The effect of the type of cement on early revision of Charnley total hip prostheses. A review of eight thousand five hundred and seventy-nine primary arthroplasties from the Norwegian Arthroplasty Register

Do voids in a femoral cement mantle affect the outcome?

A total of 156 ceramic versus ultra-high-molecular-weight polyethylene hip prostheses were followed for a minimum of 10 years to compare the outcome of the femoral component in 2 groups: those with and those without radiologically detectable voids in the cement mantle. No significant difference was observed. In this series, voids with a 5-mm diameter had no effect on loosening of the femoral component over a 10-year period.

Lessons from Europe on quality improvement: report on the Velen Castle WHO meeting

BACKGROUND

In conjunction with the German Ministry of Health, the European Regional Office of the World Health Organization (WHO/EURO) held a workshop, "Experiences with Quality Management in an International Context," at Velen Castle, Velen (Nordrhein-Westfalen), Germany, January 15-17, 1998. The approximately 50 participants were selected in part on the basis of recommendations of their respective countries' health ministries.

IMPLEMENTATION AND EVALUATION OF QUALITY MANAGEMENT

Possible ways to introduce quality management ranged from introduction of specific process control projects to total quality management (TQM) and reengineering.

STRATEGIES FOR IMPLEMENTING QUALITY MANAGEMENT

Working group sessions identified specific strategies for high-level managers, health care providers, and various kinds of consumers to facilitate quality management. For example, managers need to transmit a vision, create a quality management infrastructure, develop reporting structures, establish a system of incentives, and manage the hospital according to the principles of continuous improvement.

QUALITY MANAGEMENT MODELS AND TOOLS

Hospitals and other health care providers in Sweden are testing various methods and systems to assess and improve their organizations' ability to meet patients' demands. Benchmarking is being used as a tool for quality management of diabetes care (DiabCare-France). The benchmarking data are processed centrally and made available to the health care providers in a user-friendly format for application to their own quality improvement processes. Clinical databases-registries containing process and outcome data for a well-defined patient population-can be used for quality and technology assessment, to answer questions of treatment effectiveness, and as an information tool.

PRINCIPLES AND STRATEGIES FOR QUALITY MANAGEMENT AND DEVELOPMENT

Successful implementation of quality improvement benefits from local, professional, and national policies and objectives. A balance of incentives can reward efficiency or specific activities. Laws, rules, and regulations can be useful, especially if used sparingly. More education is needed at all levels of the health care system about how to understand and use information and information systems. Research is needed on what processes result in favorable outcomes. Despite optimism about the cost-saving potential of quality improvement efforts, many interventions are likely to be cost-effective without actually saving costs. Public release of performance data requires careful consideration, with participation of the professions.

The effect of hospital-type and operating volume on the survival of hip replacements. A review of 39,505 primary total hip replacements reported to the Norwegian Arthroplasty Register, 1988-1996

We investigated associations between the survival of total hip replacements (THRs), type of hospital and annual number of THRs per hospital. The study was based on 39,505 primary THRs reported to the Norwegian Arthroplasty Register from 45 local (n 20,756), 15 central (n 12,455) and 10 university hospitals (n 6,294) during 1988-1996. The annual number of THRs was highest at central and university hospitals, both of which are training hospitals. University hospitals were further characterized by the lowest mean annual number of THRs performed per surgeon. For cemented THRs, with adjustment for gender, age, diagnosis, surgical procedure, and annual hospital volume, the revision rates at central and university hospitals were 0.8 (95% confidence interval: 0.67-0.95) and 1.2 (CI: 1.02-1.47) times that of local hospitals, respectively. A high annual number of cemented THRs per hospital was not associated with lower revision rates. In uncemented THRs, survival results were similar in central and local hospitals, whereas the adjusted revision rate at university hospitals was 1.6 (CI: 1.13-2.19) times that of local hospitals. The adjusted 6.5 year revision probability was 12% in hospitals performing < or = 10 uncemented THRs per year (n 606), 8% in hospitals performing from 18-28 operations (n 1,378) and 5% in hospitals performing > 84 operations (n 526).

Inferior performance of Boneloc bone cement in total knee arthroplasty: a prospective randomized study comparing Boneloc with Palacos using radiostereometry (RSA) in 19 patients

We compared Boneloc bone cement with conventional cement (Palacos) in fixating the tibial component during 2-5 years in 19 patients with gonarthrosis undergoing total knee arthroplasty in a prospective randomized study. Boneloc displayed significantly larger migration, subsidence and lift-off than Palacos. The difference was identifiable already within 3 months postoperatively, but became significant at 12 months. In the Boneloc group, all components showed subsidence of the posterior part and lift-off of the anterior part of the tibial component, whereas in the Palacos group, the locations of subsidence and lift-off were evenly distributed about the edge of the implant. At 5 years, both Boneloc knees so far investigated were clinical failures with high migration rates. We conclude that, even in total knee arthroplasty, there is a substantial risk that Boneloc leads to inferior clinical results, but later than in hip replacements.

Exeter and charnley arthroplasties with Boneloc or high viscosity cement. Comparison of 1,127 arthroplasties followed for 5 years in the Norwegian Arthroplasty Register

During the years 1991-1994, the Norwegian Arthroplasty Register recorded 1,324 primary hip arthroplasties implanted with the Boneloc cement. We have compared the survival until revision due to aseptic loosening for charnley (n 955) and Exeter (n 172) prostheses. The Boneloc cemented hips were also compared with high viscosity cemented hips implanted during the same period. In the Boneloc cemented group, the estimated probability of survival at 4.5 years of a Charnley femoral component was 74% and for an Exeter femoral component 97% (p < 0.0001). Using a Cox regression model with adjustment for age, gender, type of cement, systemic antibiotic and stratified for diagnosis, an 8 times higher risk of revision was found in Boneloc cemented Charnley femoral components than in Exeter femoral components (p < 0.0001). For the acetabular components, the difference between the Charnley and Exeter components with Boneloc cement was not statistically significant. In both the Charnley and the Exeter prostheses, the high viscosity cemented components had significantly better survival than the Boneloc cemented components. The Cox regression model showed that a Boneloc cemented Charnley femoral component had a 14 times higher risk of revision than a high viscosity cemented component (p < 0.0001), and for Exeter femoral components a 7 times higher revision risk was found in the Boneloc cemented components (p = 0.003). Our results confirm the previously reported inferior results of Charnley prostheses implanted with Boneloc cement and inferior results of Boneloc cemented Exeter prostheses as well, but less pronounced than for Charnley prostheses.

Patient-related risk factors for early revision of total hip replacements. A population register-based case-control study of 674 revised hips

In this population register-based, matched case-control study, we assessed patient-related factors and early risk of revision after total hip replacement (THR). Information was obtained via a mall survey among patients reported to the Norwegian Arthroplasty Register during the period 1987-1993. The study included 674 revised hips, as cases, and 1,343 hips with a primary operation only, as controls. Completed questionnaires were received from 81% of the 2,017 individual cases and controls. We identified a set of patient-related factors associated with poor THR prognosis. Increasing weight was a risk factor among male patients older than 67 years who were more than 1.77 m tall (p = 0.01). Smoking had no overall effect, but former heavy smokers had an increased risk of 2.8 compared to never-smokers. Alcohol intake was associated with an increased risk of dislocation. Revision due to infection was commoner among patients taking anti-diabetic drugs (OR = 14) than among patients taking no medication. An increased overall revision risk was found among patients using systemic steroids (OR = 2.8) or local pulmonary steroids (OR = 6.0). The risk also increased in male patients performing regular exercise before the primary operation (OR = 2.6), and in female patients of working-age doing heavy work (OR = 1.9).

Image processing for femoral endosteal anatomy detection: description and testing of a computed tomography based program

A computed tomography (CT)-based image processing computer program was developed for three-dimensional (3D) femoral endosteal cavity shape modelling. For the examinations 50 cadaver femora were used. In the CT imaging 30 axial slices were taken above and below the lesser trochanter area from each femur. Different image analysis methods were used for femoral cavity detection depending on the structure of the processed slice. In the femoral shaft area simple thresholding methods succeeded, but in the problem areas of the metaphyseal femur edge, detection operators and local thresholding were required. In contour tracking several criteria were used to check the validity of the border pixels. The results were saved as four output data files: (i) a file for the longest anteroposterior (ap), mediolateral (ml) and oblique diameters computed by a Euclidian method, (ii) and (iii) files for 2D and 3D data respectively, and (iv) a file for centre points of each slice. Finally, testing of the results and dimensions obtained from the image analysis were carried out manually by sawing the femora into 10 stipulated horizontal slices. The ap and ml dimensions were measured with a caliper ruler. The CT-based image processing yielded a peak distribution of dimensions with a negative difference to those obtained in manual measurements. The mean difference between the image processing and the manual measurements was 1.1 mm (+/-0.7 mm, +/-1 SD). The difference was highest in the proximal slices of the femora of group I (with lowest cortical thickness), i.e. 1.3 mm (+/-0.8 mm) and lowest in the distal slices of the femora from group III (with highest cortical thickness), i.e. 0.9 mm (+/-0.6 mm). The results are acceptable for further use of the program to study endosteal anatomy for individual femoral component selection and designing basis.

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.

The Harris-Galante cementless femoral component: poor results in 57 hips followed for 3 years

Between 1986 and 1991, 68 Harris-Galante femoral prostheses were implanted in 63 patients. 53 patients (57 hips) attended for follow-up after a mean of 3.4 (2-6) years. The average Harris Hip Score (HHS) was 39 preoperatively and 81 postoperatively. Only 34 hips were excellent (27) or good (7). Mid-thigh pain occurred in 30 cases. 10 femoral components were radiographically loose because of osteolysis. Although 7 cups seemed to be radiographically loose, they probably played only a minor role in the poor overall early clinical results.

Early revision among 12,179 hip prostheses. A comparison of 10 different brands reported to the Norwegian Arthroplasty Register, 1987-1993

On the basis of data from the Norwegian Arthroplasty Register during the period 1987-1993, we have compared times to revision for 10 different cemented total hip prostheses. A total of 11,169 patients, with 12,179 primary total hip replacements (THRs), performed with high viscosity cement for primary arthrosis and followed for a maximum of 6.4 years, were included in this study. The Kaplan-Meier estimate of the overall percentage revised after 5 years was 2.5 (95% Confidence Interval: 2.1-3.0). For the Charnley prosthesis (n 6,694), 2.9% were revised after 5 years (95% CI: 2.3-3.4). Using Cox regression to adjust for gender, age, type of cement and use of systemic antibiotic prophylaxis, the Charnley prosthesis was compared with the 9 other brands. The revision rate for the Spectron/ITH combination (Spectron acetabulum, ITH femur) (n 1,034) was only 0.35 (p 0.04) times that of the Charnley prostheses. The Elite/Charnley combination (Elite acetabulum, Charnley femur) (n 507) and the Müller Type prosthesis (n 116) showed poorer results with failure rates 2.3 (p 0.01) and 2.7 times (p 0.04) that of Charnley, respectively. Although the overall results for cemented THRs in general were good, clinically important differences in revision rates were demonstrated among the cemented prosthesis brands. Our findings underline the need for careful evaluation of different total hip replacements.