Weight-bearing computed tomography (WBCT), also called weight-bearing cone-beam CT or standing CT, is a medical imaging technique in which cone-beam computed tomography of the lower limb is acquired while the patient stands, so that the bones are imaged under physiological load. It is used mainly in foot and ankle surgery and, less commonly, for the knee. Its stated advantage over conventional computed tomography is that it combines three-dimensional imaging with the loaded position that conventional radiography provides only in two dimensions. The equipment used is a dedicated extremity cone-beam scanner, and much of its practical value derives from that technology rather than from loading as such: compared with multidetector CT it delivers a lower radiation dose, acquires images in less time, costs less to install and is compact enough for use at the point of care. These properties apply to non-weight-bearing examinations of the upper limb as well. The technique emerged in the 2010s and has been studied most extensively in progressive collapsing foot deformity, hallux valgus, syndesmotic injury and hindfoot alignment. Its evidence base is large but of limited methodological quality, and several studies have found no advantage over conventional CT or weight-bearing radiographs for particular measurements. Adoption remains partial: a 2025 survey of the American Orthopaedic Foot and Ankle Society found that 42% of responding members had access to a scanner. Much of the field's leading literature is produced by authors with disclosed financial relationships to scanner manufacturers.
Principles and technique WBCT uses cone-beam geometry, in which a cone-shaped X-ray beam and a flat-panel detector rotate around the limb, rather than the fan-beam geometry and rotating detector array of conventional multidetector CT. Cone-beam acquisition allows a compact gantry that the patient can step into, and produces isotropic voxels suitable for multiplanar and three-dimensional reconstruction. Dedicated extremity cone-beam scanners are small enough to sit in an outpatient clinic and, in some designs, to run from a standard mains outlet with minimal additional shielding. Depending on the device, one or both limbs may be scanned from below the heel to above the knee.
Relationship to extremity cone-beam CT Although the modality is named after its weight-bearing capability, the underlying technology is extremity cone-beam CT, and several of its practical advantages are properties of that technology rather than of loading. Reviews of musculoskeletal cone-beam CT describe reduced radiation dose, short acquisition times, low equipment cost and a footprint small enough for point-of-care use in a clinic or emergency department. These characteristics apply equally to acquisitions made without load. A single acquisition yields both the loaded alignment information conventionally obtained from weight-bearing radiographs and the three-dimensional detail conventionally obtained from CT. Proponents argue that this allows one examination to replace two, shortening the diagnostic pathway; a single-centre series of 11,009 scans reported a 77% reduction in acquisition time relative to the imaging it displaced. The same class of scanner is accordingly used for regions that cannot be loaded. Cone-beam CT has been evaluated for trauma of the small bones and joints, and a meta-analysis of diagnostic test accuracy found it useful in radiocarpal fractures. A scoping review of musculoskeletal trauma imaging concluded that image quality was high and dose lower than multidetector CT, while noting limited evidence on cost-effectiveness. In children, the dose and cost advantages have been reported independently of any weight-bearing indication. Reported disadvantages of cone-beam geometry include increased scatter, cone-beam artefact, and poorer soft-tissue contrast than multidetector CT. An assessment of image quality in a dedicated extremity cone-beam system found bone visualisation comparable to multidetector CT but soft-tissue performance inferior. The American College of Radiology notes that the soft-tissue contrast of WBCT "is relatively poor, making it difficult to detect associated periarticular abnormalities such as soft tissue swelling, effusions, fluid collections, and muscle atrophy". Motion artefact from postural sway during standing acquisition is a recognised problem, and dedicated motion-compensation algorithms have been developed for extremity and weight-bearing knee imaging. Where a large field of view is obtained by stitching successive acquisitions, geometrical stitching errors have been documented as a further source of measurement inaccuracy.
Radiation dose Radiation dose is generally lower than conventional CT of the same region but higher than radiography. A 2024 systematic review of 21 studies by an NHS medical-physics and radiography group found that musculoskeletal cone-beam CT reduced effective dose relative to multidetector CT by a mean factor of about 12, while digital radiography delivered roughly 4.55 times less dose than cone-beam CT. In a paediatric series, mean dose was 0.63–1.1 mGy with WBCT compared with 7.92–10.37 mGy with non-weight-bearing CT. A single-centre review of 11,009 scans reported a small reduction in effective dose (4.3 versus 4.8 μSv) together with a 77% reduction in acquisition time; the same paper reported an institutional financial benefit, and its authors disclose shareholdings in a scanner manufacturer.
History Cone-beam CT was established in dental and maxillofacial imaging before being applied to the extremities. Weight-bearing CT of the lower limb was described by a Finnish group in 2013. Early orthopaedic validation work reported that standing cone-beam CT allowed more accurate measurement of bone position than radiographs or conventional CT. Swiss investigators independently applied the technique to the subtalar joint in 2014, and a radiology group at the Balgrist University Hospital in Zurich published comparisons of the hindfoot and later the knee between non-weight-bearing and upright positions in 2014 and 2015. An international study group was formed to coordinate research, later becoming the International Weight Bearing CT Society, and a dedicated textbook appeared in 2020. A 2024 scoping review identified 129 studies published between 2013 and 2023, of which 84% concerned the foot and ankle.
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