The Swedish Knee Arthroplasty study with special reference to unicompartmental prostheses.

The Swedish Knee Arthroplasty study has prospectively registered and followed knee arthroplasties done in Sweden since 1976. Demography, epidemiology and general knee prosthetic biofunction is given for 30,003 primary knee arthro-plasties and their revisions through 1992. The annual number of knee arthroplasties increased fourth fold while the relative use of Unicompartmental knee arthroplasty (UKA) decreased as Tricompartmental knee arthroplasty (TKA) increased. The 5-year Cumulative revision rate (CRR) decreased for each 5-year period studied for TKA in osteoarthrosis (OA) but for UKA no change was seen. The annual percentage of revisions has diminished from 10% to 5% In OA, modern TKA have a lower CRR than UKA, with a 5-year CRR of 3% and 8%, respectively. A problem was identified with the PCA Uni prosthesis (femoral loosening and excessive HDPE wear) and the Oxford Meniscal knee (dislocating meniscus and femoral loosening) with 5-year CRR of 16% and 10% respectively, compared to 5% for the Marmor. Two relatively unchanged prostheses, Marmor and Total Condylar, were used from 1975-1986 with continuous improvement in CRR over time. This indicates that factors other than prosthetic design affect the CRR. In failed UKA for OA, revision with exchange using new unicompartmental components gave a 5-year Cumulative rerevision rate (CRRR) of 26% while conversion to TKA gave 7%. Also addition of components in the contralateral compartment gave an inferior 5-year CRRR of 17%. Failed UKA should be converted to TKA. In comparison modern primary TKA had a CRR of 3%. A cohort of 14,551 patients followed for 66,622 patient years was matched with the Swedish National Cancer Registry. The cancer incidence was not increased after knee arthroplasty

Age, bodyweight, smoking habits and the risk of severe osteoarthritis in the hip and knee in men

Background: The objective of this study was to estimate the risk of severe osteoarthritis, with the need for arthroplasty, in the knee and/or hip according to body mass index (BMI) both within a normal range and in persons with high BMI. Furthermore, we wanted to study the significance of smoking. Methods: This study identifies male construction workers participating in a national health control program (n = 320,192). The incidence rate for joint replacement was found by matching with the Swedish hospital discharge register between 1987 and 1998. BMI and smoking habit was registered at the time of the health examination. Results: In total 1495 cases of osteoarthritis of the hip and 502 cases of osteoarthritis of the knee were identified and included in this analysis. The incidence rate was found to increase linearly to the BMI even within low and,normal' BMI. The relative risk for osteoarthritis of the hip was more than two times higher in persons with a BMI of 20-24 than in men with a BMI 17-19. There was almost a doubling of the risk of severe knee 2 osteoarthritis with an increase in BMI of 5 kg/m(2). Smoker had a lower risk of osteoarthritis than non-smokers and ex-smokers. Conclusions: BMI is an important predictor of osteoarthritis even within normal BMI. A decreased risk of osteoarthritis of the hip was found in smokers, but the effect was weak compared to that of BMI or age. Contrary to studies of radiographic osteoarthritis our study indicates higher risk of hip than of knee osteoarthritis

Revision of unicompartmental knee arthroplasty: outcome in 1,135 cases from the Swedish Knee Arthroplasty study

From 1975 through 1995, 45,025 knee arthroplasties were recorded in the prospective Swedish Knee Arthroplasty study. By the end of 1995, 1,135 of 14,772 primary unicompartmental knee arthroplasties (UKA) for localized, mainly medial arthrosis had been revised. The Marmor/Richards and St. Georg sledge/Endo-Link prostheses were used in 65%. Mean age at revision was 72 (71) years. 232 revisions were performed as an exchange UKA (partial in 97) and 750 as a total knee arthroplasty (TKA). 153 were revised by other modes. In medial UKA, the indication for revision was component loosening in 45% and joint degeneration in 25% and in lateral UKA, the corresponding figures were 31% and 35%, respectively. In 94 cases, unicompartmental components were added to the initially untreated compartment, in 14 with partial exchange of a component. The CRRR was estimated using survival statistics. After only 5 years, the risk of having a second revision was more than three times higher for failed UKAs revised to a new UKA (cumulative rerevision rate (CRRR 26%) than for those revised to a TKA (CRRR 7%). This difference remained, even if those revised before 1985, when modern operating technique was introduced, were excluded (CRRR 31% and 5%, respectively). UKA is a safe primary procedure, when performed with well-designed components and modern surgical technique. It gives documented good patient satisfaction, range of motion, pain relief and relatively few serious complications. However, once failed, the knee should be revised to a TKA. This applies to most modes of failure. Not even joint degeneration of the unoperated compartment can be safely treated by adding contralateral components; CRRR after this procedure was 17%, while it was 7% when converted to a TKA

The Swedish knee arthroplasty register. A nation-wide study of 30,003 knees 1976-1992

1976 through 1992, 30,003 primary knee arthroplasties and their revisions have been recorded in a nation-wide Swedish study. We report on the structure of the register, demographic data and survivorship. We found that operations for osteoarthrosis (OA) counted for the increase in number of arthroplasties in contrast to rheumatoid arthritis (RA), where the number had slightly declined. For primary operations, the total knee prostheses have practically eliminated other types in RA and are steadily gaining popularity in OA at the expense of the unicompartmental prostheses. Total knee replacements showed gradually improving survival even in unchanged designs while the unicompartmental prostheses don't, partly because of newly introduced inferior designs. We also found that failed unicompartmental prostheses were best replaced with a tricompartmental prosthesis and that a total revision was to be preferred when a tricompartmental tibial component failed. The risk of the most devastating complications, e.g., infection, leading to extraction of the prosthesis or arthrodesis has decreased considerably also in the last years

Knee arthroplasty in rheumatoid arthritis. A report from the Swedish Knee Arthroplasty Register on 4,381 primary operations 1985-1995

The Swedish Knee Arthroplasty Register has data on 4,381 primary operations performed 1985-1995 for rheumatoid arthritis. Of these, 192 were performed with unicompartmental prostheses and 4143 with tricompartmental. 77% were women and the mean age was 66 years. There were 126 first, 20 second, and 1 third revision in tricompartmental arthroplasties, mainly for loosening, infection and patellar problems. There were 38 first, 3 second, and 1 third revision in unicompartmental arthroplasties, mainly for progression of RA and loosening. Cumulative revision rates (Kaplan-Meier) were calculated. Tricompartmental knees had a 10-year cumulative revision rate of 5% and uni-knees 25%. Patients treated before 1990, men and patients younger than 55 had higher revision rates than patients treated after 1990, women and older patients, respectively. Cemented tibial components resulted in lower revision rates than uncemented ones. There was no significant difference in revision rates between patellar replaced and unreplaced knees or between the 9 commonest implant types

Incidence of surgically treated osteoarthritis in the hip and knee in male construction workers

Objective: Occupational workload has been associated with an increased risk of osteoarthritis. The objective was to further examine the association between workload and occurrence of osteoarthritis and in particular to study whether heavy workload has similar importance as a causative factor for osteoarthritis of the hip and knee. Methods: In a cohort study, the authors investigated the incidence of surgically treated osteoarthritis in the hip and knee among men employed in the Swedish construction industry (n = 204 741). Incident cases were found by linkage with the Swedish hospital discharge register between 1987 and 1998. Incidence rates adjusted for age and BMI were compared between different occupational groups. Results: The incidence rates for osteoarthritis in hip and knee were positively correlated (r = 0.62; p = 0.01). There was a significantly increased risk of surgically treated osteoarthritis in the knee among floor layers, asphalt workers, sheet-metal workers, rock workers, plumbers, brick layers, wood workers and concrete workers. Even if there was a trend towards increased relative risks for osteoarthritis in the hip in floor layers, asphalt workers, wood workers and concrete workers they were not statistically significant. The relative risk for surgically treated osteoarthritis of the knee was 4.7 (95% CI 1.8 to 12.3) among floor layers, indicating an attributable fraction for work factors of 79%. Conclusions: This study shows that some work-related factors seem to be risk factors for osteoarthritis both in the knee and hip. However, the risk factors seem to be of greater importance for osteoarthritis in the knee compared with the hip. This study indicates that at least 50% of the cases of severe osteoarthritis of the knee can be prevented through decreasing occupational risk factors in some occupational groups

The patella in total knee arthroplasty: resurfacing or nonresurfacing of patella

Data from the Swedish Knee Arthroplasty Registry were analyzed to compare bi- and tricompartmental knee arthroplasties carried out in patients operated on for arthrosis in 1990-1996. Of the 16,607 primary arthroplasties that were carried out there were 5,139 with patellar replacement in the primary procedure and 10,928 without. By April 1998, 280 revisions were performed, 250 of these cases were analyzed in this study. Patella-related complications were commonly the reason for early revision: in 99 of the 168 knees with a primary bicompartmental procedure and in 36 of the 82 knees with a primary tricompartmental procedure. This presentation merely analyzes the extent of patellar problems in knee arthroplasty, as a detailed analysis of the causes of this common problem is not possible using data from a national multicenter study