## 2 Materials and Methods  
This is a systematic review of the recent innovations brought by WBCT to the foot and ankle field. In order to specify the scope of the review, we defined'recent' as after 2012, the year [PERSON] et al. [8] published the first paper on a dedicated extremity CBCT device. We defined innovative techniques as techniques which could not be performed using the conventional 2 DXR-MDCT sequence (i.e., absence of concomitant 3D and natural weight-bearing). This would, in theory, include conventional measurements historically performed on weight-bearing 2 DXR, performed on 3D WBCT datasets, for instance the first to second intermetatarsal angle [39] in the forefoot, or the Saltzman angle [14] in the hindfoot. In fact, most WBCT devices have the ability to produce digitally reconstructed radiographs (DRR) [40] to help with the user's learning curve in transitioning from the 2D to the 3D environment. This is possible because WBCT produces a digital clone of the patient's foot and ankle structure, which can in turn be virtually radiographed from multiple angles (Figure 2). Classical measurements can therefore be performed in a standard way. However, this technique inevitably produces the same biases as conventional 2 DXR. Otherwise, classical angles can be measured within the 3D dataset, using multiplanar reconstruction (MPR) views. In this case, a particular slice or slab must be chosen in order to perform the measurement, which requires multiple iterative changes in the orientation of the MPR, because the points which define the angles of interest are not necessarily on the same plane. For instance, the tibia longitudinal axis, the center of the ankle joint and the lowest weight-bearing point of the calcaneus do not belong to a single vertical plane. For the corresponding angle to be measured manually, a slice has to be found by tuning the orientation of the MPR dataset, but again, it is often not possible to find a slice which includes all three points. Another possibility is to select one segment of the angle (the tibia axis) on one plane and compare it to the other side (the calcaneal axis) using the available software, but measuring a single angle from different slices is not always an available function. A third method consists of manually recording 3D coordinates for the points of interest (in the present example, the tibia extremity and the center of the ankle joint's lowest calcaneal point) and calculating the angle using standard trigonometry. Whatever the solution or combination of solutions, this method is always time-consuming [41] and introduces a new kind of bias, which we may call'slice' or'slab' bias, materializing as we must choose a particular slice from which to take the measurements, based on surface landmarks which may vary, being dependent on the operator's habits or knowledge of the anatomy. Although these methods were and are still necessary to perform and describe throughout the process of standardization of measurement methods in WBCT research [15], they inevitably present practical disadvantages which prevent inclusion in the advanced methods review, for we aimed to describe here methods which actually improve the clinical workflow, not slow it down. Hence, articles describing such methods were not included for retrieval. Figure 2: Example of a WBCT digital clone with skin rendering (**a**), digitally reconstructed dorsal-plantar radiograph (**b**) and saggital MPR view (**c**). The PubMed database was used to identify relevant scientific references for the study. We included initially all references regarding CBCT and weight-bearing or WBCT, using the following key words: weightbearing, weight-bearing, standing, extremity, cone beam, CT, computed tomography, multiplanar, foot, ankle, ankle, ankle joint, ankle, joint, ankle joint, ankle. Filters were used to exclude references without an abstract or which were not available in English, French or German.