External fixators are devices that rest outside of the skin. They can be used to stabilize broken bones (although not used very often for this purpose today) or to correct a short or angled extremity/ bone. We use fixators to lengthen small bones such as the thumb to allow pinch or to grow the forearm to assure that the two bones of the forearm are nearly the same length. The forearm is interesting because if the bones are not the same length, the wrist can deviate and/ or the elbow can dislocate or shift out of position. Neither of these are good. So, if we can avoid those problems by lengthening the short bone, it can be a real help. I have previously blogged about fixators of different varities HERE.
There are three common reasons why we lengthen a forearm bone
1) Multiple hereditary exostosis (MHE). In this case, the ulna is often short and the radius is at risk for dislocating at the elbow. See my other posts on this topic HERE.
2) Radial longitudinal deficiency (RLD). In this case, the radius is short and, if there is a radius present, it can be lengthening to balance the wrist. See other posts HERE.
3) A trauma or injury which affects the growth plate of the radius. This may be a fracture near the growth plate of the distal radius which affects growth and leads to a long ulna. Or, an infection of the growth plate can have the same effect.
This patient had multiple infections around the time of birth. The infection affected her thumb and index finger and has led to a short radius. We have elected to lengthen her radius with a fixator to achieve balance and hopefully avoid future problems. Here are x-rays showing the short radius bone.
|Short radius related to infection affecting the growth plate|
At the time of surgery, we applied a fixator to lengthen the bone.
|External fixator to lengthen the radius. The cut in the one (osteotomy) is visible- this is where we will lengthen the bone
The idea is that with slow stretching of the bone, the bone will grow. Typically we ‘turn
the dial’ on the fixator 2-4 times each day. This lengthens the bone from 1/2 of a millimeter to a full millimeter each day. We do this slowly to allow the body to make enough bone so that after we lengthen (and then give the bone time to get stronger), we can remove the fixator and the bone will be strong! The fixator is on the arm different times for each patient depending on how much length is needed and how much bone is created.
This young lady shows that the fixator is no big deal! She has had her fixator about 2 weeks and is doing really, really well with it. Super cute and, surprisingly, a little shy here.