In an effort to gain greater insight into the tradeoffs associated wit
h modular hip prostheses, 2 approaches were taken, A questionnaire was
sent to each of the orthopaedic implant manufacturing companies askin
g specific questions regarding modular components, and a series of ret
rieved prostheses, both modular and nonmodular, were examined to deter
mine the potential sources of problems associated with modular connect
ions, The respondents to the questionnaire generally agreed that it wa
s more expensive to produce modular prostheses due to the required tol
erances at the modular connections, and that the increased flexibility
provided by the modularity was important to surgical outcome, There w
as less consensus on whether inventories were reduced and little data
to support any improvement in surgical outcome caused by modularity, T
he most frequent problems associated with modular connections were fre
tting and corrosion, Easily observable significant fretting occurred i
n 4% of 701 head/neck tapers, Corrosion was observed in >30% of the mi
xed-alloy head/stem combinations, in <10% of all-titanium-alloy modula
r components, and in <6% of all-cobalt-alloy devices, In 1 series of r
etrieved modular femoral components (15 titanium ahoy and 15 cobalt al
loy) with both sets having approximately the same duration of implanta
tion, 7% of the all-cobalt-alloy components had corrosion, whereas 33%
of the mixed-ahoy components had corrosion.