Operating room ventilation and the risk of revision due to infection after total hip arthroplasty: assessment of validated data in the Norwegian Arthroplasty Register.

BACKGROUND: The air in the operating room is considered a risk factor for surgical site infection (SSI) due to airborne bacteria shed from the surgical staff or from patients themselves. AIM: To assess the influence of validated operating room (OR) ventilation data on the risk of revision surgery due to deep infection after primary total hip arthroplasty (THA) reported to the Norwegian Arthroplasty Register (NAR). METHODS: Forty orthopaedic units reporting THAs to the NAR during the period 2005-2015 were included. The true type of OR ventilation in all hospitals at the time of primary THA was confirmed in a previous study. Unidirectional airflow (UDF) systems were subdivided into: small, low-volume, unidirectional vertical flow (lvUDVF) systems; large, high-volume, unidirectional vertical flow (hvUDVF) systems; and unidirectional horizontal flow (UDHF) systems. These three ventilation groups were compared with conventional, turbulent, mixing ventilation (CV). The association between the end-point, time to revision due to infection, and OR ventilation was estimated by calculating relative risks (RRs) in a multivariate Cox regression model, with adjustments for several patient- and surgery-related covariates. FINDINGS: A total of 51,292 primary THAs were eligible for assessment. Of these, 575 had been revised due to infection. A similar risk of revision due to infection after THA performed was found in ORs with lvUDVF and UDHF compared to CV. THAs performed in ORs with hvUDVF had lower risk of revision due to infection compared to CV (RR = 0.8; 95% CI: 0.6-0.9; P = 0.01). CONCLUSION: THAs performed in ORs with hvUDVF systems had lower risk of revision due to infection compared to THAs performed in ORs with CV systems. The perception that all UDF systems are similar and possibly harmful seems erroneous.

The Norwegian Arthroplasty Register: 11 years and 73,000 arthroplasties.

In 1985, the Norwegian Orthopaedic Association decided to establish a national hip register, and the Norwegian Arthroplasty Register was started in 1987. In January 1994, it was extended to include all artificial joints. The main purpose of the register is to detect inferior results of implants as early as possible. All hospitals participate, and the orthopedic surgeons are supposed to report all primary operations and all revisions. Using the patient's unique national social security number, the revision can be linked to the primary operation, and survival analyses of the implants are done. In general, the survival analyses are performed with the Kaplan-Meier method or using Cox multiple regression analysis with adjustment for possible confounding factors such as age, gender, and diagnosis. Survival probabilities can be calculated for each of the prosthetic components. The end-point in the analyses is revision surgery, and we can assess the rate of revision due to specific causes like aseptic loosening, infection, or dislocation. Not only survival, but also pain, function, and satisfaction have been registered for subgroups of patients. We receive reports about more than 95% of the prosthesis operations. The register has detected inferior implants 3 years after their introduction, and several uncemented prostheses were abandoned during the early 1990s due to our documentation of poor performance. Further, our results also contributed to withdrawal of the Boneloc cement. The register has published papers on economy, prophylactic use of antibiotics, patients' satisfaction and function, mortality, and results for different hospital categories. In the analyses presented here, we have compared the results of primary cemented and uncemented hip prostheses in patients less than 60 years of age, with 0-11 years' follow-up. The uncemented circumferentially porous- or hydroxyapatite (HA)-coated femoral stems had better survival rates than the cemented ones. In young patients, we found that cemented cups had better survival than uncemented porous-coated cups, mainly because of higher rates of revision from wear and osteolysis among the latter. The uncemented HA-coated cups with more than 6 years of follow-up had an increased revision rate, compared to cemented cups due to aseptic loosening as well as wear and osteolysis. We now present new findings about the six commonest cemented acetabular and femoral components. Generally, the results were good, with a prosthesis survival of 95% or better at 10 years, and the differences among the prosthesis brands were small. Since the practice of using undocumented implants has not changed, the register will continue to survey these implants. We plan to assess the mid- and long-term results of implants that have so far had good short-term results.

[The hip registry. Good economy for society]. / Hofteregisteret. God samfunnsøkonomi.

As many as 33,656 total hip arthroplasties (THA) have been recorded in the Norwegian Arthtroplasty Register from the start in September 1987 until January 1994. The annual costs for the about 5,500 THA performed in Norway (4.2 million inhabitants) are 72 million USD. We have documented before that some types of uncemented prostheses (Ti-Fit/ Bio-Fit (cup/stem) and Coxa/Femora) and types of cements (low-viscosity and Boneloc) show higher revision rates than others do. In this paper the costs of these "inferior" implants are estimated. The "inferior" implants were compared with a reference-THA (the Charnley prosthesis with antibiotic-containing high viscosity cement and with systemic antibiotic-prophylaxis (n = 4,970)). In addition, based on data in the literature, comparisons have been made for two earlier commonly used prostheses in Norway: The Christiansen prosthesis (n = 6,500) and the Wagner double-cup prosthesis (n = 2,200). For the period 1987-93, the annual over-all extra cost of using other implants than the reference-THA was 1.71 mill. USD for the first 3-5 years postoperatively. For the Christiansen and the Wagner prostheses the annual extra costs were estimated to 2.65 and 2.38 mill. USD respectively. By documenting poor results early the Register helps to stop the use of the inferior prostheses and cements, and thus reduce both the number of revisions, and, most important, the suffering of the patients.

The economic impact of failures in total hip replacement surgery: 28,997 cases from the Norwegian Arthroplasty Register, 1987-1993.

The Norwegian Arthroplasty Register was established in 1987. Until January 1994, approximately 200 different implant combinations had been used in total hip replacements (THR) in Norway. About 5,500 THR were performed each year in this period with a total cost of 70 million USD per year. We analyzed the economic consequences related to the use of some inferior primary hip arthroplasties in this period. As the reference arthroplasty, we chose the most commonly used prosthesis in Norway, i.e., the Charnley prosthesis fixed with high viscosity cement containing antibiotic and with systemic antibiotic prophylaxis (n 4,970). We compared this reference group to all other primary THR registered in the same time period (n 24,027), and to the following sub-groups of primary THR: 1) uncemented Ti-Fit/ Bio-Fit (acetabulum/femur) combination (n 173), 2) uncemented Coxa/Femora combination (n 153), 3) THR with low-viscosity cement (n 1,807) and 4) THR with Boneloc cement (n 1,250). We estimated the number of additional revisions compared to the reference arthroplasty after a follow-up of 3-5 years in the different groups, with adjustment for age, sex and diagnosis. The direct extra revision costs were calculated. Compared to the reference arthroplasty, the group of all other primary THR gave an extra revision cost estimated at about 1.7 million USD per year. About 1,000 uncemented Bio-Fit femoral prostheses have been applied in Norway, including those implanted before the registration started (1985-1987). The extra revision costs the first postoperative years for these 1,000 prostheses amount to about 0.7 million USD per year. Corresponding figures in the Coxa/ Femora group were 0.08 million USD, in the group with low-viscosity cement, 0.3 million USD and in the Boneloc group, 0.4 million USD per year.

Ultrasound and congenital dislocation of the hip. The importance of dynamic assessment.

One-hundred newborn children at high risk of hip instability were prospectively assessed clinically and by ultrasound. The decision to treat was based only on the clinical examination. At the age of three months all the children were evaluated clinically and with an anteroposterior radiograph of the pelvis. None of the standard ultrasound measurements of acetabular depth and femoral head cover correlated with the outcome at three months. Dynamic assessment of stability was the only ultrasound technique that had a significant relation with outcome.