We studied the complications involving the patella following total knee
arthroplasty in eighty-six knees in which thirty-four unconstrained and
fifty-two offset hinge prostheses had been implanted. The abnormalities
that we studied included: patellar dislocation, five knees; subluxation,
eighteen knees; localized wear, three knees; and generalized wear, four
knees. In twenty-three patients these complications were associated with
patellar malalignment, and occurred predominantly when the offset hinge
model of prosthesis was used. The complications were attributed partly to
mechanical factors inherent in the prosthetic design and partly to
anatomical abnormalities. Failure of the surgeon to compensate adequately
for both of those factors at the time of operation was a factor in most of
the complications.