ABNORMAL CONDITIONS OF THE SHOULDER JOINT. 



583 



power enough to resist the influence of the 

 weight of the upper extremity ; and hence the 

 head of the humerus, unrestrained by the 

 naturally loose capsular ligament, descends 

 to the extent of half an inch or an inch from 

 theglenoid cavity. There can be but little 

 doubt, also, that in the second period of the 

 disease we are now considering, an effu- 

 sion takes place into the interior of the syno- 

 vial capsule of the joint : this may be altered 

 sj'novial fluid or Ijmph, or purulent mat- 

 ter to a small amount ; but whatever the 

 effusion be, it also will have the effect of par- 

 tially displacing, and causing an elongation of, 

 the upper extremit}'. 



It may be asked how it happens that the 

 head of the humerus, once partially displaced 

 downwards, does not become subjected to a 

 secondary displacement inwards, under the 

 influence of the contractions of the pectoral 

 and other muscles ? The answer may perhaps 

 be, that, in the second stage of this disease, 

 the long tendon of the biceps retains its form, 

 place, and functions ; so long as this tendon 

 remains in its state of integrity, arching over 

 the head of the bone, and then passing in a 

 perpendicular line down along the humerus, 

 the head of this bone cannot be partially ele- 

 vated above its normal situation, nor even 

 drawn inwards or backwards by either of the 

 great muscles which form the anterior or pos- 

 terior walls of the axilla; but when the long 

 tendon of the biceps is destroyed, as it very 

 generally is in the third stage of this disease, 

 then the head of the humerus may be moved 

 in whatever direction the inclination of the 

 new plane formed by the altered surface of 

 the glenoid cavity may give, or the muscles 

 may draw it in. 



In the third stage of chronic arthritis of the 

 .shoulder, the bones which compose the joint 

 are carious, and their surfaces are partially 

 and unequally removed ; the length of the ex- 

 tremity may be diminished. The long tendon 

 of the biceps is removed, and hence no longer 

 influences the position which the head of the 

 humerus is ultimately to take, whether the 

 bone in this third stage be partially displaced 

 upwards, forwards, or backwards. 

 I Some of the surrounding muscles are in 

 this period of the disease in a state of atrophy, 

 while others retain their form and functions. 

 The proper articular muscles, whose normal 

 function it is to keep the head of the humerus 

 close to the glenoid cavity, are, in the third 

 stage of disease, wasted ; and besides, as their 

 capsular attachment is usually in this advanced 

 stage of the disease destroyed, their influence 

 becomes annihilated. 



The pectoralis major may draw the head 

 of the bone towards the median line ante- 

 riorly ; the latissimus dorsi and triceps pos- 

 teriorly towards the dorsum of the scapula ; 

 and several muscles, such as the attenuated 

 deltoid, the coraco-brachialis, &e., may ele- 

 vate the head of the humerus, so as to bring 

 its upper surface into contact with the acro- 

 mion and coracoid process. 



We cannot pretend to say what it is which 



determines the line of direction the head of the 

 humerus in these partial displacements which 

 occur from disease may take, or explain why the 

 bone should in some cases take one direction, 

 and why occasionally another ; no more than 

 we can assign any cause for the various direc- 

 tions the head of the femur takes in the third 

 stage of scrofulous caries of the hip joint, a 

 disease we consider analogous to this we are 

 now considering. 



Anchylosis of the shoulder joint. Anchy- 

 losis of the shoulder joint may be observed to 

 be one of the terminations of an attack of 

 acute or chronic arthritis of this joint. It 

 may, we think, be remarked generally as the 

 result of true bony anchylosis of any of the 

 joints of an extremity, that shortening of the 

 limb shall have taken place. This observation 

 seems to be exemplified by what we commonly 

 observe in studying the characters of true 

 bony anchylosis of the shoulder joint. Most 

 of the specimens preserved in our collection 

 at the Richmond Hospital museum and else- 

 where, present examples of solid union of the 

 bones which compose the shoulder joint ; 

 partial displacement upwards of the head of 

 the humerus, and slight shortening of the ex- 

 tremity having previously taken place. There 

 is at present in the museum of the Richmond 

 Hospital a specimen of complete bony anchy- 

 losis of the shoulder joint, which was exhi- 

 bited by Dr. R. Smith to the Pathological 

 Society on the 13th March, 1841, along with 

 some other examples of anchylosis of this 

 joint. " The specimen," observes Dr. Smith, 

 "was taken from the body of an individual aged 

 90, who had been confined to bed for many 

 years before his death. The external appear- 

 ance of the shoulder joint resembled some- 

 what those of luxation of the head of the hu- 

 merus into the axilla, so far as the acromion 

 process having been prominent, and the joint 

 in the region of the deltoid completely flat- 

 tened ; the arm was rotated inwards ; the 

 glenoid cavity and head of the humerus 

 formed one continuous bone ; the greater 

 tubercle was anchylosed by bone to the acro- 

 mion process, while the coracoid process 

 was similarly joined to the lesser tubercle." 

 Consequently the humerus must have been 

 partially displaced upwards, and the arm 

 shortened. The supra-spinatus and infra-spi- 

 natus muscles, as well as the sulv-capuluris, 

 had undergone fatty degeneration from want 

 of use ; a change very commonly observed in 

 cases of true anchylosis of long standing, no 

 matter which of the joints has been the seat 

 of this termination of arthritis. In the ex- 

 ample just adduced the humerus was observed 

 to have ascended, and the greater and lesser 

 tuberosities had formed a solid union with 

 the coracoid and acromion process ; but in 

 some examples the anchylosis has been found 

 to have taken place directly between the sur- 

 face of the glenoid cavity and the head of the 

 humerus ; and a vertical section of the bony 

 structures running through the consolidated 

 joint exhibited the cells of the original head 

 of the humerus and the diplos of the scapula 



p p 4 



