Clinical trial NCT06909916: Weight-Bearing CT and Conventional Periprosthetic Distal Knee Fractures
Official title: Assessment of Bone Displacement Under Loading Following Distal Femur Periprosthetic Fracture Repair With Weight-Bearing CT and Conventional CT
Study type: INTERVENTIONAL
Overall status: RECRUITING
Phase: NA
Conditions: Periprosthetic Fracture Around Prosthetic Joint Implant
Lead sponsor: London Health Sciences Centre Research Institute OR Lawson Research Institute of St. Joseph's
Sponsor class: OTHER
First posted: 2025-04-04
Enrollment: 20
Sex: ALL
Minimum age (years): 50
Maximum age (years): 90
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Allocation: NA
Intervention model: SINGLE_GROUP
Intervention model description: One single visit: 1 loaded and 2 unloaded scans with weight-bearing CT. One loaded and 2 unloaded scans with conventional CT
Primary purpose: OTHER

Brief summary: Total knee arthroplasty (TKA) is a surgical procedure commonly conducted for patients with end-stage knee osteoarthritis, often leading to improved pain relief and function. However, for patients that have suffered an associated periprosthetic fracture, a broken bone that occurs around the implant of a TKA, they may receive sub-optical care due to a lack of a trustworthy assessments for component fixation and fracture healing in the literature. The prevalence of TKA surgeries is increasing annually and is projected to rise further due to an ageing population and obesity issue. By extension to this primary surgery, more Canadians will require an invasive revision surgery that risks patient morbidity and mortality. Thus, it is imperative to set a standard for fixation and bone healing assessments to lessen revision burdens and improve patient outcomes. CT imaging can effectively visualize areas of incomplete bone ingrowth that may be hidden from overlapping anatomy on plain radiographs, which remains the go-to imaging modality for orthopaedic surgeons to assess periprosthetic fracture healing. The purpose of this prospective cross-sectional study is to examine the efficacy of weight-bearing CT as a diagnostic tool for 20 participants who experienced a distal femur periprosthetic fracture and underwent revision surgery using a fracture fixation plate and screws. Participants will be scanned under loaded and unloaded conditions. Radiographic outcomes will be evaluated, including bone segment displacement and its relation to participants' reports of pain.

Detailed description: Total knee arthroplasty is the most cost-effective and successful treatment for knee joints with end-stage osteoarthritis, with more than 58,000 TKA surgeries in Canada in 2021-2022.1 The prevalence of TKA surgeries is increasing per year and is projected to rise due to an ageing population and obesity problems.1 In addition to the primary surgery, more than 4,000 Canadians require revision TKA surgery per year; the TKA revision burden is estimated to reach $13 billion by 2030 as a consequence of a substantial increase of 149% in primary surgeries by 2030 in the United States.1-3 Revision surgery is more invasive than primary surgery and poses the risk of increasing patient mortality rates, especially for older adults.3 Thus, it is imperative for surgeons to make an appropriate radiographic diagnosis of implant fixation and/or fracture healing, but many cases remain challenging to diagnose.4

In the orthopaedic literature, there is no consensus on a reliable definition criterion for long-bone non-unions, making the standardization of diagnoses difficult; the lack of a trustworthy assessment for component fixation and fracture healing can lead to patients receiving sub-optimal care.5 This can also limit the collection of evidence supporting the use of specific implant components, surgical techniques, and post-operative activity guidelines. Moreover, comparing healing results of different clinical studies for long-bone non-unions can become problematic due to different criteria being used.5 Radiographic features associated with loosening such as radiolucencies are often only appreciable for the cement-bone interface, rather than the cement-implant interface which is the most common site of failure causing loosening.4 Failure to properly diagnose fracture non-union leaves patients in pain with substantial morbidity, while unnecessary surgery risks significant complication. Given the increasing rates of TKA and associated predictions of increasing revision burden,6 along with ongoing debates over the superiority of certain implants or surgical techniques, there is an unmet need for better fixation and bone healing assessment.

Historically, radiostereometric analysis (RSA) has been the gold standard for measuring implant fixation.7 However, it remains a niche tool limited to clinical research because of its requirement for implanted marker beads and specialized equipment being accessible for a handful of labs in North America.7-8 Recently, multiple groups have developed approaches to perform RSA-like measurements using clinical CT scans for shoulder, hip, and knee replacements.9 The accuracy and precision of the "CT-RSA" methods are on par with conventional RSA and acceptable for clinical studies.10-15 It is predicted that there will be a greater uptake of CT-RSA than conventional RSA, but the technology is still in its infancy.9 The application of CT-RSA will undoubtedly be more inclusive as examinations can now be performed on patients who did not have marker beads implanted at the time of their original surgery, and CAD models of implants are not needed.16

Using a weight-bearing CT scanner is the most similar implementation of CT-RSA to conventional RSA, as exams can be acquired in unloaded and loaded positions. However, the availability of weight- bearing CT will always be lesser than conventional clinical CT scanners, even as more and more high volume orthopaedic centres are acquiring weight-bearing CT scanners. While some groups have implemented specialized loading devices to perform such scans with conventional CT,17 a more generalizable approach of simple internal-external leg rotations held in place with tape would ultimately offer the greatest potential uptake across centres.

The results of this proposed study will demonstrate the ability to precisely measure displacements between bone segments under loading following periprosthetic fracture repair with weight-bearing CT and conventional CT scanners. These will be the first-ever measurements of distal femur periprosthetic fracture healing with weight-bearing CT-RSA. Demonstration of this will enable us to pursue future studies that are prospective in nature and may evaluate topics such as time to weight-bearing activities, different types of surgical reconstructions, and relationship between healing and bone quality/bone health. Other centres with access to weight-bearing CT will also benefit from this work. Consideration for the ability to perform similar measurements with conventional CT in place of weight-bearing CT will improve the generalizability of this approach and support it as a clinical diagnostic tool. For example, surgeons may better understand bone fragment motion over time and recommend appropriate postoperative activities for patients' weight-bearing tolerance. Therefore, the proposed study design will evaluate the ability to perform inducible displacement measurements following the surgical repair of distal femur periprosthetic fractures using both weight-bearing CT and conventional CT.

Eligibility criteria: Inclusion Criteria:

* Underwent revision surgery for repair of a distal femur fracture surrounding a primary TKA femoral component using a fracture fixation plate \>1 year
* Age 50-90 years
* Body mass index up to 40kg/m2
* Able to provide informed consent
* Able and willing to do study assessments and follow instructions

Exclusion Criteria:

* Does not understand English
* Undergone revision surgery for any other indication
* Received Intramedullary nail or distal femur replacement
* Cannot independently stand on one leg in the weight-bearing CT during the inducible displacement exam

Primary outcomes:
measure: Maximum Total Point Motion of Fracture Segments from Conventional CT scans
timeFrame: 1 visit is only required for which the outcome measure will then be assessed. Through study completion, approximately of 1 year.
measure: Maximum Total Point Motion of Fracture Segments from Conventional CT scans
timeFrame: 1 visit is only required for which the outcome measure will then be assessed. Through study completion, approximately of 1 year.
measure: Western Ontario and McMaster Universities Arthritis Index (WOMAC) Questionnaire
timeFrame: 1 visit is only required for which the outcome measure will then be assessed. Through study completion, approximately of 1 year.
measure: The Knee Society Score (KSS) Questionnaire
timeFrame: 1 visit is only required for which the outcome measure will then be assessed. Through study completion, approximately of 1 year.
measure: UCLA Activity Score Guideline Questionnaire
timeFrame: 1 visit is only required for which the outcome measure will then be assessed. Through study completion, approximately of 1 year.
Secondary outcomes:
Other outcomes:
Locations:
city: London
country: Canada
facility: University Hospital - London Health Sciences Centre
state: Ontario
Study officials:
affiliation: London Health Sciences Centre Research Institute OR Lawson Research Institute of St. Joseph's
name: Matthew Teeter, PhD
role: STUDY_DIRECTOR
affiliation: Lawson Health Sciences Centre
name: Brent Lanting, MD
role: PRINCIPAL_INVESTIGATOR
affiliation: London Health Sciences Centre
name: Lyndsay Somerville, PhD
role: STUDY_CHAIR
affiliation: Western University
name: Patrick J Mixa, MD
role: STUDY_CHAIR
affiliation: London Health Sciences Centre
name: James Howard, MD
role: STUDY_CHAIR
References:
citation: Steele JR, Ryan SP, Jiranek WA, Wellman SS, Bolognesi MP, Seyler TM. Cost of Aseptic Revision Total Knee Arthroplasty at a Tertiary Medical Center. J Arthroplasty. 2021 May;36(5):1729-1733. doi: 10.1016/j.arth.2020.11.028. Epub 2020 Dec 17.
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