Because of these other anomalies the names "Constriction Ring Syndrome", "Constriction Band Syndrome", and "Streeter Bands" are given to this defect/disease. This is sometimes attributed to vascular disruption shared between cleft palate and other forms of cleft defects occurring together with ABS; this co-occurrence suggests an "intrinsic" defect of the blood circulation.The second theory postulates the involvement of an intrauterine disruption during pregnancy followed by a cascade of events involving amniotic rupture. When spontaneous rupture of the amnion occurs early in the second trimester, the separation of amnion from chorion produces many small, thin strands that can become entangled within digits and toes. Later, as the fetus grows but the bands do not, the bands become constricting. This constriction reduces blood circulation, hence causes congenital abnormalities. In some cases a complete "natural" amputation of a digit(s) or limb may occur before birth or the digit(s) or limbs may be necrotic (dead) and require surgical amputation following birth. The names "Amniotic Band Syndrome" (ABS), "Amniotic Disruption Complex", and "Amniochorionic Mesoblastic Fibrous Strings" are based on this theory. The third theory postulates the involvement of intrauterine trauma. Intrauterine trauma could be something like amniocentesis, or something like a fetal surgery. An intrauterine trauma could result in hemorrhage leading to acrosyndactyly. One study also showed the presence of bands as confirmed by sonography after fetal surgery.Because of these different theories, there are many names for this syndrome. For a long time people believed the second theory about the amniotic rupture and strands.
Malformation associated with constriction ring syndromeThe percentage of associated anomalies varies from 40% to as high as 80%
Constriction ring deformities are as common on the lower extremity as on the upper, almost all of these involve the musculoskeletal system, with clubbed feet being the most common in up to 30% of reported cases. Large reported series reveal an incidence between 5% and 15% of craniofacial malformations with clefting of the lip or palate. Prevention
Amniotic band syndrome is considered an accidental event and it does not appear to be genetic or hereditary, so the likelihood of it occurring in another pregnancy is remote. The cause of amnion tearing is unknown and as such there are no known preventative measures. Treatment
Surgical correction is recommended when a constriction ring results in a limb contour deformity, with or without lymphedema. Surgical technique
At the beginning of the surgery a tourniquet will be applied to the limb. A tourniquet compresses and controls local arterial and venous circulation for about 2 hours. The constriction band must be dissected very carefully to avoid damaging the underlying neurovasculature. When the constriction band is excised, there will be a direct closure. This allows the fatty tissue to naturally reposition itself under the skin. "With complete circumferential constriction bands, it is recommended that a two-stage correction approach be used. At the first operation, one-half of the circumference is excised and the other one-half can be excised after three to six months.