Autoimmune comorbidity in type 1 diabetes and its association with metabolic control and mortality risk in young people: a population-based study

AIMS/HYPOTHESIS

This register-based study aimed to describe autoimmune comorbidity in children and young adults from type 1 diabetes onset, and to investigate whether such comorbidity was associated with a difference in HbA1c or mortality risk compared with children/young adults with type 1 diabetes without autoimmune comorbidity.

METHODS

A total of 15,188 individuals from the Swedish National Diabetes Register, registered with type 1 diabetes before 18 years of age between 2000 and 2019, were included. Five randomly selected control individuals from the Swedish population (Statistics Sweden) were matched to each individual with type 1 diabetes (n=74,210 [346 individuals with type 1 diabetes were not found in the Statistics Sweden register at the date of type 1 diabetes diagnosis, so could not be matched to control individuals]). The National Patient Register was used to attain ICD-10 codes on autoimmune diseases and the Cause of Death Register was used to identify deceased individuals.

RESULTS

In the total type 1 diabetes cohort, mean±SD age at onset of type 1 diabetes was 9.5±4.4 years and mean disease duration at end of follow-up was 8.8±5.7 years. Of the individuals with type 1 diabetes, 19.2% were diagnosed with at least one autoimmune disease vs 4.0% of the control group. The HRs for comorbidities within 19 years from onset of type 1 diabetes were 11.6 (95% CI 10.6, 12.6) for coeliac disease, 10.6 (95% CI 9.6, 11.8) for thyroid disease, 1.3 (95% CI 1.1, 1.6) for psoriasis, 4.1 (95% CI 3.2, 5.3) for vitiligo, 1.7 (95% CI 1.4, 2.2) for rheumatic joint disease, 1.0 (95% CI 0.8, 1.3) for inflammatory bowel disease, 1.0 (95% CI 0.7, 1.2) for systemic connective tissue disorder, 1.4 (95% CI 1.1, 1.9) for uveitis, 18.3 (95% CI 8.4, 40.0) for Addison's disease, 1.8 (95% CI 0.9, 3.6) for multiple sclerosis, 3.7 (95% CI 1.6, 8.7) for inflammatory liver disease and 19.6 (95% CI 4.2, 92.3) for atrophic gastritis. Autoimmune disease in addition to type 1 diabetes had no statistically significant effect on HbA1c or mortality risk.

CONCLUSIONS/INTERPRETATION

To our knowledge, this is the first comprehensive study where young individuals with type 1 diabetes were followed regarding development of a wide spectrum of autoimmune diseases, from onset of type 1 diabetes. In this nationwide and population-based study, there was already a high prevalence of autoimmune diseases in childhood, especially coeliac and thyroid disease. The presence of autoimmune comorbidity did not have a statistically significant effect on metabolic control or mortality risk.

The use of antibiotic-loaded bone cement and systemic antibiotic prophylactic use in 2,971,357 primary total knee arthroplasties from 2010 to 2020: an international register-based observational study among countries in Africa, Europe, North America, and Oceania

BACKGROUND AND PURPOSE

Antibiotic-loaded bone cement (ALBC) and systemic antibiotic prophylaxis (SAP) have been used to reduce periprosthetic joint infection (PJI) rates. We investigated the use of ALBC and SAP in primary total knee arthroplasty (TKA).

PATIENTS AND METHODS

This observational study is based on 2,971,357 primary TKAs reported in 2010-2020 to national/regional joint arthroplasty registries in Australia, Denmark, Finland, Germany, Italy, the Netherlands, New Zealand, Norway, Romania, South Africa, Sweden, Switzerland, the UK, and the USA. Aggregate-level data on trends and types of bone cement, antibiotic agents, and doses and duration of SAP used was extracted from participating registries.

RESULTS

ALBC was used in 77% of the TKAs with variation ranging from 100% in Norway to 31% in the USA. Palacos R+G was the most common (62%) ALBC type used. The primary antibiotic used in ALBC was gentamicin (94%). Use of ALBC in combination with SAP was common practice (77%). Cefazolin was the most common (32%) SAP agent. The doses and duration of SAP used varied from one single preoperative dosage as standard practice in Bolzano, Italy (98%) to 1-day 4 doses in Norway (83% of the 40,709 TKAs reported to the Norwegian arthroplasty register).

CONCLUSION

The proportion of ALBC usage in primary TKA varies internationally, with gentamicin being the most common antibiotic. ALBC in combination with SAP was common practice, with cefazolin the most common SAP agent. The type of ALBC and type, dose, and duration of SAP varied among participating countries.

Prediction of Early Periprosthetic Joint Infection After Total Hip Arthroplasty

Purpose

To develop a parsimonious risk prediction model for periprosthetic joint infection (PJI) within 90 days after total hip arthroplasty (THA).

Patients and Methods

We used logistic LASSO regression with bootstrap ranking to develop a risk prediction model for PJI within 90 days based on a Swedish cohort of 88,830 patients with elective THA 2008–2015. The model was externally validated on a Danish cohort with 18,854 patients.

Results

Incidence of PJI was 2.45% in Sweden and 2.17% in Denmark. A model with the underlying diagnosis for THA, body mass index (BMI), American Society for Anesthesiologists (ASA) class, sex, age, and the presence of five defined comorbidities had an area under the curve (AUC) of 0.68 (95% CI: 0.66 to 0.69) in Sweden and 0.66 (95% CI: 0.64 to 0.69) in Denmark. This was superior to traditional models based on ASA class, Charlson, Elixhauser, or the Rx Risk V comorbidity indices. Internal calibration was good for predicted probabilities up to 10%.

Conclusion

A new PJI prediction model based on easily accessible data available before THA was developed and externally validated. The model had superior discriminatory ability compared to ASA class alone or more complex comorbidity indices and had good calibration. We provide a web-based calculator (https://erikbulow.shinyapps.io/thamortpred/) to facilitate shared decision making by patients and surgeons.

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Does the order of total hip replacement and lumbar spinal stenosis surgery influence patient-reported outcomes: An observational register study

Patients with degenerative hip and lumbar spine disorders requiring surgery in both locations is fairly common in clinical practice. We investigated if the order of total hip replacement (THR) and lumbar spinal stenosis surgery (LSSS) influences patient-reported outcomes (PROs). We used data from the Swedish Hip Arthroplasty Register (SHAR) and the Swedish Spine Register (Swespine), on patients operated with THR and LSSS in years 2002 to 2012. To increase the probability of having symptomatic disorders in both locations at the time of the first surgery, we only included patients with both LSSS and THR performed within 2 years. Linear and logistic regression analyses adjusted for age, sex, preoperative PROs, and time between surgeries were used to investigate the association between order of surgeries and the generic PRO measurements EQ-5D and EQ VAS. Eighty-four patients had THR prior to LSSS and 171 patients LSSS prior to THR. Linear regression showed that LSSS prior to THR was associated with higher EQ-5D index (B = 0.09, 95% confidence interval [CI] 0.03-0.16) and EQ VAS (B = 5.6, 95% CI 0.4-10.9) 1 year after the last surgery. Logistic regression showed that the odds ratio [OR] for not having any problems in the "pain" (OR = 3.0, 95% CI 1.5-6.3) and "anxiety/depression" (OR = 2.3, 95% CI 1.3-4.1) dimensions were higher for LSSS before THR. In our cohort, LSSS before THR was associated with better health-related quality of life outcomes compared to the reverse order. The results from our cohort can be helpful in a clinical situation where the physician gives advice to an individual patient when choosing the order of procedures. However, further studies are necessary in order to confirm these results in other cohorts. At present, standard of care remains that order of surgery should be individualized for each patient, with guidance from the operating surgeons.

Prediction of 90-day mortality after total hip arthroplasty

AIMS

To develop and externally validate a parsimonious statistical prediction model of 90-day mortality after elective total hip arthroplasty (THA), and to provide a web calculator for clinical usage.

METHODS

We included 53,099 patients with cemented THA due to osteoarthritis from the Swedish Hip Arthroplasty Registry for model derivation and internal validation, as well as 125,428 patients from England and Wales recorded in the National Joint Register for England, Wales, Northern Ireland, the Isle of Man, and the States of Guernsey (NJR) for external model validation. A model was developed using a bootstrap ranking procedure with a least absolute shrinkage and selection operator (LASSO) logistic regression model combined with piecewise linear regression. Discriminative ability was evaluated by the area under the receiver operating characteristic curve (AUC). Calibration belt plots were used to assess model calibration.

RESULTS

A main effects model combining age, sex, American Society for Anesthesiologists (ASA) class, the presence of cancer, diseases of the central nervous system, kidney disease, and diagnosed obesity had good discrimination, both internally (AUC = 0.78, 95% confidence interval (CI) 0.75 to 0.81) and externally (AUC = 0.75, 95% CI 0.73 to 0.76). This model was superior to traditional models based on the Charlson (AUC = 0.66, 95% CI 0.62 to 0.70) and Elixhauser (AUC = 0.64, 95% CI 0.59 to 0.68) comorbidity indices. The model was well calibrated for predicted probabilities up to 5%.

CONCLUSION

We developed a parsimonious model that may facilitate individualized risk assessment prior to one of the most common surgical interventions. We have published a web calculator to aid clinical decision-making. Cite this article: Bone Joint J 2021;103-B(3):469-478.

A small number of surgeons outside the control-limit: an observational study based on 9,482 cases and 208 surgeons performing primary total hip arthroplasties in western Sweden

Background and purpose - Feedback programs relating to surgeon levels have been introduced in some orthopedic quality registers around the globe. The aim of an established surgeon feedback program is to help surgeons understand their practice and enable an analysis of their own results. There is no surgeon feedback program in Sweden in the orthopedic quality registers and there is a fear that a feedback system might pinpoint surgeons as poor performers, partly due to patient case mix. As a step prior to the introduction of a future possible feedback program in Sweden, we assessed the variation in the occurrence of adverse events (AE) within 90 days and reoperations within 2 years between surgeons in western Sweden and explored the number of surgeons outside the control-limit following primary total hip arthroplasties (THAs).Patients and methods - Patient data, surgical data, and information on the surgeons, relating to surgeries performed in 2011-2016, were retrieved from 9 publicly funded hospitals in western Sweden. Data from medical hospital records, the Swedish Hip Arthroplasty Register (SHAR) and a regional patient register located in western Sweden were linked to a database. Funnel plots with control-limits based on upper 95% and 99.8% confidence intervals (CI) were used to illustrate the variation between surgeons in terms of the outcome and to explore the number of surgeons outside the control-limit. Both observed and standardized proportions are explored. The definition of surgeons outside the control-limit in the study is a surgeon above the upper 95% CI.Results - The study comprised 9,482 primary THAs due to osteoarthritis performed by 208 surgeons, where 91% of the included primary THAs were performed by orthopedic specialists and 9% by trainees. The mean overall annual volume for all surgeons was 27. The observed overall mean rate for AEs within 90 days for all surgeons was 6.2% (5.8-6.7) and for reoperations within 2 years 1.8% (1.7-2.2). The proportion of surgeons outside the 95% CI was low for both AEs (0-5%) and reoperations within 2 years (0-1%) in 2011-2016. The corresponding numbers were even lower for AEs (0-3%) but similar for reoperations (0-1%) after standardization for differences in case mix. In a sub-analysis when the number of surgeries performed was restricted to more than 10 primary THAs annually to being evaluated, almost half or more of all the surgeons were excluded from the annual analysis. The result of this restriction was that all surgeons outside the control-limit disappeared after standardization for both AEs and reoperations for all the years investigated. Considering the complete period of 6 years, less than 1% (1 high-volume surgeon for AEs and 2 high-volume surgeons for reoperations) after risk adjustments were outside the 95% CI, and no surgeons were outside the 99.8% CI.Interpretation - In a Swedish setting, the variation in surgeon performance, as measured by AEs within 90 days and reoperations within 2 years following primary THA, was small and 3% or less of the surgeons were outside the 95% CI for the investigated years after adjustments for case mix. The risk for an individual surgeon to be regarded as having poor performance when creating surgeon-specific feedback in the SHAR is very low when volume and patient risk factors are considered.

More hip complications after total hip arthroplasty than after hemi-arthroplasty as hip fracture treatment: analysis of 5,815 matched pairs in the Swedish Hip Arthroplasty Register

Background and purpose - Total hip arthroplasty (THA) is increasing as treatment of displaced femoral neck fractures. Several studies compare hemiarthroplasty (HA) with THA, but results vary and few studies report on medical complications. We examined the outcome of THA and HA with a focus on medical complications, hip complications, and death.Patients and methods - Data from the Swedish Hip Arthroplasty Register on 30,953 acute hip fracture patients treated with cemented THA or HA in 2005-2011 were cross-matched with Statistics Sweden for socioeconomic data and with the National Patient Register for diagnostic codes representing medical complications within 180 days or hip complications within the study period. Propensity score matching was used to create comparable groups based on age, sex, income, level of education, marital status, Elixhauser index, and year of surgery. Logistic regression models were created for each outcome.Results - 81% were treated with HA, 73% and 71% were female (HA and THA respectively). Matching resulted in 2 groups of 5,815 patients each. THA was associated with fewer medical complications (OR = 0.83; 95% CI 0.76-0.91) and lower 1-year mortality (OR = 0.42; CI 0.38-0.48), but more hip complications (OR = 1.31; CI 1.20-1.43).Interpretation - THA as treatment of hip fracture was associated with more hip-related complications than HA. The results on mortality and medical complications are, rather, influenced by residual confounding than by the implant design per se. An expansive use of THAs for hip fracture treatment, at the expense of HAs, is not recommended based on our findings if hip complications are to be avoided.

Association between patient survival following reoperation after total hip replacement and the reason for reoperation: an analysis of 9,926 patients in the Swedish Hip Arthroplasty Register

Background and purpose - The association between long-term patient survival and elective primary total hip replacement (THR) has been described extensively. The long-term survival following reoperation of THR is less well understood. We investigated the relative survival of patients undergoing reoperation following elective THR and explored an association between the indication for the reoperation and relative survival. Patients and methods - In this observational cohort study we selected the patients who received an elective primary THR and subsequent reoperations during 1999-2017 as recorded in the Swedish Hip Arthroplasty Register. The selected cohort was followed until the end of the study period, censoring or death. The indications for 1st- and eventual 2nd-time reoperations were analyzed and the relative survival ratio of the observed survival and the expected survival was determined. Results - There were 9,926 1st-time reoperations and of these 2,558 underwent further reoperations. At 5 years after the latest reoperation, relative survival following 1st-time reoperations was 0.94% (95% CI 0.93-0.96) and 0.90% (CI 0.87-0.92) following 2nd-time reoperations. At 5 years patients with a 1st-time reoperation for aseptic loosening had higher survival than expected; however, reoperations performed for periprosthetic fracture, dislocation, and infection had lower survival. Interpretation - The relative survival following 1st- and 2nd-time reoperations in elective THR patients differs by reason for reoperation. The impact of reoperation on life expectancy is more obvious for infection/dislocation and periprosthetic fracture.

Multi-state analysis of hemi- and total hip arthroplasty for hip fractures in the Swedish population-Results from a Swedish national database study of 38,912 patients

INTRODUCTION

Hip fractures are a common problem of the elderly population with significant mortality and morbidity. The choice between total hip arthroplasty (THA) and hemiarthroplasty depends on multiple factors including comorbidity. The Swedish Hip Arthroplasty Register (SHAR) provides a unique opportunity to study mortality and revision rates in this population. Linkage with government databases allow for in-depth research into the factors that influence risk of revision surgery and death in the hip fracture patient.

PATIENTS AND METHODS

Data was linked between SHAR, Statistics Sweden and the National Board of Health and Welfare. Data was collected on 38,912 patients who received a fracture-related hip arthroplasty between 2005 and 2012. A multistate analysis was performed and three states were identified: primary hip surgery and alive (state 1), revision after primary hip surgery (state 2) and death (state 3). These were marking points in the longitudinal outcome study.

RESULTS

38,912 patients who received an arthroplasty for an acute hip fracture were included. By the end of the study period 1309 (3.4%) of these patients underwent a revision and 17,365 (45.1%) patients died. Patients with THA had a reduced risk of death from primary operation compared to hemiarthroplasty (HR = 0.49) and a decreased revision risk (HR = 0.69). Female patients had a statistically significant reduced mortality (HR = 0.6) compared to men. There was no statistically significant difference in risk of revision surgery between direct lateral and posterior approach.

CONCLUSION

We identified an influence of type of surgery, sex, age and Elixhauser Comorbidity Index (ECI) on risk of revision and mortality. Males, greater comorbidity burden and older patients had higher mortality risks. The posterior approach did not have a significant influence on revision risk. Further research could include all patients who had reoperation(s) to further strengthen our findings. Patients who had a THA had lower revision rate and mortality. The latter is likely due to selection.

Low predictive power of comorbidity indices identified for mortality after acute arthroplasty surgery undertaken for femoral neck fracture

Aims

Our aim was to examine the Elixhauser and Charlson comorbidity indices, based on administrative data available before surgery, and to establish their predictive value for mortality for patients who underwent hip arthroplasty in the management of a femoral neck fracture.

Patients and Methods

We analyzed data from 42 354 patients from the Swedish Hip Arthroplasty Register between 2005 and 2012. Only the first operated hip was included for patients with bilateral arthroplasty. We obtained comorbidity data by linkage from the Swedish National Patient Register, as well as death dates from the national population register. We used univariable Cox regression models to predict mortality based on the comorbidity indices, as well as multivariable regression with age and gender. Predictive power was evaluated by a concordance index, ranging from 0.5 to 1 (with the higher value being the better predictive power). A concordance index less than 0.7 was considered poor. We used bootstrapping for internal validation of the results.

Results

The predictive power of mortality was poor for both the Elixhauser and Charlson comorbidity indices (concordance indices less than 0.7). The Charlson Comorbidity Index was superior to Elixhauser, and a model with age and gender was superior to both indices.

Conclusion

Preoperative comorbidity from administrative data did not predict mortality for patients with a hip fracture treated by arthroplasty. This was true even if association on group level existed.

Relative survival following hemi-and total hip arthroplasty for hip fractures in Sweden

BACKGROUND

Hip fractures are a common problem in the ageing population. Hip arthroplasty is the common treatment option for displaced intracapsular neck of femur fractures. Even though hip replacements are successful in restoring mobility, reducing pain and diminishing loss of health-related quality of life, the potential impact of a hip fracture on life expectancy as well as the postoperative mortality need consideration. The purpose of this study was to describe the mid-term relative survival rate for a cohort of Swedish patients whom underwent total- or hemiarthroplasty surgery following hip fracture. We also explored whether the survival rate is prosthesis-type specific and influenced by comorbidities, sex, socioeconomic and surgical factors.

METHODS

Using prospectively collected information of the Swedish Hip Arthroplasty Register-linked database we identified 43,891 patients operated between 2005 and 2012. Patient- and surgery-specific data in combination with socio-economic data were available for this analysis. We studied relative survival rate and used multivariable modelling with Cox Proportional Hazards Model in Transformed Time.

RESULTS

Compared to the Swedish general population the baseline excess hazard was very high in the first half year after the operation, thereafter the excess hazard decreased but remained non-negligible through the 8 years' follow-up period. The mortality rate of males was higher compared to women. Higher Elixhauser comorbidity index (ECI) was associated with worsening survival. However, patients who had ECI = 0 had higher mortality than patients with ECI =1 the first 420 days post fracture. Patients with a hemiarthroplasty had a worse survival than patients with a total hip arthroplasty. Of the hospital types considered university hospitals had lower survival rate. Younger patients had a greater loss of expected life span than patients who suffer hip fracture in their more advanced ages.

CONCLUSIONS

Swedish hip fracture patients who undergo arthroplasty surgery had a high excess hazard of dying in the first half year following surgery, and this excess hazard never subsided to negligible levels at least up to 8 years after surgery. Interestingly having no prior record of illnesses worsened the initial mortality. Men living alone had the highest long-term excess mortality.

Patients with a previous total hip replacement experience less reduction of back pain following lumbar back surgery

The coexistence of degenerative disorders from the hip joint and the lumbar spine, known as "the hip-spine syndrome," is a common encounter in clinical practice. These degenerative conditions may cause similar symptoms which often entail diagnostic challenges in determining the origin of pain. Lumbar back surgery (LBS) with fusion and/or decompression, and total hip replacement (THR) are both often successful interventions. However, the knowledge is limited about the post-operative patient-reported outcome (PRO) following LBS in the presence of a prior THR. The aims of this study were to compare 1-year post-operative patient-reported outcome measures (PROMs) following lumbar back surgery (LBS) in patients with and without a prior total hip replacement (THR). Data from Swespine and the Swedish Hip Arthroplasty Register were linked in order to identify the study group of patients with THR prior to LBS. The study group (n = 220) and a matched control group (n = 220) with isolated LBS was defined by using a step-wise selection process. Linear- and logistic regression analyses adjusted for age, sex and pre-operative PROMs demonstrated that THR prior to LBS was associated with worse back-pain (VAS) at 1-year follow-up (B = 5.3, 95%CI: 0.3;10.3). However, previous THR did not influence the EQ-5D index (B = 0.01, 95%CI: -0.05;0.06), EQ VAS (B = -3.0, 95%CI: -6.9;1.0), leg pain (B = 1.5, 95%CI: -4.0;7.0), Oswestry Disability Index (B = 2.6, 95%CI: -0.5;5.6) or satisfaction (OR = 1.1, 97.5%CI 0.7;1.6). This knowledge is important to communicate prior to LBS in order to set proper expectations on surgical outcomes. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2484-2490, 2018.

Risk of further surgery on the same or opposite side and mortality after primary total hip arthroplasty: A multi-state analysis of 133,654 patients from the Swedish Hip Arthroplasty Register

Background and purpose - The hip-related timeline of patients following a total hip arthroplasty (THA) can vary. Ideally patients will live their life without need for further surgery; however, some will undergo replacement on the contralateral hip and/or reoperations. We analyzed the probability of mortality and further hip-related surgery on the same or contralateral hip. Patients and methods - We performed a multi-state survival analysis on a prospectively followed cohort of 133,654 Swedish patients undergoing an elective THA between 1999 and 2012. The study used longitudinally collected information from the Swedish Hip Arthroplasty Register and administrative databases. The analysis considered the patients' sex, age, prosthesis type, surgical approach, diagnosis, comorbidities, education, and civil status. Results - During the study period patients were twice as likely to have their contralateral hip replaced than to die. However, with passing time, probabilities converged and for a patient who only had 1 non-revised THA at 10 years, there was an equal chance of receiving a second THA and dying (24%). It was 8 times more likely that the second hip would become operated with a primary THA than that the first hip would be revised. Multivariable regression analysis reinforced the influence of age at operation, sex, diagnosis, comorbidity, and socioeconomic status influencing state transition. Interpretation - Multi-state analysis can provide a comprehensive model of further states and transition probabilities after an elective THA. Information regarding the lifetime risk for bilateral surgery, revision, and death can be of value when discussing the future possible outcomes with patients, in healthcare planning, and for the healthcare economy.

Can patient-reported outcomes predict re-operations after total hip replacement?

PURPOSE

We investigated if patient-reported outcomes (PROMs) one year after total hip replacement (THR) can predict the risk of re-operation using data from the Swedish Hip Arthroplasty Register.

METHODS

A total of 75,899 patients with THR due to osteoarthritis operated in 2002-2014 were included. We used Kaplan-Meier and Cox regression to investigate the relationship between one-year post-operative PROMs and risk of re-operation (all types of further hip surgery). The predictive power of the model and post-operative PROMs were evaluated by concordance index (C).

RESULTS

Kaplan-Meier estimates for not being re-operated at eight years was 95.5% (95%CI; 95.3-95.8). Cox regression analyses showed that all PROMs, except for EQ-VAS, were associated with re-operation. The full model had a concordance index of 0.68. Satisfaction (C = 0.65) and pain (C = 0.65) in isolation had the highest predictive power.

CONCLUSIONS

Worse PROMs predicted higher risk of re-operation. Therefore, we believe PROMs may be helpful in identifying patients at risk for re-operation and timely address their problems.

Trends in hip replacements between 1999 and 2012 in Sweden

National Registers document changes in the circumstance, practice, and outcome of surgery with the passage of time. In the context of total hip replacement (THR), registers can help elucidate the relevant factors that affect the clinical outcome. We evaluated the evolution of factors related to patient, surgical procedure, socio-economy, and various outcome parameters after merging databases of the Swedish Hip Arthroplasty Register, Statistics Sweden and the National Board of Health and Welfare. Data on 193,253 THRs (164,113 patients) operated between 1999 and 2012 were merged. We studied the evolution of surgical volume, patient demographics, socio-economic factors, surgical factors, length-of-stay, mortality rate, adverse events, re-operation and revision rates, and Patient Reported Outcome Measures (PROMs). Throughout this time period the majority of patients were operated on with a diagnosis of primary osteoarthritis. Comorbidity indices increased each year observed. The share of all-cemented implants has dropped from 92% to 68%. More than 88% of the bearings were metal-on-polyethylene. Length-of-stay decreased by 50%. There was a reduction in 30- and 90-day mortality. Re-operation and revision rates at 2 years are decreasing. The post-operative PROMs improved despite the observation of worse pre-operative pain scores getting over time. The demographics of patients receiving a THR, their comorbidities, and their primary diagnosis are changing. Notwithstanding these changes, outcomes like mortality, re-operations, revisions, and PROMs have improved. The practice of hip arthroplasty has evolved, even in a country such as Sweden that is considered to be conservative with regard taking on new surgical practices. © 2017 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 36:432-442, 2018.

Comorbidity does not predict long-term mortality after total hip arthroplasty

Background and purpose - In-hospital death following total hip arthroplasty (THA) is related to comorbidity. The long-term effect of comorbidity on all-cause mortality is, however, unknown for this group of patients and it was investigated in this study. Patients and methods - We used data from the Swedish Hip Arthroplasty Register, linked to the National Patient Register from the National Board of Health and Welfare, for patients operated on with THA in 1999-2012. We identified 120,836 THAs that could be included in the study. We evaluated the predictive power of the Charlson and Elixhauser comorbidity indices on mortality, using concordance indices calculated after 5, 8, and 14 years after THA. Results - All comorbidity indices performed poorly as predictors, in fact worse than a base model with age and sex only. Elixhauser was, however, the least bad choice and it predicted mortality with concordance indices 0.59, 0.58, and 0.56 for 5, 8, and 14 years after THA. Interpretation - Comorbidity indices are poor predictors of long-term mortality after THA.

Sorting for storage in myeloid cells of nonmyeloid proteins and chimeras with the propeptide of myeloperoxidase precursor

During formation of polymorphonuclear neutrophils, proteins are synthesized for storage in granules. Whereas sorting of proteins into distinct subtypes of cytoplasmic granules may reflect the coordinated expression of the proteins contained in them, still the mechanism(s) for the retrieval of proteins from the constitutive secretion is unknown. To investigate the mechanisms of retrieval, nonmyeloid secretory proteins were expressed in myeloid cell lines, and their subcellular fate was assessed. The contribution of the propeptide (MPOpro) of the myeloperoxidase (MPO) precursor was investigated by determining the fate of chimeras containing MPOpro. The nonmyeloid protein alpha(1)-microglobulin (alpha(1)-m) was targeted to storage organelles in 32D cells and colocalized with the lysosomal marker LAMP-1, whereas soluble TNF receptor 1 (sTNFR1) was secreted without granule targeting. Fusion of MPOpro to alpha(1)-m delayed exit from endoplasmic reticulum (ER), but subsequent targeting to dense organelles was indistinguishable from that of alpha(1)-m alone. Fusion proteins between MPOpro and sTNFR1 or green fluorescent protein expressed in myeloid 32D, K562, or PLB-985 cells did not associate stably with calreticulin or calnexin, molecular chaperones that normally interact transiently with the MPO precursor, but were still efficiently retained in the ER followed by degradation. We conclude that normally secreted, nonmyeloid proteins can be targeted efficiently to storage organelles in myeloid cells, that myeloid cells selectively target some proteins for storage but not others, and that MPOpro may contribute to the prolonged ER retention of the MPO precursor independent of the ER-molecular chaperones calreticulin and calnexin.

Structural requirements for intracellular processing and sorting of bactericidal/permeability-increasing protein (BPI): comparison with lipopolysaccharide-binding protein

The bactericidal/permeability-increasing protein (BPI), which is stored in the azurophil granules of neutrophils, and the circulating lipopolysaccharide-binding protein (LBP) share the same structure. Both bind lipopolysaccharide of gram-negative bacteria through their amino-terminal domains. The carboxy-terminal domain of BPI promotes bacterial attachment to phagocytes, whereas the corresponding domain of LBP delivers lipopolysaccharide to monocytes/macrophages. Our aim was to investigate the role of the amino-and carboxy-terminal domains of BPI and LBP for sorting and storage in myeloid cells after transfection of cDNA to two rodent hematopoietic cell lines. Full-length BPI and LBP were both targeted for storage in these cells. Deletion of the carboxy-terminal half of BPI resulted in storage followed by degradation while the reciprocal deletion of the amino-terminal half led to retention in the endoplasmic reticulum for proteasomal degradation. Chimeras between halves of BPI and LBP were also targeted for storage, but those containing carboxy-terminal BPI had the highest stability, again indicating a role for the carboxy-terminal domain of BPI in protection against degradation. Therefore, we propose a critical stability function for the hydrophobic carboxy-terminal domain of BPI during intracellular sorting for storage while the amino-terminal domain may confer targeting for storage.

Processing and targeting of granule proteins in human neutrophils

Neutrophils contain an assembly of granules destined for regulated secretion, each granule type with distinct constituents formed before terminal differentiation. The earliest granules are designated azurophil (primary), followed in time by specific (secondary), and gelatinase granules as well as secretory vesicles. Transcription factors regulate the genes for the granule proteins to ensure that expression of the gene products to be stored in different organelles is separated in time. Similar to lysosomal enzymes, many granule proteins, in particular those of the heterogeneous azurophil granules, are trimmed by proteolytic processing into mature proteins. Rodent myeloid cell lines have been utilized for research on the processing and targeting of human granule proteins after transfection of cDNA. Results from extensive work on the hematopoietic serine proteases of azurophil granules, employing in vitro mutagenesis, indicate that both an immature and a mature conformation are compatible with targeting for storage in granules. On the other hand, the amino-terminal propeptide of myeloperoxidase facilitates both the export from the endoplasmic reticulum and targeting for storage in granules. Similarly, targeting of defensins rely on an intact propeptide. The proteolytic processing into mature granule protein is most commonly a post-sorting event. Mis-sorting of specific granule proteins into azurophil or lysosome-like granules can result in premature activation and degradation, but represents a potential for manipulating the composition and function of neutrophil granules.