To assess changes in the health outcomes of Japanese patients before and after total hip arthroplasty (THA), and to assess the impact of THA on commonly performed postures or body positions requiring deep flexion of the hip joint such as the use of Japanese squat toilets.
Consecutive patients undergoing primary THA between July 2003 and July 2004 were eligible for the study. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the EuroQol 5D (EQ-5D) were administered at the preoperative period and two postoperative periods of 6 weeks and 6 months. The patients were also asked to rate three items regarding common activities of daily living in Japan such as squatting. Changes in scores were examined using effect size and proportion at the floor and ceiling.
Four-hundred and fifty-one patients completed both pre- and post-THA surveys. Significant improvements in pain and physical function as measured by WOMAC and EQ-5D were evident within 6 weeks. Changes in WOMAC and EQ-5D subscale scores and scores for each item from the three time periods were highly significant (P=0.000). The effect size was 1.56 for WOMAC pain and 1.38 for physical function at 6 months. In contrast, two items (Japanese toilet and seiza) became significantly worse at the 6-week postoperative period (P=0.000) and returned to preoperative levels by the 6-month postoperative period.
These results highlight the importance of evaluating culturally sensitive physical functions in addition to conventional measurements for the health outcomes of THA patients.