A pseudoarthrosis (plural: pseudoarthroses) (a.k.a. false joint) is a mobile fracture non-union.
Pathology
A fibrous, pseudosynovial capsule forms around the non-union and viscous fluid fills the site that may simulate synovial fluid.
Etiology
failed bone graft
ankylosing spondylitis (post-trauma)
diffuse idiopathic skeletal hyperostosis (post-trauma)
Bertolotti syndrome: association of transitional lumbosacral junction due to pseudarthrosis formation
Common post-traumatic locations include:
scaphoid waist
humeral shaft
clavicular shaft
distal tibial shaft
talar neck