Lunate/Perilunate dislocation
Definitions
Lunate dislocation: lunate is forced volarly or dorsally whilst caprus remains aligned
Perilunate dislocation: the lunate stays in position whilst the capitate dislocates
Anatomy
On a lateral radiograph; the distal radius, lunate and capitate should be in a line
Mechanism
High energy impact
Wrist extended ulna deviated leading to intercarpal supination
Epidemiology
Approximately 25% missed on initial presentation
Orthopaedic emergency due to potential damage to the median nerve
Clinical presentation
Acute wrist swelling
Acute pain
Median nerve sx in 25% of patients
In a across section view of the carpal tunnel, the median nerve is directly above the lunate
Imaging
PA X-ray wrist
Lateral wrist
Break in Gilulea's arcs
Piece of pie sign: triangular shaped lunate
Lunate and capitate overlap
Scaphoid/Lunate angle > 70 degrees
Loss of llinearity of the radius, capitiate and lunate
Management
Operative
Non-operative
Closed reduction and cast
Not performed often due to poor functional outcome and risk of recurrence
Reduction in ED + open reduction, ligament repair +/- carpel tunnel release in surgery
Even in these patients stiffness and weak grip strength are a complication