Director of the Advanced Foot And Ankle Center of San Diego
He specializes in deformity correction of the Foot and Ankle. He was fellowship trained in limb lengthening and reconstruction at the international center for limb lengthening in Baltimore Maryland. He is Board certified by the American Board of Foot and Ankle Surgery in Foot and reconstruc tive Rearfoot/Ankle Surgery, and is a fellow of the American College of Foot And Ankle Surgeons.
The Charcot foot can be quite a vexing problem. As we all know, the challenge is not just treating a Charcot foot, but also the patient attached to that foot. This has led to many treatment algorithms and approaches, from total contact casting to a CROW (Charcot Restraint Orthotic Walker) boot to various surgical approaches. While a non surgical approach has its advantages many times the patient will refuse to wear a CROW boot, or the patient will continue to break down from ulcers due to a rocker bottom foot, that is non responsive to treatment by a total contact cast or CROW boot. Surgical approaches that have been used range from simple ostectomies to remove pressure loading areas of the foot, all the way to reconstructing the foot into an optimal biomechanical functioning limb.
Our discussion in this article will focus on the latest techniques l reconstruction of the charcot foot. The first step with patients affected by this process is to ascertain their overall medical health including HBA1C’s, infection status and that they are medically stable. Next before embarking on this journey with the patient is to have a lengthy discussion as to if they are mentally prepared for a reconstruction. Reason being is that the reconstruction will sometimes take 2-3 surgeries. And as we well know there is never a guarantee with these surgeries and the patient may end up with a non satisfactory result or even worse an amputation. An understanding of their home support situation is vital. Do they have help , are they married, you can not do a surgery like this and then send them home to take care of themselves.
Next is analysis of the deformity that you are dealing with. These deformities must be treated with precise angular and numerical calculations, eyeballing an x ray will only lead to creating secondary deformities and failed surgeries, as well as new ulcerations. If you can not put a number to it, then it is not science. An understanding of CORA Center of Rotation of Angulation (CORA method) and the Axis of Correction of Angulation (ACA Method) are vital to performing deformity correction. After you find the apex of the deformity with regard to the Charcot foot the surgeon needs to put numerical values to the extent of the deformity. Another important reason for these angles is to recognize that the more angular correction you attempt then the more you will be pulling on nerves arteries and veins. This is the underlying principle for gradual deformity correction of these feet. If the surgeon will gradually perform the correction then there will be less instances of arterial and nerve damage post correction. This is opposed to acute correction of the deformity where the surgeon corrects all aspects of the deformity on one fell swoop, thus increasing the risks for nerve and vascular damage.
First you will need to calculate the Meary’s angle (It is the angle between a line drawn from the center of longitudinal axes of the talus and the first metatarsal. In the normal weight-bearing foot, the midline axis of the talus is in line with the midline axis of the first metatarsal. Normally Meary’s angle is 0 degrees).
This angle will help you understand how much correction you will be making in the sagittal plane. In the above picture, Figure 1, you will note a 35 degree angular deformity of the Meary’s angle. That means the structure at risk will need to move 35 degrees to re align the Meary’s angle. The structure at risk is the dorsalis pedis artery. If one performs an acute correction, they risk putting an excessive stretch on the dorsalis pedis. Thereby necessitating the use of gradual deformity correction. Here is another large Meary’s deformity (Figure 2)
The next item to calculate is the amount of equinus that will need to be corrected. The image, (Figure 3) shows a Diabetic with an isolated fracture of the calcaneus which has resulted a calcaneal inclination angle of 19 degrees in a rocker position. Therefore the overall correction, in order to create a normal calcaneal inclination angle of 24 degrees will require a 43 degree correction. That means the structures at risk will be pulled 43 degrees. The structures at risk in this case is the posterior tibial artery and nerve. The next evaluation is the amount of abductus or adductus of the foot. In the picture (Figure 4) there is a 30 degree abduction deformity.
The next evaluation is the forefoot to rearfoot valgus or varus relationship. This is important in order to create a tripod effect for the foot. One of the little tricks in performing these corrections is to try to recreate a tri pod for the foot to stand on the three points of the tri pod are the calcaneus the first metatarsal head and the fifth metatarsal head.
The next thing is has the foot shortened. Here (Figure 5) you can see a diabetic foot that has dislocated and shortened by 3 centimeters. An acute correction on this type of foot can be disasterous.
The last is dorsal and plantar dislocation of the forefoot on the hind foot (Figure 7). One must accurately measure the distance that the segments must be moved without putting structures at risk.
Now that the deformities have been analyzed we will move on to the correction portion. Utilization of six axis correction via computer assistance software one can apply an external fixator and present the patient with a prescription for gradual correction of the deformity. As seen in seen in figures 8, 9 and 10.
The above patient was a charcot with total dislocation and shortening of his metatarsals on his foot see figure 11. This is a case where an acute correction would cause vascular damage and would prove very difficult pulling out to length.
An external fixator (Taylor Spatial Frame) was applied, figure 12, and over a 2 month period his foot was pulled out to length.
Once the deformity is corrected the decision is made if internal fixation is needed and what kind. I prefer to either perform a beaming procedure see figure 14, or a super construct of either medial or medial and lateral locking plates. (Figure 15)
In conclusion there is no one way to treat the charcot foot. However when faced with the need to perform surgery one must take into consideration the extent of the deformity and the risks of acute correction. As well as to be able to ascertain whether gradual correction is needed and to be able to give optimal surgical and post surgical care of these patients.