Standardization and Reproducibility Regarding Scanning Procedures and Measurements of Weight-bearing Cone Beam CT in the Lower Extremity

Study Overview
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Brief Summary
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Cone Beam CT (CBCT) of the knee is gaining interest, especially regarding patients suffering from patellofemoral instability. With this study we wish to investigate the day-to-day, test-retest reliability of weight bearing (WB) and non-weight bearing (NWB) CBCT of the knee in healthy participants and patients suffering from trochlear dysplasia. The participants and patients will be scanned in the following positions: 0° WB, 0° NWB, 20° WB, 20° NWB on two separate days. The trochlear dysplasia patients will furthermore be scanned 6 months postoperatively. The aim is to develop af protocol on how to both position patients during weight bearing scannings as well as a protocol on how to prepare the cross sectional images before measurements.

Detailed Description
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We expect that scans performed with CBCT will show a clear change in the TT-TG distance when comparing scans performed in two different degrees of flexion of the knee. We expect a discrete change in the TT-TG distance between non-weight bearing and weight-bearing state of the same degree of flexion. We expect that other radiological targets for assessing patellofemoral instability, e.g. in trochlear dysplasia patients will change between the different scan situations. In addition, we expect that the TT-TG distance measurement method has a high reproducibility of intra- and in-terobserver variation as well as over time with repeated scans. The reproducibility is expected to be at least as good or above existing 2D measurement methods on conventional scans. In patients with trochlear dysplasia, a greater TT-TG distance is expected than in healthy controls. In addition, differences in TT-TG distance between flexion/extension as well as between non-weight bearing and weight bearing condition are expected to be greater than in healthy controls. In addi-tion, we expect to be able to detect a correlation between controlled changes in the position of the foot which will lead to passive changes in the TT-TG distance. The purpose of the study is: To investigate changes in TT-TG distance in CBCT scans of the knee joint, in healthy con-trols as well as in trochlear dysplasia patients, in two predefined degrees of flexion (0 ° i.e. fully stretched position; 20 ° flexion), in respectively weight-bearing loaded and unloaded position To investigate the day-to-day reliability of the measured TT-TG distance, knee flexion angle and other radiological measurements regarding patellofemoral instability, at two separate CBCT scan sessions in patients with trochlear dysplasia compared with healthy controls To investigate changes in the TT-TG distance in trochlear dysplasia patients before and after surgery in terms of evaluation of the patellofemoral instability

Official Title
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Standardization and Reproducibility Regarding Scanning Procedures and Measurements of Weight-bearing Cone Beam CT in the Lower Extremity

Conditions
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Musculoskeletal Diseases

Intervention / Treatment
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* Diagnostic Test: Weight bearing CT


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Substudy 1 Healthy Male or female aged 18-39 years Must be able to stand on one leg for 30 seconds Substudy 2 Diagnosed with trochlear dysplasia, in addition healthy Male or female aged 18-39 years Patients scheduled to either a trochlear plastic surgery + MPFL reconstruction or Elmslie-Trillat + MPFL reconstruction + trochlear plastic surgery Must be able to stand on one leg for 30 seconds Exclusion Criteria: Substudy 1 Current knee injury and / or knee pain. Known rheumatoid and / or connective tissue disease. Previous treatment requiring knee injury and / or knee surgery. Pregnancy Substudy 2 Known rheumatoid and / or connective tissue disease Previous treatment requiring knee injury and / or knee surgery. Patients who need distalization Pregnancy

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 39 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Healthy<br>Weight bearing CT in fully extended and flexed (20 degrees) position, loaded and unloaded, respectively. | Diagnostic Test: Weight bearing CT<br>* Weight bearing CT in loaded and unloaded positions<br>|
| Trochlear dysplasia<br>Weight bearing CT in fully extended and flexed (20 degrees) position, loaded and unloaded, respectively. | Diagnostic Test: Weight bearing CT<br>* Weight bearing CT in loaded and unloaded positions<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Measurement of patellofemoral indices | Intra and interrater reliability and day to day repeatability | 1 year |