Unicondylar knee replacement for primary osteoarthritis: a prospective follow-up study of 1,819 patients from the Finnish Arthroplasty Register

BACKGROUND: The choice and use of unicondylar knee arthroplasty (UKA) has gone through a nation wide resurgence at the start of the 21st century in Finland. We evaluated the population-based survival of UKA in patients with primary osteoarthritis (OA) in Finland, and the factors affecting their survival. METHOD: The Finnish Arthroplasty Register was established in 1980. During the years 1985-2003, 1,928 primary UKAs were recorded in the register; 1,819 of these were performed for primary OA. Of these 1,819 UKAs, we selected for further analysis implants that had been used in more than 100 operations during the study period. The survival rates of UKAs were analyzed using Kaplan-Meier analysis and the Cox regression model. RESULTS: Analysis of the whole study period showed that UKAs had a 73% (95% CI: 70-76) survival rate at 10 years, with revision for any reason as the end point. Those patients who received the Oxford menisceal bearing unicondylar (n = 1145) had a survival rate of 81% (95% CI: 72-89) at 10 years. The group that received the Miller-Galante II unicondylar (n = 330) had a 79% survival rate (95% CI: 71-87) at 10 years, whereas the Duracon (n = 196) had a survival rate of 78% (95% CI: 72-84) and the PCA (n = 146) had a survival rate of 53% (95% CI: 45-60) at 10 years. The number of UKA operations in Finland has increased markedly in recent years. At the time of operation, the mean age of the patients was 65 (38-91) years. Younger patients (相似文献   

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.     

A 15-year follow-up study of 4606 primary total knee replacements

This is a 15-year follow-up observational study of 4390 patients with 4606 primary total knee replacements (TKRs) implanted in the Trent health region between 1990 and 1992. The operations were performed in 21 hospitals, including both district general and teaching hospitals, with 77 different surgeons as named consultant. The main objective was to analyse the survival of the patients and of the prostheses, and to evaluate what impact different variables have on survival. In addition, the 1480 patients (33.7%) (1556 TKRs) alive at 15 years following operation were sent a self-administered questionnaire which examined their level of satisfaction, of pain, and their quality of life at 15 years. Completed responses were received from 912 TKRs (58.6%). Three survival curves were constructed: a best-case scenario based on the patients entered into the life tables, another included failures not reported in the revision database, and a third worst-case scenario based on all patients lost to follow-up presumed to have had a failed primary TKR. In the best-case scenario survival at 15 years was 92.2%, and in the worst-case scenario was 81.1%. Survival was significantly increased in women and older patients (Mantel-Cox log-rank test, p < 0.005 and p < 0.001, respectively). Revision as a result of infection was required in 40 TKRs (18.8%) representing 0.87% of the original cohort. The limited information available from the questionnaire indicated that satisfaction was less frequent among men, patients with osteoarthritis and those who required revision (chi-squared test, p < 0.05, p < 0.05 and p < 0.0001, respectively). With regard to pain, older patients, females and patients who still had their primary replacement in place at 15 years, reported the least pain (chi-squared test for trends, p < 0.0005, p < 0.005 and p < 0.0001, respectively). The reported quality of life was not affected by any variable.     

Predictors of mortality following primary hip and knee replacement in the aged: A single-center analysis of 1,998 primary hip and knee replacements for primary osteoarthritis

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.

Methods 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.

Results 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.

Interpretation 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.     

Higher risk of revision for partial knee replacements in low absolute volume hospitals: data from 18,134 partial knee replacements in the Dutch Arthroplasty Register

Background and purpose — Partial knee replacement (PKR) survival rates vary a great deal among registries and cohort studies. These discrepancies can largely be attributed to inappropriate indications of the PKR and low thresholds for revision, but also to the PKR volume. This study used Dutch Arthroplasty Register data to analyze whether absolute PKR or proportional PKR hospital volume is associated with the risk of revision.Patients and methods — 18,134 PKRs were identified in the Dutch Arthroplasty Register from 2007 to 2016. For each year, hospitals were divided into 4 groups based on the quartiles for the absolute volume (< 22, 22–36, 36–58 and > 58 PKRs per year) and the proportional volume (< 8.5, 8.6–14.2, 14.3–25.8 and > 25.8% PKRs). Kaplan–Meier survival analysis was performed to determine survival rates. A multivariable Cox regression adjusted for age category, sex, ASA score, year of surgery, diagnosis, unicondylar side, and type of hospital was used to estimate hazard ratios (HR) for revision.Results and interpretation — Proportional PKR volume did not, but absolute PKR volume did influence the risk of revision. The adjusted HR for hospitals with an absolute volume of 22–36 PKRs per year was 1.04 (95% CI 0.91–1.20), 0.96 (CI 0.83–1.10) for the hospitals with 36–58 PKRs, and 0.74 (CI 0.62–0.89) for hospitals with more than 58 PKRs compared with hospitals that had fewer than 22 PKRs per year. So, patients treated with a PKR in a high absolute volume hospital have a lower risk of revision compared with those treated in a low absolute volume hospital.

One of the advantages of partial knee replacement (PKR) is that the native mechanics of the knee are largely preserved, whereas in total knee replacement (TKR) the anterior cruciate ligament is sacrificed and the mechanics change substantially (Laurencin et al. 1991). This might contribute to better a postoperative clinical outcome following PKR compared with TKR (Liddle et al. 2015). Also, a lower risk of complications has been reported for PKR (Liddle et al. 2014a, Beard et al. 2019). Furthermore, a recent randomized trial demonstrated similar Oxford Knee Scores, a higher perceived knee improvement, higher willingness to undergo the operation again, and better cost-effectiveness after PKR compared with TKR at 5 years’ follow-up (Beard et al. 2019). Nevertheless, since its introduction, the PKR has been a topic of debate due to the diversity in reported long-term survival rates.Multiple studies have reported survival rates over 94% at 10 years (Svärd and Price 2001, Pandit et al. 2011, Lisowski et al. 2011, Burnett et al. 2014). However, registries and low-volume PKR centers showed significantly lower survival rates at 5 and 10 years (Baker et al. 2012, Schroer et al. 2013, Badawy et al. 2017). The discrepancies in survival rates can largely be attributed to low absolute and proportional PKR volume (Liddle et al. 2015, Badawy et al. 2017). Badawy et al. showed that in the Nordic countries the most common annual absolute hospital volume was 1–3 PKRs per year, which could have resulted in the reported low survival rates.The use of PKR is generally accepted in the Netherlands. However, large variation in knee replacement volume exists between hospitals. Data from high-volume and low-volume hospitals are available in the Dutch Arthroplasty Register (LROI)(Van Steenbergen et al. 2015). The LROI database contains data concerning orthopedic joint implants in the Netherlands since 2007. This study investigates whether absolute PKR hospital volume and proportional PKR hospital volume are associated with higher risk of revision using population-based national register data.     

Risk factors for total ankle arthroplasty failure: A Dutch Arthroplasty Register study

BackgroundStudies concerning total ankle arthroplasty could be influenced by several forms of bias. Independent national arthroplasty registries represent objective data on survival and patient reported outcomes. The aim of this study was to determine survival and identify risk factors for early failure in a nationwide series of total ankle arthroplasties from the Dutch Arthroplasty Register (LROI).Patients and methodsData of 810 patients, who received 836 total ankle arthroplasties between 2014 and 2020 were obtained from the Dutch Arthroplasty Register (LROI) with a median follow-up of 38 months (range 1–84 months). Survival was expressed in Kaplan-Meier analysis and associated hazard ratios for implant failure were determined. Implant failure was defined as the need for revision surgery for any reason or (pan)arthrodesis.ResultsDuring follow-up, we recorded 39 failures (4.7%) resulting in a implant survival of 95.3% with a median follow-up of 38 months (range 1–84 months). Medial malleolus osteotomy (HR = 2.27), previous surgery (HR = 1.83), previous osteotomy (HR = 2.82) and previous ligament reconstruction (HR = 2.83) all showed potentially clinically meaningful associations with a higher incidence of implant failure, yet only previous OCD treatment (HR = 6.21), BMI (HR = 1.09) and age (HR = 0.71) were statistically significant.InterpretationExcellent short-term survival (95.3%) with a median follow-up of 38 months was reported for TAA patients from the Dutch Arthroplasty Register. Patients with a lower age, a higher BMI or who had a prior surgical OCD treatment before TAA surgery appear to have a higher risk for revision after short-term clinical follow-up. Thorough patient selection with emphasis on risk factors associated with early implant failure might be essential to improve TAA survivorship.     

A case-control study of spontaneous patellar fractures following primary total knee replacement

Peri-prosthetic patellar fracture following resurfacing as part of total knee replacement (TKR) is an infrequent yet challenging complication. This case-control study was performed to identify clinical, radiological and surgical factors that increase the risk of developing a spontaneous patellar fracture after TKR. Patellar fractures were identified in 74 patients (88 knees) from a series of 7866 consecutive TKRs conducted between 1998 and 2009. After excluding those with a previous history of extensor mechanism realignment or a clear traumatic event, a metal-backed patella, any uncemented component or subsequent infection, the remaining 64 fractures were compared with a matched group of TKRs with an excellent outcome defined by the Knee Society score. The mean age of patients with a fracture was 70 years (51 to 81) at the time of TKR. Patellar fractures were detected at a mean of 13.4 months (2 to 84) after surgery. The incidence of patellar fracture was found to be strongly associated with the number of previous knee operations, greater pre-operative mechanical malalignment, smaller post-operative patellar tendon length, thinner post-resection patellar thickness, and a lower post-operative Insall-Salvati ratio. An understanding of the risk factors associated with spontaneous patellar fracture following TKR provides a valuable insight into prevention of this challenging complication.     

Similar early mortality risk after cemented compared with cementless total hip arthroplasty for primary osteoarthritis: data from 188,606 surgeries in the Nordic Arthroplasty Register Association database

Background and purpose — Current literature indicates no difference in 90-day mortality after cemented compared with cementless total hip arthroplasty (THA). However, previous studies are hampered by potential selection bias and suboptimal adjustment for comorbidity confounding. Therefore, we examined the comorbidity-adjusted mortality up to 90 days after cemented compared with cementless THA performed due to osteoarthritis.Patients and methods — Using the Nordic Arthroplasty Register Association database, 2005–2013, we included 108,572 cemented and 80,034 cementless THA due to osteoarthritis. We calculated the Charlson comorbidity index of each patient based on data from national patient registers. The Kaplan–Meier method was used to estimate unadjusted all-cause mortality. Cox regression was used to estimate hazard ratios (HR) with 95% confidence intervals (CI) for 14, 30-, and 90-day mortality comparing cemented with cementless THA, adjusting for age, sex, comorbidity, nation, and year of surgery.Results — Cumulative all-cause mortality within 90 days was 0.41% (CI 0.37–0.46) after cemented and 0.26% (CI 0.22–0.30) after cementless THA. The adjusted HR for cemented vs. cementless fixation was 0.97 (CI 0.79–1.2), and similar risk estimates were obtained for mortality within 14 (adjusted HR 0.91 [CI 0.64–1.3]) and 30 days (adjusted HR 0.94 [CI 0.71–1.3]). We found no clinically relevant differences in mortality between cemented and cementless THA in analyses stratified by age, sex, Charlson comorbidity index, or year of surgery.Interpretation — After adjustment for comorbidity as an important confounder, we observed similar early mortality between the 2 fixation techniques.

The question of whether cemented fixation of total hip arthroplasty (THA) increases early postoperative mortality, potentially by inducing bone cement implantation syndrome (BCIS) or thromboembolism, is fiercely debated (Olsen et al. 2014). The 90-day mortality after THA is reported to be 0.7% in a systematic review based on 32 observational studies including 1,129,330 patients (Berstock et al. 2014). The 3 most frequent causes of death within 90 days after THA are myocardial infarction, thromboembolism, and pneumonia (Pedersen et al. 2011). Since death is a rare complication after THA, only large register studies will have the statistical power to address the question of whether cemented THA fixation indeed confers an increased risk of early mortality.Analyses based on Norwegian, Finnish, or Swedish register data indicate similar 90-day mortality after cemented compared with cementless THA, but only a few studies were designed to adequately address comorbidity confounding using different methods (Garland et al. 2017, Dale et al. 2019, Ekman et al. 2019). The Norwegian study on 79,557 patients had access to ASA class, based on physicians’ preoperative assessment of overall health (Dale et al. 2019), whereas the Finnish study on 62,221 patients had information on comorbid conditions based on a hospital discharge register (Ekman et al. 2019). A Swedish study on 178,784 patients compared mortality after cemented and cementless THA adjusting for the Charlson comorbidity index (CCI), but the cohort exposed to cementless fixation was only about a 10th the size of the cohort exposed to cemented THA (Garland et al. 2017). That study is also hampered by selection bias since the practice in Sweden is to select younger and fitter patients for cementless fixation. The Nordic Arthroplasty Register Association (NARA) was established to fuse 4 well-established Nordic arthroplasty databases into a larger framework (Havelin et al. 2009). The choice of fixation techniques varies considerably among the participating countries, with a predominance of cemented fixation in Sweden and Norway and a much larger proportion of cementless fixation in Denmark and Finland (Mäkelä et al. 2014b). Thus, the motivation for performing our study was the possibility to cope with the selection bias by analysing patients from all Nordic countries together and to improve the adjustment for comorbidity confounding compared with previous studies. In addition, we examine whether age, sex, and calendar year are effect modifiers in the association between fixation and mortality, which was not examined in previous studies.We thus designed an international register-based cohort study aimed at comparing mortality within 0–14, 0–30, and 0–90 days after cemented and cementless THA performed due to osteoarthritis with adjustment for comorbidities at the time of surgery.      

Results of 3,668 primary total hip replacements for primary osteoarthritis in patients under the age of 55 years

Background and purpose In a previous study based on the Finnish Arthroplasty Register, the survival of cementless stems was better than that of cemented stems in younger patients. However, the survival of cementless cups was poor due to osteolysis. In the present study, we analyzed population-based survival rates of the cemented and cementless total hip replacements in patients under the age of 55 years with primary osteoarthritis in Finland.

Patients and methods 3,668 implants fulfilled our inclusion criteria. The previous data included years 1980–2001, whereas the current study includes years 1987–2006. The implants were classified in 3 groups: (1) implants with a cementless, straight, proximally circumferentially porous-coated stem and a porous-coated press-fit cup (cementless group 1); (2) implants with a cementless, anatomic, proximally circumferentially porous-coated stem, with or without hydroxyapatite, and a porous-coated press-fit cup with or without hydroxyapatite (cementless group 2); and (3) a cemented stem combined with a cemented all-polyethylene cup (the cemented group). Analyses were performed separately for 2 time periods: those operated 1987–1996 and those operated 1997–2006.

Results The 15-year survival for any reason of cementless total hip replacement (THR) group 1 operated on 1987–1996 (62%; 95% CI: 57–67) and cementless group 2 (58%; CI: 52–66) operated on during the same time period was worse than that of cemented THRs (71%; CI: 62–80), although the difference was not statistically significant. The revision risk for aseptic loosening of cementless stem group 1 operated on 1987–1996 (0.49; CI: 0.32–0.74) was lower than that for aseptic loosening of cemented stems (p = 0.001).

Interpretation Excessive wear of the polyethylene liner resulted in numerous revisions of modular cementless cups. The outcomes of total hip arthroplasty appear to have been relatively unsatisfactory for younger patients in Finland.     

Results of 3,668 primary total hip replacements for primary osteoarthritis in patients under the age of 55 years

Background and purpose

In a previous study based on the Finnish Arthroplasty Register, the survival of cementless stems was better than that of cemented stems in younger patients. However, the survival of cementless cups was poor due to osteolysis. In the present study, we analyzed population-based survival rates of the cemented and cementless total hip replacements in patients under the age of 55 years with primary osteoarthritis in Finland.

Patients and methods

3,668 implants fulfilled our inclusion criteria. The previous data included years 1980–2001, whereas the current study includes years 1987–2006. The implants were classified in 3 groups: (1) implants with a cementless, straight, proximally circumferentially porous-coated stem and a porous-coated press-fit cup (cementless group 1); (2) implants with a cementless, anatomic, proximally circumferentially porous-coated stem, with or without hydroxyapatite, and a porous-coated press-fit cup with or without hydroxyapatite (cementless group 2); and (3) a cemented stem combined with a cemented all-polyethylene cup (the cemented group). Analyses were performed separately for 2 time periods: those operated 1987–1996 and those operated 1997–2006.

Results

The 15-year survival for any reason of cementless total hip replacement (THR) group 1 operated on 1987–1996 (62%; 95% CI: 57–67) and cementless group 2 (58%; CI: 52–66) operated on during the same time period was worse than that of cemented THRs (71%; CI: 62–80), although the difference was not statistically significant. The revision risk for aseptic loosening of cementless stem group 1 operated on 1987–1996 (0.49; CI: 0.32–0.74) was lower than that for aseptic loosening of cemented stems (p = 0.001).

Interpretation

Excessive wear of the polyethylene liner resulted in numerous revisions of modular cementless cups. The outcomes of total hip arthroplasty appear to have been relatively unsatisfactory for younger patients in Finland.Only a few register-based studies have yielded results of THA for primary osteoarthritis in younger patients at a population-based level (Havelin et al. 2000, Malchau et al. 2002, Eskelinen et al. 2005, 2006). In patients under the age of 55 years, data from population-based studies have suggested that the survival of cementless, proximally porous-coated stems can be as good as that of cemented stems (Havelin et al. 2000, Eskelinen et al. 2005). However, it has not been clear whether cementless cups perform as well as cemented cups in younger patients.On the basis of the Finnish Arthroplasty Register, we evaluated population-based data on the survival of primary total hip replacements performed for primary osteoarthritis in patients under the age of 55 years. The data including years 1980–2001 has been published earlier (Eskelinen et al. 2005), whereas the current study includes data from 1987 to 2006.     

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.     

Increasing risk of revision due to deep infection after hip arthroplasty: A study on 97,344 primary total hip replacements in the Norwegian Arthroplasty Register from 1987 to 2007

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.     

Bacterial contamination of the wound during primary total hip and knee replacement: Median 13 years of follow-up of 90 replacements

Background and purpose

Previous work has shown that despite preventive measures, intraoperative contamination of joint replacements is still common, although most of these patients seem to do well in follow-up of up to 5 years. We analyzed the prevalence and bacteriology of intraoperative contamination of primary joint replacement and assessed whether its presence is related to periprosthetic joint infection (PJI) on long-term follow-up.

Patients and methods

49 primary total hip replacements (THRs) and 41 total knee replacements (TKRs) performed between 1990 and 1991 were included in the study. 4 bacterial swabs were collected intraoperatively during each procedure. Patients were followed up for joint-related complications until March 2011.

Results

19 of 49 THRs and 22 of 41 TKRs had at least 1 positive culture. Coagulase-negative staphylococci and Staphylococcus aureus were the most common organisms, contaminating 28 and 9 operations respectively. Where information was available, bacteria from 27 of 29 contaminated operations were susceptible to the prophylactic antibiotic administered. 13% of samples gathered before 130 min of surgery were contaminated, as compared to 35% collected after that time. 2 infections were diagnosed, both in TKRs. 1 of them may have been related to intraoperative contamination.

Interpretation

Intraoperative contamination was common but few infections occurred, possibly due to the effect of prophylactic antibiotics. The rate of contamination was higher with longer duration of surgery. It appears that positive results from intraoperative swabs do not predict the occurrence of PJI.Periprosthetic joint infection (PJI) is a major complication of joint replacement. 1 year after primary total joint replacement, around 1% of patients have been revised due to deep infection; superficial surgical site infections (SSIs) are more common and occur in around 3% of cases (Jämsen et al. 2010, Dale et al. 2011). PJI is difficult to diagnose and treat and has a severe effect on quality of life (Whitehouse et al. 2002). The number of primary joint replacements will increase (Kurtz et al. 2007), so the incidence of PJI may also rise. Prevention is of key importance. Measures such as laminar air flow and prophylactic antibiotics are effective (Lidwell et al. 1987). Intraoperative contamination is, however, common—occurring in one-fifth to two-thirds of operations. However, the short-term prognosis of most of these patients appears to be good (Davis et al. 1999, Byrne et al. 2007). Intraoperative contamination is usually the cause of early infections, but it may also cause a substantial number of the infections arising more than 2 years after surgery (Phillips et al. 2006). To our knowledge, there have been no studies on intraoperative contamination with over 5 years of follow-up.We studied the prevalence and bacteriology of intraoperative contamination during primary joint replacement and assessed whether the presence of intraoperative contamination is related to PJI on long-term follow-up.     

Infection in total knee replacement: a retrospective review of 6489 total knee replacements.

Six thousand four hundred eighty-nine knee replacements were done in 6120 patients at the authors' institution between 1993 and 1999. Operations were done in a theater with vertical laminar flow and with the surgical team using body exhaust suits. Of these knee replacements, 116 knees became infected and 113 were available for followup. One hundred of the infections occurred in patients undergoing primary knee replacement, whereas the remaining infections occurred in patients undergoing revision knee replacement. Ninety-seven of these knees (86%) had deep periprosthetic infections and the remaining 16 knees had superficial wound infections. One third of the deep infections occurred within the first 3 months after surgery and the remaining 2/3 occurred after 3 months. The overall early deep infection rate for patients undergoing a primary knee replacement was 0.39%, whereas the rate for patients undergoing a revision knee replacement was 0.97%. A cohort of noninfected knee replacements from patients matched for gender, age, and month of surgery was used as a control group. Those comorbidities that were statistically significant in increasing the risk of infection were prior open surgical procedures, immunosuppressive therapy, poor nutrition, hypokalemia, diabetes mellitus, obesity, and a history of smoking. Patients undergoing revision procedures had a statistically higher risk of infection than did patients undergoing primary surgeries. If the surgery took longer than 2.5 hours, the risk of infection was increased significantly. There was no change in the infection rate when the perioperative antibiotic prophylaxis was decreased from 48 to 24 hours after surgery. The predominant infectious organisms were gram-positive (Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus Group B). Twenty percent of the knees that were infected clinically had no organisms that could be identified. In each case, the patient had been treated empirically at another institution with antibiotics before a culture of the joint was obtained.