Clinical and radiographic outcomes of primary total hip arthroplasty with the revelation hip system using density mapping

The Revelation Hip System is a cementless stem with a lateral flare concept. Stable fixation is achieved by fitting the stem to the medullary cavity of the proximal lateral femoral cortex. Patients who have undergone total hip arthroplasty using the Revelation Hip System show good postoperative clinical and radiographic outcomes. However, to the best of our knowledge, no study has reported the relationship between stem fitting and clinical or radiological outcomes after the surgery. In the present study, we investigated the relationship between stem fitting and clinical or radiological outcomes after total hip arthroplasty (THA) using the Revelation Hip System. In this study, 28 hips of 26 patients who were treated with the Revelation Hip System for osteoarthritis, osteonecrosis of the femoral head, rheumatoid arthritis, and rapidly destructive coxarthropathy and were followed up for > 5 y were enrolled. These patients were divided into two groups, including the rest fit group (11 hips, group R) and the control group (17 hips, group C), according to the results of the density mapping analysis. In group R, the lateral side of the stem fits on the medullary cavity of the proximal lateral femoral cortex, while in group C, the lateral side of the stem did not fit. Radiographic results showed no significant differences between the groups in terms of stem alignment, subsidence, and stress shielding around the cup. The incidence of stress shielding around the stem in zone 7 was not significant but tended to be higher in group R than in group C ( p = 0.052). Clinical outcomes showed no significant differences between group R and group C in terms of the Harris hip score, the Japanese Orthopaedic Association (JOA) score, and the Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ) total score. However, pain complaints that were assessed by patient-reported outcomes using the 36-Item Short Form Health Survey (SF-36) bodily pain and vitality subscales and the JHEQ pain subscale were significantly higher in group R than in group C at the final follow-up. These results suggest that some patients had pain complaint even if the stems were inserted as per the concept after THA with the Revelation Hip System. Trial Registration 911.