Keijo Mäkelä

Total Hip Arthroplasty for Primary Osteoarthritis in Patients Fifty-five Years of Age or Older: An Analysis of the Finnish Arthroplasty Registry

BACKGROUND According to the long-term results obtained from the Scandinavian arthroplasty registries, cemented total hip replacement has been the treatment of choice for osteoarthritis of the hip in elderly patients. The aim of the present study was to analyze population-based survival rates of the cemented and cementless total hip replacements performed for primary osteoarthritis in patients fifty-five years of age or older in Finland. METHODS From 1980 to 2004, a total of 50,968 primary total hip replacements that met our criteria were entered in the Finnish Arthroplasty Registry. The success rate of different implant groups was analyzed. The implants included were classified in one of the following four groups: implants with a cementless, straight, proximally circumferentially porous-coated stem and a modular, porous-coated press-fit cup (cementless group 1); implants with a cementless, anatomic, proximally circumferentially porous-coated and/or hydroxyapatite-coated stem with a modular, porous-coated and/or hydroxyapatite-coated press-fit cup (cementless group 2); a hybrid total hip replacement consisting of a cemented stem combined with a modular, press-fit cup (the hybrid group); and a cemented loaded-taper or composite-beam stem combined with an all-polyethylene cup (the cemented group). RESULTS Cementless total hip replacements, as well as cementless stems and cups analyzed separately, had a significantly reduced risk of revision for aseptic loosening compared with cemented hip replacements (p < 0.001). When revision for any reason was the end point in survival analyses, however, there were no significant differences among the groups. In patients between the ages of fifty-five and sixty-four years, the fifteen-year survival rates of the two cementless groups (78% and 80%) were higher than that of the cemented group (71%) with revision for aseptic loosening as the end point. In patients who were sixty-five to seventy-four years old, the fifteen-year survival rate of the implants in cementless group 1 was 94%, while cemented total hip replacements had an 85% survival rate. In patients who were seventy-five years old or more, no significant differences were detected among the total hip replacement groups; all of them had survivorship of >90% at ten years. CONCLUSIONS In patients who were fifty-five years of age or older, the long-term survival of cementless total hip replacements was comparable with that of cemented replacements. In patients who were fifty-five to seventy-four years old, straight porous-coated cementless stems had better long-term survival than the cemented stems. In patients who were seventy-five years of age and older, there were no significant differences in the results. Multiple wear-related revisions of the cementless cups in the present study indicate that excessive polyethylene wear was a major clinical problem with modular cementless cups in all age groups. LEVEL OF EVIDENCE Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

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.

Statistical analysis of arthroplasty data II. Guidelines

It is envisaged that guidelines for statistical analysis and presentation of results will improve the quality and value of research. The Nordic Arthroplasty Register Association (NARA) has therefore developed guidelines for the statistical analysis of arthroplasty register data. The guidelines are divided into two parts, one with an introduction and a discussion of the background to the guidelines (, see pages x-y in this issue), and this one with a more technical statistical discussion on how specific problems can be handled. This second part contains (1) recommendations for the interpretation of methods used to calculate survival, (2) recommendations on howto deal with bilateral observations, and (3) a discussion of problems and pitfalls associated with analysis of factors that influence survival or comparisons between outcomes extracted from different hospitals.

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.

Risk of cancer with metal-on-metal hip replacements: population based study

Objective To assess the risk of cancer associated with modern primary metal-on-metal hip replacements. Design Population based study. Setting Nationwide retrospective comparative register. Participants 10 728 patients who underwent metal-on-metal total hip arthroplasty and 18 235 patients who underwent conventional metal-on-polyethylene, ceramic-on-polyethylene, and ceramic-on-ceramic total hip arthroplasty (the non-metal-on-metal cohort) in the Finnish Arthroplasty Register 2001-10. Data on cancer cases up to 2010 for these cohorts were extracted from the Finnish Cancer Registry. Main outcome measures The relative risk of cancer was expressed as the ratio of observed to expected number of cases from the Finnish population—that is, the standardised incidence ratio. The relative risk of cancer in the metal-on-metal cohort compared with the non-metal-on-metal cohort was estimated with analyses of these ratios and Poisson regression. Results The overall risk of cancer in patients with metal-on-metal hip implants was similar to that in the Finnish population (378 observed v 400 expected, standardised incidence ratio 0.95, 95% confidence interval 0.85 to 1.04). The overall risk of cancer in patients with metal-on-metal hip implants was also no higher than in patients who had received non-metal-on-metal hip implants (relative risk 0.92, 0.81 to 1.05). Conclusions Metal-on-metal hip replacements are not associated with an increased overall risk of cancer during a mean follow-up of four years.

Cemented total hip replacement for primary osteoarthritis in patients aged 55 years or older: RESULTS OF THE 12 MOST COMMON CEMENTED IMPLANTS FOLLOWED FOR 25 YEARS IN THE FINNISH ARTHROPLASTY REGISTER

We have analysed from the Finnish Arthroplasty Register the long-term survivorship of the 12 most commonly-used cemented implants between 1980 and 2005 in patients aged 55 years or older with osteoarthritis. Only two designs of femoral component, the Exeter Universal and the Müller Straight femoral component had a survivorship of over 95% at ten years with revision for aseptic loosening as the endpoint. At 15 years of the femoral and acetabular component combinations, only the Exeter Universal/Exeter All-poly implant had a survival rate of over 90% with revision for aseptic loosening as the endpoint. In the subgroup of patients aged between 55 and 64 years, survivorship overall was less than 90% at ten years. The variation in the long-term rates of survival of different cemented hip implants was considerable in patients aged 55 years or older. In those aged between 55 and 64 years, none of the cemented prostheses studied yielded excellent long-term survival rates (> or = 90% at 15 years).

Results of 3,668 primary total hip replacements for primary osteoarthritis in patients under the age of 55 years.

Background and purpose In a previous study based on the Finnish Arthroplasty Register, the survival of cementless stems was better than that of cemented stems in younger patients. However, the survival of cementless cups was poor due to osteolysis. In the present study, we analyzed population-based survival rates of the cemented and cementless total hip replacements in patients under the age of 55 years with primary osteoarthritis in Finland. Patients and methods 3,668 implants fulfilled our inclusion criteria. The previous data included years 1980–2001, whereas the current study includes years 1987–2006. The implants were classified in 3 groups: (1) implants with a cementless, straight, proximally circumferentially porous-coated stem and a porous-coated press-fit cup (cementless group 1); (2) implants with a cementless, anatomic, proximally circumferentially porous-coated stem, with or without hydroxyapatite, and a porous-coated press-fit cup with or without hydroxyapatite (cementless group 2); and (3) a cemented stem combined with a cemented all-polyethylene cup (the cemented group). Analyses were performed separately for 2 time periods: those operated 1987–1996 and those operated 1997–2006. Results The 15-year survival for any reason of cementless total hip replacement (THR) group 1 operated on 1987–1996 (62%; 95% CI: 57–67) and cementless group 2 (58%; CI: 52–66) operated on during the same time period was worse than that of cemented THRs (71%; CI: 62–80), although the difference was not statistically significant. The revision risk for aseptic loosening of cementless stem group 1 operated on 1987–1996 (0.49; CI: 0.32–0.74) was lower than that for aseptic loosening of cemented stems (p = 0.001). Interpretation Excessive wear of the polyethylene liner resulted in numerous revisions of modular cementless cups. The outcomes of total hip arthroplasty appear to have been relatively unsatisfactory for younger patients in Finland.

Unicompartmental Knee Arthroplasty Survivorship is Lower Than TKA Survivorship: A 27-year Finnish Registry Study

BackgroundBalancing the relative advantages and disadvantages of unicompartmental knee arthroplasties (UKAs) against those for TKAs can be challenging. Survivorship is one important end point; arthroplasty registers repeatedly report inferior midterm survival rates, but longer-term data are sparse. Comparing survival directly by using arthroplasty register survival reports also may be inadequate because of differences in indications, implant designs, and patient demographics in patients having UKAs and TKAs.Questions/purposesThe aims of this study were to assess the survivorship of UKA in the context of one large, northern European registry, and to compare the rates of survivorship with those of cemented TKAs performed for primary knee osteoarthritis during the same 27-year period.MethodsFrom the Finnish Arthroplasty Register, we obtained the data for 4713 patients undergoing UKAs for primary osteoarthritis (mean age, 63.5 years; minimum followup, 0 years; mean, 6.0 years; range, 0–24 years) who had surgical revision between 1985 and 2011. From this cohort, we calculated the Kaplan-Meier survivorship for revision performed for any reason and compared it with the survivorship of 83,511 patients (mean age, 69.5 years; minimum followup 0 years; mean, 6.4 years; range, 0–27 years) with TKAs treated for primary osteoarthritis during the same period. Data were adjusted for age and sex in a comparative analysis.ResultsKaplan-Meier survivorship of UKAs was 89.4% at 5 years, 80.6% at 10 years, and 69.6% at 15 years; the corresponding rates for TKAs were 96.3%, 93.3%, and 88.7%, respectively. UKAs had inferior long-term survivorship compared with cemented TKAs, even after adjusting for the age and sex of the patients (hazard ratio 2.2, p < 0.001).ConclusionsA UKA offers tempting advantages compared with a TKA; however, the revision frequency for UKAs in widespread use, as measured in a large, national registry, was poorer than that of TKAs. When choosing between a UKA and a TKA, patients should be informed of advantages of both procedures, but they also should be advised about the generally higher revision risk after UKA.Level of EvidenceLevel III, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.

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.

Cementless total hip arthroplasty for primary osteoarthritis in patients aged 55 years and older Results of the 8 most common cementless designs compared to cemented reference implants in the Finnish Arthroplasty Register

Background Cemented total hip arthroplasty has been the treatment of choice for elderly patients with osteoarthritis. We analyzed survival rates of the most common cementless designs used in this age group in Finland. Patients and methods Inclusion criteria permitted 10,310 replacements (8 designs) performed in patients aged 55 years or older to be selected for evaluation. The risk of revision of each of the 8 implants was compared with that of a group comprising 3 cemented designs as the reference (9,549 replacements). Survival analyses were performed overall and separately for 3 age cohorts: 55–64 years (6,781 replacements), 65–74 years (8,821 replacements), and 75 years or older (4,257 replacements). Results In all patients aged 55 years or more, the Bi-Metric stem had a higher survival rate for aseptic loosening at 15 years than the cemented reference group: 96% (95% CI: 94–98) vs. 91% (CI: 90–92). However, the 15-year survival rates of the Bi-Metric/Press-Fit Universal (71% (CI: 67–75)) and the Anatomic Mesh/Harris-Galante II (72% (CI: 67–78)) total hip replacements were lower than that of the reference group (86% (CI: 84–87)). Information was scarce for patients aged 75 years or more. Interpretation Cementless proximal porous-coated stems are a good option for elderly patients. Even though biological fixation is a reliable fixation method in THA, polyethylene wear and osteolysis remain a serious problem for cementless cup designs with unplugged screw holes and low-quality liners.