dislocation

Incidence

Timing

Early < 3 - 6 months

- most common

Stryker dual mobility

Concept

Aims

Prevent contractures

Prevent dislocations

Improve walking 

Provide stable and painless sitting

Allow perineal care

Issues

Hip Dislocation

Adductor contractures

Flexion contractures

In-toeing

Windswept hips

Hip Dislocation

Natural History

Accepted that a dislocated hip in CP is painful

Epidemiology

Deadly & rare

- usually post mortem

More common in children due to

- immature joints 

- larger head to body ratio

- relative ligamentous laxity

Aetiology

High velocity trauma

- MVA

Mechanism

- hyperextension, distraction & rotation

Types

Pure ligament injury usually

Definition

Facet joint dislocations secondary flexion distraction injury

Epidemiology

10%

Stages

1. Unifacet subluxation - interspinous process widening

2. Unifacet dislocation - 25% anterolisthesis

3. Bifacet dislocation - 50% anterolisthesis

4. Complete vertebral translation - 100% anterolisthesis

Unilateral Facet Joint Dislocation

Types of Instability

1.  AP Instability

2.  Varus Valgus Instability

3.  Global Instability

4. Frank Dislocation

Mechanism

1. Direct lateral blow to patella

- usually with knee partly flexed and quadriceps relaxed

2.  Indirect low energy injury

Definition

Repeated dislocation of patella with minimal trauma

- 15-20% of paediatric acute patella dislocations

- more common girls 

- often bilateral

Dislocation occurs unexpectedly when quadriceps contracted with knee in flexion 

Direction