258 THE ARTICULATIONS. 



can be rotated in the upper radio-ulna r joint, carrying the hand with it. The 

 hand is directly articulated to the lower surface of the radius only, and the concave 

 or sigmoid surface on the lower end of the radius travels round the lower end of 

 the ulna. The latter bone is excluded from the wrist-joint (as will be seen in the 

 sequel) by the interarticular fibro-cartilage. Thus, rotation of the head of the 

 radius round an axis which passes through the centre of the radial head of the 

 humerus imparts circular movement to the hand through a very considerable arc. 



Surface Form. If the forearm be slightly flexed on the arm, a curved crease or fold with 

 its convexity downward may be seen running across the front of the elbow, extending from one 

 condyle to the other. The centre of this fold is some slight distance above the line 01 the joint. 

 The position of the radio-humeral portion of the joint can be at once ascertained by feeling for a 

 slight groove or depression between the head of the radius and the capitellum of the humerus at 

 the back of the articulation. 



Surgical Anatomy. From the great breadth of the joint, and the manner in which the 

 articular surfaces are interlocked, and also on account of the strong lateral ligaments and the 

 support which the joint derives from the mass of muscles attached to each condyle of the 

 humerus, lateral displacement of the bones is very uncommon, whereas antero-posterior disloca- 

 tion, on account of the shortness of the antero-posterior diameter, the weakness of the anterior 

 and posterior ligaments, and the want of support of muscles, much more frequently takes place, 

 dislocation backward taking place when the forearm is in a position of extension, and forward 

 when in a position of flexion. For, in the former position, that of extension, the coronoid pro- 

 cess is not interlocked into the coronoid fossa, and loses its grip to a certain extent, whereas the 

 olecranon process is in the plecranon fossa, and entirely prevents displacement forward. On 

 the other hand, during flexion, the coronoid process is in the coronoid fossa, and prevents 

 dislocation backward, while the olecranon loses its grip and is not so efficient, as during exten- 

 sion, in preventing a forward displacement. When lateral dislocation does take place, it is gen- 

 erally incomplete. 



Dislocation of the elbow-joint is of common occurrence in children, far more common 

 than dislocation of any other articulation, for, as a rule, fracture of a bone more frequently 

 takes place, under the application of any severe violence, in young persons than dislocation. In 

 lesions of this joint there is often very great difficulty in ascertaining the exact nature of the 

 injury. 



The elbow-joint is occasionally the seat of acute synovitis. The synovial membrane then 

 becomes distended with fluid, the bulging showing itself principally around the olecranon pro- 

 cess ; that is to say, on its inner and outer sides and above, in consequence of the laxness of the 

 posterior ligament. Occasionally a well-marked, triangular projection may be seen on the outer 

 side of the olecranon, from bulging of the synovial membrane beneath the Anconeus muscle. 

 Again, there is often some swelling just above the head of the radius, in the line of the radio- 

 humeral joint. There is generally not much swelling at the front of the joint, though sometimes 

 deep-seated fulness beneath the Brachialis anticus may be noted. When suppuration occurs the 

 abscess usually points at one or other border of the Triceps muscle ; occasionally the pus 

 discharges itself in front, near the insertion of the Brachialis anticus muscle. Chronic synovitis, 

 usually of tubercular origin, is of common occurrence in the elbw-joint : under these circum- 

 stances the forearm tends to assume the position of semi-flexion which is that of greatest ease 

 and relaxation of ligaments. It should be borne in mind that should ankylosis occur in this or 

 the extended position, the limb will not be nearly so useful as if ankylosed in a position of rather 

 less than a right angle. Loose cartilages are sometimes met with in the elbow-joint, not so 

 commonly, however, as in the knee ; nor do they, as a rule, give rise to such urgent symptoms, 

 and rarely require operative 'interference. The elbow-joint is also sometimes affected with 

 osteo-arthritis, but this affection is less common in this articulation than in some other of the 

 larger joints. 



Excision of the elbow is principally required for three conditions : viz. tubercular arthritis, 

 injury and its results, and faulty ankylosis ; but may be necessary for some other rarer condi- 

 tions, such as disorganizing arthritis after pyaemia, unreduced dislocations, and osteo-arthritis. 

 The results of the operation are, as a rule, more favorable than those of excision of any other 

 joint, and it is one, therefore, that the surgeon should never hesitate to perform, especially in 

 the first three of the conditions mentioned above. The operation is best performed by a single 

 vertical incision down the back of the joint, a transverse incision, over the outer condyle, being 

 added if the parts are much thickened and fixed. A straight incision is made about four 

 inches long, the mid-point of which is on a level with and a little to the inner side of the tip of 

 the olecranon. This incision is made down to the bone, through the substance of the Triceps 

 muscle. The operator with the point of his knife, and guarding the soft parts with his thumb- 

 nail, separates them from the bone. In doing this there are two structures which he should 

 carefully avoid: the ulnar nerve, which lies parallel to his incision, but a little internal, as 

 it courses down between the internal condyle and the olecranon process, and the prolongation of 

 the Triceps into the deep fascia of the forearm over the Anconeus muscle. Having cleared the 

 bones and divided the lateral and posterior ligaments, the forearm is strongly flexed and the 

 ends of the bone turned out and sawn off. The section of the humerus should be through 



