Jahss classified traumatic dislocations of the first metatarsophalangeal joint occurring after hyperextension injury. The author is from the Hospital for Joint Diseases and Mount Sinai Hospital in New York City.
Patient selection: dislocation of the first metatarsophalangeal joint
Parameters:
(1) intersesamoid ligament
(2) sesamoid bone status
Intersesamoid Ligament
Sesamoid Bones
Type
intact
intact but dorsal to metatarsal neck
I
ruptured
intact
IIA
NA
fractured
IIB
where:
• A Type I dislocation is a simple dorsal dislocation, with the proximal end of the phalanx pulled distal and then displaced above the distal metatarsal head.
• The medial sesamoid is usually the sesamoid fractured in a Type IIB dislocation.
• If a distal bone fragment is generated in a Type IIB dislocation, then it may become located intra-articular and have to be surgically removed.
A Type II dislocation (both IIA and IIB) are usually reducible on closed manipulation, while a Type I dislocation is not.
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