ABNORMAL CONDITION OF THE ELBOW-JOINT. 



67 



notch on tlie internal side of the greater sigmoid 

 cavity, ihere ahxays occurs a mass of this sub- 

 stance from which a production extends over 

 tlic n.ii'_;h groove described above, dividing the 

 si'jiiionl e.aity tiansversely. 



The synovia] capsule adheres closely to the 

 fibrous ligaments, except where masses of adi- 

 pose tissue are interposed, to which it is but 

 loosely connected. 



Uotiont. The elbow is a joint remarkable 

 for possessing great solidity, which is partly 

 owing to the extent of its osseous surfaces and 

 the manner in which they are locked into each 

 other, and partly to the strong lateral ligaments 

 and tin muscles which surround it. 



The motions enjoyed by the elbow-joint are 

 flexion and extension. 



Flexion may vary in degree so as to be com- 

 plete or incomplete: in complete flexion the 

 fore-arm is carried forwards and inwards in an 

 oblique direction across the front of the thorax, 

 so as to bring the hand towards the mouth ; 

 the direction of the fore-arm is determined in 

 this movement by the obliquity of the trochlea 

 of the hnmerus from behind forwards and in- 

 wards, as described above, and influenced by 

 the clavicle preventing the falling inwards of 

 the shoulder ; were it not for the support of 

 the Clavicle, the hand in this movement, instead 

 ol being earned to the mouth, would be direct- 

 ed to the shoulder of the opposite side : when 

 flexion of the elbow is carried to its greatest 

 extent, the coronoid process and the head of 

 the radius are received into the anterior articu- 

 lar fossae of the humerus, displacing the adipose 

 masses from these cavities, the olecranon is 

 brought downwards on the trochlea so as to be 

 placed below the level of the condyles of the 

 hnnierus ; the posterior part of the synovial 

 capsule, the posterior ligament, and the triceps 

 and ancona'Us muscles are made tense, and 

 applied to the adipose mass in the posterior 

 articular fossa and to the posterior part of the 

 trochlea : the anterior part of the capsule and 

 the anterior ligament are relaxed, as are also the 

 lateral ligaments. A dislocation is rendered 

 impossible in this state of the articulation, 

 being effectually opposed by the hold which 

 the coronoid process has on the front of the 

 trochlea of the humerus. 



In partial flexion or semiflexion, the several 

 parts of the articulation are differently circum- 

 stanced ; the coronoid process being carried 

 down is no longer applied to the front of the 

 hiunerus, the olecranon is on a plane with the 

 condyles, and the lateral ligaments are on the 

 .stretch : in this stale of the parts a powerful 

 force applied to the olecranon from behind 

 might have the effect of displacing the ulna 

 forwards, were it not for the great mobility of 

 the limb, owing to which a force thus applied 

 is moderated or altogether expended in increa- 

 sing the degree of flexion ; hence a dislocation 

 of the ulna forwards on the humerus is an acci- 

 dent which never happens. 



In extension, the olecranon, ascending above 

 the level of the condyles, is received into the 

 posterior articular fossa, displacing the adipose 

 substance which previously occupied that fossa, 



the radius is brought back on the lew r head 

 of the hnmerus, over the anterior part of which 

 and of the trochlea the cnfsule and the anterior 

 ligament are stretched ; tl.e lateral li'janynts, 

 the tendon of the triceps, and the brachi.ens 

 anticus are also in a state of tension : the pos- 

 terior part of the capsule and the posterior 

 ligament arc necessarily relaxed. It is when 

 the elbow is in such a state of extension as 

 here described that a dislocation of the fore-arm 

 backwards usually occurs in consequence of a 

 fall on the hand ; the force producing the dis- 

 location in this case operates in the following 

 way, the fore-arm serving as a fixed point, the 

 humerus becomes a lever of the first order, the 

 fulcrum of which is the point of the olecranon 

 applied to the posterior side of its lower extre- 

 mity, the power is represented by the weight 

 of the trunk of the body applied to its superior 

 extremity in front, and acting with a force pro- 

 portioned to its remoteness from the point of 

 resistance formed by the ligaments and muscles 

 which are found in a state of tension in front ; 

 when this force is such as to overcome the re- 

 sistance, the ligaments in front are ruptured, 

 the lower extremity of the humerus is then 

 driven downwards in front of the bones of the 

 fore-arm, the upper extremities of which are 

 forced upwards behind the humerus, so that 

 the coronoid process comes to occupy the nor- 

 mal situation of the olecranon in the posterior 

 articular fossa. 



Lateral motion. Anatomists have been 

 divided in opinion as to the possibility of any 

 lateral motion being performed by the ulna on 

 the humerus. Albinus, Boyer, Beclard, Cru- 

 veilhier, and others, have denied the occurrence 

 of it; Monro and Bichat, however, have dis- 

 tinctly noticed it : they consider that this mo- 

 tion is possible only in the semifixed stale of 

 the elbow, when the lateral ligaments are most 

 relaxed : in complete flexion, as well as in ex- 

 tension, the tense state of these ligaments effec- 

 tually opposes any such movement. In my 

 opinion it is easy to satisfy one's self as to the 

 occurrence of this motion ; it consists of a slight 

 degree of rolling of the middle prominent part 

 of the greater sigmoid cavity in the fossa of the 

 trochlea, produced by those fibres of the lower 

 part of the triceps which extend from the con- 

 dyle on each side to the olecranon, and by the 

 action of the anconaus externally, 



(J. Hart.) 



ELBOW-JOINT, ABNORMAL CON- 

 DITION OF. Placed in the middle of the 

 long lever which the upper, extremity repre- 

 sents, the elbow-joint is of necessity exposed 

 to numerous accidents, the most remarkable of 

 which are fractures and luxations. These, re- 

 duced or unreduced, produce immediate and 

 remote effects, to which it is our busn, 

 this place to advert. Congenital malforma- 

 tions sometimes, though very rarely, are to be 

 met with affecting this articulation, and require 

 some brief consideration. 



The several structures too, which enter into 

 the composition of the elbow-joint, are each 

 and all occasionally affected by acute and 



F 2 



