, Francois Lintz2, Cesar de Cesar Netto3, Alexej Barg4, Arne Burssens5 and Scott Ellis6
Keywords
Weight bearing CT scanCone beam CT scanMusculoskeletal imaging techniquesBeginning of Weight Bearing Computed Tomography Devices
The necessity for weight bearing computed tomography (CT) devices has already been demonstrated in the mid-1990s by Greisberg et al. [1]. This pivotal paper reported on the peritalar subluxation occurring in flatfoot deformities using a simulated weight bearing CT device containing a custom-built loading frame with the patient positioned supine. It soon became a stepping stone for other reports to follow, incorporating a similar setup [2, 3]. Despite these important findings, limitations regarding patient positioning, amount of load, and a high radiation dose were inevitable [4]. This advocated the development toward the weight bearing CT devices currently used in clinical practice.
Foot and Ankle Weight Bearing Computed Tomography Devices
The first weight bearing CT devices were available beginning of the 2010s [5–7]. They incorporate cone beam CT technology, which in essence uses a rotating X-ray to obtain the field of view. It was initially popularized in the dental area, but technical improvements caused it to be widely used across the majority of medical disciplines. The main advantages include a low radiation dose, the absence of superimposition, and a high image resolution. One of the first applications of weight bearing musculoskeletal scanning was dedicated to the foot and ankle [8, 9].

Onsight 3D Extremity System® (Carestream, Rochester, NY, USA). Physical dimensions of this device are as follows (in transport mode): length, 78.8″; width, 32″; and height, 76″. The gantry can be moved upward and turned 90°. This allows additional non-weight bearing imaging of the lower limb, as well as imaging of the upper extremities: the hand, wrist, and elbow. The first version of this device was described in one of the most early technical reports on musculoskeletal weight bearing CT imaging [10]. The first clinical applications were demonstrated in the alignment of flatfoot deformities [6]. Full technical details can be found on the website: https://www.carestream.com/en/us/medical/products/carestream-onsight-3d-extremity-system

PedCAT® (CurveBeam, Philadelphia, PA, USA). Physical dimensions of this device are as follows: length, 58″; width, 28.5″; and height, 51″. Imaging of the foot and ankle can be performed both during weight bearing, physiological bipedal stance, as well as non-weight bearing while seated. The first study using this device included both technical details as well as clinical applications. In this pivotal report, a comparison was made toward non-weight bearing CT regarding radiation dose and accuracy of measurements commonly used in clinical foot and ankle practice [5]. Full technical details can be found on the website: https://www.curvebeam.com/products/pedcat/

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