Birgitte Espehaug

Antibiotic prophylaxis in total hip arthroplasty: effects of antibiotic prophylaxis systemically and in bone cement on the revision rate of 22,170 primary hip replacements followed 0-14 years in the Norwegian Arthroplasty Register.

We studied the effects of antibiotic prophylaxis, systemically and in bone cement, on the revision rate of cemented total hip arthroplasties (THAs) in data from the Norwegian Arthroplasty Register during the period 1987-2001. To have comparable groups, only THAs performed because of primary osteoarthritis, using cemented implants with documented good results, and high-viscosity cement were included. If systemic antibiotic prophylaxis had been given, only operations with cephalosporin or penicillin were selected. Cox-estimated survival relative revision risks (RR) are presented with adjustment for differences among groups in gender, age, cement brand, type of systemic antibiotic prophylaxis, type of prosthesis, type of operating room, and duration of the operation. Of 22,170 THAs studied, 696 THAs (3.1%) were revised, 440 (2.0%) for aseptic loosening and 102 (0.5%) for deep infection. We found the lowest risk of revision when the antibiotic prophylaxis was given both systemically and in the cement (15,676 THAs). Compared to this combined regime, patients who received antibiotic prophylaxis only systemically (5,960 THAs) had a 1.4 times higher revision rate with all reasons for revision as endpoint (p= 0.001), 1.3 times higher with aseptic loosening (p= 0.02) and 1.8 times higher with infection as the endpoint (p= 0.01). With the combined antibiotic regime, the results were better if antibiotics were given 4 times on the day of surgery (2,194 THAs), as compared to once (1,424 THAs) (p<0.001), twice (2,680 THAs) (p<0.001), or 3 times (5,522 THAs) (p= 0.02). Those who received systemic prophylaxis a single day 1, 2 or 3 times, as compared to 4 times, had a revision rate 1.8-3.5 times higher with all reasons for revision as endpoint, 1.5-3.1 times higher with aseptic loosening, and 2.7-6.8 times higher with infection. When we compared systemic prophylaxis 4 times in 1 day, no further improvement resulted in those given systemic prophylaxis for 2 days (1,928 THAs) or 3 days (717 THAs). In a subset of data including only the Charnley prosthesis, we obtained similar results. This observational study shows that the best results were recorded when antibiotic prophylaxis was given both systemically and in the bone cement, and if the systemic antibiotic was given 4 times on the day of surgery.

Antibiotic prophylaxis in total hip arthroplasty

We have assessed the effect of different regimes of antibiotic prophylaxis on the survival of total hip implants, comparing antibiotics administered both systemically and in the bone cement, systemically only, in the bone cement only and with no antibiotics given. We studied 10 905 primary cemented total hip replacements, performed for osteoarthritis of the hip and reported to the Norwegian arthroplasty register between 1987 and 1995. Cox-estimated failure-rate ratios (FRR) are presented with adjustment for gender, age, the brand of cement, the prosthesis, the type of operating theatre and the operating time. For revisions performed for infection (39 operations), the lowest rate of revision was found among patients receiving antibiotic-containing cement plus systemic antibiotics (n = 5804). The revision rate for the 4586 patients receiving systemic antibiotics only was 4.3 times greater (95% CI 1.7 to 11.0, p = 0.001); in 239 with antibiotics in the bone cement only it was 6.3 times greater (CI 1.6 to 25.0, p = 0.003); and in the 276 who did not receive antibiotics it was by 11.5 times greater (CI 2.1 to 63.0, p = 0.002). Adjustment for the total amount of systemic antibiotic administered did not change the results. We also observed an increased revision rate for aseptic loosening (109 operations) comparing the systemic-only (FRR = 1.8, CI 1.1 to 2.9, p = 0.01) and the cement-only regimes (FRR = 2.6, CI 1.2 to 5.9, p = 0.02) with the combined dosage. Our findings show that systemic antibiotics combined with antibiotic-containing bone cement led to fewer revisions than the other methods.

Early failures among 7,174 primary total knee replacements: A follow-up study from the Norwegian Arthroplasty Register 1994-2000

We studied primary total knee replacements (TKRs), reported to the Norwegian Arthroplasty Register, operated on between 1994 and 2000. A Cox multiple regression model was used to evaluate differences in survival among the prosthesis brands, their types of fixation, and whether or not the patella was resurfaced. In Norway in 1999, the incidence of knee prosthesis operations was 35 per 100,000 inhabitants. Cement was used as fixation in 87% of the knees, 10% were hybrid and 2% uncemented implants. Bicompartmental (not resurfaced patella) prostheses were used in 65% of the knees. With all revisions as endpoint, no statistically significant differences in the 5-year survival were found among the cemented tricompartmental prostheses brands: AGC 97% (n 279), Duracon 99% (n 101), Genesis I 95% (n 654), Kinemax 98% (n 213) and Tricon 96% (n 454). The bicompartmental LCS prostheses had a 5-year survival of 97% (n 476). The type of meniscal bearing in LCS knees had no effect on survival. Survival with revision for all causes as endpoint showed no differences among types of fixation, or bi- or tricompartmental prostheses. Pain alone was the commonest reason for revision of cemented bicompartmental prostheses. The risk of revision because of pain was 5.7 times higher (p < 0.001) in cemented bicompartmental prostheses than cemented tricompartmental ones, but the revisions mainly involved insertion of a patellar component. In tricompartmental prostheses the risk of revision because of infection was 2.5 times higher than in bicompartmental ones (p = 0.03). Young age (< 60) and the sequelae after a fracture increased the risk of revision. The 5-year survival of the 6 most used cemented tricompartmental knee prostheses brands varied between 95% and 99%, but the differences were not statistically significant. There were more revisions because of pain in bicompartmental than in tricompartmental knees. In tricompartmental knees, however, there were more revisions because of an infection. The relatively few patients with uncemented and hybrid implants showed no improvements in results compared to cemented knee prostheses.

Registration completeness in the Norwegian Arthroplasty Register

Introduction A high degree of registration completeness is necessary in order to obtain unbiased and accurate register-based study results. We investigated the completeness of registration in the national Norwegian Arthroplasty Register (NAR). Material and methods Registration completeness for the years 1999–2002 was calculated as a percentage, with the number of joint replacements reported to the NAR as numerator and those reported to the Norwegian Patient Register (NPR) as denominator. While the NAR received information directly from the orthopedic surgeons on a voluntary basis, the NPR, which is mandatory, received information from the electronic administrative patient records of the hospitals. Results Registration completeness in the NAR was 97% (97% for primary operations; 101% for revisions). Completeness was 98% (97%; 106%) for hip replacements, and for knee replacements it was 99% (99%; 97%). Hip and knee replacements represented 95% of all operations. However, completeness was poorer for less common joint replacements and poorest for ankle implants (82%; 40%) and wrist implants (52%; 14%). In the NAR, completeness of registration of revisions involving only removal of one or more prosthetic parts was lower than for exchange revisions for all types of joint replacement. For hip implants, 76% of the removal revisions (80% of Girdlestone procedures) were reported, and for knee implants the figure was 62%. According to NPR statistics, removal procedures accounted for 9% of all revisions of hip and knee replacements. Interpretation In the NAR, registration completeness of hip and knee replacements was high both for primary operations and exchange revisions. For some of the less common joint replacements, completeness was low and may—if not improved—compromise prosthesis survival studies. The lower registration completeness of removal revisions also needs to be improved. ▪

Failure Mechanisms After Unicompartmental and Tricompartmental Primary Knee Replacement with Cement

BACKGROUND Concern exists regarding the durability of unicompartmental knee replacements. The purpose of the present study was to compare the early failure rates and failure mechanisms of primary cemented unicompartmental knee replacements with those of primary cemented tricompartmental total knee replacements. METHODS The rates of failure of primary cemented unicompartmental knee replacements (n = 2288) and tricompartmental total knee replacements (n = 3032) as reported to the Norwegian Arthroplasty Register from January 1994 through December 2004 were compared with use of Kaplan-Meier estimated survival rates and Cox multiple regression. RESULTS The ten-year survival probability was 80.1% (95% confidence interval, 76.0% to 84.2%) for unicompartmental knee replacements, compared with 92.0% (95% confidence interval, 90.4 to 93.6%) for total knee replacements, with a relative risk of revision of 2.0 (95% confidence interval, 1.6 to 2.5) (p < 0.001). This increased risk of revision following unicompartmental knee replacement was seen in all age-categories. Unicompartmental knee replacement was associated with an increased risk of revision due to pain (relative risk, 11.3 [95% confidence interval, 4.8 to 26.8]; p < 0.001), aseptic loosening of the tibial component (relative risk, 1.9 [95% confidence interval, 1.2 to 3.0]; p = 0.01) and of the femoral component (relative risk, 4.8 [95% confidence interval, 2.3 to 10.3]; p < 0.001), and periprosthetic fracture (relative risk, 3.2 [95% confidence interval, 1.2 to 8.9]; p = 0.02) as compared with total knee replacement. Unicompartmental knee replacement was associated with a lower risk of infection compared with total knee replacement (relative risk, 0.28 [95% confidence interval, 0.10 to 0.74]; p = 0.01). CONCLUSIONS The survival of cemented unicompartmental knee replacements is inferior to that of cemented tricompartmental total knee replacements in all age-categories.

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.

We studied the survival of 8579 Charnley prostheses, in 7922 patients, according to the different types of cement that had been used. All of the patients had had a primary total hip replacement for primary coxarthrosis. The mean duration of follow-up was 3.2 years (range, zero to 6.4 years). The data were collected from the national Norwegian Arthroplasty Register. The duration of survival was defined as the time to revision due to aseptic loosening. The Kaplan-Meier estimate of survival at 5.5 years for the 1226 femoral components that had been implanted with low-viscosity cement was 94.1 per cent (95 per cent confidence interval, 92.1 to 96.2 per cent), compared with 98.1 per cent (95 per cent confidence interval, 97.5 to 98.6 per cent) for the 6589 components that had been implanted with high-viscosity cement (p < 0.0001). The remaining 764 femoral components had been implanted with Boneloc cement, which was classified as neither high nor low-viscosity, and these components were considered as a separate group in the analyses. The Boneloc cement had been used for only three years, and the two-year survival rate of these prostheses was 95.5 per cent (p < 0.0001). The cement contained an antibiotic in 2801 (42 per cent of the hips in which the femoral component had been implanted with high-viscosity cement, compared with only thirty (2 per cent) of those in which it had been implanted with low-viscosity cement.(ABSTRACT TRUNCATED AT 250 WORDS)

Femoral head size is a risk factor for total hip luxation A study of 42,987 primary hip arthroplasties from the Norwegian Arthroplasty Register

On the basis of the Norwegian Arthroplasty Register, which has recorded nearly all primary hip prostheses and revisions in Norway since 1987, we studied risk factors for prosthesis luxation leading to revision. 7 prosthesis brand combinations used in 42,987 primary operations were included from 1987-2000. We found that femoral head size was an important risk factor; 28 mm heads led to revision more often than 32 mm ones (failure rate ratio (FRR) 4.0, 95% confidence interval (CI) 2.2-7.3). Charnley (22 mm head) performed equally well or better than the 28 mm heads. The Exeter stem and cup is the type of prosthesis on the Norwegian market with more than two femoral head sizes (26, 28, 30, 32 mm) and 26 mm heads led to revision due to luxation significantly more often than 30 mm heads (FRR 4.1, 95%CI 2.2-8.1). Old age, preoperative diagnosis, and choice of prosthesis brand combination were also important factors affecting the revision rate due to luxation. A posterior approach increased the risk of revision more than a lateral one (FRR 1.9, 95%CI 1.4-2.5). Gender, trochanteric osteotomy and duration of the operation did not affect the results.

Risk of revision for infection in primary total hip and knee arthroplasty in patients with rheumatoid arthritis compared with osteoarthritis: A prospective, population-based study on 108,786 hip and knee joint arthroplasties from the Norwegian Arthroplasty Register

To compare differences in the risk of revision for infection and changes in risk over time and in time from primary surgery to revision for infection after total hip replacement (THR) and total knee replacement (TKR) in rheumatoid arthritis (RA) and osteoarthritis (OA) patients.

Increasing risk of revision due to deep infection after hip arthroplasty.

Background and purpose Over the decades, improvements in surgery and perioperative routines have reduced the incidence of deep infections after total hip arthroplasty (THA). There is, however, some evidence to suggest that the incidence of infection is increasing again. We assessed the risk of revision due to deep infection for primary THAs reported to the Norwegian Arthroplasty Register (NAR) over the period 1987–2007. Method We included all primary cemented and uncemented THAs reported to the NAR from September 15, 1987 to January 1, 2008 and performed adjusted Cox regression analyses with the first revision due to deep infection as endpoint. Changes in revision rate as a function of the year of operation were investigated. Results Of the 97,344 primary THAs that met the inclusion criteria, 614 THAs had been revised due to deep infection (5-year survival 99.46%). Risk of revision due to deep infection increased throughout the period studied. Compared to the THAs implanted in 1987–1992, the risk of revision due to infection was 1.3 times higher (95%CI: 1.0–1.7) for those implanted in 1993–1997, 1.5 times (95% CI: 1.2–2.0) for those implanted in 1998–2002, and 3.0 times (95% CI: 2.2–4.0) for those implanted in 2003–2007. The most pronounced increase in risk of being revised due to deep infection was for the subgroup of uncemented THAs from 2003–2007, which had an increase of 5 times (95% CI: 2.6–11) compared to uncemented THAs from 1987–1992. Interpretation The incidence of deep infection after THA increased during the period 1987–2007. Concomitant changes in confounding factors, however, complicate the interpretation of the results.

Early failures among 14,009 cemented and 1,326 uncemented prostheses for primary coxarthrosis. The Norwegian Arthroplasty Register, 1987-1992.

In the Norwegian Arthroplasty Register, 15,335 primary total hip replacements (THR) in patients with primary arthrosis were followed for 0-5.4 years. The Kaplan-Meier estimate of cumulative failure (revision) after 4.5 years was 2.7 percent for cemented THR, compared to 6.5 percent for uncemented. In patients under 65 years the cumulative revisions for cemented and uncemented THR were 3.3 and 7.9 percent. For the acetabular components, the cumulative failures were 0.6 percent for cemented and 1.7 percent for uncemented, and for femoral components 1.7 and 3.9 percent after 4.5 years. Adjusting for age and sex using a Cox regression model, 2 times higher rates of failure were found comparing uncemented to cemented THR. The results for uncemented prostheses were more unfavorable in young patients. In men and women under 60, the revision rates were increased 6 and 3 times, respectively, for patients with uncemented THR compared to those with cemented THR. Restriction of the end-point to revision for aseptic loosening gave results similar to the over-all results. No difference between cemented and uncemented THR was seen for revisions due to infection, whereas the most unfavorable results for uncemented THR were seen when revisions due to causes other than infection and aseptic loosening were considered.