Flashcards in Miscellaneous Deck (37):
Describe the vascular supply of mature bone.
Has 3 major sets of blood vessels
- nutrient artery and vein, metaphyseal vessels, periosteal vessels
Define: diaphysis, epiphysis, metaphysis
Diaphysis: tubular shaft
Epiphysis: expanded end area
Metaphysis: connects diaphysis and epiphysis
Describe the neural innervation of bone.
Sensory nerves innervate the endosteum
Vasomotor nerves innervate the bone cavity and epiphysis
What is intramembranous ossification and what type of bones are formed?
Osteoblasts differentiate within a mesenchymal or fibrous connective tissue
Form 'dermal bones' such as flat bones of the skull, the mandible and clavicle
What is endochondral ossification?
Bones form from hyaline cartilage
Name 3 benign and 1 malignant bone-forming tumour
Benign: Osteoma, otseoid osteoma, osteoblastoma
Name 3 benign and 1 malignant cartilage-forming tumour
Benign: Chondroma, osteochondroma, chondroblastoma
List 2 malignant marrow tumours
List 3 benign and 3 malignant connective tissue tumours
Benign: Fibroma, fibrous histiocytoma, lipoma
Malignant: Fibrosarcoma, malignant fibrous histiocytoma, liposarcoma
In staging tumours, what do the terms 'low-grade' and 'high-grade' mean?
Low-grade - moderately aggressive + take a long time to metastasise
High-grade - usually very aggressive and metastasise early
How are malignant bone tumours staged?
Stage I: all low-grade sarcomas
Stage II: histologically high-grade lesions
Stage III: sarcomas which have metastasised
Can be further divided into Type A (intracompartmental) or Type B (extracompartmental)
In describing benign MSK tumours, what does 'latent' mean? (3)
Well-defined margin. Grows slowly and then stops. Remains static/heals spontaneously
In describing benign MSK tumours, what does 'active' mean? (3)
Progressive growth limited by natural barriers. Not self-limiting. Tendency to recur
In describing benign MSK tumours, what does 'aggressive' mean?
Growth not limited by natural barriers
What is a brown tumour?
Bone lesion that arises in setting of excess osteoclast activity e.g. hyperparathyroidism, and which is radiolucent on X-ray. Mainly affects phalanges of fingers, long bones
In which age groups is osteosarcoma most frequently diagnosed?
2nd decade or 10-30
Describe 3 radiographic findings found in osteosarcoma
1. Codman's triangle - manifestation of periosteal reaction - partial ossified periosteum lifted off cortex by neoplastic tissue
2. Sunburst - manifestation of periosteal reaction - tumour extension into periosteum
3. Destructive lesion in metaphysis, may cross epiphyseal plate
What is Ewing's Sarcoma?
Tumour believed to arise from endothelial cells in bone marrow, usu. in tubular bone e.g. fibula/tibia/clavicle. Occurs in those 5 - 20 years old
In which age group does multiple myeloma usually occur?
90% occur in people over than 40 years, M:F = 2:1
How should multiple myeloma be investigated? (3)
1. Bloodwork - FBC (anaemia), increased ESR, urea and creatinine, and increased calcium
2. Serum and urine electrophoresis - IgG or IgA sometimes seen in latter, Bence Jones protein sometimes in former
3. X-rays: lytic, 'punched-out' lesions. CT/MRI may be used to detect lesions not seen on XR
What are the diagnostic criteria for multiple myeloma? (4)
1. Monoclonal protein band in serum or urine electrophoresis
2. Plasma cells increased on marrow biopsy
3. Evidence of end-organ damage: hypercalcaemia, renal insufficiency, anaemia
4. Bone lesions - skeletal survey - X-ray of chest, all of spine, skull
What are the signs of hypercalcaemia?
"Bones, stones, moans and psychic groans"
Bones: bone pain
Moans: abdominal pain (also vomiting, constipation)
Groans: depression, confusion
List the 5 common tumours that metastasise to bone
Occurrence of osteolytic vs osteoblastic lesions in bone metastases
Bone metastases usually lytic - pathological fractures are therefore very common.
Prostate cancer occasionally osteoblastic
What are the common sites of bone metastases? (4)
3. Proximal half of femur
Describe Mirel's Criteria for Impending Fracture Risk and prophylactic internal fixation
4 variables: site, pain, lesion, size
1 - upper arm, 2 - lower extremity, 3- trochanter
1 - mild, 2 - moderate, 3 - severe
1 - blastic, 2- mixed, 3 - lytic
1 - less than 1/3, 2 - 1/3 to 2/3 diameter, 3 - more than 2/3 diameter
A score greater than 8 suggests prophylactic nailing
How does a bone scan work? (Lay explanation) (3)
1. Bone scans use radionuclides to detect areas of the bone which are growing or being repaired. A radionuclide (sometimes called a radioisotope or isotope) is a chemical which emits a type of radioactivity called gamma rays. A tiny amount of radionuclide is put into the body, usually by an injection into a vein. (Sometimes it is breathed in or swallowed, depending on the test.)
2. Cells which are most 'active' in the target tissue or organ will take up more of the radionuclide. So, active parts of the tissue will emit more gamma rays than less active or inactive parts.
3. The gamma rays which are emitted from inside the body are detected by the gamma camera. The rays are then converted into an electrical signal and sent to a computer. The computer builds a picture by converting the differing intensities of radioactivity emitted into different colours or shades of grey.
Which organisms can cause septic arthritis?
Most commonly caused by Staph aureus in adults
Consider gonorrhoea in sexually active adults
How should septic arthritis be investigated? (3)
1. Blood: FBE, ESR, CRP, blood cultures
2. X-ray: to rule out fracture, tumour, metabolic bone disease
3. Joint aspirate
How is septic arthritis treated?
1. IV antibiotics - usu. fluclox (empiric therapy for S. aureus)
2. For small joints - needle aspiration is therapeutic
3. For major joints: urgent decompression and surgical drainage
What is the most common organism in osteomyelitis?
How is osteomyelitis classified?
Acute (less than 14 days) vs chronic
Children vs adults
Which bones are commonly affected in children vs adults in osteomyelitis?
Children: long bones
How is osteomyelitis investigated? (3)
1. Blood: FBE, ESR/CRP, blood culture
2. +/- biopsy
3. Imaging: X-ray +/- bone scan +/- MRI
What are the X-ray findings seen in osteomyelitis? (3)
1. Soft tissue swelling
2. Lytic bone destruction - generally not seen on plain films until 10-12d after onset of infection
3. Periosteal reaction (formation of new bone, esp. in response to #)
How is osteomyelitis managed? (2)
1. IV AB therapy:empiric - in long bones: fluclox, in vertebral: ceftriaxone. Adjust after results of blood cultures, serial CRP can be used to monitor response to therapy
2. Surgical debridement