Background: According to the mid-term results obtained from the previous registry-based studies, survival of cementless stems for aseptic loosening in younger patients with primary osteoarthritis has been better than the survival of cemented stems. However, it has not been clear if the endurance against aseptic loosening of cementless cups is comparable to that of cemented cups. The aim of the present study was to analyze population-based long-term survival rates of the cemented and cementless total hip replacements in patients under the age of fifty-five years with primary osteoarthritis in Finland.

Patients and Methods: Between 1980 and 2006, a total of 7310 primary total hip replacements performed for primary osteoarthritis in patients under the age of fifty-five years were entered in the Finnish Arthroplasty Registry. 4,032 of them fulfilled our inclusion criteria and were subjected to analysis. The implants included were classified in one of the three following groups: implants with a cementless, straight, proximally circumferentially porous-coated stem and a porous-coated press-fit cup (cementless group #1); implants with a cementless, anatomic, proximally circumferentially porous-coated and/ or hydroxyapatite-coated stem with a porous-coated and/or hydroxyapatite-coated press-fit cup (cementless group #2); and a cemented stem combined with a cemented all-polyethylene cup (the cemented group).

Results: Cementless total hip replacements, as well as cementless stems and cups analyzed separately, had a significantly reduced risk of revision for aseptic loosening compared with cemented hip replacements. The 15-year survivorship of cementless stem groups for aseptic loosening was higher than that of cemented stems (89% and 90% vs. 72%). The 15-year survivorship of cementless press-fit porous-coated cups for aseptic loosening was higher than that of cemented cups (80% vs. 71%). When revision for any reason was the end point in survival analyses, however, there were no significant differences among the groups.

Conclusions: Both cementless stems and cementless cups have better resistance to aseptic loosening than cemented implants in long term follow-up in younger patients. Even if liner-exchange revisions are taken into account, the long-term survival of cementless total hip replacements is comparable to that of cemented implants.

Aims: Nationwide, computer-based survey of all total joint arthroplasties performed in Finland has been carried out since January 1980. From these records a cohort of 9,443 patients, with 80,734 person-years, after primary operation with a total polyethylene-on-metal knee arthroplasty (TKA) has been followed up for cancer. In 1999 we published the material until December 31, 1996. The standardized incidence ratio (SIR) for all cancers was 0.98. The SIRs for non-Hodgkin lymphoma (1.40), Hodgkinñs disease (1.24), multiple myeloma (1.54) and prostate cancer (1.49) were increased, but only that of non-Hodgkin lymhoma was statistically signiþcant 3 to 10 years after the operation. The overall cancer risk after TKA done for primary osteoarthrosis appeared to be negligible. Material and methods: Follow-up for cancer was undertaken using the þles in the population-based, nationwide Finnish Cancer Registry, employing personal identiþcation numbers. Follow-up for cancer started at the date of þrst knee replacement and ended on emigration, death, or 31 December 2000, whichever occurred þrst. No subject was lost to follow-up. Standardized incidence ratios (SIRs) were calculated by dividing observed numbers of cases by expected numbers. Results: There were 2,001 men and 7,442 women left in the cohort to be followed-up. Numbers of person-years are now 15,679 and 650,552, respectively. The mean duration of follow-up per person was therefore 8,5 years. During the 21-year follow-up period, 358 cases of cancer occurred in the male subjects. The expected number was 349. In the female subjects 801 cases of cancer were observed vs. 804 expected. Combining data for men and women, the SIR for cancer at all sites was 1.00. SIRs were signiþ-cantly lower in relation to cancers of the lung (0.69), and colon (0.77). The incidence of risk of colon cancer was lower than would have been expected only in women (SIR 0.70). As far as cancers of the urinary organs is concerned, the SIR was within unity (SIR 1,03). The overall incidence of non-Hodgkin lymphoma (extranodal sites included) was elevated, but without any statistical signiþ-cance (SIR 1.22). The SIR values for multiple myeloma and leucemia have reduced to 0.80 and 0.53. Conclusions: We conclude, that this large nation-wide material could not establish any association between TKA and the all-over incidence of remote or adjacent cancers; on the contrary incidences of certain cancers were in fact lower than those reported in the formed material with four years less follow-up. All the alarming SIRs in the former material, especially those with non-Hodgin lym-phoma, urinary tract cancers and leucemia, have now reduced and are less than unity.

Corrosion and wear of total hip (THA) and knee (TKA) prostheses extricate metallic particles and soluble metallic compounds. The oncogenic risk of these products should be known. Material and methods: Three Nordic cohorts of total hip (THA) and total knee arthroplasty (TKA) patients operated on for primary osteoarthrosis during 1967–1995 were combined for meta-analysis. The number of THA patients was 49,000 and TKA patients 24,000 totaling 497,000 person years. The mean follow-up time was 6.8 years. Standardized incidence ratios (SIRs) with 95% conþdence intervals (95% CI) were calculated for the observed and expected number of cancers. The expected numbers were based on national incidence rates. Results: The allover SIRs as well as the site-speciþc cancer incidences were similar for the THA and TKA patients. The observed number of all site cancers was 7639 and 8202 expected (SIR 0.93, 95% CI 0.91–0.95). The SIR for lung cancer (0.69, 0.64–0.75) was reduced. The incidence was also low for cancers of the stomach (SIR 0.76, 0.67–0.84), colon (SIR 0.86, 0.79–0.93) and rectum (SIR 0.89, 0.80–0.98). Slightly elevated SIRs were seen among TKA patients in cancer of the endometrium and prostate and among both THA and TKA patients in skin melanoma. Conclusions: Total cancer risk was signiþcantly reduced among THA and TKA patients due to decrease of respiratory and gastrointestinal cancers. The present results do not suggest any oncogenic risk of the components of hip and knee prostheses and their degradation products.

Aims: The most common complications after total knee arthroplasty (TKA) are the result of patellar complications. The causes of patellar problems range from sub-luxation, dislocation, component loosening, rupture of the patellar tendon, excess wear of the polyethylene (especially after metal backing), retropatellar pain, and patellar fracture. The incidence of these patellar complications after TKA ranges from 5–30%. Selective retention of the patella has been recommended more recently although there are still potential problems of maltracking and anterior knee pain. According to the nationwide registration of all TKAs in Finland since 1980 it seems evident that interest of patellar retention during the primary operation has now been stabilized at the level of about 55 per cent. At the same time there are, however, quite a high incidence of reoperations done due to patellar complications or later resurfacing of the patella in connection of revisions done with other indications. Methos:

Database of the Finnish Arthroplasty Register was evaluated from the years 1999 and 2000 focusing on the reoperations done either due to patellar complication (in the notiþcation: indication for revision) or due to other reason (to be speciþed in full text). These were further divided into three main categories: removal or fracture of patellae, delayed resurfacing due to patellar pain or maltracking, and component loosening.

Conclusions: Reoperations done due to the patellar complications and/or later resurfacing of patellae mean quite a notable work-load; 31,7 to 33,6 per cent of all TKA revisions done in the years 1999 and 2000, respectively. Of the total of 113 delayed patellar resurfacing operations, almost 50 per cent were done in connection to revisions primarily due to other reasons, usually after excess liner wear. In conclusion we can say, that ÒprimaryÒ patellar complications (after patellar resurfacing in the primary operation) encountered about 15 per cent of all revisions, and those done in the Òsecondary phaseÒ (after retention of patella) another 15 to 16 per cent. This is in accordance with the results gained in the other Nordic Registers; in Norway ÒprimaryÒ/loose 16,5% of all TKA revisions. It seems that the need for a secondary patellar replacement in unreplaced cases was balanced by the need for revisions of failed patellar components in patellar replaced cases.

Aims: In 1999 we published a cohort of 24,638 polyethylene-on-metal total hip arthroplasty (THA) patients followed up for cancer, using Finnish Cancer Registry data, from 1980 to 1995. The number of person-years was then 173,022 (until 31st Dec, 1996). During follow-up, there were statistically significantly fewer cancers among the THA patients (standardized incidence ratio [SIR], 0.91; 95% confidence interval [Cl], 0.87–0.94). There was no significantly increased risk at any site, and for certain cancers that was even below the unity (lung and stomach).

On the longer run, however, certain tendency for increased risk for cancer of the urinary bladder, myeloma, and leukemia could be observed; SIRs were greater than unity with the THA patients followed up 3 to 9 years. Further follow-up of the cohort is therefore needed. Methods: The follow-up of the same cohort, originally identified in the National Register of Arthroplasties, maintained by the National Agency for Medicines (primary THA with primary arthritis as the indication) was expanded with a four year period (from 1st of Jan 1997 to 31st of Dec 2000). Follow-up for cancer was undertaken using the files in the population-based, nationwide Finnish Cancer Registry, employing personal identification numbers.

Follow-up for cancer started at the date of first hip replacement and ended on emigration, death, or December 31, 2001, whichever occurred first. Multiple cancers were taken account of in similar ways in relation to observed and expected numbers of cases. Results: After excluding revision and infective or systemic disease as indications for operation, there were 9,479 men and 15,157 women in the cohort followed. The updated numbers for person-years were 89,295 for males and 153,759 for females. The mean duration of follow-up was now 9,9 years. The total risk for cancer was now 0.93 (95%Cl 0.90–0.96) and that for stomach 0.89, for colon 0.90, lung 0.64, for urinary organs 1.01, and for connective tissues 0.88. The SIRs for non-Hogkin lymphoma, myeloma and leucemia were all under the untity, 0.88, 1.09 and 0.73, respectively, without any tendency for increased risk in the follow-up of plus ten years.

Conclusions: These findings indicate that the risk of hematopoietic cancers is not increased after THA using polyethylene-on-metal prostheses. Expanding of the follow-up with four years did not markedly change the profile of the SIRs at any specific site, and contrary to our earlier report there were increased risk left of myeloma and leucemia with increased follow-up time. The SIRs associated with soft tissue cancers and bone sarcomas were not significantly different from unity. No sarcomas developed at the site of a prosthesis.