Impact of hip arthroplasty registers on orthopaedic practice and perspectives for the future

Do all short stem types restore biomechanical parameters of the hip? Comparison according to femoral neck osteotomy levels

PURPOSE

There is no consensus on ideal short femoral stem design. A classification system proposed by Feyen and Shimmin divides short stems in two types according to femoral neck osteotomy levels: subcapital (IIIA) and standard (IIIB). The study aims to determine which design type is more successful in restoring native biomechanical parameters and whether stem type has an impact on clinical results.

METHODS

In this retrospective comparative study, patients that have undergone short stem hip arthroplasty were evaluated according to stem types: type IIIA (n = 52, 66.7%) (Mathys Optimys) and IIIB (n = 26, 33.3%) (Implantcast Aida and Smith & Nephew SMF). Pelvis X-rays were assessed in terms of femoral neck length, horizontal and vertical hip centres of rotation, horizontal and vertical femoral offsets, abductor lever arm lengths, leg lengths, and stem-shaft angles. Improvement in Harris hip scores, differences between post-operative and pre-operative measurements, and stem-shaft angles were evaluated and compared between two groups.

RESULTS

Mean femoral neck resection (8.27 ± 6.68 mm in IIIA and 15 ± 6.33 mm in IIIB) was significantly different between both groups (p < 0.001). Harris hip scores were increased at post-operative six months in both groups with no difference (84.4 ± 6.4 and 84.6 ± 5.5, p = 0.4). The absolute values of differences between pre-operative and post-operative horizontal centres of rotation (p = 0.63), vertical centers of rotation (p = 0.75), horizontal femoral offsets (p = 0.78), vertical femoral offsets (p = 0.83), abductor lever arm distances (p = 0.63), and leg length (p = 0.21) measurements were not different between both groups. Stem positions were both varus with no statistically significant difference between groups (p = 0.14).

CONCLUSION

We found no difference regarding restoration of biomechanical parameters between short stem designs with different levels of neck osteotomy. Additionally, short stem can mostly result in varus component positioning regardless of the level of neck osteotomy.

Over a decade of experience in total knee arthroplasty with a multiradius design and fixed bearing at a single centre: Data from the Catalan Arthroplasty Registry

Purpose

Arthroplasty registers can provide feedback information on the results of arthroplasties performed by a certain institution or surgeon. The use of real-world data to achieve real-world evidence can help evaluate the performance of the implants used and help counsel our patients. The main objective of our study was to determine the survivorship of the total knee implant we are currently using.

Methods

A retrospective cohort study of patients who received a total knee arthroplasty from January 2009 to December 2020 in our hospital was conducted, using data from the Catalan arthroplasty registry and the Catalan health service database. Demographic and surgical data were analysed using the Kaplan-Meier method, log-rank test and Cox proportional hazards models with the R Project software (p < 0.05).

Results

A total of 1336 total knee arthroplasties were included in the study, of which 992 were women. The causes for revision included aseptic loosening (17), infection (29), instability (13), patellar implantation (13), arthrofibrosis (5) and quadriceps tendon rupture (1).The cumulative risk for revision at 5 years using the Kaplan-Meier method was 6.0% and at 10 years 6.5%. Considering gender, this risk was 7.0% and 7.5% at 5 and 10 years, respectively, in women and 3.3% in men, both at 5 and 10 years (p = 0.009). A higher risk for revision in women was seen, which is considered statistically significant (p = 0.012).

Conclusion

Our survivorship results are comparable to those published in the literature, but with a higher revision risk in women that is only statistically significant for the whole group of reoperations and for patellar implantation, but not for the rest of the diagnoses.

Level of Evidence

Level IV.

Improvements in Quality, Safety and Costs Associated with Use of Implant Registries Within a Health System

BACKGROUND

Clinical quality registries (CQRs) are intended to enhance quality, safety, and cost reduction using real-world data for a self-improving health system. Starting in 2001, Kaiser Permanente established several medical device CQRs as a quality improvement initiative. This report examines the contributions of these CQRs on improvement in health outcomes, changes in clinical practice, and cost-effectiveness over the past 20 years.

METHODS

Eight implant registries were instituted with standardized collection from the electronic health record and other institutional data sources of patient characteristics, medical comorbidities, implant attributes, procedure details, surgical techniques, and outcomes (including complications, revisions, reoperations, hospital readmissions, and other utilization measures). A rigorous quality control system is in place to improve and maintain the quality of data. Data from the Implant Registries form the basis for multiple quality improvement and patient safety initiatives to minimize variation in care, promote clinical best practices, facilitate recalls, perform benchmarking, identify patients at risk, and construct reports about individual surgeons.

RESULTS

Following the inception of the Implant Registries, there was an observed (1) reduction in opioid utilization following orthopedic procedures, (2) reduction in use of bone morphogenic protein during lumbar fusion allowing for cost savings, (3) reduction in allograft for anterior cruciate ligament reconstruction and subsequent decrease in organizationwide revision rates, (4) cost savings through expansion of same-day discharge programs for joint arthroplasty, (5) increase in the use of cement fixation in the hemiarthroplasty treatment of hip fracture, and (6) organizationwide discontinuation of an endograft device associated with a higher risk for adverse outcomes following endovascular aortic aneurysm repair.

CONCLUSION

The use of Implant Registries within our health system, along with clinical leadership and organizational commitment to a learning health system, was associated with improved quality and safety outcomes and reduced costs. The exact mechanisms by which such registries affect health outcomes and costs require further study.

Enhancing the data capture of periprosthetic joint infections in the Danish Knee Arthroplasty Registry: validity assessment and incidence estimation

BACKGROUND AND PURPOSE

Revisions due to periprosthetic joint infection (PJI) are underestimated in national arthroplasty registries. Our primary objective was to assess the validity in the Danish Knee Arthroplasty Register (DKR) of revisions performed due to PJI against the Healthcare-Associated Infections Database (HAIBA). The secondary aim was to describe the cumulative incidences of revision due to PJI within 1 year of primary total knee arthroplasty (TKA) according to the DKR, HAIBA, and DKR/HAIBA combined.

METHODS

This longitudinal observational cohort study included 56,305 primary TKAs (2010-2018), reported in both the DKR and HAIBA. In the DKR, revision performed due to PJI was based on pre- and intraoperative assessment disclosed by the surgeon immediately after surgery. In HAIBA, PJI was identified from knee-related revision procedures coinciding with 2 biopsies with identical microbiological pathogens. We calculated the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of revision due to PJI in the DKR (vs. HAIBA, within 1 year of TKA) with 95% confidence intervals (CI). Cumulative incidences were calculated using the Kaplan-Meier method.

RESULTS

The DKR's sensitivity for PJI revision was 58% (CI 53-62) and varied by TKA year (41%-68%) and prosthetic type (31% for monoblock; 63% for modular). The specificity was 99.8% (CI 99.7-99.8), PPV 64% (CI 62-72), and NPV 99.6% (CI 99.6-99.7). 80% of PJI cases not captured by the DKR were caused by non-reporting rather than misclassification. 33% of PJI cases in the DKR or HAIBA were culture-negative. Considering potential misclassifications, the best-case sensitivity was 64%. The cumulative incidences of PJI were 0.8% in the DKR, 0.9% in HAIBA, and 1.1% when combining data.

CONCLUSION

The sensitivity of revision due to PJI in the DKR was 58%. The cumulative incidence of PJI within 1 year after TKA was highest (1.1%) when combining the DKR and HAIBA, showing that incorporating microbiology data into arthroplasty registries can enhance PJI validity.

Intracardiac leakage of cement during artificial femoral head replacement: a case report and review

Bone cement leakage from the femoral medullary cavity is a rare complication following hip replacement. Currently, there are no reports of bone cement leakage into the heart. Here, we report an 81-year-old female patient with right femoral neck fracture. A thorough preoperative examination showed that bone cement had leaked into the heart during right femoral head replacement, leading to the death of the patient that night. Postoperative cardiac ultrasound showed that bone cement entered the vascular system through the femoral medullary cavity and subsequently entered the heart. Extreme deterioration in the patient's condition resulted in death that night. Unfortunately, the patient's family abandoned the idea of surgical removal of foreign bodies, leading to inevitable death. This case emphasizes the risk of clinical manifestations of cardiac embolism of bone cement after artificial femoral head replacement, suggesting that the risk of such embolism might be underestimated. We propose routine real-time C-arm X-ray guidance and injection of an appropriate amount of bone cement to prevent serious cardiopulmonary failure.

Initial experience with Bulgarian Arthroplasty Register

INTRODUCTION

National arthroplasty registries date back to 1975, when the Swedish Knee Arthroplasty Register was founded. This method of database collecting has since been employed for both patient follow-up and the creation of annual statistical reports. In Bulgaria, there is currently no state-approved software that offers these features.

Do 'Surgeon Champions' and High-Volume Surgeons Have Lower Rates of Periprosthetic Femur Fracture? Perspective from a State-wide Quality Improvement Registry

BACKGROUND

Recently, a state-wide registry identified fracture as a major cause of total hip arthroplasty revision. There were 52.8% of revisions occurring within 6 months (fracture leading cause). Registry sites have a 'Surgeon Champion' who acts as liaison and advocate. This study evaluated the effect of surgeon volume and role of 'surgeon champion' on fracture rates.

METHODS

There were 95,948 cases from 2012 to 2019 queried with peri-implant femoral fractures identified (within 6 months). Funnel plots were generated to compare individual surgeon-specific fracture rates. Surgeons who had a fracture rate below the confidence interval were labeled 'green' (lower than mean), within were 'yellow' (no difference), and above were 'red' (significantly higher).

RESULTS

For all surgeons, 19.6% were red, 72.1% yellow, and 8.3% green. There were 17.2% 'Surgeon Champions' and 6.2% 'Non-Champions' that were green (P=0.01), while 20.7 and 19.3% were red (P=0.82). There was a significant association between volume and performance (P<0.01). No surgeons in the lower two quartiles (<84; 84 to 180 cases), while 4 and 29% of higher-volume surgeons (181 to 404; >404 cases) were green. There was no statistical difference in red status by volume (P=0.53).

CONCLUSION

'Surgeon champions' and high-volume surgeons were more likely to be high performers, but not less-likely to be low performers. Active involvement in quality improvement and/or high-volume was associated with better outcomes, but did not impart complication immunity. 'Green' surgeons should mentor colleagues to help reduce fractures by re-evaluating modifiable factors. Analyzing outcomes to promote quality and decrease complications is paramount.

National Joint Registry recorded untoward intraoperative events during primary total hip arthroplasty: an investigation into the data accuracy, causal mechanisms and attributability

INTRODUCTION

Untoward intraoperative events occurring during total hip arthroplasty are recorded by the National Joint Registry through Minimum Data Set (MDS) forms. This data may be used to assess the safety of implants. The aim of this study is to evaluate the accuracy of the untoward intraoperative events, assess the mechanism and ascertain whether these events were attributable to the implants inserted.

METHODS

A retrospective analysis was undertaken of primary total hip arthroplasties performed between 2005 and 2018 in which an untoward intraoperative event was recorded.

RESULTS

Of 12,802 primary hip replacements, 64 patients (0.5%) had untoward intraoperative events recorded on the MDS form. In 43 of 64 cases, the intraoperative untoward event recorded on the MDS form matched the operation notes. Among these 43 cases, in 30 (69%) patients the intraoperative event could be attributed to the implant recorded. In the remaining 13 (31%) cases, the events recorded could not be attributed to the implant. In six cases, the untoward events were attributed to implants used to manage the events rather than the implants which caused them. In seven cases, the untoward events were related to surgical technique rather than to the implant or instrumentation.

CONCLUSIONS

Our analysis highlights that all untoward intraoperative events recorded on the NJR form are not implant related or attributable to the implant inserted. Provision should be made on the MDS form to clarify whether a particular untoward intraoperative event was related to the implant inserted.

The ethylene oxide sterilised Opera acetabular component demonstrates high rates of loosening and revision compared to the gamma irradiated Ogee cup: a cohort study demonstrating potential shortcomings of revision-based registry data

AIMS

To evaluate the long-term clinical outcomes of 2 cemented ultra-high molecular weight polyethylene (UHMWPE) acetabular components, with the main difference between the 2 components being their method of sterilisation.

PATIENTS AND METHODS

Data was collected prospectively on 352 consecutive total hip replacements, performed between March 2000 and July 2004, at a single centre. A posterior approach was used with a cemented C-Stem femoral component (DePuy, Warsaw, IN, USA) in all cases and either the Ogee (DePuy, Warsaw, IN, USA) or the Opera (Smith & Nephew, Memphis, TN, USA) acetabular implant. Patients were reviewed clinically and radiologically with a median 12-year follow-up (6-16 years).

RESULTS

The risk of experiencing loosening was 90% lower for the Gamma irradiated implant (GII) group compared to the ethylene oxide sterilised implant (EOSI) group, which was statistically significant (p = 0.003), (HR 0.10; 95% CI, 0.02-0.45). The incidence of cup revision was also lower in the GII group (p = 0.029), but after adjustment for age, gender and BMI was not statistically significant (p = 0.104). 15-year survivorship with failure/loosening as an endpoint was 70.1% for the EOS implant and 92.9% for the GII (OR 4.99; CI 95%, 1.75-14.2) and with revision as an endpoint was 81.4% for the EOSI and 92.9% for the GII (OR 2.60; CI 95%, 0.87-7.75).

CONCLUSIONS

We report increased rates of loosening, revision and failure for the EOSI compared to the GII at long-term follow-up. This may have been attributable to the different sterilisation methods used.

International Registries: U.K. National Joint Registry, Nordic Registries, and Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR)

National-level joint arthroplasty registries were among the first large orthopaedic surgery databases and represent some of the longest-running and most influential big databases in our profession. Nordic registries were among the first registries and were followed by excellent registries in the United Kingdom and Australia. In this article, we describe each of these registries and highlight the data elements collected, the data points that can be obtained by linking the national arthroplasty registries to other national registries or databases, the completeness of data, and the strengths and weaknesses of each database. Each of these registries publishes an annual report that is available online, and each also can do more detailed analysis of certain aspects of its data for special studies.When evaluating and interpreting data from national joint registries, the user should be aware that, despite the power of huge numbers, there remain numerous limitations to the observational data. Strong selection biases exist with regard to which patients are chosen for which procedure. Surgeons of different skill levels may use one technique or implant differentially compared with another. The end points that registries collect differ widely: for example, some report only hip dislocations leading to revision rather than all dislocations. Registries in countries in which there are long wait times for revision surgery may report artificially low revision rates compared with countries in which revision surgery is more easily accessible. Despite these limitations, registries have the merit of reporting the actual results of huge numbers of surgical procedures performed across the spectrum of hospitals, surgeons, and patients, making the data extremely powerful for identifying trends, identifying early signs of problems related to certain implants or implant classes, and identifying associations between variables that can be further studied to determine if the effect is causal.

Cutting-Edge Approaches in Arthroplasty: Before, during and after Surgery

Personalised medicine was introduced in arthroplasty a long time ago with the aim of respecting each individual person for their unique personal characteristics in order to further improve outcomes [...].

Knee registries: state of the art

Sports injuries, trauma and the globally ageing and obese population require increasing levels of knee surgery. Shared decision making has replaced the paternalistic approach to patient management. Evidence-based medicine underpins surgical treatment strategies, from consenting an individual patient to national healthcare system design. The evolution of successful knee-related registries starting from specific arthroplasty registries has given rise to ligament reconstruction, osteotomy and cartilage surgery registries developing as platforms for surgical outcome data collection. Stakeholders include surgeons and their patients, researchers, healthcare systems, as well as the funding insurers and governments. Lately, implant manufacturers have also been mandated to perform postmarket surveillance with some hoping to base that on registry data. Aiming to assess the current status of knee-related registries, we performed a comprehensive literature and web search, which yielded 23 arthroplasty, 8 ligament, 4 osteotomy and 3 articular cartilage registries. Registries were evaluated for their scope, measured variables, impact and limitations. Registries have many advantages as they aim to increase awareness of outcomes; identify trends in practice over time, early failing implants, outlier surgeon or institution performance; and assist postmarketing surveillance. International collaborations have highlighted variations in practice. The limitations of registries are discussed in detail. Inconsistencies are found in collected data and measured variables. Potential measurement and selection biases are outlined. Without mandated data collection and with apparent issues such as unverified patient reporting of complications, registries are not designed to replace adverse event recording in place of a proper safety and efficacy study, as demanded by regulators. Registry 'big data' can provide evidence of associations of problems. However, registries cannot provide evidence of causation. Hence, without careful consideration of the data and its limitations, registry data are at risk of incorrectly drawn conclusions and the potential of misuse of the results. That must be guarded against. Looking at the future, registry operators benefit from a collective experience of running registries as they mature, allowing for improvements across specialties. Large-scale registries are not only of merit, improving with stakeholder acceptance, but also are critical in furthering our understanding of our patients' outcomes. In doing so, they are a critical element for our future scientific discourse.

Causes of Early Hip Revision Vary by Age and Gender: Analysis of Data From a Statewide Quality Registry

BACKGROUND

While total hip arthroplasty (THA) is extremely successful, early failures do occur. The purpose of this study was to determine the cause of revision in specific patient demographic groups at 3 time points to potentially help decrease the revision risk.

METHODS

Data for cases performed between 2012 and 2018 from a statewide, quality improvement arthroplasty registry were used. The database included 79,205 THA cases and 1,433 revisions with identified etiology (1,584 in total). All revisions performed at <5 years from the primary THA were reviewed. Six groups, men/women, <65, 65-75, and >75 years, were compared at revision time points <6 months, <1 year, and <5 years.

RESULTS

There were obvious and significant differences between subgroups based on demographics and time points (P < .0001). Seven hundred and fifty-six (53%) of all revisions occurred within 6 months. The most common etiologies within 6 months (756 revisions) were fracture (316, 41.8%), dislocation/instability (194, 25.7%), and infection (98, 12.9%). At this early time point, the most common revision cause was fracture for all age/gender-stratified groups, ranging from 27.6% in young men to 60% in older women. Joint instability became the leading cause for revision after 1 year in all groups.

CONCLUSION

This quality improvement project demonstrated clinically meaningful differences in the reason for THA revision between gender, age, and time from surgery. Strategies based on these data should be employed by surgeons to minimize the factors that lead to revision.

Risk of revision arthroplasty surgery after exposure to physically demanding occupational or leisure activities: A systematic review

INTRODUCTION

Lower limb arthroplasty is successful at relieving symptoms associated with joint failure. However, physically-demanding activities can cause primary osteoarthritis and accordingly such exposure post-operatively might increase the risk of prosthetic failure. Therefore, we systematically reviewed the literature to investigate whether there was any evidence of increased risk of revision arthroplasty after exposure to intensive, physically-demanding activities at work or during leisure-time.

METHODS

We searched Medline, Embase and Scopus databases (1985-July 2021) for original studies including primary lower limb arthroplasty recipients that gathered information on physically-demanding occupational and/or leisure activities and rates of revision arthroplasty. Methodological assessment was performed independently by two assessors using SIGN, AQUILA and STROBE. The protocol was registered in PROSPERO [CRD42017067728].

RESULTS

Thirteen eligible studies were identified: 9 (4,432 participants) after hip arthroplasty and 4 (7,137participants) after knee arthroplasty. Narrative synthesis was performed due to considerable heterogeneity in quantifying exposures. We found limited evidence that post-operative activities (work or leisure) did not increase the risk of knee revision and could even be protective. We found insufficient high-quality evidence to indicate that exposure to physically-demanding occupations increased the risk of hip revision although "heavy work", agricultural work and, in women, health services work, may be implicated. We found conflicting evidence about risk of revision hip arthroplasty associated with either leisure-time or total physical activities (occupational or leisure-time).

CONCLUSION

There is currently a limited evidence base to address this important question. There is weak evidence that the risk of revision hip arthroplasty may be increased by exposure to physically-demanding occupational activities but insufficient evidence about the impact on knee revision and about exposure to leisure-time activities after both procedures. More evidence is urgently needed to advise lower limb arthroplasty recipients, particularly people expecting to return to jobs in some sectors (e.g., construction, agriculture, military).

The First Report of the International Cartilage Regeneration and Joint Preservation Society's Global Registry

OBJECTIVE

The International Cartilage Regeneration and Joint Preservation Society's (ICRS's) global registry, aims to be the best source of information for patients and an unbiased resource of evidence-based medicine for scientists and clinicians working to help those unfortunate enough to suffer the pain and disability associated with articular cartilage lesions. This article constitutes the scientific summary of the reports' main findings.

DESIGN

The article outlines the historical precedents in the development of orthopedic registries from the earliest tumor registries, then local arthroplasty databases that led ultimately to international collaborations between national arthroplasty and soft tissue registries. The ICRS global cartilage registry was designed from the outset as a GDPR (General Data Protection Regulation) compliant, multilingual, multinational cooperative system. It is a web-based user-friendly, live in 11 languages by end 2019, which can be accessed via https://cartilage.org/society/icrs-patient-registry/. Patients and clinicians enter data by smartphone, tablet, or computer on any knee cartilage regeneration and joint preservation treatment, including the use of focal arthroplasty. Knee Injury and Osteoarthritis Outcome Score and Kujala patient-reported outcome measures are collected preoperatively, 6 months, 12 months, and annually for ten years thereafter. EQ-5D data collection will allow cost-effectiveness analysis. Strengths, weaknesses, and future plans are discussed.

RESULTS

Since inception the registry has 264 users across 50 countries. Major findings are presented and discussed, while the entire first ICRS global registry report is available at https://cartilage.org/society/icrs-patient-registry/registry-annual-reports/. Conclusion. A measure of the maturity of any registry is the publication of its findings in the peer reviewed literature. With the publication of its first report, the ICRS global registry has achieved that milestone.

The rise of registry-based research: a bibliometric analysis

Background and purpose - The main purpose of arthroplasty registries is to collect information on patients, techniques, and devices to monitor and improve the outcome of the specific procedure. This study analyses the role played by registries in the orthopedic research community and describes publication trends, characteristics, and patterns of this field of research.Patients and methods - A descriptive-bibliometric review was conducted. Scopus was the database used for the research. All articles published from 1991 to December 2020 containing keywords related to registries and arthroplasty were considered. In particular, the following dimensions were analyzed in detail: (i) papers/year; (ii) journals; (iii) countries; (iv) research growth rate; (v) collaboration among countries. VOSviewer software was used to perform the bibliometric analysis. Finally, the 50 most cited papers of the last 10 years were briefly analyzed.Results - 3,933 articles were identified. There has been growing interest in the topic since 2010. Acta Orthopaedica ranked first for the number of articles published. The country with the largest number of articles citing registries was the United States, followed by the United Kingdom and Sweden. The relative number of articles per 100,000 inhabitants is 0.60 for Europe and 0.38 for the United States. The literature in this research area has an average yearly growth rate of 28%.Interpretation - The publication rate in the field of arthroplasty registries is constantly growing with a noteworthy impact in the evolution of this research and clinical area. The growth rate is significantly higher than that of arthroplasty literature (28% vs. 10%) and the collaboration among countries is strong and increasing with time.

Return to Sports After Total Hip Arthroplasty: A Survey Among Members of the European Hip Society

BACKGROUND

The study's aim was to summarize the recommendations given by members of the European Hip Society (EHS) regarding sport activities after total hip arthroplasty (THA).

METHODS

Members of the EHS were invited to complete an online web-based questionnaire including recommendations for 47 sports disciplines. The questions regarding the specific sports were also divided into 4 subcategories: "allowed," "allowed when experienced," "not allowed", and "no opinion." Four intervals for resuming the sports activities after THA were evaluated: within 6 weeks after THA, 6 to 12 weeks after THA, 12 weeks to 6 months after THA, and more than 6 months after THA. Consensus on resuming sports was analyzed.

RESULTS

A total of 150 (32.9%) EHS members participated in the survey. Agreement was found for 5 sports activities in the first 6 weeks after THA, for 10 activities, 6 to 12 weeks after surgery, for 26 activities, 3 to 6 months after THA, and for 37 of 47 activities, 6 months after surgery. Sports activities which were not allowed after THA were handball, soccer and football, basketball, full contact sports, and martial arts.

CONCLUSION

This is the first report describing the recommendations of European hip arthroplasty surgeons on resuming sport activity after THA. Most physical activities were allowed for the patients 6 months after THA. The experience of the patient in performing a distinct sport activity did not influence the recommendations to return to former sports activities. European surgeons are progressively mitigating restrictions to sports after THA. Further studies should evaluate the effects of this trend on patients' outcome and implant survival.

Femoral Stem Fracture in Hip Revision Arthroplasty: A Systematic Literature Review of the Real-World Evidence

Background Total hip arthroplasty (THA) presents as an excellent treatment for the osteoarthritic hip, demonstrating good survival rates. However, aseptic loosening and infection are the main causes of operative revision. The methods used in revision surgery are non-modular or modular THA implants. In addition to the abovementioned revision reasons for THA, this treatment could be associated with the possibility of femoral stem fracture, especially in the modular system. The topic of material failure has been focused on in the public media. The question arises as to how such media reports correlate with the published literature. The observed mentioned number of cases concerning a femoral stem fracture vary between one single case and up to 18.5% within a clinical study, thus presenting an inhomogeneous data situation with a large span. The specific aim of this systematic review is to establish facts and clarify the number of unforeseen events of a femoral stem fracture based on peer review articles and registry data. This clarification is important to us, as these media reports have led to uncertainty among patients.

Methods A systematic review was performed in accordance with the PRISMA statement. Peer review articles in English and German, presenting original articles, meta-analyses, or case reports, were searched from the turn of the millennium up to December 2019. Only articles that reported a femoral stem component fracture, with content of clinical data as well as register data, were included. Relevant papers published after the defined research time frame were taken into account within the discussion.

Results In total, 218 fractures of a femoral stem (141 primary and 77 revision THA) component could be identified within the selected literature. Most cases of a femoral stem fracture occurred in the modular THA implants compared to the non-modular stems. Regarding revision THA, in summary, 77 implants, presenting 23 non-modular and 54 modular implants, failed by means of femoral stem fracture. A review of 11 National Joint Registries shows a revision rate between 0.04 and 0.05% in only 2 registers according to the specific subject of a femoral stem fracture. For the remaining 9 registers, however, detailed information is lacking and only nonspecific information such as a generic “implant failure” or “other reason” (which can cover a multitude of causes) is supplied.

Conclusion A femoral stem fracture presents a devastating complication for the patient, the surgeon as well as for the manufacturer of the implant. Modular THA implants play an increasingly valuable role concerning restoration of individual anatomy in modern THA revision surgery, especially within complex cases. Regarding revision procedures, data suggests a lower risk of femoral stem fracture for modular implants compared to primary procedures, while the risk of fracture for non-modular implants seems to increase during revision. Ultimately, it cannot be proven whether this is actually applicable, since the absolute number of implanted prosthesis systems is not known. Various implant-, patient-, and surgeon-related factors may lead to these reported femoral stem fractures. However, this systematic review suggests that this is, in general, a rare complication.

Development of a diagnostic algorithm identifying cases of dislocation after primary total hip arthroplasty-based on 31,762 patients from the Danish Hip Arthroplasty Register

Background and purpose - Dislocation of total hip arthroplasties (THA) is often treated with closed reduction and traditionally not registered in orthopedic registers. This study aimed to create an algorithm designed to identify cases of dislocations of THAs with high sensitivity, specificity, and positive predictive value (PPV) based on codes from the Danish National Patient Register (DNPR).Patients and methods - All patients (n = 31,762) with primary osteoarthritis undergoing THA from January 1, 2010 to December 31, 2014 were included from the Danish Hip Arthroplasty Register (DHR). We extracted available data for every hospital contact in the DNPR during a 2-year follow-up period, then conducted a comprehensive nationwide review of 5,096 patient files to register all dislocations and applied codes.Results - We identified 1,890 hip dislocations among 1,094 of the included 31,762 THAs. More than 70 different diagnoses and 55 procedural codes were coupled to the hospital contacts with dislocation. A combination of the correct codes produced a sensitivity of 63% and a PPV of 98%. Adding alternative and often applied codes increased the sensitivity to 91%, while the PPV was maintained at 93%. Additional steps increased sensitivity to 95% but at the expense of an unacceptable decrease in the PPV to 82%. Specificity was, in all steps, greater than 99%.Interpretation - The developed algorithm achieved high and acceptable values for sensitivity, specificity, and predictive values. We found that surgeons in most cases coded correctly. However, the codes were not always transferred to the discharge summary. In perspective, this kind of algorithm may be used in Danish quality registers.

Revision Risk After Unipolar or Bipolar Hemiarthroplasty for Femoral Neck Fractures: An Instrumental Variable Analysis of 62,875 Procedures from the Australian Orthopaedic Association National Joint Replacement Registry

BACKGROUND

There remains much international practice variation regarding the choice of a unipolar or bipolar prosthesis design for displaced femoral neck fractures that are treated with hemiarthroplasty. The purpose of the present study was to compare revision rates following primary hemiarthroplasty for femoral neck fracture to determine if the unipolar hemiarthroplasty design increases the risk of revision arthroplasty for all causes.

METHODS

Instrumental variable analysis was performed with use of data that had been entered into the Australian Orthopaedic Association National Joint Replacement Registry from September 1, 1999, to December 31, 2018. Sixty-two thousand, eight hundred and seventy-five patients with femoral neck fractures that were treated with primary modular unipolar or bipolar hemiarthroplasty procedure were analyzed. Hospital preference for prosthesis design in the 12 months prior to the index procedure was used as an instrument to adjust for unmeasured confounding. The primary outcome was time to first revision for any cause. Secondary analyses were performed on the reason for revision (infection, dislocation, periprosthetic fracture, or acetabular erosion), the use of cement femoral stem fixation, and the type of stem (polished or matte).

RESULTS

Modular unipolar hemiarthroplasty was associated with a higher rate of revision at >2.5 years (hazard ratio [HR], 1.86; 95% confidence interval [CI], 1.46 to 2.36; p < 0.001), but there was no difference between the groups before 2.5 years (HR, 0.98; 95% CI, 0.85 to 1.13; p = 0.79). Protective factors for revision included female sex (HR, 0.82; 95% CI, 0.74 to 0.9), use of cemented fixation (HR, 0.69; 95% CI, 0.62 to 0.77), and surgery performed in a public hospital setting (HR 0.79; 95% CI, 0.70 to 0.89). Modular unipolar prostheses had a greater risk of revision for acetabular erosion, particularly in later time periods (HR at ≥5.5 years, 5.10; 95% CI, 2.40 to 10.83; p < 0.001), while being protective against periprosthetic fractures (HR, 0.72; 95% CI, 0.59 to 0.87; p < 0.001) at all time points. There was no difference in terms of the risk of revision for infection, dislocation, or stem type.

CONCLUSIONS

Bipolar hemiarthroplasty designs resulted in a lower risk of revision than unipolar designs. Unipolar hemiarthroplasties are justified for patients with femoral neck fracture and a shorter life expectancy (≤2.5 years).

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Completeness and capture rate of publicly funded arthroplasty procedures in the New Zealand Joint Registry

BACKGROUND

Registry-based studies have become more common due to the availability of a large study cohort. However, the validity of findings is dependent on the completeness of the registry. This study aimed to validate the capture rate of the New Zealand Joint Registry (NZJR) by matching procedures that have been recorded separately via clinical coding by the New Zealand Government's National Surgical Site Infection Improvement Programme (SSIIP).

METHODS

The National Health Index, a unique identification code for all patients, was combined with the arthroplasty procedure performed (primary total knee arthroplasty (TKA), primary total hip arthroplasty (THA), revision TKA or revision THA) and operation side. Publicly funded procedures recorded in the NZJR were matched with procedures recorded by the SSIIP on a record-by-record basis. This identified the total number of arthroplasty procedures performed in New Zealand, which was used as the denominator value to calculate the procedure capture rate of the NZJR.

RESULTS

Between 2013 and 2018, 24 556 primary TKA, 28 970 primary THA, 2107 revision TKA and 4263 revision THA procedures were recorded by both datasets. The NZJR recorded 95.5% of primary TKA procedures, 96.3% of primary THA procedures, 97.1% of revision TKA procedures and 95.2% of revision THA procedures.

CONCLUSION

The NZJR recorded >95% of publicly funded arthroplasty procedures. In contrast, there were inaccuracies in clinical coding by hospitals, particularly with revision procedures, demonstrating the benefits of an arthroplasty registry. However, data recorded by an infection surveillance programme may supplement arthroplasty registry data to strengthen the quality of research.