THE TRADEOFFS ASSOCIATED WITH MODULAR HIP PROSTHESES

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.