Over the last several blogs, I have been reviewing the use of external fixation for pediatric foot and ankle surgery. I discussed using this technique for non-elective cases such as fracture management. Last month I talked about elective application, more specifically for the use of lateral column lengthening and for brachymetatarsia. Both of these procedures use the Ilizarov technique of callus distraction and that will be the focus of this month’s blog.
I have a word of caution before you consider this technique. If you haven’t been trained to do these procedures with external fixation, please participate in a workshop to get your hands on the equipment. Have a colleague who has experience with this sort of equipment help you in the operating room the first few times before attempting this procedure on kids.
One of the advantages with this technique is that with experience, one may use a minimal incision approach. The technique involves stab incisions to place the pins for the external fixation and then a small incision to make the necessary osteotomy. The surgeon does all this under the direction of a mini or regular C-arm.
Osteotomy placement is also important in these procedures. For the Evans procedure, place the osteotomy between 5 mm and 15 mm proximal to the calcaneocuboid joint. The distance will vary based on your training. There is controversy about osteotomy placement for the lengthening of the metatarsal. Some make the osteotomy at the surgical neck and others make it more toward the base of the metatarsal. I have had better success with the osteotomy at the base of the metatarsal as there is more vascularity there and it also limits how much the metatarsal can rotate. I have seen some cases where the surgical neck osteotomy placement has caused rotation of the head as it heals.
There are three stages of manipulation when going through the Ilizarov technique. The first phase involves compression of the osteotomy to stimulate osteoblastic activity at the osteotomy site. The recommendation is to allow this compression stage to last between seven and 10 days. However, I have found this can be too long in the pediatric population as I have seen osteotomies close in this timeframe. I will usually only let this stage go until the first postoperative appointment five days after surgery.
At this point, it is time to start the distraction stage of the technique. I recommend distracting the osteotomy 1 mm per day until it is at the desired length. I generally have my patients do one-quarter turn of the device’s screw system four times a day. This gives the desired 1 mm per day and still preserves the neurovascular bundles during distraction. If you distract the osteotomy too quickly, it can damage the neurovascular bundles permanently.
Once you distract the osteotomy to the desired length, I recommend that you maintain the device to that length for the same amount of time it took to reach that length. So theoretically, if you wanted 1 cm of length, you would distract the osteotomy for 10 days and then leave the device on for another 10 days at the fully distracted length. I have found it is better to do serial radiographs to determine when to remove the device and one can do this in the office.
Next month, I will talk about some pearls for pre-, peri- and postoperative management and education of the patients and their families. As always, please e-mail me with questions at firstname.lastname@example.org .