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Questions and Answers
What are the primary functions of the cells described in the text?
What are the primary functions of the cells described in the text?
What is required for the bone matrix produced by these cells to remodel into normal lamellar bone?
What is required for the bone matrix produced by these cells to remodel into normal lamellar bone?
What type of bone is produced by the remodeling process described in the text?
What type of bone is produced by the remodeling process described in the text?
Which of the following best describes the role of immobilization in the bone remodeling process?
Which of the following best describes the role of immobilization in the bone remodeling process?
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What is the primary component of the bone matrix produced by the cells described in the text?
What is the primary component of the bone matrix produced by the cells described in the text?
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What is another name for osteonecrosis?
What is another name for osteonecrosis?
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Which type of osteonecrosis results in the collapse of bone, fracture, and sloughing of articular cartilage?
Which type of osteonecrosis results in the collapse of bone, fracture, and sloughing of articular cartilage?
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What is a common cause of osteonecrosis in patients with sickle cell disease?
What is a common cause of osteonecrosis in patients with sickle cell disease?
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Which organism commonly causes pyogenic osteomyelitis due to its ability to bind easily to collagen in the osteoid matrix?
Which organism commonly causes pyogenic osteomyelitis due to its ability to bind easily to collagen in the osteoid matrix?
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How does pyogenic osteomyelitis in children most commonly reach the bones?
How does pyogenic osteomyelitis in children most commonly reach the bones?
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What is the main source of nutrients that keep the overlying articular cartilage intact in subchondral osteonecrosis?
What is the main source of nutrients that keep the overlying articular cartilage intact in subchondral osteonecrosis?
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What type of tissue forms after one week in the healing process of a fracture?
What type of tissue forms after one week in the healing process of a fracture?
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What happens to the soft callus after two weeks in the healing process of a fracture?
What happens to the soft callus after two weeks in the healing process of a fracture?
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Which type of bone is deposited during the conversion of soft callus to bony callus?
Which type of bone is deposited during the conversion of soft callus to bony callus?
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What is the composition of the initial soft callus formed after one week?
What is the composition of the initial soft callus formed after one week?
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What characterizes the conversion process of the soft callus to bony callus after two weeks?
What characterizes the conversion process of the soft callus to bony callus after two weeks?
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What is the term used to describe the drainage tract in the subperiosteal shell of viable new bone?
What is the term used to describe the drainage tract in the subperiosteal shell of viable new bone?
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Which part of the new bone is necrotic and labeled with the red arrow?
Which part of the new bone is necrotic and labeled with the red arrow?
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The original cortex seen in the drainage tract is characteristic of:
The original cortex seen in the drainage tract is characteristic of:
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What color arrow is used to indicate the involucrum in the drainage tract?
What color arrow is used to indicate the involucrum in the drainage tract?
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The presence of a sequestrum within the drainage tract indicates:
The presence of a sequestrum within the drainage tract indicates:
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What is the first step in the process of bone healing?
What is the first step in the process of bone healing?
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What is the process by which new cartilage formation at the fracture site is converted into bone?
What is the process by which new cartilage formation at the fracture site is converted into bone?
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What happens to the callus during the later stages of bone healing?
What happens to the callus during the later stages of bone healing?
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What is the final step in the process of bone healing?
What is the final step in the process of bone healing?
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What is the purpose of the remodeling process during bone healing?
What is the purpose of the remodeling process during bone healing?
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Study Notes
Osteonecrosis (Avascular Necrosis)
- Also known as avascular necrosis, characterized by ischemic infarction of bone and bone marrow
- Most commonly affects middle-aged adults
- Causes: vascular injury, drug-induced (corticosteroids), radiation, and thrombosis (sickle cell disease)
Types of Osteonecrosis
- Medullary: infarction of trabecular bone and bone marrow, cortical bone is spared due to collateral circulation
- Subchondral: wedge-shaped, results in bone collapse, fracture, and sloughing of articular cartilage
Characteristics of Osteonecrosis
- No visible osteocytes (empty lacunae) microscopically
- Osteoclasts from adjacent viable areas start resorbing dead bone
- Repair of subchondral infarction is slow
Symptoms of Osteonecrosis
- Pain, begins with activity and becomes constant
- Secondary osteoarthritis develops if articular cartilage is sloughed
Osteomyelitis
- Inflammation of bone and bone marrow
- Almost always infectious in origin, caused by bacteria, viruses, and fungi
Pyogenic Osteomyelitis
- Caused by bacterial infection
- Organisms reach bone through hematogenous route, extension from adjacent site, or direct implantation
- Most common in children: hematogenous and affects long bones
- Most common in adults: secondary to fractures, surgery, or diabetes (diabetic foot)
Characteristics of Pyogenic Osteomyelitis
- Staph Aureus is the most common microorganism, binding easily to collagen in osteoid matrix
- In neonates: group B-streptococci and E. coli are common microorganisms
Fracture Healing
- Reaction to a fracture begins with an organizing hematoma
- Callus formation: soft callus (procallus) forms after one week, and is converted to bony callus by deposition of woven bone after two weeks
- Contour of new bone is re-established, and shows lamellar bone
- Formation of medullary cavity is the final step in bone healing
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Description
Learn about osteonecrosis, also known as avascular necrosis, ischemic infarction of bone and bone marrow. Understand the various causes including vascular injury, drugs, radiation, and thrombosis. Explore the types of osteonecrosis such as medullary and subchondral.
