avascular necrosis

Definition

Spontaneous osteonecrosis of the navicular

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

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

Definition 

Avascular necrosis & subsequent disintegration of lunate

Aetiology

50-75% history of trauma

Occasionally seen in sickle cell / steroid use

Pathogenesis

Vascular Theory

Trauma disrupting vascularity

- single incident with disruption of blood supply

Definition

Body Fracture

- fracture line exits inferior surface behind lateral process

- into posterior facet

- intra-articular body fracture

Neck Fracture

- fracture line exits inferior surface anterior to lateral process

- in front of sinus tarsi

- extra-articular neck fracture

Types

1.  Shear

2.  Crush

3.  Posterior Process