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1.  The incidence of late prosthetic joint infections 
Acta Orthopaedica  2015;86(3):321-325.
Background and purpose
Late prosthetic joint infections (PJIs) are a growing medical challenge as more and more joint replacements are being performed and the expected lifespan of patients is increasing. We analyzed the incidence rate of late PJI and its temporal trends in a nationwide population.
Patients and methods
112,708 primary hip and knee replacements performed due to primary osteoarthritis (OA) between 1998 and 2009 were followed for a median time of 5 (1–13) years, using data from nationwide Finnish health registries. Late PJI was detected > 2 years postoperatively, and very late PJI was detected > 5 years postoperatively.
During the follow-up, involving 619,299 prosthesis-years, 1,345 PJIs were registered: cumulative incidence 1.20% (95% CI: 1.13–1.26) (for knees, 1.41%; for hips, 0.92%). The incidence rate of late PJI was 0.069% per prosthesis-year (CI: 0.061–0.078), and it was greater after knee replacement than after hip replacement (0.080% vs. 0.057%, p = 0.006). The incidence rate of very late PJI was 0.051% per prosthesis-year (CI: 0.042–0.063), 0.058% for knees and 0.044% for hips (p = 0.2). The incidence rate of late PJI varied between 0.041% and 0.107% during the years of observation without any temporal trend (incidence rate ratio (IRR) = 0.98, 95% CI: 0.93–1.03). Very late PJI increased from 0.026% in 2004 to 0.056% in 2010 (IRR = 1.11, 95% CI: 1.02–1.20).
In our nationwide study, the incidence rate of late PJI after hip or knee arthroplasty was approximately 0.07% per prosthesis-year. The incidence of very late PJI appeared to increase.
PMCID: PMC4443453  PMID: 25813645
2.  Risk factors for perioperative hyperglycemia in primary hip and knee replacements 
Acta Orthopaedica  2015;86(2):175-182.
Background and purpose
Background and purpose — Perioperative hyperglycemia has been associated with adverse outcomes in several fields of surgery. In this observational study, we identified factors associated with an increased risk of hyperglycemia following hip and knee replacement.
Patients and methods
Patients and methods — We prospectively monitored changes in glucose following primary hip and knee replacements in 191 patients with osteoarthritis. Possible associations of patient characteristics and operation-related factors with hyperglycemia (defined as glucose > 7.8 mmol/L in 2 consecutive measurements) and severe hyperglycemia (glucose > 10 mmol/L) were analyzed using binary logistic regression with adjustment for age, sex, operated joint, and anesthesiological risk score.
Results — 76 patients (40%) developed hyperglycemia, and 48 of them (25% of the whole cohort) had severe hyperglycemia. Glycemic responses were similar following hip replacement and knee replacement. Previously diagnosed diabetes was associated with an increased risk of hyperglycemia and severe hyperglycemia, compared to patients with normal glucose metabolism, whereas newly diagnosed diabetes and milder glucose metabolism disorders had no effect. In patients without previously diagnosed diabetes, increased values of preoperative glycosylated hemoglobin (HbA1c) and fasting glucose on the day of operation were associated with hyperglycemia. Higher anesthesiological risk score—but none of the operation-related factors analyzed—was associated with an increased risk of hyperglycemia.
Interpretation — Perioperative hyperglycemia is common in primary hip and knee replacements. Previously diagnosed diabetes is the strongest risk factor for hyperglycemia. In patients with no history of diabetes, preoperative HbA1c and fasting glucose on the day of operation can be used to stratify the risk of hyperglycemia.
PMCID: PMC4404767  PMID: 25409255
3.  The decline in joint replacement surgery in rheumatoid arthritis is associated with a concomitant increase in the intensity of anti-rheumatic therapy 
Acta Orthopaedica  2013;84(4):331-337.
Background and purpose
Drug-based treatment of rheumatoid arthritis (RA) has evolved markedly over the past 2 decades. Using nationwide register data, we studied how this has affected the rates of hip, knee, shoulder, and elbow replacement from 1995 to 2010.
The number of primary joint replacements was obtained from the Finnish Arthroplasty Register. To test the hypothesis that improvements in medical treatment of RA reduce the need for joint replacements, we also collected data about purchases of different disease-modifying anti-rheumatic agents (DMARDs) and biological drugs from the nationwide drug registers.
The annual incidence of primary joint replacements for RA declined from 19 per 105 in 1995 to 11 per 105 in 2010. The decline was greater for upper-limb operations than for lower-limb operations. At the same time, the numbers of individuals using methotrexate, hydroxychloroquine, and sulfasalazine (the most commonly used DMARDs) increased 2- to 4-fold.
Our results are in accordance with observations from other countries, and indicate that the use of joint replacements in RA has decreased dramatically. Our data suggest that effective medical therapy is the most likely explanation for this favorable development.
PMCID: PMC3768029  PMID: 23992137
4.  Incidence of rheumatoid arthritis-related ankle replacement and ankle arthrodesis 
Acta Orthopaedica  2013;84(4):338-341.
Background and purpose
For 20 years, medical treatment of rheumatoid arthritis (RA) has been improving and the incidence of joint surgery has decreased. We investigated the rates of primary ankle joint arthrodesis and total ankle arthroplasty in patients with RA in Finland between 1997 and 2010 to establish whether trends have changed during that period.
The annual figures for primary ankle joint arthrodeses and total ankle replacements performed in patients with RA were obtained from nationwide population-based registries. Incidences were calculated per population of 105 and they are reported in 2-year periods.
During the study period, 593 primary ankle joint arthrodeses and 318 total ankle arthroplasties were performed in patients with RA. The incidence of ankle joint arthrodesis reached its highest value (2.4/105) in 1997–1998 and it was lowest in 2001–2002 (1.1/105). After 2002, the incidence increased slightly but did not reach the level in 1997–1998, even though total ankle replacements almost ended in Finland during the period 2009–2010. From 1997, total ankle replacements increased until 2003–2004 (incidence 1.5/105) and then gradually decreased. In 2009–2010, the incidence of total ankle replacements was only 0.4/105.
During the observation period 1997–2010, while total ankle replacements generally became more common in patients with RA, the incidence of primary ankle joint arthrodesis decreased and did not increase in the period 2009-2010, even though total ankle replacement surgery almost ended in Finland. No change in the incidence of these operations, when pooled together, was observed from 1997 to 2010.
PMCID: PMC3768030  PMID: 23992138
5.  Predictors of mortality following primary hip and knee replacement in the aged 
Acta Orthopaedica  2013;84(1):44-53.
Background and purpose
High age is associated with increased postoperative mortality, but the factors that predict mortality in older hip and knee replacement recipients are not known.
Preoperative clinical and operative data on 1,998 primary total hip and knee replacements performed for osteoarthritis in patients aged ≥ 75 years in a single institution were collected from a joint replacement database and compoared with mortality data. Average follow-up was 4.2 (2.2–7.6) years for the patients who survived. Factors associated with mortality were analyzed using Cox regression analysis, with adjustment for age, sex, operated joint, laterality, and anesthesiological risk score.
Mortality was 0.15% at 30 days, 0.35% at 90 days, 1.60% at 1 year, 7.6% at 3 years, and 16% at 5 years, and was similar following hip and knee replacement. Higher age, male sex, American Society of Anesthesiologists risk score of > 2, use of walking aids, preoperative walking restriction (inability to walk or ability to walk indoors only, compared to ability to walk > 1 km), poor clinical condition preoperatively (based on clinical hip and knee scores or clinical severity of osteoarthritis), preoperative anemia, severe renal insufficiency, and use of blood transfusions were associated with higher mortality. High body mass index had a protective effect in patients after hip replacement.
Postoperative mortality is low in healthy old joint replacement recipients. Comorbidities and functional limitations preoperatively are associated with higher mortality and warrant careful consideration before proceeding with joint replacement surgery.
PMCID: PMC3584602  PMID: 23244785
6.  Prevention of deep infection in joint replacement surgery 
Acta Orthopaedica  2010;81(6):660-666.
PMCID: PMC3216074  PMID: 21110700
7.  Younger age increases the risk of early prosthesis failure following primary total knee replacement for osteoarthritis 
Acta Orthopaedica  2010;81(4):413-419.
Background and purpose
Total knee replacements (TKRs) are being increasingly performed in patients aged ≤ 65 years who often have high physical demands. We investigated the relation between age of the patient and prosthesis survival following primary TKR using nationwide data collected from the Finnish Arthroplasty Register.
From Jan 1, 1997 through Dec 31, 2003, 32,019 TKRs for primary or secondary osteoarthritis were reported to the Finnish Arthroplasty Register. The TKRs were followed until the end of 2004. During the follow-up, 909 TKRs were revised, 205 (23%) due to infection and 704 for other reasons.
Crude overall implant survival improved with increasing age between the ages of 40 and 80. The 5-year survival rates were 92% and 95% in patients aged ≤ 55 and 56–65 years, respectively, compared to 97% in patients who were > 65 years of age (p < 0.001). The difference was mainly attributable to reasons other than infections. Sex, diagnosis, type of TKR (condylar, constrained, or hinge), use of patellar component, and fixation method were also associated with higher revision rates. However, the differences in prosthesis survival between the age groups ≤ 55, 56–65, and > 65 years remained after adjustment for these factors (p < 0.001).
Young age impairs the prognosis of TKR and is associated with increased revision rates for non-infectious reasons. Diagnosis, sex, type of TKR, use of patellar component, and fixation method partly explain the differences, but the effects of physical activity, patient demands, and obesity on implant survival in younger patients warrant further research.
PMCID: PMC2917562  PMID: 20809740
8.  Low rate of infected knee replacements in a nationwide series—is it an underestimate? 
Acta Orthopaedica  2009;80(2):205-212.
Background and purpose Specialist hospitals have reported an incidence of early deep infections of < 1% following primary knee replacement. The purpose of this study was to estimate the infection rate in a nationwide series using register-based data.
Methods The Finnish Arthroplasty Register (FAR) was searched for primary unicompartmental, total, and revision knee arthroplasties performed in 1997 through 2003 and eventual revision arthroplasties. The FAR data on revision arthroplasties was supplemented by a search of the national Hospital Discharge Register (HDR) for debridements, partial and total revision knee replacements, resection arthroplasties, arthrodeses, and amputations.
Results During the first postoperative year, 0.33% (95% CI: 0.13–0.84), 0.52% (0.45–0.60) and 1.91% (1.40–2.61) of the primary UKAs, primary TKAs, and revision TKAs, respectively, were reoperated due to infection. The 1-year rate of reoperations due to infection remained constant in all arthroplasty groups over the observation period.
The overall infection rate calculated using FAR data only was 0.77% (95% CI: 0.69–0.86), which was lower, but was not, however, statistically significantly different from the overall infection rate calculated using endpoint data combined from FAR and HDR records (0.89%; 95% CI: 0.80–0.99). FAR registered revision arthroplasties and patellar resurfacing arthroplasties reliably but missed a considerable proportion of other reoperations.
Interpretation More reoperations performed due to infection can be expected as the numbers of knee arthroplasties increase, since there has been no improvement in the early infection rate. Finnish Arthroplasty Register data appear to underestimate the incidence of reoperations performed due to infection.
PMCID: PMC2823163  PMID: 19404805
9.  Outcome of prosthesis exchange for infected knee arthroplasty: the effect of treatment approach 
Acta Orthopaedica  2009;80(1):67-77.
Background and purpose Two-stage revision remains the gold standard in the treatment of infected knee arthroplasty. Lately, good long-term results of direct exchange arthroplasty have been reported. The purpose of this literature review is to compare the clinical outcome achieved with one-stage revision and two-stage revision with different types of spacers.
Methods A thorough systematic review of literature was undertaken to idenepsy reports on the treatment alternatives. Papers written in English or including an English abstract, published from 1980 through 2005, and reporting either the success rate in eradication of infection or the clinical status achieved were reviewed. 31 original articles describing the results of 154 one-stage exchange arthoplasties and of 926 two-stage exchange arthoplasties were included. The depth of detail in the description of materials and methods varied markedly, making it impossible to perform a meta-analysis. Instead, a descriptive review of the results is presented.
Results With a follow-up of 12–122 months, the overall success rate in eradication of infection was 73–100% after one-stage revisions and 82–100% after two-stage revisions. Reinfection rates were the lowest in series where articulating cement spacers were used, though the follow-up was relatively short. Studies using articulating spacers reported the highest average postoperative ranges of motion. Otherwise, no correlations were observed between the clinical outcome and the length of follow-up, the type of revision, or the type of spacer. The clinical outcome (knee scores and range of motion) of the one-stage revisions was no different from that of the two-stage revisions.
Interpretation Two-stage exchange is an effective treatment. Mobile spacers may further improve the range of motion. More experience in one-stage revision is required in order to define its role in the management of infected knee arthroplasties.
PMCID: PMC2823239  PMID: 19234888

Results 1-9 (9)