A textbook of obstetrics . ANOMALIES IN THE FORCES OF LABOR. 443 than, the same as, or even greater than, the distance betweentheir crests. A further result of these combined forces pullingthe innominate bones inward and forward behind and hold-ing them in place in front is to produce in them an abnormalcurvature, as in the case of the sacrum, or as in a bow bentbetween ones hand and the ground (Fig. 298). The point ofangulation or greatest curvature is found on the ilio-pectinealline, back of the median transverse line of the pelvic inlet,near the sacro-iliac joints. On account of the flexion
A textbook of obstetrics . ANOMALIES IN THE FORCES OF LABOR. 443 than, the same as, or even greater than, the distance betweentheir crests. A further result of these combined forces pullingthe innominate bones inward and forward behind and hold-ing them in place in front is to produce in them an abnormalcurvature, as in the case of the sacrum, or as in a bow bentbetween ones hand and the ground (Fig. 298). The point ofangulation or greatest curvature is found on the ilio-pectinealline, back of the median transverse line of the pelvic inlet,near the sacro-iliac joints. On account of the flexion of theinnominate bones the transverse diameter of the rachitic pel-vis is relatively increased, but, as the whole pelvis is com-monly below the normal in size, this diameter rarely exceeds,if, indeed, it equals, the normal transverse measurement. Afurther consequence of the exaggerated curvature of the innom-inate bones is to throw the acetabula forward, so that the. Fig. 298.—Schematic representation of the anterior position of the acetabula ina rachitic pelvis. The prcs-ure of the femora from before backward contributes tothe flattening of the pelvis (Schroeder). counterpressure of the lower extremities is exerted more antero-posteriorly than in the normal pelvis (Fig. 298). The pubicrami and the symphysis are diminished in height and show alessened slant outward. The cartilage at the junction of thesymphysis projects inward upon the pelvic canal, standing outabove the level of the bones to such a degree that it is some-times a source of injury to the head or to the maternal struct-ures. The force of resistance at the symphysis to the outwardmovement of the innominate bones sometimes bends the endsof the pubic bones inward upon the pelvic canal, giving to thepelvic inlet the shape of a figure 8. From the traction of theadductor and rotator muscles of the thigh upon the tuberositiesof the ischiatic bones (increased in rachitis by the positions
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Keywords: ., bookcentury1800, bookdecade1890, bookidtex, booksubjectobstetrics
