instability

AP / Long Leg Views

Quantify Valgus Malalignment

Lateral Xray

1.  Assess Patella Alta

30^o flexion

Bristow

Concept

Non-anatomical bony block 

- transfer of coracoid process through subscapularis

- dynamic anteroinferior musculotendinous sling

- provides subscapularis tenodesis

- preventing lower portion from displacing proximally as arm abducted

- when shoulder in vulnerable position abduction and ER

Types

Dorsal

- most common

Volar

Causes

1.  Acute traumatic peripheral tear TFCC with DRUJ dislocation

- usually major trauma

- dorsal or volar

2A.  Distal radial fracture

Definition

Volar Intercalated Segmental Instability

- secondary to injury to the lunate-triquetral ligament

Epidemiology

Less common

Aetiology

Caused by fall on outstretched extended wrist

- hypothenar eminence strikes ground first 

- isolated LT ligament injury

Can be part of perilunate dislocation

- SL heals

- residual LT laxity

Definition

Patients usually complain of subluxation rather than dislocation

- rarely requires reduction

Different entity to acute posterior dislocation usually

Epidemiology

Rare

Aetiology

1.  Ligamentous laxity > 50%

- commonly associated with MDI

- posterior only 20%

- posterior & inferior 20%

Definition

Instability in at least 2 planes

- postero-inferior

- antero-inferior

- antero-postero-inferior

Epidemiology

Recognised as a common problem 

- often misdiagnosed

Most patients athletic

Definition

Chronic instability due to rupture of one or more parts of the lateral ligament

Anatomy

Progressive injury

1. Anterolateral capsule

2. ATFL

3. CFL

NHx

Can lead to ankle OA over time