A Dictionary for Birth Anomalies of the Upper Extremity

As much as I try to write for the non- physician, there are still medical terms throughout my blog posts. So, in an effort to simplify the terms and explain some basic concepts in the field of congenital hand, I will provide a dictionary of sorts.  I hope this helps simplify the terms and ideas.

Polydactyly means extra digit.  Polydactyly can be preaxial or radial sided (thumb sided) or postaxial (or ulnar sided, pinky sided) polydactyly.  The most common type is postaxial polydactyly.  There are a few rare types including central polydactyly (middle of hand) and mirror hand (3 or 4 extra digits on the thumb side).

Syndactyly means joined digits.  Most commonly there is only skin connecting the 2 fingers. However, sometimes bone can connect the fingers.  Rarely, more than 2 digits are involved in syndactyly.  The long and ring fingers are most commonly joined.

Longitudinal Deficiency means limited development on one side of the arm or forearm.  The most common type of longitudinal deficiency is radial sided (thumb sided) which may affect the radius bone, the muscles of the forearm and the thumb.  Less common is ulnar longitudinal deficiency which affects the pinky side of the forearm and may affect finger development as well.

Radial and ulnar longitudinal deficiency can affect the hand alone or the hand and forearm.  Cleft hand has been also called central deficiency as it typically affects the middle digits of the hand (as well as the thumb web space).  Cleft hand does not affect the forearm.

Amniotic constriction band has been called more than 30 different terms in the medical literature. Other common terms for this condition (which causes bands, syndactyly, and amputations) in amniotic band syndrome or constriction band syndrome. (although it is not a syndrome)  This category is by far the most common diagnosis given by pediatricians but is often inaccurate.

Symbrachydactyly is a tough term because it literally means short, webbed fingers but it is a term used for a broader range of conditions.  This includes children with absent fingers with nubbins and some kids with an absent hand or forearm.  This diagnosis can be difficult to distinguish from transverse deficiency or congenital amputation.

While I have previously written about causes for less than five fingers, it may be worth repeating. There are five common causes for less than five fingers: radial deficiency, ulnar deficiency, cleft hand, amniotic constriction band, and symbrachydactyly.

Camptodactyly means bent finger, specifically a finger in which the first joint (the PIP joint) does not straighten fully.  It can be present at birth, it can be associated with arthrogryposis, or it can present in the early teenage years.  Clinodactyly is most commonly seen in the small finger with deviation of the finger towards the ring finger.  The other fingers and the thumb can also be affected.

Charles A. Goldfarb, MD
My Bio at Washington University
congenitalhand@wudosis.wustl.edu

Extra Digits- What Happens After Treatment

Postaxial polydactyly is the medical term for an extra digit on the pinky side of the hand.  It is far and away the most common location for an extra digit.  It is much more commonly seen in African Americans compared to whites (the reverse is true with radial polydactyly- thumb side).  There is a definite inheritance pattern (typically autosomal dominant).  I have previously written about this on several occasions- read here. 

I find it interesting that most children with an extra finger next to the pinky are not treated by a hand surgeon.  The extra digits are routinely "tied- off" in the newborn nursery.  Rarely these children may be treated in the pediatrician's office or at an orthopedic surgeon's office.  And most of these kids do really well, although small signs of the extra digit remain years later.  However, this treatment is best for the small extra digit and not the fully formed digit which requires a more formal surgery.

There is a huge variety in how the extra finger may appear- from quite small to normally sized.  The position and development of the extra digit is also variable as noted in this excellent article in the medical literature.

This child has a fully formed extra digit next to his pinky.

Smaller (and a bit swollen) extra finger.

Another type of extra digit, this time coming off the small finger closer to the nail.

So, no matter whether the extra digits is "tied- off" in the newborn nursery, clipped in the clinic or treated with formal surgery, most patients do great. 

 

Subtle hint of where the extra digit was removed.

However problems do develop.

1) One potential problem with an extra digit procedure is the need for a later surgery, a formal surgery to address the scar or pain.  In a recent article on using clips in the clinic (see here), 7% of kids needed a scar revision surgery.  Here is an example of a child treated in the nursery with an uncomfortable residual "nubbin."

Painful, small nubbin after treatment of polydactyly.

2) When the extra finger is clipped or tied, the blood supply to the digit is cut off and the extra digit enlarges, turns black and eventually falls off.  However, the timing of this process is unclear and the extra digit can stay on for week.  There is also a risk of infection.  These factors affect family satisfaction with this type of procedure and it certainly makes education of the family very important.

Necrotic extra digit after being tied off.

Another necrotic small finger polydactyly after being tied off.

3) Even formal surgery is not perfect for polydactyly.  The goal with formal surgery is to remove the finger and address the nerves, arteries, and tendons to allow a satisfactory appearance and function. And it is usually successful.  There are few problems reported.  Here is one recent example of a patient I treated with a revision excision.  His first surgery had been elsewhere and the surgeon had left behind some bone and the nerve stump had become painful as well.

After incomplete extra finger excision.  The patient needed a revision surgery.

Charles A. Goldfarb, MD
My Bio at Washington University
congenitalhand@wudosis.wustl.edu

Short Fingers- Treatment Choices

Symbrachydactyly means short and webbed fingers but the term really includes a wide range of presentations.  I have previously posted on symbrachydactyly a number of times and this Post summarizes the 7 different types of hand appearance.  I have also written that I prefer certain techniques to lengthen the fingers such as bone lengthening or web space deepening- read Here and Here .  However, I do believe that using toes to lengthen fingers might make sense in certain very specific situations.  Consider this child:

Symbrachydactyly with excellent thumb.

Symbrachydactyly with excellent thumb.

Radiographs of same child with symbrachydactyly showing the great thumb and limited other digits.

This patient has symbrachydactyly although it shares some similarities to hypodactyly, as defined by Ezaki, et al article.  This patient has a great thumb but limited finger development.  The hand and metacarpal bones are well developed but there simply is very little development of the fingers (phalanges).  And, importantly for this discussion, there are excellent soft tissue pouches that can be used for reconstruction.

In order to provide a strong pinch, we elected to reconstruct the index finger which was the most developed finger.  It had a small remnant of the proximal phalanx and a small fingernail (with some of the distal phalanx beneath it.  To me, this seems like the ideal candidate for a nonvascularized toe to hand transfer.  While there can be problems with the feet, typically patients do well.  And the index finger has immediate length and stability and, we all hope, will grow (as long as the growth plates of the transferred bone remain open).

Symbrachydactyly after free toe phalanx transfer.

Palmar view after surgery for free toe transfer in symbrachydactyly.

Charles A. Goldfarb, MD
My Bio at Washington University
congenitalhand@wudosis.wustl.edu