L14 – Bone Pathology: Osteomyelitis, Metabolic Disorders and Bone Tumours

Question 1

What are the two major types of bone tissue?

Answer 1

Compact (cortical) bone and cancellous (trabecular) bone.

Question 2

What is the functional significance of osteons in compact bone?

Answer 2

Osteons provide structural strength and support by organising bone into cylindrical units with a central canal.

Question 3

How does cancellous bone differ from cortical bone?

Answer 3

Cancellous bone is spongy, with a trabecular structure that supports metabolic functions and houses bone marrow.

Question 4

What is osteomyelitis and how does it typically develop?

Answer 4

Osteomyelitis is an infection of the bone, usually resulting from haematogenous spread or direct inoculation after trauma.

Question 5

What is the primary pathophysiological defect in osteomalacia?

Answer 5

Inadequate mineralisation of the osteoid matrix due to vitamin D deficiency or related metabolic disturbances.

Question 6

How does rickets differ from osteomalacia?

Answer 6

Rickets occurs in children with growing bones, leading to bone deformities, while osteomalacia affects mature bone, causing pain and fragility.

Question 7

What role does activated vitamin D play in bone mineralisation?

Answer 7

Activated vitamin D is crucial for the absorption of calcium and phosphate, essential for proper bone mineralisation.

Question 8

What are Looser’s zones and what do they signify in osteomalacia?

Answer 8

Looser’s zones are radiolucent areas seen on X-rays indicating areas of unmineralised osteoid and microfractures.

Question 9

How can intrinsic disturbances in vitamin D production occur?

Answer 9

They may result from limited sunlight exposure, dietary deficiency, malabsorption syndromes, or impaired renal conversion.

Question 10

What is osteitis fibrosa cystica, and which condition is it associated with?

Answer 10

Osteitis fibrosa cystica is a bone disorder characterised by cystic and fibrous changes, commonly due to hyperparathyroidism.

Question 11

How does hyperparathyroidism lead to bone changes?

Answer 11

Excess parathyroid hormone causes increased bone resorption, resulting in cystic lesions and fibrous replacement of bone.

Question 12

What are common clinical signs of hyperparathyroidism affecting bone?

Answer 12

Patients may present with bone pain, pathological fractures, and elevated serum calcium levels.

Question 13

What is Paget’s disease of bone?

Answer 13

A chronic disorder of disorganised bone remodelling, leading to enlarged and weakened bones.

Question 14

Which demographic is most commonly affected by Paget’s disease?

Answer 14

It primarily affects older adults, typically those over 55 years of age.

Question 15

What is the typical radiological appearance of osteosarcoma?

Answer 15

Osteosarcoma often shows a mixed lytic-sclerotic lesion with periosteal reaction and subperiosteal new bone formation.

Question 16

What age group is most affected by high-grade intramedullary osteosarcoma?

Answer 16

It is most common in teenagers during periods of rapid skeletal growth, with a peak around 15 years.

Question 17

What are the common anatomical sites for osteosarcoma?

Answer 17

The distal femur and proximal tibia, particularly around the knee, are the most frequent sites.

Question 18

How is osteosarcoma histologically defined?

Answer 18

It is characterised by malignant osteoblasts producing osteoid in a disorganised, often high-grade, pattern.

Question 19

What are enchondromas?

Answer 19

Enchondromas are benign cartilaginous tumours that develop within the medullary cavity of bones.

Question 20

What defines an osteochondroma?

Answer 20

Osteochondromas are benign bony exostoses with a cartilage cap, typically arising from the metaphyseal region of long bones.

Question 21

How are chondrosarcomas classified?

Answer 21

They are classified based on location (intramedullary vs peripheral) and histological grade (conventional, myxoid, clear cell, dedifferentiated).

Question 22

At what age do chondrosarcomas typically present?

Answer 22

They most commonly occur in individuals over 40 years, with a slight male predominance.

Question 23

What is the prognostic significance of histological grading in bone tumours?

Answer 23

The histological grade correlates with tumour aggressiveness, metastatic potential, and guides treatment planning.

Question 24

How does tumour size affect the management of bone tumours?

Answer 24

Larger tumours often indicate a more aggressive disease and may require more extensive surgical resection and adjuvant therapy.

Question 25

What imaging modalities are used to evaluate bone lesions?

Answer 25

Conventional radiography, CT, MRI, and bone scintigraphy are commonly used to assess bone pathology.

Question 26

What is the clinical relevance of DEXA scans in metabolic bone disease?

Answer 26

DEXA scans measure bone mineral density, aiding in the diagnosis of conditions like osteomalacia and osteoporosis.

Question 27

Which laboratory tests are essential in evaluating metabolic bone diseases?

Answer 27

Serum calcium, phosphate, alkaline phosphatase, and vitamin D levels are crucial.

Question 28

How does measurement of parathyroid hormone (PTH) aid in diagnosing bone pathology?

Answer 28

Elevated PTH levels help diagnose hyperparathyroidism, which leads to increased bone resorption.

Question 29

What radiological finding is characteristic of osteomalacia in adults?

Answer 29

The presence of Looser’s zones, which are radiolucent bands representing unmineralised osteoid.

Question 30

What is the significance of subperiosteal new bone formation in osteosarcoma?

Answer 30

It is a radiological sign that supports the diagnosis and indicates aggressive periosteal reaction.

Question 31

How do bone tumours cause pathological fractures?

Answer 31

Tumour-induced weakening of the bone structure predisposes to fractures even with minimal trauma.

Question 32

What is the difference between metabolic and neoplastic bone diseases?

Answer 32

Metabolic bone diseases affect bone density and mineralisation diffusely, while neoplastic diseases present as focal lesions.

Question 33

Why is a multidisciplinary approach essential in bone tumour management?

Answer 33

It ensures accurate diagnosis, optimal surgical planning, and integration of chemotherapy or radiotherapy as needed.

Question 34

How do intrinsic and extrinsic factors contribute to metabolic bone disorders?

Answer 34

Intrinsic factors include genetic and hormonal influences, while extrinsic factors involve diet, sunlight exposure, and renal function.

Question 35

What is the overall goal of a comprehensive evaluation in bone pathology?

Answer 35

To accurately diagnose the underlying condition—whether metabolic, infectious, or neoplastic—thus guiding appropriate treatment and improving patient outcomes.

Question 36

What are the most common tumors found in bone?

Answer 36

The most common tumors found in bone are usually metastatic, not primary.

Question 37

What are the different types of bone?

Answer 37

Bone can be classified into tubular bones (like those in the arms and legs), small tubular bones (like those in the hands and feet), and flat bones (like those in the pelvis and scapula).

Question 38

What is the structure of bone?

Answer 38

Bone typically has a cortex (the hard outer shell) and a central component made of cancellous bone or trabecular bone, which is a network of thin, interconnected bone structures.

Question 39

What is the role of the cortex in bone?

Answer 39

The cortex provides support and resistance to weight and lateral trauma.

Question 40

What does cancellous bone house?

Answer 40

Cancellous bone houses the intertrabecular marrow, where hematopoietic cells are produced.

Question 41

What happens to bone when it undergoes constant remodeling?

Answer 41

Bone undergoes the deposition of new bone and resorption of old bone, allowing it to grow and respond to physiological needs such as the demand for calcium and phosphate.

Question 42

How does immobilization affect bones?

Answer 42

When a bone is fractured and immobilized, the fracture site and the entire limb can be affected due to under-utilization.

Question 43

How do infections commonly affect bones?

Answer 43

Infections can spread to bone from the bloodstream, adjacent sites, or via trauma or surgery, especially orthopedic surgeries intended to repair joints or stabilize fractures.

Question 44

What is a risk factor for bone infections in diabetic patients?

Answer 44

Skin ulcers, particularly due to poor circulation and neuropathy, pose an increased risk for bone infections in diabetic patients.

Question 45

How do infections in bone differ in children and adults?

Answer 45

In children, long bones are more commonly affected, while in adults, infections often localize in the spine.

Question 46

Why are hemodialysis patients at higher risk for osteomyelitis?

Answer 46

Hemodialysis patients are at increased risk of osteomyelitis due to contamination.

Question 47

What happens to bone during an infection?

Answer 47

Osteoclasts attack infected bone, which can lead to abscess formation due to the closed structure of bone limiting the inflammatory response.

Question 48

What is the risk of infection in bones from contiguous spread?

Answer 48

Contiguous spread can occur from adjacent soft tissue to bone, especially in cases of ulcers or dental infections.

Question 49

What characterizes osteomalacia and rickets?

Answer 49

Osteomalacia and rickets are characterized by insufficient mineralization, with rickets affecting developing skeletons in children and osteomalacia impacting mature skeletons.

Question 50

What is osteoporosis, and who is most at risk?

Answer 50

Osteoporosis is a metabolic bone disease characterized by weakened bone density, with the elderly being most at risk, especially when multiple conditions are present.

Question 51

What causes osteitis fibrosa cystica?

Answer 51

Osteitis fibrosa cystica results from hyperparathyroidism, which leads to the overproduction of parathyroid hormone, causing bone resorption and the creation of lesions.

Question 52

What is Paget's disease of bone?

Answer 52

Paget’s disease involves abnormal, disorganized bone remodeling, which can increase the risk of osteosarcomas, particularly in older individuals.

Question 53

How are benign bone tumors different from malignant bone tumors?

Answer 53

Benign bone tumors do not metastasize but may cause pain or fractures, while malignant tumors, such as osteosarcomas, can spread and are more aggressive.

Question 54

Which type of bone tumor is most common in young adults?

Answer 54

Osteosarcomas are the most common primary bone tumors in young adults.

Question 55

At what age do chondrosarcomas typically arise?

Answer 55

Chondrosarcomas typically arise in individuals over 40 years of age.

Question 56

What condition can chondrosarcomas be associated with?

Answer 56

Chondrosarcomas can be associated with conditions like Ollier's disease.

Question 57

What are the primary functions of the skeletal system?

Answer 57

The primary functions of the skeletal system include providing structural support, protecting vital organs, facilitating movement, storing minerals, and housing bone marrow for blood cell production.

Question 58

How does bone remodeling contribute to calcium homeostasis?

Answer 58

Bone remodeling contributes to calcium homeostasis by balancing bone resorption and formation, thus regulating calcium levels in the blood.

Question 59

What is the significance of the periosteum in bone health?

Answer 59

The periosteum is significant in bone health as it contains nerves and blood vessels that nourish bone tissue and is involved in bone growth and repair.

Question 60

How do osteoblasts and osteoclasts interact during bone remodeling?

Answer 60

Osteoblasts and osteoclasts interact during bone remodeling by coordinating the processes of bone formation and resorption, respectively, to maintain bone integrity.

Question 61

What is the role of collagen in bone structure?

Answer 61

Collagen in bone structure provides tensile strength and flexibility, allowing bones to withstand various stresses without breaking.

Question 62

How does age affect bone density and strength?

Answer 62

Age affects bone density and strength by leading to a decrease in bone mass and an increased risk of fractures due to changes in bone remodeling dynamics.

Question 63

What is the impact of mechanical stress on bone remodeling?

Answer 63

Mechanical stress impacts bone remodeling by stimulating bone formation, thereby increasing bone density and strength in response to physical activity.

Question 64

How do hormones influence bone growth and maintenance?

Answer 64

Hormones such as parathyroid hormone, calcitonin, and sex hormones influence bone growth and maintenance by regulating bone remodeling and calcium metabolism.

Question 65

What are the differences between woven bone and lamellar bone?

Answer 65

Woven bone is characterized by a haphazard organization of collagen fibers and is typically found in newly formed bone, while lamellar bone has a regular parallel alignment of collagen fibers and is mechanically stronger.

Question 66

How does nutrition affect bone health?

Answer 66

Nutrition affects bone health by providing essential nutrients like calcium and vitamin D, which are crucial for bone mineralization and overall skeletal integrity.