Dorsal dislocation of the ulnar styloid and extensor carpi ulnaris tendon into the distal radioulnar joint: the empty sulcus sign

Two cases of distal radioulnar joint (DRUJ) disruption and diastasis secondary to distal radial fractures were associated with displacement of the ulnar styloid and extensor carpi ulnaris (ECU) into the DRUJ. Both cases had a palpable empty ECU tendon sulcus. In one case surgical exploration revealed that the ulnar styloid, triangular fibrocartilage, and extensor carpi ulnaris tendon had dislocated into the DRUJ as a unit. The end result was good. In the second case lack of recognition and reduction of the ECU tendon and ulnar styloid led to persistent subluxation and diastasis. The end result was poor. Early recognition of the dislocation of the ulnar and ECU into the DRUJ and their significance may avoid poor results.     

Lung vascular smooth muscle as a determinant of pulmonary hypertension at high altitude.

The pulmonary hypertensive response to chronic hypoxia varies markedly among mammalian species. An explanation for this variability was sought by exposing seven species to hypobaric hypoxia (PB equal to 435 mmHg) for 19-48 days. Control animals were studied at 1,600 m (PB equal to 630 mmHg). The pulmonary hypertension that developed varied in the following order of decreasing severity: calf and pig (severe); rat and rabbit (moderate); sheep, guinea pig, and dog (mild). Right ventricular hypertrophy developed in proportion to the elevation in right ventricular systolic pressure. These interspecies variations in response were not correlated with the degree of arterial hypoxemia, degree of polycythemia, elevation in heart rate, or postnatal age. However, the medial thickness of the small pulmonary arteries in control animals was highly correlated with the development of pulmonary hypertension and right ventricular hypertrophy in hypoxic animals. Thus, the amount of lung vascular smooth muscle inherent within each species is a major determinant of the pulmonary hypertensive response to high altitude and contributes to the interspecies variability in this response.