CT

Indications

RA 

OA 

AVN 

Contra-indications

Infection

Charcot

Paralysis of deltoid

Torn rotator cuff

Insufficient glenoid bone stock

Epidemiology

Usually after 50-60 years of age

Aetiology

Primary 90% of cases

Secondary

- AVN

- trauma

- instability

Pathology

Definition

Coronal plane fracture of distal femoral condyle

- intra-articular

- often only attachment is posterior capsule

Epidemiology

Rare

Mechanism

Usually a severe valgus trauma

Xray

Epidemiology

Uncommon

< 1% Primary bone tumour

Young boys

- second decade

Location

Similar to OO

Spine 30%

- especially posterior elements

Long bones 35%

Clinical

Back or limb pain

- pain less severe than OO

Definition

Fracture distal to articular surface & proximal to intertrochanteric region

Epidemiology

On average 4 years younger than intertrochanteric fracture

One year mortality as high as 36%

Only 1/3 will return to pre-fracture living environment

Anatomy

3 facets

1.  Posterior facet (STJ)

2.  Middle facet (sustenaculum tali)

3.  Anterior facet (on distal medial aspect)

Anterior process 

- forms calcaneocuboid (CCJ) articulation

Thalamic portion 

- under lateral process talus

Tuberosities

Posterior tuberosity 

- posterior process / T Achilles attachment

Incidence

5-15% of posterior dislocations

Aetiology

Posterior hip dislocation

Pipkin Classification

Type I - head fracture below fovea

Undisplaced

- non operative

Displaced

- excise fragment if small

- ORIF fragment if large (can contribute to instability)

Definition

Primary malignancy arising from remnants of the notochord

Epidemiology

Rare malignant tumour

Middle-aged adults (50-70)

M>F

Location

In midline in axial skeleton

Base of skull 35%

Vertebrae 15%

- especially cervical

Sacrum 50%

Anatomy

Pelvis is a true ring

- any anterior fracture must have a posterior injury as well

- integrity of the posterior sacroiliac complex is key

Bony Anatomy

2 innominate bones + sacrum

Symphysis pubis < 5mm

SI joint 2-4 mm

Principle

Irradiate a slice of tissue from multiple angles

Measure the output from different sides

Tissues have different densities

- with denser tissue fewer x-rays reach the detectors

Hounsfield scale

Bone    2000

ST        40

Water   0

Fat       -100

Air       -1000