Socioeconomic status affects patient-reported outcome measures in total hip and knee arthroplasty: A retrospective Dutch registry study

BACKGROUND

To determine the association between socioeconomic status and patient-reported outcome measures in a Dutch cohort who have undergone total hip arthroplasty (THA) or total knee arthroplasty (TKA).

METHODS

A retrospective national registry study of all patients who underwent primary THA or TKA between 2014-2020 in the Netherlands was performed. Linear mixed-effects regression models were used to assess the association between SES and PROMs for THA and TKA patients separately. The following measures were collected: Numeric pain rating scale, Oxford Hip/Knee Score, Hip/Knee disability and Osteoarthritis Outcome Score and the EuroQol 5-Dimensions-questionnaire. Sex, age, body mass index, American Society of Anesthesiologists-classification, Charnley-classification and smoking status were considered as covariates in the models.

RESULTS

THA patients (n=97,443) were on average 70 years old with a BMI of 27.4 kg/m2, and TKA patients (n=78,811) were on average 69 years old with a BMI of 29.7 kg/m2. Preoperatively, patients with a lower socioeconomic status undergoing THA or TKA reported more severe symptoms and lower health-related quality of life. At 1-year follow-up, they also reported lower scores and less improvement over time compared to patients with a higher socioeconomic status.

CONCLUSION

Patients with lower socioeconomic status report worse symptoms when admitted for surgery, and less improvement after surgery. Future research must address potentially mediating factors of the association between socioeconomic status and symptom reporting such as access to surgery and rehabilitation, subjectivity in reporting, and patient expectation for THA and TKA outcomes.

Machine Learning Did Not Outperform Conventional Competing Risk Modeling to Predict Revision Arthroplasty

BACKGROUND

Estimating the risk of revision after arthroplasty could inform patient and surgeon decision-making. However, there is a lack of well-performing prediction models assisting in this task, which may be due to current conventional modeling approaches such as traditional survivorship estimators (such as Kaplan-Meier) or competing risk estimators. Recent advances in machine learning survival analysis might improve decision support tools in this setting. Therefore, this study aimed to assess the performance of machine learning compared with that of conventional modeling to predict revision after arthroplasty.

QUESTION/PURPOSE

Does machine learning perform better than traditional regression models for estimating the risk of revision for patients undergoing hip or knee arthroplasty?

METHODS

Eleven datasets from published studies from the Dutch Arthroplasty Register reporting on factors associated with revision or survival after partial or total knee and hip arthroplasty between 2018 and 2022 were included in our study. The 11 datasets were observational registry studies, with a sample size ranging from 3038 to 218,214 procedures. We developed a set of time-to-event models for each dataset, leading to 11 comparisons. A set of predictors (factors associated with revision surgery) was identified based on the variables that were selected in the included studies. We assessed the predictive performance of two state-of-the-art statistical time-to-event models for 1-, 2-, and 3-year follow-up: a Fine and Gray model (which models the cumulative incidence of revision) and a cause-specific Cox model (which models the hazard of revision). These were compared with a machine-learning approach (a random survival forest model, which is a decision tree-based machine-learning algorithm for time-to-event analysis). Performance was assessed according to discriminative ability (time-dependent area under the receiver operating curve), calibration (slope and intercept), and overall prediction error (scaled Brier score). Discrimination, known as the area under the receiver operating characteristic curve, measures the model's ability to distinguish patients who achieved the outcomes from those who did not and ranges from 0.5 to 1.0, with 1.0 indicating the highest discrimination score and 0.50 the lowest. Calibration plots the predicted versus the observed probabilities; a perfect plot has an intercept of 0 and a slope of 1. The Brier score calculates a composite of discrimination and calibration, with 0 indicating perfect prediction and 1 the poorest. A scaled version of the Brier score, 1 - (model Brier score/null model Brier score), can be interpreted as the amount of overall prediction error.

RESULTS

Using machine learning survivorship analysis, we found no differences between the competing risks estimator and traditional regression models for patients undergoing arthroplasty in terms of discriminative ability (patients who received a revision compared with those who did not). We found no consistent differences between the validated performance (time-dependent area under the receiver operating characteristic curve) of different modeling approaches because these values ranged between -0.04 and 0.03 across the 11 datasets (the time-dependent area under the receiver operating characteristic curve of the models across 11 datasets ranged between 0.52 to 0.68). In addition, the calibration metrics and scaled Brier scores produced comparable estimates, showing no advantage of machine learning over traditional regression models.

CONCLUSION

Machine learning did not outperform traditional regression models.

CLINICAL RELEVANCE

Neither machine learning modeling nor traditional regression methods were sufficiently accurate in order to offer prognostic information when predicting revision arthroplasty. The benefit of these modeling approaches may be limited in this context.

Socioeconomic inequalities in patient-reported outcome measures of Dutch primary hip and knee arthroplasty patients for osteoarthritis

OBJECTIVE

To study socio-economic inequalities in patient-reported outcomes in primary hip and knee arthroplasty (THA/TKA) patients for osteoarthritis, using two analytical techniques.

METHODS

We obtained data from 44,732 THA and 30,756 TKA patients with preoperative and 12-month follow-up PROMs between 2014 and 2020 from the Dutch Arthroplasty Registry. A deprivation indicator based on neighborhood income, unemployment rate, and education level was linked and categorized into quintiles. The primary outcome measures were the EQ-5D-3L index and Oxford Hip/Knee Score (OHS/OKS) preoperative, at 12-month follow-up, and the calculated change score between these measurements. We contrasted the most and least deprived quintiles using multivariable linear regression, adjusting for patient characteristics. Concurrently, we calculated concentration indices as a non-arbitrary tool to quantify inequalities.

RESULTS

Compared to the least deprived, the most deprived THA patients had poorer preoperative (EQ-5D -0.03 (95%CI -0.02, -0.04), OHS -1.26 (-0.99, -1.52)) and 12-month follow-up health (EQ-5D -0.02 (-0.01, -0.02), OHS -0.42 (-0.19, -0.65)), yet higher mean change (EQ-5D 0.02 (0.01, 0.03), OHS 0.84 (0.52, 1.16)). The most deprived TKA patients had similar results. The higher mean change among the deprived resulted from lower preoperative health in this group (confounding). After accounting for this, the most deprived patients had a lower mean change. The concentration indices showed similar inequality effects and provided information on the magnitude of inequalities over the entire socio-economic range.

CONCLUSION

The most deprived THA and TKA patients have worse preoperative health, which persisted after surgery. The concentration indices allow comparison of inequalities across different outcomes (e.g., revision risk).

Femoral Neck Design Does Not Impact Revision Risk After Primary Total Hip Arthroplasty Using a Dual Mobility Cup

Background

The use of dual mobility (DM) cups has increased quickly. It is hypothesized that femoral neck taper geometry may be involved in the risk of prosthetic impingement and DM cup revision. We aim to (1) explore the reasons for revision of DM cups or head/liners and (2) explore whether certain femoral neck characteristics are associated with a higher risk of revision of DM cups.

Methods

Primary total hip arthroplasties with a DM cup registered in the Dutch Arthroplasty Register between 2007 and 2021 were identified (n = 7603). Competing risk survival analyses were performed, with acetabular component and head/liner revision as the primary endpoint. Reasons for revision were categorized in cup-/liner-related revisions (dislocation, liner wear, acetabular loosening). Femoral neck characteristics were studied to assess whether there is an association between femoral neck design and the risk of DM cup/liner revision. Multivariable Cox proportional hazard analyses were performed.

Results

The 5- and 10-year crude cumulative incidence of DM cup or head/liner revision for dislocation, wear, and acetabular loosening was 0.5% (CI 0.4-0.8) and 1.9% (CI 1.3-2.8), respectively. After adjusting for confounders, we found no association between the examined femoral neck characteristics (alloy used, neck geometry, CCD angle, and surface roughness) and the risk for revision for dislocation, wear, and acetabular loosening.

Conclusions

The risk of DM cup or head/liner revision for dislocation, wear, and acetabular loosening was low. We found no evidence that there is an association between femoral neck design and the risk of cup or head/liner revision.

The Rise of the Direct Anterior Approach: Trends, Learning Curves, and Patient Characteristics of 63,182 Primary Total Hip Arthroplasties in the Dutch Arthroplasty Register (LROI)

BACKGROUND

The use of the direct anterior approach (DAA) in total hip arthroplasty (THA) has steadily increased in the Netherlands since 2007. The aim of this study was to outline how the DAA has been implemented in the Netherlands. Moreover, we investigated the learning curve of the DAA at a hospital level, and explored patient characteristics of the DAA compared with other approaches and during the learning phase after implementing the DAA.

METHODS

In this population-based cohort study, we included all primary THAs between 2007 and 2020 (n = 342,473) from the Dutch Arthroplasty Register. For hospitals implementing the DAA (n > 20), patients were categorized in 4 experience groups using the date of surgery: 1 to 50, 51 to 100, 101 to 150, or > 150. Subsequently, data from different hospitals were pooled and survival rates were calculated using Kaplan-Meier survival analyses. Adjusted revision rates were calculated using mixed Cox proportional hazard models (frailty).

RESULTS

The use of the DAA gradually rose from 0.2% in 2007 to 41% of all primary THAs in 2020. A total of 64 (56%) hospitals implemented the DAA. However, not all hospitals continued using this approach. After implementation, the 5-year survival rate for the first 50 procedures was significantly lower (96% confidence interval [CI] 95.8 to 97.2) compared to >150 procedures (98% CI 97.7 to 98.1). Multivariable Cox hazard analyses demonstrated a higher risk of revision during the first 50 procedures compared with >150 procedures (hazard ratio 1.6, CI 1.3 to 2.0).

CONCLUSIONS

The use of DAA for primary THA significantly increased. For hospitals implementing DAA, a considerable learning curve with increased revision risk was seen.

Revision Risk of Unipolar and Bipolar Hemiarthroplasties in the Dutch Arthroplasty Register

BACKGROUND

Hemiarthroplasty (HA) for hip fractures can be performed with a unipolar or bipolar head. We describe the use of unipolar and bipolar HA after a hip fracture in the Netherlands and determined revision rates and risk factors.

METHODS

All HAs for an acute hip fracture registered in the Dutch Arthroplasty Register (LROI) during 2007 to 2021 were included; 44,127(88%) unipolar and 6,013(12%) bipolar HAs. Competing risk survival analyses were performed with revision for any reason as the endpoint. Multivariable Cox regression analyses were performed adjusting for patient and surgery-related factors.

RESULTS

The 1-year, 5-year, and 10-year revision rates were comparable for unipolar and bipolar HA. Cox regression analysis showed a hazard ratio of 1.2 (95% confidence interval (CI) 1.0 to 1.4)) after adjustment for confounders for bipolar heads. In cases of a cemented stem, the 1-year cumulative incidence of revision was lower (1.5% (CI 1.4 to 1.7%) compared to uncemented stems (2.4% (CI 2.1 to 2.7%); uncemented stems showed higher risks for revision after adjustment compared to cemented stems (hazard ratio 1.4 (CI 1.2 to 1.5)). The anterior, antero-lateral, and straight-lateral approach showed lower risk for revision compared to the postero-lateral approach.

CONCLUSION

The revision rate for bipolar HA and unipolar HA was comparable. However, after adjustment for potential confounders the risk for revision showed an estimated 20% increased revision risk for bipolar heads, although not statistically significant. For both head types, the risk for revision was significantly higher when an uncemented stem was chosen or the postero-lateral approach was used.

Reduced 5-Year Risk for Revision of the Oxford UKA Using New Instrumentation versus Conventional Instrumentation: A Registry Study of 12,867 UKAs

Microplasty instrumentation was introduced for a more consistent surgical implantation technique, especially component alignment and tibial resection level, of the Oxford medial unicompartmental knee arthroplasty (UKA) and thereby aims to improve UKA survival. This study aimed to assess the 5-year risk for revision and reasons for revision of the Oxford medial UKA using the new instrumentation (Microplasty) with its predecessor, that is, conventional instrumentation (Phase 3). Data of all medial UKAs from the Dutch Arthroplasty Register (Landelijke Registratie Orthopedische Implantaten) between 2007 and 2019 were collected. Type of instrumentation was divided into new (Microplasty) and conventional instrumentation. Kaplan-Meier analysis was performed to calculate 5-year cumulative revision percentage with any reason for revision as end point. A multivariable Cox regression with outcome revision of UKA adjusted for age, gender, American Society of Anesthesiologists score, surgical history, and type of fixation was performed. Additionally, reasons for revision at 3-year were assessed and tested through Fisher's exact tests. A total of 12,867 Oxford medial UKAs, 8,170 using new and 4,697 using conventional instrumentation, were included. The 5-year revision percentage was 9.2% (95% confidence interval [CI]: 8.4-10.1%) for UKAs using the conventional and 6.1% (95% CI: 5.4-6.7%) for new instrumentation. The adjusted hazard ratio for revision at 5-year follow-up was 0.74 (95% CI: 0.63-0.87) in favor of UKAs using the new instrumentation. Malalignment was more frequently registered as reason for revision in UKAs using the conventional compared with the new instrumentation (16% versus 7.5%; p = 0.001). Our results show a reduced 5-year risk for revision of the medial Oxford UKAs using the new compared with the conventional instrumentation. This might be the result of a lower revision rate for malalignment in UKAs using the new instrumentation.

Femoral head size and surgical approach affect dislocation and overall revision rates in total hip arthroplasty: up to 9-year follow-up data of 269,280 procedures in the Dutch Arthroplasty Register (LROI)

BACKGROUND

Femoral head size and surgical approach might affect the revision rate for dislocation and for any other reason after total hip arthroplasty (THA). We penetrated this question based on registry data with up to 9-year follow-up.

METHODS

269,280 primary THAs documented in the Dutch Arthroplasty Registry (LROI) between 2007 and 2019 were included. Revision rates were calculated by competing risk analyses. Multivariable Cox proportional hazard regression ratios (HR) were used for comparison.

RESULTS

Revisions for dislocation were rare. They were more frequent after posterolateral (1.4% [95% CI, 1.3-1.5]), compared to straight lateral (0.6% [95% CI, 0.5-0.7]), anterolateral (0.6% [95% CI, 0.5-0.7]) and anterior (0.4% [95% CI, 0.3-0.5]) approach. Larger femoral head size decreased the dislocation revision risk: 1.4% [95% CI, 1.3-1.5) for 22-28-mm heads; 0.9% (95% CI, 0.8-1.0) for 32-mm heads; 0.6% (95% CI, 0.6-0.7) for 36-mm heads. For the anterior approach, the HR for both revision for dislocation (0.3, 95% CI, 0.3-0.4) and any other reason (0.8, 95% CI, 0.8-0.9) were lowest compared to other approaches including posterolateral (HR 1). Revision risk for any other reason was highest with anterolateral (HR 1.3 (95% CI, 1.2-1.4)) and straight lateral approach (1.1 [95% CI, 1.0-1.2]).

CONCLUSIONS

The anterior approach might reduce revision rates for both dislocation and all cause revision. Posterolateral approach is associated with a higher risk of dislocation revision but has a lower risk of any other revision. Increasing femoral head size up to 36 mm reduces revision for dislocation and improves overall revision rates for all approaches.

No clinically relevant difference in patient-reported outcomes between the direct superior approach and the posterolateral or anterior approach for primary total hip arthroplasty: analysis of 37,976 primary hip arthroplasties in the Dutch Arthroplasty Registry

BACKGROUND AND PURPOSE

The direct superior approach (DSA) is a modification of the posterolateral approach (PLA) for total hip arthroplasty (THA). Patient-reported outcome measures (PROMs) of the DSA have not been investigated previously using nationwide data. Our aim was to assess PROMs after THA using the DSA compared with the PLA and, secondarily, with the anterior approach (DAA).

PATIENTS AND METHODS

In this population-based cohort study we included 37,976 primary THAs performed between 2014 and 2020 (PLA: n = 22,616; DAA: n = 15,017; DSA: n = 343) using Dutch Arthroplasty Registry data. PROMs (NRS pain, EQ-5D, HOOS-PS, and OHS) were measured preoperatively, and at 3 and 12 months postoperatively. Repeated measurements were analyzed using mixed-effects models, adjusted for confounders, to investigate the association between surgical approach and PROMs over time.

RESULTS

From baseline to 3 and 12 months, improvements for NRS pain scores, EQ-5D, and OHS were comparable for the DSA compared with the PLA or DAA. No difference was found in HOOS-PS improvement 3 months postoperatively between DSA and PLA (-0.2, 95% confidence interval [CI] -2.4 to 1.9) and between DSA and DAA (-1.7, CI -3.9 to 0.5). At 12 months postoperatively, patients in the DSA group had improved -2.8 points (CI -4.9 to -0.6) more in HOOS-PS compared with the DAA, but not with the PLA group (-1.0, CI -3.2 to 1.1).

CONCLUSION

Our study showed no clinically meaningful differences between the DSA and either PLA or DAA.

[The shoulder prosthesis in the past 7 years: increasingly used, with good results]

The shoulder prosthesis is increasingly used as a solution for various shoulder problems. On the basis of a few cases, an overview is given of the various situations in which a shoulder prosthesis can be used, with a small risk of complications, a high risk of pain reduction and a long survival. In addition, a shoulder prosthesis improves the quality of life and is cost-effective. It is important, however, to set the correct indication with an eye for various psychosocial factors. The individual end result depends on patient-related factors such as pathology, general condition, activity and expectations. But the type of prosthesis and surgical expertise and experience also play a role.

Out-of-hospital opioid prescriptions after knee and hip arthroplasty: prescribers and the first prescribed opioid

BACKGROUND

We determined the first prescribed opioid and the prescribers of opioids after knee and hip arthroplasty (KA/HA) between 2013 and 2018 in the Netherlands. We also evaluated whether the first prescribed opioid dose was associated with the total dispensed dose and long-term opioid use in the first postoperative year.

METHODS

The Dutch Foundation for Pharmaceutical Statistics was linked to the Dutch Arthroplasty Register. Stratified for KA/HA, the first out-of-hospital opioid within 30 days of operation was quantified as median morphine milligram equivalent (MME). Opioid prescribers were orthopaedic surgeons, general practitioners, rheumatologists, anaesthesiologists, and other physicians. Long-term use was defined as ≥1 opioid prescription for >90 postoperative days. We used linear and logistic regression analyses adjusted for confounders.

RESULTS

Seventy percent of 46 106 KAs and 51% of the 42 893 HAs were prescribed ≥1 opioid. Oxycodone increased as first prescribed opioid (from 44% to 85%) whereas tramadol decreased (64-11%), but their dosage remained stable (stronger opioids were preferred by prescribers). An increase in the first prescription of 1% MME resulted in a 0.43%/0.37% increase in total MME (KA/HA, respectively). A 100 MME increase in dose of the first dispensed opioid had a small effect on long-term use (prevalence: 25% KA, 20% HA) (odds ratio=1.02/1.01 for KA/HA, respectively). Orthopaedic surgeons increasingly prescribed the first prescription between 2013 and 2018 (44-69%). General practitioners mostly prescribed consecutive prescriptions (>50%).

CONCLUSION

Oxycodone increased as first out-of-hospital prescription between 2013 and 2018. The dose of the first prescribed opioid was associated with the total dose and a small increased risk of prolonged use. First prescriptions were mostly written by orthopaedic surgeons and consecutive prescriptions by general practitioners.

A significant change towards cemented fixation in revision total hip arthroplasty in patients younger than 55 years in the Netherlands: results of an observational cohort study in the Dutch Arthroplasty Register in 28,516 primary hip replacements and 1285 revision procedures

BACKGROUND

Worldwide, the majority of total hip arthroplasties (THAs) placed in patients <55 years are uncemented. However, little is known about the preferred method of fixation in revision hip arthroplasty in young patients. The aim of this study was to assess potential differences in the method of fixation used between primary and revision THA in young patients using data from the Dutch Arthroplasty Register.

METHODS

All primary THA placed in patients younger than 55 years, registered in the LROI between 2007 and 2019 were included n = 28,516). Kaplan-Meier survival analyses were used to estimate the survival of primary THA by method of fixation. Additionally, survival of revision procedures that changed or did not change in method of fixation were estimated. McNemar's test was used to assess differences in the proportion of cemented and uncemented fixation between primary and revision THA.

RESULTS

In all acetabular revisions, the use of cemented fixation increased statistically significant with 39% (95% CI, 34-45, p < 0.001) from 23% in primary THA to 62% in revision procedures. In all femoral revisions, the increase of cemented fixation was also statistically significant with 25% (95% CI, 19-31, p < 0.001), from 11% in primary THA to 36% in revision surgery. For both revised acetabular and femoral components, we found no statistically significant difference in the 5-year survival between revision procedures that changed or did not change in method of fixation.

CONCLUSIONS

There was a significant change towards cemented fixation between primary and revision THA in young patients in the Netherlands, which was especially pronounced in acetabular revisions. No significant difference in short-term survival was found between revision procedures that changed or did not change in method of fixation. Long-term follow-up data are needed to evaluate the effect of this change in fixation method on the outcome of revision procedures in young patients.

Identification of implant outliers in joint replacement registries

Recent concerns surrounding joint replacements that have a higher than expected rate of revision have led to stricter controls by regulatory authorities with regards to the introduction of new devices into the marketplace. Implant post-market surveillance remains important, and joint replacement registries are ideally placed to perform this role. This review examined if and how joint replacement registries identified outlier prostheses, outlined problems and suggested solutions to improve post-market surveillance. A search was performed of all joint replacement registries that had electronic or published reports detailing the outcomes of joint replacement. These reports were examined for registry identification of outlier prostheses. Five registries publicly identified outlier prostheses in their reports and the methods by which this was performed, and three others had internal reports. Identification of outlier prostheses is one area that may improve overall joint replacement outcomes; however, further research is needed to determine the optimum methods for identification, including the threshold, the comparator and the numbers required for notification of devices. Co-operation of registries at a global level may lead to earlier identification of devices and thereby further improve the results of joint replacement.

Nationwide partial knee replacement uptake is influenced by volume and supplier--A Dutch arthroplasty register study

BACKGROUND

Despite the established advantages of partial knee replacements (PKR), their usage remains limited. We investigated the effect of hospital knee arthroplasty (KA) volume and the availability of a frequently used PKR by the total KA supplier on the use of PKRs in a hospital.

METHODS

A total of 190,204 total knee replacements (TKR) and 18,134 PKRs were identified in the Dutch Arthroplasty Register (LROI) from 2007 to 2016. For each hospital we determined the annual absolute KA volume (TKR+PKR) into quartiles (<103, 103-197, 197-292, >292 knee replacements/year), and determined whether the TKR supplier provided a frequently used PKR. Hospitals were divided in routine PKR users (≥13 PKRs/year) or occasional/non PKR users (<13 PKRs/year). Based on these parameters, the effect of total KA volume and supplier on PKR usage was investigated, using chi-square tests. Logistic regression analysis was performed to evaluate the influence of the combination of these factors.

RESULTS

In the lowest volume group, around 15% of the hospitals used PKRs, compared to 75% in the highest volume group. Having a TKR supplier that also provides a frequently used PKR resulted in a higher likelihood of performing PKR, especially in low volume hospitals.

CONCLUSIONS

Hospitals' total KA volume and the availability of a frequently used PKR appear to influence the use of PKR.

Mismatch in Capture of Periprosthetic Joint Infections Between the Dutch Arthroplasty Register (LROI) and a Detailed Regional Periprosthetic Joint Infection Registry

BACKGROUND

National arthroplasty registries are important sources for periprosthetic joint infection (PJI) data and report an average incidence ranging from 0.5% to 2.0%. However, studies have shown that PJI incidence in national arthroplasty registries may be underestimated. Therefore, the incidence of PJI in the Dutch Arthroplasty Register (LROI) was evaluated.

METHODS

We matched revisions due to infection within 90 days of index procedure in the LROI database (prospectively registered in 2014-2018) with acute PJI cases registered in a Regional Infection Cohort (RIC) and vice versa. The RIC comprised of 1 university hospital, 3 large orthopedic teaching hospitals and 4 general district hospitals, representing 11.3% of all Dutch arthroplasty procedures with a similar case mix.

RESULTS

From the 352 acute PJIs in the RIC, 166 (47%) were registered in the LROI. Of the 186 confirmed PJI cases not registered in the LROI, 51% (n = 95) were a unregistered Debridement, Antibiotics, and Implant Retention procedure without component exchange. The remaining missing PJI cases (n = 91, 49%) were of administrative origin. The acute PJI incidence in the RIC was 1%, compared to a 0.6% incidence of revision <90 days due to infection from LROI data.

CONCLUSION

Besides unregistered Debridement, Antibiotics, and Implant Retention procedures without component exchange, administrative errors are an important source of missing PJI data for the LROI, leading to underestimation of PJI incidence in the Netherlands. A national arthroplasty complication registry, linked to the LROI, might decrease the number of missing PJI cases. Although our study concerns Dutch data, it supports the scarce literature on PJI incidence obtained from national arthroplasty registries, which also reports an underestimation.

Age-Associated Changes in Proximal Femur Morphology Affect Femoral Component Sizing in Cementless Hip Arthroplasty

Background

In cementless hip arthroplasty, the femoral component should obtain firm fixation within the endosteal bone and achieve adequate reconstruction of hip joint biomechanics simultaneously. Previous anatomical studies described age-related changes of the proximal femoral canal, such as canal widening, which theoretically necessitates the use of larger stem sizes in elderly patients. This study examines a potential association between patients’ age at surgery and the implant size of a cementless femoral component.

Material and methods

A total of 13,423 primary hip arthroplasties with a single cementless stem registered in the Dutch Arthroplasty Register (LROI) were included. Patient characteristics (ie patients’ age, sex, height and weight at time of surgery) and femoral component size were derived. A one-way ANCOVA was used to compare the mean stem size between age groups, and multivariable linear regression analysis was used in order to investigate to which extent ageing impacted stem size.

Results

Each subsequent age- group (ten-year intervals) had a significantly larger mean stem size than the prior age- group. Multivariable linear regression analysis revealed that age is positively correlated with stem size and that this correlation is more prominent in females than in males (beta = .046, P < .001 and beta = .028, P < .001 respectively).

Interpretation

Implant size is positively correlated with age, in particular in females and independently from investigated anthropometric characteristics. The present study endorses that the femoral canal morphology is related to patients’ characteristics such as age and sex. The morphology will subsequently influence implant sizing and therefore may have biomechanical and clinical implications.

Timing of debridement, antibiotics, and implant retention (DAIR) for early post-surgical hip and knee prosthetic joint infection (PJI) does not affect 1-year re-revision rates: data from the Dutch Arthroplasty Register

Debridement, antibiotics, and implant retention (DAIR) is a procedure to treat a periprosthetic joint infection (PJI) after total hip arthroplasty (THA) or total knee arthroplasty (TKA). The timing between the primary procedure and the DAIR is likely a determinant for its successful outcome. However, the optimal timing of a DAIR and the chance of success still remain unclear. We aimed to assess the risk of re-revision within 1 year after a DAIR procedure and to evaluate the timing of the DAIR in primary THA and TKA. We used data from the Dutch Arthroplasty Register (LROI) and selected all primary THA and TKA in the period 2007-2016 which underwent a DAIR within 12 weeks after primary procedure. A DAIR was defined as a revision for infection in which only modular parts were exchanged. A DAIR was defined as successful if not followed by a re-revision within 1 year after DAIR; 207 DAIRs were performed < 4  weeks after THA, of which 16 (8 %) received a complete revision within 1 year. DAIR procedures performed between 4 and 12 weeks ( n = 98 ) had a failure rate of 9 % ( n = 9 ). After TKA 126 DAIRs were performed in less than 4  weeks, of which 11 (9 %) received a complete revision within 1 year; 83 DAIRs were performed between 4 and 12 weeks, of which 14 (17 %) were revised. There was no significant difference in 1-year re-revision rate after a DAIR procedure by timing of the DAIR procedure for total hip and knee arthroplasty based on Dutch registry data.

Which patients improve most after total hip arthroplasty? Influence of patient characteristics on patient-reported outcome measures of 22,357 total hip arthroplasties in the Dutch Arthroplasty Register

BACKGROUND

Patient-reported outcome measures (PROMs) after total hip arthroplasty (THA), can be influenced by patient characteristics (case-mix factors). We used the Dutch Arthroplasty Register (LROI) to determine the effect of case-mix on improvement of PROMs after primary THA.

METHODS

We included all primary THAs (n = 22,357) performed in the Netherlands between 2014 and 2018. The Hip disability and Osteoarthritis Outcome Score Physical function short form (HOOS-PS), Oxford Hip Score (OHS), EQ-5D index score and thermometer, and Numeric Rating Scales (NRS) measuring pain during activities and at rest, were recorded. The difference between preoperative and 3- and 12-month postoperative scores was calculated (delta-PROM) and used as primary outcome variable. Multivariable linear regression was used to examine the association between patient characteristics (age, sex, ASA score, body mass index (BMI), Charnley class, smoking, and previous operations to the affected hip) and PROMs. Cohens' d was used to measure effect size.

RESULTS

Postoperative improvement (delta-PROM) on HOOS-PS, OHS, EQ-5D, and pain relief were significantly higher in patients <60 years, in patients with female gender, a high ASA score (III-IV), a BMI >30 kg/m², and patients without a previous operation to the hip. Cohen's d indicated clinically small differences (0.2).

CONCLUSIONS

Patients benefiting most in terms of postoperative improvement of self-reported physical functioning, pain relief and quality of life after primary THA were young, female, with a high ASA or BMI score, and without previous operations to the hip.

Survival and reasons for revision of the uncemented Symax hip stem: A Dutch Arthroplasty Register study

AIMS

Previous studies have already shown early proximal ingrowth, fast osseous integration, and a stable fit of the uncemented Symax hip stem, with excellent clinical and radiographic performance. Aims were to evaluate cumulative revision rates and reasons for revision of the Symax hip stem using Dutch Arthroplasty Register (LROI) data and to assess possible associations between patient characteristics and revision rate of the Symax hip stem.

PATIENTS AND METHODS

All total hip arthroplasties with the uncemented Symax hip stem registered in the LROI between 2007 and 2017 were included (n = 5,013). Kaplan-Meier survival analysis was performed to assess the cumulative 1, 5 and 7-year revision percentages. Cox proportional hazard regression analysis was performed to assess the association between patient and procedural characteristics, and revision arthroplasty of the stem.

RESULTS

Cumulative 1, 5, and 7-year revision rates (with 95% confidence interval (CI)) for revision of any component were 1.5% (CI 1.2%-1.8%), 3.2% (CI 2.7%-3.7%), and 3.8% (CI 3.1%-4.4%) respectively. Cumulative 1, 5, and 7-year stem revision rates of the Symax hip stem were 0.9% (CI 0.6%-1.1%), 1.5% (CI 1.1%-1.9%), and 1.7% (CI 1.3%-2.1%) respectively. Periprosthetic fractures (n = 35) and loosening of the stem (n = 30) were the most common reasons for revision of the stem. Revision of the stem was associated with acute fracture as primary diagnosis (Hazard Ratio (HR) 2.4 (CI 1.3-4.3)), or history of a previous surgery to the affected hip (HR 2.7 (CI 1.4-5.2)).

CONCLUSION

This population-based registry study shows revision rates for the Symax hip stem comparable to those for best performing uncemented total hip arthroplasties in the Netherlands. Primary diagnosis of an acute fracture, and history of previous surgery on the affected hip, were significantly associated risk factors for revision of the Symax hip stem, and we discourage the use of the Symax hip stem in these patients.

Monitoring Hospital Performance with Statistical Process Control After Total Hip and Knee Arthroplasty: A Study to Determine How Much Earlier Worsening Performance Can Be Detected

BACKGROUND

Given the low early revision rate after total hip arthroplasty (THA) and total knee arthroplasty (TKA), hospital performance is typically compared using 3 years of data. The purpose of this study was to assess how much earlier worsening hospital performance in 1-year revision rates after THA and TKA can be detected.

METHODS

All 86,468 THA and 73,077 TKA procedures performed from 2014 to 2016 and recorded in the Dutch Arthroplasty Register were included. Negative outlier hospitals were identified by significantly higher O/E (observed divided by expected) 1-year revision rates in a funnel plot. Monthly Shewhart p-charts (with 2 and 3-sigma control limits) and cumulative sum (CUSUM) charts (with 3.5 and 5 control limits) were constructed to detect a doubling of revisions (odds ratio of 2), generating a signal when the control limit was reached. The median number of months until generation of a first signal for negative outliers and the number of false signals for non-negative outliers were calculated. Sensitivity, specificity, and accuracy were calculated for all charts and control limit settings using outlier status in the funnel plot as the gold standard.

RESULTS

The funnel plot showed that 13 of 97 hospitals had significantly higher O/E 1-year revision rates and were negative outliers for THA and 7 of 98 hospitals had significantly higher O/E 1-year revision rates and were negative outliers for TKA. The Shewhart p-chart with the 3-sigma control limit generated 68 signals (34 false-positive) for THA and 85 signals (63 false-positive) for TKA. The sensitivity for THA and TKA was 92% and 100%, respectively; the specificity was 69% and 51%, respectively; and the accuracy was 72% and 54%, respectively. The CUSUM chart with a 5 control limit generated 18 signals (1 false-positive) for THA and 7 (1 false-positive) for TKA. The sensitivity was 85% and 71% for THA and TKA, respectively; the specificity was 99% for both; and the accuracy was 97% for both. The Shewhart p-chart with a 3-sigma control limit generated the first signal for negative outliers after a median of 10 months (interquartile range [IQR] = 2 to 18) for THA and 13 months (IQR = 5 to 18) for TKA. The CUSUM chart with a 5 control limit generated the first signal after a median of 18 months (IQR = 7 to 22) for THA and 21 months (IQR = 9 to 25) for TKA.

CONCLUSIONS

Monthly monitoring using CUSUM charts with a 5 control limit enables earlier detection of worsening 1-year revision rates with accuracy so that initiatives to improve care can start earlier.

Mortality and revision rate of cemented and uncemented hemiarthroplasty after hip fracture: an analysis of the Dutch Arthroplasty Register (LROI)

Background and purpose - Femoral neck fractures are commonly treated with cemented or uncemented hemiarthroplasties (HA). We evaluated differences in mortality and revision rates in this fragile patient group.Patients and methods - From January 1, 2007 until December 31, 2016, 22,356 HA procedures from the Dutch Arthroplasty Register (LROI) were included. For each HA, follow-up until death, revision, or end of follow-up (December 31, 2016) was determined. The crude revision rate was determined by competing risk analysis. Multivariable Cox regression analyses were performed to evaluate the effect of fixation method (cemented vs. uncemented) on death or revision. Age, sex, BMI, Orthopaedic Data Evaluation Panel (ODEP) rating, ASA grade, surgical approach, and previous surgery were included as potential confounders.Results - 1-year mortality rates did not differ between cemented and uncemented HA. 9-year mortality rates were 53% (95% CI 52-54) in cemented HA compared to 56% (CI 54-58) in uncemented HA. Multivariable Cox regression analysis showed similar mortality between cemented and uncemented HA (HR 1.0, CI 0.96-1.1). A statistically significantly lower 9-year revision rate of 3.1% (CI 2.7-3.6) in cemented HA compared with 5.1% (CI 4.2-6.2) in the uncemented HA was found with a lower hazard ratio for revision in cemented compared with uncemented HA (HR 0.56, CI 0.47-0.67).Interpretation - Long-term mortality rates did not differ between patients with a cemented or uncemented HA after an acute femoral neck fracture. Revision rates were lower in cemented compared with uncemented HA.

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.

A Comprehensive Evaluation of Lateral Unicompartmental Knee Arthroplasty Short to Mid-Term Survivorship, and the Effect of Patient and Implant Characteristics: An Analysis of Data From the Dutch Arthroplasty Register

BACKGROUND

The rarity of lateral unicompartmental knee arthroplasty (UKA) results in a lack of large cohort studies and understanding. The aim of this study is to comprehensively evaluate survivorship of lateral UKA with registry data and compare this to medial UKA.

METHODS

Lateral (n = 537) and medial UKAs (n = 19,295) in 2007-2017 were selected from the Dutch Arthroplasty Register. Survival analyses were performed with revision for any reason as primary endpoint. Adjustments were made for patient and implant characteristics. Stratified analyses according to patient and implant characteristics were performed. Reasons and type of revision were grouped according to laterality and bearing design.

RESULTS

The 5-year revision rate was 12.9% for lateral UKA and 9.3% for medial UKA. Multivariable regression analyses showed no significant increased risk for revision for lateral UKA (hazard ratio 0.87, 95% confidence interval 0.66-1.15). Stratified analyses showed that the effect of patient characteristics on revision was comparable between lateral and medial UKA; however, the use of mobile-bearing design for lateral UKA was associated with increased revision rate. Progression of osteoarthritis was the main reason for revision on both sides accompanied by tibia component loosening for medial UKA. Reasons and type of revision varied depending on bearing design.

CONCLUSION

Similar survivorship of lateral and medial UKA was reported. Specifically, there is a notable risk for revision when using mobile-bearing designs for lateral UKA. Failure modes and type of revision depends on laterality and bearing design. These findings emphasize that surgical challenges related to anatomy and kinematics of the lateral and medial knee compartment need to be considered.

Between-Hospital Variation in Revision Rates After Total Hip and Knee Arthroplasty in the Netherlands: Directing Quality-Improvement Initiatives

BACKGROUND

Variation in 1-year revision rates between Dutch hospitals after primary total hip and knee arthroplasty (THA and TKA) may direct quality-improvement initiatives if this variation accurately reflects true hospital differences. The aim of the present study was to assess the extent of variation, both overall and for specific indications, as well as the statistical reliability of ranking hospitals.

METHODS

All primary THAs and TKAs that were performed between January 2014 and December 2016 were included. Observed/expected (O/E) ratios regarding 1-year revision rates were depicted in a funnel plot with 95% control limits to identify outliers based on 1 or 3 years of data, both overall and by specific indication for revision. The expected number was calculated on the basis of patient mix with use of logistic regression models. The statistical reliability of ranking hospitals (rankability) on these outcomes indicates the percentage of total variation that is explained by "true" hospital differences rather than chance. Rankability was evaluated using fixed and random effects models, for overall revisions and specific indications for revision, including 1 versus 3 years of data.

RESULTS

The present study included 86,468 THAs and 73,077 TKAs from 97 and 98 hospitals, respectively. Thirteen hospitals performing THAs were identified as negative outliers (median O/E ratio, 1.9; interquartile range [IQR], 1.5-2.5), with 5 hospitals as outliers in multiple years. Eight negative outliers were identified for periprosthetic joint infection; 4, for dislocation; and 2, for prosthesis loosening. Seven hospitals performing TKAs were identified as negative outliers (median O/E ratio, 2.3; IQR, 2.2-2.8), with 2 hospitals as outliers in multiple years. Two negative outlier hospitals were identified for periprosthetic joint infection and 1 was identified for technical failures. The rankability for overall revisions was 62% (moderate) for THA and 46% (low) for TKA.

CONCLUSIONS

There was large between-hospital variation in 1-year revision rates after primary THA and TKA. For most outlier hospitals, a specific indication for revision could be identified as contributing to worse performance, particularly for THA; these findings are starting points for quality-improvement initiatives.

Outcome of revision hip arthroplasty in patients younger than 55 years: an analysis of 1,037 revisions in the Dutch Arthroplasty Register

Background and purpose - The increasing use of hip arthroplasties in young patients will inevitably lead to more revision procedures at younger ages, especially as the outcome of their primary procedures is inferior compared with older patients. However, data on the outcome of revision hip arthroplasty in young patients are limited. We determined the failure rates of revised hip prostheses performed in patients under 55 years using Dutch Arthroplasty Register (LROI) data.Patients and methods - All 1,037 revised hip arthroplasty procedures in patients under 55 years at the moment of revision registered in the LROI during the years 2007-2018 were included. Kaplan-Meier survival analyses were used to calculate failure rates of revised hip arthroplasties with endpoint re-revision for any reason. Competing risk analyses were used to determine the probability of re-revision for the endpoints infection, dislocation, acetabular and femoral loosening, while other reasons for revisions and death were considered as competing risks.Results - Mean follow-up of revision procedures was 3.9 years (0.1-12). 214 re-revisions were registered. The most common reason for the index revision was dislocation (20%); the most common reason for re-revision was infection (35%). The 5-year failure rate of revised hip prostheses was 22% (95% CI 19-25), and the 10-year failure rate was 28% (CI 24-33). The 10-year cumulative failure rates of index revisions with endpoint re-revision for infection was 7.8% (CI 6.1-9.7), acetabular loosening 7.0% (CI 4.1-11), dislocation 3.8% (CI 2.6-5.2), and femoral loosening 2.7% (CI 1.6-4.1). The 10-year implant failure rate of index revisions for infection was 45% (CI 37-55) with endpoint re-revision for any reason.Interpretation - Failure rate of revised hip prostheses in patients under 55 years is worrisome, especially regarding index revisions due to infection. This information facilitates realistic expectations for these young patients at the time of primary THA.

Patient Characteristics Influence Revision Rate of Total Hip Arthroplasty: American Society of Anesthesiologists Score and Body Mass Index Were the Strongest Predictors for Short-Term Revision After Primary Total Hip Arthroplasty

BACKGROUND

Outcome and survival after primary total hip arthroplasty (THA) can be affected by patient characteristics. We examined the effect of case-mix on revision after primary THA using the Dutch Arthroplasty Register.

METHODS

Our cohort included all primary THAs (n = 218,214) performed in patients with osteoarthritis in the Netherlands between 2007 and 2018. Multivariable logistic regression analysis was used to calculate the difference in survivorship in patients with different patient characteristics (age, gender, American Society of Anesthesiologists [ASA] score, body mass index [BMI], Charnley score, smoking, and previous operations to the hip).

RESULTS

Case-mix factors associated with an increased risk for revision 1 year after THA were the following: a high ASA score (II and III-IV) (odds ratio [OR] 1.5, 95% confidence interval [CI] 1.1-2.0 and OR 3.0, 95% CI 1.7-5.3), a higher BMI (30-40 and >40) (OR 1.4, 95% CI 1.2-1.5 and OR 2.0, 95% CI 1.4-1.7), age ≥75 years (OR 1.5, 95% CI 1.1-2.0), and male gender (OR 1.3, 95% CI 1.2-1.4). A similar model for 3-year revision showed comparable results. High BMI (OR 1.9, 95% CI 1.3-2.9), a previous hip operation (OR 1.8, 95% CI 1.3-2.5), ASA III-IV (OR 1.2, 95% CI 1-1.6), and Charnley score C (OR 1.5, 95% CI 1.1-2.2) were associated with increased risk for revision. Main reasons for revision in obese and ASA II-IV patients were infection, dislocation, and periprosthetic fracture. Patients with femoral neck fracture and late post-traumatic pathology were more likely to be revised within 3 years, compared to osteoarthritis patients (OR 1.5, 95% CI 1.3-1.7 and OR 1.5, 95% CI 1.2-1.7).

CONCLUSION

The short-term risk for revision after primary THA is influenced by case-mix factors. ASA score and BMI (especially >40) were the strongest predictors for 1-year revision after primary THA. After 3 years, BMI and previous hip surgery were independent risk factors for revision. This will help surgeons to identify and counsel high-risk patients and take appropriate preventive measures.

Lower 5-year cup re-revision rate for dual mobility cups compared with unipolar cups: report of 15,922 cup revision cases in the Dutch Arthroplasty Register (2007-2016)

Background and purpose - During revision hip arthroplasty the dual mobility cup (DMC) is widely used to prevent dislocation despite limited knowledge of implant longevity. We determined the 5-year cup re-revision rates of DMC compared with unipolar cups (UC) following cup revisions in the Netherlands. Patients and methods - 17,870 cup revisions (index cup revision) were registered in the Dutch Arthroplasty Register during 2007-2016. Due to missing data 1,948 revisions were excluded and the remaining 15,922 were divided into 2 groups: DMC (n = 4,637) and UC (n = 11,285). Crude competing risk and multivariable Cox regression analysis were performed with cup re-revision for any reason as endpoint. Adjustments were made for known patient characteristics. Results - The use of DMC (in index cup revisions) increased from 23% (373/1,606) in 2010 to 47% (791/1,685) in 2016. Patients in the index DMC cup revision group generally had a higher ASA score and the cups were mainly cemented (89%). The main indication for index cup revision was loosening. In the DMC group dislocation was the 2nd main indication for revision. Overall 5-year cup re-revision rate was 3.5% (95% CI 3.0-4.2) for DMC and 6.7% (CI 6.3-7.2) for UC. Cup re-revision for dislocation was more frequent in the UC group compared with the DMC group (32% [261/814] versus 18% [28/152]). Stratified analyses for cup fixation showed a higher cup re-revision rate for UC in both the cemented and uncemented group. Multivariable regression analyses showed a lower risk for cup re-revision for DMC compared with UC (HR 0.5 [CI 0.4-0.6]). Interpretation - The use of DMC in cup revisions increased over time with differences in patient characteristics. The 5-year cup re-revision rates for DMC were statistically significantly lower than for UC.

Generic implant classification enables comparison across implant designs: the Dutch Arthroplasty Register implant library

In the Dutch Arthroplasty Register (LROI), the product and batch number of prosthetic components and cement are registered for traceability. Registration of the product number provides opportunities to extend the information about a specific prosthesis. All product numbers used from the beginning of the registration in 2007 were characterized to develop and maintain an implant library.

The Scientific Advisory Board developed a core-set that contains the most important characteristics needed to form an implant library. The final core-set contains the brand name, type, coating and material of the prosthesis. In total, 35 676 product numbers were classified, resulting in a complete implant library of all product numbers used in the LROI.

To improve quality of the data and increase convenience of registration, the LROI implemented barcode scanning for data entry into the database. In 2017, 82% of prosthetic components and cement stickers had a GS1 barcode. The remaining product stickers used HIBCC barcodes and custom-made barcodes.

With this implant library, implants can be grouped for analyses at group level, e.g. evaluation of the effect of a material of a prosthesis on survival of the implant. Apart from that, the implant library can be used for data quality control within the LROI database.

The implant library reduces the registration burden and increases accuracy of the database. Such a system will facilitate new designs (learning from the past) and thus improve implant quality and ultimately patient safety.

Cite this article: EFORT Open Rev 2019;4 DOI: 10.1302/2058-5241.4.180063

Dual mobility cups in primary total hip arthroplasties: trend over time in use, patient characteristics, and mid-term revision in 3,038 cases in the Dutch Arthroplasty Register (2007-2016)

Background and purpose - We noticed an increased use of dual mobility cups (DMC) in primary total hip arthroplasty (THA) despite limited knowledge of implant longevity. Therefore, we determined the trend over time and mid-term cup revision rates of DMC compared with unipolar cups (UC) in primary THA. Patients and methods - All primary THA registered in the Dutch Arthroplasty Register (LROI) during 2007-2016 were included (n = 215,953) and divided into 2 groups - DMC THA (n = 3,038) and UC THA (n = 212,915). Crude competing risk and multivariable Cox regression analyses were performed with cup revision for any reason as primary endpoint. Adjustments were made for sex, age, diagnosis at primary THA, previous operation, ASA score, type of fixation, surgical approach, and femoral head size. Results - The proportion of primary DMC THA increased from 0.8% (n = 184) in 2010 to 2.6% (n = 740) in 2016. Patients who underwent DMC THA more often had a previous operation on the affected hip, a higher ASA score, and the diagnosis acute fracture or late posttraumatic status compared with the UC THA group. Overall 5-year cup revision rate was 1.5% (95% CI 1.0-2.3) for DMC and 1.4% (CI 1.3-1.4) for UC THA. Stratified analyses for patient characteristics showed no differences in cup revision rates between the 2 groups. Multivariable regression analyses showed no statistically significantly increased risk for revision for DMC THA (HR 0.9 [0.6-1.2]). Interpretation - The use of primary DMC THA increased with differences in patient characteristics. The 5-year cup revision rates for DMC THA and UC THA were comparable.

Total Hip Arthroplasty in Young Patients in The Netherlands: Trend Analysis of >19,000 Primary Hip Replacements in the Dutch Arthroplasty Register

BACKGROUND

Total hip arthroplasty (THA) is one of the most successful interventions in medical care. Because of shifting trends in THA and failure rates being higher in younger patients, we aimed to assess trends in implant fixation, bearing type, head diameter, and surgical approach in patients younger than 55 years in the Netherlands using data from the Dutch Arthroplasty Register.

METHODS

Trends in the method of implant fixation, bearing type, head diameter, and surgical approach were analyzed over year of surgery (2007-2016) and over age groups (<25, 25-29, 30-34, 35-39, 40-44, 45-49, and 50-54 years).

RESULTS

Between 2007 and 2016, a total of 19,915 primary THAs were performed in patients <55 years. Osteoarthritis was the most prevalent diagnosis (66.1%). Uncemented fixation was used in 79.5% of all performed THAs. The use of 32-mm head diameters increased (from 32.6% in 2007 to 50.1% in 2016), where an increasing trend toward the use of ceramic-on-polyethylene as most frequently used bearing type was present (from 37.5% in 2007 to 53.8% in 2016). The posterolateral surgical approach was the most frequently used approach; however, the anterior approach is used increasingly (0.1% in 2007 to 21.1% in 2016). Ceramic-on-polyethylene bearing surfaces, 32-mm head diameters, and the anterior approach were most commonly used in patients between 50 and 54 years.

CONCLUSION

There was a clear preference for uncemented fixation in young patients. In head diameter, bearing type, and surgical approach, clear trends were visible. Characteristics of THA in young patients were subject to changing perspectives.

Nationwide review of mixed and non-mixed components from different manufacturers in total hip arthroplasty

Background and purpose - Combining components from different manufacturers in total hip arthroplasty (THA) is common practice worldwide. We determined the proportion of THAs used in the Netherlands that consist of components from different manufacturers, and compared the revision rates of these mixed THAs with those of non-mixed THAs. Patients and methods - Data on primary and revision hip arthroplasty are recorded in the LROI, the nationwide population-based arthroplasty register in the Netherlands. We selected all 163,360 primary THAs that were performed in the period 2007-2014. Based on the manufacturers of the components, 4 groups were discerned: non-mixed THAs with components from the same manufacturer (n = 142,964); mixed stem-head THAs with different manufacturers for the femoral stem and head (n = 3,663); mixed head-cup THAs with different head and cup manufacturers (n = 12,960), and mixed stem-head-cup THAs with different femoral stem, head, and cup manufacturers (n = 1,773). Mixed prostheses were defined as THAs (stem, head, and cup) composed of components made by different manufacturers. Results - 11% of THAs had mixed components (n = 18,396). The 6-year revision rates were similar for mixed and non-mixed THAs: 3.4% (95% CI: 3.1w-3.7) for mixed THAs and 3.5% (95% CI: 3.4-3.7) for non-mixed THAs. Revision of primary THAs due to loosening of the acetabulum was more common in mixed THAs (16% vs. 12%). Interpretation - Over an 8-year period in the Netherlands, 11% of THAs had mixed components-with similar medium-term revision rates to those of non-mixed THAs.

More than 95% completeness of reported procedures in the population-based Dutch Arthroplasty Register

BACKGROUND AND PURPOSE

A complete and correct national arthroplasty register is indispensable for the quality of arthroplasty outcome studies. We evaluated the coverage, completeness, and validity of the Dutch Arthroplasty Register (LROI) for hip and knee arthroplasty.

PATIENTS AND METHODS

The LROI is a nationwide population-based registry with information on joint arthroplasties in the Netherlands. Completeness of entered procedures was validated in 2 ways: (1) by comparison with the number of reimbursements for arthroplasty surgeries (Vektis database), and (2) by comparison with data from hospital information systems (HISs). The validity was examined by conducting checks on missing or incorrectly coded values in the LROI.

RESULTS

The LROI contains over 300,000 hip and knee arthroplasties performed since 2007. Coverage of all Dutch hospitals (n = 100) was reached in 2012. Completeness of registered procedures was 98% for hip arthroplasty and 96% for knee arthroplasty in 2012, based on Vektis data. Based on comparison with data from the HIS, completeness of registered procedures was 97% for primary total hip arthroplasty and 96% for primary knee arthroplasty in 2013. Completeness of revision arthroplasty was 88% for hips and 90% for knees in 2013. The proportion of missing or incorrectly coded values of variables was generally less than 0.5%, except for encrypted personal identity numbers (17% of which were missing) and ASA scores (10% of which were missing).

INTERPRETATION

The LROI now contains over 300,000 hip and knee arthroplasty procedures, with coverage of all hospitals. It has a good level of completeness (i.e. more than 95% for primary hip and knee arthroplasty procedures in 2012 and 2013) and the database has high validity.

[Evidence-based hip prostheses: more high-quality prostheses used after introduction of a classification system]

OBJECTIVE

To determine the effect of an evidence-based classification list on use of total hip prostheses of proven quality in the Netherlands.

DESIGN

Observational study.

METHOD

The Netherlands Orthopaedic Association (NOV) drew up a classification list for total hip prostheses in 2013. This classification list considered total hip prostheses to be of proven quality when the average percent of revision was ≤ 10% after 10 years of follow-up (category 1A) or ≤ 5% after 5 years of follow-up (category 1B). Data from the Dutch National Orthopaedic Implant Registry Register (LROI) were used to determine the effect of the classification list on the use of hip prostheses of proven quality in the Netherlands. All patients, operations and prosthesis characteristics of the hip prostheses used in the Netherlands were registered in the LROI. We selected details of all interventions in which a hip prosthesis was implanted in patients with 'osteoarthritis' as primary diagnosis between 2012 and 2014 from the LROI. The prostheses could be classified as 1A, 1B or 'not 1A or 1B' by means of the implant code of the acetabular and femoral components. We took 2012 as the reference year.

RESULTS

In the reference year, 84% of the acetabular components and 94% of the femoral components were category 1A or 1B. In 2013 these percentages had increased to 89% and 95%, respectively; in 2014 the percentages had increased to 92% and 97%.

CONCLUSION

After implementation of the NOV classification list there was an increase in the percentage of total hip prostheses of proven quality, which means that patient care has become better and safer.

Conditional survival of malignant melanoma in The Netherlands: 1994-2008

BACKGROUND

Cutaneous malignant melanoma causes the majority of skin cancer related deaths and features increasing incidence and mortality rates in the Netherlands. Conditional survival analysis is performed on patients who survived the preceding year(s).

METHODS

Patients with invasive melanoma, as recorded in the population-based Netherlands Cancer Registry, were included. To assess prognosis of melanoma survivors according to gender and Breslow thickness, conditional five-year relative survival was calculated for lymph node negative melanoma patients and conditional one-year relative survival was analysed for melanoma patients with and without nodal involvement.

FINDINGS

Between 1994 and 2008, 40,050 patients developed a melanoma (stage I-III, of whom 6% with nodal involvement). Six to 8years after diagnosis, survival of patients with a 1-2mm (T2) thick melanoma equalised the general population. Conditional five-year relative survival for patients with >4mm thick (T4) melanomas increased from about 60% at diagnosis to 90% at 7years after diagnosis. Largest improvements were found in patients with thick melanomas and female patients with nodal involvement.

INTERPRETATION

The prognosis for melanoma survivors improved with each additional year of survival after diagnosis, except for patients with a ⩽1mm thick melanoma, who never had any excess mortality during follow-up. Conditional survival of melanoma was better amongst females, amongst those with lower Breslow thickness and nodal stage.

Treatment and outcome of young patients with esophageal cancer in the Netherlands

BACKGROUND

Esophageal cancer is increasingly recognized in younger patients. We compared clinicopathological characteristics, treatment, and survival of patients aged ≤50 years with patients aged >50 years diagnosed with esophageal cancer in the Netherlands.

METHODS

From the nationwide Netherlands Cancer Registry we identified all patients diagnosed with esophageal cancer between January 2000 and January 2011. Proportions were compared using the χ(2) test for categorical variables. Overall and relative survival was calculated.

RESULTS

Eleven percent of the patients (n = 1,466) were aged ≤50 years and adenocarcinoma was the most common tumor type (73.6%). Grade of tumor differentiation was comparable between both age groups (P = 0.460) as well as T-stage (P = 0.058). Younger patients presented more often with positive lymph nodes (70.1% vs. 66.4%, P = 0.010) and distant metastasis (50.5% vs. 44.7%, P < 0.001) but had surgery more often as compared to older patients: 40.6% versus 37.9%, P = 0.047. There was no significant difference in the 5-year relative survival between both age groups: 18.1% versus 17.2%, P > 0.05. A subgroup analysis among patients diagnosed with adenocarcinoma revealed similar results.

CONCLUSIONS

Young patients with esophageal cancer present with more advanced disease stage and received more often treatment. However, they show comparable relative survival rates with their older counterparts.

The lymph node ratio as a prognostic factor for gastric cancer

To predict prognosis of gastric cancer, an adequate assessment of the stage of gastric cancer is important. The UICC/AJCC TNM classification is the most commonly used classification system. For adequate N staging at least 15 lymph nodes should be retrieved. In some countries, this amount of lymph nodes is not met, which can lead to understaging. Therefore, the lymph node ratio (LNR) is proposed as an alternative N staging modality. The purpose of this study was to compare the different staging modalities. Patients and methods. We included all patients who underwent surgery for gastric cancer, newly diagnosed between 2000 and 2009 and staged patient by UICC/AJCC TNM 5th/6th or 7th and by LNR. We conducted crude survival analysis, univariate and multivariate analyses according to the different staging systems. Results. The five-year overall survival rates ranged from 58% for N0 disease to 18% in case of more than 15 metastatic lymph nodes. The distribution of overall five-year survival according to LNR was 58% for LNR0 and 10% for LNR3. Univariate analysis showed that all the UICC/AJCC TNM classification systems as well as the LNR were strong prognostic factors for overall survival. The LNR correlated less with the number of nodes examined. Conclusion. LNR is a good prognostic tool for overall survival, it is an independent prognostic factor with a more homogenous spread of hazard ratios and five-year survival rates than UICC/AJCC systems. Furthermore, the LNR has a lower correlation with the number of nodes examined, making it less vulnerable for stage migration.

Impact of the transition from screen-film to digital screening mammography on interval cancer characteristics and treatment - a population based study from the Netherlands

INTRODUCTION

In most breast screening programmes screen-film mammography (SFM) has been replaced by full-field digital mammography (FFDM). We compared interval cancer characteristics at SFM and FFDM screening mammography.

PATIENTS AND METHODS

We included all 297 screen-detected and 104 interval cancers in 60,770 SFM examinations and 427 screen-detected and 124 interval cancers in 63,182 FFDM examinations, in women screened in the period 2008-2010. Breast imaging reports, biopsy results and surgical reports of all cancers were collected. Two radiologists reviewed prior and diagnostic mammograms of all interval cancers. They determined breast density, described mammographic abnormalities and classified interval cancers as missed, showing a minimal sign abnormality or true negative.

RESULTS

The referral rate and cancer detection at SFM were 1.5% and 4.9‰ respectively, compared to 3.0% (p<0.001) and 6.6‰ (p<0.001) at FFDM. Screening sensitivity was 74.1% at SFM (297/401, 95% confidence interval (CI)=69.8-78.4%) and 77.5% at FFDM (427/551, 95% CI=74.0-81.0%). Significantly more interval cancers were true negative at prior FFDM than at prior SFM screening mammography (65.3% (81/124) versus 47.1% (49/104), p=0.02). For interval cancers following SFM or FFDM screening mammography, no significant differences were observed in breast density or mammographic abnormalities at the prior screen, tumour size, lymph node status, receptor status, Nottingham tumour grade or surgical treatment (mastectomy versus breast conserving therapy).

CONCLUSION

FFDM resulted in a significantly higher cancer detection rate, but sensitivity was similar for SFM and FFDM. Interval cancers are more likely to be true negative at prior FFDM than at prior SFM screening mammography, whereas their tumour characteristics and type of surgical treatment are comparable.

Actual prognosis during follow-up of survivors of B-cell non-Hodgkin lymphoma in the Netherlands

Survival rates determined at diagnosis are often too negative for cancer survivors. Conditional relative survival reflects actual prognosis during follow-up better. Data from all 54,015 patients newly diagnosed in the Netherlands with B-cell non-Hodgkin lymphoma during 1989-2008, aged 15-89 years (Netherlands Cancer Registry), were used. Five-year conditional relative survival was computed for every additional year of survival up to 16 years after diagnosis, according to entity, grade, gender, age, and Ann Arbor stage. The prognosis for survivors of indolent B-cell non-Hodgkin lymphoma improved slightly with each additional year survived up to 91%. For patients with aggressive non-Hodgkin lymphoma conditional relative survival improved strongly during the first year after diagnosis (from 48% to 68%) and gradually thereafter to 93% after 16 years. There were differences between morphological entities. Initial differences in conditional relative survival at diagnosis between groups with different disease stages became smaller with increasing number of years survived. Age remained a prognostic indicator, also after prolonged follow-up. These results help caregivers to plan optimal surveillance and inform patients about their actual prognosis during follow-up. Long-lasting excess mortality among patients with B-cell non-Hodgkin lymphoma indicates the need for additional care long after their diagnosis.

Rising incidence, no change in survival and decreasing mortality from thyroid cancer in The Netherlands since 1989

The incidence of thyroid cancer (TC) is increasing worldwide, partly due to increased detection. We therefore assessed combined trends in incidence, survival and mortality of the various types of TC in The Netherlands between 1989 and 2009. We included all patients ≥15 years with TC, diagnosed in the period 1989-2009 and recorded in The Netherlands Cancer Registry (n=8021). Information on age, gender, date of diagnosis, histological type of tumour and tumour-node-metastasis classification was recorded. Mortality data (up to 1st January 2010) were derived from Statistics Netherlands. Annual percentages of change in incidence, mortality and relative survival were calculated. Since 1989 the incidence of TC increased significantly in The Netherlands (estimated annual percentage change (EAPC)=+1.7%). The incidence rates increased for all age groups (except for females >60 years), papillary tumours (EAPC=+3.5%), T1 and T3 TC (EAPC=+7.9 and +5.8% respectively). Incidence rates decreased for T4 TC (-2.3%) and remained stable for follicular, medullary anaplastic and T2 TC. Five-year relative survival rates remained stable for papillary (88%) and follicular (77%) TC, all age groups and T1-T3 TC (96, 94 and 80% respectively) and somewhat lower for T4 (53%), medullary (65%) and anaplastic TC (5%) in the 2004-2009 period compared with earlier periods. Mortality due to TC decreased (EAPC=-1.9%). TC detection and incidence has been rising in The Netherlands, while mortality rates are decreasing and survival rates remained stable or slightly decreasing.

Survival of MUTYH-associated polyposis patients with colorectal cancer and matched control colorectal cancer patients

BACKGROUND

MUTYH-associated polyposis is a recessively inherited disorder characterized by a lifetime risk of colorectal cancer that is up to 100%. Because specific histological and molecular genetic features of MUTYH-associated polyposis colorectal cancers might influence tumor behavior and patient survival, we compared survival between patients with MUTYH-associated polyposis colorectal cancer and matched control patients with colorectal cancer from the general population.

METHODS

In this retrospective multicenter cohort study from Europe, 147 patients with MUTYH-associated polyposis colorectal cancer were compared with 272 population-based control patients with colorectal cancer who were matched for country, age at diagnosis, year of diagnosis, stage, and subsite of colorectal cancer. Kaplan-Meier survival and Cox regression analyses were used to compare survival between patients with MUTYH-associated polyposis colorectal cancer and control patients with colorectal cancer. All statistical tests were two-sided.

RESULTS

Five-year survival for patients with MUTYH-associated polyposis colorectal cancer was 78% (95% confidence interval [CI] = 70% to 84%) and for control patients was 63% (95% CI = 56% to 69%) (log-rank test, P = .002). After adjustment for differences in age, stage, sex, subsite, country, and year of diagnosis, survival remained better for MUTYH-associated polyposis colorectal cancer patients than for control patients (hazard ratio of death = 0.48, 95% CI = 0.32 to 0.72).

CONCLUSIONS

In a European study cohort, we found statistically significantly better survival for patients with MUTYH-associated polyposis colorectal cancer than for matched control patients with colorectal cancer.