LUXATION. 



tend his arm. HowcTer, in fome cafes, efpccially in young 

 perfons, fome motion is acquired in lime ; the hcado of tin; 

 radius and ulna making in the humeius cavitii :s, in which 

 they perform fome motionp, but always imperfectly. 



The luxation forwards ftiould be treated as a frafture of 

 the olecranon, with whicli it would be inevitably accom- 

 panied. It may be neccfikry, on account of the great in- 

 jury done to the foft parts, to bleed the patient copioufly, 

 and put him on an ar,tipl,lngiltic regimen. 



As to the lateral luxations, cither inwards or outwards, 

 they are always incomplete, and eafiiy difcovered. They 

 are reduced by drawiii^' the humerus and fore-arm in con- 

 trary directions, and at the fame time pudiing the extre- 

 mity of the humerus, and the two bones of the fore arm in 

 oppofite direAions. 



Thefe luxations cannot be produced without confiderable 

 violence ; b':t when the bones are reduced, they are eafiiy 

 kept in their place. It will be fufficiert to pafs a roller 

 round the part, to put the fore-arm in a middle Rate, neither 

 inuch bent nor extended, and to fupport it in a Ihng. ■■ But 

 much inflammation is to be expefted from the injury done to 

 the foft part?. In order to prevent it, or at leuft mitigate 

 it, the patient is to be bled t\ro or three times, and put on 

 a low diet, and the articulation is to be covered with the 

 iotio aq. litharg. acet. It is fcarcely neceflary to repeat, 

 that the arm is to be moved as foou as the ftate of the foft 

 parts will admit of it. 



The dillocation of the fore-arm backward, is faid to 

 occur ten times as frequently as lateral luxations; and thofe 

 forward are fo rare, that no comparifon whatever can be 

 drawn. Qiuvres Chir. de Default, tom. i. 



Lateral luxations have been divided into complete, that is, 

 when the articular fnrfaces have entirely loft their ftate of 

 reciprocal crntacl ; and into incomplete, that is, when only 

 one bone, or a part of it, is thrown off the humerus. But 

 what caufe can operate with fufficient force to produce the 

 firft occurrence? The miichief would alfo be fo great, 

 were fuch a cafe to happen, that amputation would moft 

 likely be requilite. 



The incomplete lateral luxation may be produced by a 

 blow, which drives the upper part of the fore-arm violently 

 outward, or inward. A footman, fays Petit, in falling 

 from a cnach, had his arm entangled in the fpokcs of a 

 wheel, and a dillocation outward was the confequence. 

 Another man luxated his fore-arm inward, by falhng from 

 his horfe and driving his arm againit an uneven place. 



When the ulna is puflied into the fituation of the radius, 

 the fpace between the olecranon and internal condyle is 

 much greater than is natural. Thele points of bone are 

 always very diftinguiihable, let the joint be ever fo much 

 fwoUen ; and hence, the information to be derived from an 

 examination of thein, may be obtained in every cafe, with- 

 out exception. Alfo, when the ulna is pufhed into the 

 place of the radius, the latter bone cannot be eafiiy rotated, 

 nor can the fore -arm be bent and extended in a perfeft 

 manner. 



The dillocation inward muft be very uncommon, as the 

 form of the bones is almoft an infurmountable obftacle to 

 fuch an accident. It may happen, however, as the autho- 

 rity of Petit confirms. 



All recent diflocations of the elbow are very eafiiy re- 

 duced, and as eafiiy maintained fo ; for the reciprocal man- 

 ner in which fhe articular furfaces receive each other, and 

 tlieir mutual eminences and cavities, will not readily allow 

 the bones to become difplaced again. 



The application of a bandage in the form of a figure of S, 



and fupportlng the arm in a fling, are proper in ail thcfe 

 cafes. 



huxallon Iff the Radius from the Ulna The majority of 



authors, who have written on diflocations of the fore-arm, 

 have not feparately confidered thofe of the radius. Some 

 detached obfervationv, on luxations of its fuperior extre- 

 mity, arc to be found here and there ; a fub;ect which Du- 

 verney alone has fully treated of. The diflocations of its 

 lower and, which are more frequent, and eafy of occurrence, 

 have almoll efcaped the notice of French, and alfo Enghfh 

 writers. At prefent, cafes of this fort have been fo nu" 

 ineroufly coUedled, that a particular account of thtm may- 

 be oftered. 



lYtffcrenee of Strudiire, l/ettveen the two Joints of the Radius 

 with the Ulna. — The radius, the moveable agent of prona- 

 tion and fupination, rolls round the ulna, which forms its 

 immoveable fupport, by means of two articular furfaces ; 

 one above, flightly convex, broad internally, narrow out- 

 wardly, and correfponding to the little figmoid cavity of 

 the ulna, in wiiith it is lodged ; the other below, concave,, 

 femi-circular, and adapted to receive the convex edge of the 

 ulna. Hence there are two joints, differing in their mo- 

 tions, articular furfaces, and ligaments. By afcertaining 

 fuch differences, w-e fliall be enabled to find out thofe 

 which exift between the luxations of the upper and lower 

 head of the radius. 



Above, the radius, in pronation and fupination, only- 

 moves OH its own axis ; below, it rolls round the axis of the 

 ulna. Here, being more diilant from the centre, its mo- 

 tions muft be botli more extenfive and powerful than they 

 arc above. The head of the radius, turning on its own axis 

 in the annular ligament, cannot diftend it in any direction. 

 On the contrary, beloiv, the radius, in pcrforrring pronation, 

 ftretchcs the pofterior part of the capfule, and preffes it 

 again ll the immoveable head of the ulna, w-hich is apt to be 

 pulhed through, if the motion be forced. A fimilar event, 

 in a contrary fenle, takes place in fupination. The front 

 part of the caplule, being rendered tenfe, may now be 

 lacerated. 



Add to this difpofition, the difference of ftrength between 

 the ligaments of the two joints. Delicate and yielding 

 below ; thick and firm above ; their difference is very great. 

 The upper head of the radius, fjpported on the fmaller im- 

 moveable articular furface of the ulna, it protefled from 

 dillocation in moft of its motions. On the contrary, its . 

 lower end, carrying along with it in its motions the bones 

 of the carpus which it lupports, cannot itfelf derive any 

 folid ftability from them. 



Di'/trences of Luxiilions of the Radius. — From what has 

 been faid, the following conclulions may be drawn ; i, that 

 with more caufes of luxation, the lower articulation of the 

 radius has lefs means of refiftance ; and, that under the 

 triple confideration of motions, ligaments tying the articu- 

 lar furfaces togetlier, and the relations of thele furfaces to 

 each other, this joint mull be very fubjeCt to diflocation. 

 2. That, for oppofite reafons, the upper joint cannot be 

 very fubjeit to fuch an accideiit. 



Indeed what could be the caufe producing it in this fitua- 

 tion ? Can it arifc from a violent pronatian, or fupination J 

 The lower joint being the weakeft -.vould give way the firft, 

 and however forcible any motion of this kind might be, the 

 upper head of the radius w-ould only be rotated on its own 

 axis. How then can this part be d.flocatcd without being 

 pufhed forward or backward? All the mufcular and liga- 

 mentous fupport ot the joint muft be br<'keii ; and the muf- 

 cles and ligaments are t( o ftrong to admit of this, and ths 

 motion iilclf too feeble. Can the accident originate from 

 4 R 2 any 



