362 The Pelvis 



The sacrum is wedged between the haunch bones from above 

 downwards and before backwards, the better to break shock and 

 escape dislocation. Its lower end forms a slightly movable joint with 

 the base of the coccyx, a fibro-cartilage being interposed ; sometimes 

 these bones are welded together ; as the result of a fall on to the but- 

 tocks, or during parturition, fracture may occur and union fail to take 

 place. Subsequently, during defalcation, and in every other movement 

 of the coccyx, the last sacral nerve is subjected to painful contusions, 

 and removal of the coccyx may be demanded. This distressing disease 

 is called coccydynia. A subcutaneous section of the nerves irritated 

 or of the muscles moving the coccyx is far less likely to afford relief 

 than removal of the bone itself, which in these cases may be found 

 necrosed. That the bone is loose or dislocated may be readily made 

 out by taking the coccyx between the finger and thumb, the finger 

 being in the rectum. In women who have spent much time on horse- 

 back the coccyx is especially incurved and likely to be broken in labour. 



Fracture of the pelvis is often associated with injury to the pelvic 

 viscera ; information can often be obtained as to the nature of the 

 fracture by digital examination through the rectum or vagina. The 

 treatment consists of rest in bed, the thighs being flexed, so as to 

 slacken the rectus femoris and the muscles of Scarpa's triangle, and a 

 band being fixed around the pelvis, if expedient. 



Fracture often traverses the slender pubic and ischial rami, in 

 which case laceration of the urethra may occur. Blood in the urine 

 is a grave symptom in fracture of the pelvis ; a metal catheter should 

 be carefully introduced, but if that cannot be done the perineal urethra, 

 or the bladder itself, must be opened, lest extravasation of urine 

 take place. The patient must not attempt to micturate. 



From great violence the head of the femur may be driven through 

 the acetabulum, or the pelvis crushed out of shape. 



The festal pelvis is small, so as not to interfere with parturition, and 

 even after birth its development proceeds slowly up to puberty. 

 During infancy there is not room in it for the bladder, which, together 

 with the coils of small intestine and much of the rectum, are lodged in 

 the abdomen. Thus it is that the young child's abdomen bulges so 

 greatly ; and that in perineal lithotomy difficulty may be experienced 

 in introducing the finger into his bladder. 



Deformities of the pelvis may be due to rickets or mollities 

 ossium. In each case the bones are soft, and, in rickets, as the grow- 

 ing child walks, sits, and stands, the weight of the body thrusts the pro- 

 montory of the sacrum towards the pubes at the expense of the conjugate 

 diameter of the brim. If such a child have her weak and bending 

 spine caged in an iron ' support,' the weight transmitted through the 

 soft pelvis is much increased and the pelvis rendered all the narrower. 



In mollities ossium, which comes on after puberty, the haunch- 

 bones yield from the superimposed weight at their weakest part, that is 



