LACERATIONS OF THE PERINEUM.
It usually results from blows of the external genital organs against hard, sharp objects. There are many in stances of the kind on record. Hildebrandt speaks of a rupture of the perineum following a fall on the leg of a stool, with such force, indeed, as to break the object; of a case of a little girl who in sliding down the balusters, ruptured her perineum against the newel post We had a patient in our ward who deeply lacerated the perineum and the recto vaginal wall, as the result of a fall against a vine-prop. It occasionally happens that the perineum is lacerated during operative procedures for the removal of a polyp or the remnants from a miscarriage. These in stances, however, are groat rarities when compared with laceration, the result of parturition.
The most frequent cause of laceration during labor is the sudden birth of the foetal head. The introitus vagina; is frequently so narrow in a young nullipara, that there is scarcely room enough for the insertion of a single finger. It is wonderful how such a narrow introitus will distend under the pressure of the foetal head. If the birth of the head occurs slowly and in normal relations, then the perineum may be uninjured. If, however, at a critical moment, there is downward pressure or hasty manoeuvre then laceration is likely to occur. Even where the foetal head is small the perineum may be ruptured by intense bearing-down or pres sure, while a larger head under judicious management may be delivered without injury.
We are not concerned here with the details of the methods for the prevention of laceration, but it is necessary to state the principles on which they are based.
When we consider what is necessary for the protection of the peri neum during labor, we see that it lies in recourse to timely measures. The child must pass over this narrow route in order to he born, and this may happen without injury when it occurs slow enough. The first and most important measure for securing proper relaxation we have already spoken of: slow birth of the greatest circumference of the head, and the second is delivery by the smallest diameters of the head, which of course varies with the position, and the third is the preservation of distensibility as far as this is in our power. Finally, and only very exceptionally, we
note the enlargement of the introitus by lateral incisions in order to fore stal laceration.
To secure the first aim the various means of prevention in use are of value. They consist in holding back the head at the critical time, and in pressing it forwards against the symphysis. Thus the elasticity of the perineum is retained, and it is enabled to relax. In case a broad liga mentum arcuatum present forward pushing of the head, it must be stretched or incised.
The so-called Ritgen's method, which consists in fixing the head of the child by a finger in the rectum, and which also extends it gently dur ing the intervals of the pains, succeeds in securing slow delivery of the head in many cas As for the second desideratum, the birth of the head by its favorable diameters, the following points are to be noted: In case of occipital posi tions the diameter of the head engages, which is included between a line extending from the lines nuclue and one or the other frontal protuber ance; or rather, since the head generally lies a trifle oblique, a line extend ing from one side of the Linea nuclue to the opposite frontal protuberance. It is often erroneously believed that in other positions, that is to say, in brow and face, the engagement is not so favorable. Such is not, how ever, the case. In brow presentations that diameter engages which ex tends from a point midway between the large fontanelle and the middle of the forehead, and the occipital protuberance. In deep engagement the diameter lies between the top of the forehead and the lines nuchfe, so that in this instance engagement does not take place by a greater cir cumference than in the former, and the risk to the perineum is not at all greater. In case of face presentations, the conditions are still more favor able than in case A vertex. The engaging circumference is not at all greater than in case of occipital and brow presentations. Indeed it is often noted that exit of the head in face presentations is rather easy and quick than slow and difficult. In case of the after-coming head, the same diameters engage at the vulva as in case of occipital presentations.