The Oxford hip score demonstrates moderate ceiling effects at one and two years after total hip arthroplasty: which patients are at risk and does it matter?
摘要
The aim was to assess whether the postoperative Oxford Hip Score (OHS) demonstrated a ceiling effect at 1 or 2 years after total hip arthroplasty (THA) and to identify which patients are more likely to achieve a ceiling score and whether this limits assessment of their outcome.
MethodsA retrospective cohort of 7871 patients undergoing primary THA was identified from an established arthroplasty database. Patient demographics, ASA grade, socioeconomic status, OHS and EuroQol questionnaire were collected preoperatively and at 1 and 2 years postoperatively. Regression analysis was used to identify independent preoperative factors associated with achieving a ceiling score. Receiver operating characteristic curves were used to identify preoperative OHS's that predicted a postoperative ceiling score.
ResultsThe ceiling effect (proportion achieving the maximal score) at 1 year was 21.8% (n = 1372) which increased significantly (p < 0.001) to 26.6% (n = 1569) at 2 years. Female gender (p ≤ 0.028), younger age (p < 0.001), decreasing socioeconomic deprivation (only for 2-year OHS), a better preoperative OHS (p < 0.001) or EQ-VAS (p < 0.001) were independently associated with a ceiling OHS postoperatively. The preoperative OHS was demonstrated to be a poor discriminator of achieving postoperative ceiling score at 1 year (AUC 62.4%, 95% CI 60.7 to 64.1, p < 0.001) and 2 years (AUC 61.5%, 95% CI 60.0 to 63.2). Those achieving a postoperative ceiling OHS at 1 and 2 years had statistically significant (p < 0.001) greater improvements in their OHS, EQ-5D and EQ-VAS and were more likely to have achieved a minimal important change in their OHS relative to their preoperative baseline and a postoperative patient acceptable symptom state.
ConclusionThe OHS demonstrated moderate ceiling effects at both 1 and 2 years following THA, and the preoperative score was a predictor of achieving a ceiling score. However, it would seem the ceiling effect did not limit the potential for improvements relative to baseline and achieving clinically meaningful values in the OHS.