• The measurement of hindfoot alignment is a technical challenge.
• Today, hindfoot alignment is typically measured on hindfoot alignment view radiographs or long axial view radiographs. Measurements on both types of radiographs are hampered by technical shortcomings such as minimal rotational misplacement of the foot at the time of image acquisition. In previous publications our study groups demonstrated substantial measurement errors due to these shortcomings as well as bad interreader agreement.
• Hindfoot alignment measurement is feasible on MR images but hampered by the non-weight-bearing position of the patient and therefore not suited for pre-treatment evaluation.
• In an ex vivo study using plastic phantoms of a foot our research group could demonstrate superior interreader agreement and complete correction for foot misplacement at the time of image acquisition using a 3D secondary measurement technique based on biplanar low dose radiographs.
• Image acquisition using biplanar low dose radiographs is associated with a substantial reduction (about 1/7) of radiation dose applied to the patient compared to standard radiographs.
• Therefore the question arises if these excellent ex vivo results can be confirmed in a prospective clinical study.

Objectives:

1. Evaluation of technical feasibility of 3D hindfoot alignment measurements based on biplanar radiographs.
2. Reproduction of superior interreader agreement of measurements based on biplanar radiographs compared to measurements on conventional radiographs.

Additional information to the brief summary:

Outcome(s): Hindfoot alignment measurement on standard radiographs and biplanar radiographs. The hindfoot angle is measured between the tibial axis and the calcaneal axis in degrees. Measurement results on plain films and based on 3D reconstructions will be compared.

Inclusion/Exclusion criteria:

• Inclusion: All patients referred for hindfoot alignment radiographs. These are all adults having suffered severe trauma or suffering from osteoarthrosis of the ankle joint. No inclusion of vulnerable participants.
• Exclusion criteria: Prior surgery, prior fracture, children and adolescents younger than the age of 20 years, known pregnancy.

Measurements and Procedures: Measurement of hindfoot alignment based on conventional radiographs and based on biplanar radiographs by two independent radiologists. Comparison of measurement results (paired-t-test, Wilcoxon signed-rank test) and calculation of interreader agreement (Intraclass correlation coefficient).

Study Product / Intervention: EOS low-dose biplanar x-ray scanner, EOS imaging, Paris, France One scan of the ankle joint to obtain an antero-posterior and lateral view.

Control Intervention: Conventional x-rays of the ankle joint (a.p., lateral, long axial or hindfoot alignment view) as referred from the clinician for treatment planning.

Number of Participants: 50 adults Based on a power analysis we think that this number of patients will enable reliable results. Because we do not know how big the differences between the measurements on standard radiographs and measurements on biplanar radiographs will be it is very difficult to perform a reasonable power analysis. In prior studies comparing torsion measurements on biplanar radiographs with CT measurements we were able to produce reliable results with the same number of patients.

Study Schedule:

First-Participant-In: June 2014 Last-Participant-Out: May 2015

Inclusion Criteria:

• All patients referred for hindfoot alignment radiographs. These are all adults having suffered severe trauma or suffering from osteoarthrosis of the ankle joint. No inclusion of vulnerable participants.

Exclusion Criteria:

• Prior surgery, prior fracture, children and adolescents younger than the age of 20 years, known pregnancy.

Adult patients with clinically suspected hindfoot malalignment