ABNORMAL CONDITIONS OF THE SHOULDER JOINT. 



577 



tachment of these muscles at right angles to 

 the lever, and at a considerable distance from 

 the fulcrum, enables them to act at a great 

 mechanical advantage, and their sudden con- 

 traction makes the upper end of the humerus 

 to become the moveable extremity of the 

 lever, and presses it against the capsule, which 

 giving way between the triceps and the sub- 

 scapularis muscles, allows the bone to escape 

 into the subscapular fossa. The long diameter 

 of the glenoid cavity being vertically placed 

 is favourable to the motion of abduction, and 

 in some degree lessens the liability to dislo- 

 cation, to which the joint is so prone in this 

 position, whilst on the other hand the com- 

 parative fixity of the scapula when the arm 

 is being ahJucted, explains in some degree the 

 frequency of dislocation of the humerus down-, 

 wards. 



5. Circumduction is compounded of the 

 preceding motions, the flatness of the humeral 

 tuberosities and the shallowness of the glenoid 

 cavity rendering it very extensive in subser- 

 vience to the variety of uses of the upper ex- 

 tremity. Circumduction is much more limited 

 in the hip-joint, as there, the anatomical 

 conditions which favour this motion in the 

 shoulder are wanting, freedom of motion 

 being sacrificed to security. 



6. Rotation is imperfectly developed in the 

 shoulder joint, but it exists in great perfection 

 in the hip, as a necessary consequence of the 

 great development of the neck of the femur. 



(Ben, Geo. MDowel.} 



SHOULDER JOINT, ABNORMAL CON- 

 DITIONS OF. The alterations from the normal 

 condition of the shoulder joint, which we have 

 observed, may be classed under the three fol- 

 lowing heads : First, those which are pro- 

 duced by disease ; secondly, those caused by 

 accidental injury; and, thirdly, those which are 

 the result of congenital malformation, 



SECTION* I. Disease.. The abnormal 

 appearances observed in the joints in gene- 

 ral, and in that of the shoulder in particular, 

 resulting from disease, owe their origin to 

 some local injury done to the joint, or to 

 some specific irritation, such as gout, rheu- 

 matism, syphilis, struma, &c. Whether the 

 disease first commences in the bone, the 

 cartilage, or synovial membrane*, it soon in- 

 volves all the structures of the articulation 

 in the same morbid action, and with the local 

 affection is usually associated some form of 

 inflammation, either acute or chronic. 



ACUTE ARTHRITIS OF THE SHOULDER. The 



sipnptoms of acute inflammation of the shoulder 

 joint will be found to be similar to those we 

 have elsewhere in this work described as 

 being present, when some of the other large 

 articulations have been affected by it.f The 

 patient will feel considerable pain in the 

 shoulder joint, to the front of which he will 

 point as the seat of his most acute suffering. 

 This pain is aggravated by the slightest touch, 



* See HIP JOINT, Vol. II. p. 790. 

 t See Vol. III. pp. 4955 ; HIP JOINT ; also Vol. 

 II. pp. 788792. 

 VOL. IV. 



or when any movement is communicated to 

 the joint. The patient himself carefully pre- 

 serves his arm immovably in one posture as 

 he lies in bed, with his elbow abducted from 

 his side, and his hand supported in the state 

 of supination. Effusion of altered synovia, or 

 purulent matter, rapidly takes place into the 

 synovial sac of the articulation. There is much 

 heat of the surface and tension of the skin. 

 The pain which, as already mentioned, is felt 

 on the front of the shoulder joint, soon ex- 

 tends down the arm to the inside of the 

 elbow-joint, and the patient complains of 

 spasmodic starlings of the limb, and oedema of 

 the whole extremity may supervene. The 

 distention of the synovial sac of the articu- 

 lation increases, and the surgeon can discover 

 a fluctuation along the anterior or posterior 

 border of the deltoid region, and he may find 

 it expedient, with the view of relieving pain 

 and tension, to make an incision into the 

 joint, and thus give exit to a large quantity of 

 purulent matter. Irritative, or it may be in 

 some constitutions inflammatory, fever accom- 

 panies these symptoms, and the patient may 

 be carried off even before the period when 

 the purulent matter shall have made its way 

 to the surface ; or the acute inflammation may 

 subside into chronic arthritis, and articular 

 caries of the shoulder joint be established, to 

 run its subsequent course as a chronic 

 disease. 



The acute form of the disease only differs 

 from the chronic in the former being more 

 intense in its attack, and in being accompanied 

 with swelling of the joint in being more 

 rapid in its course, and more speedily pro- 

 ducing complete disouganisation of the arti- 

 cular textures. 



Anatomical characters of arthritis of the shoul- 

 der. Very few opportunities are offered to the 

 anatomist of witnessing the appearances which 

 the several tissues of the shoulder joint pre- 

 sent when they have been the seat of acute 

 inflammation ; we may, however, safely infer, 

 that the articular structure of this joint will 

 be altered in a similar manner in consequence 

 of an attack of acute arthritis, as the corre- 

 sponding tissues in other joints have been 

 already described.* 



CHRONIC ARTHRITIS OF THE SHOULDER. > 

 We meet, in practice, with two forms of chronic 

 arthritis of the shoulder. The first of these oc- 

 curs as an example of slow inflammation passing 

 into either articular caries or anchylosis of the 

 joint, and is analogous to the well-known 

 scrofulous disease of the hip. The second 

 furnishes us with a specimen of a chronic 

 disease, which the writer has elsewhere in 

 this work denominated chronic rheumatic 

 arthritis f ; a disease, the effects of which are 

 to be traced in all the articulations, but its 

 peculiarities are in no joint better exemplified 

 than when the shoulder becomes the seat of 

 it. We shall first treat of the abnornal ap- 

 pearances produced by the disease we call 



Vide Vol. III. p. 54. 



See HAND ; HIP JOINT ; ELBOW, &c. &c. 

 P P 



