MSK Revision 1

Question 1

[] is the most common causative pathogen in osteomyelitis.

Answer 1

Staph aureus is the most common causative pathogen in osteomyelitis.

Question 2

What are the two types of osteomyelitis? [2]

State common causes for each

Answer 2

There are two types of osteomyelitis as defined by their source: haematogenous and nonhaematogenous.

Haematogenous:
* Indwelling intravascular catheter (e.g. Hickman line)
* Haemodialysis
* Endocarditis
* IV drug use

Non-haematogenous:
* Skin ulcers
* Trauma
* Surgery (especially when foreign material is placed)
* Animal / insect bites

Question 3

Which bones are more commonly affected by haematogenous vs non-haematogenous osteomyelitis? [2]

Answer 3

Haematogenous:
- axial skeleton, primarily the vertebral bones
- sternum and pelvis

Non-Haematogenous:
- ares of trauma / surgery

Question 4

Clinical features of acute [3] and chronic osteomyelitis [3] ?

Answer 4

Acute osteomyelitis:
- Pain is the most common symptom
- Warm and erythema
- Systemic symptoms

Chronic osteomyelitis:
- Tends to present only with local symptoms such as swelling, erythema and pain
- Systemic symptoms such as fever are often ABSENT
- Often secondary to DM vascular injury - diabetics with ulcers >2cm2 are very likely to have osteomyelitis, even if no bone is visible
- A draining sinus tract may be seen - this is pathognomonic of osteomyelitis

-

Question 5

In patients with a history of intravenous drug use, what organism is the most common cause for osteomyelitis?

Salmonella spp.

S. aureus

P. aeruginosa

E. coli

Answer 5

In patients with a history of intravenous drug use, what organism is the most common cause for osteomyelitis?

Salmonella spp.

S. aureus

P. aeruginosa

E. coli

Question 6

Investigations for osteomyeltis? [+]

Answer 6

Serology:
- Acute = raised WCC / CRP
- Chronic = often has normal WCC
- Blood cultures are positive in around half of cases

X-ray:
- Acute = first two weeks of infection may show normal
- Soft tissue swelling, osteopaenia (bone thinning), bone destruction, periosteal reaction (changes to the surface of the bone), endosteal scalloping and new bone apposition

MRI:
- Best imaging for dx
- Sequestrum: Refers to a dead piece of devitalised bone that has been separated (i.e. sequestered) due to necrosis from the surrounding bone.
- Involucrum: New growth of periosteal bone around a sequestrum.
- Cloaca: An opening in an involuvcrum that allows the internal necrotic bone and pus to discharge out.

Question 7

Label A-C

Answer 7

Sequestrum: Refers to a dead piece of devitalised bone that has been separated (i.e. sequestered) due to necrosis from the surrounding bone.

Involucrum: New growth of periosteal bone around a sequestrum.

Cloaca: An opening in an involuvcrum that allows the internal necrotic bone and pus to discharge out.

Question 8

Describe the difference between sequestrum vs involucrum? [1]

Answer 8

A sequestrum is the necrotic bone which has become walled off from its blood supply and can present as a nidus for chronic osteomyelitis.

An involucrum is a layer of new bone growth outside existing bone seen in osteomyelitis.

Question 9

What is A? [1]

Answer 9

Sequestrum

Question 10

Describe the treatment for osteomyelitis [3]

Answer 10

Antibiotics +/- surgical debridement forms the mainstay of management.

Abx:
- Should be held until bone cultures are completed
- Guided by microbiology
- BNF: flucloxacillin for 6 weeks; possibly with rifampicin or fusidic acid added for the first 2 weeks
- Chronic osteomyelitis usually requires 3 months or more of antibiotics.
- Clindamycin in penicillin allergy
- Vancomycin or teicoplanin when treating MRSA

Surgery:
- More common in non-haem. spread
- infected necrotic bone must be removed
- Irrigation & debridement - sequestrum must be eliminated from the body, or infection is likely to recur; replace dead bone and scar tissue with vascularized tissue

Question 11

What are the indications for surgery in osteomyelitis? [3]

Answer 11

• Failure to respond to antibiotic therapy
• Formation of discrete abscess
• Neurological deficit (vertebral osteomyelitis)

Question 12

Answer 12

S. aureus

Question 13

Answer 13

Salmonella

Question 14

Septic arthritis can be caused by direct inoculation of the joint or by haematogenous spread of bacteria from another site. The most common causative organism in adults is [].

Answer 14

Septic arthritis can be caused by direct inoculation of the joint or by haematogenous spread of bacteria from another site. The most common causative organism in adults is Staphylococcus aureus.

Question 15

Describt the different causes of septic arthritis

Answer 15

When septic arthritis is caused by haematogenous spread it may be a result of:
Bacterial migration from a distant site
* Abscesses and wounds
* Septicaemia

Disseminated infection
* Gonorrhoea

OR

When septic arthritis is caused by direct inoculation it may be a result of:
Iatrogenic procedures
* Joint injections (e.g. steroid injections)
* Joint arthrocentesis
* Athroscopy

Traumatic injuries
* Infected wounds around the joint
* Penetrating injuries from foreign objects

Question 16

Describe investigations for septic arthritis? [2]

Answer 16

Joint aspiration is key and should be obtained prior to antibiotics (whenever possible):
- Also decompresses joint space
- synovial fluid appearance: often yellow/green and turbid on aspiration compared to uninfected fluid which is clear and usually colourless.
- Cultures of synovial fluid in cases of gonococcal septic arthritis yield positive results in only 25% of cases.
- Synovial fluid WCC: is often raised with neutrophil predominance. WBC: >50 000 cells/mm3 with Neutrophils: >75 %

Question 17

The Kocher criteria for the diagnosis of septic arthritis is [4]

Answer 17

The Kocher criteria for the diagnosis of septic arthritis:
* fever >38.5 degrees C
* non-weight bearing
* raised ESR
* raised WCC

Question 18

Describe the management plan for septic arthritis

Answer 18

First: rule out sepsis

Empirical IV antibiotics should be given until the sensitivities are known. Often following are given:
* Flucloxacillin (often first-line)
* Clindamycin (penicillin allergy)
* Vancomycin (if MRSA is suspected)
* Ceftriaxone if gonorrhoea

Antibiotics are typically continued IV for 2 weeks before switching to PO if the patient is improving.

Question 19

A patient presents with ?osteomyelitis. An MRI is performed.

What does the arrow point at? [1]

Answer 19

involucrum: formation of new bone around an area of bony necrosis

Question 20

A patient presents with ?osteomyelitis. An MRI is performed.

What does the arrow point at? [1]

Answer 20

sequestrum: devitalized bone that serves as a nidus for infection

Question 21

Describe the positions of a sequestrum vs a involucrum [2]

Answer 21

A sequestrum is the necrotic bone which has become walled off from its blood supply and can present as a nidus for chronic osteomyelitis.

An involucrum is a layer of new bone growth outside existing bone seen in osteomyelitis.

Question 22

Clinical features of osteoporosis? [2]

Answer 22

Pathological or fragility fractures:
- Vertebral compression fractures
- Appendicular fractures - proximal femur or distal radius following a fall: Neck of femur and Colles fractures

Question 23

State causes of secondary osteoporosis [+]

Answer 23

Endocrine:
- DM
- Cushings
- Hyperparathyroidism
- Hyperthyroidism
- Low testosterone

Malabsorptive
- IBD
- Coeliac

COPD
CKD
Chronic liver disease

Question 24

How would you differentiate osteoporosis and osteomalacia?
- presentation [2]
- investigations [1]

Answer 24

osteomalacia may cause generalised bone pain, tenderness and myopathy
- low Ca and PO4 serum; high ALP and PTH

Question 25

Describe the treatment algorithm for osteoporosis [4]

Answer 25

First line: Bisphosphonates
- oral alendronate or risedronate weekly oral
- zoledronic acid - yearly infusion
- MOA: interfering with the way osteoclasts attach to bone, reducing their activity and the reabsorption of bone.

Second line: Denosumab:
- monoclonal antibody agaisnt RANK ligand, inhibits osteoclasts
- SC every 6 months
- can be used for osteoporosis in post-menopausal women or OP In men
- can be used for patients on steroids

Raloxifene
- Raloxifene is approved for the treatment and prevention of osteoporosis in postmenopausal women
- selective oestrogen receptor modulator (SERM)

HRT: unopposed oestrogen or O&P
- Prevention of fracture in women at high risk. It is normally reserved for use in younger women as the side effect profile is better.

Clinical scenarios
- if a patient is deemed high-risk based on a QFracture or FRAX score they should have a DEXA scan to assess bone mineral density (BMD): if T-score of - 2.5 SD or below start bisphosphinates
- A postmenopausal woman, or a man age ≥50 has a symptomatic osteoporotic vertebral fracture: above
start treatment straight away - oral bisphosphonates are used first-line e.g. alendronate or risedronate
- following a fragility fracture in women ≥ 75 years, a DEXA scan is not necessary to diagnose osteoporosis and hence commence a bisphosphonate

Question 26

Which groups are bisphosphinates CI in? [3]

Answer 26

Severe renal impairment (renally excreted)
Hypocalcaemia
Upper GI disorders

Smokers and dental disease should be cautioned because of jaw necrosis risk

Question 27

In which patient groups is raloxifene CI In? [1]

Answer 27

history of venous thromboembolism or if a patient has prolonged immobilisation due to risk of VTE

Question 28

Name three side effects of raloxifene [3]

Answer 28

Side effects include hot flushes, vaginal dryness and leg cramps.

NB: Raloxifene is a selective oestrogen receptor modulato

Question 29

Name two side effects of denosumab [2]

In which patient populations is it CI In? [3]

Answer 29

Side effects include cellulitis and hypocalcaemia

CI in hypocalcaemia and hypersensitivity and avoided in pregnancy.

Question 30

Answer 30

heparin

Question 31

Answer 31

Normal serum calcium, normal serum phosphate, normal ALP and normal PTH

Question 32

Answer 32

SERM

Question 33

Name the clinical presentation of the hand signs of OA [5]

Answer 33

Heberden’s nodes (in the DIP joints)
Bouchard’s nodes (in the PIP joints)
Squaring at the base of the thumb (CMC joint)
Weak grip
Reduced range of motion

Question 34

Why is the CMC so likely to get OA? [1]

Where may pain from this joint present? [1]

Answer 34

The carpometacarpal joint at the base of the thumb is a saddle joint, with the metacarpal bone sitting on the trapezius bone, using it like a saddle. It gets a lot of use and is very prone to wear.

TOM TIP: Patients may present with referred pain, particularly in the adjacent joints. For example, consider osteoarthritis in the hip in patients presenting with lower back or knee pain.

Question 35

NICE CG 226: Osteoarthritis in over 16s: diagnosis and management (2022) advise a clinical diagnosis (without imaging) can be made when a patient: [3]

Answer 35

• Is 45 or over and
• Has activity-related joint pain and
• Has either no morning joint-related stiffness or morning stiffness that lasts no longer than 30 minutes.

Question 36

Describe the medical management of OA

Answer 36

First line:
- NSAIDS (topical); w/ PPI. Hand: topical; Knee - topical; Hip - oral

Second line:
- oral NSAIDS

Third line - Intra-articular injections:
- corticosteroid injections for short-term pain relief in patients with moderate-to-severe knee OA and signs of local inflammation
- Hyaluronic acid (HA)

Surgery:
- Hip or knee replacement (Arthroplasty)
- Osteotomy (realignment)

NB: NICE guidance (NG 226) advise against hyaluronan injections (due to lack of evidence of efficacy), though some clinicians do use them, typically the patient must buy the medication privately.

Question 37

Describe the clinical presentation of osteomalacia [+]

Answer 37

Musculoskeletal Symptoms:
- Bone pain: Diffuse, poorly localized pain involving the lower back, hips, pelvis, and lower extremities is a common presenting symptom. Pain is typically exacerbated by weight-bearing activities and may be relieved with rest.
- Muscle weakness - especially proximal muscle weakness
- Joint pain

Hypocalcaemia:
- Paresthesia: Patients may complain of numbness or tingling sensations in their extremities due to hypocalcemia-induced neuromuscular excitability.
- Tetany: Severe hypocalcemia can cause carpopedal spasm, Chvostek’s sign (facial muscle twitching), or Trousseau’s sign (carpopedal spasm induced by inflating a blood pressure cuff).

Extra-skeletal Manifestations
* Dental abnormalities: Defective dentin formation may lead to dental caries, enamel hypoplasia, and periodontal disease.
* Nonspecific symptoms: Fatigue, anorexia, and weight loss may be present in patients with osteomalacia.

Question 38

Describe the treatment for osteomalacia [1]

Answer 38

Colecalciferol (vitamin D₃):
- Give a loading and maintenence dose

Question 39

Answer 39

Phenytoin

Question 40

Answer 40

Type 2 renal tubular acidosis

Question 41

Answer 41

Fanconi

Question 42

Define Paget’s disease of the bone [1]

Describe the basic pathophysiology [3]

Answer 42

Paget’s disease is a disease of increased but uncontrolled bone turnover. The excessive turnover is not coordinated leading to areas of patchy sclerosis and lysis

Pathophysiology:
* Increased osteoclastic bone resorption (larger than normal osteoclasts)
* Increased osteoblastic response; but in an architecturally disorganised manner
* Get areas of alernating sclerotic and lytic phases

Question 43

Clinical features of Pagets? [4]

Answer 43

Bone pain
Bone deformity
Fractures - bowing of tibia; bossing of skull
Hearing loss

Question 44

Describe the investigations used to dx Paget’s [3]

Answer 44

Serology:
- Raised ALP
- Ca and P normal

Imaging:
- Osteolysis or mixed sclerosis / lytic lesions
- Skull: thickened vault and cotton wool appearance
- V-shaped osteolytic defects in the long bones

Question 45

Management of Pagets? [+]

Answer 45

First line: Bisphosphinates
- Alendronic acid: This is often the first choice due to its favourable side effect profile and cost-effectiveness. It is typically given orally.
- Pamidronate and Zoledronic acid: These intravenous bisphosphonates may be used in patients who cannot tolerate oral bisphosphonates

Analgesics:
- Over-the-counter analgesics like paracetamol may be sufficient for some patients, but others may require stronger analgesics such as opioids.
- Nonsteroidal anti-inflammatory drugs (NSAIDs) may be beneficial for those with associated inflammatory arthritis.

Surgery:
- Pathological fractures: These may require surgical fixation to allow for proper healing and to reduce pain.
- Severe osteoarthritis or joint destruction: Joint replacement surgery may be considered in patients with severe joint damage.
- Neurological complications: For patients with nerve compression syndromes, such as spinal stenosis, decompressive surgery may be required.

Question 46

Answer 46

normal serum calcium, normal serum phosphate, raised ALP and normal PTH

Question 47

For the following, state if you give oral or topical NSAIDs as first line treatment for OA [3]:

Hand
Knee
Hip

Answer 47

Hand: topical
Knee: topical
Hip: oral (& PPI)

Question 48

How is zoledronate administered? [1]

Answer 48

Intravenously, once a year

Question 49

What are the non-musculoskeletal features of Paget’s disease? [3]

Answer 49

Skull enlargement can lead to complications such as hearing loss (most commonly), thought to be due to cochlear damage. They may also develop tinnitus because of nerve compression.

Rarely patients can develop osteosarcoma which might be suspected if their pain levels suddenly and significantly worsens.

From a cardiac perspective, patients are more likely to develop congestive heart failure, particularly if more than 40% of their skeleton is affected by the condition.

Question 50

1.

What is the commonest clinical feature in Paget’s disease?

Answer 50

Asymptomatic in 90%

Question 51

What is the rare malignant complication of Paget’s disease? [1]

Answer 51

Osteosarcoma