We have come a long way in understanding congenital hand and upper extremity abnormalities. Dr Swanson, more than 40 years ago, published a classification system that was adopted by most of us who treat patients with birth anomalies. This classification system was based purely on appearance of the extremity but allowed us to communicate better as well as advancing the field through research. Recently, Drs Oberg, Tonkin and Manske suggested another classification system still based on appearance but a bit more refined and improved through the last 40 years of research. Eventually we will have a system based not on appearance (phenotype) but based on the genetics (genotype). We have a ways to go.
Our research has allowed us to better understand the origin of many anomalies, but certainly not all. The more we learn, the more we can give good advice to families on 1) associated conditions to look for in their child https://congenitalhand.wustl.edu/2012/04/diagnosis-and-evaluation.html 2) the risk to future children and 3) the risk to the affected child’s future children. We also want to give rest to mothers’ (and fathers) fears that they caused the problem: in almost all cases, this is simply not the case. The more I learn about how limb forms, the more amazed I am that it ever happens “correctly.” There are so many signals and responses and molecules and proteins- simply amazing.
|Combination of cleft hand and forearm synostosis|
|another X-ray of cleft hand and synostosis|
I present only one example in this post. This is a very rare combination of a cleft hand https://congenitalhand.wustl.edu/2012/01/central-deficiency.html and a forearm synostosis https://congenitalhand.wustl.edu/search/label/Synostosisin an otherwise healthy child. The child has been evaluated by genetics on several occasions without identification of any know syndrome or abnormality. The cleft hand appears as a thumb and pinky only. The other hand is normal. The forearm does not rotate as bone unites the proximal portion of the radius and ulna. Why do these 2 anomalies happen together? It is unclear. The cleft hand usually only affects the hand plate. The forearm synostosis often happens in isolation. I believe it is safe to say that the two anomalies happened together for 1 of 2 reasons. First, it may simply have been timing. The forearm bones may have been separating at the same time the central digits were forming- one insult at that critical time caused both. Alternatively, a key signal may not have happened affecting both areas and thus causing both problems. At this point, the error is not clear and we know formation is complex. https://congenitalhand.wustl.edu/2012/10/limb-formation.html One day it might be. I should also point out that these unusual combinations often teach us a great deal because it is unlikely to be coincidence. Unlikely to be lightning striking twice in one unfortunate arm.