Acta Orthopaedica 2011; 82 (6): 639–645 639 Is reverse hybrid hip replacement the solution? 3,963 primary hip replacements with cemented cup and uncemented stem, from the Norwegian Arthroplasty Register Einar Lindalen1, Leif I Havelin2,3, Lars Nordsletten4, Eva Dybvik2, Anne M Fenstad2, Geir Hallan2, Ove Furnes2,3, Øystein Høvik1, and Stephan M Röhrl4 1Department of Orthopaedic Surgery, Lovisenberg Deaconal Hospital, Oslo; 2Department of Orthopaedic Surgery, Norwegian Arthroplasty Register, Haukeland University Hospital, Bergen; 3Section of Orthopaedic Surgery, Department of Surgical Sciences, University of Bergen; 4Orthopaedic Department, Oslo University Hospital, University of Oslo, Oslo, Norway Correspondence EL: eli@lds.no Submitted 11-01-05 Accepted 11-06-08 Background and purpose Reverse hybrid hip replacement uses a cemented all-polyethylene cup and an uncemented stem. Despite increasing use of this method in Scandinavia, there has been very little documentation of results. We have therefore analyzed the results from the Norwegian Arthroplasty Register (NAR), with up to 10 years of follow-up. Patients and methods The NAR has been collecting data on total hip replacement (THR) since 1987. Reverse hybrid hip replace- ments were used mainly from 2000. We extracted data on reverse hybrid THR from this year onward until December 31, 2009, and compared the results with those from cemented implants over the same period. Specific cup/stem combinations involving 100 cases or more were selected. In addition, only combinations that were taken into use in 2005 or earlier were included. 3,963 operations in 3,630 patients were included. We used the Kaplan-Meier method and Cox regression analysis for estimation of prosthesis survival and relative risk of revision. The main endpoint was revision for any cause, but we also performed specific analyses on different reasons for revision. Results We found equal survival to that from cemented THR at 5 years (cemented: 97.0% (95% CI: 96.8–97.2); reverse hybrid: 96.7% (96.0–97.4)) and at 7 years (cemented: 96.0% (95.7–96.2); reverse hybrid: 95.6% (94.4–96.7)). Adjusted relative risk of revi- sion of the reverse hybrids was 1.1 (0.9–1.4). In patients under 60 years of age, we found similar survival of the 2 groups at 5 and 7 years, with an adjusted relative risk of revision of reverse hybrids of 0.9 (0.6–1.3) compared to cemented implants. Interpretation With a follow-up of up to 10 years, reverse hybrid THRs performed well, and similarly to all-cemented THRs from the same time period. The reverse hybrid method might therefore be an alternative to all-cemented THR. Longer follow-up time is needed to evaluate whether reverse hybrid hip replacement has any advantages over all-cemented THR.  The reverse hybrid method (also known as “inverse hybrid”) uses a cemented all-polyethylene cup in combination with an uncemented stem. This method is partly based on good clini- cal results of cemented cups and of some uncemented stems in the Norwegian Arthroplasty Register (NAR) (Havelin et al. 2000a,b, Hallan et al. 2007). The register has also shown that some uncemented femoral stems may have better long–term results (> 10 years) than cemented stems in patients 60 years of age or younger. Based on these findings, the NAR suggested 10 years ago that the use of cemented cups in combination with uncemented stems might be justified in young patients (Havelin et al. 2000a). In the Swedish Hip Arthroplasty Reg- ister, the performance of uncemented THR was found to be inferior to that of cemented THR (Hailer et al. 2010). The authors of that study found that cemented cups performed better than uncemented cups and that uncemented femoral stems had better survival than cemented stems, with aseptic loosening as endpoint. In the Finnish Arthroplasty Registry, Mäkelä et al. (2010) found better long-term survival regarding aseptic loosening for the best performing types of cementless stems compared to the cemented reference group, in the age group 55–74 years. McNally et al. (2000) studied survival of the Furlong HA coated femoral stem in combination with a cemented ultra- high-density polyethylene cup at 10–11 years, and found values of 99% for the stem and 95% for the cup. Alho et al. (2000) reported results with cemented Lubinus cups and unce- mented Furlong stems, and they also pointed out the possibil- ity of using the principle of reverse hybrid arthroplasty. We are not aware of any other reports on the reverse hybrid method. In a reverse hybrid THR, an uncemented stem and a mod- ular head are most often combined with a cemented cup of another name or from another company. Combining implants that are not designed to fit each other might theoretically lead Open Access - This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the source is credited. DOI 10.3109/17453674.2011.623569