L14 – Bone Pathology: Osteomyelitis, Metabolic Disorders and Bone Tumours Flashcards
What are the two major types of bone tissue?
Compact (cortical) bone and cancellous (trabecular) bone.
What is the functional significance of osteons in compact bone?
Osteons provide structural strength and support by organising bone into cylindrical units with a central canal.
How does cancellous bone differ from cortical bone?
Cancellous bone is spongy, with a trabecular structure that supports metabolic functions and houses bone marrow.
What is osteomyelitis and how does it typically develop?
Osteomyelitis is an infection of the bone, usually resulting from haematogenous spread or direct inoculation after trauma.
What is the primary pathophysiological defect in osteomalacia?
Inadequate mineralisation of the osteoid matrix due to vitamin D deficiency or related metabolic disturbances.
How does rickets differ from osteomalacia?
Rickets occurs in children with growing bones, leading to bone deformities, while osteomalacia affects mature bone, causing pain and fragility.
What role does activated vitamin D play in bone mineralisation?
Activated vitamin D is crucial for the absorption of calcium and phosphate, essential for proper bone mineralisation.
What are Looser’s zones and what do they signify in osteomalacia?
Looser’s zones are radiolucent areas seen on X-rays indicating areas of unmineralised osteoid and microfractures.
How can intrinsic disturbances in vitamin D production occur?
They may result from limited sunlight exposure, dietary deficiency, malabsorption syndromes, or impaired renal conversion.
What is osteitis fibrosa cystica, and which condition is it associated with?
Osteitis fibrosa cystica is a bone disorder characterised by cystic and fibrous changes, commonly due to hyperparathyroidism.
How does hyperparathyroidism lead to bone changes?
Excess parathyroid hormone causes increased bone resorption, resulting in cystic lesions and fibrous replacement of bone.
What are common clinical signs of hyperparathyroidism affecting bone?
Patients may present with bone pain, pathological fractures, and elevated serum calcium levels.
What is Paget’s disease of bone?
A chronic disorder of disorganised bone remodelling, leading to enlarged and weakened bones.
Which demographic is most commonly affected by Paget’s disease?
It primarily affects older adults, typically those over 55 years of age.
What is the typical radiological appearance of osteosarcoma?
Osteosarcoma often shows a mixed lytic-sclerotic lesion with periosteal reaction and subperiosteal new bone formation.
What age group is most affected by high-grade intramedullary osteosarcoma?
It is most common in teenagers during periods of rapid skeletal growth, with a peak around 15 years.
What are the common anatomical sites for osteosarcoma?
The distal femur and proximal tibia, particularly around the knee, are the most frequent sites.
How is osteosarcoma histologically defined?
It is characterised by malignant osteoblasts producing osteoid in a disorganised, often high-grade, pattern.
What are enchondromas?
Enchondromas are benign cartilaginous tumours that develop within the medullary cavity of bones.
What defines an osteochondroma?
Osteochondromas are benign bony exostoses with a cartilage cap, typically arising from the metaphyseal region of long bones.
How are chondrosarcomas classified?
They are classified based on location (intramedullary vs peripheral) and histological grade (conventional, myxoid, clear cell, dedifferentiated).
At what age do chondrosarcomas typically present?
They most commonly occur in individuals over 40 years, with a slight male predominance.
What is the prognostic significance of histological grading in bone tumours?
The histological grade correlates with tumour aggressiveness, metastatic potential, and guides treatment planning.
How does tumour size affect the management of bone tumours?
Larger tumours often indicate a more aggressive disease and may require more extensive surgical resection and adjuvant therapy.
What imaging modalities are used to evaluate bone lesions?
Conventional radiography, CT, MRI, and bone scintigraphy are commonly used to assess bone pathology.
What is the clinical relevance of DEXA scans in metabolic bone disease?
DEXA scans measure bone mineral density, aiding in the diagnosis of conditions like osteomalacia and osteoporosis.
Which laboratory tests are essential in evaluating metabolic bone diseases?
Serum calcium, phosphate, alkaline phosphatase, and vitamin D levels are crucial.
How does measurement of parathyroid hormone (PTH) aid in diagnosing bone pathology?
Elevated PTH levels help diagnose hyperparathyroidism, which leads to increased bone resorption.
What radiological finding is characteristic of osteomalacia in adults?
The presence of Looser’s zones, which are radiolucent bands representing unmineralised osteoid.
What is the significance of subperiosteal new bone formation in osteosarcoma?
It is a radiological sign that supports the diagnosis and indicates aggressive periosteal reaction.
How do bone tumours cause pathological fractures?
Tumour-induced weakening of the bone structure predisposes to fractures even with minimal trauma.
What is the difference between metabolic and neoplastic bone diseases?
Metabolic bone diseases affect bone density and mineralisation diffusely, while neoplastic diseases present as focal lesions.
Why is a multidisciplinary approach essential in bone tumour management?
It ensures accurate diagnosis, optimal surgical planning, and integration of chemotherapy or radiotherapy as needed.
How do intrinsic and extrinsic factors contribute to metabolic bone disorders?
Intrinsic factors include genetic and hormonal influences, while extrinsic factors involve diet, sunlight exposure, and renal function.
What is the overall goal of a comprehensive evaluation in bone pathology?
To accurately diagnose the underlying condition—whether metabolic, infectious, or neoplastic—thus guiding appropriate treatment and improving patient outcomes.
What are the most common tumors found in bone?
The most common tumors found in bone are usually metastatic, not primary.
What are the different types of bone?
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).
What is the structure of bone?
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.
What is the role of the cortex in bone?
The cortex provides support and resistance to weight and lateral trauma.
What does cancellous bone house?
Cancellous bone houses the intertrabecular marrow, where hematopoietic cells are produced.
What happens to bone when it undergoes constant remodeling?
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.
How does immobilization affect bones?
When a bone is fractured and immobilized, the fracture site and the entire limb can be affected due to under-utilization.
How do infections commonly affect bones?
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.
What is a risk factor for bone infections in diabetic patients?
Skin ulcers, particularly due to poor circulation and neuropathy, pose an increased risk for bone infections in diabetic patients.
How do infections in bone differ in children and adults?
In children, long bones are more commonly affected, while in adults, infections often localize in the spine.
Why are hemodialysis patients at higher risk for osteomyelitis?
Hemodialysis patients are at increased risk of osteomyelitis due to contamination.
What happens to bone during an infection?
Osteoclasts attack infected bone, which can lead to abscess formation due to the closed structure of bone limiting the inflammatory response.
What is the risk of infection in bones from contiguous spread?
Contiguous spread can occur from adjacent soft tissue to bone, especially in cases of ulcers or dental infections.
What characterizes osteomalacia and rickets?
Osteomalacia and rickets are characterized by insufficient mineralization, with rickets affecting developing skeletons in children and osteomalacia impacting mature skeletons.
What is osteoporosis, and who is most at risk?
Osteoporosis is a metabolic bone disease characterized by weakened bone density, with the elderly being most at risk, especially when multiple conditions are present.
What causes osteitis fibrosa cystica?
Osteitis fibrosa cystica results from hyperparathyroidism, which leads to the overproduction of parathyroid hormone, causing bone resorption and the creation of lesions.
What is Paget’s disease of bone?
Paget’s disease involves abnormal, disorganized bone remodeling, which can increase the risk of osteosarcomas, particularly in older individuals.
How are benign bone tumors different from malignant bone tumors?
Benign bone tumors do not metastasize but may cause pain or fractures, while malignant tumors, such as osteosarcomas, can spread and are more aggressive.
Which type of bone tumor is most common in young adults?
Osteosarcomas are the most common primary bone tumors in young adults.
At what age do chondrosarcomas typically arise?
Chondrosarcomas typically arise in individuals over 40 years of age.
What condition can chondrosarcomas be associated with?
Chondrosarcomas can be associated with conditions like Ollier’s disease.
