[Optimization of conventional X-ray images for the detection of hook of hamate fractures].

Fractures of the hook of the hamate are a rare event. The fracture cannot always be detected clinically and standard radiographs do not always provide an overlap-free image of the hook of the hamate, so that fractures can easily be overlooked. The objective of the present study was to examine if the sensitivity of detecting hamulus ossis hamati fractures can further be improved by a modified conventional radiographic projection. After dissection of the hook of the hamate on 10 cadaver hands, a fracture was produced close to the base using a surgical chisel. Conventional radiographs were then performed in four different projections (dorso-palmar, lateral, carpal-tunnel and oblique view). The oblique view was obtained in a 45 degrees supination position, slight extension and radial duction, with the tube tilted from distal to proximal by 30 degrees. An axial spiral CT was used as a reference for detection of the fracture. The highest sensitivity of the conventional radiographs, with 8/10 identified fractures (80%), was achieved by the oblique view. The carpal-tunnel view with 4/10 (40%) and the dorso-palmar projection with 3/10 (30%) were much lower. All fractures were missed in the lateral projection. If all of the conventional radiographic projections are taken into account, the sensitivity is increased to 90%. All of the fractures were reliably detected in the axial CT-image. If a hamulus ossis hamati fracture is suspected clinically, in addition to the dorso-palmar and carpal-tunnel view, the special oblique view described here should be performed as a third projection plane, while the lateral view can be dispensed with. However, even if all projections are taken into account, a negative finding in the conventional radiographic imaging does not exclude a fracture with absolute certainty. In such cases, a CT or MRI should be performed to exclude a fracture.