ABNORMAL CONDITION OF THE ANKLE-JOINT. 



159 



malleolus interims 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. 



Luxation 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 tibia forwards 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- 

 ronaei 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 solaeus. 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. 



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 



* The weight that so justly attaches to any ob- 

 servations from Sir A. Cooper, induced us to con- 

 sider well the account he gives of the dissection of 

 this complete luxation of the tibia forwards, in his 

 work on Dislocations and Fractures ; and we find 

 that we cannot reconcile it with our ideas of the 

 anatomy of the injury. We are sorry in this in- 

 stance to be obliged to differ from an authority, 

 to which we feel indebted for many observation^ 

 copied into these pages ; but we think there must 

 be error in the following passage taken from the 

 valuable work to which we allude, page 178, 8th 

 edition. 



" On dissection, the tibia is found to rest upon 

 the upper surface of the os naviculare and os cunei- 



