PRACTICAL CONSIDERATIONS : THE PELVIS. 345 



The weight in standing is transmitted to the thigh bones, in sitting to the 

 tuberosities of the ischia ; in both cases the parts of the pelvis running to the pubes 

 act as "ties" to prevent the spreading of the arch. The circumference of the 

 acetabulum is of strong bone to resist pressure from the joint, and in the erect 

 position a strong part runs from the socket directly upward to the crest of the 

 ilium. The thinness of the bottom of the acetabulum in all ages and the meeting 

 there in childhood of the three bones make it a weak place. 



Surface Anatomy. — The anterior superior spine of the ilium is easily felt, 

 but care must be taken not to mistake for it a swelling of the crest an inch or more 

 behind it. To make sure of this spine as a point for measurements, the finger 

 should be carried over it from the crest and then back again till it is arrested by 

 the overhanging spine. The anterior inferior spine cannot be felt. The outer 

 lip of the crest of the ilium can easily be followed to the posterior superior spine, 

 which is marked by a dimple, and is on a level with the middle of the sacro-sciatic 

 joint. The tuberosity of the ischium is readily felt, but it is too thickly covered for 

 details to be recognized. A line drawn from the posterior superior spine to the outer 

 part of the tuberosity of the ischium will cross the inferior spine of the ilium and the 

 spine of the ischium. A line from the same point to the top of the greater trochanter 

 will pass very close to the highest point of the great sacro-sciatic notch. The sym- 

 physis of the pubes and most of the borders of the pubic arch can be felt. The 

 spine of the pubes can be recognized, but usually not without some difficulty. It 

 may be necessary to feel for it beneath the skin by invaginating the scrotum or 

 labium. In woman it is nearly 2.5 centimetres from the median line ; in man some- 

 what less. 



PRACTICAL CONSIDERATIONS. 



Failure of devehpvient in the separate bones of the pelvis produces certain 

 well-known deformities. In the sacrum, the arch of the upper sacral vertebra, 

 which is formed later than the others and varies notably in thickness, is frequently 

 incomplete, which results in the very common occurrence of spina bifida at this 

 region (page 105 1). 



When the pelvic girdle is incomplete anteriorly, there is an interval of several 

 inches between the pubic bones, and all the bones of the pelvis are changed some- 

 what in shape and direction. The defect may be associated with exstrophy of the 

 bladder, epispadias in the male, split clitoris in the female, double inguinal hernia, 

 ectopia of the testicles, and sometimes ventral hernia from separation of the recti 

 muscles. 



Deforynitics of the pelvis have even more interest to the obstetrician than to 

 the surgeon. The usual differences between the male and female pelves are some- 

 times absent, constituting an abnormality, though perhaps stopping short of actual 

 deformity. The so-called masculine pelvis, for example, is characterized by a 

 diminution in the breadth of the pubic arch and an increase in the pubic angle. 



The female pelvis, as compared with that of the male, is lighter, less compact, 

 more expanded, shorter in vertical depth, broader at the inlet, with a greater angle 

 in its pubic arch, a lesser curve in the sacrum, and a greater separation between the 

 ischial spines, and is thus more perfectly adapted to the purposes of parturition. 



The chief deformities due to faulty development may be at least enumerated 

 here on account of their importance in this relation. In the simple flat pelvis the 

 antero-posterior diameter is contracted by the advancement of the sacrum in a down- 

 ward and forward direction between the iliac bones. The equally contracted pelvis 

 resembles a miniature normal female pelvis with other peculiarities that approxi- 

 mate it to the infantile type. The funnel-shaped pelvis is contracted transversely 

 at the outlet in both the antero-posterior and transverse diameters, the cavity is 

 deeper, the sacrum is narrow and less curved. These peculiarities are found in 

 very early life, and hence this is also known as the fottai. pelvis. The obliquely con- 

 tracted pelvis is due to imperfect development of the ala on one side of the sacrum, 

 which is associated with many secondary deformities, among them a lack of curva- 

 ture of the innominate bone on the affected side. The transversely contracted pelvis 

 in which both sacral alae are undeveloped is rarest of all contracted pelves. The 



