Knee ArthropathyNCT07398742
Incidence and Microbial Profiles of Periprosthetic Joint Infection After Total Knee Arthroplasty in Obese vs Non-Obese Patients
An observational study of Knee Arthropathy and PJI, run by Bispebjerg Hospital at 1 site in Denmark.
Trial summary
Importance: After a primary total knee arthroplasty (TKA), we anticipate that obese individuals are more likely to experience a of periprosthetic joint infection (PJI). Knowing the microbial profile in obese patients can potentially help in choosing the proper prophylactic measures for this group as well as tailoring… Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Knee Arthropathy, PJI
- How many people
- 101,299 participants
- Where
- 1 siteDenmark
- Study dates
- 1 Jan 2025to 25 Nov 2025
- How long will I take part?
- 2 Years
- Phase
- Observational
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Study population: In order to be eligible, we will include adult patients with primary or secondary osteoarthritis (due to meniscus or cruciate ligament lesion) who underwent primary TKA between January 1, 2011, and February 28, 2021, and for whom weight and height data are available. Patients will be identified from the DKR. Patients are followed for 2 years, until first revision, death or migration, whichever comes first.
Who may be able to join
- Adults with available BMI data recieved knee arthroplasty due to osteoarthritis
Who cannot join
- -
Trial locations and contacts
1 site in 1 country.
Denmark1 site
Department of Orthopedic surgery and traumatology, Bispebjerg Hospital, Copenhagen, Denmark
Copenhagen NV, 2400
About this study
Importance: After a primary total knee arthroplasty (TKA), we anticipate that obese individuals are more likely to experience a of periprosthetic joint infection (PJI). Knowing the microbial profile in obese patients can potentially help in choosing the proper prophylactic measures for this group as well as tailoring the empirical antibiotics in relation to PJI in obese patients.
Objective: To compare incidence of PJI revisions within 2 years after TKA in obese vs non-obese OA patients. Secondarily: To compare microbial profiles of infections in these groups in two time windows: early (≤90 days) vs late (91-730 days) and incidence of revisions due to all causes within 2 years.Design and Setting: We will include patients having primary knee arthroplasty using Danish national registers. Patients will be stratified into anthropometric groups, referred to as exposed and unexposed to obesity, based on their baseline Body Mass Index (BMI). Participants included in the analysis population will be followed up for 2 years, until first revision, death or migration whichever comes first.
Read more
Participants: We will include adult patients with available weight and height data with primary/idiopathic or secondary (due to meniscus or cruciate ligament lesion) OA who received primary TKA in the period from 2011-01-01 and 2021-02-28. Patients will be identified from the Danish knee arthroplasty register.
Exposure and Comparator: The cohort will be divided into obese (exposed), defined as body mass index (BMI) ≥ 30 kg/m2; and non-obese (unexposed), defined as BMI < 30 kg/m2.
Main Outcomes and Measures: The primary outcome will be revision due to prosthetic joint infection (PJI) within 730 days following TKA. Secondary endpoints will then be to examine revision due to all causes within 730 days following TKA and type of microbial infection between obese and non-obese in the first 90 days and the period from 91 days to 730 days following TKA.
Planned Statistical Analyses: We will use descriptive statistics to summarize the baseline characteristics of the two groups. Hazard ratios with corresponding two-sided 95% confidence intervals (95%CIs) for experiencing the outcome will be estimated using a Cox proportional hazards regression model. We will fit both unadjusted (crude) model and a propensity score adjusted model calculated based on age, sex, highest completed education, household income, comedications, and Elixhauser Comorbidity Measure (ECM), all collected up to the day of surgery. Stratified analyses will categorize PJI cases by bacterial infection and compare crude proportions between groups based on the absolute risk difference with 95% confidence intervals.
Ethical Considerations and Registration: The study and its statistical analysis plan will be registered in clinicaltrials.org prior to conducting the study.
- Conditions
- Knee Arthropathy, PJI
- Keywords
- microbiological profiles, knee arthroplasty, obesity, pji
- Medical subject headings
- Obesity, Juvenile polyposis syndrome
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
| Study group | Role | What they receive |
|---|---|---|
| Patients with obesity | Patients with body mass index of 30 or more | |
| Patients without obesity | Patients with body mass index less than 30 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Incidence Periprosthetic joint infection
PJI: our definition of PJI is adapted from The European Bone and Joint Infection Society (EBJIS) criteria as at least one of the following:
- Danish Knee Arthroplasty Register-registered revision surgery due to infection. B. At least 2 deep-tissue samples of phenotypically indistinguishable bacteria isolated from at least 3 deep-tissue samples C. One or more positive intraoperative samples from a closed fluid aspirate AND a biopsy (fluid AND tissue) of phenotypically indistinguishable bacteria isolated.
Measured: 2 years
Secondary outcomes (3)
Incidence of Revision due to all causes
Any registered surgery in the ipsilateral knee following the primary arthroplasty extracted from the danish knee arthroplasty register
Measured: 2 years
Proportions Microbiological profiles in periprosthetic infection
For the revision due to PJI, we will stratify the outcome looking into the proportions of the following groups of bacteria A. PJI due to Staphylococcus aureus. B. PJI due to Coagulase-negative staphylococci. C. PJI due to other gram-positive bacteria. D. PJI due to gram-negative bacteria. E. PJI due to anaerobic bacteria. F. PJI due to mycoplasmic infection. G. PJI due to polymicrobial infection. H. PJI with negative culture.
Measured: 90 days
Proportions of Microbiological profiles in periprosthetic infection
For the revision due to PJI, we will stratify the outcome looking into the proportions of the following groups of bacteria A. PJI due to Staphylococcus aureus. B. PJI due to Coagulase-negative staphylococci. C. PJI due to other gram-positive bacteria. D. PJI due to gram-negative bacteria. E. PJI due to anaerobic bacteria. F. PJI due to mycoplasmic infection. G. PJI due to polymicrobial infection. H. PJI with negative culture.
Measured: 91 days to 2 years
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted10 Feb 2026
- Study start1 Jan 2025
- Primary completion25 Nov 2025
- Study completion25 Nov 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Knee ArthropathyStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Cohort
- Time perspective
- Other
- Enrolment
- 101,299 participants (actual)
- Target duration
- 2 Years
Sponsor and investigators
- Lead sponsor
- Bispebjerg Hospital
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Saber Muthanna Saber, Bispebjerg Hospital
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07398742
- Sponsor's protocol ID
- p-2023-14433-Micro
- Status last verified
- Sep 2025
- First submitted
- 25 Sep 2025
- Last updated
- 10 Feb 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 10 Feb 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Incidence and Microbial Profiles of Periprosthetic Joint Infection After Total Knee Arthroplasty in Obese vs Non-Obese Patients
- ClinicalTrials.gov ID
- NCT07398742
- Acronym / sponsor ID
- p-2023-14433-Micro
- Conditions
- Knee Arthropathy, PJI
- Keywords
- microbiological profiles, knee arthroplasty, obesity, pji
- Study type
- Observational
- Recruitment status
- Completed
- Enrolment
- 101,299 participants (actual)
- Lead sponsor
- Bispebjerg HospitalUniversity, hospital or other
- Study start
- 1 Jan 2025 (actual)
- Primary completion
- 25 Nov 2025 (actual)
- Study completion
- 25 Nov 2025 (actual)
- First posted
- 10 Feb 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Importance: After a primary total knee arthroplasty (TKA), we anticipate that obese individuals are more likely to experience a of periprosthetic joint infection (PJI). Knowing the microbial profile in obese patients can potentially help in choosing the proper prophylactic measures for this group as well as tailoring the empirical antibiotics in relation to PJI in obese patients.
Objective: To compare incidence of PJI revisions within 2 years after TKA in obese vs non-obese OA patients. Secondarily: To compare microbial profiles of infections in these groups in two time windows: early (≤90 days) vs late (91-730 days) and incidence of revisions due to all causes within 2 years.Design and Setting: We will include patients having primary knee arthroplasty using Danish national registers. Patients will be stratified into anthropometric groups, referred to as exposed and unexposed to obesity, based on their baseline Body Mass Index (BMI). Participants included in the analysis population will be followed up for 2 years, until first revision, death or migration whichever comes first.
Participants: We will include adult patients with available weight and height data with primary/idiopathic or secondary (due to meniscus or cruciate ligament lesion) OA who received primary TKA in the period from 2011-01-01 and 2021-02-28. Patients will be identified from the Danish knee arthroplasty register.
Exposure and Comparator: The cohort will be divided into obese (exposed), defined as body mass index (BMI) ≥ 30 kg/m2; and non-obese (unexposed), defined as BMI < 30 kg/m2.
Main Outcomes and Measures: The primary outcome will be revision due to prosthetic joint infection (PJI) within 730 days following TKA. Secondary endpoints will then be to examine revision due to all causes within 730 days following TKA and type of microbial infection between obese and non-obese in the first 90 days and the period from 91 days to 730 days following TKA.
Planned Statistical Analyses: We will use descriptive statistics to summarize the baseline characteristics of the two groups. Hazard ratios with corresponding two-sided 95% confidence intervals (95%CIs) for experiencing the outcome will be estimated using a Cox proportional hazards regression model. We will fit both unadjusted (crude) model and a propensity score adjusted model calculated based on age, sex, highest completed education, household income, comedications, and Elixhauser Comorbidity Measure (ECM), all collected up to the day of surgery. Stratified analyses will categorize PJI cases by bacterial infection and compare crude proportions between groups based on the absolute risk difference with 95% confidence intervals.
Ethical Considerations and Registration: The study and its statistical analysis plan will be registered in clinicaltrials.org prior to conducting the study.
Study design
- Observational model
- Cohort
- Time perspective
- Other
- Target follow-up
- 2 Years
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Patients with obesity | – | –Patients with body mass index of 30 or more |
| Patients without obesity | – | –Patients with body mass index less than 30 |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
- Study population
- In order to be eligible, we will include adult patients with primary or secondary osteoarthritis (due to meniscus or cruciate ligament lesion) who underwent primary TKA between January 1, 2011, and February 28, 2021, and for whom weight and height data are available. Patients will be identified from the DKR. Patients are followed for 2 years, until first revision, death or migration, whichever comes first.
Key inclusion criteria (1 listed)
- Adults with available BMI data recieved knee arthroplasty due to osteoarthritis
Key exclusion criteria (1 listed)
- -
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Primary outcome
Incidence Periprosthetic joint infection
Time frame: 2 years
PJI: our definition of PJI is adapted from The European Bone and Joint Infection Society (EBJIS) criteria as at least one of the following: A. Danish Knee Arthroplasty Register-registered revision surgery due to infection. B. At least 2 deep-tissue samples of phenotypically indistinguishable bacteria isolated from at least 3 deep-tissue samples C. One or more positive intraoperative samples from a closed fluid aspirate AND a biopsy (fluid AND tissue) of phenotypically indistinguishable bacteria isolated.
3 secondary outcomes
Incidence of Revision due to all causes
Time frame: 2 years
Proportions Microbiological profiles in periprosthetic infection
Time frame: 90 days
Proportions of Microbiological profiles in periprosthetic infection
Time frame: 91 days to 2 years
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 10 Feb 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Knee Arthropathy and PJI, run by Bispebjerg Hospital at 1 site in Denmark.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 1 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 10 Feb 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Denmark. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Incidence Periprosthetic joint infection (time frame: 2 years). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 10 Feb 2026.