Orthopaedics

Question 1

Embryological development of the musculoskeletal system begins at what week of gestation?

Answer 1

Approx. the 4th week

Question 2

Activations of mesenchymal cells in what embryological structure is responsible for the development of the musculoskeletal system?

Answer 2

Somatic lateral mesoderm

Question 3

What genes are responsible for regulating the musculoskeletal system?

Answer 3

Homeobox genes

Question 4

At what days gestation do the upper and lower limb buds develop?

Answer 4

Upper limb buds - day 24

Lower limb buds - day 25-26

Question 5

What are limb buds?

Answer 5

Elongated proliferations of mesenchyme

Question 6

What structure forms at the apex of each limb bud? What is their function?

Answer 6

Ectoderm thickens to form the apical ectodermal ridge (AER) which exerts an inductive influence on the limb mesenchyme causing the growth of blood vessels/cartilage/bone etc.

Question 7

Outline the process of the embryological formation of hands and feet

Answer 7

Distal ends of the limb buds flatten into paddle-like plates which condense into digital rays for hands and feet by six and seven weeks gestation respectively.

Question 8

What process causes separation of digital rays to make individual fingers and toes?

Answer 8

Programmed cell death (apoptosis) mediated by morphogenetic proteins

Question 9

What defect may arise from the incorrect separation of digits in utero?

Answer 9

Syndactyly (simple cutaneous or complicated osseous)

Question 10

Cartilaginous precursors to the bones of the limbs develop from what embryological structure?

Answer 10

Mesoderm

Question 11

What areas of proto-bone develop between 8 and 12 weeks gestation? What causes their development?

Answer 11

Primary centres of ossification appear in response to growth factors

Question 12

What type of calcification occurs for all limb bones? What is the one exception?

Answer 12

Endochondral ossification for all limb bones except the clavicle (membranous ossification instead)

Question 13

Both limbs rotate in utero during the development of the musculoskeletal system.

Outline rotation of both upper and lower limbs respectively

Answer 13

Upper limbs - rotate laterally - extensors are on lateral/posterior surface (remember the thumb is lateral)

Lower limbs - rotate medially - rotate medially so extensors are on anterior surfaces (remember big toe is medial)

Question 14

Birth defects of the limbs can be either hereditary or teratogenic in nature. What is the word used to describe a total lack of limbs?

Answer 14

Amelia

Question 15

What is meant by the term meromelia?

Answer 15

Partial lack of limbs

Question 16

What is meant by the term phocomelia?

Answer 16

Partial loss of long bones

Question 17

What is meant by the term micromelia?

Answer 17

All parts of limbs present but small

Question 18

What teratogen is associated with meromelia?

Answer 18

Thalidomide

Question 19

What is the medical term of a congenital club-foot?

Answer 19

Talipes equinovarus

Question 20

Describe congenital clubfoot

Answer 20

Soles of feet are turned medially and the foot is inverted

Question 21

List different types of bone-forming tumours

Answer 21

Benign - osteoid osteoma, osteoblastoma

Malignancy - osteosarcoma

Question 22

List different types of cartilage-forming tumours

Answer 22

Benign - enchondroma, osteochondroma

Malignant - Chondrosarcoma

Question 23

List different types of fibrous tissue tumours

Answer 23

Benign - fibroma

Malignant - fibrosarcoma, malignant fibrous histiocytoma (MFH)

Question 24

List different types of vascular tissue tumours

Answer 24

Benign - haemangioma, aneurysmal bone cyst

Malignant - angiosarcoma

Question 25

List different types of fatty tissue tumours

Answer 25

Benign - lipoma | Malignant - liposarcoma

Question 26

List different types of bone marrow tissue tumours

Answer 26

Malignant - Ewing's sarcoma, lymphoma, myeloma

Question 27

What is the commonest primary malignant bone tumour in younger patients?

Answer 27

Osteosarcoma

Question 28

What is the commonest primary malignant bone tumour in older patients?

Answer 28

Myeloma (not strictly a bone malignancy but it is a major diagnostic aspect of the disease)

Question 29

List some investigation which may be useful in the diagnosis and monitoring of bone tumours

Answer 29

``` Plain X-Rays CT Scan Isotope bone scan MRI PET Scan ```

Question 30

Outline the clinical features of a bone tumour

Answer 30

``` Pain (worse at night) Loss of function (limp/reduced movement/stiff back) Swelling Pathological fracture Joint effusion Deformity Neurovascular effects ```

Question 31

What is the triad of pathophysiology of osteoarthritis?

Answer 31

Tear, flare and repair A lifetime of wear (and injuries) cause inflammation and subchondral changes lead to activation of the repair process - constant cycles of repair lead to destruction of cartilage

Question 32

What are the diagnostic criteria for osteoarthritis?

Answer 32

Typically aged +45 Activity related joint pain No related morning stiffness/stiffness that lasts <30 mins Pay attention to a history of trauma, prolonged morning stiffness, rapid deterioration or systemic symptoms as this may point to a more serious underlying diagnosis

Question 33

What are some differential diagnoses for osteoarthritis?

Answer 33

Gout Inflammatory arthritides (rheumatoid, psoriatic etc.) Septic arthritis Malignancy

Question 34

What is the treatment escalation plan for osteoarthritis?

Answer 34

First-line - non-pharmacological treatments Second line - pharmacological Third line - surgical intervention

Question 35

What non-pharmacological treatments are available or osteoarthritis?

Answer 35

Thermotherapy, electrotherapy, aids and devices, manual therapy

Question 36

What pharmacological treatments are available or osteoarthritis?

Answer 36

``` Oral analgesia (paracetamol, NSAIDs) Topical treatments (NSAIDs, capsaicin cream) ```

Question 37

What age demographic is most likely to develop osteomyelitis?

Answer 37

Mostly children with boys being more affected than girls

Question 38

What routes of infection may lead to osteomyelitis?

Answer 38

Hematogenous spread Local spread - from a contiguous site of infection e.g. trauma (open fracture), surgery (ORIF) or joint replacement

Question 39

What are the most likely causes of osteomyelitis in infants, children and adults respectively?

Answer 39

Infants - infected umbilical cord Children - boils, tonsilitis, skin abrasions Adults - UTI, arterial lines

Question 40

What organisms are most likely to be the cause of osteomyelitis in infants?

Answer 40

Staph aureus Group B strep E. Coli

Question 41

What organisms are most likely to be the cause of osteomyelitis in older children?

Answer 41

Staph aureus Strep pyogenes H influenzae

Question 42

What organisms are most likely to be the cause of osteomyelitis in adults?

Answer 42

Staph aureus Coagulase -ve staph Mycobacterium Pseudomonas aeroginosa

Question 43

What organism(s) are most likely the cause of osteomyelitis in diabetic foot/pressure sore patients?

Answer 43

Mixed infection (including anaerobes)

Question 44

What organism(s) are most likely the cause of osteomyelitis in sickle cell disease patients?

Answer 44

Salmonella spp.

Question 45

What organism(s) are most likely the cause of osteomyelitis in fishermen or filleters?

Answer 45

Mycobacterium manrium

Question 46

What organism(s) are most likely the cause of osteomyelitis in HIV/AIDS patients?

Answer 46

Candida

Question 47

What anatomical sites are most commonly affected by osteomyelitis?

Answer 47

Long bones (particularly distal femur, proximal tibia or proximal humerus) Joints with intra-articular metaphysis (hip, elbow (radial head)

Question 48

Outline the pathophysiology of osteomyelitis

Answer 48

Acute inflammation at the metaphysis/suppuration causing vascular stasis. Release of pressure