Anatomic Landmarks of the Distal Radioulnar Joint.

HYPOTHESIS: Using Lister's tubercle and the ulnar styloid as landmarks, accurate localization of the distal radioulnar joint can be achieved without the need for an image-guided approach. METHODS: Cadaveric dissection of 16 upper extremities was performed to measure the relationships between the ulnar styloid, Lister's tubercle, and the distal radioulnar joint. In each specimen, the location of the distal radioulnar joint (point A) in relation to Lister's tubercle and the ulnar styloid was determined as follows: (1) the perpendicular distance between the distal radioulnar joint and ulnar styloid-Lister's tubercle was measured; (2) with A' marking the intersection of this distance and the ulnar styloid-Lister's tubercle line, the location of the distal radioulnar joint along the ulnar styloid-Lister's tubercle axis was determined by comparing ulnar styloid-A' and A'-Lister's tubercle with ulnar styloid-Lister's tubercle. RESULTS: The mean distance between ulnar styloid-Lister's tubercle was 4.3 ± 0.4 cm. The mean perpendicular distance between the distal radioulnar joint and the ulnar styloid-Lister's tubercle line was 0.2 ± 0.1 cm proximal to the ulnar styloid-Lister's tubercle line. The ratio of ulnar styloid-A' and A'-Lister's tubercle to ulnar styloid-Lister's tubercle was 0.5 ± 0.03 and 0.5 ± 0.03, respectively. CONCLUSIONS: Simple relationships between the ulnar styloid and Lister's tubercle serve as reliable landmarks for locating the distal radioulnar joint. The distal radioulnar joint is centered about the midpoint of the ulnar styloid-Lister's tubercle axis and slightly proximal to it. This may improve the accuracy and efficacy of corticosteroid injections in the treatment of distal radioulnar joint arthritis without the need for image guidance.

Independently switchable atomic quantum transistors by reversible contact reconstruction.

The controlled fabrication of actively switchable atomic-scale devices, in particular transistors, has remained elusive to date. Here, we explain the operation of an atomic-scale three-terminal device by a novel switching mechanism of bistable, self-stabilizing reconstruction of the electrode contacts at the atomic level: While the device is manufactured by electrochemical deposition, it operates entirely on the basis of mechanical effects of the solid-liquid interface. We analyze mechanically and thermally stable metallic junctions with a predefined quantized conductance of 1-5 G0 in experiment and atomistic simulation. Atomistic modeling of structural and conductance properties elucidates bistable electrode reconstruction as the underlying mechanism of the device. Independent room temperature operation of two transistors at low voltage demonstrates intriguing perspectives for quantum electronics and logics on the atomic scale.