The astragal us in this accident is carried towards and below the external malleolus (fig. 55), whilst the outer edge of the foot is turned downwards, its inner edge upwards, and the sole inwards, the tibial malleolus disappears, and is hidden at the bottom of a retiring angle formed by the inner side of the leg and foot, and the peroneal malleolus forms, with the astragalus, a salient angle rounded off on the outside. Looking only to the change of form, situation, and rela tive position of the leg and foot, we might sup pose the case one of congenital club-foot.* The luxation of the tibia outwards, with inversion of the sole of the foot, is one of the most rare and most difficult cases to explain. Its pro duction must be the result, we suppose, of co incidences rare and unusual. There may be a certain obliquity in the line of direction of the fracture coinciding with a considerable degree of resistance in the lower fragment of the fibula: thus, if we can suppose that a fracture shall traverse the tibia obliquely from above down wards, and from within outwards, so that the point of the upper fragment be directed down wards and outwards, and the lower fragment point upwards and inwards, and if to this obliquity we suppose added a certain resistance on the side of the lower fragment of the fibula, it is plain that the foot being unable to turn out wards, must be carried inwards by the action of the muscles, and with this inversion, &c. some little shortening of the limb, at least when measured on its inner side, may be ex pected.
If this accident be neglected, the cure which nature attempts is very imperfect, the ankle-joint becomes stiff and rigid (fig. 56), the interval be tween the internal and external malleolus is much increased, the latter presses heavily against the integuments, which, when the limb is much exercised, have a strong tendency to inflame and suppurate, the outer edge of the foot throughout its whole line presses the ground, whether the patient be standing or walking, while the inner edge is somewhat elevated and curved inwards. In the dissec tion of this accident, it will be found that the malleolus internus is fractured, and in general, we suppose, with the obliquity from above downwards, and within outwards, above de scribed. The deltoid ligament remains un broken, the capsular membrane is torn in front, the fibula has been found obliquely fractured, as well as the tibia, or the three ligaments which connect it to the tarsus have given way ; none of the tendons suffer, and haemorrhage to any extent in these cases seldom or never occurs, as the large arteries generally escape injury.
Enxation of the tibia and fibula forwards, and also luxation of these bones backwards from the articular pulley of the astragalus, without fracture.—In the simple and complete luxa tion of the bones of the leg forwards at the ankle-joint, (without fracture,) the articular pulley of the astragalus is placed behind the inferior extremity of the tibia, which last rests partly on the superior surface of the neck of the astragalus, and partly on the os naviculare.
In the simple and complete luxation of the tibia backwards, (without fracture,) the inferior extremity of the tibia is placed behind the arti cular pulley of the astragalus, and corresponds to the posterior part of the superior surface of the os calcis. In both these luxations, the na tural connexion with each other of the bones of the leg remains undisturbed, and the two mal leoli advance or recede together, according to the direction in which the displacement has occurred. In both, the capsular membrane and
the posterior and lateral ligaments must be ex tensively lacerated, and most of the flexor and extensor tendons, in some degree, put upon the stretch.
The luxation of the bones of the leg forwards cannot take place, but in a forced and sudden extension of the leg on the foot, when the latter being retained by some obstacle, and solidly supported, we fall backwards.
The luxation of the tibia backwards, on the contrary, cannot happen unless when the foot is strongly flexed, the toes being elevated and retained in this position, we fall forwards.
Authors have seldom failed to notice these simple luxations forwards and backwards of the bones of the leg, yet for our part, no mat ter to what source we apply for information, we cannot satisfy our minds that we can adduce a single well-marked example of luxation of the bones of the leg at the ankle-joint, unac companied by a fracture of one or both of the malleoli ; we would not, however, be under stood to deny the possibility of such an occur rence, but merely to state our conviction that such an accident must be exceedingly rare.
We have now to consider luxations of the tibia from the astragalus, forwards and back wards, when complicated with a simple frac ture of the fibula or tibia close to the articula tion : these may be complete or partial.
Complete luxation of the tibiaforwards from the articular part of the astragalus compli cated with a simple fracture of the fibula.— This accident may arise from the same causes nearly as those which may be supposed to influence the more simple luxation in the same direction ; and as we know that when the fibula is fractured near its malleolus, the pe ronTi muscles may under certain circumstances effect a luxation of the tibia inwards, so that displacement which we are now considering may be the result of the action of the gastro cnemius and soloeus. These acting on the foot, which in consequence of the fracture is no longer fixed by the malleolus externus, cause the astragalus to slip from before backwards, and the lower end of the tibia forwards, and move the lower fragment of the fibula in such a manner that its malleolar extremity is carried backwards, and the upper part forwards. This action of these muscles, however, only pro duces a very incomplete dislocation whenever the internal malleolus is uninjured, or the foot in this case being carried outwards and back wards at the same time; but when, as often happens, either the internal malleolus or del toid ligament is broken, this displacement may be as complete and direct as the simple dis location forwards of the tibia. We then find the foot lengthened behind and shortened in front; a semicircular excavation occurs in the former direction, and an osseous tumour raises the tendons and ligaments on the front of the ankle, but it is to be particularly remarked that, whilst in the simplest form of luxation of the tibia, i. e. where there is no fracture, the external malleolus follows the tibia and fibula, and forms a projection corresponding to that of the internal, it is in this case dragged backwards with the foot to which it is attached by the lateral ligaments, and no longer has the same direction as the bones of the leg.