Anatomic Classification of Spencer for Conjoined Twins

head and face

ventral rostral fusion with fused face

2

thorax

ventral rostral fusion

ventral rostral fusion with conjoined heart

upper abdomen

ventral rostral fusion to umbilicus

ventral rostral fusion

lower abdomen

2

2

pelvis and sacrum

2

2

symphysis pubis

2

2

arms

4

4

legs

4

4

head and face

2

2

thorax

ventral rostral fusion lower thorax

2

upper abdomen

ventral rostral fusion

2

lower abdomen

ventral rostral fusion

fusion with shared GU tract

pelvis and sacrum

2

ventral caudal fusion of pelvis with 2 sacra

symphysis pubis

2

2

arms

4

4

legs

4

4

head and face

cranial vault (not face, not foramen magnum), 2 faces

may involve occiput

thorax

2

dorsal fusion vertebral column

upper abdomen

2

dorsal fusion vertebral column

lower abdomen

2

dorsal fusion vertebral column

pelvis and sacrum

2

2

symphysis pubis

2

2

arms

4

4

legs

4

4

head and face

2

2

thorax

2

2

upper abdomen

2

ventral lateral fusion

lower abdomen

2

ventral lateral fusion

pelvis and sacrum

dorsal fusion sacro-coccygeal and perineum, with 1 anus and 2 rectums

ventral lateral fusion with 1-2 sacra

symphysis pubis

2

1

arms

4

2 - 4

legs

4

2 - 3

head and face

2

ventral lateral fusion with 2 faces

thorax

ventral lateral fusion

ventral lateral fusion

upper abdomen

ventral lateral fusion

ventral lateral fusion

lower abdomen

ventral lateral fusion

ventral lateral fusion

pelvis and sacrum

ventral lateral fusion with 1-2 sacra

ventral lateral fusion with 1-2 sacra

symphysis pubis

1

1

arms

2 - 4

2 - 4

legs

2 - 3

2 - 3