http://upload.orthobullets.com/topic/8078/images/bone infarct xray.jpg
http://upload.orthobullets.com/topic/8078/images/bone infarct mri.jpg
Introduction
  • Overview
    • bone infarcts are often thought to be in the same spectrum of disease as osteonecrosis
    • occurs within the metaphysis or diaphysis of long bone
  • Epidemiology & Incidence
    • similar risk factors as those seen in osteonecrosis
      • trauma, sickle cell disease, connective tissue disorders, Gaucher's disease, steroid use
  • Mechanism
    • interruption of blood supply by intrinsic or extrinsic factors
Presentation
  • Symptoms
    • usually asymptomatic
      • often found when imaging the extremities for other reasons
Imaging
  • Radiographs  
    • medullary lesion of sheet-like central lucency surrounded by sclerosis with a serpiginous border  
      • "smoke up the chimney"
  • MRI 
    • key feature is that central signal remains of normal marrow 
    • T1 weighted images
      • peripheral low signal due to grannulation tissue and to lesser extent sclerosis
      • periphery may enhance post gadolinium
    • T2 weighted images
      • acute infarct may show ill-defined non-specific area of high signal
      • intense inner ring of granulation tissue and a hypointense outer ring of sclerosis
  • Bone Scan
    • cold in early phases
    • hot in late resorptive and revascularisation phase
Treatment
  • Nonoperative
    • observation
      • indications
        • usually asymptomatic and do not require treatment
 

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Questions (1)

(OBQ08.167) A 45-year-old female twists her knee suddenly while playing tennis. She denies any history of knee pain in the past. Radiographs are shown in Figure A. What is the diagnosis? Review Topic

QID:553
FIGURES:
1

Bone infarct

82%

(843/1034)

2

Osteonecrosis

2%

(18/1034)

3

Metastatic carcinoma

1%

(9/1034)

4

Osteosarcoma

1%

(6/1034)

5

Enchondroma

15%

(152/1034)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

Idiopathic bone infarcts often occur in the metaphysis of long bones such as the femur and tibia. They are often asymptomatic and found on imaging studies for other reasons. The infarcted area undergoes progressive, but incomplete resorptive replacement. The bone infarct becomes surrounded by a thick and calcified fibro-osseous wall in a healing attempt. This accounts for the blotchy medullary and linear peripheral shadows seen in radiographs of old bone infarcts resembling “smoke up the chimney”.

Bone scans are cold in the early stages and hot as revascularisation occurs. The etiology is thought to be related to intrinsic/extrinsic vascular compromise such as atherosclerosis, arteritis, and thrombosis. Biopsy (usually unnecessary) shows mineralization of necrotic marrow elements. Bone infarcts usually are asymptomatic, and no treatment is required. If a patient presents with pain, another etiology should be sought. Rarely, malignancy, such as a malignant fibrous histiocytoma, can occur at the site of a bone infarct


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