Which direction is common for Glenohumeral Dislocation
Anterior (95%)
Radiographic signs for Posterior GH Joint Dislocation
- Rim sign
- Trough line sign
- Lack of humeral head/glenoid fossa overlap
- Vacant glenoid sign
- Tennis racquet appearance
- Superior displacement of humeral head
Mechanism of Inferior GH Dislocation
Hyperabduction and get stuck in abduction
Radiographic sign in Rotator Cuff Tear
- Superior Subluxation of humeral head (not dislocation)
- Reduced Acromiohumeral Joint space (<7mm)
- Head may form pseudo joint superiorly with clavicle and acromion
Reasons of humeral move superiorly when rotator cuff tear
Reduced holding power of infraspinatus tendon allowing elevation of humeral head by deltoid
Mechanism of Glenoid Labrum Tear
Biceps tendon tesion during external rotation
Common in Overhead athletes
Internet:
Forceful eccentric traction is exerted on the biceps tendon and in throwers by the chronic stress placed on the labrum when the shoulder is forcefully abducted and externally rotated.
Types of dislocated Acriomioclavicular Joint and its radiographic signs
Type I- No tear; no radiographic signs
Type II- AC ligaments torn; coracoclavicular ligaments stretched, but intact
Radiographic signs include increased AC joint space, but normal coracoclavicular distance
Type III- AC ligaments AND coracoclavicular ligaments torn
Radiographic signs include widened AC joint space, elevation of distal clavicle above acromion and coracoclavicular distance >5 mm wider than the opposite side
Which direction of displacement is life-treatening for dislocated sternoclavicular joint
Posterior displacement
Damage the neurovascular bundle at thoracic outlet (subclavian artery and vein)
Extra:
anterior sternoclavicular and costoclavicular ligaments tear when the joint dislocated
Common sites for Simple Bone Cyst (Unicameral Bone Cyst)
- Proximal femur and proximal humerus (60-75%)
- Fibula
- Base of calcaneal neck (4%, > 2 years of age)
- Talus
- Not in spine or calvarium
Radiographic Signs of Simple Bone Cyst (Unicameral Bone Cyst)
- Intramedullary central metaphyseal lesion adjacent to epiphyseal cartilage (during active phase)
- Migrates into diaphysis with growth (during latent phase)
- Does not cross epiphyseal plate
- 2-3cm oval radiolucency with long axis parallel to long axis of host bone
- Thin sclerotic margin
- Fallen fragment sign if fractured (20%) = centrally dislodged fragment falls into a dependent position
- Most spontaneously regress
General Tumour characteristics, commandments and clues
- Focal or multifocal areas of increased or decreased bone density
- Thou shall respect joint spaces and physes
- Soft tissue mass with bone involvement
Bone Density Changes Tumour look-a-likes
- Epiphyseal changes
- Eccentric lesions with larger soft tissue components
- Eningmas, masqueradors
What action of GH joint move when different location Fracture at proximal Shaft of humerus
Proximal to pec M
- Head abducts and rotates
Between pec M and delt
- head will adduct
Distal to deltoid
- head will abduct
Radiographic signs for Anteior GH Joint Dislocation
- Inferomedial displacement of humeral head
- Altered head shape
- Presence of Hill-Sachs or Bankart lesions
Causes and clinical finding for Posterior GH Joint Dislocation
Triple E:
Epileptic convulsion, electric shock or extreme trauma
Reverse hill-Sachs and reverse bankart lesion
- Impaction of the anteromedial humeral head and posterior glenoid
