Scientific background: Total hip arthroplasty (THA) is considered one of the most successful surgical interventions. In countries under the Organisation for Economic Cooperation and Development (OECD), about 160 primary THA procedures are performed per 100,000 inhabitants. Many available studies and registry reports indicate a >90% survival rate of modern THA at a 10-year follow-up. Despite the general well-being of patients with THA, some patients still complain about the operated hip, and they represent an important burden to the healthcare system.
Aim: This thesis aimed to analyse the reasons for THA failure. Thus, our research was divided into three subsets. Firstly, we aimed to analyse THA failures related to a specific implant. Secondly, the group of aseptic failures was considered, with a focus on pertrochanteric pain syndrome. Thirdly, the group of septic failures was analysed.
Hypotheses:
In the field of failure analysis of individual types of total hip endoprostheses, we tested the following hypotheses:
H1. The survival of the Zweymüller hip endoprosthesis, when followed up for 25 years in a cohort of approximately 2,000 patients from a single hospital, depends on associated factors (surgeon, patient age, gender, operated side and season of the surgery), but does not differ significantly from the survival of this implant in previously published studies.
H2. The survival of the EcoFit® type hip endoprosthesis, when followed up for 12 years in a cohort of approximately 700 patients from a single hospital, does not differ significantly from the survival of the similarly designed Taperloc® implant in previously published studies.
In the field of aseptic failures, our hypotheses were:
H3. The translated and validated VISA-G questionnaire in the Slovenian language allows for the clinical assessment of pertrochanteric pain with adequate internal consistency, test-retest reliability, concurrent validity, and defines the ceiling and floor effects.
H4. A larger offset in total hip arthroplasty is associated with more pronounced pertrochanteric pain assessed with the VISA-G questionnaire and a worse functional outcome, assessed with the Harris Hip Score (HHS), which reversibly improves after revision surgery with the aim of normalizing the offset.
In the field of septic failures, our hypotheses were:
H5. Synovial fluid viscosity in the group of septic failures, defined by the EBJIS criteria, differs significantly from the synovial fluid viscosity of patients with aseptic failure of joint arthroplasty.
H6. Perioparative use of glucocorticoids does not increase the incidence of the periprosthetic joint infection after primary total hip arthroplasty.
H7. Consistent adherence to the septic treatment protocol results in a high cure rate of corynebacterial infections.
Methods: In the field of failure analysis of individual types of total hip endoprostheses, we reviewed operative records for cementless hip endoprostheses of the Zweymüller and EcoFit® types. We analysed the survival of total hip arthroplasty until revision or removal of immobile components using the Kaplan-Meier method, with a minimum follow-up of 5 years. The influence of associated factors on total hip arthroplasty survival was analysed using the Cox regression method.
In the field of aseptic failures, we translated and validated the VISA-G questionnaire in the Slovenian language in accordance with current recommendations. We assessed internal consistency using Cronbach’s alpha, test-retest reliability using the interclass correlation coefficient, and concurrent validity using the Pearson correlation coefficient. We also defined the ceiling and floor effects. We analysed changes in hip joint offset based on X-ray images using the method described by Bjarnaason and Reikeras and determined the relationship with the presence of pertrochanteric pain.
In the field of septic failures, we analysed the viscosity of synovial fluid sampled obtained during revision total joint arthroplasties performed for aseptic and septic reasons. In the analysis of the impact of perioperative glucocorticoid administration on the incidence of periprosthetic joint infection, we followed patients with idiopathic osteoarthritis who underwent- primary total joint arthroplasty for two years after the procedure and recorded the incidence of periprosthetic joint infection. The risk for periprosthetic joint infection was analysed using multivariate logistic regression.
In the analysis of corynebacterial infections, we analysed the cure rate in monomicrobial and polymicrobial groups of corynebacterial periprosthetic joint infections, as well as the cure rate according to the type of surgical treatment used.
Results:
For Zweymüller total hip arthroplasty, the cumulative revision-free survival rates were 92/90/85/81% at 10/15/20/25 years of follow-up, respectively. After adjusting for age, gender, and side of surgery, we found that surgery performed by a less experienced surgeon, the warmer part of the year (spring vs. winter), and the use of components from different manufacturers were significant risk factors with worse implant survival.
The cumulative revision-free survival of the EcoFit® femoral component at 5/10 years of follow-up was 96/94%, respectively. In our cohort, the revision rate of EcoFit® femoral component was 0.46 per 100 component-years, which was not significantly different from the reported values for the Taperloc® femoral component. Higher patient age was a risk factor for revision of the EcoFit® femoral component in our cohort (hazard ratio 1.039, p = 0.048).
For the Slovenian version of the VISA-G questionnaire, we found a test-retest reliability of ICC = 0.977, 95% confidence interval (CI): 0.960–0.986. Internal consistency was assessed with Cronbach’s alpha = 0.79. A statistically significant but low correlation was found between the HHS and VISA-G (r = 0.48).
In the analysis of 123 synovial fluid samples obtained during joint arthroplasty revision, the mean synovial fluid viscosity in the septic group was 8.5 ± 0.4 mPa s, while in the aseptic group it was 103.2 ± 18.8 mPa s (p < 0.05). Synovial fluid viscosity achieved 100% sensitivity and 85.3% specificity, with an AUC of 0.832, 95% CI: 0.739–0.925.
Multivariate logistic regression showed that perioperative dexamethasone use was not associated with an increased risk of periprosthetic joint infection within first two years of follow-up (odds ratio = 0.80, 95% CI: 0.30–1.73; p = 0.603).
Among monomicrobial periprosthetic joint infections caused by corynebacteria, the cure rate was 100%, while in the polymicrobial group 87% of patients were cured. In the polymicrobial group, the success rate of treatment with debridement and implant retention was 90%, while the success rate of the reimplantation protocol was 85%.
Conclusions:
Our study, with 23,255 component-years of follow-up, represents the largest published cohort of patients with third-generation Zweymüller total hip endoprostheses from a single hospital. When analysing the long-term survival of the third-generation of Zweymüller total hip endoprosthesis, environmental factors at the time of primary arthroplasty have an impact, and variability between surgeons is also important for the implant survival.
The long-term survival of the EcoFit® femoral component is comparable to that of the Taperloc® implant. Special caution is advised when using this type of metaphyseal fixation stem in the elderly patients.
The Slovenian version of the VISA-G questionnaire has excellent psychometric properties needed to assess gluteal tendinopathy-related disability in patients with pertrochanteric pain in Slovenia. Therefore, we recommend using the questionnaire to assess trochanteric hip pain.
Synovial fluid viscosity is a more sensitive but slightly less specific diagnostic test than synovial fluid cell count with differential examination in the diagnosis of periprosthetic joint infection.
Our study is the first, in a single centre with a standardized periprosthetic joint infection diagnostics, to show that a single perioperative intravenous dose of dexamethasone is not associated with an increased risk of early or delayed periprosthetic joint infection after total joint arthroplasty in patients with primary osteoarthritis.
Unlike previously published studies on corynebacterial periprosthetic joint infections, our treatment results are favourable, with a cure rate of 91% in our cohort. The cure rate was slightly lower in the polymicrobial group compared to the monomicrobial group, at 87% and 100%, respectively.
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