Module 5 - MSK Flashcards
what are the 4 muscles of the rotator cuff?
Supraspinatus: abduction, most susceptible to impingement
Infraspinatus: external rotation with arm by side
Teres minor: external rotation with arm abducted
Subscapularis: internal rotation, larges and strongest
What views are included in a “shoulder series” XR
- AP in external rotation to best demonstrate lesser and greater tuberosities of humerus
- Internal rotation
- Lateral or scapulular y : demonstrates coracoacromial arch, and the glenohumeral
- Axillary/axial view
Which of the following images demonstrates a shoulder dislocation? Is it dislocated anteriorly or posteriorly?
Internal rotation of humeral head
Posterior dislocation
Left
What is the difference between a hill sachs lesion and bankart lesion
Hill sachs: head of humerus
Bankart: glenoid rim
What is the most common mechanism for shoulder ACJ disruption
Usually direct impact onto acromium with rupture of stabilising ligaments, depressing scapula relative to clavicle
Describe the continuum of pathology for rotator cuff disease (5 steps)
- Impingement: Repetitive compression of cuff on coracoacromial arch
- Partial thickness tear: Chronic tendinitis or acute trauma
- Full thickness tear: Usually an extension of partial tear, remaining cuff compensates
- Massive tear: Weakness and functional impairment
- Arthropathy: proximal humeral migration, secondary OA
Describe 3 imaging modalities useful in rotator cuff pathology
XR: good at demonstrating calcific tendinosis
U/S: good at calcific tendinosis, directs injections
MRI: effectively demonstrates all structures including soft tissue
What are Gilula’s lines?
Borders of carpal bones used to assess carpal instability
- Proximal margin of proximal row (Scaphoid, lunate, triquetrium)
- Distal margin of proximal row
- Proximal margins of capitate/hamate
imaging features of rotator cuff tear
XR:
- calcific tendonitis
- calcification in the coracohumeral ligament
- cystic changes in greater tuberosity
- proximal migration of humerus seen with chronic RCT (acromiohumeral interval <7 mm)
- Type III (hooked) acromion
US: hypoechoic or anechoic defects in which fluid has replaced the area of the torn tendon
MRI: fatty streaks in muscle, humeral head cysts
imaging features of scaphoid fracture
Distal fractures in children, waist or middle third in adults
XR: need scaphoid views
CT: less accurate than MRI for occult fractures
MRI: for occult fractures <24 hours, T2 hyperintensity
Bone scan: acute increased radionucleotide uptake
imaging features of osteoarthritis (4)
- Joint space narrowing
- Sclerosis
- Subchondral cysts
- Osteophytes
Name a fracture associated with ACL rupture
What are 2 MRI findings associated with ACL rupture
Segond Fracture: ACL rupture associated with lateral fibular head fracture
Deep sulcus sign: Depressed subchondral plate
Wrinkled tibia (posterior tibia wrinkling subtly) obvious on MRI
What are they? Which requires ORIF
A: Colles
B: Smith
C & D: Barton (partial intra-articular)
Barton requires ORIF
Late complications of distal radial fractures (4)
Post-traumatic arthritis
Malunion
Tendon rupture
Stiffness
List the 5 ottawa knee rules for XR of the knee post-trauma
Aged <55
Tenderness at fibula head
Patellar tenderness
Inability to flex knee to 90 degrees
Inability to weight bear (4 steps, immediately and at presentation)
MRI appearance of ligamentous injury of the knee
Bone marrow oedema appears bright on T2
Proton density sequences -> Meniscus black
List the 4 ottawa ankle rules
High energy injury
Inability to weight bear
Gross swelling
Bony tenderness
What is the tibio-fibular clear space? What is its relevance?
1 cm above joint, normal clear space is <6mm
see red line
If wider, is marker for syndesmotic injury
Describe the imaging appearance of aggressive bone lesions on different imaging modalities
DESTRUCTION: permeative
MARGIN: poorly-defined
PERIOSTEAL REACTION: spiculated (lamellated is slightly less aggressive)
What are the most common bone tumours in the following age groups
0-10 yo
5-25 yo
10-25 yo
20-40 yo
0-10 yo: histiocytosis X or eosinophilic granuloma
5-25 yo: ewing sarcoma
10-25 yo: osteosarcoma
20-40 yo: giant cell tumour
What are the most common bone lesions based on the following locations
Epiphyseal
Metaphyseal
Diaphyseal
Epiphyseal : chondroblastoma
Metaphyseal: osteosarcoma
Diaphyseal: ewing’s sarcoma
What modalities are useful in the diagnosis of bone tumours and what is their specific utility?
XR: may be diagnostic
MRI: aids diagnosis, local staging
PET: distant staging
CT: calcification investigation as secondary investigation after XR
U/S: biopsy
What is aseptic lymphocytic vasculitis?
Adverse reactions to metal debris where particle wear and discharge creates a biological response resulting in soft tissue lesion that impacts on the prosthesis
Name 6 types of prosthetic complications
Aseptic loosening: due to mechanical stress and osteolysis, often in first 2 years (perioprosthetic radiolucency >2mm for knees, >0.5 for shoulders)
Polyethylene wear: late complication often of TKA, joint space loss +/- tilt
- Tibial component loosens more frequently than femoral
Particle disease: common in hip prostheses
Infection: in 0.5-2%, often normal on imaging, only through aspiration of fluid that it’s obvious
Component failure: Ceramic liner fracture
Bead shedding: from the outer coating of component
