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 6,080 Tritanium Cups in Primary Total Hip Arthroplasty: Data from the Finnish Arthroplasty Register from 2009 to 2017.

BACKGROUND: To enhance osseointegration in total hip arthroplasty (THA), ultraporous or highly porous-coated cups were introduced. Implant survival data on these new devices have been scarce. The aim of our study was to assess the survivorship of ultraporous Tritanium cups (Stryker) in a population-based register study. METHODS: In this study, we collected data on 6,080 primary THAs using a Tritanium cup and 25,670 THAs using a conventional cup (control group) from the Finnish Arthroplasty Register; these procedures were performed from January 1, 2009, to December 31, 2017. We calculated the Kaplan-Meier survival estimates with 95% confidence intervals (CIs). The end point was revision for any reason or for aseptic loosening of the cup. The revision risks were assessed with use of the Cox multiple regression model. The variables assessed in the Cox model were femoral head size, age group, involved side, operation year, sex, diagnosis, and fixation of the stem. The proportional hazards assumption of the Cox model was not fulfilled, so the follow-up time was divided into 3 time periods: 0 to 2 years, >2 to 4 years, and >4 years. RESULTS: When comparing the 2 groups with regard to revision for any reason, the 5-year Kaplan-Meier survivorship of the Tritanium group (94.7% [95% CI, 94.0% to 95.4%]) was inferior to that of the control group (96.0% [95% CI, 95.7% to 96.3%]). In the Cox regression analysis of the 2 groups for the time period of >4 years, the Tritanium group had an increased risk of revision for any reason compared with the control group (hazard ratio [HR], 3.12 [95% CI, 1.82 to 5.35]; p < 0.001). With regard to revision for aseptic loosening of the cup, the Tritanium group had an increased risk of revision compared with the control group for both 0 to 2 years (HR, 3.80 [95% CI, 1.76 to 8.24]; p < 0.001) and >2 to 4 years (HR, 11.2 [95% CI, 3.28 to 38.0]; p < 0.001). CONCLUSIONS: There was no advantage to using the ultraporous-coated Tritanium cup for primary THA compared with conventional uncemented cups. However, wide CIs for some HR estimates may point to a lack of precision. Therefore, further research on subject is needed. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Early postoperative mortality similar between cemented and uncemented hip arthroplasty: a register study based on Finnish national data.

Background and purpose - Implant survival of cemented total hip arthroplasty (THA) in elderly patients is higher than that of uncemented THA. However, a higher mortality rate in patients undergoing cemented THA compared with uncemented or hybrid THA has been reported. We assessed whether cemented fixation increases peri- or early postoperative mortality compared with uncemented and hybrid THA. Patients and methods - Patients with osteoarthritis who received a primary THA in Finland between 1998 and 2013 were identified from the PERFECT database of the National Institute for Health and Welfare in Finland. Definitive data on fixation method and comorbidities were available for 62,221 THAs. Mortality adjusted for fixation method, sex, age group, and comorbidities among the cemented, uncemented, and hybrid THA was examined using logistic regression analysis. Reasons for cardiovascular death within 90 days since the index procedure were extracted from the national Causes of Death Statistics and assessed separately. Results - 1- to 2-day adjusted mortality after cemented THA was comparable to that of the uncemented THA group (OR 1.2; 95% CI 0.24-6.5). 3- to 10-day mortality in the cemented THA group was comparable to that in the uncemented THA group (OR 0.54; CI 0.26-1.1), and in the hybrid THA group (OR 0.64, CI 0.25-1.6). Pulmonary embolism or cardiovascular reasons as a cause of death were not over-represented in the cemented THA group. Interpretation - Early peri- and postoperative mortality in the cemented THA group was similar compared with that of the hybrid and uncemented groups.

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.