The risk of revision after primary total hip arthroplasty among statin users: a nationwide population-based nested case-control study

Statin use in total joint arthroplasty: a systematic review

Introduction

There has been increased interest in the use of Statins in total hip and knee arthroplasty (THA and TKA) patients to improve outcomes and reduce postoperative complications. This study was performed to systematically review the evidence on Statin use in total joint arthroplasty, specifically its benefits and complications.

Methods

Adhering to the PRISMA guidelines, a systematic review of PubMed, Embase, Scopus, Web of Science, and the Cochrane database was performed to find studies reporting on the effects of Statin use on outcomes of THA and TKA. Two authors independently selected relevant papers to include.

Results

A total of 18 papers were included in the final analysis. Most were retrospective studies, with heterogeneous patient selection and outcome measures. The evidence on the risks and benefits of Statin use on outcomes of total joint arthroplasty was very limited and heterogeneous. Studies were focusing on perioperative cardiac outcomes, clinical outcomes and complications, renal, pulmonary, and gastrointestinal outcomes. Due to the heterogeneity of reported data, a formal meta-analysis was not possible.

Conclusions

There is some evidence in the literature suggesting that perioperative use of Statins, especially in Statin-naïve patients, may reduce cardiac (e.g. atrial fibrillation) and noncardiac (e.g. delirium) complications, while not increasing the risk of muscle or liver toxicity. The authors also found low levels of evidence that Statin use may reduce the long-term risk for revision surgery and osteolysis.

Preoperative Statin Exposure Reduces Periprosthetic Fractures and Revisions following Total Knee Arthroplasty

The purpose of this study is to examine patients undergoing primary total knee arthroplasty (TKA) with and without prior history of statin use. We specifically evaluated (1) 90-day to 2-year periprosthetic fractures, (2) revisions, and (3) respective risk factors. We queried a national, all-payer database for patients undergoing primary TKA between 2010 and 2020. Chronic statin exposure was then identified and defined as more than three prescriptions filled within 1 year prior to TKA (statin users). A control cohort of patients undergoing TKA without the prior history of statin use was then created (statin naïve). Cohorts were matched 1:1 based on age range, Charlson Comorbidity Index, sex, diabetes, obesity, and tobacco use, yielding 579,136 patients. Multivariate logistic regression was performed to evaluate the risk factors for periprosthetic fractures and revisions, adjusted for demographics and comorbidities. Statin users had a lower incidence of periprosthetic fractures from 90 days to 2 years compared with the statin naïve (p < 0.001). Similarly, statin users had a lower incidence of revisions at 90 days to 2 years (p < 0.001). Using the statin-naïve cohort as a reference, statin use was independently associated with decreased odds of periprosthetic fractures and revisions. Statin use was associated with a reduced risk of periprosthetic fractures and revisions. These results may mitigate postoperative risks though statin therapy is currently not recommended for fracture-related benefits alone.

Stroke Risk in Patients with Gout: A Nationwide Retrospective Cohort Study in Taiwan

Objectives: To estimate stroke risk in Taiwanese patients with gout. Methods: We enrolled patients from the Taiwan National Health Insurance Database, with gout diagnosed from 2000 to 2008, and followed them up until December 2018. This cohort was propensity score-matched according to birth year, sex, the date of diagnosis of gout, comorbidities, and co-medications with individuals without gout (controls) (n = 310,820 in each group). Stroke was defined as the primary diagnosis at discharge after the index date. To evaluate ischemic and hemorrhagic stroke risks, we calculated their incidence, hazard ratio (HR), and two-year moving average incidence rate. Results: The incidence (95% CI) and HR of ischemic stroke were lower in the gout group than in the control group in the first 3 years (incidence: 4.74 [4.60–4.88] vs. 5.17 [5.03–5.32] per 1000 person-years; HR: 0.92 [0.88–0.96]), then became significantly higher than in the control group after 3 years (incidence: 4.10 [4.04–4.16] vs. 3.81 [3.75–3.87] per 1000 person-years; HR: 1.08 [1.05–1.10]). Similarly, the incidence (95% CI) and HR of hemorrhagic stroke was lower in the gout group than in the control group in the first 3 years (incidence: 1.51 [1.43–1.59] vs. 1.70 [1.62–1.79] per 1000 person-years; HR: 0.88 [0.82–0.92]), then became significantly higher than in controls after 3 years (incidence: 1.43 [1.39–1.46] vs. 1.26 [1.22–1.29] per 1000 person-years; HR: 1.14 [1.10–1.18]). Conclusions: In Taiwan, patients with gout had higher risks of ischemic and hemorrhagic stroke after 3 years.

UK poSt Arthroplasty Follow-up rEcommendations (UK SAFE): what does analysis of linked, routinely collected national datasets tell us about mid-late term revision risk after knee replacement?

OBJECTIVE

To identify patients at risk of mid-late term revision of knee replacement (KR) to inform targeted follow-up.

DESIGN

Analysis of linked national datasets from primary and secondary care (Clinical Practice Research Datalink (CPRD GOLD), National Joint Registry (NJR), English Hospital Episode Statistics (HES) and Patient Reported Outcome Measures (PROMs)).

PARTICIPANTS

Primary elective KRs aged ≥18 years.

EVENT OF INTEREST

Revision surgery ≥5 years (mid-late term) postprimary KR.

STATISTICAL METHODS

Cox regression modelling to ascertain risk factors of mid-late term revision. HRs and 95% CIs assessed association of sociodemographic factors, comorbidities, medication, surgical variables and PROMs with mid-late term revision.

RESULTS

NJR-HES-PROMs data were available from 2008 to 2011 on 188 509 KR. CPRD GOLD-HES data covered 1995-2011 on 17 378 KR. Patients had minimum 5 years postprimary surgery to end 2016. Age and gender distribution were similar across datasets; mean age 70 years, 57% female. In NJR, there were 8607 (4.6%) revisions, median time-to-revision postprimary surgery 1.8 years (range 0-8.8), with 1055 (0.6%) mid-late term revisions; in CPRD GOLD, 877 (5.1%) revisions, median time-to-revision 4.2 years (range 0.02-18.3), with 352 (2.0%) mid-late term revisions.Reduced risk of revision after 5 years was associated with older age (HR: 0.95; 95% CI 0.95 to 0.96), obesity (0.70; 0.56 to 0.88), living in deprived areas (0.71; 0.58 to 0.87), non-white ethnicity (0.58; 0.43 to 0.78), better preoperative pain and functional limitation (0.42; 0.33 to 0.53), better 6-month postoperative pain and function (0.33; 0.26 to 0.41) or moderate anxiety/depression (0.73; 0.63 to 0.83) at primary surgery.Increased risk was associated with male gender (1.32; 1.04 to 1.67); when anticonvulsants (gabapentin and pregabalin) (1.58; 1.01 to 2.47) or opioids (1.36; 1.08 to 1.71) were required prior to primary surgery.No implant factors were identified.

CONCLUSION

The risk of mid-late term KR revision is very low. Increased risk of revision is associated with patient case-mix factors, and there is evidence of sociodemographic inequality.

UK poSt Arthroplasty Follow-up rEcommendations (UK SAFE): what does analysis of linked, routinely collected national data sets tell us about mid-late term revision risk after hip replacement? Retrospective cohort study

OBJECTIVE

To identify patients at risk of mid-late term revision of hip replacement to inform targeted follow-up.

DESIGN

Analysis of linked national data sets from primary and secondary care (Clinical Practice Research Datalink (CPRD-GOLD); National Joint Registry (NJR); English Hospital Episode Statistics (HES); Patient-Reported Outcome Measures (PROMs)).

PARTICIPANTS

Primary elective total hip replacement (THR) aged≥18.

EVENT OF INTEREST

Revision surgery≥5 years (mid-late term) after primary THR.

STATISTICAL METHODS

Cox regression modelling to ascertain risk factors of mid-late term revision. HR and 95% CI assessed association of sociodemographic factors, comorbidities, medication, surgical variables and PROMs with mid-late term revision.

RESULTS

NJR-HES-PROMs data were available from 2008 to 2011 on 142 275 THR; mean age 70.0 years and 61.9% female. CPRD GOLD-HES data covered 1995-2011 on 17 047 THR; mean age 68.4 years, 61.8% female. Patients had minimum 5 years postprimary surgery to end 2016. In NJR-HES-PROMS data, there were 3582 (2.5%) revisions, median time-to-revision after primary surgery 1.9 years (range 0.01-8.7), with 598 (0.4%) mid-late term revisions; in CPRD GOLD, 982 (5.8%) revisions, median time-to-revision 5.3 years (range 0-20), with 520 (3.1%) mid-late term revisions.Reduced risk of mid-late term revision was associated with older age at primary surgery (HR: 0.96; 95% CI: 0.95 to 0.96); better 6-month postoperative pain/function scores (HR: 0.35; 95% CI: 0.27 to 0.46); use of ceramic-on-ceramic (HR: 0.73; 95% CI: 0.56 to 0.95) or ceramic-on-polyethylene (HR: 0.76; 95% CI: 0.58 to 1.00) bearing surfaces.Increased risk of mid-late term revision was associated with the use of antidepressants (HR: 1.32; 95% CI: 1.09 to 1.59), glucocorticoid injections (HR: 1.33; 95% CI: 1.06 to 1.67) and femoral head size≥44 mm (HR: 2.56; 95% CI: 1.09 to 6.02)No association of gender, obesity or Index of Multiple Deprivation was observed.

CONCLUSION

The risk of mid-late term THR is associated with age at primary surgery, 6-month postoperative pain and function and implant factors. Further work is needed to explore the associations with prescription medications observed in our data.

Statin Exposure and Risk of Prosthetic Joint Infection After Total Knee or Hip Arthroplasty Among U.S. Veterans

BACKGROUND

Statins have a variety of pleiotropic effects that could be beneficial for patients undertaking total knee or hip arthroplasty. In vitro and in vivo models suggest the beneficial effects of statins through bone formation and modulating proinflammatory cytokines triggered by implant debris. However, statins also exhibit antimicrobial action and may reduce the risk of revision surgery via reducing the risk of infection. We sought to explore the relationship between statin use and prosthetic joint infection (PJI) after total knee or hip arthroplasty.

METHODS

We use a retrospective cohort of patients undergoing total knee or hip arthroplasty performed within the Department of Veterans Affairs. To minimize selection bias between the statin exposed and unexposed patients, we used 1:1 ratio propensity score matching. We fit adjusted Cox proportional hazards models to quantify the risk of PJI between the cohorts within 1 year, 3 years, and all follow-up time.

RESULTS

With a study period beginning from January 2000, a total of 60,241 patients were included. The unmatched Cox models reveal, over the entire follow-up time, a statistically significant lower risk of infection for the statin exposed patients (hazard ratio = 0.869; 95% confidence interval = [0.79-0.956]). The matched Cox model results reveal a statistically significant lower risk of PJI, only in the overall model, for the statin exposed cohort compared with the unexposed cohort (hazard ratio = 0.895, 95% confidence interval = [0.807-0.993]).

CONCLUSION

Our analysis finds some support for the beneficial effects of statins for preventing PJI among patients undergoing total knee or hip arthroplasty.

Long-term survival after cemented versus uncemented total hip arthroplasty for treatment of acute femoral neck fracture: a retrospective study with a mean 10-year follow-up

Objective

To compare the long-term survivorship and Harris hip scores (HHSs) between cemented total hip arthroplasty (CTHA) and uncemented total hip arthroplasty (UTHA) for treatment of acute femoral neck fractures (FNFs).

Methods

Data of 224 hips (CTHA, n = 112; UTHA, n = 112) that underwent primary surgery in our medical institution from 2005 to 2017 were retrospectively analysed. The primary endpoint was the risk of all-cause revision. The difference in the risk of all-cause revision between the two groups was assessed by Kaplan–Meier survival analysis with a log-rank test and Cox regression analysis.

Results

The mean postoperative follow-up was 10 years (range, 3–13 years). The Kaplan–Meier estimated 10-year implant survival rate was significantly higher in the CTHA than UTHA group (98.1% vs. 96.2%, respectively). The adjusted Cox regression analysis demonstrated a significantly lower risk of revision in the CTHA than UTHA group. At the final follow-up, the mean HHS was significantly higher in the CTHA than UTHA group (85.10 vs. 79.11, respectively).

Conclusion

This retrospective analysis demonstrated that CTHA provided higher survival, lower revision risk, and higher functional outcome scores than UTHA. Further follow-up is necessary to verify whether these advantages of CTHA persist over time.

Statins, bone biology and revision arthroplasty: review of clinical and experimental evidence

Osteoarthritis is a painful, disabling condition which is increasing in prevalence as a result of an ageing population. With no recognized disease-limiting therapeutics, arthroplasty of the hip and knee is the most common and effective treatment for lower limb osteoarthritis, however lower limb arthroplasty has a finite life-span and a proportion of patients will require revision arthroplasty. With increasing life expectancy and an increasing proportion of younger (<65 years) patients undergoing arthroplasty, the demand for revision arthroplasty after implant failure is also set to increase.

Statins are cholesterol-modulating drugs widely used for cardiovascular risk reduction which have been noted to have pleiotropic effects including potentially influencing arthroplasty survival. In vitro studies have demonstrated pleiotropic effects in human bone cells, including enhancement of osteoblastogenesis following simvastatin exposure, and in vivo studies have demonstrated that intraperitoneal simvastatin can increase peri-implant bone growth in rats following titanium tibial implant insertion. There is evidence that statins may also influence osseointegration, enhancing bone growth at the bone–implant interface, subsequently improving the functional survival of implants. Data from the Danish Hip Arthroplasty Registry and the Clinical Practice Research Datalink in the UK suggest a reduction in the risk of lower limb revision arthroplasty in statin ever-users versus never-users, and a time-dependent effect of statins in reducing the risk of revision. In this article we review the clinical and experimental evidence linking statins and risk of revision arthroplasty.

The Effects of Biomaterial Implant Wear Debris on Osteoblasts

Aseptic loosening subsequent to periprosthetic osteolysis is the leading cause for the revision of arthroplasty failure. The biological response of macrophages to wear debris has been well established, however, the equilibrium of bone remodeling is not only dictated by osteoclastic bone resorption but also by osteoblast-mediated bone formation. Increasing evidence shows that wear debris significantly impair osteoblastic physiology and subsequent bone formation. In the present review, we update the current state of knowledge regarding the effect of biomaterial implant wear debris on osteoblasts. The interaction of osteoblasts with osteoclasts and macrophages under wear debris challenge, and potential treatment options targeting osteoblasts are also presented.

The what, when and how of orthopaedic registers: an introduction into register-based research

Establishment of orthopaedic registers started in 1975 and many registers have been initiated since. The main purpose of registers is to collect information on patients, implants and procedures in order to monitor and improve the outcome of the specific procedure.

Data validity reflects the quality of the registered data and consists of four major aspects: coverage of the register, registration completeness of procedures/patients, registration completeness of variables included in the register and accuracy of registered variables.

Survival analysis is often used in register studies to estimate the incidence of an outcome. The most commonly used survival analysis is the Kaplan–Meier survival curves, which present the proportion of patients who have not experienced the defined event (e.g. death or revision of a prosthesis) in relation to the time. Depending on the research question, competing events can be taken into account by using the cumulative incidence function. Cox regression analysis is used to compare survival data for different groups taking differences between groups into account.

When interpreting the results from observational register-based studies a number of factors including selection bias, information bias, chance and confounding have to be taken into account. In observational register-based studies selection bias is related to, for example, absence of complete follow-up of the patients, whereas information bias is related to, for example, misclassification of exposure (e.g. risk factor of interest) or/and outcome.

The REporting of studies Conducted using Observational Routinely-collected Data guidelines should be used for studies based on routinely-collected health data including orthopaedic registers.

Linkage between orthopaedic registers, other clinical quality databases and administrative health registers may be of value when performing orthopaedic register-based research.

Cite this article: EFORT Open Rev 2019;4 DOI: 10.1302/2058-5241.4.180097

Effect of Timing and Duration of Statin Exposure on Risk of Hip or Knee Revision Arthroplasty: A Population-based Cohort Study

OBJECTIVES

To determine whether the timing and duration of statin exposure following total hip/knee arthroplasty (THA/TKA) influence the risk of revision arthroplasty.

METHODS

Subjects from the Clinical Practice Research Datalink, a large population-based clinical database, who had THA/TKA from 1988 to 2016, were included. Propensity score adjusted Cox regression models were used to determine the association between statin exposure and the risk of revision THA/TKA, (1) at any time, and (2) if first exposed 0-1, 1-5, or > 5 years following THA/TKA. We also investigated the effect of duration of statin exposure (< 1, 1-2, 2-3, 3-4, 4-5, > 5 yrs).

RESULTS

The study included 151,305 participants. There were 65,032 (43%) exposed to statins during followup and 3500 (2.3%) had revision arthroplasty. In a propensity score adjusted model, exposure to statins was associated with a reduced risk of revision arthroplasty (HR 0.82, 95% CI 0.75-0.90). Participants first exposed within 1 year and between 1 and 5 years following THA/TKA (vs unexposed) had a reduced risk of revision arthroplasty (HR 0.82, 95% CI 0.74-0.91 and HR 0.76, 95% CI 0.65-0.90, respectively). In relation to duration of statin therapy, participants exposed for more than 5 years in total (vs < 1 yr) had a reduced risk of revision (HR 0.74, 95% CI 0.62-0.88).

CONCLUSION

Statin therapy initiated up to 5 years following THA/TKA may reduce the risk of revision arthroplasty.

Total knee arthroplasty: improving outcomes with a multidisciplinary approach

Total knee arthroplasty (TKA) is the most commonly performed inpatient surgical procedure within the USA and is estimated to reach 3.48 million procedures annually by 2030. As value-based care initiatives continue to focus on hospital readmission rates and patient satisfaction, it has become essential for health care providers to develop and implement a multidisciplinary approach to enhance TKA outcomes while minimizing unnecessary expenditures. Through this necessity, clinical care pathways have been developed to standardize, organize, and improve the quality and efficiency of patient care while simultaneously encouraging the collaboration among various medical care providers. Here, we review several systems based programs and specialty care practices that can be adopted into the standard orthopedic practice.

Comparison of general versus isolated regional anesthesia in total shoulder arthroplasty: A retrospective propensity-matched cohort analysis

BACKGROUND

Intraoperative anesthetic typically consists of either general anesthesia (GA) or isolated regional anesthesia (RA).

METHODS

A retrospective propensity-matched cohort analysis on patients undergoing TSA was performed to determine differences between GA and RA in regard to patient population, complications, LOS and hospital readmission.

RESULTS

4158 patients underwent TSA with GA or isolated RA. Propensity-matching resulted in 912 patients in each cohort. RA had lower overall in-hospital complications and greater homebound discharge disposition with lower 90-day readmission rates than GA.

CONCLUSION

After TSA, isolated RA was associated with lower in-hospital complications, readmission rates and odds of hospital readmission than GA.

The effect of simvastatin on periprosthetic bone mineral density in the hypercholesterolaemic patients after total hip arthroplasty

OBJECTIVE

The purpose of this study was to investigate the effect of simvastatin on periprosthetic bone mineral density (BMD) in hypercholesterolaemic patients after total hip arthroplasty.

METHODS

From January 2012 to December 2015, a total of 42 consecutive hypercholesterolaemic patients with total hip arthroplasty were recruited for this study. The simvastatin group was 21 patients (15 males, 6 females) with average age of 69.4 ± 6.6 years treated with simvastatin for one year post-operatively, and the control group was the other 21 patients (12 males, 9 females) who did not take simvastatin. These parameters of the periprosthetic bone mineral density after total hip arthroplasty were collected by dual energy X-ray absorptiometry(DEXA) one week and three, six, 12 months post-operatively.

RESULTS

In the control group patients showed significant loss of periprosthetic BMD in ROIs 1, 2, 6, and 7 throughout the study period. The loss of BMD in ROIs 3 and 5 was only significantly observed at three months follow-up and recovered thereafter. There were no significant detected changes of BMD in ROI 4. In the Simvastatin group, the percentage of BMD loss was significantly less (P < 0.05) in ROI 1, 2, 6 and 7 throughout the study period than the control group. The percentage of BMD loss were significant observed in ROI 3 and 5 at three months follow-up, which were also significantly less (P < 0.05) than in the control group. A slight gain of BMD was measured in ROI 4 at 12 months follow-up (1.419%, P < 0.05).

CONCLUSION

Simvastatin administered for one year post-operatively can effectively prevent periprosthetic bone loss after total hip arthroplasty.

Clinical Factors, Disease Parameters, and Molecular Therapies Affecting Osseointegration of Orthopedic Implants

Total hip and knee arthroplasty are effective interventions for management of end-stage arthritis. Indeed, about 7 million Americans are currently living with artificial hip and knee joints. The majority of these individuals, however, will outlive their implants and require revision surgeries, mostly due to poor implant osseointegration and aseptic loosening. Revisions are potentially avoidable with better management of patient-related risk factors that affect the osseointegration of orthopedic implants. In this review, we summarize the published clinical literature on the role of demographics, biologic factors, comorbidities, medications and aseptic loosening risk. We focus on several systemic and local factors that are particularly relevant to implant osseointegration. Examples include physiological and molecular processes that are linked to hyperglycemia, oxidative stress, metabolic syndrome and dyslipidemia. We discuss how orthopedic implant osseointegration can be affected by a number of molecular therapies that are antiresorptive or bone anabolic (i.e. calcium, vitamin D, bisphosphonates, calcitonin, strontium, hormone replacement therapy, selective estrogen-receptor modulators).

Statins and Risk of Lower Limb Revision Surgery: The Influence of Differences in Study Design Using Electronic Health Records From the United Kingdom and Denmark

Previous observational studies on statins have shown variable results based on the methodology used. Our objective was to study the association between statins and orthopedic implant failure and to explore the influence of methodological differences in study design. Our study base consisted of patients with a primary total joint replacement in Denmark and the United Kingdom (n = 189,286; 1987–2012). We used 4 study designs: 1) case-control (each patient with revision surgery matched to 4 controls), 2) time-dependent cohort (postoperative statin use as a time-varying exposure variable), 3) immortal time cohort (misclassifying the time postoperatively before statin use), and 4) time-exclusion cohort (excluding the time postoperatively before statin use). Cox proportional hazards models and logistic regression were used to estimate incidence rate ratios. In the time-dependent cohort design, statin use was associated with a decreased risk of revision surgery (adjusted incidence rate ratio (IRR) = 0.90, 95% confidence interval (CI): 0.85, 0.96), which was similar to our case-control results (IRR = 0.87, 95% CI: 0.81, 0.93). In contrast, both time-fixed cohort designs yielded substantially lower risk estimates (IRR = 0.36 (95% CI: 0.34, 0.38) and IRR = 0.65 (95% CI: 0.63, 0.68), respectively). We discourage the use of time-fixed cohort studies, which may falsely suggest protective effects. The simple choice of how to classify exposure can substantially change results from biologically plausible to implausible.

On the use and misuse of scalar scores of confounders in design and analysis of observational studies

We assess the asymptotic bias of estimates of exposure effects conditional on covariates when summary scores of confounders, instead of the confounders themselves, are used to analyze observational data. First, we study regression models for cohort data that are adjusted for summary scores. Second, we derive the asymptotic bias for case-control studies when cases and controls are matched on a summary score, and then analyzed either using conditional logistic regression or by unconditional logistic regression adjusted for the summary score. Two scores, the propensity score (PS) and the disease risk score (DRS) are studied in detail. For cohort analysis, when regression models are adjusted for the PS, the estimated conditional treatment effect is unbiased only for linear models, or at the null for non-linear models. Adjustment of cohort data for DRS yields unbiased estimates only for linear regression; all other estimates of exposure effects are biased. Matching cases and controls on DRS and analyzing them using conditional logistic regression yields unbiased estimates of exposure effect, whereas adjusting for the DRS in unconditional logistic regression yields biased estimates, even under the null hypothesis of no association. Matching cases and controls on the PS yield unbiased estimates only under the null for both conditional and unconditional logistic regression, adjusted for the PS. We study the bias for various confounding scenarios and compare our asymptotic results with those from simulations with limited sample sizes. To create realistic correlations among multiple confounders, we also based simulations on a real dataset.

Comorbid diseases as predictors of survival of primary total hip and knee replacements: a nationwide register-based study of 96 754 operations on patients with primary osteoarthritis

OBJECTIVES

To examine how comorbid diseases (cardiovascular diseases, hypertension, diabetes, cancer, pulmonary diseases, depression, psychotic disorders and neurodegenerative diseases) affect survival of hip and knee replacements.

METHODS

Data for this register-based study were collected by combining data from five nationwide health registers. 43 747 primary total hip and 53 007 primary total knee replacements performed for osteoarthritis were included. The independent effects of comorbid diseases on prosthesis survival were analysed using multivariate Cox regression analysis.

RESULTS

Occurrence of one or more of the diseases analysed was associated with poorer survival of hip (HR for revision 1.16, 95% CI 1.08 to 1.23) and knee replacements (1.23, 1.16 to 1.30). Cardiovascular diseases and psychotic disorders were associated with increased risk of revision after both hip (1.19, 1.06 to 1.34 and 1.41, 1.04 to 1.91, respectively) and knee replacement (1.29, 1.14 to 1.45 and 1.41, 1.07 to 1.86, respectively). Hypertension and diabetes were associated with early revision (0-5 years after primary operation) after knee replacements (1.14, 1.01 to 1.29 and 1.27, 1.08 to 1.50, respectively). Cancer was associated with poorer survival of hip replacements (1.27, 1.05 to 1.54) and late revision (>5 years) of knee replacements (2.21, 1.31 to 3.74). Depression affected the risk of early revision after hip replacement (1.50, 1.02 to 2.21). Neurodegenerative and pulmonary diseases did not affect prosthesis survival.

CONCLUSIONS

Comorbid diseases may play an important role in predicting survival of primary hip and knee replacements. The mechanisms underlying these findings and their effect on cost-effectiveness of joint replacements, merit further research.

Osteolysis around total knee arthroplasty: a review of pathogenetic mechanisms

Aseptic loosening and other wear-related complications are some of the most frequent late reasons for revision of total knee arthroplasty (TKA). Periprosthetic osteolysis (PPOL) pre-dates aseptic loosening in many cases, indicating the clinical significance of this pathogenic mechanism. A variety of implant-, surgery- and host-related factors have been delineated to explain the development of PPOL. These factors influence the development of PPOL because of changes in mechanical stresses within the vicinity of the prosthetic device, excessive wear of the polyethylene liner, and joint fluid pressure and flow acting on the peri-implant bone. The process of aseptic loosening is initially governed by factors such as implant/limb alignment, device fixation quality and muscle coordination/strength. Later, large numbers of wear particles detached from TKA trigger and perpetuate particle disease, as highlighted by progressive growth of inflammatory/granulomatous tissue around the joint cavity. An increased accumulation of osteoclasts at the bone-implant interface, impairment of osteoblast function, mechanical stresses and increased production of joint fluid contribute to bone resorption and subsequent loosening of the implant. In addition, hypersensitivity and adverse reactions to metal debris may contribute to aseptic TKA failure, but should be determined more precisely. Patient activity level appears to be the most important factor when the long-term development of PPOL is considered. Surgical technique, implant design and material factors are the most important preventative factors, because they influence both the generation of wear debris and excessive mechanical stresses. New generations of bearing surfaces and designs for TKA should carefully address these important issues in extensive preclinical studies. Currently, there is little evidence that PPOL can be prevented by pharmacological intervention.

Statins may reduce femoral osteolysis in patients with total Hip arthroplasty

In experimental studies, statin use has been associated with reduction of osteoclastic activity and promotion of bone formation around implants. Moreover, a large clinical study recently reported a substantially reduced risk of revision for aseptic loosening among statin users with THA. Our objective was to evaluate the influence of statin use on the development of femoral osteolysis within 5 years after THA. We conducted a case-cohort study including all THAs presenting with femoral osteolysis at the 5 year visit (cases) and compared them with those without osteolysis (controls). Cases and controls were identified from a cohort of primary THAs operated between 2001 and 2005. Seven hundred thirty-five THAs were included, mean age 68 years. Five years after surgery osteolysis had developed around the femoral component of 40 THAs (5.4%). Ever-use of statins was much less frequent among cases (5 of 40, 12.5%) than among controls (199 of 695, 28.6%). The crude risk ratio of femoral osteolysis among statin users was 0.36 (95% CI 0.14; 0.92). After adjusting for age, sex, activity level, BMI, diagnosis, bearing surface, and type of stem, the adjusted risk ratio was 0.38 (95% CI 0.15; 0.99). In conclusion, statin use was associated with a reduced risk of developing femoral osteolysis 5 years after THA. Statins may be useful for reducing the risk of implant failure following THA.

Medial placement of the acetabular component in an alumina-on-alumina total hip arthroplasty: a comparative study with propensity score matching

PURPOSE

In an alumina-on-alumina total hip arthroplasty (THA), recommended with a small inclination angle <45°, the acetabular component (cup) may be positioned more medially to be covered almost completely by host bone. The purpose of this study was to identify the correlating factors and to evaluate the outcomes of medial placement of the cup in patients with alumina-on-alumina THAs.

METHODS

Using the propensity score matching with age, gender, body mass index, initial diagnosis, and the length of follow-up as variables, 38 hips with a medialized cup and 38 hips with a non-medialized one were identified from 389 hips in 347 who patients underwent primary alumina-on-alumina THA and followed up for more than 7 years. Clinical and radiological outcomes were compared between the two groups.

RESULTS

Preoperative acetabular medial wall thickness and the cup inclination angle were significantly smaller in the medialization group compared to the non-medialization group. Center edge angle, cup size, and coverage by host bone were not significantly different between the two groups. The hip center of rotation was significantly medialized in the medialization group. The Harris hip scores were not significantly different between the two groups. No component loosening or osteolysis was observed and no revision was required in either groups.

CONCLUSIONS

Thin acetabular medial wall and a small inclination angle of the cup were the correlating factors of medial placement of the cup in patients who underwent an alumina-on-alumina THA. Medial placement did not lead to differences in the clinical or radiological outcomes.

Simvastatin prevents the induction of interleukin-6 gene expression by titanium particles in human osteoblastic cells

One of the most important complications of total joint arthroplasty is failure associated with periprosthetic osteolysis, a process mainly initiated by the biological response to wear-derived products from the biomaterials in service. The inflammatory mediator interleukin-6 (IL-6) plays a key role in the establishment and progression of aseptic loosening. Metal particles specifically up-regulate IL-6 production in bone-forming cells and implant-bone interfacial tissues. The use of statins has been recently associated with a significantly reduced risk of revision in patients that undergo total hip arthroplasty. We hypothesized that simvastatin (Simv) could modulate the osteoblastic response to titanium particles (Ti) by attenuating the production of IL-6. Pre-treatment of human osteoblastic cells with Simv down-regulated Ti particle-induced IL-6 gene expression at mRNA and protein levels. The effect of Simv on Ti-induced IL-6 production in osteoblastic cells could not be explained by inhibition of the internalization of metal particles. The mechanism involved in this down-regulation is based in the inhibition of the HMG-CoA/GGPP/RhoA/ROCK pathway, independently of Simv effects in the cholesterol synthesis. The cytokine-lowering property of Simv has been observed in Saos-2 cells and human primary osteoblasts (hOBs) exposed to Ti particles, and was further enhanced when hOBs were co-cultured with macrophages.

Risk factors for revision of primary total hip arthroplasty: a systematic review

BACKGROUND

Numerous papers have been published examining risk factors for revision of primary total hip arthroplasty (THA), but there have been no comprehensive systematic literature reviews that summarize the most recent findings across a broad range of potential predictors.

METHODS

We performed a PubMed search for papers published between January, 2000 and November, 2010 that provided data on risk factors for revision of primary THA. We collected data on revision for any reason, as well as on revision for aseptic loosening, infection, or dislocation. For each risk factor that was examined in at least three papers, we summarize the number and direction of statistically significant associations reported.

RESULTS

Eighty-six papers were included in our review. Factors found to be associated with revision included younger age, greater comorbidity, a diagnosis of avascular necrosis (AVN) as compared to osteoarthritis (OA), low surgeon volume, and larger femoral head size. Male sex was associated with revision due to aseptic loosening and infection. Longer operating time was associated with revision due to infection. Smaller femoral head size was associated with revision due to dislocation.

CONCLUSIONS

This systematic review of literature published between 2000 and 2010 identified a range of demographic, clinical, surgical, implant, and provider variables associated with the risk of revision following primary THA. These findings can inform discussions between surgeons and patients relating to the risks and benefits of undergoing total hip arthroplasty.

Influence of statins locally applied from orthopedic implants on osseous integration

Background

Simvastatin increases the expression of bone morphogenetic protein 2 (BMP-2) in osteoblasts, therefore it is important to investigate the influence of statins on bone formation, fracture healing and implant integration. The aim of the present study was to investigate the effect of Simvastatin, locally applied from intramedullary coated and bioactive implants, on bone integration using biomechanical and histomorphometrical analyses.

Methods

Eighty rats received retrograde nailing of the femur with titanium implants: uncoated vs. polymer-only (poly(D,L-lactide)) vs. polymer plus drug coated (either Simvastatin low- or high dosed; “SIM low/ high”). Femurs were harvested after 56 days for radiographic and histomorphometric or biomechanical analysis (push-out).

Results

Radiographic analysis revealed no pathological findings for animals of the control and SIM low dose group. However, n=2/10 animals of the SIM high group showed osteolysis next to the implant without evidence of bacterial infection determined by microbiological analysis. Biomechanical results showed a significant decrease in fixation strength for SIM high coated implants vs. the control groups (uncoated and PDLLA). Histomorphometry revealed a significantly reduced total as well as direct bone/implant contact for SIM high- implants vs. controls (uncoated and PDLLA-groups). Total contact was reduced for SIM low vs. uncoated controls. Significantly reduced new bone formation was measured around SIM high coated implants vs. both control groups.

Conclusions

This animal study suggests impaired implant integration with local application of Simvastatin from intramedullary titanium implants after 8 weeks when compared to uncoated or carrier-only coated controls.

Peptic ulcer disease and heart disease are associated with periprosthetic fractures after total hip replacement

BACKGROUND AND PURPOSE

There have been no published studies assessing the possible association of medical comorbidities with periprosthetic fracture risk. We therefore assessed whether medical comorbidity is associated with risk of periprosthetic fractures after total hip replacement (THR).

MATERIAL AND METHODS

We used prospectively collected data from 1989-2008 in the Mayo Clinic Total Joint Registry for 2 cohorts: primary THR and revision THR. The main variables of interest were Deyo-Charlson comorbidities at the time of surgery. Outcome of interest was p ostoperative periprosthetic fracture at postoperative day 1 onwards. Multivariable Cox regression models were additionally adjusted for age, sex, body mass index, American Society of Anesthesiology (ASA) class, and operative diagnosis.

RESULTS

We identified 14,065 primary THRs and 6,281 revision THRs with mean follow-up times of 6.3 and 5.6 years, respectively. There were 305 postoperative periprosthetic fractures in the primary THR cohort and 330 in the revision THR cohort. In patients who underwent primary THR, 2 comorbidities were associated with higher risk of periprosthetic fracture: peptic ulcer disease with adjusted hazard ratio of 1.5 (95% CI: 1.1-2.2) and heart disease with adjusted hazard ratio of 1.7 (CI: 1.2-2.4). In patients with revision THR, peptic ulcer disease was associated with a higher adjusted risk of periprosthetic fracture, 1.6 (CI: 1.1-2.3).

INTERPRETATION

Peptic ulcer disease and heart disease in primary THR patients and peptic ulcer disease in revision THR patients were associated with higher postoperative periprosthetic fracture risk. Further studies are needed to understand whether disease severity or specific medications used for treatment, or both, are responsible for this association. This may allow identification of modifiable factors.

Patient-related risk factors for postoperative mortality and periprosthetic joint infection in medicare patients undergoing TKA

BACKGROUND

The impact of specific baseline comorbid conditions on the relative risk of postoperative mortality and periprosthetic joint infection (PJI) in elderly patients undergoing TKA has not been well defined.

QUESTIONS/PURPOSES

We calculated the relative risk of postoperative mortality and PJI associated with 29 comorbid conditions in Medicare patients undergoing TKA.

PATIENTS AND METHODS

The Medicare 5% sample was used to calculate the relative risk of 90-day postoperative mortality and PJI as a function of 29 preexisting comorbid conditions in 83,011 patients who underwent primary TKA between 1998 and 2007.

RESULTS

The independent risk factors for 90-day postoperative mortality (in decreasing order of significance) were congestive heart failure, metastatic cancer, renal disease, peripheral vascular disease, cerebrovascular disease, lymphoma, cardiac arrhythmia, dementia, pulmonary circulation disorders, and chronic liver disease. The independent risk factors for PJI (in decreasing order of significance) were congestive heart failure, chronic pulmonary disease, preoperative anemia, diabetes, depression, renal disease, pulmonary circulation disorders, obesity, rheumatologic disease, psychoses, metastatic tumor, peripheral vascular disease, and valvular disease.

CONCLUSIONS

We believe this information important when counseling elderly patients regarding the risks of mortality and PJI after TKA and risk-adjusting publicly reported TKA patient outcomes.

Organisation, data evaluation, interpretation and effect of arthroplasty register data on the outcome in terms of revision rate in total hip arthroplasty

Originally developed in Scandinavia, national arthroplasty registers have spread worldwide during the last decade. The value of registers for quality improvement in arthroplasty has frequently been documented. However, for the development of a successful register a few key points should be taken into account. Uncontrolled loss of patients from the registry area should be avoided. Registers should form an integral part of a country's medical system. To realise the potential for improvement, it is crucial that physicians deal with the results in detail. Thus it is absolutely essential to involve the specialty societies in the interpretation and dissemination of results. With respect to revision rates, register data are usually more valid than meta-analyses of clinical studies. For every physician the most valuable data are those coming from a register in his own country; the development of national arthroplasty registers should therefore be continued.