ABNORMAL CONDITION OF THE ELBOW-JOINT. 



71 



(liable ; th patient for ever loses the power of 

 fully Hexing the fore-arm, and the muscles of 

 the arm become more or less atrophied ; the 

 powers of pronation and supination also become 

 unpaired, but extension of the elbow-joint can 

 be performed. 



Sir A. Cooper had an opportunity of dissect, 

 ing a compound luxation of the elbow-joint, HI 

 which the radius and ulna were thrown back- 

 wards, and the specimen is preserved in the 

 Museum of St. Thomas's Hospital, and a re- 

 presentation given in his work on dislocations : 

 see plate xxiii. fig. 2. The coronoid process 

 of the ulna was thrown into the posterior fossa 

 of the os humeri, and the olecranon projected 

 at the back part of the elbow, above its riatura 1 

 situation, an inch and a half. The radius was 

 placed behind the external condyle of the os 

 numeri, and the humerus was thrown forwards 

 on the anterior part of the fore-arm, where it 

 formed a large projection. The capsular liga- 

 ment was torn through anteriorly to a great ex- 

 tent ; the coronary ligament remained entire. 

 The biceps muscle was slightly put on the 

 stretch by the radius receding, but the braehia- 

 lis anticus was excessively stretched by the 

 altered position of the coronoid process of the 

 ulna. 



This was a recent case ; but it would ap- 

 pear from the dissections which have been 

 made of cases which had been left for a long 

 time unreduced, that a new bony cavity had 

 been made on the front of the coronoid process 

 of the ulna, while the brachialis anticus be- 

 came the seat of ossific depositions. An in- 

 teresting case of this kind is recorded by Cru- 

 veilhier, and figured by him in his Anat. Pathol. 

 plate iv. fig. 1. Beclard also met with a simi- 

 lar case in dissection. 



2. Lateral dislocation of the bones of the fore- 

 arm. Lateral dislocations of the elbow-joint are 

 rare, and this circumstance is owing to the great 

 transverse extent of the articular surfaces, to the 

 inequalities which the corresponding surface 

 of the humerus presents in the transverse di- 

 rection, to the strength of the lateral liga- 

 ments, and the attachment to them of the tendons 

 of those superficial muscles which pass to the 

 anterior and posterior part of the fore-arm, 

 which tendons almost identify themselves with 

 the lateral ligaments, and must considerably 

 strengthen and support the joint laterally. 

 Again, the force which would have a tendency 

 to luxate the bones laterally can very rarely be 

 directed in such a manner as to produce the 

 luxation we are now considering, nor are the 

 muscles ever so directed as to produce them. 



We find in authors circumstantial accounts 

 of the symptoms of the complete luxation 

 outwards and also of the complete luxation 

 inwards : but we have not had any opportuni- 

 ties ourselves of witnessing these complete luxa- 

 tions as the immediate result of accidents. 

 Indeed we can scarcely conceive any complete 

 luxation outwards to correspond exactly to the 

 description given ; as we imagine that when- 

 ever the bones of the fore-arm are completely 



thrown outwards, these bones must be drawn 



* 



Fig. 42. 



Luxation outuxirdi of both bonet of the fora-arm, 

 coruecutme to cariet of the trochlea and great 

 tit/moid cavity of the ulna. 



immediately upward along the outer side 

 of the arm. We can conceive it possible, 

 however, that the bones of the fore-arm may 

 be completely dislocated inwards from the 

 trochlea of the humerus, and still be restrained 

 from yielding to those forces which would draw 

 them upwards and inwards, by the great pro- 

 jection inwards of the internal condyle of the 

 humerus, which we know is so much more 

 prominent than the external. We could scarcely 

 mistake the case of complete lateral luxation 

 of the fore-arm, whether it was inwards or 

 outwards. 



In the incomplete lateral luxations of tin- 

 bones of the fore-arm at the elbow-joint, the 

 articular surfaces of the bones are still in con- 

 nexion, but the points of contact of their 

 naturally corresponding surfaces are altered 

 more or less as to their relative positions to 

 each other. In these luxations the bones of 

 the fore-arm may be thrown partially outwards 

 or partially inward*. In the luxation outwards, 

 the cavity of the superior extremity of the 

 radius abandons the lesser head of the humerus, 

 and its cup-like extremity may be felt beneath 

 the skin, while the great sigmoid cavity of the 

 ulna corresponds to the capitulum of the 

 huraerus from which the radius has been dis- 

 placed. As to the anatomy of the parts under 

 such circumstances, the ligaments must be all 

 torn, the biceps and triceps muscles must be 

 pulled outwards in the direction of the bones 

 of the fore-arm, into which they are inserted, 

 the supinator brevis muscle cannot escape lace- 

 ration, and the musculo-spiral nerve must be 

 more or less stretched. There must be danger 

 of such a luxation being rendered complete or 

 even compound. 



One of the most remarkable of the external 

 signs of this injury is an increase of breadth of 

 the fore-arm in the line of the articulation. There 

 is a considerable projection seen at the outer 

 side of the arm formed by the head of the radius, 

 and an angular depression immediately above 

 this. On the inner side of the arm we see the 



