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

Epidemiology

Uncommon

- dancers

- athletes

Aetiology

Hyperdorsiflexion of the MTPJ

Pathology

MT head dislocates plantar

- may buttonhole through capsule

- can prevent closed reduction

Blocks to Reduction

1.  Sesamoids

2.  Conjoint tendon

3.  Intersesamoid Ligament

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