Influence of the contralateral hip state after total hip arthroplasty on patient-reported outcomes measured with the Forgotten Joint Score-12.

PURPOSE: The purpose of this study was to examine the influence of the contralateral hip state on postoperative assessment using the Forgotten Joint Score-12 (FJS-12) in comparison with the McMaster Universities Osteoarthritis Index (WOMAC) and the Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ).

METHODS: One hundred and thirty-four hips underwent total hip arthroplasty (THA) between 2014 and 2015. Of these, the subjects were 106 hips with degenerative hip arthrosis as a primary disease for whom initial THA was performed on the affected side. The WOMAC and JHEQ were investigated before surgery and 1 month, 6 months, and 1 year after surgery. The FJS-12 was examined 1 month, 6 months, and 1 year after surgery.

RESULTS: We divided the subjects into three groups based on the state of the contralateral hip, which was not surgically treated in this study: healthy (n = 43), THA (n = 31), and OA (n = 31) groups. One year after surgery, the mean FJS-12 scores in the healthy, THA, and OA groups were 69.1, 52.8, and 68.0 points, respectively. In the THA group, the score was significantly lower than in the healthy and OA group. There were no significant differences in WOMAC and JHEQ scores among the three groups.

CONCLUSIONS: The FJS-12 score in the presence of an arthroplasty on the contralateral side was more markedly influenced by the contralateral hip state compared with that in the presence of contralateral painful OA. This result suggests that it is necessary to understand the characteristics of PROs and utilize them for post-THA assessment.