PELVIS. 



209 



spongy texture, and deep-seated position. 

 When fractures of this bone do happen, they 

 are most commonly found at the lower part, 

 which is less protected by the above pecu- 

 liarities. They occur chiefly from direct and 

 great violence, which generally injures also 

 other parts of the pelvis extensively, seriously 

 affecting the nerves of the sacral plexus, so 

 as to produce paraplegia and retention of 

 urine, as well as extensive injury to the soft 

 parts, such as result in effusion of blood, 

 peritonitis, and sloughing of the integuments. 

 Fractures at the lower part are much more 

 easy to diagnose than those of the upper, 

 which are seldom discovered till after death. 

 In the former case, the lower fragment is 

 generally drawn forwards by the action of the 

 great glutei and coccygei muscles, so as to 

 press upon and interfere with the functions 

 of the rectum, through which it may be felt 

 by the finger. It will also produce great pain 

 on moving the legs, which may lead to its 

 discovery, when more serious injury is not 

 present. 



The coccyx when normally placed is rarely 

 fractured, on account of its great mobility 

 and small size. It always happens by di- 

 rect violence. When ankylosed, it is more 

 frequently broken, and instances of this have 

 been before mentioned, in relation to the 

 obstruction of the outlet in parturition which 

 it occasions. It is diagnosed by the mo- 

 bility and grating of the fragments, and by 

 the pain caused by the action of the great 

 glutei muscles. Dislocation of the coccyx is 

 said to have occurred backward in difficult 

 labours, and to have been followed by abscess, 

 but these cases have been most probably 

 fractures like those just mentioned. 



Fractures of the innominate done generally 

 occur on one side only, where the greatest 

 part of the force has fallen, but sometimes on 

 both. They are most frequently found in the 

 ilium which is most exposed, but often impli- 

 cate both the ischium and pubes. They may 

 be confined to one part of the bone ; in which 

 case they are found chiefly about the iliac 

 crest and wing. Boyer relates a case in which 

 the inferior anterior iliac spine was broken off 

 by the kick of a horse. Cases are not un- 

 frequently seen where the anterior superior 

 iliac spine and a portion of the crest are 

 broken off. Sometimes they are comminuted 

 in, and radiate from, the cotyloid cavity, such 

 fractures generally resulting from direct vio- 

 lence against the lateral pelvic arch, and act- 

 ing on the head of the femur so as to drive it 

 inwards through the pelvic wall. 



Fractures of the pelvis, like those of the 

 spinal column, are seldom present without dis- 

 location also of the sacro-iliac or pubic joints. 

 This results from the circular arrangement of 

 its bones, and from the laws of its mechanism, 

 explained in the first section of this article. 

 Thus, when force is applied so as to compress 

 the pelvic circle from before backward (as 

 commonly the cause of these fractures is such 

 compression by the wheels of a loaded cart or 

 other vehicle), then the cotylo-sacral arch 

 Sit pp. 



yields inwards at its haunches, the sacro-iliac 

 joints, the anterior ligaments of which are 

 torn, and the articular surfaces separated in 

 front. At the same time the pubic tie yields 

 either at the symphysi.s or in the superior 

 rami. 



The innominate bone may be entirely dis- 

 located upward or backward, generally on 

 one side only. A case is related by Cloquet, 

 in which this was the case on both sides, the 

 pubic symphysis, at the same time, separated 

 an inch, the pubis and ischio-pubic ramus were 

 broken, and the bladder ruptured. Another 

 case, where the left innominate bone was dis- 

 placed upwards, was treated successfully by 

 Chaussier. 



The ligaments and fibro-cartilage of the sym- 

 physis pubis are usually torn, the latter ge- 

 nerally carrying with it a portion of one of 

 the bones ; or the superior ramus is broken 

 at its weakest part, above the obturator fora- 

 men, or it separates from the other innominate 

 pieces. In most cases the ischio-pubic ramus 

 of the same side also yields at or near the 

 point of suture, which is its thinnest and 

 weakest part, and the obturator foramen is 

 again penetrated. This results from the ope- 

 ration of the force upon the unsupported 

 ischio-sacral arch and its tie, after the other 

 has yielded. A preparation exhibiting such a 

 fracture is found in the King's College Mu- 

 seum. In this case the superior pubic ramus 

 has separated in the acetabulum from the 

 other pieces of the innominatum in the line 

 of the Y-shaped suture, while the fracture 

 through the ischio-pubic ramus extends up- 

 wards, along the side, and into the centre of 

 the pubic symphysis (fig. 126.). 

 Fig. 126. 



Fracture of the pubis and acetabulum. 



This fracture, accompanied by that of the 

 superior pubic ramus, may also happen from 

 a fall from a great height upon the breech, on 

 one side or both, as the force happens to fall. 

 The great strength of the body of the ischium 

 renders a fracture there of less frequent oc- 

 currence than in the other pieces of the 

 innoimnatum. 



Fractures of the innominate bones seldom 

 occur without displacement, produced usually 

 not by subsequent muscular action, which is 

 kept in check by their balance of power, and 

 by the extensive ligamentous and fascial at- 



