When a child is developing in the womb, thin bands from the lining of the amniotic membrane can break off and float in the amniotic fluid. In some individuals, these bands can be quite extensive and can wrap around body parts such as fingers, toes, or the entire limb like a tourniquet. When this occurs at the right time during gestation, the result can be a failure of the involved portion of the limb to form or a deep groove where the band caused constriction. The portion of the digit or limb further away from the constriction ring is underdeveloped frequently. Sometimes the bands can squeeze digits together and making them coalesce, similar to a severe form of webbing (ie, syndactyly). This process can involve a small part of a single digit, the entire limb, or multiple limbs. This process is known as constriction ring syndrome or amniotic band syndrome.
Constriction ring syndrome is usually not hereditary or genetic in nature. It can happen to any child and occurs in approximately 1 in 1200 to 15,000 births. It is, however, occasionally associated with cleft lip and palate. Sometimes, it can be detected on prenatal ultrasound. There is currently no way of preventing constriction ring syndrome. CRS footTreatment usually involves separating coalesced digits and improving contour where a deep groove has formed. This is mostly an elective procedure that can be planned. However, in some instances, the ring may cause significant constriction and interfere with the blood supply of the remaining limb. In these cases, surgery to relieve the constriction will need to be done urgently, usually in the first few days of life. Otherwise, surgery may begin as early as 3 months of age.
If multiple digits or limbs are involved, surgery is sometimes staged. For example, fingers that are fused may be separated in a stepwise fashion to avoid damaging the blood supply to adjacent digits. Or, if there are multiple deep grooves over the limbs or fingers, then it may be decided that only the severe ones will be corrected initially. Multiple surgeries may be required over a lifetime, depending upon the severity of the condition and the number areas involved.