Many patients who receive knee replacement surgery must return for a revision (or repeat) surgery due to ongoing pain, stiffness, infection, or implant loosening. The role of the gut microbiome-the collection of bacteria and other microbes within the human gastrointestinal tract-is just beginning to be recognized in orthopaedics. The gut microbiome has been found to affect the immune response and bone regulation, potentially contributing to infection or loosening after total joint replacement. Antibiotics are regularly used in orthopaedic surgery to reduce the risk of infection, yet they might also harm gut microbiota and reduce their potentially beneficial effects. As a result, understanding the relationship between gut microbiota and surgical outcomes has become increasingly important. Therefore, this study aims to determine if there are differences in gut microbiota composition between patients with well-functioning knee replacements and those requiring revision knee replacements. Additional study aims include assessing inflammation, implant loosening, metal ion levels, and circulating bacteria in blood or tissue between well-functioning or failed knee replacements.
Scheduled to undergo a revision TKA
Willing and able to comply with follow-up requirements
Ability to provide informed consent
Ability to read, write, and speak English
Pregnancy
Less than 3 months post-operation from primary surgery
Diagnosis of periprosthetic fracture
Scheduled for DAIR (debridement, antibiotics, and implant retention) revision surgery
Patients at University Hospital scheduled to undergo a revision TKA.
Cohort
Prospective
Revision Total Knee Arthroplasty
Procedure/SurgeryStudy participants must be scheduled to receive a revision TKA.
Gut Microbiome Composition
The gut microbiome composition of the revision total knee arthroplasty (TKA) cohort prior to revision surgery will be compared to that of the well-functioning TKA cohort. Additionally, we will evaluate changes in the gut microbiome within the revision cohort from before surgery to six weeks after surgery.
Inducible Displacement Measurements with Weight-Bearing Computed Tomography (WBCT)
Seated and standing WBCT exams will be performed. The bone and implant will be segmented, and a novel software (WBCT-based radiostereometric analysis (WBCT-RSA)) will be used to measure implant motion between the double seated exams (precision) or seated and standing exams (inducible displacement). Change in implant position will be measured in millimeters as maximum total point motion (MTPM). MTPM will be compared between the revision TKA cohort and a cohort with well-functioning implants.
Inflammation in the Knee Joint Based on [18F]FEPPA Standard Uptake Values (SUV)
Positron Emission Tomography/Computed Tomography (PET/CT) of the knee joint will be performed using the radiotracer \[18F\]FEPPA, which binds to molecules highly expressed on inflammatory cells. Radiotracer uptake will be quantified using SUV. SUV near the bone and joint will be calculated and compared between the revision TKA cohort and the well-functioning TKA cohort.
Inducible Displacement and Microbiome Composition
Joint and gut microbiome composition, along with inducible displacement measurements, will be assessed to determine whether alterations in the gut microbiome lead to increased within-bone implant motion.
Implant Wear Volume and Within-Bone Implant Motion from Inducible Displacement Exams
Seated and standing WBCT exams will be performed. The bone and implant will be segmented, and a novel software (WBCT-RSA) will be used to measure implant motion between the seated and standing exams (inducible displacement). Change in implant position will be measured in millimeters as MTPM. An optical coordinate measuring machine will be used to quantitatively measure the amount of volume loss from the retrieved implant components. Inducible displacement MTPM will be compared to volume loss to determine if greater within-bone implant motion may cause greater wear of the implant component resulting in more volume loss.
Metal Ion Levels and Within-Bone Implant Motion from Inducible Displacement Exams
Seated and standing WBCT exams will be performed. The bone and implant will be segmented, and a novel software (WBCT-RSA) will be used to measure implant motion between the seated and standing exams (inducible displacement). Change in implant position will be measured in millimeters as MTPM. Metal ion levels (cobalt, chromium, nickel, and titanium) will be measured from a blood draw prior to the revision surgery. Inducible displacement MTPM and metal ion levels will be compared to determine if greater within-bone implant motion causes greater levels of circulating metal ions.
[18F]FEPPA Activity and Microbiome Composition
Joint and gut microbiome composition will be compared to \[18F\]FEPPA activity, to assess whether alterations in the gut microbiome contribute to increased inflammation in the knee joint.
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