A stitch in time: stitching errors in digital radiology

Modern digital radiological techniques include “stitching” together multiple x-ray images. This provides one overall image of the area of interest, such as the entire spine or lower limbs, for deformity assessment. Dedicated software automatically combines separate exposures and allows for overlap. Image acquisition is rapid, minimising patient motion artefact and reducing distortion.1 However, if images are inappropriately put together (digitally stitched), stitching errors may occur with this computer-driven process. If not manually corrected by the radiology technician, the supplied image may hide pathology or give the false impression of abnormality. Four cases of digital stitching error have recently occurred in our tertiary referral paediatric hospital.

Digitally stitched x-rays from the lower limbs were obtained for routine assessment of a child with skeletal dysplasia, and fractures of the left tibia and fibula were apparent (Box, A). This did not correlate with the clinical findings, including the child dancing in the waiting room. The radiology department was contacted and they re-issued corrected images (Box, B). Spinal x-rays in two patients after scoliosis surgery incorrectly showed broken surgical rods. In the context of ongoing symptoms, the option of revision surgery was discussed with the family in the first case. Repeat x-rays, obtained as part of the pre-operative planning, showed the rod was in fact not broken. A stitching error was immediately recognised by the spinal surgeon when a second similar case occurred. In a fourth case, comparison of the anteroposterior and lateral views of a child’s spine showed different numbers of vertebrae in the two views (11 vertebrae on the frontal view and 12 on the lateral).

Digital radiology is commonplace and allows rapid image acquisition and ease of digital measurement.2 However, technical errors — digital stitching errors — may occur. Although rarely reported, these may be relatively common, with one study identifying stitching errors in 14 out of 86 reviewed scoliosis studies.1 Despite ongoing technological refinements,3 clinicians should always carefully check digitally stitched images: look for soft tissue mismatch, correlate with source images and clinical presentation, and avoid digital stitching in certain patients, such as people with movement disorders.

Box – Digitally stitched long leg images of a paediatric patient, showing the stitching error and apparent fracture (A),* and corrected image with resolution of the stitching error and no fracture (B)

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* Note the mismatched soft tissue shadow (A).