chapter 4 - general principles of dislocations Flashcards
what is a dislocation
there is no contact between the articular surfaces that normally constitute the joint
what is subluxation?
joint surfaces are abnormally opposed but there is some contact
what is joint congruity?>
it means that in a normal joint the opposing articular surfaces are shaped to fit against each other - ie they are congruent. Alteration or displacement will result in the joint being incongruent.
what is the joint space?
it is a radiological entity- what we see is the radiolucent articular cartilage which appears to be a black space on xray
why is the joint space black, eventhought it is not actually a space?
it is the radiolucent articular cartilage which is not calcified and therefore appears to be black
what does a decreased joint space indicate?
worn or thin cartilage
what is the synovial space?
a space which has the potential to distend to accomodate fluid
why do joints dislocate? give 3 factors responsible for the stability of a joint.
- bone congruity
- joint capsule and surrounding ligaments
- muscles acting across the joint
list 3 striking features of a dislocation
deformity and loss of normal bony landmarks
painful loss of function
distal neurovascular complications
which special investigation is NB for a dislocated joint
standard xray - AP and lateral views
which 6 specific dislocations are often missed by the inexperienced doctor?
cervical spine ( uni-facet dislocation) posterior sternoclavicular dislocation posterior shoulder dislocation radial head carpal and tarsal bones tarso metatarsal (lisfranc)
2 reasons why dislocations have to be treated more urgently than most fractures
- the articular ends are larger than the shaft and therefore there is a high risk of compression of nerves and vessels
- large displacements will cause traction injuries to the neurovascular structures
why is an angiogram always indicated in a knee joint dislocation despite normal pulses?
there is a risk of intimal tears or flaps whcih may result in the occlusion of a vessel
how to manage a dislocation
open or closed reduction
when is an open reduction indicated
fracture/dislocations ie both occur together
occasionally irreducible dislocation
old un reduced dislocations
what is the management of a dislocation post reduction?
- splinting and rest for a few days till swelling subsides
- bracing and controlled exercise programme for 6 wks to 3m
who is likley to present with an unreduced dislocation?
elderly pt alcoholic mentally challenged epileptic after convulsion multiply injured pt
what is the approach to the management of an unreduced dislocation? outline the 3 scenarios
- stable pain free joint with adequate function = accept the dislocation
- unstable or painful joint with impaired function = attempt to manipulate gently under anaesthesia with full muscle relaxation and if this fails –> open reduction
- joint which remains painful or unstable despite reduction= arthroplasty or athrodesis
which 2 joints are prone to recurrent dislocation and why?
shoulder
patella femoral joint
= both have a small area of bony contact on one side of the joint and no bony containment
how do you treat a joint that is prone to dislocation
soft tissue reconstruction
osteotomy
