220 SPECIAL ANA TOMY OF THE SKELETON 



iliac furrow lies slightly below the level of the crest. It terminates behind in the posterior supe- 

 rior spinous process, the position of which is indicated by a slight depression on a level with the 

 spinous process of the second sacral vertebra. Between the two posterior superior spinous 

 processes, but at a lower level, is to be felt the spinous process of the third sacral vertebra (see 

 page 68). Another part of the bony pelvis easily accessible to touch is the tuberosity of the 

 ischium, situated beneath the gluteal fold, and, when the hip is flexed, it is easily felt, as it is then 

 to a great extent uncovered by muscle. Finally, the spine of the os pubis can always be readily 

 felt, and constitutes an important surgical guide, especially in connection with the subject of 

 hernia. It is nearly in the same horizontal line with the upper edge of the great trochanter. In 

 thin subjects it is very apparent, but in the obese it is obscured by the pubic fat. It can, however, 

 be detected by everting the thigh and following up the tendon of origin of the Adductor longus 

 muscle. 



Applied Anatomy. There is arrest of development in the bones of the pelvis in cases of 

 extroversion of the bladder; the anterior part of the pelvic girdle being deficient, the bodies of the 

 pubic bones imperfectly developed, and the symphysis absent. The pubic bones are separated 

 to the extent of from two to four inches, the superior rami shortened and directed forward, and 

 the obturator foramen diminished in size, narrowed, and turned outward. The iliac bones are 

 straightened out more than normal. The sacrum is very peculiar. The lateral curve, instead of 

 being concave, is flattened out or even convex, with the iliosacral facets turned more outward 

 than normal, while the vertical curve is straightened. 1 



Fractures of the pelvis are divided into fractures of the false pelvis and of the true pelvis. Frac- 

 tures of the false pelvis vary in extent: a small portion of the iliac crest may be broken or one of 

 the spinous processes may be torn off, and this may be the result of muscular action; or the 

 bone may be extensively comminuted. This latter accident is the result of some crushing vio- 

 lence, and may be complicated with fracture of the true pelvis. These cases may be accompanied 

 by injury to the intestine as it lies in the hollow of the bone, or to the iliac vessels as they course 

 along the margin of the true pelvis. Fractures of the true pelvis generally occur through the 

 ascending ramus of the os pubis and the ramus of the ischium, as this is the weakest part of the 

 bony ring, and may be caused either by crushing violence applied in an antero-posterior direction, 

 when the fracture occurs from direct force, or by compression laterally, when the acetabula are 

 pressed together, and the bone gives way in the same place from indirect violence. Occasionally 

 the injury may be double, a break occurring on both sides of the body. In fracture of the true 

 pelvis the contained viscera are liable to be damaged; the small intestines, the urethra, the bladder, 

 the rectum, the vagina, and even the uterus, in the female, have all been lacerated by a dis- 

 placed fragment. Fractures of the acetabulum are occasionally met with ; either a portion of 

 the rim may be broken off, or a fracture may take place through the bottom of the cavity, and the 

 head of the femur may be driven inward and project into the pelvic cavity. Separation of the 

 Y-shaped cartilage at the bottom of the acetabulum may also occur in the young subject, 

 dispersing the bone into its three anatomical portions. 



The sacrum is seldom broken. The cause is direct violence i. e., blows, kicks, or falls on the 

 part. The lesion may be complicated with injury to the nerves of the sacral plexus, leading 

 to paralysis and loss of sensation in the lower extremity or to incontinence of feces from paralysis 

 of the Sphincter ani. 



Fracture of the coccyx is a very rare injury, but does occasionally take place. Some sup- 

 posed dislocations of this bone have been fractures and so have some of the cases diagnosticated 

 as coccygodynia. A fracture of the coccyx is due to direct force. 



The pelvic bones often undergo important deformity in rhachitis, the effect of which in the 

 adult woman may interfere seriously with childbearing. The deformity is due mainly to the 

 weight of the spine and trunk, which presses on the sacrovertebral angle and greatly increases 

 it, so that the antero-posterior diameter of the pelvis is diminished. But, in addition to this, 

 the weight of the viscera on the venter ilii causes the ilia to expand and the tuberosities of the 

 ischia to incurve. In osteomalacia also great deformity may occur. The weight of the trunk 

 causes an increase in the sacrovertebral angle and a lessening of the antero-posterior diameter 

 of the inlet, and at the same time the pressure of the acetabula on the heads of the thigh bones 

 causes these cavities, with the adjacent bone, to be pushed upward and backward, so that the 

 oblique diameters of the pelvis are also diminished, and the cavity of the pelvis assumes a tri- 

 radiate shape, with the symphysis pubis pushed forward. 



THE THIGH. 



The thigh is that portion of the lower extremity which is situated between the 

 pelvis and the knee. It consists in the skeleton of a single bone, the femur. 



1 Wood, Heath's Dictionary of Practical Surgery, i, 426. 



