AVN

Epidemiology

Much less common than hip OA

- usually presents late

Aetiology

Similar causes as hip (AS IT GRIPS 3C)

Alcohol / Steroid / Trauma / Idiopathic

Gauchers

RA / RTx

Sickle Cell 

Types

1.  Dorsal lip fracture / Tuberosity fracture

- avulsion fractures

- most common

- beware avulsion T post

2.  Body fracture

3.  Stress Fractures

Body Fractures

Types

A.  Transverse fracture in coronal plane

B.  Transverse from dorsolateral to plantarmedial

C.  Central or lateral comminution