Is Peroneal Spastic Flatfoot Causing Chronic Ankle Pain?

By Mark A. Caselli, DPM

Essential Diagnostic Pointers
When attempting to pinpoint the etiology of peroneal spastic flatfoot, radiographic modalities remain the most beneficial diagnostic tools. Plain film radiography should be your initial screening tool for any young patient who has a rigid or semirigid foot, especially when you suspect tarsal coalition. The radiographic appearance of tarsal coalition depends on its site and whether it is bony or fibrocartilagenous. Be sure to include dorsoplantar, lateral and oblique projections among your initial radiographs. These reveal coalitions between the talus and navicular, and between the calcaneus and the cuboid.
For calcaneonavicular coalitions, the best view is a 45-degree oblique view of the foot made with the patient standing and the X-ray projected through the middle of the foot from the lateral to the medial side.
Getting an axial view of the calcaneus is necessary to reveal a talocalcaneal coalition. However, because it is often difficult to get a good axial view, the CT scan is the standard for radiographic diagnosis of the talocalcaneal coalition. Beaking on the dorsal and lateral aspect of the head of the talus adjacent to the talonavicular joint is a common secondary change in tarsal coalition. This talar beak appears to be produced by the impingement of the dorsal part of the navicular on the head of the talus during dorsiflexion.
Regardless of the precipitating factor, most authors agree that the peroneal muscles contract or shorten as a protective mechanism to reduce or eradicate pain. The musculature splints the subtalar and ankle joints against discomfort or pain, maintaining an everted attitude of the rearfoot. This splinting results in an adaptive, functional shortening with tautness or contracture of the involved muscles. The peroneus brevis muscle is most often implicated but the peroneus longus, peroneus tertius and the extensor digitorum longus muscles may also exhibit contracture in peroneal spastic flatfoot.

What To Consider For Treatment
When you see a young athlete with peroneal spastic flatfoot, it very important to clearly define treatment goals with both the athlete and parents, since the eventual return to full sports activity may not be attainable, especially if certain tarsal coalitions are involved. The progression of the treatment program should be as follows:
1) eliminate pain;
2) enable the youth to return to school and participate in all non-athletic school functions;
3) limited participation in athletic school functions, such as physical education classes; and
4) return to previous sports activities.
To facilitate initial symptomatic relief in a young patient, you may recommend rest, nonsteroidal antiinflammatory drugs, muscle relaxants, paraffin baths, heat, warm soaks and whirlpool.
With further conservative treatment, you want to decrease the motion of the painful joints in order to help alleviate pain. When a patient has moderate to severe pain on ambulation, using a below-the-knee cast is recommended for three to four weeks. You can combine this with a common peroneal nerve block and an injection of steroid and anesthetic into the sinus tarsi, which are effective in both relieving pain and muscle spasm.
Upon removing the cast, you should place the patient in orthotic devices and modified shoes that increase the support to the medial side of the foot.
Using a leather laminate foot orthosis with a deep heel seat and high medial and lateral flanges is recommended. This type of device offers good support but will deform to allow for foot pressure areas. Be aware that patients with peroneal spastic flatfoot usually cannot tolerate hard, rigid orthoses. You can modify shoes with 1/8- to 3/16-inch inner heel and inner sole wedges. You should also consider physical therapy for ankle strengthening exercises, range of motion exercises to increase inversion and other techniques to decrease pain.
Between 30 and 90 percent of patients have been reported to respond to nonoperative conservative treatment of tarsal coalitions. Most authors believe in exhausting or at least trying conservative care before any surgical intervention, although there are some that stress the importance of surgery as soon as possible.

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