MSK Flashcards
What are the key features of bone remodelling?
It’s a complex balance between bone formation and bone resorption, mediated by several different chemicals
Stages of fracture healing (5)
- Haematoma and inflammation
- Organisation (granulation tissue forms)
- Primary callus response (osteoprogenitor cells become osteoblasts)
- External bridging callus
- Remodelling stage several months after to streamline the callus formation
What material do osteoblasts form?
Osteoid
What happens if a fracture is not properly immobilised?
Cartilage is formed instead of bone
Local (early) complications of fractures (5)
Infection Bleeding Dislocation of joint Skin loss/tissue injury Damage to nerves and vessels
Local (delayed) complications of fractures (5)
Damage to epiphyseal growth plates in children
Avascular necrosis of bone
Osteoarthritis
Delayed union
Non-union (no healing at all)
Systemic complications of fractures (8)
Cardiac shock Fat embolus (within 24-72 hrs) DIC Septic shock Bed sores DVT/PE ARDS (even when no injury near chest) Pneumonia
Factors impairing healing (11)
Age Diabetes Malnutrition Cancer Radiotherapy Infection Ischaemia Soft tissue injury Compound fracture Large fracture gap
Name for infection of bones?
Osteomyelitis
Name for infection of joints?
Spetic arthritis
Why are bone infections hard to treat?
Poor blood supply, hard to get antibiotics to get into the bone
What age group commonly gets acute osteomyelitis
Young children and infants
Important DDx of crying child
X rays are no use in diagnosis, therefore have a high index of suspicion and take blood cultures
Most common organism causing acute osteomyelitis?
Staph aureus
Most common organism causing acute osteomyelitis <4 yr olds?
Haem influenzae
Most common organism causing acute osteomyelitis in sickle cell disease?
Salmonella typhi
Aetiology of acute osteomyelitis?
Typically a haematogenous spread from minor infection eg tooth or toenail
Can be a complication of open fracture, metal prothesis, or in people who are immunosuppressed
What LATE x ray sign can be seen in osteomyelitis?
Sometimes can see a periosteal reaction (fluffiness of periosteum)
Progression of acute osteomyelitis?
Bone abscess can exert pressure within bone causing further necrosis, infection, and destruction
How do you prevent a bone infection?
Urgent debridement of open fractures
Strict aseptic technique in surgery
Use of prophylactic Abx in open fractures and surgery
Which age group gets chronic osteomyelitis?
Usually adults
DOES NOT FOLLOW ON FROM ACUTE OSTEOMYELITIS, DIFFERENT DISEASES
Represents the presence of a smouldering infection which causes bone necrosis and formation.
Causes marked bone deformity
Complications of osteomylitis? (acute and chronic)
Sepsis
Bone deformtiy
Osteoarthritis
Skin sinus formation
Squamous carcinoma (Marjolin’s ulcer)
Systemic amyloid (causes liver and renal failure)
What is Marjolin’s ulcer?
A squamous carcinoma that can form in long standing chronic osteomyelitis
What causes bone/joint TB?
ALWAYS secondary to pulmonary TB (miliary primary TB or reactivation of secondary infection due to immunosuppression)
Where does bone TB arise?
Spine, long bones, hips, knees, small bones of hands and feet
Pathology of bone/joint TB: ____ granulomas are seen with necrosis and ___ multinuclear giant cells with the cell distributed in ___ fashion.
Caseous
Langerhans
Horseshoe
How can bone TB affect the bones grossly?
Can cause kyphosis and scoliosis
Can cross the disc space to involve multiple vertebrae
Psoas abscess
Ankylosis of joints
Systemic amyloid
True/ false: The skeleton is composed of 80% cancellous bone and 20% cortical bone
False, other way round
True/false: The bones in the human skull develop by a process of intramembranous ossification
False, majority of skull forms this way, but the skull base and jaw bone are fromed through endochondrial ossification
True/ false: PTH raised serum Ca by decreasing renal tubular calcium resorption
True, it does this and increases resorption at at the collecting duct
Definition of osteoporosis
Reduction in amount of bone
with loss of microarchitecture
LEADING TO weaken bone and pathological fractures
NB** There is normal mineralisation and normal bone cell activity, there is just not enough bone.
Causes of osteoporosis (7)
Idiopathic, post-menopausal Cushings/ STEROIDS!! Thyrotoxicosis Hypogonadism (lack oestrogen) Hyperparathyoidism Alcohol abuse Scurvy
Risk factors in osteoporosis
Female Age Caucasian Early menopause Family history SMoking Alcohol STEROIDS!!!!! Previous fractures Low dietary calcium Sedentary
Define osteomalacia
Uncommon in Europe
Disease due to poor mineralisation of bone
Caused by both low serum calcium and low serum phosphate
Causes of osteomalacia (different to osteoporosis) (7)
Deficient diet Lack of sun Malabsorption Chronic liver disease Chronic renal disease !!PHENYTOIN!! Hypophosphataemia
How will osteomalacia appear with a von Kossa stain?
Thickening of unmineralised osteoid (purple) on the surface of mineralised one (black)
What is Paget’s disease? What bones are affected?
Due to increased rate of bone remodelling.
Rare under 40 years old
Affects long bones, vertebrae, pelvis and skull
Idiopathic cause but ?slow virus
What is coxa vara in Paget’s disease?
When the neck of the femur shifts from 120 degrees to 90 due to bone remodelling
Difference between Paget’s and osteoporosis on histology?
Paget’s bone is thickened, osteoporosis bone is thinned
In Pagets you also see greatly increased osteoblasts and osteoclasts. The marrow fat is replaced by loose fibrovascular stroma
Presentation of Paget’s?
Mostly asymptomatic
Bone pain
Fractures
Deformity (limb bowing or enlarged skull)
Progressive deafness
Complications of Paget’s disease (5)
Fractures
Osteoarthritis
Nerve compression
SARCOMA due to increased blood supply to bone
?high output heart failure (HF is more likely to be due to another cause)
Structure and function of articular cartilage
Distributes stress forces around joints
Made up of chondrocytes and matrix which does not regenerate
Matrix is made up of GAGs (polysaccharide polymers which absorb water) and collagen
What can cause secondary osteoarthritis?
Previous fractures Metabolic bone disease Hip dislocation Osteonecrosis Joint infection Burnt out RA
Pathogenesis of osteoarthritis
Wear and repari
Change in composition of GAGs, resulting in splitting and loss of cartilage
Reduction in cartilage, but lots of sclerosis and reactive bone around the joint
X ray features of OA
Loss of joint space
Osteophytes
Subchondral cysts
Sclerosis
Pathology of RA (complex, don’t rote learn)
Auto-immune disease
Rhematoid factor IgM reacts with Fc part of sensitised IgG forming an IMMUNE COMPLEX
This activates complement system and interleukins 1 and 6 are released, as well as TNFa.
Increased incidence with HLA-Dr4
Who most commonly gets RA?
Females>males 4:1
20-50 years
Does synovitis or arthrits occur first in RA?
Synovitis first (opposite to OA)
Inflamed synovium spreads over articular cartilage and starves it of nutrition
Leads to destruction of cartilage- ARTHRITIS
Pathological features found in RA
Synovial hyperplasia (thrown up into papillary folds)
Chronic inflammation
Lyphocyte aggregates
Lymphoid follicles
Subcutanous rheumatoid nodules (acellular necrotic collagen granuloma)
Systemic effects casued by RA (5)
Vasculitis Pericarditis Lung fibrosis Infection risk Chronic systemic amyloid
Another name for chondrocalcinosis?
Pseudogout
What cuases gout?
Increased sodium urate which comes from breakdown of DNA
If patient is dehydrated, there is a reduction in solvent and this increases urate
Urate crystals in soft tissues causes inflammation
Causes of gout
Genetics: purine metobolism
Renal failure
THIAZIDE DIURETICS
Increased cell turnover eg form leukaemia etc leading to increased DNA breakdown
Histological feature of chronic gout?
Giant cells
What diseases are sero-negative arthropathies?
Ankylosing spondylitis
Psoriatic arthritis
Reiter’s disease
IBD arthritis
They are all NEGATIVE for rheumatoid factor
Pathology of sero-negative arthropathies
ENTHESITIS (inflammation where a ligament or tendon is attached to bone)
Results in secondary ossification and spondylitis.
Can get large joint synovitis later on
What are syndesmophytes?
Parallel arrays of bone that cross the intervertebral discs and stiffen the spine
Seen in seronegative arthropathies eg AS, psoriatic arthritis
Where do metastatic bone tumours occur?
VERY RARE TO OCCUR DISTAL TO KNEE
Skull, ribs, pelvis, spine, humerus, femur
What are sclerotic bone metastases?
Also called osteoblastic
Induce osteoblast activity
Spread characteristically from prostate and breast
Most common primary sites for metastases to bone?
Lung, thyroid, breast, kidney, prostate
Benign bone forming tumours (3)
Osteoma
Osteoid osteoma
Osteoblastoma
Malignant bone forming tumour (1)
Osteosarcoma
What is an osteoma?
Benign bone forming tumour
Arises on bone surface
Most common in 40s-60w
M=F
Composed of dense cortical bone
Where do osteomas occur?
Bone surfaces
Craniofacial skeleton most common
What is Gardner syndrome?
Multiple osteomas
Increased risk of intestinal adenocarcinoma
Treatment of osteoma
Observation or simple excision
No reoccurrence usually
What is an Osteoid Osteoma?
Benign bone forming tumour characterised by:
- Small size
- Classic pain pattern worse at night time and relieved by NSAIDS
Occurs in teens and YA males
Treated with radio frequency ablation
Where do osteoid ostemoas occur?
Most common site is proximal femur
Can occur in small bones of hands and feet or vertebral column
Tx for osteoid osteoma
Radiofrequency ablation
What is an osteoblastoma?
Benign bone forming lesion
Similar histology to osteoid osteoma but is >2cm
Occurs in teens and YAs
M>F
Present with pain, swelling, and spinal tumours can cause neurologic symptoms
Osteoblastoma location
**Posterior part of vertebra (not in the body) and sacrum
Also feet and hands
Imaging of osteoblastoma
Expansile tumour with circumscribed margins which appear both sclerotic and lytic
Treatment of osteoblastoma
Surgical: Curettage or en-bloc resection
Excellent prognosis but recurrence rate of 20%
What is the most common primary malignant bone tumour? (excluding haematology)
Osteosarcoma
Age group affected by osteosarcoma?
10-20 year olds :(
Second peak >50s
M>F
Presentation of osteosarcoma?
Enlarging painful mass
Minority have pathological fracture
Causes of osteosarcoma
Mostly idiopathic
Some arise in diseased bone:
- Paget’s
- Radiation
- Chemo
- Trauma
Foreign body implants
Genetics: Hereditary retinoblastoma or Li-Fraumeni syndrome
Osteosarcoma locations
50% in knee region
15% humerous
Also femur, tibia, humerus
X ray appearance of osteosarcoma
Ill defined
Both lytic and sclerotic
Radiodensity in soft tissues in keeping with soft tissue extension of tumour
What is Codman’s triangle on osteosarcoma MRI imaging?
Reactive bone deposited next to the tumour, usually triangular in shape
Osteosarcoma treatment
Preoperative chemo (efficacy is determined by histology assessment of tumour necrosis)
Surgery: complete excision or amputation
Radiotherapy if tumour is too large to resect
Benign cartilage tumours (2)
Osteochondroma
Enchondroma
Malignant cartilage tumour
Chondrosarcoma
What is an osteochondroma
Most common primary bone tumour.
Originates in growth plate region. Caused by inactivating mutations of EXT genes
Most patients are in their 20s
M>F
Most are asymptomatic
How do osteochondormas present? Solitary vs multiple
Can occur sporadically as solitary lesion
Multiple lesions in MULTIPLE HEREDITARY OSTEOCHONDROMATOSIS
Occur in knee, distal femur and proximal tibia
Histology of osteochondroma: Characteristic ____ shape with surface _____ cap and an underlying bony stalk
Mushroom
Cartilaginous
Treatment for osteochondroma
Growth ceases at puberty
Treated by excision
Malignant transformation is very uncommon
What is an enchondroma?
Benign chondrocyte tumour that arises in medulla
Unknown cause
60% in hands and feet
Majority are asymptomatic
Presents in 30s-40s
Treatment of enchondroma
Slow limited growth
Most require no treatment
If painful: curettage, then packing with bone graft or cement
Multiple lesions occr in Ollier disease and Maffucci syndrome
What is a chondrosarcoma?
Malignant cartilage producing tumour
idiopathic
Adults in 50s-70s, M>F
Painful enlarging mass, may fracture
**Where do chondrosarcomas occur?
Pelvis
Proximal femur
RARE to be in hands or feets
Treatment of chondrosarcoma
Surgery: Aggressive curettage, wide local resection
Radiotherapy if difficult to resect
Prognosis of chondrosarcoma
Grade 1: 85% 5 year survival
Grade 2 and 3: 50% 5 year survival
What is Fibrous Dysplasia?
BENIGN fibro-osseus bone neoplasm
Bone lesions develop in childhood and are asymptomatic.
Often in one bone only
Associated with McCune Albright syndrome and Mazabraud syndromes
Affects ribs, femur, tibia, jaw, skull
Which bone neoplasm is associate with the bone resembling Chinese figures on low power histology?
Fibrous dysplasia
Treatment of fibrous dysplasia
Benign
Treatment if painful
What is a Giant Cell TUmour of Bone?
Benign but locally aggressive tumour
Occurs in adults 30s to 50s
FEMALES OVER MALES (unusual)
Occurs in knee, pain and swelling
What does RANK ligand do in Giant Cell tumour?
Induces formation of osteoclast type giant cells.
Activated by mononuclear cells of the tumour
Treatment for Giant Cell Tumour?
Surgery: Curettage or en-bloc resection
RANK ligand inhibitor
Radiation
Local recurrance rate is 25%
What is Ewing’s sarcoma? How does it present? Who is affected?
Malignancy small round cell sarcoma
Most patients between 10-15 yrs
M>F
Painful enlarging mass, mimicing infection
Patients have FEVER and raised WCCs!!
Where does Ewing’s sarcoma occur?
Mostly in ilium and femur
X ray appearance of Ewing’s
Ill defined lytic lesion
with periosteal reaction causing new bone formation
Which bone lesion is assocaited with a t(11:22)(q24:q12) translocation?
Ewing’s sarcoma
Can be detected using FISH or PCR
Treament of Ewing’s sarcoma
Combo of chemo and surgery:
-pre op chemo (histology, tumour necrosis >90% is good response)
Radiotherapy
50% are cured long term
