Increasing risk of revision due to infection after primary total hip arthroplasty: results from the Nordic Arthroplasty Register Association

Choice of Bearings Influences the Implant Survival of Total Hip Arthroplasty in Patients Who Have Osteoarthritis Aged 55 Years or More: Results of 158,044 Patients from the Nordic Arthroplasty Register Association from 2005 to 2017

BACKGROUND

The aim of our study was to compare implant survival rates of different total hip arthroplasty (THA) bearings in the Nordic Arthroplasty Register Association.

METHODS

All conventional primary THAs performed between 2005 and 2017 in patients over 55 years of age who had primary osteoarthritis were studied. Metal-on-highly crosslinked polyethylene (MoXLP), ceramic-on-highly crosslinked polyethylene (CoXLP), ceramic-on-ceramic (CoC), and metal-on-metal (MoM) bearings were included. The outcome was a revision. Kaplan-Meier (KM) estimates were calculated at 5 and 10 years. The risk for revision was analyzed using a flexible parametric survival model (FPSM) adjusted for nation, age, sex, femoral head size, and femoral fixation.

RESULTS

A total of 158,044 THAs were included. The 5-year KM estimates were 95.9% (95% confidence interval [CI] 95.8 to 96.1) in MoXLP, 95.8% (95.6 to 96.1) in CoXLP, 96.7% (96.4 to 97.0) in CoC, and 93.9% (93.5 to 94.4) in MoM. The 10-year KM estimates were 94.2% (94.0 to 94.5) in MoXLP, 94.3% (93.9 to 94.8) in CoXLP, 95.4% (95.0 to 95.9) in CoC, and 85.5% (84.9 to 86.2) in MoM. Compared with MoXLP, the adjusted risk for revision was lower in CoC (hazard ratio [HR] 0.6, CI 0.5 to 0.6), similar in CoXLP (1.0, 0.9 to 1.0), and higher in MoM (1.3, 1.2 to 1.4).

CONCLUSIONS

We found that MoXLP, CoXLP, and CoC bearings evinced comparably high implant survival rates up to 10 years, and they can all be regarded as safe options in this patient group. The MoM bearings were associated with clearly lower survivorship. The CoC bearings had the highest implant survival and a lower adjusted risk for revision compared with XLP bearings.

How good are surgeons at disclosing periprosthetic joint infection at the time of revision, based on pre- and intra-operative assessment? A study on 16,922 primary total hip arthroplasties reported to the Norwegian Arthroplasty Register

BACKGROUND AND PURPOSE

Revision due to infection, as reported to the Norwegian Arthroplasty Register (NAR), is a surrogate endpoint to periprosthetic joint infection (PJI). We aimed to find the accuracy of the reported causes of revision after primary total hip arthroplasty (THA) compared with PJI to see how good surgeons were at disclosing infection, based on pre- and intraoperative assessment.

PATIENTS AND METHODS

We investigated the reasons for revision potentially caused by PJI following primary THA: infection, aseptic loosening, prolonged wound drainage, and pain only, reported to the NAR from surgeons in the region of Western Norway during the period 2010-2020. The electronic patient charts were investigated for information on clinical assessment, treatment, biochemistry, and microbiological findings. PJI was defined in accordance with the Musculoskeletal Infection Society (MSIS) definition. Sensitivity, specificity, and accuracy were calculated.

RESULTS

363 revisions in the NAR were eligible for analyses. Causes of revision were (reported/validated): infection (153/177), aseptic loosening (139/133), prolonged wound drainage (37/13), and pain only (34/40). The sensitivity for reported revision due to infection compared with PJI was 80%, specificity was 94%, and accuracy-the surgeons' ability to disclose PJI or non-septic revision at time of revision-was 87%. The accuracy for the specific revision causes was highest for revision due to aseptic loosening (95%) and pain only (95%), and lowest for revision due to prolonged wound drainage (86%).

CONCLUSION

The accuracy of surgeon-reported revisions due to infection as representing PJI was 87% in the NAR. Our study shows the importance of systematic correction of the reported cause of revision in arthroplasty registers, after results from adequately taken bacterial samples.

Incidence of Rifampicin Resistance in Periprosthetic Joint Infection: A Single-Centre Cohort Study on 238 Patients

BACKGROUND

Rifampicin is a pillar in the treatment of periprosthetic joint infection (PJI). However, rifampicin resistance is an increasing threat to PJI treatment. This study explores the incidence of rifampicin-resistant bacteria over time in a Swedish tertiary referral centre and the association of rifampicin resistance with infection-free survival after PJI.

METHODS

The study included 238 staphylococcal PJIs treated between 2001 and 2020 for which susceptibility data for rifampicin were available. Data on causative bacteria, rifampicin resistance, treatment, and outcome were obtained. Kaplan-Meier survival analysis and Cox regression modelling estimated the infection-free cumulative survival and adjusted hazard ratios (HRs) for the risk of treatment failure.

RESULTS

Rifampicin-resistant causative bacteria were identified in 40 cases (17%). The proportion of rifampicin-resistant agents decreased from 24% in 2010-2015 to 12% in 2016-2020. The 2-year infection-free survival rates were 78.6% (95% CI, 66.4-93.1%) for the rifampicin-resistant group and 90.0% (95% CI, 85.8-94.4%) for the rifampicin-sensitive group. Patients with PJI caused by rifampicin-resistant bacteria had an increased risk of treatment failure (adjusted HR, 4.2; 95% CI, 1.7-10.3).

CONCLUSIONS

The incidence of PJI caused by rifampicin-resistant bacteria did not increase over the past 20 years. The risk of treatment failure in PJI caused by rifampicin-resistant bacteria is more than four times that caused by rifampicin-sensitive bacteria, highlighting the importance of limiting the development of rifampicin resistance.

Increased mortality after total hip prosthetic joint infection is mainly caused by the comorbidities rather than the infection itself

BACKGROUND AND PURPOSE

Periprosthetic joint infection (PJI) is a feared complication of arthroplasty surgery. There is controversy as to whether PJI also correlates with increased mortality. Our aim was to investigate in a nationwide cohort if PJI is an independent risk factor for dying.

PATIENTS AND METHODS

We performed a retrospective cohort study based on data from the Swedish Hip Arthroplasty Register (SHAR). All patients with a revision THA performed between 1998 and 2017 were included. The outcome is mortality; exposure is PJI according to SHAR. The control group was study participants who underwent aseptic revision. Confounders were age, sex, diagnosis, and comorbidity according to the Elixhauser index. The outcome was analyzed with a Cox proportional hazards model.

RESULTS

4,943 PJI revisions and 12,529 non-infected revisions were included in the analysis. The median follow-up time was 4.1 years. In the PJI group, 1,972 patients died and in the control group, 4,512. The incidence rate ratio was 1.19 (95% confidence interval [CI] 1.13-1.25), the crude hazard ratio (HR) 1.19 (CI 1.13-1.25), and the adjusted HR 1.05 (CI 0.99-1.12) for the exposed versus the unexposed group. The strongest confounder was comorbidity.

CONCLUSION

The increased mortality risk after revision due to PJI is mainly caused by the comorbidity of the patient, rather than by the infection itself.