###### Abstract  
The decade from 2010-2020 has seen the development of cone beam weight-bearing CT (WBCT) as a major innovation in the foot and ankle realm, becoming an important modality for bone and joint imaging. The ability to provide three-dimensional images of the naturally loaded skeleton has enabled several subsequent innovations to arise with aims to hasten image processing and to extend the clinical applications of WBCT. The objective of this work was to identify, categorize and explain those emerging techniques. We performed a structured review of the literature according to PRISMA standards, finally including 50 studies. We subsequently proposed a classification of these techniques. Segmentation and distance mapping were identified as key features. We conclude that although WBCT has already been adopted in a number of clinical communities with an immediate improvement in patient workflows, adoption of advanced techniques is yet to come. However, that relies mostly not on the technology itself, but on improvements in AI software allowing practitioners to quickly process images in daily practice and enabling the clinicians to obtain an accurate three-dimensional evaluation of the segment considered. Standardization will be paramount to amass large amounts of comparable data, which will fuel further innovations in a potentially virtuous circle. Keywords:cone beam CT; weight-bearing CT; distance mapping; coverage maps; automatic segmentation; 3D biometrics; systematic review +
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dedicated use in orthopedics was described in 2011 by [PERSON] et al. [7]. The first mention of a dedicated extremity CBCT device was by [PERSON] et al. in 2012 [8], and the first mention of weight-bearing CBCT (WBCT) in the lower limbs was in 2013 by [PERSON] et al. [9]. The first mention of WBCT in the foot and ankle concerned the pes planovalgus [10], but that was simulated weight-bearing. The first publications on the use of true (i.e., under body weight) WBCT in the foot and ankle were in 2013 by [PERSON] et al. [11] on the biomechanics of the first ray, followed by [PERSON] in 2014 on the superiority of 3D WBCT measurements as compared to 2D or non-weight-bearing WBCT [12]. A quick look at the literature suggests that WBCT would allow clinicians to optimize acquisition speed, therefore reducing operating costs, with a smaller footprint compared to traditional two-dimensional radiography (2 DXR) plus three-dimensional non weight-bearing fan beam MDCT in diverse areas [7; 8; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34]. This would enable clinicians to obtain marked improvements in the operative workflow [32; 35]. Besides advantages for the clinicians, immediate advantages for patients are also huge time gains in their care pathway [32], more accurate diagnoses (i.e., increased chances of detecting injuries commonly missed through standard imaging) [12; 30] and lower radiation doses [32; 36; 37] (Figure 1). However, it also seems that the advantages of CBCT are somewhat overshadowed by the weight-bearing side of the equation, since not many authors have focused on non-weight-bearing cone beam imaging so far [29; 30; 32; 38]. Indeed, it is in the foot and ankle field that the industry has chosen to chase initial prospects, likely because this is where 3D combined with weight-bearing have shown the most evident improvements over the conventional 2 DXR-MDCT sequence. In turn, this was due to the complex anatomy of the foot, including 28 bones with a variety of shapes and sizes, making it hard to correctly assess without 3D or without bearing weight [12]. A large body of literature preceding the WBCT period has already insisted on the importance of weight-bearing while imaging the foot and ankle, using custom devices to simulate weight-bearing with conventional prone MDCT protocols [10].