In the dislocation forwards of the tibia (whether simple or complicated with a frac ture of the fibula) from the astragalus, the articular pulley of this bone is placed behind the inferior articular cavity formed for it in the tibia ; but this latter bone at the same time, it will be recollected, must now rest on the dor sum of the tarsus, where it is formed by the upper part of the neck of the astragalus and os navi culare. When the tibia has thus once advanced before the articular pulley of the astragalus, the luxation forwards is as complete as it well can be; in our opinion, to imagine any more com plete luxation of the tibia forwards, we should be obliged to presume that this bone in its advance on the dorsum of the foot had com pletely cleared the astragalus, and then rested " on the os naviculare and os cuneiforme in ternum,"* which last form part of the anterior range of the tarsus, a situation which the tibia could not well occupy, without a previous lesion of the tendons of the tibialis anticus, and stretching of the other extensors : from such a relative position of the bones of the leg and foot would result a shortening of the dorsum of the foot and an elongation of the heel to an extent which, we believe, has never been no ticed.
Partial luxation of the tibia with simple of one or both cf the nu:Ileoli. —The complete luxation forwards of the tibia from the astragalus, which we have described, in the preceding section, all writers look upon as the more common form of dislocation for wards ; while the partial luxation in this di rection is considered a rare accident. My opinion upon this subject is quite different ; for some experience in these accidents leads me to say, that a complete luxation of the tibia forwards from the articular pulley of the astra galus is rare, but that a partial luxation in this direction accompanied with a simple fracture of one or both of the malleoli, is an accident by no means uncommon.
The signs of this partial luxation of the tibia forwards are nearly the same as those we have stated to belong to the complete luxation in this direction ; they are, however, as might be expected, more faintly marked, and, conse quently, may more easily be neglected ; but, after all, these signs are so evident, that it is wonderful how with common attention they can be overlooked. It may not be amiss to subjoin the following case as illustrative of the common partial luxation forwards : A man, aged twenty-two years, was ad mitted into Jervis - Street Hospital, at three o'clock, A.M. of the 26th of December, 1833. He stated that he and had been drinking together in a public house, that in the middle of the night they quarrelled, that he was knocked down, and was unable to rise, in consequence of his having received a severe injury of his left ankle : his friend then pro cured some assistance and carried him to the hospital; at my visit, I found him in bed, complaining of much pain, his leg extended and resting on its outer side; the heel was re tracted, and between it and the calf of the leg, instead of the ordinary line which marks the course of the tendo Achillis, there was a conspicuous semicircular curve, (fig. 57, a, h);
in a word, the heel was lengthened, and the dorsum of the foot seemed much shortened ; in the situation of the ankle-joint in front, there Was a remarkably hard, prominent, trans verse ridge made by the advance of the lower extremity of the tibia and extensor muscles of the toes, while beneath this there was a marked depression, where the skin and annular liga ment seemed, as it were, pinched in, drawn under the lower edge of the articular part of the tibia ; the foot was pointed downwards, no movement of flexion or extension could be communicated to the ankle-joint, but it ad mitted of some little motion in a horizontal, and also in a lateral, direction, when the leg was firmly grasped with one hand and the foot moved with the other.
It was remarkable that, although the man had no power whatever over the motions of the joint, he could, while he lay in bed, move his whole limb about with much freedom, and (as there was probably a locking of the bones with each other) these voluntary movements were not accompanied by any increase of pain.
The fibula could be felt to be fractured about an inch and a half above the lowest point of the outer malleolus, " the foot, the outer malleolus, and short portion of the broken fibula, formed one system of parts," and were carried for the length of an inch or more horizontally backwards, while there was a projection forwards, of the lower articular part of the tibia, and the internal malleolus itself was advanced in the same proportion : it is to be observed, that there was no crepitus, because it was the deltoid ligament only which was torn ; the tibia was not broken, and the ends of the fractured fibula were evidently far separated from each other. When the luxation was reduced, which was effected with out much difficulty, crepitus could be felt, proving the restoration to its place of the lower fragment of the fibula.
This is a species of fracture and luxation, which can, by proper management, be readily redressed, and no deformity remains, if time be not lost after the accident has occur red ; but if the fibula become solidly united in its new situation, the motions of the ankle joint are for ever lost, and the patient is doomed to lameness for life.