ABSTRACT:The contact areas between the articular surfaces of the talus and tibia are essential for understanding the mobility of the ankle joint. The purpose of our study was to reveal the contact area among the superior articular surface of the trochlea tali (target surface T) and the inferior articular surface of the tibia (query surface Q) under non-weight-bearing conditions in plantar flexion and dorsiflexion. Twenty cadaveric foot specimens were dissected and scanned by a three-dimensional (3D) laser scanner to obtain data point sets. These point sets were triangulated and a registration procedure performed to avoid any intersection of the two joint surfaces. For all points of the query surface Q, the closest distance to T was measured. In 11 of the 20 ankle joints, the contact area was larger in plantar flexion, in 5 it was nearly of equal size, and in 4 the two surfaces were found in a better congruence in dorsiflexion. The two articular surfaces can be in point or line contact and cause different motions while T is gliding on Q, so the original geometry of ligaments must be carefully reconstructed after injury or during total ankle replacement. ß
The lateral articular facet of the talus (Facies malleolaris lateralis) is slanting and irregulary shaped; therefore, the fibula shows compensative motions in transverse, sagittal, vertical and rotational directions when the ankle joint is moved. There are contradictory statements concerning the course of this compensative rotation, because the fibula shows individually different reactions. The fibula is not rotated during dorsiflexion in nearly 25% of legs; approximately one half of the remaining fibulae is rotated outward, the other half inward. This matter of fact is not surprising, when the shape of the lateral articular facet is inspected exactly: it resembles a flat saddle, the anterior part of which is screw-shaped. The fibula rotates outward during dorsiflexion, if the furrow of this screw-shaped area increases forward; it totates inward, if the furrow diminishes forward; and it does not rotate at all, if the furrow is constant.
Brainstem auditory evoked potentials were recorded in a 3-year-old girl with the central alveolar hypoventilation syndrome (Ondine's syndrome). Abnormal findings were seen at the level of the mid to upper brain stem (wave III), which was not reproducibly recordable on the left side. This electrophysiologic abnormality is consistent with a previous finding in a patient with sleep apnea.
The metacarpophalangeal joint of the human thumb (Articulatio metacarpophalangea pollicis) is an ellipsoidal (condyloid) joint. The head of the first metacarpal bone is shaped like a spindle polled at either end. Its form relevant to the mobility is determined by the correlation of two flexures, expressed by the quotient R/r, where R = semi-diameter of the radio-ulnar flexure and r = semi-diameter of the dorso-palmar flexure in the middle of the head. Only the substantial kind of motion (flexion – extension) maintains the perfect contiguity of the articular surfaces. Owing to the deformability of the articular cartilage, the actual littleness of the articular surfaces as well as the relative smallness of the cavity with respect to the head permits both transverse motions (adduction – abduction) and axial motions (rotation inward and outward). The amplitude of the transverse motion unexpectedly does not correlate to the intensity of the radio-ulnar flexure of the head.
Brainstem auditory evoked potentials (BAEPs) were recorded in 14 artificially ventilated patients (12 males, 2 females; mean age 33.3 +/- 16.3 years, range 18-67) with respiratory insufficiency resulting from severe inflammatory encephalopathies. The results were compared with those of 17 healthy volunteers (13 males, 4 females; mean age 27.4 +/- 5.3 years, range 21-45). BAEPs in the study patients showed prolonged interpeak latencies (I-III, I-V, III-V, IV-V) and delayed absolute latencies of waves I, II, III, and V at least on one side. Because the auditory pathways are in the near vicinity of the respiratory control centers in the brainstem, the electrophysiologic abnormalities of wave III and the IV/V complex may be a reflection of the disturbed central control of ventilation.
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