Simultaneous bilateral versus unilateral total hip arthroplasty: Pain and physical function in a one- and five-year follow-up - retrospective patients record study

BACKGROUND: Total hip arthroplasty (THA) decreases pain and improves function in patients with osteoarthritis. In some cases, both hips have been operated simultaneously. Our aim was to report patients’ pain and physical function after one- and five-years post-operatively among patients who underwent unilateral THA and those who underwent bilateral THA at the same time in one orthopaedic hospital in Finland. METHODS: The study group consisted of 488 patients retrospectively selected patients from a single centre; 421 of them underwent unilateral THA and 67 underwent simultaneous bilateral THA. The patients had two clinical examinations one and five years postoperatively. Systematic data about pain and physical function were collected using the scaled Orton Hip Score (sOHS). Register data on revisions and mortality events were from the Finnish Institute of Health and Welfare. RESULTS: At the one-year follow-up, total sOHS was improved remarkably from the preoperative situation, both in the unilateral THA (age and gender adjusted mean improvement 42 points (95% CI: 40 to 44, p < 0.001) and in the bilateral THA groups (age and gender adjusted mean improvement 45 [95% CI: 41 to 49], p < 0.001), with no group differences after five-years of operation (age and gender adjusted p = 0.19). Total sOHS was statistically higher in the bilateral THA compared to the unilateral THA after one year (98 vs. 95, p < 0.001) and five years (97 vs. 95, p = 0.003) of operation. CONCLUSIONS: Patients in unilateral THA and bilateral THA groups had increased their physical function, and pain had decreased after one-year follow-up of the primary THA operation, and condition remained after five years of operation. At follow-ups, patients who underwent bilateral THA had slightly better physical function compared to patients who underwent unilateral THA at follow-up; however, this difference had no clinical relevance. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12891-023-06743-w.