Anne Marie Fenstad

Knee arthroplasty in Denmark, Norway and Sweden. A pilot study from the Nordic Arthroplasty Register Association.

Background and purpose The number of national arthroplasty registries is increasing. However, the methods of registration, classification, and analysis often differ. Methods We combined data from 3 Nordic knee arthroplasty registers, comparing demographics, methods, and overall results. Primary arthroplasties during the period 1997–2007 were included. Each register produced a dataset of predefined variables, after which the data were combined and descriptive and survival statistics produced. Results The incidence of knee arthroplasty increased in all 3 countries, but most in Denmark. Norway had the lowest number of procedures per hospital—less than half that of Sweden and Denmark. The preference for implant brands varied and only 3 total brands and 1 unicompartmental brand were common in all 3 countries. Use of patellar button for total knee arthroplasty was popular in Denmark (76%) but not in Norway (11%) or Sweden (14%). Uncemented or hybrid fixation of components was also more frequent in Denmark (22%) than in Norway (14%) and Sweden (2%). After total knee arthroplasty for osteoarthritis, the cumulative revision rate (CRR) was lowest in Sweden, with Denmark and Norway having a relative risk (RR) of 1.4 (95% CI: 1.3–1.6) and 1.6 (CI: 1.4–1.7) times higher. The result was similar when only including brands used in more than 200 cases in all 3 countries (AGC, Duracon, and NexGen). After unicompartmental arthroplasty for osteoarthritis, the CRR for all models was also lowest in Sweden, with Denmark and Norway having RRs of 1.7 (CI: 1.4–2.0) and 1.5 (CI: 1.3–1.8), respectively. When only the Oxford implant was analyzed, however, the CRRs were similar and the RRs were 1.2 (CI: 0.9–1.7) and 1.3 (CI: 1.0–1.7). Interpretation We found considerable differences between the 3 countries, with Sweden having a lower revision rate than Denmark and Norway. Further classification and standardization work is needed to permit more elaborate studies.

Increasing risk of prosthetic joint infection after total hip arthroplasty

Background and purpose The risk of revision due to infection after primary total hip arthroplasty (THA) has been reported to be increasing in Norway. We investigated whether this increase is a common feature in the Nordic countries (Denmark, Finland, Norway, and Sweden). Materials and methods The study was based on the Nordic Arthroplasty Register Association (NARA) dataset. 432,168 primary THAs from 1995 to 2009 were included (Denmark: 83,853, Finland 78,106, Norway 88,455, and Sweden 181,754). Adjusted survival analyses were performed using Cox regression models with revision due to infection as the endpoint. The effect of risk factors such as the year of surgery, age, sex, diagnosis, type of prosthesis, and fixation were assessed. Results 2,778 (0.6%) of the primary THAs were revised due to infection. Compared to the period 1995–1999, the relative risk (with 95% CI) of revision due to infection was 1.1 (1.0–1.2) in 2000–2004 and 1.6 (1.4–1.7) in 2005–2009. Adjusted cumulative 5–year revision rates due to infection were 0.46% (0.42–0.50) in 1995–1999, 0.54% (0.50–0.58) in 2000–2004, and 0.71% (0.66–0.76) in 2005–2009. The entire increase in risk of revision due to infection was within 1 year of primary surgery, and most notably in the first 3 months. The risk of revision due to infection increased in all 4 countries. Risk factors for revision due to infection were male sex, hybrid fixation, cement without antibiotics, and THA performed due to inflammatory disease, hip fracture, or femoral head necrosis. None of these risk factors increased in incidence during the study period. Interpretation We found increased relative risk of revision and increased cumulative 5–year revision rates due to infection after primary THA during the period 1995–2009. No change in risk factors in the NARA dataset could explain this increase. We believe that there has been an actual increase in the incidence of prosthetic joint infections after THA.

Failure rate of cemented and uncemented total hip replacements: register study of combined Nordic database of four nations

Objective To assess the failure rate of cemented, uncemented, hybrid, and reverse hybrid total hip replacements in patients aged 55 years or older. Design Register study. Setting Nordic Arthroplasty Register Association database (combined data from Sweden, Norway, Denmark, and Finland). Participants 347 899 total hip replacements performed during 1995-2011. Main outcome measures Probability of implant survival (Kaplan-Meier analysis) along with implant survival with revision for any reason as endpoint (Cox multiple regression) adjusted for age, sex, and diagnosis in age groups 55-64, 65-74, and 75 years or older. Results The proportion of total hip replacements using uncemented implants increased rapidly towards the end of the study period. The 10 year survival of cemented implants in patients aged 65 to 74 and 75 or older (93.8%, 95% confidence interval 93.6% to 94.0% and 95.9%, 95.8% to 96.1%, respectively) was higher than that of uncemented (92.9%, 92.3% to 93.4% and 93.0%, 91.8% to 94.0%), hybrid (91.6%, 90.9% to 92.2% and 93.9%, 93.1% to 94.5%), and reverse hybrid (90.7%, 87.3% to 93.2% and 93.2%, 90.7% to 95.1%) implants. The survival of cemented (92.2%, 91.8% to 92.5%) and uncemented (91.8%, 91.3% to 92.2%) implants in patients aged 55 to 64 was similar. During the first six months the risk of revision with cemented implants was lower than with all other types of fixation in all age groups. Conclusion The survival of cemented implants for total hip replacement was higher than that of uncemented implants in patients aged 65 years or older. The increased use of uncemented implants in this age group is not supported by these data. However, because our dataset includes only basic information common to all national registers there is potential for residual confounding.

Comparison of the Norwegian Knee Arthroplasty Register and a United States Arthroplasty Registry

Several national total joint arthroplasty registries exist outside of the United States (U.S.) and have been used to compare rates and outcomes of total knee arthroplasty. Within the U.S., regional arthroplasty registries provide an opportunity to compare U.S. practices and outcomes with those of other countries. The purpose of this study was to compare the demographics, choice of implants, techniques, and outcomes of total knee arthroplasties in Norway to those from a large, U.S. integrated health-care system and to determine the feasibility of using aggregate-level data for international registry comparisons. The study sample consisted of 25,004 primary total knee arthroplasties performed in Norway and 56,208 from the Kaiser Permanente health-care system. Summary-level data were used to compare the two cohorts. At the time of the seven-year follow-up, the cumulative survival of the total knee prosthesis was 94.8% for the arthroplasties performed in Norway and 96.3% for those performed at Kaiser Permanente. The primary reasons for revision arthroplasty included infection, instability, pain, and aseptic loosening. Patient characteristics, selection of implants, surgical techniques, and outcomes differed between the cohorts. Harmonization of data elements and definitions is necessary for future international research.

A Scandinavian experience of register collaboration: the Nordic Arthroplasty Register Association (NARA).

BACKGROUND The Nordic (Scandinavian) countries have had working arthroplasty registers for several years. However, the small numbers of inhabitants and the conformity within each country with respect to preferred prosthesis brands and techniques have limited register research. METHODS A collaboration called NARA (Nordic Arthroplasty Register Association) was started in 2007, resulting in a common database for Denmark, Norway, and Sweden with regard to hip replacements in 2008 and primary knee replacements in 2009. Finland joined the project in 2010. A code set was defined for the parameters that all registers had in common, and data were re-coded, within each national register, according to the common definitions. After de-identification of the patients, the anonymous data were merged into a common database. The first study based on this common database included 280,201 hip arthroplasties and the second, 151,814 knee arthroplasties. Kaplan-Meier and Cox multiple regression analyses, with adjustment for age, sex, and diagnosis, were used to calculate prosthesis survival, with any revision as the end point. In later studies, specific reasons for revision were also used as end points. RESULTS We found differences among the countries concerning patient demographics, preferred surgical approaches, fixation methods, and prosthesis brands. Prosthesis survival was best in Sweden, where cement implant fixation was used more commonly than it was in the other countries. CONCLUSIONS As the comparison of national results was one of the main initial aims of this collaboration, only parameters and data that all three registers could deliver were included in the database. Compared with each separate register, this combined register resulted in reduced numbers of parameters and details. In future collaborations of registers with a focus on comparing the performances of prostheses and articulations, we should probably include only the data needed specifically for the predetermined purposes, from registers that can deliver these data, rather than compiling all data from all registers that are willing to participate.

Inferior outcome after hip resurfacing arthroplasty than after conventional arthroplasty: Evidence from the Nordic Arthroplasty Register Association (NARA) database, 1995 to 2007

Background and purpose The reported outcomes of hip resurfacing arthroplasty (HRA) vary. The frequency of this procedure in Denmark, Norway, and Sweden is low. We therefore determined the outcome of HRA in the NARA database, which is common to all 3 countries, and compared it to the outcome of conventional total hip arthroplasty (THA). Methods The risk of non-septic revision within 2 years was analyzed in 1,638 HRAs and compared to that for 172,554 conventional total hip arthroplasties (THAs), using Cox regression models. We calculated relative risk (RR) of revision and 95% confidence interval. Results HRA had an almost 3-fold increased revision risk compared to THA (RR = 2.7, 95% CI: 1.9–3.7). The difference was even greater when HRA was compared to the THA subgroup of cemented THAs (RR = 3.8, CI: 2.7–5.3). For men below 50 years of age, this difference was less pronounced (HRA vs. THA: RR = 1.9, CI: 1.0–3.9; HRA vs. cemented THA: RR = 2.4, CI: 1.1–5.3), but it was even more pronounced in women of the same age group (HRA vs. THA: RR = 4.7, CI: 2.6–8.5; HRA vs. cemented THA: RR = 7.4, CI: 3.7–15). Within the HRA group, risk of non-septic revision was reduced in hospitals performing ≥ 70 HRAs annually (RR = 0.3, CI: 0.1–0.7) and with use of Birmingham hip resurfacing (BHR) rather than the other designs as a group (RR = 0.3, CI: 0.1–0.7). Risk of early revision was also reduced in males (RR = 0.5, CI: 0.2–0.9). The femoral head diameter alone had no statistically significant influence on the early revision rate, but it eliminated the significance of male sex in a combined analysis. Interpretation In general, our results do not support continued use of hip resurfacing arthroplasty. Men had a lower early revision rate, which was still higher than observed for all-cemented hips. Further follow-up is necessary to determine whether HRA might be useful as an alternative in males.

Countrywise results of total hip replacement An analysis of 438,733 hips based on the Nordic Arthroplasty Register Association database

Background and purpose An earlier Nordic Arthroplasty Register Association (NARA) report on 280,201 total hip replacements (THRs) based on data from 1995–2006, from Sweden, Norway, and Denmark, was published in 2009. The present study assessed THR survival according to country, based on the NARA database with the Finnish data included. Material and methods 438,733 THRs performed during the period 1995–2011 in Sweden, Denmark, Norway, and Finland were included. Kaplan-Meier survival analysis was used to calculate survival probabilities with 95% confidence interval (CI). Cox multiple regression, with adjustment for age, sex, and diagnosis, was used to analyze implant survival with revision for any reason as endpoint. Results The 15-year survival, with any revision as an endpoint, for all THRs was 86% (CI: 85.7–86.9) in Denmark, 88% (CI: 87.6–88.3) in Sweden, 87% (CI: 86.4–87.4) in Norway, and 84% (CI: 82.9–84.1) in Finland. Revision risk for all THRs was less in Sweden than in the 3 other countries during the first 5 years. However, revision risk for uncemented THR was less in Denmark than in Sweden during the sixth (HR = 0.53, CI: 0.34–0.82), seventh (HR = 0.60, CI: 0.37–0.97), and ninth (HR = 0.59, CI: 0.36–0.98) year of follow-up. Interpretation The differences in THR survival rates were considerable, with inferior results in Finland. Brand-level comparison of THRs in Nordic countries will be required.

Posterior approach and uncemented stems increases the risk of reoperation after hemiarthroplasties in elderly hip fracture patients

Background Hemiarthroplasties are performed in great numbers worldwide but are seldom registered on a national basis. Our aim was to identify risk factors for reoperation after fracture-related hemiarthroplasty in Norway and Sweden. Material and methods A common dataset was created based on the Norwegian Hip Fracture Register and the Swedish Hip Arthroplasty Register. 33,205 hip fractures in individuals > 60 years of age treated with modular hemiarthroplasties were reported for the period 2005–2010. Cox regression analyses based on reoperations were performed (covariates: age group, sex, type of stem and implant head, surgical approach, and hospital volume). Results 1,164 patients (3.5%) were reoperated during a mean follow-up of 2.7 (SD 1.7) years. In patients over 85 years, an increased risk of reoperation was found for uncemented stems (HR = 2.2, 95% CI: 1.7–2.8), bipolar heads (HR = 1.4, CI: 1.2–1.8), posterior approach (HR = 1.4, CI: 1.2–1.8) and male sex (HR = 1.3, CI: 1.0–1.6). For patients aged 75–85 years, uncemented stems (HR = 1.6, 95% CI: 1.2–2.0) and men (HR = 1.3, CI: 1.1–1.6) carried an increased risk. Increased risk of reoperation due to infection was found for patients aged < 75 years (HR = 1.5, CI: 1.1–2.0) and for uncemented stems. For open surgery due to dislocation, the strongest risk factor was a posterior approach (HR = 2.2, CI: 1.8–2.6). Uncemented stems in particular (HR = 3.6, CI: 2.4–5.3) and male sex increased the risk of periprosthetic fracture surgery. Interpretation Cemented stems and a direct lateral transgluteal approach reduced the risk of reoperation after hip fractures treated with hemiarthroplasty in patients over 75 years. Men and younger patients had a higher risk of reoperation. For the age group 60–74 years, there were no such differences in risk in this material.

Reduction in orthopaedic surgery in patients with rheumatoid arthritis: a Norwegian register-based study

Objectives: The disease course of patients with rheumatoid arthritis (RA) has become milder in recent years. In this study we investigated the incidence of orthopaedic surgery in patients with RA. Method: From the Norwegian Arthroplasty Register we selected joint replacement procedures conducted during the years 1994–2012 (n = 11 337), and from the Norwegian Patient Register we obtained data on synovectomies (n = 4782) and arthrodeses (n = 6022) during 1997–2012. Using Poisson regression we analysed the time trends in the incidence of procedures performed. Results: There was a significant decrease in the incidence of arthroplasty surgery (coefficient of −0.050 per year) and synovectomies (coefficient of −0.10) and a declining trend of arthrodeses in patients with RA in the study periods. The greatest reduction was found in procedures involving the wrist and hand. Conclusions: We found a decrease in orthopaedic surgery in patients with RA that continued into the biologic era and throughout the study period. The general increasing trend in the use of synthetic and biological disease-modifying anti-rheumatic drugs (DMARDs) thus coincides with less joint destruction and an improved long-term prognosis of patients with RA.

Hydroxyapatite coating does not improve uncemented stem survival after total hip arthroplasty!: An analysis of 116,069 THAs in the Nordic Arthroplasty Register Association (NARA) database

Background and purpose — It is still being debated whether HA coating of uncemented stems used in total hip arthroplasty (THA) improves implant survival. We therefore investigated different uncemented stem brands, with and without HA coating, regarding early and long-term survival. Patients and methods — We identified 152,410 THA procedures using uncemented stems that were performed between 1995 and 2011 and registered in the Nordic Arthroplasty Register Association (NARA) database. We excluded 19,446 procedures that used stem brands less than 500 times in each country, procedures performed due to diagnoses other than osteoarthritis or pediatric hip disease, and procedures with missing information on the type of coating. 22 stem brands remained (which were used in 116,069 procedures) for analysis of revision of any component. 79,192 procedures from Denmark, Norway, and Sweden were analyzed for the endpoint stem revision. Unadjusted survival rates were calculated according to Kaplan-Meier, and Cox proportional hazards models were fitted in order to calculate hazard ratios (HRs) for the risk of revision with 95% confidence intervals (CIs). Results — Unadjusted 10-year survival with the endpoint revision of any component for any reason was 92.1% (CI: 91.8–92.4). Unadjusted 10-year survival with the endpoint stem revision due to aseptic loosening varied between the stem brands investigated and ranged from 96.7% (CI: 94.4–99.0) to 99.9% (CI: 99.6–100). Of the stem brands with the best survival, stems with and without HA coating were found. The presence of HA coating was not associated with statistically significant effects on the adjusted risk of stem revision due to aseptic loosening, with an HR of 0.8 (CI: 0.5–1.3; p = 0.4). The adjusted risk of revision due to infection was similar in the groups of THAs using HA-coated and non-HA-coated stems, with an HR of 0.9 (CI: 0.8–1.1; p = 0.6) for the presence of HA coating. The commonly used Bimetric stem (n = 25,329) was available both with and without HA coating, and the adjusted risk of stem revision due to aseptic loosening was similar for the 2 variants, with an HR of 0.9 (CI: 0.5–1.4; p = 0.5) for the HA-coated Bimetric stem. Interpretation — Uncemented HA-coated stems had similar results to those of uncemented stems with porous coating or rough sand-blasted stems. The use of HA coating on stems available both with and without this surface treatment had no clinically relevant effect on their outcome, and we thus question whether HA coating adds any value to well-functioning stem designs.