CT

Hoffa fracture

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

 

Usually lateral femoral condyle

 

Osteoblastoma

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

Background

DefinitionGarden 3 Displaced Subcapital

 

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

Background

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

 

Femoral Head Fractures

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)

 

Chordoma

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%

 

Background

Anatomy

Pelvis 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

 

CT Scan

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

Bipartite Patella

Ossification

 

Patella may develop from one or multiple ossification centres at 3 years

 

Failure of centres to fuse may produce bipartite or tripartite patella

- usually bilateral and painless

 

Classically superolateral

 

Classification Saupe

 

I   Inferior Pole 5%

II  Lateral 20%

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