Radial polydactyly is also called split thumb
or thumb duplication. Or, an extra
thumb if we really want to keep it simple.
Extra thumbs all share some similarities but each is really
unique.
How most patients with radial polydactyly are similar
- Both thumbs are smaller than the “normal” thumb should be.
- Many extra thumbs have decreased motion. Fortunately, decreased motion is not a terribly big deal for function as the thumb can be great for function even with limited flexibility. It is more important that the thumb be well aligned and stable.
- Most thumbs are usable even though there is an extra digit. However, the extra thumb is often in the way, might limit use of the better thumb, and obviously creates a social issue for the child (with possible mental health impacts).
How patients with radial polydactyly can be different
- Some extra thumbs are pretty straight and some are really crooked ( really “z” shaped). This fact is, to me, the most important difference and the one that affects surgical technique and surgical outcome most. It is also the reason that more than one surgery might be necessary.
- Some thumbs have really pretty normal underlying tendons and joints whereas other thumbs have abnormal tissues. This affects motion and may play a role in recurrence of deformity.
- Sometimes the thumb is positioned right where it should be- a position to maximize holding big objects and pinching against index finger. Sometimes the thumb is more in the plane of the fingers, thus making pinch more challenging.
- Some extra thumbs are small and only have a single bone whereas others have 3 or more bones, extra muscles, etc.
The following is a case of an extra thumb treated at a young
age with a result that has made the family really happy. The radial polydactyly surgery was
somewhat complicated with excision of the extra, outer thumb and reconstruction
of the inner thumb. That reconstruction
included stabilizing the main joint, cutting and angling the bone, and
realigning the tendon.
Some of our research has been on the topic of appearance after the reconstruction of radial polydactyly.
http://www.ncbi.nlm.nih.gov/pubmed/18929199 This paper reviews the appearance outcome from a number of patients that we treated with surgery and concludes that the type of radial polydactyly (i.e., based on the bony appearance before surgery), the angulation after surgery, and the nail itself affect satisfaction with surgery.
Currently, the patient uses the thumb well, has a stable thumb,
and has no pain. The size is good and
not noticeably smaller than the other thumb.
However, the thumb is not straight.
At this point, the family is not concerned with the
deformity. Yet, I believe it is
something that can be effectively corrected as the child gets a bit older.
The hand doubles in size from birth until 2 years of age and
then almost doubles again at an adult size.
As the thumb gets larger, a correction is easier to accomplish and can
be done more precisely. I believe that
this patient will benefit from an osteotomy (or cutting) of the bone to
straighten the thumb. I continue to
follow patients on a yearly basis and the family and I will continue to
discuss this decision. I have no intention of
“talking” the family into a surgery but will make them aware of the option and
what an osteotomy surgery would require.
Specifically, it would require an outpatient surgery, require less
than1.5 hours of surgery time in most cases, and require pinning of the bone(s)
for about 5 weeks. We may have to work
on the soft tissues again as well. The patient's thumb and hand would be casted during those first 5 weeks and possible splinted later.
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Radial polydactyly before surgery. Note that both thumbs are crooked. We reconstructed the inner thumb and removed the outer thumb. |
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X-ray of radial polydactyly |
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1 year after radial polydactyly surgery. |
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Another view 1- year after surgery to reconstruct radial polydactyly. Note that the thumb is crooked. |
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x-ray after radial polydactyly reconstruction |
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x-ray after radial polydactyly reconstruction |