The indications for this procedure is the correction of a deformity whereby the front and mid part of the foot is splayed to the outside (abducted). This deformity is often seen in a flatfoot deformity or a deformity in children associated with a tarsal coalition.
The Evans procedure is performed to correct a specific deformity of the foot. When the foot is splayed out to the side, it can sometimes be helpful to lengthen the outside column (lateral column) of the foot, pushing the front of the foot into a more neutral position. The Evans procedure itself involves making an incision on the outside of the foot just near the front of the ankle. The front part of the heel bone (calcaneus) is then cut. This bone is then pried apart 8 to 10 mm, and a bone graft either from the pelvis or from a cadaver is used to maintain this lengthening. The cut (osteotomy) for the Evans procedure is performed just behind the calcaneal cuboid joint. By making the cut through the front part of the calcaneus bone instead of lengthening and fusing through the calcaeno-cuboid joint, the motion of this joint can be maintained. The Evans procedure is often performed in conjunction with other procedures in order to have a more complete correction of an acquired adult flatfoot deformity. These other procedures may include a calcaneal osteotomy, a flexor tendon transfer to the posterior tibial tendon or an Achilles lengthening, or gastrocnemius resection.
This procedure involves cutting (osteotomizing) a bone (calcaneus) in the foot. For the procedure to be effective, the bones must knit together. This usually takes six to eight weeks of healing time. During this time, it is usually necessary to keep the area immobilized and weight off of the foot. Once the area has healed enough to bear weight, the patients are often placed in a walking boot and they are asked to gradually increase their activities over a further six to eight week period. It is often a year or more before a full recovery is achieved.
Complications that may occur with the Evans procedure that are specific to this procedure include:
- Malunion: Over or under lengthening of the bone cut can be problematic. Under lengthening will result in an incomplete correction of the deformity. Over lengthening can result in a foot that is painful and stiff. It is not uncommon even in a well performed Evans procedure for the patient to have significant stiffness and discomfort for many months after this surgery, as the foot accommodates to the new position.
- Pain associated with the lateral hind foot: There can be pain associated with the lateral hind foot where the procedure is performed. This can occur because there is now increased pressure to the calcaneal cuboid joint. This is what is known as lateral column overload.
- Painful Hardware: The bone graft needs to be fixed and placed, either with screws or a plate. These can start to irritate the soft tissue in this area which has relatively little padding.
Edited April 24, 2015