Radial deficiency and ulnar deficiency are, for most children, easily distinguished. Radial deficiency, a condition about which I have blogged about on numerous occasions- see here – presents with a problem on the radial (thumb) side of the forearm and hand (mainly the thumb). The radius bone can be absent or limited and the extensor muscles are affected also.
Ulnar deficiency–
check posts here – can be a bit more challenging as there is more variability in presentation. In other words, it can be harder to group kids with
ulnar deficiency. The forearm is often affected and the ulna can be absent or deficient. Sometimes, the radius will be joined, or fused, to the humerus in these kids. The hand is also more variable as there can be absent fingers on the ulnar side (i.e., ring and small finger) or absent thumb.
Below is a case which presents like an ulnar deficiency but this child is different than most. The child is “typical” in the following ways. First, there is a clear ulnar deviation posture of the wrist. Second, the thumb is deficient and of limited function as can be seen with ulnar deficiency. However, neither the forearm nor the thumb are typical for ulnar deficiency. The forearm has a fusion of the radius and ulna. The thumb is marked limited, narrow, and of limited function. Certainly, we do think of other, really rare conditions with forearm synostosis (like Holt- Oram Syndrome or Nievergelt- Pearlman Syndrome)- but this child does exactly fit into any category.
Before presenting the case, I should clarify why it matters- that is, why it matters to make the best diagnosis. Making the right diagnosis provides a great deal of information to the family about what to expect now and in the future. It lets us know about associated problems or conditions that might not be obvious- these conditions can involve important organ systems like the heart or kidney. The right diagnosis can let us know about future siblings if the family is considering more kids and also the risks or expectations when the child is considering having his/ her own kids in the future. Genetic information is becoming more and more available and the cost of obtaining genetic information is decreasing- this will help so much in our understanding of these conditions. This particular child is also consulting a genetics team for additional thoughts. For now, I would classify this as an ulnar deficiency but we will continue to work with the genetics team moving forward.
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| Ulnar deviated wrist. Note the small thumb which is similar to a finger. The thumb is also not particularly functional and may benefit from intervention in the future. |
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| Another view of ulnar deficiency wrist. |
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| Ulnar deficiency before surgery. Unusual with radioulnar synostosis. |
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| Ulnar deficiency after surgery. |
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| Ulnar deficiency after surgery. |
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| Ulnar deficiency after surgery. Pins still in place. |