Radial Longitudinal Deficiency
Hi, my name is Charles Goldfarb. I'm an Orthopedic Surgeon at Washington University in St. Louis. I see patients at the Orthopedic Center of Chesterfield, St. Louis Children's Hospital and the Shriner's Hospital for Children. Kids born with hand and upper extremity abnormalities often come to these sites to see me for evaluation and treatment.
Radial longitudinal deficiencies are complex abnormality of the upper extremity. It's named for the lack of the radius bone which is the thumb side of the forearm bone but is much more complex and intricate than that. All the muscles, tendons, nerves are affected in the forearm and often in the hand as well making it very complex and so treatment is based upon the exact abnormality that exists. We classify radial deficiencies based on the bony abnormality, but again, all of the other factors have to be considered when one plans treatment for children born with radial deficiency.
It is something that happens early in gestation. So around 26 to 32 days of gestation, the abnormality occurs and it's a signaling problem which is based in the developing limb bud. Something called sonic hedgehog doesn't communicate well with the rest of the developing limb bud leading to the abnormality. Children are born, and usually it's obvious, usually you see a marked deformity of the wrist, but sometimes it can be more subtle and may not show up until later in childhood. Radial longitudinal deficiency is uncommon and we don't have a firm understanding of the exact incidence numbers in the United States, but is estimated to be approximately 1 in 10,000 live births.
When I first see a child with radial deficiencies, several things go through my mind. First, I want to evaluate the exact deficiency and better understand what the child has functionally and how the hand and forearm work but almost more importantly is that I want to make sure there are no other associated medical abnormalities. Because of the timing of this insult and again, that's early in gestation, other organs can be affected and so it's not uncommon to see children with heart problems, kidney problems, spine problems, tracheal problems and so all of these issues must be evaluated so we take great care to evaluate and send a child to a geneticist or to a pediatrician to perform different testing to assure no other medical abnormalities exist.
Part of the spectrum of radial deficiency as we've already discussed is the forearm, but the thumb can also be affected in radial deficiency as well. The thumb can be smaller than normal or can be absent completely. If a thumb is absent, we typically reconstruct the thumb by using the index finger and rotating it into the position of a thumb. That's called a pollicization procedure. The main procedure for a stabilizing the forearm is called a centralization procedure and by that, we take a deviated forearm and we place the hand and wrist on the end of the ulna bone to try to make a more normal and highly functioning hand.
We started treating those patients in a two-step process. The first step is the application of what we call an external fixator which stabilizes the forearm to the hand and allows us to straighten and stretch the structures in the forearm over several weeks to several months. We then take the fixator off and do a procedure to further stabilize the wrist onto the forearm.
We've made great strides in treating children with radial deficiency. I believe a two step process of the fixator followed by the surgical intervention on the wrist has been very effective. It's allowed for a better functional outcome, a better appearance outcome and hopefully, less recurrence over time. One of the things we fought over the years is that while we may correct the child and create a straight wrist, over time, that wrist can deviate backwards to where it started. The newer treatment options seem to allow us to keep the wrist in a straighter position for a longer duration of time.