Summary
Component malalignment and impingement are possible causes of recurrent luxation following
total hip replacement in the dog. In the two cases presented in this report, luxation
that was probably due to impingement was managed by exchanging the standard 17 mm
prosthetic head for a 24 mm prosthetic head. This required removal of the original
acetabular cup liner and placement of a new polyethylene liner that would accept the
24 mm head into the stable acetabular shell. In the first case, a 50 kg Malamute dog,
recurrent luxation was initially managed by component alignment revision, iliofemoral
suture, triple pelvic osteotomy and a novel lasso technique, without long-term success.
After exchanging the head and cup liner, luxation did not recur over a 12-month period.
In the second case, a 65 kg Newfoundland dog, impingement was suspected after a second
luxation event. Luxation did not recur during the nine months after exchange of the
head and cup liner. The larger prosthetic head used in these two cases increased the
impingement-free range-of-motion of the joint and increased the translation distance
required for luxation (jump distance).
Keywords
Total hip replacement - impingement - cup liner exchange - luxation - head diameter
