dislocation

Background

Definition

Dislocated Patella

 

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

 

Perilunate dislocations

Epidemiology

 

Young men in 20's and 30's

 

Aetiology

 

High energy injuries

- fall from heights

- MVA

 

Mayfield Classification

 

Injury progresses from radial to ulna

- usually disruption proximal row either side of lunate

 

1.  Capitate usually displaces dorsally initially

- volar lunate dislocation is end stage

 

Complications

Intraoperative glenoid fracture

 

Avoid by

- careful reaming and drilling osteoporotic bone

 

Management

1.  Rotate metaglene

- use locking screws to stabilise glenoid

2.  PA screws

- cannulated 4.0 mm screws

- inserted percutaneously from posterior

 

Haematomas

 

Great deal of dead space is created

- always use a drain

Head size

THR Large Head

Issues

 

Wear

Stability

Normal feel of hip

Increased ROM

 

Wear

 

Large head

- increase volumetric wear

- less penetrative / linear  wear

 

Small head

- increased linear wear

- decreased volumetric wear

Pisiform

Subluxation & dislocation

 

Diagnosis

 

Pisotriquetral view

- forearm positioned 30° supinated off the neutral position

- loss of symmetry between the pisiform and triquetrum is required for the diagnosis

- carpal tunnel view may be helpful in further assessment of the joint

 

Osteoarthritis

 

Clinical

 

More common problem

 

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