CT arthrography is ideally suited for visualizing the morphology of the scapholunate ligament and the osseous structure of the scaphoid. Prerequisites are multicompartment arthrography, high-resolution CT acquisition with sub-millimeter slices, and anatomical secondary reconstruction along the SL ligament and parallel to the longitudinal axes of the scaphoid.
In the presented case, the complete rupture of the scapholunate ligament was confirmed and a scaphoid fracture was ruled out. The diagnosis was a “bone bruise”.
Discussion
Basis for the imaging and correct interpretation is the clinical examination findings. The key symptoms of a fresh scaphoid fracture are local pain when pressure is applied to the scaphoid and axial compression pain on the thumb. The key symptoms of scapholunate dissociation are increased mobility of the scaphoid, which is examined using the Watson maneuver.
The scaphoid bone is aligned at an angle of approximately 450 to the coronal and sagittal planes. This is why it appears shortened in the dorsopalmar and lateral X-ray projections, which makes it more difficult to detect fractures. In fracture diagnostics, an additional view in fist closure and maximal ulnar deviation (Stecher view) is recommended. In this view, the scaphoid is oriented parallel to the detector and is visualized in its full length.
MRI is 100% sensitive in the detection of scaphoid fractures. However, at around 60%, its specificity in distinguishing it from a bone contusion is low. This is due to the carpal restoring forces that can lead to the anatomical spontaneous repositioning of the scaphoid fragments. Only the detection of a fracture gap is conclusive evidence of a fracture in MRI.
The best way to visualize the cortical and trabecular bone structures of the scaphoid is with high-resolution CT oblique reconstructions parallel to the longitudinal axis of the MRI scan. For non-dislocated fractures, CT has a sensitivity of 95 to 98%.
CT arthrography can be used to differentiate a scaphoid fracture from scapholunate dissociation in a single procedure.
Therapy
In the case of scapholunate dissociation, dorsal capsulodesis with ligament plasty according to Cuenod is usually performed, and the carpal transit is stabilized transitorily with SL and SC guide wires for 6 weeks.
