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Dystocia due to fetomaternal disproportion: treatment
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Dystocia due to fetomaternal disproportion: treatment
FETOMATERNAL DISPROPORTION IN CATTLE As has been discussed earlier in the book, fetomaternal disproportion is a major cause of dystocia in cattle, with a considerable variation in the degree; it can be marginal or severe, the latter being associated with a very immature heifer or pathological enlargement of the fetus. The latter occurs with fetal giantism which can occur in embryos derived from in vitro maturation (IVM) or fertilisation (IVF), or prolonged gestation, or fetal monsters such as conjoined twins; these are described in Chapter 4 and 17. Sometimes in cases of dystocia due to fetomaternal disproportion, it may not always be obvious to the obstetrician whether the fetus is too large or the pelvis too small. However, the clinical signs based on clinical history and examination are the same, namely that the dam has been straining unproductively for a time in excess of the normal duration of the second stage of parturition for that species, with the fetus in the normal disposition for birth. In addition, the approach to the case and the technique for the treatment of the dystocia and delivery of the fetus are the same. It may be overcome in one of the following ways: ●
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The normal expulsive forces may be supplemented by external traction on the fetus. This method is frequently employed successfully by stockpersons and shepherds. The diameter of the vulval opening may be increased by episiotomy. The fetus may be removed by a caesarean operation. The volume of the fetus may be reduced by fetotomy (originally referred to as embryotomy), i.e. dismemberment of its body within the uterus and vagina, and the fetus
removed in several parts. Nowadays fetotomy is applied only when the fetus is already dead. As a guide to deciding which of the foregoing methods to use in a case of fetomaternal disproportion the veterinarian should be influenced by the obstetrician’s ideal, which is to render the abnormal birth as near to the physiological as possible, ensuring both the welfare and survival of dam and fetus whilst preserving the dam’s subsequent fertility. In the case of a group of animals where dystocia is being caused by fetomaternal disproportion, consideration should be given to inducing early parturition in the remainder of the group (see Chapter 6).
Fetomaternal disproportion: anterior presentation This is probably the commonest type of bovine dystocia. Modest disproportion is often successfully treated by the stockperson. It occurs in all breeds, particularly in immature heifers and those where there is a tendency for muscular hypertrophy. Although it is much commoner in heifers, many cases occur in mature cows, particularly when there has been a long delay in rendering obstetric aid, with resultant fetal enlargement due to emphysematous decomposition. Unfortunately, this occurs all too frequently. Often, when the veterinarian arrives, the animal has been in secondstage labour for at least 2 hours and there is a measure of secondary uterine inertia. The allantochorion has ruptured and two forefeet are visible as well as, occasionally, the fetal nose. Difficulty seems to be associated with the birth of the fetal head. In heifers this can be due to a failure of the posterior vagina and vulva to dilate; in adult cows it is often associated with too great a bulk of fetal chest and shoulders at the entrance to the maternal pelvis. 279
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Once the head is expelled, the remainder of the calf can usually be delivered, except in the case of calves with muscular hypertrophy which have disproportionately large shoulders and particularly large hindquarters. In these cases, the head, and perhaps the chest, may emerge with relatively little effort, but the calf’s hips will not pass into the maternal pelvis. At the initial examination, it is often difficult to be sure of the degree of disproportion, and therefore to decide which of the treatment options should be tried. With increasing experience, and if the degree of disproportion is severe, the veterinary surgeon may be able to make this judgement with considerable accuracy; however, in many cases it can only be made following attempted traction. A useful guide is to apply traction using two persons, or with a calving jack, and if it is possible to bring the head and the elbows of the two forelimbs caudal to the brim of the pelvis, then it is likely that traction will be successful. If it cannot be achieved, then an alternative strategy must be considered since prolonged unsuccessful traction will result in a high calf mortality rate and possible trauma to the cow or heifer.
Delivery by traction The vast majority of cases of moderate fetomaternal disproportion are successfully treated by the application of manual traction to the presenting feet, but birth is greatly expedited by first applying a head snare so that an axial pull may be put on the fetus. For vaginal delivery, three snares are
required, although it is important to stress that only minimal traction should be applied to the head snare. The animal is suitably restrained. A loop is made in the head snare and this is carried into the vulva where part of the loop is placed in the calf’s mouth and the remainder pushed up over the forehead and behind the ears. A simpler alternative, which is easier to apply and less stressful to the calf, is to push the centre point of a rope snare over the forehead and behind the ears, leaving both ends of the snare outside the vulva. A good axial pull, which also tends to depress the calf’s poll ventrally, can be achieved by simultaneous traction on both ends of the snare. Each of the other snares is placed above the fore fetlock of the calf. At first, with the head rope held taut, traction is applied to one foot snare with a view to advancing one shoulder at a time through the pelvic entrance (Figure 14.1). Then the other leg is advanced. All three ropes are then pulled on. At all times traction should be synchronous with the expulsive efforts of the cow and, as far as practicable, the initial pulling should be upwards; once the head engages the vulva, however, the direction of traction should be obliquely downward. After each bout of straining, and with each small advance of the fetus, the veterinarian should ascertain by further examination that delivery is proceeding satisfactorily. Frequent applications of lubricant to the vagina and to the fetal occiput are indicated and the veterinarian should be satisfied with very gradual progress.
Fig. 14.1 Diagnosis: anterior presentation, dorsal position, extended posture; fetal oversize. Delivery by traction. Alternate traction is first applied to the forelimbs. Note Benesch’s head snare for axial traction.
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Episiotomy. If it is obvious that the vulva is relatively small (as is commonly the case in Friesian–Holstein heifers) and that further traction on the calf will cause rupture of the vulva and perineum (with subsequent infertility), episiotomy should be performed. Freiermuth (1948) suggested incising, in the shape of an arch and in a dorsolateral direction, the vulval labium in its upper third. Cutting directly upwards into the perineal raphe is contraindicated because, once started, further birth of the calf will cause a traumatic upward extension towards, and sometimes into, the anus and rectum creating a third-degree perineal laceration. It is preferable to cut both labiae in the manner advised by Freiermuth; the requisite depth of the vulval incisions can be decided only by trial on the basis of the minimum amount to allow delivery. By gentle traction on the fetal head so as to cause firm engagement of the occiput in the vulval orifice, it is easy to ascertain the necessary depth of the incisions. Local infiltration, rather than epidural anaesthesia, should be used so as not to interfere with the maternal expulsive efforts. Immediately after delivery the wounds should be sutured, the suture material being passed through all the tissues of the wound except the vulval mucosa. Birth of the head is facilitated and rupture of the perineum is less likely to occur if, while downward traction is maintained on the head snare, the obstetrician inserts both hands, ‘cups’ them over the occiput and presses vigorously downwards. When the fetal head is born, all three ropes may be pulled on as the cow strains and the direction of traction should progressively approach the vertical. Obstruction sometimes occurs as the fetal pelvis engages the pelvic inlet; this is sometimes referred to as ‘hip-lock’ and is due to the greater trochanters of the femurs and the overlying muscle impinging on the shafts of the ilia. At this stage, slight retropulsion and rotation of the calf through an angle of 45° or even 90° is very helpful; this is because the sacral-pubic dimension is greater than that between the two ilia (remember the pelvic opening is oval in shape). The direction of traction should now be vertically downwards until birth is completed. The calf is attended to so as to free its nostrils of amnion or mucus, and respiration is stimulated. The genital tract of the cow or heifer is explored, firstly in order to ascertain that another
calf is not present, and secondly to make sure that it has sustained no trauma. In the case of impacted ‘hip-lock’ by a dead fetus where it is found impossible to repel and rotate the calf, Graham (1979) has suggested a method of reducing the fetal diameter so that traction may succeed. He uses a long-handled (75 cm) blunt hook which is passed into the fetal abdomen through an incision made just behind the xiphisternum. The hook is advanced to engage the fetal pelvis and abrupt traction on it then fractures the pelvic girdle. One or two repetitions of this procedure to cause further fractures and to ensure pelvic collapse may be followed by easy traction delivery. Another method of treating hip-lock in a dead fetus is to make a transverse bisection of the calf in the thoracolumbar region and then to divide the hindquarters by means of a vertical cut, both cuts being made by means of the wire-saw fetotome. When this has been completed each ‘half’ of the hindquarters can then be removed with care, which sometimes can be difficult without the use of obstetrical hooks (see Figure 12.1). At all stages of traction it is important that the veterinarian should determine that the disposition of the calf continues to remain normal, as well as its progress through the birth canal by vaginal examination; the importance of ensuring that there is plenty of lubrication cannot be stressed enough. Where possible, traction should coincide with the abdominal contractions of the cow, and the veterinary surgeon should be satisfied with very gradual progress. It is not unusual for a cow to go down when heavy traction is applied; this is not necessarily a disadvantage, provided that she does not fall awkwardly and injure herself. In fact, with the patient in lateral recumbency, traction may be applied to better advantage, particularly if manual or by means of a pulley block. In the case of some calving jacks it can be an inconvenience. As you may have noted in Chapter 12 (Table 12.1), the tractive forces exerted by calving aids and pulley blocks are much greater than those associated with natural calvings and the use of people. Despite their obvious advantages there are some important disadvantages: ●
The amount of force which in unskilled hands can be applied. 281
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The fact that the pull is continuous and ungiving, which may lead to damage of maternal soft tissues. (In natural birth the calf would be advanced some way with each contraction, and then go back a little before the next contraction pushes it even further.) The fact that the direction of pull has to be at least slightly down towards the udder. If it is horizontal or away from the udder then the rump bar merely slips down the perineum away from the vulva when traction is applied. This means it is very difficult to apply force in the same direction as the expulsion forces of the cow. Ideally, force should be applied in a slightly upward direction until the calf’s head is within the pelvis, then in a horizontal direction until the calf’s head and chest have been delivered and, finally, in a progressively more downward direction until the calf’s hips have been born. This has been overcome in a more recent design of the calf puller, the Vink calving jack. This has a rump frame which fits around the tail head and vulva of the cow, allowing traction to be applied in the direction chosen by the obstetrician.
attempts have been made to develop predictive methods of the likely success of traction or whether a caesarean operation should be performed, the objective being to prevent the sequence: attempted traction/failure/caesarean operation/dead calf (Hindson, 1978). In any predictive method the two factors which have to be considered are the size of the calf and the size of the pelvis. Hindson (1978) found a good correlation between the digital diameter of the calf (as measured at the level of the fetlock) and its body weight. Since at the time of dystocia it is likely to be difficult, if not impossible, to measure the size of the pelvic inlet directly attempts have been made to correlate it with external pelvic measurements. Hindson (1978) found a good correlation between the medial interischial tuberosity distance and both the vertical and horizontal pelvic diameters. As a result of this, and a study involving 60 selected calvings, he devised a formula to obtain a figure for the traction ratio (TR). It is as follows:
If after 5 minutes of judicious traction no progress is made, the veterinary surgeon must resort to a caesarean operation if the calf is alive or dead, or fetotomy if the calf is dead. There are cases where it is difficult to assess whether a calf is alive or dead. If there is any question, the calf should be given the benefit of the doubt. If certain of success by the employment of limited fetotomy, such as the removal of a forelimb, or a forelimb together with the head and neck, this would be the method of choice; unfortunately, not infrequently, having embarked on fetotomy the obstetrician finds that total dismemberment will be necessary to effect delivery. Because of the difficulty in assessing the amount of fetotomy required and the knowledge that total fetotomy is a tedious and arduous task, there is an increasing tendency for veterinary surgeons to resort to a caesarean operation in cases of disproportion where the fetus cannot be delivered by reasonable traction. Assessment of the likely success of traction to relieve dystocia due to fetomaternal disproportion is very much based on trial and error. Several
P1 = the party factor of 0.95 for heifers; P2 = a correction factor of 1.05 for posterior presentation; E = a factor for breeds with muscular hypertrophy. Traction ratios greater than 2.5 are unlikely to have dystocia due to fetomaternal disproportion; between 2.3 and 2.5 traction is likely to be successful; between 2.1 and 2.3 substantial traction may be required which may not be successful; 2.1 or less the method of treatment should be by caesarean operation. In the author’s experience, it has some value as a predictive method, but since there are other variables such as the degree of uterine inertia or the dryness of the birth canal, for example, it needs to be used with caution. The technique of fetotomy for severe fetal oversize in extended anterior presentation will now be described. The method used involves the removal of one or sometimes two forelimbs, with a view to reducing the circumference of the fetal chest. If the head is likely seriously to impede the proposed manipulations it may be returned to the uterus; failing this, it may first be removed (Figure 14.2)
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TR =
Interischial distance P1 1 × × Calf’s digital diameter P2 E
DYSTOCIA DUE TO FETOMATERNAL DISPROPORTION: TREATMENT
Fig. 14.2 Diagnosis: as in Figure 14.1. Delivery by fetotomy. Amputation of the head using Thygesen’s wire-saw fetotome.
but it must be understood that the head is not itself the cause of dystocia due to fetomaternal disproportion.
Subcutaneous fetotomy: removal of a forelimb A foreleg may be removed by subcutaneous or percutaneous fetotomy. In either case, caudal epidural anaesthesia is employed. The simpler method, which will now be described, is subcutaneous removal, for which the essential instrument is a
fetotomy knife. When both forelegs are equally accessible it is immaterial which is removed, but the right-handed operator will find it easier to perform fetotomy on the left foreleg of the calf. This leg is snared – around the pastern rather than above the fetlock – and sustained traction applied to it by one assistant. The obstetrician makes a small incision with a scalpel into the skin in front of the fetlock joint. Into this ‘nick’ the beak of Roberts’ fetotomy knife is inserted, and a longitudinal incision is made up the front of the limb from the pastern to the scapular cartilage (Figure 14.3).
Fig. 14.3 Diagnosis: as in Figure 14.1. The head has been returned to the uterus. Delivery by fetotomy. Subcutaneous removal of the extended forelimb. Stage 1: the skin has been incised from the fetlock to the scapula, using Roberts’ fetotomy knife.
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Fig. 14.4 Diagnosis: as in Figure 14.1. Subcutaneous removal of the extended forelimb. Stage 2: finger dissection of the skin around the leg and extending as high as possible in the scapular region.
The knife is now laid aside, and the second step in the procedure is literally the ‘skinning’ of the limb in situ (Figure 14.4). This operation requires strong fingers, but with diligent application it may be completed in about 10 minutes. (The separation of the skin from the muscles lying over the scapula completes this second step.) The third step involves the division of the adductor muscles. This is conveniently done by reintroducing Roberts’ knife, and, by vigorous probing with the beak of the instrument, the muscle mass is separated into several ‘strings’; then each of these, in turn, is engaged and severed by the knife.
The fourth step (Figure 14.5) is to disarticulate the fetlock joint so that the digit is left connected to the detached skin of the metacarpus. A snare is then attached to the cannon bone, and, in order to get a more secure hold, an additional half-hitch is put on above the first loop. The shank of the snare, with traction bars, is then handed to two assistants, and the final step in the operation consists in avulsion of the denuded forelimb by the forcible traction while the operator applies counterforce to the front of the fetus. In this way, the remaining muscle attachments to the top of the scapula are broken and the limb comes away.
Fig. 14.5 Diagnosis: as in Figure 14.1. Subcutaneous removal of the extended forelimb. Stage 3: after the attachments of the pectoral muscles in the axilla have been broken down and the metacarpophalangeal joint disarticulated, traction is applied to the denuded limb. Note that the foot is still attached to the skin.
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In many cases the removal of the one forelimb gives a sufficient reduction in fetal diameter to allow delivery. The principles of traction previously described are applied and in this case the foot and skin of the amputated limb afford a safe hold for a snare. Should delivery not be possible after this operation, the other foreleg must be removed in the same way, after which moderate traction is usually successful. Occasionally, after removal of one or both forelimbs – and despite partial rotation of the fetus – its hindquarters become locked at the pelvic inlet. Now the calf should be withdrawn as far as possible, and the protruding part of the trunk completely severed. The fetal abdomen is eviscerated, following which one of the hindlegs must be removed. There are two ways of doing this, and the one chosen will depend largely on the mobility of the retained extremity. If it is possible, the posterior part of the calf should be repelled and one of the hindlimbs brought forward with the aid of a snare; the limb is then removed by subcutaneous fetotomy (presently to be described). If it is not possible to grasp the limb and bring it forward it must be amputated in the following way. Using a direct cutting fetotomy knife, such as Unsworth’s, an incision is made over the hip joint of the leg to be removed. The muscles lateral to the femoral head are also divided and the upper extremity of the femur is isolated. Around this a snare is passed and by vigorous abrupt traction the teres ligament is broken and the articular head freed from the acetabulum. The snare loop is then made secure below the great trochanter and sustained traction applied. This causes the leg to be drawn out from its skin; difficulty occurs over the os calcis but a few strokes of the knife frees this part also. The hind digit should be left attached to the skin and the leg disarticulated at the fetlock joint. After one of the hindlimbs is removed, the remainder of the posterior part of the fetus can be withdrawn by traction through the medium of the double hook – which is attached to the coapted skin of the severed trunk – and the digit and skin of the amputated limb. Amputation of both hindlimbs is rarely needed. In cases where hip-lock occurs after partial fetotomy of the front extremity, Graham’s (1979) method of causing fetal pelvic collapse should be
considered as an alternative to further dismemberment of the fetus. Complete fetotomy as described above is tiring and time-consuming, and requires substantial skill as well as the appropriate equipment. If the fetus is emphysematous and undergoing putrefaction the tissues readily break down even with modest force, thus making the task much easier.
Percutaneous fetotomy In the opinion of many obstetricians, the delivery of a dead calf associated with dystocia due to fetomaternal disproportion may be more expeditiously accomplished by percutaneous fetotomy, that is, by means of the wire-saw tubular fetotome. For ease of sterilisation the model preferred is the Swedish modification of Thygesen’s instrument. Reliable wire, safe handgrips, a wire introducer – such as Schriever’s – and a threader are required. Percutaneous fetotomy of a calf in anterior presentation will now be described. The first operation is the removal, in one piece, of the fetal head, neck and one forelimb (Figure 14.6). To do this the fetotome wire must be looped around the neck and forelimb and pushed back on one side so as to lie behind the posterior angle of the scapula where a deep incision is made with Unsworth’s knife to accommodate the wire. The head of the instrument is brought up to the base of the neck on the side opposite to the foreleg being removed.With the wire loop correctly placed, the section is very easily completed by an assistant who makes long sawing strokes, so as to use the maximum length of available wire. The detached segment of fetus is carefully drawn out of the birth canal. An attempt is now made to deliver the remainder of the calf by traction; a snare is placed on the intact limb and, with the aid of the double hook, another point of traction is available on the exposed lower, cervical vertebral column. If birth is not yet possible, the calf is repelled and the fetotome wire is looped around the trunk of the calf with the head of the instrument laterally, and as far back as possible, in the dorsolumbar region (Figure 14.7). Sawing is continued until the vertebral column is severed, when the anterior part of the calf may be delivered. The remainder of the abdomen is eviscerated, and the next step is to bisect, in the sagittal plane, the 285
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Fig. 14.6 Diagnosis: as in Figure 14.1. Delivery by percutaneous fetotomy. Amputation of the forelimb and neck after removal of the head (as in Figure 14.2). It is sometimes possible to remove the head, neck and forelimb in one operation.
Fig. 14.7 Diagnosis: as in Figure 14.1. Delivery by percutaneous fetotomy. Transverse division through the trunk after removal of the head and forelimb. Note that if the base of the neck had been removed with the forelimb, as in Figure 14.6, the operation would have been simplified.
hind extremity.To do this, the introducer, with wire attached, is passed over the dorsal aspect of the sacrum and down behind the perineum, where the hand, passed in under the calf, reaches it, pulls it out and completes the loop.The head of the instrument is placed against the fetal spine (Figure 14.8) and the hindquarters are divided by direct sawing; then each of the halves can be withdrawn in turn by means of the double hook. In comparing the facility with which a calf may be removed by subcutaneous or percutaneous fetotomy, it must be clearly appreciated that the 286
troublesome part of the percutaneous method is the correct placing and retention of the wire. Given strong wire, the actual sawing presents no difficulty. Occasionally, the two methods may be advantageously combined, e.g. the subcutaneous procedure for the forelimb(s) and the wire-saw fetotome for the head, trunk and hindlimbs. Many veterinary surgeons now prefer a caesarean operation to total fetotomy. One cannot generalise on which method is preferable, but the subsequent health and fertility of the cow should figure prominently in the reckoning.
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Delivery by traction
Fig. 14.8 Diagnosis: as in Figure 14.1. Delivery by percutaneous fetotomy. Final stage of total fetotomy: longitudinal division of the hindparts.
Fetomaternal disproportion: posterior presentation The capacity of the fetus to survive obstructive dystocia is diminished if it is in posterior presentation; such cases therefore require prompt attention. Because of the abruptly presenting buttocks and contrary direction of the fetal hair, a posteriorly presented fetus is more difficult to deliver than a comparable one presented anteriorly. The retroverted tail may also be an impediment. When confronted with such a dystocia, the obstetrician should first attempt to assess the degree of disparity between the fetus and birth canal. Where oversize is slight, delivery by traction should first be tried.
The hindfeet are usually visible at the vulva, and to them snares are applied above the fetlock joints. It should be ascertained that the fetal tail is not retroverted; in delayed cases fetal fluid supplements are essential. With one leg repelled as far as possible (Figure 14.9), the other is pulled on so as to bring its stifle over the pelvic brim. The repelled limb is similarly dealt with. In this way a smaller fetal diameter is presented at the pelvic inlet and, with this simple manoeuvre, traction may succeed. A simple way of assessing the likely success of traction can usually be predicted if both stifle joints can be brought into the pelvis following a moderate amount of traction. If during traction the fetal pelvis becomes ‘jammed’ in the birth canal, the calf should be repelled a little, rotated through 45° and again pulled on. This latter manipulation, which brings the greater diameter of the fetus into the largest pelvic dimension, is often successful; it may be accomplished by simply bending the protruding metatarsi and using them as levers in a rotary manner. There is a misunderstanding, particularly among some stockpersons, that calves in posterior presentation need to be pulled out very rapidly, otherwise they will die. One must remember that the calf’s life will not be compromised until its umbilical cord becomes trapped against the maternal pelvis. In practical terms, therefore, traction should be slow and controlled until such time as the calf’s tail-head and anus begin to emerge from
Fig. 14.9 Diagnosis: posterior presentation, dorsal position, extended posture; fetal oversize. Delivery by traction. Alternate traction on the hindlimbs.
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the cow’s vulva. Once this point is reached, delay should be avoided. If the hindquarters can be delivered the forequarters usually follow, but there are exceptions and they will be considered when discussing total fetotomy in posterior presentation. In cases of posterior presentation where substantial judicious traction has not succeeded, the fetus must be removed by caesarean operation if the calf is alive, or if dead by caesarean or fetotomy. In the case of an immovable, dead fetus there is a choice about which it is difficult to generalise, but if there is obviously gross oversize a laparotomy is preferable. In many instances of medium oversized and dead fetuses, however, it may be easier to remove one limb, for this relatively simple operation often makes birth possible, and this fetotomy will now be described. The presenting legs can be removed by subcutaneous or percutaneous methods, and the former will be described first.
Subcutaneous removal of the hindlimb Posterior epidural anaesthesia is induced and a ‘nick’ made just above the fetlock on the posterior aspect of the extended fetal leg. Into this is placed the ‘beak’ of Roberts’ knife, and with it an incision is made from the fetlock up the back of the limb to the anterior gluteal region. The skin is separated all around the leg, and the muscles above the hip joint, as well as the adductor muscles, are divided. The femoral head is detached from the acetabulum by introducing a traction bar underneath the Achilles tendon and by forcibly rotating the limb laterally. The skin is then cut sufficiently around the fetlock joint to give scope for disarticulation, and a rope snare is placed over the freed end of the metatarsus. Sustained traction on the snare by two assistants, with retropulsion of the calf by the obstetrician, usually causes avulsion of the denuded limb. Removal of the one leg followed by traction on its foot – connected to the torso by the skin of the leg – and on the other limb often results in extraction of the calf. If it does not, then the other hindlimb must be similarly removed.This will allow complete delivery or birth of the posterior half of the calf. Should the forequarters become obstructed at the pelvic inlet, then further fetotomy is required as follows. As much of the calf as possible is withdrawn from the vulva and amputated. Evisceration 288
is now carried out. The remainder is repelled and then, with Unsworth’s knife, an incision is made in the skin over the scapula cartilage, and the muscles which connect the scapula to the spine are divided. By blunt dissection, the upper end of the shoulder blade is isolated and to it Krey’s hooks are fastened and traction applied. In this way, the limb is drawn out of its skin as far as the fetlock joint, at which point it is disarticulated and removed. The digit, with skin attached, together with Krey’s hooks gripping the thoracic vertebral column, serve as traction points for extraction of the remainder of the calf. In rare cases, before the anterior half can be withdrawn, the other forelimb must be removed.
Percutaneous removal of the hindlimb Percutaneous fetotomy in posterior presentation is most conveniently performed with the tubular wire-saw Danish fetotome. The instrument is threaded, and the wire loop placed over one foot and passed up the limb so that laterally it lies anterior to the external angle of the ilium where a cut in the skin, previously made with Unsworth’s knife, helps to retain it. The head of the instrument is placed lateral to the anus, and the tail of the calf must be included in the loop; otherwise, during sawing, the wire will slip down the limb and the section will be made through the distal third instead of through the upper extremity of the femur. The severed limb is removed. Traction is then applied to the calf by means of the Krey– Schottler hook attached to the perineum or with the aid of Obermayer’s anal hook passed over the calf’s pubic brim. If delivery is still impossible, the other hindleg must be removed and the fetus withdrawn as far as possible. If the calf cannot now be removed completely then its trunk must be bisected by means of the wire loop, the division being made as far forward as possible. One, or if necessary both, forelimbs are afterwards amputated by passing the wire, with the aid of Schriever’s introducer, forwards between the neck and foreleg and then reaching for the introducer underneath the calf; the wire is withdrawn, the threading of the instrument completed and its ‘head’ passed up the severed end of the vertebral column where the section may be made by sawing. The severed limb may be brought out by attaching to it Krey’s hook.
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An attempt is again made to withdraw the anterior portion of the calf and in most cases this is now possible. In the exceptional case the other foreleg must be removed in like manner.
FETOMATERNAL DISPROPORTION IN OTHER ANIMALS Mare Disproportion as a cause of dystocia is uncommon in horses. Apart from being more urgent, the occasional case of relative oversize is treated on similar lines to the bovine case, with the exception that because of the late osseous union of the fetal skull, only limited traction should be applied to the fetal head. Although prolonged gestation is not uncommon, excessively large fetuses are rare in horses. When the fetus is alive, the caesarean operation is the first consideration and, with the increasing experience of recent years, it is now preferred to total fetotomy for a dead fetus.
Ewe Oversize is a common cause of dystocia in ewes carrying single lambs. Ewes of the smaller breeds
are often mated to larger rams, and although the fetal size is controlled to a large extent by the dam, bulky body features derived from the ram, such as large head and coarseness of shoulders and buttocks, often cause trouble. Most cases are successfully overcome by the shepherd applying traction to the forelegs. More severe cases may be brought to the veterinary surgery, where they may be conveniently treated as described for the cow. Where judicious traction – using fine snares, copious lubricants and a high standard of cleanliness – does not succeed, a caesarean operation or fetotomy may be employed. Where the fetus is dead, and this is frequently so in cases seen by the veterinary surgeon, fetotomy is often indicated. In this species the subcutaneous methods of limb removal are very easily carried out, but the percutaneous technique, using the wire-saw protected by Glattli’s spiral tubes, is quite practicable.
Sow Although fetal oversize may occur in the multiparous species when pregnant with an abnormally small litter, it cannot be treated by fetotomy; if traction by hand, snare or forceps fails, then hysterotomy is indicated.
REFERENCES Freiermuth, G. J. (1948) J. Amer.Vet. Med. Assn, 113, 231. Graham, J. A. (1979) J. Amer.Vet. Med. Assn, 174, 169. Hindson, J. C. (1978) Vet. Rec., 102, 327.
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Dystocia due to fetomaternal disproportion: treatment
FETOMATERNAL DISPROPORTION IN CATTLE As has been discussed earlier in the book, fetomaternal disproportion is a major cause of dystocia in cattle, with a considerable variation in the degree; it can be marginal or severe, the latter being associated with a very immature heifer or pathological enlargement of the fetus. The latter occurs with fetal giantism which can occur in embryos derived from in vitro maturation (IVM) or fertilisation (IVF), or prolonged gestation, or fetal monsters such as conjoined twins; these are described in Chapter 4 and 17. Sometimes in cases of dystocia due to fetomaternal disproportion, it may not always be obvious to the obstetrician whether the fetus is too large or the pelvis too small. However, the clinical signs based on clinical history and examination are the same, namely that the dam has been straining unproductively for a time in excess of the normal duration of the second stage of parturition for that species, with the fetus in the normal disposition for birth. In addition, the approach to the case and the technique for the treatment of the dystocia and delivery of the fetus are the same. It may be overcome in one of the following ways: ●
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The normal expulsive forces may be supplemented by external traction on the fetus. This method is frequently employed successfully by stockpersons and shepherds. The diameter of the vulval opening may be increased by episiotomy. The fetus may be removed by a caesarean operation. The volume of the fetus may be reduced by fetotomy (originally referred to as embryotomy), i.e. dismemberment of its body within the uterus and vagina, and the fetus
removed in several parts. Nowadays fetotomy is applied only when the fetus is already dead. As a guide to deciding which of the foregoing methods to use in a case of fetomaternal disproportion the veterinarian should be influenced by the obstetrician’s ideal, which is to render the abnormal birth as near to the physiological as possible, ensuring both the welfare and survival of dam and fetus whilst preserving the dam’s subsequent fertility. In the case of a group of animals where dystocia is being caused by fetomaternal disproportion, consideration should be given to inducing early parturition in the remainder of the group (see Chapter 6).
Fetomaternal disproportion: anterior presentation This is probably the commonest type of bovine dystocia. Modest disproportion is often successfully treated by the stockperson. It occurs in all breeds, particularly in immature heifers and those where there is a tendency for muscular hypertrophy. Although it is much commoner in heifers, many cases occur in mature cows, particularly when there has been a long delay in rendering obstetric aid, with resultant fetal enlargement due to emphysematous decomposition. Unfortunately, this occurs all too frequently. Often, when the veterinarian arrives, the animal has been in secondstage labour for at least 2 hours and there is a measure of secondary uterine inertia. The allantochorion has ruptured and two forefeet are visible as well as, occasionally, the fetal nose. Difficulty seems to be associated with the birth of the fetal head. In heifers this can be due to a failure of the posterior vagina and vulva to dilate; in adult cows it is often associated with too great a bulk of fetal chest and shoulders at the entrance to the maternal pelvis. 279
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Once the head is expelled, the remainder of the calf can usually be delivered, except in the case of calves with muscular hypertrophy which have disproportionately large shoulders and particularly large hindquarters. In these cases, the head, and perhaps the chest, may emerge with relatively little effort, but the calf’s hips will not pass into the maternal pelvis. At the initial examination, it is often difficult to be sure of the degree of disproportion, and therefore to decide which of the treatment options should be tried. With increasing experience, and if the degree of disproportion is severe, the veterinary surgeon may be able to make this judgement with considerable accuracy; however, in many cases it can only be made following attempted traction. A useful guide is to apply traction using two persons, or with a calving jack, and if it is possible to bring the head and the elbows of the two forelimbs caudal to the brim of the pelvis, then it is likely that traction will be successful. If it cannot be achieved, then an alternative strategy must be considered since prolonged unsuccessful traction will result in a high calf mortality rate and possible trauma to the cow or heifer.
Delivery by traction The vast majority of cases of moderate fetomaternal disproportion are successfully treated by the application of manual traction to the presenting feet, but birth is greatly expedited by first applying a head snare so that an axial pull may be put on the fetus. For vaginal delivery, three snares are
required, although it is important to stress that only minimal traction should be applied to the head snare. The animal is suitably restrained. A loop is made in the head snare and this is carried into the vulva where part of the loop is placed in the calf’s mouth and the remainder pushed up over the forehead and behind the ears. A simpler alternative, which is easier to apply and less stressful to the calf, is to push the centre point of a rope snare over the forehead and behind the ears, leaving both ends of the snare outside the vulva. A good axial pull, which also tends to depress the calf’s poll ventrally, can be achieved by simultaneous traction on both ends of the snare. Each of the other snares is placed above the fore fetlock of the calf. At first, with the head rope held taut, traction is applied to one foot snare with a view to advancing one shoulder at a time through the pelvic entrance (Figure 14.1). Then the other leg is advanced. All three ropes are then pulled on. At all times traction should be synchronous with the expulsive efforts of the cow and, as far as practicable, the initial pulling should be upwards; once the head engages the vulva, however, the direction of traction should be obliquely downward. After each bout of straining, and with each small advance of the fetus, the veterinarian should ascertain by further examination that delivery is proceeding satisfactorily. Frequent applications of lubricant to the vagina and to the fetal occiput are indicated and the veterinarian should be satisfied with very gradual progress.
Fig. 14.1 Diagnosis: anterior presentation, dorsal position, extended posture; fetal oversize. Delivery by traction. Alternate traction is first applied to the forelimbs. Note Benesch’s head snare for axial traction.
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Episiotomy. If it is obvious that the vulva is relatively small (as is commonly the case in Friesian–Holstein heifers) and that further traction on the calf will cause rupture of the vulva and perineum (with subsequent infertility), episiotomy should be performed. Freiermuth (1948) suggested incising, in the shape of an arch and in a dorsolateral direction, the vulval labium in its upper third. Cutting directly upwards into the perineal raphe is contraindicated because, once started, further birth of the calf will cause a traumatic upward extension towards, and sometimes into, the anus and rectum creating a third-degree perineal laceration. It is preferable to cut both labiae in the manner advised by Freiermuth; the requisite depth of the vulval incisions can be decided only by trial on the basis of the minimum amount to allow delivery. By gentle traction on the fetal head so as to cause firm engagement of the occiput in the vulval orifice, it is easy to ascertain the necessary depth of the incisions. Local infiltration, rather than epidural anaesthesia, should be used so as not to interfere with the maternal expulsive efforts. Immediately after delivery the wounds should be sutured, the suture material being passed through all the tissues of the wound except the vulval mucosa. Birth of the head is facilitated and rupture of the perineum is less likely to occur if, while downward traction is maintained on the head snare, the obstetrician inserts both hands, ‘cups’ them over the occiput and presses vigorously downwards. When the fetal head is born, all three ropes may be pulled on as the cow strains and the direction of traction should progressively approach the vertical. Obstruction sometimes occurs as the fetal pelvis engages the pelvic inlet; this is sometimes referred to as ‘hip-lock’ and is due to the greater trochanters of the femurs and the overlying muscle impinging on the shafts of the ilia. At this stage, slight retropulsion and rotation of the calf through an angle of 45° or even 90° is very helpful; this is because the sacral-pubic dimension is greater than that between the two ilia (remember the pelvic opening is oval in shape). The direction of traction should now be vertically downwards until birth is completed. The calf is attended to so as to free its nostrils of amnion or mucus, and respiration is stimulated. The genital tract of the cow or heifer is explored, firstly in order to ascertain that another
calf is not present, and secondly to make sure that it has sustained no trauma. In the case of impacted ‘hip-lock’ by a dead fetus where it is found impossible to repel and rotate the calf, Graham (1979) has suggested a method of reducing the fetal diameter so that traction may succeed. He uses a long-handled (75 cm) blunt hook which is passed into the fetal abdomen through an incision made just behind the xiphisternum. The hook is advanced to engage the fetal pelvis and abrupt traction on it then fractures the pelvic girdle. One or two repetitions of this procedure to cause further fractures and to ensure pelvic collapse may be followed by easy traction delivery. Another method of treating hip-lock in a dead fetus is to make a transverse bisection of the calf in the thoracolumbar region and then to divide the hindquarters by means of a vertical cut, both cuts being made by means of the wire-saw fetotome. When this has been completed each ‘half’ of the hindquarters can then be removed with care, which sometimes can be difficult without the use of obstetrical hooks (see Figure 12.1). At all stages of traction it is important that the veterinarian should determine that the disposition of the calf continues to remain normal, as well as its progress through the birth canal by vaginal examination; the importance of ensuring that there is plenty of lubrication cannot be stressed enough. Where possible, traction should coincide with the abdominal contractions of the cow, and the veterinary surgeon should be satisfied with very gradual progress. It is not unusual for a cow to go down when heavy traction is applied; this is not necessarily a disadvantage, provided that she does not fall awkwardly and injure herself. In fact, with the patient in lateral recumbency, traction may be applied to better advantage, particularly if manual or by means of a pulley block. In the case of some calving jacks it can be an inconvenience. As you may have noted in Chapter 12 (Table 12.1), the tractive forces exerted by calving aids and pulley blocks are much greater than those associated with natural calvings and the use of people. Despite their obvious advantages there are some important disadvantages: ●
The amount of force which in unskilled hands can be applied. 281
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The fact that the pull is continuous and ungiving, which may lead to damage of maternal soft tissues. (In natural birth the calf would be advanced some way with each contraction, and then go back a little before the next contraction pushes it even further.) The fact that the direction of pull has to be at least slightly down towards the udder. If it is horizontal or away from the udder then the rump bar merely slips down the perineum away from the vulva when traction is applied. This means it is very difficult to apply force in the same direction as the expulsion forces of the cow. Ideally, force should be applied in a slightly upward direction until the calf’s head is within the pelvis, then in a horizontal direction until the calf’s head and chest have been delivered and, finally, in a progressively more downward direction until the calf’s hips have been born. This has been overcome in a more recent design of the calf puller, the Vink calving jack. This has a rump frame which fits around the tail head and vulva of the cow, allowing traction to be applied in the direction chosen by the obstetrician.
attempts have been made to develop predictive methods of the likely success of traction or whether a caesarean operation should be performed, the objective being to prevent the sequence: attempted traction/failure/caesarean operation/dead calf (Hindson, 1978). In any predictive method the two factors which have to be considered are the size of the calf and the size of the pelvis. Hindson (1978) found a good correlation between the digital diameter of the calf (as measured at the level of the fetlock) and its body weight. Since at the time of dystocia it is likely to be difficult, if not impossible, to measure the size of the pelvic inlet directly attempts have been made to correlate it with external pelvic measurements. Hindson (1978) found a good correlation between the medial interischial tuberosity distance and both the vertical and horizontal pelvic diameters. As a result of this, and a study involving 60 selected calvings, he devised a formula to obtain a figure for the traction ratio (TR). It is as follows:
If after 5 minutes of judicious traction no progress is made, the veterinary surgeon must resort to a caesarean operation if the calf is alive or dead, or fetotomy if the calf is dead. There are cases where it is difficult to assess whether a calf is alive or dead. If there is any question, the calf should be given the benefit of the doubt. If certain of success by the employment of limited fetotomy, such as the removal of a forelimb, or a forelimb together with the head and neck, this would be the method of choice; unfortunately, not infrequently, having embarked on fetotomy the obstetrician finds that total dismemberment will be necessary to effect delivery. Because of the difficulty in assessing the amount of fetotomy required and the knowledge that total fetotomy is a tedious and arduous task, there is an increasing tendency for veterinary surgeons to resort to a caesarean operation in cases of disproportion where the fetus cannot be delivered by reasonable traction. Assessment of the likely success of traction to relieve dystocia due to fetomaternal disproportion is very much based on trial and error. Several
P1 = the party factor of 0.95 for heifers; P2 = a correction factor of 1.05 for posterior presentation; E = a factor for breeds with muscular hypertrophy. Traction ratios greater than 2.5 are unlikely to have dystocia due to fetomaternal disproportion; between 2.3 and 2.5 traction is likely to be successful; between 2.1 and 2.3 substantial traction may be required which may not be successful; 2.1 or less the method of treatment should be by caesarean operation. In the author’s experience, it has some value as a predictive method, but since there are other variables such as the degree of uterine inertia or the dryness of the birth canal, for example, it needs to be used with caution. The technique of fetotomy for severe fetal oversize in extended anterior presentation will now be described. The method used involves the removal of one or sometimes two forelimbs, with a view to reducing the circumference of the fetal chest. If the head is likely seriously to impede the proposed manipulations it may be returned to the uterus; failing this, it may first be removed (Figure 14.2)
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TR =
Interischial distance P1 1 × × Calf’s digital diameter P2 E
DYSTOCIA DUE TO FETOMATERNAL DISPROPORTION: TREATMENT
Fig. 14.2 Diagnosis: as in Figure 14.1. Delivery by fetotomy. Amputation of the head using Thygesen’s wire-saw fetotome.
but it must be understood that the head is not itself the cause of dystocia due to fetomaternal disproportion.
Subcutaneous fetotomy: removal of a forelimb A foreleg may be removed by subcutaneous or percutaneous fetotomy. In either case, caudal epidural anaesthesia is employed. The simpler method, which will now be described, is subcutaneous removal, for which the essential instrument is a
fetotomy knife. When both forelegs are equally accessible it is immaterial which is removed, but the right-handed operator will find it easier to perform fetotomy on the left foreleg of the calf. This leg is snared – around the pastern rather than above the fetlock – and sustained traction applied to it by one assistant. The obstetrician makes a small incision with a scalpel into the skin in front of the fetlock joint. Into this ‘nick’ the beak of Roberts’ fetotomy knife is inserted, and a longitudinal incision is made up the front of the limb from the pastern to the scapular cartilage (Figure 14.3).
Fig. 14.3 Diagnosis: as in Figure 14.1. The head has been returned to the uterus. Delivery by fetotomy. Subcutaneous removal of the extended forelimb. Stage 1: the skin has been incised from the fetlock to the scapula, using Roberts’ fetotomy knife.
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Fig. 14.4 Diagnosis: as in Figure 14.1. Subcutaneous removal of the extended forelimb. Stage 2: finger dissection of the skin around the leg and extending as high as possible in the scapular region.
The knife is now laid aside, and the second step in the procedure is literally the ‘skinning’ of the limb in situ (Figure 14.4). This operation requires strong fingers, but with diligent application it may be completed in about 10 minutes. (The separation of the skin from the muscles lying over the scapula completes this second step.) The third step involves the division of the adductor muscles. This is conveniently done by reintroducing Roberts’ knife, and, by vigorous probing with the beak of the instrument, the muscle mass is separated into several ‘strings’; then each of these, in turn, is engaged and severed by the knife.
The fourth step (Figure 14.5) is to disarticulate the fetlock joint so that the digit is left connected to the detached skin of the metacarpus. A snare is then attached to the cannon bone, and, in order to get a more secure hold, an additional half-hitch is put on above the first loop. The shank of the snare, with traction bars, is then handed to two assistants, and the final step in the operation consists in avulsion of the denuded forelimb by the forcible traction while the operator applies counterforce to the front of the fetus. In this way, the remaining muscle attachments to the top of the scapula are broken and the limb comes away.
Fig. 14.5 Diagnosis: as in Figure 14.1. Subcutaneous removal of the extended forelimb. Stage 3: after the attachments of the pectoral muscles in the axilla have been broken down and the metacarpophalangeal joint disarticulated, traction is applied to the denuded limb. Note that the foot is still attached to the skin.
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In many cases the removal of the one forelimb gives a sufficient reduction in fetal diameter to allow delivery. The principles of traction previously described are applied and in this case the foot and skin of the amputated limb afford a safe hold for a snare. Should delivery not be possible after this operation, the other foreleg must be removed in the same way, after which moderate traction is usually successful. Occasionally, after removal of one or both forelimbs – and despite partial rotation of the fetus – its hindquarters become locked at the pelvic inlet. Now the calf should be withdrawn as far as possible, and the protruding part of the trunk completely severed. The fetal abdomen is eviscerated, following which one of the hindlegs must be removed. There are two ways of doing this, and the one chosen will depend largely on the mobility of the retained extremity. If it is possible, the posterior part of the calf should be repelled and one of the hindlimbs brought forward with the aid of a snare; the limb is then removed by subcutaneous fetotomy (presently to be described). If it is not possible to grasp the limb and bring it forward it must be amputated in the following way. Using a direct cutting fetotomy knife, such as Unsworth’s, an incision is made over the hip joint of the leg to be removed. The muscles lateral to the femoral head are also divided and the upper extremity of the femur is isolated. Around this a snare is passed and by vigorous abrupt traction the teres ligament is broken and the articular head freed from the acetabulum. The snare loop is then made secure below the great trochanter and sustained traction applied. This causes the leg to be drawn out from its skin; difficulty occurs over the os calcis but a few strokes of the knife frees this part also. The hind digit should be left attached to the skin and the leg disarticulated at the fetlock joint. After one of the hindlimbs is removed, the remainder of the posterior part of the fetus can be withdrawn by traction through the medium of the double hook – which is attached to the coapted skin of the severed trunk – and the digit and skin of the amputated limb. Amputation of both hindlimbs is rarely needed. In cases where hip-lock occurs after partial fetotomy of the front extremity, Graham’s (1979) method of causing fetal pelvic collapse should be
considered as an alternative to further dismemberment of the fetus. Complete fetotomy as described above is tiring and time-consuming, and requires substantial skill as well as the appropriate equipment. If the fetus is emphysematous and undergoing putrefaction the tissues readily break down even with modest force, thus making the task much easier.
Percutaneous fetotomy In the opinion of many obstetricians, the delivery of a dead calf associated with dystocia due to fetomaternal disproportion may be more expeditiously accomplished by percutaneous fetotomy, that is, by means of the wire-saw tubular fetotome. For ease of sterilisation the model preferred is the Swedish modification of Thygesen’s instrument. Reliable wire, safe handgrips, a wire introducer – such as Schriever’s – and a threader are required. Percutaneous fetotomy of a calf in anterior presentation will now be described. The first operation is the removal, in one piece, of the fetal head, neck and one forelimb (Figure 14.6). To do this the fetotome wire must be looped around the neck and forelimb and pushed back on one side so as to lie behind the posterior angle of the scapula where a deep incision is made with Unsworth’s knife to accommodate the wire. The head of the instrument is brought up to the base of the neck on the side opposite to the foreleg being removed.With the wire loop correctly placed, the section is very easily completed by an assistant who makes long sawing strokes, so as to use the maximum length of available wire. The detached segment of fetus is carefully drawn out of the birth canal. An attempt is now made to deliver the remainder of the calf by traction; a snare is placed on the intact limb and, with the aid of the double hook, another point of traction is available on the exposed lower, cervical vertebral column. If birth is not yet possible, the calf is repelled and the fetotome wire is looped around the trunk of the calf with the head of the instrument laterally, and as far back as possible, in the dorsolumbar region (Figure 14.7). Sawing is continued until the vertebral column is severed, when the anterior part of the calf may be delivered. The remainder of the abdomen is eviscerated, and the next step is to bisect, in the sagittal plane, the 285
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Fig. 14.6 Diagnosis: as in Figure 14.1. Delivery by percutaneous fetotomy. Amputation of the forelimb and neck after removal of the head (as in Figure 14.2). It is sometimes possible to remove the head, neck and forelimb in one operation.
Fig. 14.7 Diagnosis: as in Figure 14.1. Delivery by percutaneous fetotomy. Transverse division through the trunk after removal of the head and forelimb. Note that if the base of the neck had been removed with the forelimb, as in Figure 14.6, the operation would have been simplified.
hind extremity.To do this, the introducer, with wire attached, is passed over the dorsal aspect of the sacrum and down behind the perineum, where the hand, passed in under the calf, reaches it, pulls it out and completes the loop.The head of the instrument is placed against the fetal spine (Figure 14.8) and the hindquarters are divided by direct sawing; then each of the halves can be withdrawn in turn by means of the double hook. In comparing the facility with which a calf may be removed by subcutaneous or percutaneous fetotomy, it must be clearly appreciated that the 286
troublesome part of the percutaneous method is the correct placing and retention of the wire. Given strong wire, the actual sawing presents no difficulty. Occasionally, the two methods may be advantageously combined, e.g. the subcutaneous procedure for the forelimb(s) and the wire-saw fetotome for the head, trunk and hindlimbs. Many veterinary surgeons now prefer a caesarean operation to total fetotomy. One cannot generalise on which method is preferable, but the subsequent health and fertility of the cow should figure prominently in the reckoning.
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Delivery by traction
Fig. 14.8 Diagnosis: as in Figure 14.1. Delivery by percutaneous fetotomy. Final stage of total fetotomy: longitudinal division of the hindparts.
Fetomaternal disproportion: posterior presentation The capacity of the fetus to survive obstructive dystocia is diminished if it is in posterior presentation; such cases therefore require prompt attention. Because of the abruptly presenting buttocks and contrary direction of the fetal hair, a posteriorly presented fetus is more difficult to deliver than a comparable one presented anteriorly. The retroverted tail may also be an impediment. When confronted with such a dystocia, the obstetrician should first attempt to assess the degree of disparity between the fetus and birth canal. Where oversize is slight, delivery by traction should first be tried.
The hindfeet are usually visible at the vulva, and to them snares are applied above the fetlock joints. It should be ascertained that the fetal tail is not retroverted; in delayed cases fetal fluid supplements are essential. With one leg repelled as far as possible (Figure 14.9), the other is pulled on so as to bring its stifle over the pelvic brim. The repelled limb is similarly dealt with. In this way a smaller fetal diameter is presented at the pelvic inlet and, with this simple manoeuvre, traction may succeed. A simple way of assessing the likely success of traction can usually be predicted if both stifle joints can be brought into the pelvis following a moderate amount of traction. If during traction the fetal pelvis becomes ‘jammed’ in the birth canal, the calf should be repelled a little, rotated through 45° and again pulled on. This latter manipulation, which brings the greater diameter of the fetus into the largest pelvic dimension, is often successful; it may be accomplished by simply bending the protruding metatarsi and using them as levers in a rotary manner. There is a misunderstanding, particularly among some stockpersons, that calves in posterior presentation need to be pulled out very rapidly, otherwise they will die. One must remember that the calf’s life will not be compromised until its umbilical cord becomes trapped against the maternal pelvis. In practical terms, therefore, traction should be slow and controlled until such time as the calf’s tail-head and anus begin to emerge from
Fig. 14.9 Diagnosis: posterior presentation, dorsal position, extended posture; fetal oversize. Delivery by traction. Alternate traction on the hindlimbs.
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the cow’s vulva. Once this point is reached, delay should be avoided. If the hindquarters can be delivered the forequarters usually follow, but there are exceptions and they will be considered when discussing total fetotomy in posterior presentation. In cases of posterior presentation where substantial judicious traction has not succeeded, the fetus must be removed by caesarean operation if the calf is alive, or if dead by caesarean or fetotomy. In the case of an immovable, dead fetus there is a choice about which it is difficult to generalise, but if there is obviously gross oversize a laparotomy is preferable. In many instances of medium oversized and dead fetuses, however, it may be easier to remove one limb, for this relatively simple operation often makes birth possible, and this fetotomy will now be described. The presenting legs can be removed by subcutaneous or percutaneous methods, and the former will be described first.
Subcutaneous removal of the hindlimb Posterior epidural anaesthesia is induced and a ‘nick’ made just above the fetlock on the posterior aspect of the extended fetal leg. Into this is placed the ‘beak’ of Roberts’ knife, and with it an incision is made from the fetlock up the back of the limb to the anterior gluteal region. The skin is separated all around the leg, and the muscles above the hip joint, as well as the adductor muscles, are divided. The femoral head is detached from the acetabulum by introducing a traction bar underneath the Achilles tendon and by forcibly rotating the limb laterally. The skin is then cut sufficiently around the fetlock joint to give scope for disarticulation, and a rope snare is placed over the freed end of the metatarsus. Sustained traction on the snare by two assistants, with retropulsion of the calf by the obstetrician, usually causes avulsion of the denuded limb. Removal of the one leg followed by traction on its foot – connected to the torso by the skin of the leg – and on the other limb often results in extraction of the calf. If it does not, then the other hindlimb must be similarly removed.This will allow complete delivery or birth of the posterior half of the calf. Should the forequarters become obstructed at the pelvic inlet, then further fetotomy is required as follows. As much of the calf as possible is withdrawn from the vulva and amputated. Evisceration 288
is now carried out. The remainder is repelled and then, with Unsworth’s knife, an incision is made in the skin over the scapula cartilage, and the muscles which connect the scapula to the spine are divided. By blunt dissection, the upper end of the shoulder blade is isolated and to it Krey’s hooks are fastened and traction applied. In this way, the limb is drawn out of its skin as far as the fetlock joint, at which point it is disarticulated and removed. The digit, with skin attached, together with Krey’s hooks gripping the thoracic vertebral column, serve as traction points for extraction of the remainder of the calf. In rare cases, before the anterior half can be withdrawn, the other forelimb must be removed.
Percutaneous removal of the hindlimb Percutaneous fetotomy in posterior presentation is most conveniently performed with the tubular wire-saw Danish fetotome. The instrument is threaded, and the wire loop placed over one foot and passed up the limb so that laterally it lies anterior to the external angle of the ilium where a cut in the skin, previously made with Unsworth’s knife, helps to retain it. The head of the instrument is placed lateral to the anus, and the tail of the calf must be included in the loop; otherwise, during sawing, the wire will slip down the limb and the section will be made through the distal third instead of through the upper extremity of the femur. The severed limb is removed. Traction is then applied to the calf by means of the Krey– Schottler hook attached to the perineum or with the aid of Obermayer’s anal hook passed over the calf’s pubic brim. If delivery is still impossible, the other hindleg must be removed and the fetus withdrawn as far as possible. If the calf cannot now be removed completely then its trunk must be bisected by means of the wire loop, the division being made as far forward as possible. One, or if necessary both, forelimbs are afterwards amputated by passing the wire, with the aid of Schriever’s introducer, forwards between the neck and foreleg and then reaching for the introducer underneath the calf; the wire is withdrawn, the threading of the instrument completed and its ‘head’ passed up the severed end of the vertebral column where the section may be made by sawing. The severed limb may be brought out by attaching to it Krey’s hook.
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An attempt is again made to withdraw the anterior portion of the calf and in most cases this is now possible. In the exceptional case the other foreleg must be removed in like manner.
FETOMATERNAL DISPROPORTION IN OTHER ANIMALS Mare Disproportion as a cause of dystocia is uncommon in horses. Apart from being more urgent, the occasional case of relative oversize is treated on similar lines to the bovine case, with the exception that because of the late osseous union of the fetal skull, only limited traction should be applied to the fetal head. Although prolonged gestation is not uncommon, excessively large fetuses are rare in horses. When the fetus is alive, the caesarean operation is the first consideration and, with the increasing experience of recent years, it is now preferred to total fetotomy for a dead fetus.
Ewe Oversize is a common cause of dystocia in ewes carrying single lambs. Ewes of the smaller breeds
are often mated to larger rams, and although the fetal size is controlled to a large extent by the dam, bulky body features derived from the ram, such as large head and coarseness of shoulders and buttocks, often cause trouble. Most cases are successfully overcome by the shepherd applying traction to the forelegs. More severe cases may be brought to the veterinary surgery, where they may be conveniently treated as described for the cow. Where judicious traction – using fine snares, copious lubricants and a high standard of cleanliness – does not succeed, a caesarean operation or fetotomy may be employed. Where the fetus is dead, and this is frequently so in cases seen by the veterinary surgeon, fetotomy is often indicated. In this species the subcutaneous methods of limb removal are very easily carried out, but the percutaneous technique, using the wire-saw protected by Glattli’s spiral tubes, is quite practicable.
Sow Although fetal oversize may occur in the multiparous species when pregnant with an abnormally small litter, it cannot be treated by fetotomy; if traction by hand, snare or forceps fails, then hysterotomy is indicated.
REFERENCES Freiermuth, G. J. (1948) J. Amer.Vet. Med. Assn, 113, 231. Graham, J. A. (1979) J. Amer.Vet. Med. Assn, 174, 169. Hindson, J. C. (1978) Vet. Rec., 102, 327.
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