No difference in implant survival between 28-mm M2a RingLoc metal-on-metal and metal-on-polyethylene total hip arthroplasty: results from the Finnish Arthroplasty Register.

BACKGROUND AND PURPOSE: Long-term outcome of small head (28 mm) metal-on-metal (MoM) total hip arthroplasty (THA) is available mainly for Metasul devices (Sulzer Medica, Winterthur, Switzerland). Biomet MoM THA was frequently used in Finland. Therefore, we assessed long-term survivorship of the M2a 28-mm RingLoc MoM THA (Biomet, Warsaw, IN, USA) and compared it with the metal-on-polyethylene (MoP) RingLoc THA from the same manufacturer. PATIENTS AND METHODS: We conducted a register study based on THAs from the Finnish Arthroplasty Register performed between January 1, 2000 and December 31, 2007. 290 28-mm head M2a MoM THAs and 1,647 28-mm head MoP THAs (reference group) were included. The endpoint was revision for any reason, or revision for aseptic loosening, osteolysis, liner wear, or metallosis as one group. Kaplan-Meier survival estimates were calculated, and revision risks were assessed using a Cox multiple regression model, both with 95% confidence intervals (CI). RESULTS: No difference was found in the 15-year Kaplan-Meier survivorship between the 28-mm head M2a RingLoc MoM THA and the reference group for any reason for revision (87.7% [82.9-92.1] and 83.3% [81.0-85.3], respectively). The adjusted hazard ratio (HR) for any reason for revision for the MoM THA group compared with the reference group was at least equal or better (0.70 [0.48-1.02]). Both groups presented similar survival for revision for aseptic loosening of the cup, osteolysis, liner wear, or metallosis, at 96.2% (92.7-98.0) and 95.4% (93.9-96.5), respectively. INTERPRETATION: In the long-term survival there was no difference between the M2a 28-mm RingLoc MoM THA and 28-mm MoP THA. Further follow-up regimens for M2a 28-mm RingLoc THA patients may be unnecessary, but long-term metal ion and radiological data is needed before any formal suggestions.

Implant survival of 2,723 vitamin E-infused highly crosslinked polyethylene liners in total hip arthroplasty: data from the Finnish Arthroplasty Register.

Background and purpose - The use of crosslinked polyethylene in total hip arthroplasty (THA) has decreased wear remarkably. It has been suggested that the antioxidative effects of vitamin E may enhance the wear properties of polyethylene even further. This study evaluates revision rates between vitamin E-infused polyethylene liners (E1 and E-poly, ZimmerBiomet, Warsaw, IN, USA) versus moderately crosslinked polyethylene (ModXLPE) liners from the same manufacturer used in primary THA.Patients and methods - We conducted a study based on data from the Finnish Arthroplasty Register. The study group consisted of 2,723 THAs with a vitamin E-infused liner and a reference group of 2,707 THAs with a moderately crosslinked polyethylene liner. Survivorship, revision risk, and re-revision causes were compared between groups.Results - The 7-year survival of the vitamin E-infused polyethylene liner group and of the reference group with revision for any reason as the endpoint was comparable (94% [95% CI 92.9-94.9] and 93% [CI 91.9-93.9], respectively). The adjusted hazard ratio (HR) for any revision was similar between the groups (0.7 [CI 0.4-1.1]). When revision for aseptic loosening was studied as the endpoint, the survival for the study group was 99% (CI 98.6-99.4) and for the reference group 99% (CI 98.7-99.5), and the risk of revision was comparable between the study groups (HR 1.3 [CI 0.7-2.5]).Interpretation - After an observation period of 7 years vitamin E-infused liners shows results equal to results obtained with crosslinked polyethylene liners.

Association between fixation type and revision risk in total knee arthroplasty patients aged 65 years and older: a cohort study of 265,877 patients from the Nordic Arthroplasty Register Association 2000-2016.

Background and purpose - The population of the Nordic countries is aging and the number of elderly patients undergoing total knee arthroplasty (TKA) is also expected to increase. Reliable fixation methods are essential to avoid revisions. We compared the survival of different TKA fixation concepts with cemented fixation as the gold standard.Patients and methods - We used data from the Nordic Arthroplasty Register Association (NARA) database of 265,877 unconstrained TKAs performed for patients aged ≥ 65 years with primary knee osteoarthritis between 2000 and 2016. Kaplan-Meier (KM) survival analysis with 95% confidence intervals (CI) and the Cox multiple-regression model were used to compare the revision risk of the fixation methods.Results - Cemented fixation was used in 243,166 cases, uncemented in 8,000, hybrid (uncemented femur with cemented tibia) in 14,248, and inverse hybrid (cemented femur with uncemented tibia) fixation in 463 cases. The 10-year KM survivorship (95% CI) of cemented TKAs was 96% (96 - 97), uncemented 94% (94 - 95), hybrid 96% (96 - 96), and inverse hybrid 96% (94 - 99), respectively. Uncemented TKA was associated with increased risk of revision compared with the cemented TKA; the adjusted hazard ratio was 1.3 (95% CI 1.1 - 1.4).Interpretation - Cemented, hybrid, and inverse hybrid TKAs showed 10-year survival rates exceeding 95%. Uncemented fixation was associated with an increased risk of revision in comparison with cemented fixation. As both hybrid and inverse hybrid fixation were used in only a limited number of TKAs, indicating possibility of selection bias in their favor, cemented TKA still remains the gold standard, as it works reliably in the hands of many.

Similar early mortality risk after cemented compared with cementless total hip arthroplasty for primary osteoarthritis: data from 188,606 surgeries in the Nordic Arthroplasty Register Association database.

Background and purpose - Current literature indicates no difference in 90-day mortality after cemented compared with cementless total hip arthroplasty (THA). However, previous studies are hampered by potential selection bias and suboptimal adjustment for comorbidity confounding. Therefore, we examined the comorbidity-adjusted mortality up to 90 days after cemented compared with cementless THA performed due to osteoarthritis.Patients and methods - Using the Nordic Arthroplasty Register Association database, 2005-2013, we included 108,572 cemented and 80,034 cementless THA due to osteoarthritis. We calculated the Charlson comorbidity index of each patient based on data from national patient registers. The Kaplan-Meier method was used to estimate unadjusted all-cause mortality. Cox regression was used to estimate hazard ratios (HR) with 95% confidence intervals (CI) for 14, 30-, and 90-day mortality comparing cemented with cementless THA, adjusting for age, sex, comorbidity, nation, and year of surgery.Results - Cumulative all-cause mortality within 90 days was 0.41% (CI 0.37-0.46) after cemented and 0.26% (CI 0.22-0.30) after cementless THA. The adjusted HR for cemented vs. cementless fixation was 0.97 (CI 0.79-1.2), and similar risk estimates were obtained for mortality within 14 (adjusted HR 0.91 [CI 0.64-1.3]) and 30 days (adjusted HR 0.94 [CI 0.71-1.3]). We found no clinically relevant differences in mortality between cemented and cementless THA in analyses stratified by age, sex, Charlson comorbidity index, or year of surgery.Interpretation - After adjustment for comorbidity as an important confounder, we observed similar early mortality between the 2 fixation techniques.

The effect of fixation type on the survivorship of contemporary total knee arthroplasty in patients younger than 65 years of age: a register-based study of 115,177 knees in the Nordic Arthroplasty Register Association (NARA) 2000-2016.

Background and purpose - Cemented fixation is regarded as the gold standard in total knee arthroplasty (TKA). Among working-age patients, there has been controversy regarding the optimal fixation method in TKA. To address this issue, we conducted a register-based study to assess the survivorship of cemented, uncemented, hybrid, and inverse hybrid TKAs in patients aged < 65 years.Patients and methods - We used the Nordic Arthroplasty Register Association data of 115,177 unconstrained TKAs performed for patients aged < 65 years with primary knee osteoarthritis over 2000-2016. Kaplan-Meier (KM) survival analysis with 95% confidence intervals (CI) and Cox multiple-regression model with adjustment for age, sex, and nation were used to compare fixation methods in relation to revision for any reason.Results - The 10-year KM survivorship of cemented TKAs was 93.6% (95% CI 93.4-93.8), uncemented 91.2% (CI 90.1-92.2), hybrid 93.0% (Cl 92.2-93.8), and inverse hybrid 96.0% (CI 94.1-98.1). In the Cox model, hybrid TKA showed decreased risk of revision after 6 years' follow-up compared with the reference group (cemented) (hazard ratio [HR] 0.5 [CI 0.4-0.8]), while uncemented TKAs showed increased risk of revision both < 1 year (HR 1.4 [1.1-1.7]) and > 6 years' (HR 1.3 [1.0-1.7]) follow-up compared to the reference.Interpretation - Both cemented and hybrid TKAs had 10-year survival rates exceeding 92->93% in patients aged < 65 years. Cemented TKA, however, was used in the vast majority (89%) of the operations in the current study. As it performs reliably in the hands of many, it still deserves the status of gold standard for TKA in working-age patients.

No Increase in Survival for 36-mm versus 32-mm Femoral Heads in Metal-on-polyethylene THA: A Registry Study.

BACKGROUND: During the past decade, the 32-mm head has replaced the 28-mm head as the most common head size used in primary THA in many national registries, and the use of 36-mm heads has also increased. However, it is unclear whether 32-mm and 36-mm heads decrease the revision risk in metal-on-polyethylene (MoP) THA compared with 28-mm heads. QUESTIONS/PURPOSES: (1) In the setting of the Nordic Arthroplasty Register Association database, does the revision risk for any reason differ among 28-, 32-, and 36-mm head sizes in patients undergoing surgery with MoP THA? (2) Does the revision risk resulting from dislocation decrease with increasing head diameter (28-36 mm) in patients undergoing surgery with MoP THA in the same registry? METHODS: Data were derived from the Nordic Arthroplasty Register Association database, a collaboration among the national arthroplasty registries of Denmark, Finland, Norway, and Sweden. Patients with primary osteoarthritis who had undergone primary THA with a 28-, 32-, or 36-mm MoP bearing from 2003 to 2014 were included. Patients operated on with dual-mobility cups were excluded. In patients with bilateral THA, only the first operated hip was included. After applying the inclusion criteria, the number of patients and THAs with a complete data set was determined to be 186,231, which accounted for 51% of all hips (366,309) with primary osteoarthritis operated on with THA of any head size and bearing type during the study observation time. Of the included patients, 60% (111,046 of 186,231) were women, the mean age at surgery was 70 (± 10) years, and the median followup was 4.5 years (range, 0-14 years). A total of 101,094 patients had received a 28-mm, 57,853 a 32-mm, and 27,284 a 36-mm head with 32 mm used as the reference group. The revision of any component for any reason was the primary outcome and revision for dislocation was the secondary outcome. Very few patients are estimated to be lost to followup because emigration in the population of interest (older than 65-70 years) is rare. A Kaplan-Meier analysis was used to estimate THA survival for each group, whereas Cox regression models were fitted to calculate hazard ratios (HRs) with 95% confidence intervals (CIs) for THA revision comparing the 28- and 36-mm head diameters with the 32-mm head diameters adjusting for age, sex, year of surgery, type of cup and stem fixation, polyethylene type (crosslinked versus conventional), and surgical approach. RESULTS: In the adjusted Cox regression model, there was no difference in the adjusted risk for revision for any reason between patients with 28-mm (HR, 1.06; 95% CI, 0.97-0.16) and 32-mm heads, whereas the risk of revision was higher for patients with 36-mm heads (HR, 1.14; 95% CI, 1.04-1.26) compared with patients with 32-mm heads. Patients with 28-mm heads had a higher risk of revision for dislocation (HR, 1.67; 95% CI, 1.38-1.98) compared with 32 mm, whereas there was no difference between patients with 36-mm (HR, 0.85; 95% CI, 0.70-1.02) and 32-mm heads. CONCLUSIONS: After adjusting for relevant confounding variables, we found no benefits for 32-mm heads against 28 mm in terms of overall revision risk. However, when dislocation risk is considered, 32-mm heads would be a better option, because they had a lower risk of revision resulting from dislocation. There were no benefits with the use of 36-mm heads over 32 mm, because the transition from 32 to 36 mm was associated with a higher risk of revision for all reasons, which was not accompanied by a decrease in the risk of revision resulting from dislocation. The use of 32-mm heads appears to offer the best compromise between joint stability and other reasons for revision in MoP THA. Further studies with longer followup, especially of 36-mm heads, as well as better balance of confounders across head sizes and better control of patient-related risk factors for THA revision are needed. LEVEL OF EVIDENCE: Level III, therapeutic study.

Survival of uncemented cups from a single manufacturer implanted from 1985 to 2013: Finnish Arthroplasty Register data.

INTRODUCTION: Total hip arthroplasty (THA) with uncemented implants has been a relatively common procedure in Finland during the recent decades. The most common brand of uncemented implants was chosen for further analysis to study the survivorship of this uncemented cup design in comparison to cemented references. PATIENTS, MATERIALS AND METHODS: Since 1980, The Finnish Arthroplasty Register has collected information on THAs on a national level. This study was based on information of THAs recorded in the Finnish Arthroplasty Register from 1985 to 2013. If patient had undergone bilateral THA, only the first one was included. Altogether, 49,289 THAs were included. RESULTS: The overall 10-year implant survivorship of uncemented implants was 84.3% (95% CI 83.5-85.0%) and of cemented implants 90.6% (90.2-90.0%). The 10-year survival of the contemporary uncemented implants was 90.8% (94.0-95.5%) and 88.5% (84.2-91.7%). The most recently introduced uncemented cup designs had good survivorship rates at 5 years; 10-year survival data are not yet available. CONCLUSIONS: We found that modern uncemented cup designs may provide good long-term survivorship rates comparable with the gold standard of cemented cups. However, polyethylene wear, liner problems and periosthetic osteolysis may still occur, also with modern uncemented acetabular components.

Implant survival of the most common cemented total hip devices from the Nordic Arthroplasty Register Association database.

Background and purpose - According to previous Nordic Arthroplasty Register Association (NARA) data, the 10-year implant survival of cemented total hip arthroplasties (THAs) is 94% in patients aged 65-74 and 96% in patients aged 75 or more. Here we report a brand-level comparison of cemented THA based on the NARA database, which has not been done previously. Patients and methods - We determined the rate of implant survival of the 9 most common cemented THAs in the NARA database. We used Kaplan-Meier analysis with 95% CI to study implant survival at 10 and 15 years, and Cox multiple regression to assess survival and hazard ratios (HRs), with revision for any reason as endpoint and with adjustment for age, sex, diagnosis, and femoral head material. Results - Spectron EF THA (89.9% (CI: 89.3-90.5)) and Elite THA (89.8% (CI: 89.0-90.6)) had the lowest 10-year survivorship. Lubinus (95.7% survival, CI: 95.5-95.9), MS 30 (96.6%, CI: 95.8-97.4), and C-stem THA (95.8%, CI: 94.8-96.8) had a 10-year survivorship of at least 95%. Lubinus (revision risk (RR) = 0.77, CI: 0.73-0.81), Müller (RR =0.83, CI: 0.70-0.99), MS-30 (RR =0.73, CI: 0.63-0.86), C-stem (RR =0.70, CI: 0.55-0.90), and Exeter Duration THA (RR =0.84, CI: 0.77-0.90) had a lower risk of revision than Charnley THA, the reference implant. Interpretation - The Spectron EF THA and the Elite THA had a lower implant survival than the Charnley, Exeter, and Lubinus THAs. Implant survival of the Müller, MS 30, CPT, and C-stem THAs was above the acceptable limit for 10-year survival.

Hydroxyapatite coating does not improve uncemented stem survival after total hip arthroplasty!

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.

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.

Cementless total hip arthroplasty for primary osteoarthritis in patients aged 55 years and older.

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.

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.

Cemented versus cementless total hip replacements in patients fifty-five years of age or older with rheumatoid arthritis.

BACKGROUND: results obtained from single-center studies indicate that a cemented total hip replacement is the treatment of choice for the management of patients over fifty-five years of age with rheumatoid arthritis. The aim of this study was to analyze population-based survival rates for cemented and cementless total hip replacements in patients aged fifty-five years or over with rheumatoid arthritis in Finland. METHODS: between 1980 and 2006, a total of 6000 primary total hip replacements performed for the management of rheumatoid arthritis in patients who were fifty-five years of age or older were entered in the Finnish Arthroplasty Registry. 4019 of them fulfilled our inclusion criteria and were subjected to analysis. The implants were classified into one of three possible groups: (1) a cementless group (a noncemented proximally porous-coated stem and a noncemented porous-coated press-fit cup), (2) a cemented group 1 (a cemented, loaded-taper stem combined with a cemented, all-polyethylene cup), or (3) a cemented group 2 (a cemented, composite-beam stem with a cemented, all-polyethylene cup). RESULTS: cementless stems and cups, analyzed separately, had a significantly lower risk of revision for aseptic loosening than cemented implants in patients who were fifty-five years of age or older with rheumatoid arthritis. The fifteen-year survival rate of cementless total hip replacements (80%) was comparable with the rates of the cemented groups (86% in cemented group 1 and 79% in cemented group 2) when revisions for any reason were used as the end point. CONCLUSIONS: cementless and cemented total hip replacements produced comparable long-term results in patients who were fifty-five years of age or older with rheumatoid arthritis. LEVEL OF EVIDENCE: therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

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.