Although this species of luxation has not been specially described in any of our English works, I doubt not but such an accident has been observed, although it is possible that its nature was not always clearly understood. Sir A. Cooper, in his valuable work on Disloca tions and Fractures, states that the foot has also been known to be thrown upwards, between the tibia and fibula, by the giving way of the ligament which unites these bones ; but he adds that this accident is only an aggravated form of an internal dislocation.
We find but little difficulty in comprehend ing how the accident described by Dupuytren may occur, because, the fibula having been first fractured, the broken bone and ruptured ligaments permit the foot to yield to the powerful action of the muscles on the back part and outside of the leg, which draw it at first outwards, and then upwards ; but on the contrary, it is not easy to imagine any force capable of overcoming the resistance of the many inter-osseous ligaments which exist, and of the fasciae and annular membranes which surround the bones of the leg : a force must be great indeed which can overcome the muscles also, and cause a divarication of the bones of the leg sufficient to permit the astragalus and rest of the foot to be thrown upwards between the tibia and fibula. Supposing this last case pos sible, the shortening of the limb and its newly acquired breadth between the malleoli might lead to error, and the two cases here alluded to be at first sight confounded ; but in Dupuy tren's case, the fracture of the fibula, the over lapping of its fragments, and above all the ascent of the external malleolus, so much above the level of the internal, will always constitute such characteristic marks, that when such an accident presents itself, we conceive it cannot be confounded with any other injury of this articulation.
What are the anatomical characters of this complete luxation of the tibia inwards, with displacement of the foot and outer malleolus upwards and outwards ? It is evident that there must be very extensive injury done in such cases to the ligaments and bones ; the fibula must he fractured near the ankle, and it is probable that some fragments of the tibia may be carried off with the fibula, for such is the strength of the ligaments between the lower part of the tibia and fibula, where these unite for the reception of the astragalus (vid. jig. 61), that there is reason to believe that the bone itself would break before the ligaments would yield.
If a portion of the tibia, however, is not broken off and carried with the fibula, these transverse fibrous bands must be torn, as well as those oblique •ligaments which pass before and be hind from the fibula to the tibia. The proper interosseous membrane itself must be detached from between the bones to allow the astragalus to ascend along the outside of the tibia. While the ligaments which connect the outer malleolus to the tibia must be torn, those which unite it to the foot remain entire, the deltoid or internal lateral ligament must be completely torn across, as well as the synovial sac of the articula tion ; nor should it be forgotten that the annu lar ligaments and strong fasciae at the lower part of the leg, must, in so severe and ex tensive an injury, be lacerated ; the tendons, muscles, and other structures may escape injury, the astragalus and outer malleolus are dragged up (fig. 54, a, b), their ascent being only limited by the lower point of the upper fragment of the fibula (c), which remains in its natural relation to the tibia, except that it must be somewhat approximated to it; the lowest point of the superior fragment of the broken fibula rest upon the summit of the articular pulley of the astragalus, as is well seen in a preparation preserved in the collection of St. Thomas's Hospital Museum, the delineation of which we have borrowed from Sir A. Cooper's work. The preservation of this specimen, which in our mind is a true example of the complete dislo cation of the tibia inwards, and of the external malleolus astragalus and foot upwards and outwards, is a new proof of the truth of the observation we have above made, that this severe accident had not altogether escaped the notice of English surgeons, although the 44 Annuaire" contains the first accurate account of the external signs by which it may be recog nized in the living subject.
Luxation the tibia outwards, complicated with simple fracture of one or both of the mal leoli.—This, it is said, is one of the most dan gerous of the dislocations to which the ankle is liable, for its production has been noticed to be attended with greater violence, and to be accompanied by more contusion of the integu ments, more laceration of ligaments, and greater injury to bone, than we have occasion to ob serve in the production of the other luxations of this joint.