A Cocker Spaniel presented for recurrence of right forelimb lameness 33 months following transcondylar screw placement for a humeral intracondylar fissure. Elbow radiographs showed no evidence of implant‐related complications. Standard CT scale reconstruction images failed to demonstrate implant failure. Extended CT scale reconstruction images revealed a fracture through the mid‐portion of the screw. Revision surgery confirmed the implant failure; the screw was replaced and the lameness subsequently resolved. Extended CT scale reconstruction images allow detailed assessment of metal implants and should be considered when implant failure is suspected.

Objective Application of extended computed tomography scale (ECTS) reconstruction to diagnose metal implant failure has been described in a single case report. The purpose of this study was to compare the features and visibility of humeral transcondylar screw fractures in standard CT scale (SCTS) and ECTS images. Study Design Case series: CT images of dogs with fractured transcondylar screws were retrospectively reviewed and described in both SCTS and ECTS images. Results Five dogs with a total of six transcondylar screw failures (five right and one bilateral) were reviewed. All cases had an ongoing humeral intercondylar fissure with varying degrees of stress remodelling. The fracture was seen in all screws on ECTS images, however only in three implants on SCTS images. The measured fracture gap was larger in ECTS images in all cases (range: + 0.14 mm to + 0.28mm). The three smallest fracture gaps were not seen on SCTS images. A subtle hypoattenuating streak (artefact) was visible adjacent to the screw fracture in 5/6 of cases using SCTS images. All screw fractures occurred parallel and often slightly medial to the humeral intercondylar fissure. Conclusion Implant failure is only seen with larger fracture gaps in SCTS images, with 3/6 screw fractures not visible in SCTS compared with ECTS. A hypoattenuating streak extending perpendicular to the implant in SCTS images is suggestive of screw fracture even if this is not directly visible.

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Objectives (1) To compare the ability of standard computed tomography (CT) scale (SCTS) and extended CT scale (ECTS) images, produced using conventional CT technology, to provide detailed assessment of metal screws in vitro. (2) To assess how screw size, type, and orientation relative to the Z-axis of the gantry affect implant assessment. (3) To test the ability of SCTS, ECTS, and radiography to diagnose screw failure when there is negligible screw fragment displacement. Study design Part 1: 12 screws of different size, type, and composition were scanned in three orientations (parallel or 0°; oblique or 45°; and perpendicular or 90°) relative to the Z-axis of the gantry. SCTS and ECTS reconstructions were made for each screw, in each plane, to assess implant shape, structure, and diameter. Part 2: fatigue-failure was induced in four screws commonly used to stabilize canine humeral intracondylar fissures. Screws were then reassembled achieving grossly perfect apposition and alignment of the fragments. Ability to detect implant failure was tested using SCTS, ECTS, and radiography. Results ECTS provided better screw assessment compared with SCTS resulting in clear visualization of the structure in 8/12 versus 0/12 screws and shape in 12/12 versus 11/12 screws; however, results were affected by screw size, type, and orientation. ECTS identified all in vitro screw fractures with negligible screw fragment displacement; however, success was affected by screw orientation: 4/4 fractures identified with a 90° angle, 1/4 for 45°, and 0/4 for 0°. SCTS and radiography did not identify any of them. Conclusion The results indicate that ECTS reconstructions are useful for assessment of metal screws and for detection of nondisplaced screw fractures.