The use of modularity in revision total hip replacement.

A study was undertaken to establish the pattern of components revised in recent years during total hip revision to establish how often a modular feature of a retained component was used. All total hip revisions performed by the total joint service of the University Hospital between 1991 and 1995 were reviewed. Revisions involving a surface replacement, endoprosthesis, bipolar stem, or infection were excluded because retention of components is not an option in these cases. This left 158 cases for review. If a modular femoral or acetabular component was retained, it was determined whether a different length of modular head or different liner type was replanted, thus using a modular feature of the component. The most common pattern of component revision was to revise all components, which was done in 77 of 158 cases (48.7%). The second most common pattern was to revise a socket and leave the stem in place (53/158, 33.5%). The third most common was to revise the stem and leave the socket in place (22/158, 13.9%). The least common was to retain both the stem and socket and exchange the head and liner (6/158, 3.8%). Of the 59 cases in which the stem was retained, a modular head of a different length was used in 52 (88%). Of the 28 cases in which a socket was retained, a different liner type was used in 14 (50%). The modular aspect of the retained component was a valuable asset at the time of revision in a high percentage of cases (66/158, 41.8%).