To describe the extent of variation in outcome measure usage in hip and knee replacement randomized trial literature, and to summarize this variation in the context of the International Classification of Functioning, Disability, and Health (ICF) conceptual model created by the World Health Organization (WHO).
We used a defined search strategy in Medline and EMBase databases to identify articles published from January 2000 to February 2007. Studies were reviewed if they were randomized trials with a ≥6-week followup and if they used noninvasive outcome measures of impaired joint function or whole-person limitations in daily activities or functional status. The WHO ICF model was used to categorize outcome measures.
Of 972 studies, 160 were included for review. Of these, 82 were conducted on patients with hip replacements, 75 on patients with knee replacements, and 3 on patients with both. The most common outcome measure in knee trials was the American Knee Society score (used in 48% of reviewed studies), and in hip trials was the Harris hip score (52.4%). At least 20 different outcome measures were used in the hip trials, and at least 14 different measures were used in knee trials. The primary outcome was identified in only 24% of trials.
We found extensive variation in outcome measures across trials and saw inconsistency across the components of the WHO ICF model. To improve interpretability, future work should determine whether consensus can be developed for a standardized set of outcome measures for hip and knee replacement trials.