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End-stage extension of the knee and its influence on tibial tuberosity-trochlear groove distance (TTTG) in asymptomatic volunteers

Dietrich, Tobias ; Betz, Michael ; Pfirrmann, Christian ; Koch, Peter ; Fucentese, Sandro

In: Knee Surgery, Sports Traumatology, Arthroscopy, 2014, vol. 22, no. 1, p. 214-218

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    Title
    • End-stage extension of the knee and its influence on tibial tuberosity-trochlear groove distance (TTTG) in asymptomatic volunteers
    Author
    • Dietrich, Tobias. Department of Radiology, Orthopedic University Hospital Balgrist, University of Zurich, Forchstrasse 340, 8008, Zurich, Switzerland
    • Betz, Michael. Department of Orthopedic Surgery, Orthopedic University Hospital Balgrist, University of Zurich, 8008, Zurich, Switzerland
    • Pfirrmann, Christian. Department of Radiology, Orthopedic University Hospital Balgrist, University of Zurich, Forchstrasse 340, 8008, Zurich, Switzerland
    • Koch, Peter. Department of Orthopedic Surgery, Orthopedic University Hospital Balgrist, University of Zurich, 8008, Zurich, Switzerland
    • Fucentese, Sandro. Department of Orthopedic Surgery, Orthopedic University Hospital Balgrist, University of Zurich, 8008, Zurich, Switzerland
    Document Type
    • Postprint
    Language
    • English
    Published in
    • Knee Surgery, Sports Traumatology, Arthroscopy, 2014, vol. 22, no. 1, p. 214-218. Springer Berlin Heidelberg
    Other Version
    OAI-PMH Identifier
    • oai:doc.rero.ch:325653
    Summary
    Purpose: Increased tibial tuberosity-trochlear groove distance (TTTG) is one potential correcting parameter in patients suffering from lateral patellar instability. It was hypothesized that end-stage extension of the knee might influence the TTTG distance on MR images. Methods: Transverse T1-weighted MR images of the knee were acquired at full extension, 15° and 30° flexion of the knee in 30 asymptomatic volunteers. MRI parameters: slice thickness: 3mm, matrix: 256×384, FOV: 150×150mm. Two observers independently measured the TTTG at all positions. Results: Mean TTTG for observer 1 was 15.1±3.2mm at full extension, 10.0±3.5mm at 15° flexion and 8.1±3.4mm at 30° flexion. Mean TTTG for observer 2: 14.8±3.3mm at full extension, 9.4±3.0mm at 15° flexion, 8.6±3.4mm at 30° flexion. Mean values were significantly different (p<0.001) between full extension and 15° as well as 30° flexion for both observers. Mean values were significantly different (p<0.001) between 15° and 30° for observer 1, but not for observer 2 (n.s.). Interobserver agreement was very good (intraclass correlation coefficient: 0.87-0.88; p<0.001). Conclusions: The TTTG increases significantly at the end-stage extension of the knee. Therefore, the comparability of published TTTG values measured on radiographs, CT and MRI at various flexion/extension angles of the knee are limited. Level of evidence: Development of diagnostic criteria in a consecutive series of patients and a universally applied ‘gold' standard, Level II.