AVN

Definition

Spontaneous osteonecrosis of the navicular

Indications for THA

Osteoarthritis

- abnormal morphology

- loss of head neck offset

- bony impingement on acetabulum

AVN

Definition

Osteonecrosis of the navicular

Epidemiology

Present at age 4-6 years

- same as Perthes disease

M:F 5:1

Bilateral in 20%

Aetiology

Repetitive trauma to maturing ossific nucleus

Indications

< 60 with good bone stock and preserved joint space

Reduction

Union rates increased with anatomical reduction

Options

- closed reduction

- open reduction / if closed reduction fails

Accept

- no varus

- < 15^o valgus

- < 10^o AP plane

Non-Operative

Education regarding shoe wear

- extra wide / large toe box

Insoles

- longitudinal arch support

- pre MT dome for metatarsalgia

- podiatry to attend to callosities

Toe spacers

Analgesia

Operative

Indications

1.  Continued pain and discomfort

2.  Difficulties with shoe wear

Incidence

Young men

Posterior / Anterior 9:1

Aetiology

High velocity injury

- head direction at impact decides direction of dislocation

Anterior Dislocation 

Externally rotated & abducted leg

- flexion = inferior dislocation

Management Summary

Stage 0

Natural history mixed

- depends on size of lesion and diagnosis

- treat if becomes asymptomatic

- may benefit from bisphosphonates

Stage 1 / Normal X-ray, abnormal MRI

Forage: 80% G/E

Bisphosphonates

Stage 2 / Abnormal X-ray with cysts and sclerosis

A:  As for Stage I

Definition

Non-traumatic or traumatic condition of femoral head with bone death

Epidemiology

20 - 50 yo (average 38)

- M: F 4:1

NHx  

70-80% with AVN will progress within 1 year

AVN  

Largely related to degree of displacement

Incidence

Hawkins Type I

- 0% to 13% 

Hawkins Type II 

- 20% to 50% 

- usually only patchy and not a problem (rarely collapses)

Diagnosis

Xray

- sclerosis

CT