect acetabular side of the joint

Stage V

Stage VI

• Extensive destruction of femoral head and joint

• May be indistinguishable from osteoarthritis

Treatment Options

• Stage dependent• Clinical signs and symptoms• Physiologic condition• Age• Medical comorbidities

Observation

• Normal x-ray• Possible abnormal MRI• No clinical signs or symptoms

Core Decompression

• Stage I or II• With or without hardware• Age

Core Decompression

• Added fixation

Free Vascularized Fibular Graft

• Pioneered in 1979 by Dr. Urbaniak at Duke• Over 2500 performed• Multidisciplinary approach• Only center with real consistent results

Core Decompression

• Vascularized fibular graft

Partial Resurfacing

• No Longer in favor• Disastrous results

LooseningFractureMigration of implant

Hip Replacement

• Too much destruction of head• Age

Hip Resurfacing

• Age• Bone preserving• More functional hip replacement

Total Hip Versus Resurfacing

Workman's Compensation

• Trauma• Secondary injury• Difficult

May take several years to show up

Femoral Neck Fracture

• Basilar neck• Transcervical• Subcapital• Intertrochanteric

Femoral Neck Fracture

• Location of fracture determines risk of AVN

Treatment Examples

• Fracture pattern determines treatment• Other factors

AgeComorbidities

Transcervical Fracture

Fixation

• 3 Screws• Screw and sideplate• Intramedullary device

AVN After Treatment

• AVN can occur long after treatment

Replacement

• Hemiarthroplasty• Total hip

Summary

• AVN is the disruption of the blood supply to bone

• There are multiple causes• Diagnosis may be delayed• Treatment is dependent on stage and other

factors

Sources

Staging of Avascular Necrosis. Orthopaedia Main. In: Orthopaedia-Collaborative Orthopaedic Knowledgebase

JBJS Br. Core Decompression of the Distal Femur. Vol. 71-B. August, 1989

JBJS. Treatment of Osteonecrosis with Free Vascularized Fibular Graft. Vol 77. 1995