Adult-Acquired Flat Foot Deformity (AAFFD) is most commonly caused by a progressive degeneration of the tendon (tibialis posterior) that supports the arch of the foot. As the tendon ages or is subjected to repetitive trauma, it stretches out over time, the natural arch of the foot becomes less pronounced and the foot gradually flattens out. Although it is uncertain why this occurs, the problem is seen equally among men and women - at an increasing frequency with age. Occasionally, a patient will experience a traumatic form of the condition as a result of a fall from a height or abnormal landing during aerial sports such as gymnastics or basketball.
There are a number of theories as to why the tendon becomes inflamed and stops working. It may be related to the poor blood supply within the tendon. Increasing age, inflammatory arthritis, diabetes and obesity have been found to be causes.
Pain along the inside of the foot and ankle, where the tendon lies. This may or may not be associated with swelling in the area. Pain that is worse with activity. High-intensity or high-impact activities, such as running, can be very difficult. Some patients can have trouble walking or standing for a long time. Pain on the outside of the ankle. When the foot collapses, the heel bone may shift to a new position outwards. This can put pressure on the outside ankle bone. The same type of pain is found in arthritis in the back of the foot. Asymmetrical collapsing of the medial arch on the affected side.
Clinicians need to recognize the early stage of this syndrome which includes pain, swelling, tendonitis and disability. The musculoskeletal portion of the clinical exam can help determine the stage of the disease. It is important to palpate the posterior tibial tendon and test its muscle strength. This is tested by asking patient to plantarflex and invert the foot. Joint range of motion is should be assessed as well. Stiffness of the joints may indicate longstanding disease causing a rigid deformity. A weightbearing examination should be performed as well. A complete absence of the medial longitudinal arch is often seen. In later stages the head of the talus bone projects outward to the point of a large "lump" in the arch. Observing the patient's feet from behind shows a significant valgus rotation of the heel. From behind, the "too many toes" sign may be seen as well. This is when there is abducution of the forefoot in the transverse plane allowing the toes to be seen from behind. Dysfunction of the posterior tibial tendon can be assessed by asking the patient to stand on his/her toes on the affected foot. If they are unable to, this indicates the disease is in a more advanced stage with the tendon possibly completely ruptured.
Non surgical Treatment
Medical or nonoperative therapy for posterior tibial tendon dysfunction involves rest, immobilization, nonsteroidal anti-inflammatory medication, physical therapy, orthotics, and bracing. This treatment is especially attractive for patients who are elderly, who place low demands on the tendon, and who may have underlying medical problems that preclude operative intervention. During stage 1 posterior tibial tendon dysfunction, pain, rather than deformity, predominates. Cast immobilization is indicated for acute tenosynovitis of the posterior tibial tendon or for patients whose main presenting feature is chronic pain along the tendon sheath. A well-molded short leg walking cast or removable cast boot should be used for 6-8 weeks. Weight bearing is permitted if the patient is able to ambulate without pain. If improvement is noted, the patient then may be placed in custom full-length semirigid orthotics. The patient may then be referred to physical therapy for stretching of the Achilles tendon and strengthening of the posterior tibial tendon. Steroid injection into the posterior tibial tendon sheath is not recommended due to the possibility of causing a tendon rupture. In stage 2 dysfunction, a painful flexible deformity develops, and more control of hindfoot motion is required. In these cases, a rigid University of California at Berkley (UCBL) orthosis or short articulated ankle-foot orthosis (AFO) is indicated. Once a rigid flatfoot deformity develops, as in stage 3 or 4, bracing is extended above the ankle with a molded AFO, double upright brace, or patellar-tendon-bearing brace. The goals of this treatment are to accommodate the deformity, prevent or slow further collapse, and improve walking ability by transferring load to the proximal leg away from the collapsed medial midfoot and heel.
Surgical treatment should be considered when all other conservative treatment has failed. Surgery options for flatfoot reconstruction depend on the severity of the flatfoot. Surgery for a flexible flatfoot deformity (flatfoot without arthritis to the foot joints) involves advancing the posterior tibial tendon under the arch to provide more support and decrease elongation of the tendon as well as addressing the hindfoot eversion with a osteotomy to the calcaneus (surgical cut in the heel bone). Additionally, the Achilles tendon may need to be lengthened because of the compensatory contracture of the Achilles tendon with flatfoot deformity. Flatfoot deformity with arthritic changes to the foot is considered a rigid flatfoot. Correction of a rigid flatfoot deformity usually involves surgical fusion of the hindfoot joints. This is a reconstructive procedure which allows the surgeon to re-position the foot into a normal position. Although the procedure should be considered for advanced PTTD, it has many complications and should be discussed at length with your doctor.