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.

Hip disease and the prognosis of total hip replacements. A review of 53,698 primary total hip replacements reported to the Norwegian Arthroplasty Register 1987-99

We studied the rates of revision for 53,698 primary total hip replacements (THRs) in nine different groups of disease. Factors which have previously been shown to be associated with increased risk of revision, such as male gender, young age, or certain types of uncemented prosthesis, showed important differences between the diagnostic groups. Without adjustment for these factors we observed an increased risk of revision in patients with paediatric hip diseases and in a small heterogeneous 'other' group, compared with patients with primary osteoarthritis. Most differences were reduced or disappeared when an adjustment for the prognostic factors was made. After adjustment, an increased relative risk (RR) of revision compared with primary osteoarthritis was seen in hips with complications after fracture of the femoral neck (RR = 1.3, p = 0.0005), in hips with congenital dislocation (RR = 1.3, p = 0.03), and in the heterogenous 'other' group. The analyses were also undertaken in a more homogenous subgroup of 16,217 patients which had a Charnley prosthesis implanted with high-viscosity cement. The only difference in this group was an increased risk for revision in patients who had undergone THR for complications after fracture of the femoral neck (RR = 1.5, p = 0.0005). THR for diagnoses seen mainly among young patients had a good prognosis, but they had more often received inferior uncemented implants. If a cemented Charnley prosthesis is used, the type of disease leading to THR seems in most cases to have only a minor influence on the survival of the prosthesis.

Antibiotic prophylaxis in total hip arthroplasty. Review of 10,905 primary cemented total hip replacements reported to the Norwegian arthroplasty register, 1987 to 1995

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.

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)

Hip disease and the prognosis of total hip replacements

We studied the rates of revision for 53 698 primary total hip replacements (THRs) in nine different groups of disease. Factors which have previously been shown to be associated with increased risk of revision, such as male gender, young age, or certain types of uncemented prosthesis, showed important differences between the diagnostic groups. Without adjustment for these factors we observed an increased risk of revision in patients with paediatric hip diseases and in a small heterogeneous ‘other’ group, compared with patients with primary osteoarthritis. Most differences were reduced or disappeared when an adjustment for the prognostic factors was made. After adjustment, an increased relative risk (RR) of revision compared with primary osteoarthritis was seen in hips with complications after fracture of the femoral neck (RR = 1.3, p = 0.0005), in hips with congenital dislocation (RR = 1.3, p = 0.03), and in the heterogenous ‘other’ group. The analyses were also undertaken in a more homogenous subgroup of 16 217 patients which had a Charnley prosthesis implanted with high-viscosity cement. The only difference in this group was an increased risk for revision in patients who had undergone THR for complications after fracture of the femoral neck (RR = 1.5, p = 0.0005).

THR for diagnoses seen mainly among young patients had a good prognosis, but they had more often received inferior uncemented implants. If a cemented Charnley prosthesis is used, the type of disease leading to THR seems in most cases to have only a minor influence on the survival of the prosthesis.

Survival rates and causes of revision in cemented primary total knee replacement: a report from the Norwegian Arthroplasty Register 1994-2009

We evaluated the rates of survival and cause of revision of seven different brands of cemented primary total knee replacement (TKR) in the Norwegian Arthroplasty Register during the years 1994 to 2009. Revision for any cause, including resurfacing of the patella, was the primary endpoint. Specific causes of revision were secondary outcomes. Three posterior cruciate-retaining (PCR) fixed modular-bearing TKRs, two fixed non-modular bearing PCR TKRs and two mobile-bearing posterior cruciate-sacrificing TKRs were investigated in a total of 17 782 primary TKRs. The median follow-up for the implants ranged from 1.8 to 6.9 years. Kaplan-Meier 10-year survival ranged from 89.5% to 95.3%. Cox's relative risk (RR) was calculated relative to the fixed modular-bearing Profix knee (the most frequently used TKR in Norway), and ranged from 1.1 to 2.6. The risk of revision for aseptic tibial loosening was higher in the mobile-bearing LCS Classic (RR 6.8 (95% confidence interval (CI) 3.8 to 12.1)), the LCS Complete (RR 7.7 (95% CI 4.1 to 14.4)), the fixed modular-bearing Duracon (RR 4.5 (95% CI 1.8 to 11.1)) and the fixed non-modular bearing AGC Universal TKR (RR 2.5 (95% CI 1.3 to 5.1)), compared with the Profix. These implants (except AGC Universal) also had an increased risk of revision for femoral loosening (RR 2.3 (95% CI 1.1 to 4.8), RR 3.7 (95% CI 1.6 to 8.9), and RR 3.4 (95% CI 1.1 to 11.0), respectively). These results suggest that aseptic loosening is related to design in TKR.

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).

The type of cement and failure of total hip replacements

Using data from the Norwegian Arthroplasty egister, we have assessed the survival of 17 323 primary Charnley hip prostheses in patients with osteoarthritis based upon the type of cement used for the fixation of the implant. Overall, 9.2% had been revised after follow-up for ten years; 71% of the failures involved aseptic loosening of the femoral component. We observed significantly increased rates of failure for prostheses inserted with CMW1 and CMW3 cements. Using implants fixed with gentamicin-containing Palacos cement as the reference, the adjusted Cox regression failure rate ratios were 1.1 (95% CI 0.9 to 1.4) for implants cemented with plain Palacos, 1.1 (95% CI 0.7 to 1.6) for Simplex, 2.1 (95% 1.5 to 2.9) for gentamicin-containing CMW1, 2.0 (95% CI 1.6 to 2.4) for plain CMW1 and 3.0 (95% CI 2.3 to 3.9) for implants fixed with CMW3 cement. The adjusted failure rate at ten years varied from 5.9% for implants fixed with gentamicin-containing Palacos to 17% for those fixed with CMW3.

Early aseptic loosening of uncemented femoral components in primary total hip replacement. A review based on the Norwegian Arthroplasty Register

The Norwegian Arthroplasty Register recorded 24,408 primary total hip replacements from 1987 to 1993; 2907 of them (13%) were performed with uncemented femoral components. We have compared the results of eight different designs, each used in more than 100 patients. Survivorship of the components was estimated by the Kaplan-Meier method using revision for aseptic loosening of the femoral component as the end-point. At 4.5 years, the estimated probability of revision for aseptic loosening for all implants was 4.5%, for the Bio-Fit stem 18.6% (n = 210) and for the Femora stem 13.6% (n = 173). The PM-Prosthesis and the Harris/Galante stem prostheses needed revision in 5.6% and 3.6%, respectively. The clockwise threaded stem of the Femora implant needed revision in 20% of right hips, but in only 4% of left hips. The short-term results of the four best uncemented femoral components (Corail, LMT, Profile and Zweimuller) were similar to those for cemented stems, with revision for loosening in less than 1% at 4.5 years. The importance of the control of innovative designs and the registration of early results is discussed.

The Norwegian arthroplasty register. A survey of 17,444 hip replacements 1987-1990

In Norway a national register for total hip replacements was established in September 1987. Up till February 1991, 17,444 total hip replacements (THR) were reported, i.e., 140 THR/100,000 inhabitants/year. The median age of the patients was 70 years, and 69 percent were women. 87 percent were primary arthroplasties and 13 percent were revisions. Primary arthrosis was the diagnosis in 68 percent of the primary operations. The acetabular implants were uncemented in 17 percent and the femoral implants in 12 percent of primary operations. In revisions, the implants were uncemented in 21 and 17 percent, respectively. The reasons for revision were loosening of components in 87 percent and deep infection in 4 percent. The Charnley prosthesis dominated with 49 percent of all implants. A total of 422 different designs and sizes of acetabular implants, 398 femoral implants and 166 of caput designs and sizes were used. This large number of different types and designs seems unreasonable.

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.

Tamoxifen therapy in unresectable adenocarcinoma of the pancreas and the papilla of Vater

Between 1984 and 1987, 176 Norwegian patients with histologically verified unresectable pancreatic adenocarcinoma were randomized to double-blind treatment with oral tamoxifen (30 mg daily; 48 men and 44 women) or placebo (47 men and 37 women). Analysis of oestrogen receptor activity in the carcinomas was not performed. There were no statistically significant differences between the two groups according to age, Karnofsky performance index, tumour node metastasis (TNM) stage, operative treatment or other patient characteristics. The tamoxifen or placebo treatment continued to death or to 10 months after accrual into the trial was stopped. In the tamoxifen group, the mean and median survivals were 205 and 115 days, respectively. These values did not differ statistically from the 192 and 122 days, respectively, observed in the placebo group. Additional retrospective analyses of sex and stage revealed no beneficial effect of tamoxifen upon survival. For women in stage III (any T N1 M0), mean and median survivals were 255 and 191 days, respectively, compared with values of 84 and 45 days, respectively, in the placebo group (P = 0.011). After 2.5 years, three (7 per cent) women in the tamoxifen group were still alive compared with no survivors in the placebo group. No male patients survived beyond 2.5 years. This therapeutic result in a small subgroup of women is probably incidental and not an effect of tamoxifen.

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.

Functional outcome and alignment in computer-assisted and conventionally operated total knee replacements

We performed a randomised controlled trial comparing computer-assisted surgery (CAS) with conventional surgery (CONV) in total knee replacement (TKR). Between 2009 and 2011 a total of 192 patients with a mean age of 68 years (55 to 85) with osteoarthritis or arthritic disease of the knee were recruited from four Norwegian hospitals. At three months follow-up, functional results were marginally better for the CAS group. Mean differences (MD) in favour of CAS were found for the Knee Society function score (MD: 5.9, 95% confidence interval (CI) 0.3 to 11.4, p = 0.039), the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales for ‘pain’ (MD: 7.7, 95% CI 1.7 to 13.6, p = 0.012), ‘sports’ (MD: 13.5, 95% CI 5.6 to 21.4, p = 0.001) and ‘quality of life’ (MD: 7.2, 95% CI 0.1 to 14.3, p = 0.046). At one-year follow-up, differences favouring CAS were found for KOOS ‘sports’ (MD: 11.0, 95% CI 3.0 to 19.0, p = 0.007) and KOOS ‘symptoms’ (MD: 6.7, 95% CI 0.5 to 13.0, p = 0.035). The use of CAS resulted in fewer outliers in frontal alignment (> 3° malalignment), both for the entire TKR (37.9% vs 17.9%, p = 0.042) and for the tibial component separately (28.4% vs 6.3%, p = 0.002). Tibial slope was better achieved with CAS (58.9% vs 26.3%, p < 0.001). Operation time was 20 minutes longer with CAS. In conclusion, functional results were, statistically, marginally in favour of CAS. Also, CAS was more predictable than CONV for mechanical alignment and positioning of the prosthesis. However, the long-term outcomes must be further investigated.

Cite this article: Bone Joint J 2014; 96-B:609–18.

The performance of two hydroxyapatite-coated acetabular cups compared with Charnley cups. From the Norwegian Arthroplasty Register

We have compared the survival of two hydroxyapatite (HA)-coated cups, 1208 Atoll hemispheric and 2641 Tropic threaded, with cemented Charnley all-polyethylene cups (16 021) using the Cox regression model. The Tropic cup used in combination with an alumina ceramic femoral head, had good results, similar to those of the Charnley cup. When used in combination with a stainless-steel head, however, the risk of revision beyond four years was increased 3.4 times for the Tropic cup compared with the Charnley cup (p < 0.001). Over the same period, the Atoll cup had an increased risk of revision of 3.8 times when used with the alumina heads (p < 0.001) and an increased risk of 6.1 times when used with stainless-steel heads (p < 0.001). Revision because of wear and osteolysis was more common with both types of HA-coated cup than with the Charnley cup. The rate of revision of the Atoll cup because of aseptic loosening was also increased. We found that HA-coated cups did not perform better than the Charnley cup.

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).

A multifactorial analysis of factors related to lethality after treatment of perforated gastroduodenal ulcer. 1935-1985

One thousand one hundred and twenty-eight patients treated for perforated gastroduodenal ulcer during the years 1935-1985 were studied at the Haukeland University Hospital. The majority of patients (97.7%) were treated surgically. The data was analyzed by contingency tables and chi square testing, and a stepwise logistic regression analysis was performed in order to reveal interactions between variables and to elucidate time trends in lethality rates. The total postperforation lethality was 7.4%, the postsurgical death rate was 6.6%, and the death rate among conservatively treated patients was 42.3%. Lethality was significantly influenced by year of hospital admission and increased markedly with the age of the patients. For all age groups, the lethality decreased markedly with time. Treatment delay was associated with a moderate but significant increase in lethality. In patients with gastric ulcer the lethality was 3.6 times higher than in those with duodenal ulcer. The death rate was similar in the duodenal and pyloric ulcer groups. Death rate decreased with time in both stomach ulcer, duodenal, and pyloric ulcer patients. There was no sex difference and no difference between patients treated with simple suture or gastric resection.

The type of cement and failure of total hip replacements

Using data from the Norwegian Arthroplasty Register, we have the assessed survival of 17 323 primary Charnley hip prostheses in patients with osteoarthritis based upon the type of cement used for the fixation of the implant.

Overall, 9.2% had been revised after follow-up for ten years; 71% of the failures involved aseptic loosening of the femoral component. We observed significantly increased rates of failure for prostheses inserted with CMW1 and CMW3 cements. Using implants fixed with gentamicin-containing Palacos cement as the reference, the adjusted Cox regression failure rate ratios were 1.1 (95% CI 0.9 to 1.4) for implants cemented with plain Palacos, 1.1 (95% CI 0.7 to 1.6) for Simplex, 2.1 (95% 1.5 to 2.9) for gentamicin-containing CMW1, 2.0 (95% CI 1.6 to 2.4) for plain CMW1 and 3.0 (95% CI 2.3 to 3.9) for implants fixed with CMW3 cement. The adjusted failure rate at ten years varied from 5.9% for implants fixed with gentamicin-containing Palacos to 17% for those fixed with CMW3.

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.

The impact of physical function and pain on work status at 1-year follow-up in patients with back pain

STUDY DESIGN

A randomized, controlled trial.

OBJECTIVE

To examine the impact of physical function and pain on work status in patients who are long-term sick-listed because of back pain.

SUMMARY OF BACKGROUND DATA

Sickness benefit is granted to a person who is incapable of working because of reduced functioning. Improved physical function and decrease of pain may be important in considering return to work.

METHODS

Physical performance (five activities), disability, and pain (self-reported questionnaires) were assessed at baseline and at the 1-year follow-up evaluation in 117 patients randomized to an intervention group (n = 81) and a control group (n = 36).

RESULTS

At the 1-year follow-up evaluation, 50% had returned to work. Statistically significant improvements were demonstrated from baseline to follow-up evaluation in returners to work: in the intervention group on all tests and in the control group on all except two performance tests. Improvement measures discriminated between returners and nonreturners to work in the intervention group on all physical tests and a pain test and in the control group on three physical tests and a pain test. In the intervention group, odds ratios for not having returned to work were high when test measures at follow-up indicated markedly impaired physical function and high pain; in the control group, this appeared in high pain.

CONCLUSIONS

Return to work was related to physical function and pain. More importance seemed to be attributed to physical performance in the intervention group than in the controls as a basis for returning patients to work.

Oxinium modular femoral heads do not reduce polyethylene wear in cemented total hip arthroplasty at five years: a randomised trial of 120 hips using radiostereometric analysis

We report the five-year outcome of a randomised controlled trial which used radiostereometric analysis (RSA) to assess the influence of surface oxidised zirconium (OxZr, Oxinium) on polyethylene wear in vivo. A total of 120 patients, 85 women and 35 men with a mean age of 70 years (59 to 80) who were scheduled for primary cemented total hip arthroplasty were randomly allocated to four study groups. Patients were blinded to their group assignment and received either a conventional polyethylene (CPE) or a highly cross-linked (HXL) acetabular component of identical design. On the femoral side patients received a 28 mm head made of either cobalt-chromium (CoCr) or OxZr. The proximal head penetration (wear) was measured with repeated RSA examinations over five years. Clinical outcome was measured using the Harris hip score. There was no difference in polyethylene wear between the two head materials when used with either of the two types of acetabular component (p = 0.3 to 0.6). When comparing the two types of polyethylene there was a significant difference in favour of HXLPE, regardless of the head material used (p < 0.001). In conclusion, we found no advantage of OxZr over CoCr in terms of polyethylene wear after five years of follow-up. Our findings do not support laboratory results which have shown a reduced rate of wear with OxZr. They do however add to the evidence on the better resistance to wear of HXLPE over CPE.

The performance of two hydroxyapatite-coated acetabular cups compared with Charnley cups

We have compared the survival of two hydroxyapatite (HA)-coated cups, 1208 Atoll hemispheric and 2641 Tropic threaded, with cemented Charnley all-polyethylene cups (16 021) using the Cox regression model.

The Tropic cup used in combination with an alumina ceramic femoral head, had good results, similar to those of the Charnley cup. When used in combination with a stainless-steel head, however, the risk of revision beyond four years was increased 3.4 times for the Tropic cup compared with the Charnley cup (p < 0.001). Over the same period, the Atoll cup had an increased risk of revision of 3.8 times when used with the alumina heads (p < 0.001) and an increased risk of 6.1 times when used with stainless-steel heads (p < 0.001). Revision because of wear and osteolysis was more common with both types of HA-coated cup than with the Charnley cup. The rate of revision of the Atoll cup because of aseptic loosening was also increased.

We found that HA-coated cups did not perform better than the Charnley cup.

The influence of acetabular inclination angle on the penetration of polyethylene and migration of the acetabular component

In this prospective study we studied the effect of the inclination angle of the acetabular component on polyethylene wear and component migration in cemented acetabular sockets using radiostereometric analysis.

A total of 120 patients received either a cemented Reflection All-Poly ultra-high-molecular-weight polyethylene or a cemented Reflection All-Poly highly cross-linked polyethylene acetabular component, combined with either cobalt–chrome or Oxinium femoral heads. Femoral head penetration and migration of the acetabular component were assessed with repeated radiostereometric analysis for two years. The inclination angle was measured on a standard post-operative anteroposterior pelvic radiograph. Linear regression analysis was used to determine the relationship between the inclination angle and femoral head penetration and migration of the acetabular component.

We found no relationship between the inclination angle and penetration of the femoral head at two years’ follow-up (p = 0.9). Similarly, our data failed to reveal any statistically significant correlation between inclination angle and migration of these cemented acetabular components (p = 0.07 to p = 0.9).