Outcome after total hip arthroplasty - Part II. Disease-specific follow-upand the Swedish National Total Hip Arthroplasty Register

The Swedish National Total Hip Arthroplasty Register records primary hip re placements, revisions and surgical technique/environmental factors, The end -point for failure is revision. A prosthesis still in place, however, does not mean success, Clinical and radiographic outcomes should describe in mor e detail the efficacy of hip replacement surgery instead of the relatively blunt outcome measure that the register can provide. We performed a clinica l outcome analysis on patients with primary total hip replacement thus test ing the adequacy of the end-point for failure in the Swedish register. 1,11 3 randomly selected patients who had had total hip replacement surgery betw een 1986 and 1995 answered a disease-specific self-administered questionnai re (WOMAC). A cohort of 344 patients was studied, using the Harris Hip Scor e and a conventional radiographic examination as outcome measures. We found clinical failure rates of 13% and 20% for all implants after 10 years, usi ng 60 points or revision as the definition of failure in the Harris Hip Sco re and WOMAC, respectively, The result, according to the register during th e same period, was a 7% revision rate. The clinical failure rate depended o n the type of evaluation tool, definition of failure and demographics, whic h made it difficult to decide whether there was a need for revision. With t he exception of pain measured by the Harris Hip Score, the results showed n o significant correlation between clinical failure and radiographic failure , Hence, with the knowledge that there is a difference between the revision rate according to the register and clinical outcome, the strict definition of failure in the register is useful as an end-point for primary hip repla cement surgery.