Avascular necrosis & subsequent disintegration of lunate
50-75% history of trauma
Occasionally seen in sickle cell / steroid use
Trauma disrupting vascularity
- single incident with disruption of blood supply
Scapho-lunate advanced collapse
- caused by malalignment of scaphoid on radius
- due to scapholunate disruption
Most common cause of wrist OA
1. Radio-scaphoid degenerative changes
- from abnormal flexion of scaphoid
Dorsal Intercalated Segmental Instability / CID
Scapholunate joint
- C shaped
- 2-3 mm thick dorsally with transverse fibres
- thin palmar
Dorsal extrinsic ligaments
- V shaped, onto trapezium
Loss of normal ligamentous and / or bony constraints of wrist
Overall alignment maintained by extrinsic and intrinsic ligaments
Carpal bone to carpal bone
- support the lunate in a balanced position
A. Scapho-lunate ligaments
Elderly population
Less common in younger population
Type I
Fracture lateral to the CC ligaments
- does not extend into the ACJ
- non displaced
- most common 4:1
Massive tear
1. > 5cm
- retracted to humerus / glenoid margin
2. At least 2 complete tendons
- lose SS / IS or SS / SC
Synovial joint with hyaline cartilage
Has fibrocartilage intra-articular disc
- complete or incomplete
- usually degeneration by 4th decade
Clavicle may lie superior to acromion in normal population
Acromioclavicular Ligaments
Osteochondritis Dissecans
- separation of avascular fragment of bone & cartilage
M : F = 2:1
Mean age 18 years
- can present as young as 9
4:1000
Rotational force incurred while joint partially flexed & extending
- caught between femoral & tibial condyles
- usually valgus & ER / varus & IR
FOOSH
Age 6 as maximum ligamentous laxity
- < 4 - physeal separation
- > 8 - dislocation
Male > F
Supracondylar region in 6 year old is thin
- thinnest at olecranon fossa (2-3 mm)