26 Questions
What are the primary functions of the cells described in the text?
To produce cartilage and bone matrix
What is required for the bone matrix produced by these cells to remodel into normal lamellar bone?
Adequate immobilization
What type of bone is produced by the remodeling process described in the text?
Lamellar bone
Which of the following best describes the role of immobilization in the bone remodeling process?
It enables the remodeling process
What is the primary component of the bone matrix produced by the cells described in the text?
Collagen fibers
What is another name for osteonecrosis?
Vascular necrosis
Which type of osteonecrosis results in the collapse of bone, fracture, and sloughing of articular cartilage?
Subchondral
What is a common cause of osteonecrosis in patients with sickle cell disease?
Thrombosis
Which organism commonly causes pyogenic osteomyelitis due to its ability to bind easily to collagen in the osteoid matrix?
Staphylococcus aureus
How does pyogenic osteomyelitis in children most commonly reach the bones?
Hematogenous route
What is the main source of nutrients that keep the overlying articular cartilage intact in subchondral osteonecrosis?
Synovial fluid
What type of tissue forms after one week in the healing process of a fracture?
Uncalcified new tissue
What happens to the soft callus after two weeks in the healing process of a fracture?
It is converted to bony callus by deposition of woven bone
Which type of bone is deposited during the conversion of soft callus to bony callus?
Woven bone
What is the composition of the initial soft callus formed after one week?
Uncalcified new tissue
What characterizes the conversion process of the soft callus to bony callus after two weeks?
Deposition of woven bone
What is the term used to describe the drainage tract in the subperiosteal shell of viable new bone?
Sinus tract
Which part of the new bone is necrotic and labeled with the red arrow?
Sequestrum
The original cortex seen in the drainage tract is characteristic of:
Osteomyelitis
What color arrow is used to indicate the involucrum in the drainage tract?
Yellow
The presence of a sequestrum within the drainage tract indicates:
Necrotic bone
What is the first step in the process of bone healing?
Formation of an organizing hematoma
What is the process by which new cartilage formation at the fracture site is converted into bone?
Endochondral ossification
What happens to the callus during the later stages of bone healing?
It undergoes remodeling according to weight-bearing forces and reduces in size and shape
What is the final step in the process of bone healing?
Formation of the medullary cavity
What is the purpose of the remodeling process during bone healing?
To adapt the newly formed bone to the weight-bearing forces
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
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.
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