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Reliability and correlation analysis of computed methods to convert conventional 2D radiological hindfoot measurements to a 3D setting using weightbearing CT



The exact radiographic assessment of the hindfoot alignment remains challenging. This is reflected in the different measurement methods available. Weightbearing CT (WBCT) has been demonstrated to be more accurate in hindfoot measurements. However, current measurements are still performed in 2D. This study wants to assess the use of computed methods to convert the former uniplanar hindfoot measurements obtained after WBCT towards a 3D setting.


Forty-eight patients, mean age of 39.6 ± 13.2 years, with absence of hindfoot pathology were included. A WBCT was obtained, and images were subsequently segmented and analyzed using computer-aided design operations. In addition to the hindfoot angle (HA), other ankle and hindfoot parameters such as the anatomical tibia axis, talocalcaneal axis (TCA), talocrural angle, tibial inclination (TI), talar tilt, and subtalar vertical angle were determined in 2D and 3D.


The mean \(\hbox {HA}_{2\mathrm{D}}\) was \(0.79^{\circ }\) of valgus ± 3.2 and the \(\hbox {HA}_{\mathrm{3D}}\) was \(8.08^{\circ }\) of valgus ± 6.5. These angles differed significantly from each other with a \(P<0.001\). The correlation between both showed to be good by \(\hbox {a}\) Pearson correlation coefficient (r) of 0.72 (\(P < 0.001\)). The \(\hbox {ICC}_{\mathrm{3D}}\) showed to be excellent when compared to the \(\hbox {ICC}_{\mathrm{2D}}\), which was good. Similar findings were obtained in other angles. The highest correlation was seen between the \(\hbox {TI}_{\mathrm{2D}}\) and \(\hbox {TI}_{\mathrm{3D}}\) (r = 0.83, \(P < 0.001\)) and an almost perfect agreement in the \(\hbox {TCA}_\mathrm{3D}\) (\(\hbox {ICC}_{\mathrm{3D}}=0.99\)).


This study shows a good and reliable correlation between the \(\hbox {HA}_{\mathrm{2D}}\) and \(\hbox {HA}_{\mathrm{3D}}\). However, the \(\hbox {HA}_{\mathrm{3D}}\) overcomes the shortcomings of inaccuracy and provides valuable spatial data that could be incorporated during computer-assisted surgery to assess the multiplanar correction of a hindfoot deformity.

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The authors wish to thank Ir. Karim Chellaoui, as a clinical engineer for his attributive remarks to the study design and thorough review of the statistics. The linguistic and structural support was provided by Maxwell Weinberg, research assistant at the University of Utah and Hannes Van Wynendaele, MLing of Ugent.

CT International Study Group (WBCT ISG), committee members are as follows: Richter M, Barg A, Lintz F, de Cesar Netto C and Burssens A. M Richter: Prof dr M Richter, MD, PhD. Head of the Department of Foot and Ankle Surgery in Rummelsberg and Nuremberg, Germany; A Barg: Prof dr A Barg, MD. Associate Professor of Orthopaedics, University Hospital of Utah, USA; F Lintz: dr F Lintz, Department Foot and Ankle Surgery, Clinique de L’Union in Toulouse, France; C de Cesar Netto: dr de Netto C, Department Foot and Ankle Surgery, Hospital for Special Surgery, NY, USA. France; Burssens A: Burssens A, MD Resident Orthopaedic Surgery, Department of Orthopaedic Surgery, Ghent University Hospital, De Pintelaan 185, 9000 Gent, Belgium.

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Correspondence to A. Burssens.

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The authors declare no conflict of interest or acceptance of external funding.

Ethical approval

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. For this type of study formal consent was not required.

Additional information

Weightbearing CT International Study Group contributing authors were as follows: M. Richter, A. Barg, F. Lintz, C. de Cesar Netto and A. Burssens.

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Burssens, A., Peeters, J., Peiffer, M. et al. Reliability and correlation analysis of computed methods to convert conventional 2D radiological hindfoot measurements to a 3D setting using weightbearing CT. Int J CARS 13, 1999–2008 (2018).

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  • Hindfoot alignment
  • Weightbearing CT
  • Computed radiology
  • Hindfoot correction