Visibility of Transcondylar Screw Fractures in Standard and Extended Scale Computed Tomography Images

Abstract

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.

Keywords

computed tomography - screw fracture - dog - humeral intracondylar fissure - transcondylar screw

Authors' Contributions

R.B. designed study and acquired and interpreted data; he was lead author; he critically reviewed and gave final approval of the manuscript (accepting accountability for its contents). J.L. was involved in study design; data interpretation, critical review and final approval of the manuscript (accepting accountability for its contents). A.H. was involved in study conception and design; data acquisition and interpretation; critical review and final approval of the manuscript (accepting accountability for its contents).

Publication History

Received: 20 September 2021

Accepted: 17 November 2021

Article published online:
31 December 2021

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