Validity and responsiveness of the Oxford hip score in a prospective study with Japanese total hip arthroplasty patients

Background  With the increasing need for disease-specific health outcome measurements, the Oxford hip score was developed to measure health-related quality of life of total hip arthroplasty (THA) patients in the United Kingdom. The Oxford hip score comprises 12 items pertaining to pain and physical function, which are increasingly used to measure health outcomes of patients who have undergone THA. The purpose of this study was to establish the validity and responsiveness of the Oxford hip score in a prospective study of Japanese patients. Methods  The study was conducted at two hospitals. The eligibility criterion for the study was consenting adult patients who underwent primary unilateral THA between April 2005 and October 2007. Three scales were self-administered at the preoperative stage and 6 months after THA. These scales were the Oxford hip score, the Short Form-36 (SF-36) version 2, and three activities requiring deep flexion of the hip (i.e., clipping one’s toenails; use of a Japanese squat toilet; “seiza” — sitting on one’s legs on the floor, a common posture while eating in Japan. Results  A total of 224 consenting adult patients were recruited. Among them, 125 (61.9%) participated in pre- and postoperative surveys. Altogether, 108 (22 men, 86 women; mean age, 58.4 ± 12.5 years) of the 125 patients answered all the items. A significant improvement in the mean scores was observed in all scales. Correlation coefficients between the Oxford hip score and the SF-36 version 2 (physical functioning, role physical, bodily pain) ranged from 0.60 to 0.76 preoperatively and postoperatively. Effect size was 1.7 for pain and 1.3 for physical function. The effect size for seiza was small (0.3). Conclusions  This study demonstrated the validity and responsiveness of the Oxford hip score in a prospective study. However, it does not measure activities requiring deep flexion of the hip joint, and the use of additional items is suggested.