Antti Eskelinen

Background and purpose: Cemented stem fixation in total hip arthroplasty (THA) reduces early femoral fracture risk in elderly patients, but the optimal method of cup fixation remains controversial. We aimed to compare cup revision risk between cemented and uncemented acetabular cups in patients aged 65 years or older undergoing primary THA.Methods: This registry-based cohort study used data from the Nordic Arthroplasty Register Association (NARA). We included patients aged 65 years or older who underwent primary THA for primary osteoarthritis or sequelae of childhood hip disorders between 1995 and 2018. The primary outcome was all-cause cup revision, with prespecified analyses stratified by age and sex. Cox regression adjusted for age, sex, femoral head size, time period, and nation was used. Follow-up was divided into 3 periods: 0–1, 1–6, and 6–26 years.Results: Among 310,515 patients, cemented cups were associated with a lower risk of all-cause cup revision during the first year (adjusted hazard ratio [aHR] 0.47, 95% confidence interval [CI] 0.41–0.53) and a higher risk at 6–26 years (aHR 1.91, CI 1.72–2.13). In patients aged 80 years or older, the sex-specific adjusted hazard ratios after the first year were close to 1, with wide confidence intervals.Conclusion: Cemented cups were associated with a lower risk of cup revision during the first year across all age groups and a higher risk at 6–26 years in the overall cohort. Among patients aged 80 years or older, we found no evidence of an association between fixation method and cup revision after the first year.

Background and purpose: Robotic-assisted total knee arthroplasty (rTKA) has been proposed to improve component positioning but evidence on its effect on implant survival is limited. We aimed to compare implant survival between rTKA and conventional total knee arthroplasty (cTKA) overall and due to peri-prosthetic joint infection (PJI).Methods: We included all rTKAs performed in Finland from April 2021 until May 2023, all implanted with Triathlon TKA using MAKO robotic-arm assist. Propensity score matching was used to form a control group with similar characteristics for the same time period. Primary survival endpoint was first revision due to any cause within 12 months after the index surgery. PJI and non-PJI revisions were considered secondary outcomes. Kaplan–Meier (KM) analysis and Cox proportional hazards regression were used to assess implant survival and between-group contrasts hazard ratios (HR) with 95% confidence intervals (CIs), respectively.Results: 1,318 fixed bearing rTKAs were compared with a control group of 1,318 cTKAs. Revision-free survival at 12 months after index surgery did not differ between groups. KM estimates were 99.1% (CI 98.5–99.7) for rTKA and 98.6% (CI 98.0–99.3) for cTKA with HR 0.61 (CI 0.28–1.34). The rTKA group demonstrated better PJI-free survival at 12 months (HR 0.29, CI 0.10–0.90). Overall, PJI was the most common reason for revision. At the end of available follow-up, the estimated overall survival was 97.7% (CI 94.9–100.0) for rTKA and 97.9% (CI 96.6–99.2) for cTKA.Conclusion: No difference in all-cause revision risk was observed between rTKA and cTKA groups. However, within the first 12 months, fewer revisions due to PJI occurred in the rTKA group.

Objective: Metal-on-metal (MoM) total hip arthroplasty (THA) and hip-resurfacing arthroplasty were widely used worldwide, including in Finland, at the beginning of the century. This study aimed to assess the long-term cancer risk among all Finnish patients with any kind of MoM hip device and to compare it with that of the general Finnish population and patients with conventional THA. Design: Population-based study. Setting: Nationwide retrospective comparative register-based study. Participants: A total of 18 922 patients who underwent MoM hip arthroplasty (HA) and 29 247 patients who underwent conventional THA (reference cohort) were recorded in the Finnish Arthroplasty Register (FAR) between 2001 and 2013. Data on cases of cancer up to 2021 for these cohorts were extracted from the Finnish Cancer Registry (FCR). Data from the FAR and FCR, as well as information on deaths from the Population Register Centre, were linked using personal identification codes. Main outcome measures: The relative risk of cancer was expressed as the ratio of the observed to expected number of cases in the Finnish population using the standardised incidence ratio (SIR). Poisson regression was used to estimate the relative risk of cancer in the MoM cohort compared with the non-MoM cohort as a ratio of SIRs. Results: The overall risk of cancer in the MoM cohort was decreased compared with that of the general Finnish population (1381 observed versus 1521 expected; SIR 0.91; 95% CI 0.86 to 0.96; p<0.001). The overall cancer risk in the MoM cohort was similar to that of the non-MoM cohort (SIR ratio 0.94; 95% CI 0.88 to 1.00). Basal cell carcinoma and melanoma risks in the MoM cohort were increased compared with that of the general Finnish population (991 observed vs 918 expected; SIR 1.08; 95% CI 1.01 to 1.15; p=0.02, and 167 observed vs 143 expected; SIR 1.17; 95% CI 1.00 to 1.36; p=0.05, respectively). However, the basal cell carcinoma and melanoma risks between the MoM and the non-MoM cohorts were similar (SIR ratio 1.05; 95% CI 0.97 to 1.14, and SIR ratio 1.20; 95% CI 0.97 to 1.47, respectively). Conclusions: MoM HA was not associated with increased overall cancer risk, even in the long term. The melanoma, basal cell carcinoma and prostate findings should be interpreted cautiously because they are increased versus the general population but not versus conventional THA. Longer follow-up periods may be needed to clarify the risks of skin and prostate cancers.

Background and purpose: After total knee arthroplasty (TKA), 10–20% of patients remain unsatisfied. Well-performing clinical prediction models can provide individualized risk estimates and stratification in terms of poor outcomes, resulting in unnecessary surgeries being avoided and patients being counseled preoperatively. We aimed to create a precise, well-performing prediction model for clinical application using different machine learning algorithms to predict those patients who will have residual pain, a low total Oxford Knee Score (OKS) and the patient group who do not achieve minimally clinical important difference (MCID) in OKS 1 year after TKA.Methods: We conducted a retrospective cohort study based on patients who had undergone primary TKA at our institution combined with 751 patient-related variables. The multivariable models used were based on the results of univariate analysis. We used the machine learning method Extreme Gradient Boosting (XGBoost). The discrimination capability of the models was measured with the area under the curve (AUC).Results: 11,755 patients were included in this study. There were 850 (7.2%) patients who experienced persistent pain 1 year after TKA. The AUC was 0.67. For the secondary outcomes, the AUC values were similar. The most important variables in the model were lower preoperative OKS, younger age, valgus malalignment, lower preoperative pain OKS, use of mild opioid, neuropathic pain medicine and thyroxine, and higher body mass index.Conclusion: The prediction models achieved poor AUCs. It seems clear that the prediction of pain and functional outcome after TKA is difficult, even with a large patient cohort combined with 751 patient-related variables and sophisticated machine-learning algorithms.

Background and Aims: A high body mass index (BMI) has traditionally been a strict criterion for surgical eligibility for arthroplasty based on the increased risk for periprosthetic joint infection (PJI). Individuals with obesity are two to four times more likely to undergo joint arthroplasty. There are limited data on how well BMI predicts PJI risk and whether strict BMI-based surgical criteria are justified. Methods: This retrospective single-center cohort study included all primary total hip arthroplasties (THAs) and total knee arthroplasties (TKAs) performed at our institution between 1 January 2008 and 28 November 2023. Survival was analyzed using the Kaplan–Meier method, with PJI as the primary outcome. The association between BMI and PJI was assessed using logistic regression and Cox proportional hazards regression. Results: A total of 54,879 arthroplasties (23,544 hip and 31,335 knee arthroplasties) were included. The median age was 68 years (interquartile range (IQR): 60–75), and 60.0% of patients were female. The risk for PJI was highest in patients with a BMI >45. After THA, the lowest risk for PJI was seen with a BMI <25 (1.0%) and between 25 and 30 (1.1%) after TKA. After THA, a J-shaped association between BMI and PJI was observed in logistic regression analysis, as the risk for PJI increased in patients with both low and high BMIs. A J-shaped association between BMI and PJI was also observed in Cox regression analysis after both TKA and THA. Men had a higher risk for PJI after THA than women, whereas no sex variation was observed after TKA. Conclusion: The risk for PJI does not increase linearly with BMI and the risk differs between women and men. When BMI exceeds 45, risk levels become notably high. Otherwise, the absolute risk differences between different BMI categories are relatively low. Emphasis should be placed on individualized risk assessment and shared decision-making rather than focusing solely on BMI.

Current tissue engineering (TE) strategies depend on destructive analyses to assess tissue maturity. Non-destructive monitoring of tissue maturity would enable optimisation of culture conditions while the TE process is ongoing. In this study, we aimed to utilise near infrared (NIR) spectroscopy as a tool for in situ non-destructive assessment of engineered cartilage properties.We prepared tissue-engineered constructs (TECs) by encapsulating human bone marrow stem/stromal cells (BMSCs) in sodium purified gellan gum. The TECs were cultured in serum-free chondrogenic medium for 28 days. At specific time points, NIR spectral data were acquired from TECs in situ and from the conditioned culture medium. TECs were subjected to reference analyses to determine biochemical and mechanical properties and chondrogenic marker gene expression levels.The study yielded machine learning models trained using NIR spectra collected from TECs and their corresponding media, using reference property measurements as target, to facilitate non-destructive estimation of the properties of previously unseen TECs. Models trained on spectra acquired from the TECs had the best predictions for biochemical composition, mechanical properties and chondrogenic marker gene expression. The analyses highlighted the importance of incorporating spectral information of cell-free hydrogels and culture medium in normalization strategies to improve the prediction of the biomarkers.

Plain radiographs play a key role in the diagnosis of knee osteoarthritis (OA), with the Kellgren-Lawrence (KL) grading system being widely used to assess

Introduction: Lewinnek safe zone has guided optimal acetabular cup positioning for decades. This study aimed to provide new data on dislocation rates after total hip arthroplasty (THA), assess the effects of cup positioning, and evaluate how well the event of dislocation can be predicted. Methods: A total of 1520 THAs performed at our hospital were included. The primary outcome was dislocation. Hips were divided into 20° × 20° areas with 5° intervals based on positioning, and crude dislocation rates were compared. Logistic regression models were used and the results reported using odds ratios with 95% confidence intervals. Predictive performances were assessed with R ² and C-indexes Results: 59 dislocations (48 posterior, 11 anterior) occurred, giving a dislocation rate of 3.9%. Neither a universal nor component-specific safe zone could be created. Cup brand was the most significant factor. Overall predicative values were 0.041–0.134 with R ² values and 0.665–0.775 with C-index values. Conclusions: Dislocation after THA cannot be explained by cup positioning alone. Risk profiles differ between acetabular cup systems, and even though cup design emerged as a key factor, its explanatory power remained modest. These findings emphasize the multifactorial nature of dislocation and the limitations of universal safe zones.

Background: Debridement, antibiotics, and implant retention (DAIR) is the method of choice in the treatment of acute periprosthetic joint infection (PJI). However, the optimal timing of DAIR is somewhat unclear. We assessed the success of DAIR performed during different time intervals after primary total hip arthroplasty (THA) and total knee arthroplasty (TKA) using data from the Finnish Arthroplasty Register (FAR). Methods: There were 178,498 primary operations (78,888 THAs and 99,610 TKAs) from May 2014 to April 2022 recorded in the FAR. Male patients represented 53.4% of the THA group and 55.5% of the TKA group. The most common age group was ≤62 years in the THA group and ≥76 years in the TKA group. All patients were of Finnish ethnicity. A total of 1,014 DAIR procedures were performed within 6 months after the primary arthroplasty. Cases of reoperation after DAIR were followed for 1 year after the DAIR; re-revision due to PJI within 1 year was regarded as a failure of the DAIR treatment. We compared the failure rate of DAIR among 3 time intervals: 0 to 42, 43 to 84, and 85 to 180 days after the primary operation. A Cox regression model was used to assess risk factors for re-revision. Results: In the THA group, the failure rate was 15.1% when DAIR was performed within 42 days, 10.0% when performed at 43 to 84 days, and 31.4% when performed at 85 to 180 days after the primary THA. In the TKA group, the failure rate was 8.9% when DAIR was performed within 42 days, 16.7% when performed at 43 to 84 days, and 9.8% when performed at 85 to 180 days after the primary TKA. Later DAIR was not associated with an increased re-revision risk, compared with the reference of 0 to 42 days, in the THA group (43 to 84 days: hazard ratio [HR], 1.2 [95% confidence interval (CI), 0.6 to 2.2; p = 0.63]; 85 to 180 days: HR, 1.4 [95% CI, 0.6 to 3.0; p = 0.41]). The same was true in the TKA group (43 to 84 days: HR, 1.0 [95% CI, 0.4 to 2.4; p = 0.98]; 85 to 180 days: HR, 1.9 [95% CI, 1.0 to 3.8; p = 0.065]). Conclusions: The failure rate of DAIR may not increase as much as previously thought if performed >6 weeks after primary total joint arthroplasty. Thus, DAIR can also be worth considering as a treatment method for PJI beyond the first 6 weeks postoperatively, depending on the severity of the case. Level of Evidence: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.