2. MSK (Pagets, Tendon ultrasound, Arthrogram)

Question 1

Pagets - epidemiology/pathology (4)

Answer 1

Common (affects 4% over 40 and 10% over 80).
M>F.
Most people asymptomatic.
Pathophysiology not well understood.

Question 2

Pagets - phases (3)

Answer 2

Lytic (usually asymtpmatic),
Mixed (Elevated ALP, fractures),
Sclerotic (Elevated hydroxyproline, more fractures. Sarcomas may develop)

Question 3

Pagets - types (2)

Answer 3

Monoostotic and polyostotic (more common, 80-90%)

Question 4

Pagets - buzzwords (9)

Answer 4

“Wide bones with thick trabeculae”
Blade of Grass sign - lucent leading edge in long bone
Osteoporosis Circumscripta - Blade of Grass in skull
Picture Frame Vertebra - Cortex thickened on all sides (Rugger Jersey is only superior and inferior end plates).
Cotton wool bone - Thick, disorganised trabeculae
Banana fracture - insufficiency fracture of bowed soft bone (femur or tibia usually)
Tam O-Shanter sign - thick skull
Saber shin - bowing of tibia
Ivory Vertebra - Differential finding, including mets. Pagets tends to be expansile

Question 5

Pagets - complications (7)

Answer 5

Deafness is most common.
Spinal stenosis from cortical thickening is very characteristic.
Others
- Cortical stress fractures
- Cranial nerve paresis
- High output heart failure
- Secondary hyperparathyroidism (10%)
- Secondary development of sarcoma (1%, often highly treatment resistant)

Question 6

Pagets - Trivia (4)

Answer 6

Giant cell tumours can arise from pagets.
Osteosarcoma is most common tumour from pagets.
Pagets bone is hypervascular and can be 5 degrees hotter than other bone.
ALP will be elevated up to 20x in reparative phase.

Question 7

Pagets - Skull (4)

Answer 7

Large areas of osteolysis in the frontal and occipital bones.
“Osteolysis circumscript” in lytic phase.
Skull looks like cotton wool in mixed phase.
Favours outer table

Question 8

Pagets - spine (2)

Answer 8

Cortical thickening causes “picture frame sign”.
Can also give ivory vertebral body.

Question 9

Pagets - pelvis (2)

Answer 9

Most common bone affected. Always involved iliopectineal line on pelvic brim.

Question 10

Pagets - long bones (2)

Answer 10

Advancing margin of lucency from one end to other (Blade of grass or Flame).
Often spares fibula, even in advanced disease

Question 11

Pagets - MRI (3)

Answer 11

Lytic/early mixed: Marrow shows heterogenous T2, iso T1 to muscle, speckled appearance
Late mixed: Fatty high T1 and T2
Sclerotic: Low T1 and T2

Question 12

Pagets - Nuclear medicine (3)

Answer 12

Bone scans used to help define disease extent and assess Rx response.
Classically “Whole bone involvement” - e.g. entire vertebral body including posterior elements, or entire pelvis.
Hot on all 3 phases

Question 13

Tendon ultrasound - Anisotropy (3)

Answer 13

Tendons are normally hyperechoic.
If they aren’t scanned perpendicularly to sound waves, they can look hypoechoic (can be confused for injury).
Particularly an issue for supraspinatus tendon as it curves along contours of humeral head, or long head of biceps in bicipital groove.

Question 14

Tendon US - tears (2)

Answer 14

Focal hypoechoic areas on ultrasound.
Can be difficult to tell complete vs partial tear (need MRI)

Question 15

Tenosynovitis - US (2)

Answer 15

Increased fluid within the tendon sheath.
May see associated peritendinous subcutaneous hyperaemia on Doppler

Question 16

Plantar fasciitis - US (2)

Answer 16

Thickening of plantar fascia >4mm, loss of normal fibrillar pattern.
Most commonly involved central band (there are 3 bands).

Question 17

Calcific tendonitis

Answer 17

Will shadow just like a GB stone, classically seen in supraspinatus tendon near it’s insertion.

Question 18

Arthrogram - basics (4)

Answer 18

Target is the joint capsule, not the joint itself.
Need the needle to touch a bone within the capsule.
Must be done without contaminating or damaging an adjacent structure like an artery.
Avoid air in the joint too, will cause susceptibility artifact.

Question 19

Hip arthrogram - procedure (6)

Answer 19

1) Mark femoral artery
2) Internally rotate the hip slightly, to localise femoral head-neck junction (target).
3) Clean and numb skin
4) Advance 20-22 gauge spinal needle into joint, straight down superior head-neck junction
5) Inject small amount of contrast to confirm position. Contrast should flow away from needle tip, if it doesn’t flow, it’s not in a space.
6) Inject the rest of the contrast

Question 20

Hip arthrogram - trivia (2)

Answer 20

Capsule is widest at head-neck junction.
Injected cocktail is around 4cc lidocaine, 10cc visipaque, 0.1cc Gd

Question 21

Shoulder arthrogram - procedure (6)

Answer 21

1) Supinate the hand (externally rotate shoulder)
2) Clean and numb skin
3) Advance 20-22 gauge needle into joint, straight down junction between middle and inferior thirds of humeral head, 2mm inside cortex.
4) Once you strike bone, pull back 1mm and turn bevel towards humeral head, should drop into joint.
5) Inject small amount of contrast to confirm position (should flow away from joint, otherwise not in a space)
6) Put rest of contrast in
(4cc lidocaine, 8cc visipaque, 0.1cc Gd)