Separation of omphalopagus twins: Unique reconstruction using syngeneic cryopreserved tissue

Unique By Timothy

Separation Reconstruction

of Omphalopagus Twins: Using Syngeneic Cryopreserved

G. Canty, St-, Richard Mainwaring, Thomas Frank Lynch, and James San

Diego,

Vecchione, Mathewson

John

Lamberti,

Tissue David Collins,

California

Omphalopagus twin girls were admitted for evaluation of possible separation and repair at age 7 days. Prenatal sonographic diagnosis occurred late in the third trimester and was followed by cesarean section delivery shortly thereafter. Results of extensive evaluation overthe next 7 days including x-rays, computed tomography and ultrasound scan of the head and torso, and cardiac catheterization showed: the gastrointestinal tracts were separate and normal, the livers were joined but had separate biliary and vascular systems, and the hearts were separate with vastly different anatomy and function. One twin (twin A) had a normal heart with a small insignificant VSD. Twin B had a single ventricle, an incompetent A-V valve, stenotic pulmonic valve, ASD, PDA, and congenital heart block. Hemodynamic support of twin B was almost entirely from twin A. The vascular communications between the two consisted of a major connection between the internal mammary arteries and large arterial and venous connections traversing the joined livers. Because of continued deterioration of twin B, separation was undertaken at age 15 days. The separation included dividing the liver and

the multiple large vascular connections. Two teams then reconstructed each twin separately. Twin B began showing signs of cardiac decompensation shortly after separation in spite of placement of a pacemaker, pulmonary artery banding, and ligation of the PDA. Cardiac function rapidly deteriorated and she died. Tissue from her chest wall was cryopreserved and placed in the tissue bank. Twin A underwent closure of her abdomen, and received a temporary bovine pericardial patch over the chest defect. She subsequently underwent placement of a graft of twin B’s rib cage to bridge the bony chest defect and skin flap closure. She is presently taking a normal diet and thriving at home at age 18 months. The use of cryopreserved tissue from a syngeneic source provides a unique method of reconstruction in this situation. J Pediatr Surg 33:750-753. Copyright o 1998 by W.B. Saunders Company.

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tion of a set of omphalopagus twins with a unique method of reconstruction.

HE INCIDENCE of conjoined twinning is reported as 1 in 50,000 to 100,000 births. Because the majority of conjoined twins are stillborn, and another large number die shortly after birth, the incidence of live birth with survival is 1 in 200,000 or less.lw3Successful separation of twins with long-term survival of both infants is rare.4,5 The terminology for conjoined twins has recently been addressed by Spencer.6,1 She makes a strong case for differentiating omphalopgus from thoracopagus twinnings; although the external ventral union may be identical, thoracopagus is reserved for those infants that have some conjunction of the heart, and omphalopagus refers to those with separate hearts. This distinction has definite clinical prognostic significance as true thoracopagus twins are almost never separable, whereas omphalopagus twins commonly are. 6,7We report the successful separa-

From the Cllildrem Hospital and Health Center; San Diego, CA. Address reprint requests to Tkothy G. Canty, Si: MD, 3030 Childrens Way, Suite 401, San Diego, CA 92123. Copyright 0 1998 by WB. Saunders Company 0022-3468/98/3305-0024$03.00/O

750

INDEX served

WORDS: tissue.

Omphalopagus

twins,

syngeneic

cryopre-

CASE REPORT Omphalopagus twin girls were transported to the Childrens Hospital, San Diego, for evaluation for possible separation at 7 days of age. Prenatal sonographic diagnosis had been made late in the third trimester and was followed by cesarian section delivery shortly thereafter. Neither twin required resuscitation at birth, and both began oral feeding by day 3. It became apparent that one of the twins exhibited less spontaneous activity than the other and was slightly cyanotic. The physical union was a ventral fusion of the torsos from the sternal notch to the umbilicus. Both twins were intubated before transport to ensure stable airways. Results of extensive studies over the next 7 days, including plain and contrast x-rays. computed tomography (CT) and ultrasound scan of the torsos and heads, and cardiac catheterization, showed normal and completely separate gastrointestinal (GI) tracts, two livers with separate vascular and biliary systems, but joined across the ventral union, separate hearts with vastly different anatomy and function. One twin (twin A) had a normal heart with a small insignificant VSD. The heart of twin B had a single ventricle, an incompetent A-V valve, a stenotic pulmonic valve. an ASD, PDA, and congenital heart block. The heart rate of twin A was 125 beats per minute. and that of twin B 45 beats per minute. Twin B was mildly cyanotic and in heart failure. The hemodynamic support of twin B was almost entirely from twin A. Vascular communications between the two consisted of a large arterial

Journal

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Vol 33, No 5 (May),

1998: pp 750-753

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connection between the internal mammary arteries and large arterial and venous communication between the aortas and the inferior vena cavas traversing the joined livers (Fig 1). Blood flow through these connections was from twin A to twin B via the arteries, and venous return in the reverse direction. The heart of twin B contributed virtually nothing to the circulation. Because of continued deterioration of twin B, separation was undertaken at 15 days of age. The operation proceeded smoothly, carefully balancing the volume and circulation of each twin as the liver was divided, and the large vascular connections were ligated. Twin B began showing signs of cardiac decompensation shortly after separation in spite of rapid placement of a cardiac pacemaker, ligation of the PDA, and pulmonary artery banding. The abdomen and chest were closed with the aid of a bovine pericardial patch graft. Cardiac function continued to deteriorate in spite of vigorous supportive efforts on return to the neonatal intensive care unit, and she died. After consultation with the parents, tissue from her chest was immediately harvested, cryopreserved, and placed in the tissue bank. Twin Aunderwent primary closure of her abdomen without difficulty. A temporary bovine pericardial patch was used to cover the bony chest wall defect. Maximal ventilatory and circulatory support was required for the first 2 postoperative days including high frequency ventilation, and steroid and pressor support. Weaning then was rapid and feedings were begun on the fourth postoperative day. On postoperative day 7, she was returned to the operating room, the bovine patch removed, and the graft of twin B’s rib cage was placed to cover the chest defect. Extensive skin flaps were mobilized to complete the closure (Fig 2). Several minor debridings of the closure were required over the ensuing days with eventual complete healing. She was discharged from the hospital on the 15th postoperative day. Over the past 16 months she has remained well with normal growth and development. Recent examination revealed a less than l-cm inverted U-shaped gap in the lower most portion of the “neostemum.”

Fig 1. Diagram shows extent of ventral union involving bony junction of the chests to sternal notch. The liver bridge contains major vascular connections between the aortas and the inferior vena cavas. The connection between the internal mammary arteries is not shown.

Whether this represents partial resorption and/or contraction of the syngeneic cartilage graft is speculative. Primary closure of this small gap may be necessary in the future.

DISCUSSION

Ancient sculptures and drawings of conjoined twin “monsters” predate written language as early as 6000 BC8 The earliest written record occurs in the Chinese literature of the 3rd century. Over the ensuing millennia, surviving, nonseparated, conjoined twins attained the status of medical, social, and circuslike curiosities, often with colorful names and histories9J0 The first recorded case of separation was by Koenig in 1689, a set of minimally conjoined omphalopagus twins, both of whom survived.” Reports of separation of a variety of types of conjoined twins have since appeared in both the lay and medical literature. Confusion exists regarding the terminology and classification of conjoined twins, which has direct bearing on the reports of the incidence of different types. Spencer has devoted much of her professional career to studying most, if not all the world’s reports of conjoined twins encompassing over 1,200 recorded cases. Her theories of the embryogenesis and resultant classification are noteworthy. The controversy as to whether conjunction is an accident of fusion or fission is clarified in her writings. She suggests that conjoined twins begin as a set of separate identical twins that “bump” together in only 8 specific areas of the embryo where ectoderm is not complete, resulting in fusion at these and only these points. Further, the fusion occurs at like areas, eg, head to head, tail to tail, and not head to tail etc. Her studies further detail and explain the eight types of conjoined twins and the relative incidences: parapagus (26%), thoracopagus (25%), omphalopagus (17%), cephalopagus (1 l%), ischiopagus (9%), pygopagus (6%), craniopagus (5%), and rachipagus (2%). It is generally quite simple to label these by external examination of the area of union. The exception is with thoracopagus and omphalopagus forms of twins, which may exhibit identical external musculoskeletal union from sternal notch to umbilicus but have very different internal unions. The importance of differentiating between these two is their vastly different prognosis. Thoracopagus should be reserved for those with some degree of union of the hearts, usually very complex and almost always not separable.6,7 Omphalopagus twins do not exhibit cardiac union, but almost always liver union, and on occasion some fusion of portions of the GI tract, (eg, duodenum or Meckels diverticulum). These twins are usually separable and will survive if other anomalies are not life limiting.12-15 The timing of separation of conjoined twins has received attention in the recent literature. In situations in

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Fig 2. (A) Twin A at the completion of the separation and primary closure of the abdomen. Note large bony defect of chest wall. (6) Graft of rib cage of twin B placed to fill bony defect of twin A (arrow). (Cl Mobilization of skin flaps to cover bony graft on twin A. (DI Final appearance of closure of twin A.

which the physiological status of the infants in their conjoined status is stable, delay of separation while the infants grow and stabilize further is preferred. The use of tissue expanders to enlarge the subcutanous and skin reserve for eventual closure has also been reported and appears attractive.i5.16 In this case, the deterioration of one twin forced our hand. Had we not proceeded, the demise of one twin would most certainly have led to the quick demise of both, precluding even the emergent saving of the remaining viable twin. Essential to a smooth operative course is precise knowledge of the anatomy and physiology of the conjoined organ and vascular systems. This will direct the conduct and order of the operation. In this case, the cardiac catheterization data supplied us with a detailed roadmap of the anatomy and physiology of these twins and directed how the separation should occur. These studies strongly suggested that the cardiac anatomy of twin B was nonsurvivable, which became clear when twin B began to die. Reconstruction of the bony chest wall defects after separation is a difficult problem in this form of omphlaopagus twins. Even though the hearts are separate, a large gap remains where the sternum is absent. Closing this gap primarily results in cardiac decompensation caused by

pressure on the heart. A variety of techniques has been suggested to accomplish closure, including flaps of chest wall and artificial implants.17J8 The use of the chest wall of a nonsurviving twin to reconstruct the surviving twin has been described when it has been clear that only one would survive, and the primary procedure was designed accordingly.19 The use of tissue from the nonsurviving twin has also occurred when death occurs on the operating table.4 In our case, the twins were successfully separated and returned to the nursery. When twin B died, it was only then that the idea of harvesting her chest wall and preserving it for delayed reconstruction of twin A was entertained. This was a delicate decision for both the parents and the members of the surgical teams. By preserving the tissue, we could return to the operating room at a time when twin A had stabilized, and proceed with the graft under very controlled conditions. This unique approach allowed for early definitive closure of the bony defect with cartilage and appropriate soft tissue flap mobilization for coverage. The small defect in the lower most portion of the neosternum may need further reconstructive attention in the future. The use of cryopreserved syngeneic tissue for reconstruction under specific circumstances needs further evaluation for future applications.

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11. Messmer BJ. Homchen H, Kosters C: Surgical separation of conjoined (Siamese) xiphopagus twins. Surgery 89:622-625. 1981 12. Poenaru D. Uroz-Tristan J, Leclerc S: Minimally conjoined omphalopagi: A consistent spectrum of anomalies. J Pediatr Surg 29:1236-1235,1994 13. Boles ET, Vassy LE: Thoraco-omphalopagus conjoined twins: successful surgical separation. Surgery 86:485-492, 1979 14. deVries PA: Separation of the San Francisco twins. Birth defects original article series 3:75-79, 1967 15. Wirt SW, Algren CL, Wallace VR, et al: Separation of conjoined twins. Aorn J 62:527-545, 1995 16. Zubowicz VN, Ricketts R: Use of skin expansion in separation of conjoined twins. Ann Plastic Surg 20:272-276, 1988 17. Chiu CT, Hou SH, Lai HS, et al: Separation of thoracopagus conjoined twins. A case report. J Cardiovasc Surg 351459-462, 1994 18. Saing H, Mok CK, Tam P, et al: Problems in the surgery of conjoined twins. Surgical Rounds 10:81-96, 1987 19. Oberniedermayr A, Buhlmeyer K, Fendel H. et al: Report of operation on newborn thoracopagi, and of another inviable thoracopagus tin German), Z. Kinderchir 6:162-174, 1968