The pain and inability to walk, the sudden effusion around the injured ankle, the ecchy mosis, tenderness of the skin and tension, the signs of this injury expressed by the living structures, are all accounted for by the lesions which an anatomical examination of these in juries of the ankle-joint discovers. This also explains what practical writers have noted of sprains, viz. that sometimes the ankle-joint which has been affected by this accident, rapidly and perfectly recovers,—that, on the other hand, it is_not unfrequently so weakened by the injury, as to become peculiarly suscep tible of a renewal of the sprain from slight causes; sometimes the articulation contracts a rigidity, by which for a time, or even for life itself, its proper functions are interfered with, and a permanent oedema of the soft parts around the joint is too often in these cases established.
Bones. — The bones which contribute to form the ankle-joint are liable to fracture and to luxation. These bones, we know, are the tibia, fibula, and astragalus; for an account of the accidents which affect the latter particularly, we refer to the article FOOT, and shall here, as succinctly as we can, notice the various dis placements of the bones of the leg at the ankle-joint, which have been observed to be the result of a fracture through one or both of the malleoli, or of an accidental rupture of the ligaments which tie these eminences to the foot.
When we reflect on the great strength of the ligaments which connect the astragalus to the tibia and fibula, and the support which the ar ticulation derives from the prolongation down wards of the malleoli, we can easily perceive that a luxation of the foot must be the effect only of some very violent cause, and that this accident can very rarely (in a true sense) be a simple one. Effusions of blood, rupture of all the surrounding ligaments, fracture of the external or even of both the malleoli, wounds of the soft parts, and even protrusion of the bones, are contingences which frequently render the dislocation of the tibia at the ankle-joint a very complex accident.
The most superficial view of the structure of the ankle-joint will convince any one that no lateral displacement of the bones of the leg can occur, without its having been im mediately preceded by a fracture of either the tibial or peronmal malleolus ; but such a view would warrant the conjecture, that a luxation in the direction forwards or backwards may possibly take place, simply from the rupture of the ligaments of the joint alone, and the action of muscles. Such a luxation as this last, when no fracture exists, should be best entitled to the name of simple ; yet those luxations of this articulation (such is the vagueness of surgical language), whether ac companied with fracture or not, are all called simple, provided there be no wound through the integuments communicating with the cavity of the joint. In this latter case alone the luxation is denominated compound, of which it is not our intention here to treat.
We shall arrange the luxations of the bones of the leg at the ankle-joint in the above sense called simple luxations, into those which occur in the direction inwards, outwards, forwards, and backwards, and each of these, it is be lieved, may be a partial or a complete lux ation.
Luxation of the Tibia inwards.—This luxa tion may be complete or incomplete : we shall first treat of the most common form of it or that termed partial Dislocation of the Tibia inwards from the Astragalus, or Pott's luxation. Mr. Pott, in describing this accident, observes, " that the support of the body, and the due and proper use and execution of the office of the joint of the ankle, depend almost entirely on the perpendicular bearing of the tibia upon the astragalus, and on its firm connexion with the fibula. If the former bone is forced from its just and perpendicular position on the astragalus ; or, if it be separated by violence from its connexion with the latter, the joint of the ankle will suffer a partial luxation inter nally : this is the case when, by leaping or jumping, the fibula breaks in its weak part, within two or three inches of its lower ex tremity. When this happens, the inferior frac tured end of the fibula falls inwards towards the tibia, that extremity of the bone which forms the outer ankle is turned somewhat out wards and upwards, and the tibia, having lost its proper support, and not being of itself capable of steadily preserVing its true perpendicular bearing, is forced off from the astragalus, in wards, by which the ligaments are torn, thus producing a perfect fracture and a partial dis location." =" If we are called to examine a patient wlio has recently suffered this accident, we find that the ankle-joint now possesses some degree of lateral mobility. In the normal state of the ankle-joint we know that the quadrilateral cavity formed by the tibia and fibula for the reception of the astragalus, makes with the latter a perfect mortise joint, which admits of motions of flexion and extension, but allows of no motion whatever laterally or horizontally ; for it must be recollected that those motions of inclination of the foot, known under the names of adduction and abduction, are not movements in the ankle-joint, but take place in the joints of the tarsus : but the un natural mobility in question is very great when the fibula is broken at its lower part; this is shewn, when, after the surgeon has bent the limb to relax the muscles, the leg is fixed by one hand placed at its lower extremity, whilst the other moves the foot from within outwards; the foot is then seen to move in a transverse line and to quit the axis of the leg; the mal leolus internus projects inwards, and the mal leolus externus is moved upwards and out wards, and all these appearances vanish, when by a contrary movement we bring the foot to its natural position.