4. Outward. The only case in which the displacement is described as outward is one briefly referred to by Bryant, in which the displacement was due to arrest of the growth of the tibia following injury to its epiphyseal cartilage.

B. Dislocations of the lower end.

Of this the only two recorded cases, excluding, of course, the numerous ones in which diastasis of this joint has formed one of the lesions of Pott's fracture at the ankle and the few cases in which the same diastasis has been part of inward or outward dislocation of the foot, are one observed by Nelaton in the service of Gerdy and one in the service of Tillaux reported by Dunand.' Gerdy's patient came to the hospital thirty-nine days after the accident. The wheel of a wagon had passed across the lower end of his leg and had forced the external malleolus so far backward that it was almost in contact with the outer border of the tendoAchillis; the outer surface of the astragalus could be felt through almost its entire extent. The patient walked fairly well, and Gerdy thought no attempt to reduce should be made.

Tillaux's case resembles Pott's fracture at the ankle. The patient in stepping from an omnibus caught his foot and fell forward. The foot was everted, there was a large ecchymosis on the inner side of the leg and foot, and another on the outer side; the ankle was swollen and tender, especially on the inner side; no fracture could be found. The lower end of the fibula was freely movable forward and backward with cartilaginous crepitus, and could be drawn outward so far that the end of the finger could be inserted between it and the astragalus. The patient made a good recovery. It seems probable that this was produced by inversion of the foot, by which the upper outer border of the astragalus was turned outward, forcing the fibula away from the tibia.

SPONTANEOUS OR PATHOLOGICAL DISLOCATIONS.

These have been reported as occurring at the upper end in consequence of inflammation of the joint, of rachitic changes in the bones, and of exaggerated growth of the tibia following necrosis. In the same group may be classed the dislocation outward reported by Bryant, and quoted above, which was due to arrest of the growth of the tibia.

Malgaigne, after quoting a general description given by Cooper, according to which chronic hydrarthrosis leads to the easy displacement of the head of the fibula and to much weakness and fatigue in walking, describes a case under his own care in which this laxity of the joint existed; in certain movements of the knee the fibula was displaced backward, returning almost at once to its place with a cracking sound; the condition followed an arthritis which had produced a similar relaxation of the knee.

In a case of rachitic curvature of the leg in an infant Malgaigne thought he could recognize the head of the fibula displaced upward almost to the level of the articular surface of the tibia, and on examining the rachitic

1 Dunand Thèse de Paris, 1878, No. 217.

skeletons preserved in the Musée Dupuytren he found several examples; the displacement was upward and outward at the upper end, the lower end preserving its normal relations.

Dislocation downward of the upper end due to elongation of the tibia following necrosis was described by Parise (quoted by Malgaigne), who reported three cases. In one of them the elongation was three centimetres on the inner side of the tibia and one and a half centimetres on the outer. Malgaigne subsequently saw and reported a fourth case. The condition did not affect the functions of the limb.

4. Outward. The only case in which the displacement is described as outward is one briefly referred to by Bryant, in which the displacement was due to arrest of the growth of the tibia following injury to its epiphyseal cartilage.

B. Dislocations of the lower end.

Of this the only two recorded cases, excluding, of course, the numerous ones in which diastasis of this joint has formed one of the lesions of Pott's fracture at the ankle and the few cases in which the same diastasis has been part of inward or outward dislocation of the foot, are one observed by Nélaton in the service of Gerdy and one in the service of Tillaux reported by Dunand.' Gerdy's patient came to the hospital thirty-nine days after the accident. The wheel of a wagon had passed across the lower end of his leg and had forced the external malleolus so far backward that it was almost in contact with the outer border of the tendoAchillis; the outer surface of the astragalus could be felt through almost its entire extent. The patient walked fairly well, and Gerdy thought no attempt to reduce should be made.

Tillaux's case resembles Pott's fracture at the ankle. The patient in stepping from an omnibus caught his foot and fell forward. The foot was everted, there was a large ecchymosis on the inner side of the leg and foot, and another on the outer side; the ankle was swollen and tender, especially on the inner side; no fracture could be found. The lower end of the fibula was freely movable forward and backward with cartilaginous. crepitus, and could be drawn outward so far that the end of the finger could be inserted between it and the astragalus. The patient made a good recovery. It seems probable that this was produced by inversion of the foot, by which the upper outer border of the astragalus was turned outward, forcing the fibula away from the tibia.

SPONTANEOUS OR PATHOLOGICAL DISLOCATIONS.

These have been reported as occurring at the upper end in consequence of inflammation of the joint, of rachitic changes in the bones, and of exaggerated growth of the tibia following necrosis. In the same group may be classed the dislocation outward reported by Bryant, and quoted above, which was due to arrest of the growth of the tibia.

Malgaigne, after quoting a general description given by Cooper, according to which chronic hydrarthrosis leads to the easy displacement of the head of the fibula and to much weakness and fatigue in walking, describes a case under his own care in which this laxity of the joint existed; in certain movements of the knee the fibula was displaced backward, returning almost at once to its place with a cracking sound; the condition followed an arthritis which had produced a similar relaxation of the knee.

In a case of rachitic curvature of the leg in an infant Malgaigne thought he could recognize the head of the fibula displaced upward almost to the level of the articular surface of the tibia, and on examining the rachitic

1 Dunand Thèse de Paris, 1878, No. 217.

skeletons preserved in the Musée Dupuytren he found several examples; the displacement was upward and outward at the upper end, the lower end preserving its normal relations.

Dislocation downward of the upper end due to elongation of the tibia following necrosis was described by Parise (quoted by Malgaigne), who reported three cases. In one of them the elongation was three centimetres on the inner side of the tibia and one and a half centimetres on the outer. Malgaigne subsequently saw and reported a fourth case. The condition did not affect the functions of the limb.