Regression Discontinuity Design Search for Differences in Mortality and Revision for Fixation Type of THA

November 8, 2021 updated by: Rudolf W Poolman, MD PhD, Leiden University Medical Center

Age-based Cut-off Point as Methodological Approach in Search for Differences in Mortality and Revision for Fixation Type: Cemented Versus Uncemented Total Hip Arthroplasty

The goal of this study is to apply the regression discontinuity design (RD) methodology on arthroplasty registry data. The investigators aim to use an age-based cut-off for fixation type choice and estimate the causal effect of fixation type on short term mortality and revision, using a fuzzy regression discontinuity design.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

The optimal method of fixation for primary total hip arthroplasty (THA), cemented or uncemented remains unknown. Studying implant survival in both RCT and retrospective study design, as measured by the revision rate both gives inconclusive evidence, largely due to heterogeneity between patient groups. A network meta-analysis showed similar survival of newer uncemented implants compared to the traditional cemented hip implants. In general, older patients more frequently have cemented THAs. However, since these elderly patients have more comorbidity and might pass away or might be unfit for revision surgery, the likelihood of revision will be lower compared with younger patients with an uncemented THAs.

In the last decade, there is a trend towards an increased use of uncemented implants in Europe, Australia and the United States. This despite the fact that registry data show not unequivocal superior outcomes of these uncemented stems. One of the most important methodological challenges in observational data, is to determine whether the medical intervention under study is causally related to an outcome, rather than simply being correlated with another factor that is truly causally related to the outcome under study. This is a particular threat as in observational studies comparison groups are typically different in more aspects than just treatment type because of non-random treatment allocation. Patients are treated in accordance with the preferences of treating physicians, rather than because of a coin flip, like in randomized studies. These treatment choices are frequently informed by a patient's severity of illness. The treatment may be associated with outcome but could be interfered by other factors like disease severity that are causally related to outcome. Thus, observational studies assessing the causal effect of treatments are at risk of obtaining incorrect results. This type of bias is called confounding by indication. Since overall registry data are prone to inclusion bias and the aforementioned confounding by indication, a randomised controlled trial (RCT) design to analyse the difference in revision rate between these two THA fixation methods could clarify this unanswered question. RCTs are the best scientific method for evaluating the efficacy of treatment. However, randomised controlled trials may have poor external validity due to exclusion of patients not meeting the inclusion criteria. Therefore, complementing any evidence on treatment efficacy from randomised controlled trials with that from observational studies is valuable. When looking at implant survival an RCT design is also impractical due to the relatively long time until revisions (with the risk of revision is as low as 0.5 percent per year for the first 20 years) occur and thus a large number of patients needed, to correct for the heterogeneity between these patients. Furthermore, studying data from the Dutch Arthroplasty Registry (LROI), it shows a large variation in clinical practice of type of fixation of hip and cup stems between hospitals. When using data from a national registry with high completeness and hospital coverage, such as the LROI, regardless of age, confounding by indication exists (e.g. large variation in the selection of fixation type) and the patient group will be very heterogeneous. Thus, new research methods are warranted to isolate the effect of fixation of THA on outcome within registries.

Some orthopaedic surgeons and hospitals use an age-based cut-off in the choice for the type of fixation of components of the THA. The existence of such simple age-based cut-off guidelines for choosing for either a cemented or non-cemented stem and/or cup between different hospitals, enables us to analyse the causal effect of fixation on revision in THA. In one of the hospitals in the LROI it is known which age dependent cut-off points are used. In male patients above the age of 70 years old cement fixation is used, and under the cut-off age an uncemented THA is placed. In female patients this cut-off age is set at 65 years of age. This age-based cut-off point for assignment of either cemented or uncemented THA offers the opportunity for a new quasi-experimental research design while limiting the potential for selection bias, and allowing causal inference, namely the regression discontinuity design (RD). The RD is a quasi-experimental study design that was first introduced by psychologists Thistlethwaite and Campbell, who used the RD to evaluate the impact of National Merit Scholarship awards on awardees' careers and attitudes. Since then RD has also been applied in politics, psychology, and other areas, but a recent study showed it is underutilized in medicine.

The RD identifies causal effects by exploiting a treatment assignment practice: the assignment of treatment based on whether a patient scores above or below a cut-off point on a continuously measured variable, such as blood pressure, cholesterol, CD4 count or in our case age. Treatment assignment following such a rule can be either deterministic (every patient on the one side of the cut-off value receives the treatment and every patient on the other side does not) or probabilistic (the probability of receiving the treatment is higher on the one side of the cut-off value than on the other side). The first case is called ''sharp'' RD design (SRD) and the second ''fuzzy'' RD design (FRD).

The goal of this study is to apply the regression discontinuity design (RD) methodology on arthroplasty registry data. The investigators aim to use an age-based cut-off for fixation type choice and estimate the causal effect of fixation type on short term mortality and revision, using a fuzzy regression discontinuity design.

Study Type

Observational

Enrollment (Actual)

43789

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Netherlands
    • Zuid Holland
      • Leiden, Zuid Holland, Netherlands
        • Leiden University Medical Cente

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Sampling Method

Non-Probability Sample

Study Population

The data will consist of all the THAs done in the aforementioned period in the 94 hospitals who report to the Dutch Arthroplasty Register.

Description

Inclusion criteria:

  • Primary total hip arthroplasty with diagnosis osteoarthritis.
  • Placed January 1st 2007 and December 31th 2017
  • Patients who are 18 years and older

Exclusion criteria:

  • Hybrid fixation type (cemented stem and uncemented acetabular component)
  • Reverse hybrid fixation type (uncemented stem and cemented acetabular component)
  • Metal-on-metal bearing THA

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
THA
Patient with primary total hip arthroplasty
Procedure: Cemented THA
THA with cement fixation
Procedure: Unemented THA
THA with uncemented / pressfit fixation

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Number of Participants who die within 90 days after surgery
Time Frame: 90 days
Mortality after surgery
90 days
Number of Participants who undergo revision surgery of the treated hip
Time Frame: 2 years
Number of Participants who undergo revision surgery of the treated hip as recorded in the LROI database.
2 years

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Number of Participants who undergo revision surgery of the treated hip
Time Frame: 5 years
Number of Participants who undergo revision surgery of the treated hip as recorded in the LROI database.
5 years

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Leiden University Medical Center

Collaborators

Erasmus Medical Center
Academisch Medisch Centrum - Universiteit van Amsterdam (AMC-UvA)
OLVG
Dijklander Hospital, Hoorn and Purmerend, The Netherlands
Radboud University Medical Centre Nijmegen, Nijmegen, the Netherlands

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

January 1, 2007

Primary Completion (Actual)

December 1, 2019

Study Completion (Actual)

December 1, 2019

Study Registration Dates

First Submitted

May 3, 2021

First Submitted That Met QC Criteria

October 24, 2021

First Posted (Actual)

November 4, 2021

Study Record Updates

Last Update Posted (Actual)

November 15, 2021

Last Update Submitted That Met QC Criteria

November 8, 2021

Last Verified

November 1, 2021

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 17011991

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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