Translation of 3D Anatomy to 2D Radiographic Angle Measurements in the Ankle Joint
Validity and Reliability
Gwendolyn Vuurberg (Universiteit van Amsterdam, Amsterdam Collaboration on Health & Safety in Sports, Academic Centre for Evidence based Sports medicine (ACES), Rijnstate Hospital)
Nazli Tümer (TU Delft - Biomaterials & Tissue Biomechanics)
Inger Sierevelt (Xpert Orthopedics, Spaarne Gasthuis Academy)
Johannes G.G. Dobbe (Universiteit van Amsterdam)
Robert Hemke (Academic Centre for Evidence based Sports medicine (ACES), Universiteit van Amsterdam, Amsterdam Collaboration on Health & Safety in Sports)
Jan Joost Wiegerinck (Universiteit van Amsterdam, Bergman Clinics)
Mario Maas (Amsterdam Collaboration on Health & Safety in Sports, Universiteit van Amsterdam, Academic Centre for Evidence based Sports medicine (ACES))
Gino M.M.J. Kerkhoffs (Universiteit van Amsterdam, Academic Centre for Evidence based Sports medicine (ACES), Amsterdam Collaboration on Health & Safety in Sports)
Gabriëlle J.M. Tuijthof (Amsterdam Collaboration on Health & Safety in Sports, Universiteit van Amsterdam, Academic Centre for Evidence based Sports medicine (ACES), Maastricht University)
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Abstract
Background: The objective consisted of 2 elements, primarily to define 2 bone geometry variations of the ankle that may be of prognostic value on ankle instability and secondly to translate these bone variations from a 3D model to a simple 2D radiographic measurement for clinical use. Methods: The 3D tibial and talar shape differences derived from earlier studies were translated to two 2D radiographic parameters: the medial malleolar height angle (MMHA) and talar convexity angle (TCA) respectively to ensure clinical use. To assess validity, the MMHA and TCA were measured on 3D polygons derived from lower leg computed tomographic (CT) scans and 2D digitally reconstructed radiographs (DRRs) of these polygons. To assess reliability, the MMHA and TCA were measured on standard radiographs by 2 observers calculating the intraclass correlation coefficient (ICC). Results: The 3D angle measurements on the polygons showed substantial to excellent agreement with the 2D measurements on DRR for both the MMHA (ICC 0.84-0.93) and TCA (ICC 0.88-0.96). The interobserver reliability was moderate with an ICC of 0.58 and an ICC of 0.64 for both the MMHA and TCA, respectively. The intraobserver reliability was excellent with an ICC of 0.96 and 0.97 for the MMHA and the TCA, respectively. Conclusion: Two newly defined radiographic parameters (MMHA and TCA) are valid and can be assessed with excellent intraobserver reliability on standard radiographs. The interobserver reliability was moderate and indicates training is required to ensure uniformity in measurement technique. The current method may be used to translate more variations in bone shape prior to implementation in clinical practice. Level of Evidence: Level III, cohort study.
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