CHAPTER SYNOPSIS:

Nonoperative treatment of subtalar arthritis can maintain function and avoid surgery. Indications for bracing and injections are covered. Nonoperative treatment should always precede any surgical intervention of subtalar arthritis.

IMPORTANT POINTS:

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  Orthotics are of benefit in the patient with a flexible foot and impingement. However, the most effective way of reducing pain in the subtalar joint is to reduce the motion using a brace or taping. This may be as simple as an off-the-shelf lace-up brace, or it could be a custom-made patellar tendon–bearing ankle foot orthosis.

  
  
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  Injections may also play a role as long as the joint is deemed unsalvageable. Hyaluronic acid may be injected into the salvageable joint and may have a longer duration of benefit than steroids.

CLINICAL/SURGICAL PEARLS:

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  Oral agents shown by placebo-controlled studies to be effective for the treatment of knee arthritis (and therefore potentially beneficial in foot arthritis) include acetaminophen (Tylenol), nonsteroidal anti-inflammatory drugs, chondroitin sulfate, glucosamine sulfate, and opioid analgesics.

  
  
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  The first four medications have a short-term therapeutic effect and are well tolerated. The last has some effect on pain but is poorly tolerated because of side effects.

CLINICAL/SURGICAL PITFALLS:

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  Recent information on the toxicity of local anesthetic agents on cartilage limits their use to unsalvageable joints.

VIDEO AVAILABLE:

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HISTORY/INTRODUCTION/SCOPE OF THE PROBLEM

The incidence of subtalar arthritis is unknown. The rate of subtalar fusion in our province is between 120 and 160 procedures per year, or 30 subtalar fusions per 1 million population. This rate would translate to 9000 subtalar fusions per year in the United States.

INDICATIONS/CONTRAINDICATIONS

Nonoperative treatment should be maximized in patients with any source of subtalar pain.

ANATOMY

The subtalar joint is between the calcaneus and talus. It is composed of three facets, although in some patients the medial and anterior facets can be joined as a single facet. The posterior facet is the largest and the usual source of pain. The posterior facet is shaped like the section of a cone with the tip of the cone on the medial side of the ankle. The axis points posteriorly and laterally. The medial facet acts as a fulcrum around which the posterior facet rotates, changing the relative height of the medial and lateral border of the foot.

As the calcaneus internally rotates on the talus, the lateral border of the foot is pushed forward and the talus rides up the slope of the calcaneus on the lateral side. The combined height of the talus and calcaneus laterally increases, forcing the hindfoot into inversion. The motion of the subtalar joint is a complex combination of rotation medially in the middle facet and translation laterally on the posterior facet.

RELATIONS

The lateral side of the posterior facet lies next to the calcaneofibular ligament, forming a thickened area in the lateral capsule. The peroneus longus lies over the ligament inferior and posterior to the brevis tendon. Both pass close to the lateral joint margin. The tip of the fibula is superior to the lateral joint margin.

Anterior to the posterior facet lies the sinus tarsi. The interosseous ligament borders the capsule at this point, and it can be impinged on by the anterior process of the talus in extreme eversion of the hindfoot.

The posterior margin of the joint lies anterior to the tendon of flexor hallucis longus. Just medial to this lies the tibial nerve and the tibial artery. Both lie in the posterior medial aspect of the posterior facet.

The flexor digitorum longus and tibialis posterior tendons pass medial to the medial facet, superficial to the deep deltoid ligament that lines the medial facet. All lie inferior to the medial malleolus.

Anterior to the anterior facet lies the spring ligament and the talonavicular joint.

KINEMATICS

The subtalar joint allows the hindfoot to be inverted and everted, in conjunction with the talonavicular joint. The calcaneocuboid joint also moves with the subtalar joint but is less critical on subtalar motion than the talonavicular joint. A block of talonavicular motion will result in almost no motion at the subtalar joint.

DIFFERENTIAL DIAGNOSIS OF SUBTALAR JOINT PAIN

Most often, ankle joint pain may need to be differentiated from subtalar joint pain. Pain may also exist in both joints concurrently, and the most symptomatic joint may need to be determined. Isolated motion of the subtalar followed by the ankle may be the best differentiator of discomfort in each joint.

Ankle joint pain is typically more proximal and anterior in location. Swelling will follow the anterior margin of the ankle. Ankle joint pain is located proximal to the malleoli. Subtalar joint pain is distal and inferior to the malleoli.

On the lateral side of the subtalar joint lie the peroneal tendons. Pain in the peroneal tendon area can be confused for pain in the lateral side of the posterior facet.

A planovalgus foot can also cause pain in the sinus tarsi region. In this case, the pain will be localized just anterior to the lateral margin of the posterior facet, and there will be no discomfort on passive motion of the ankle unless the ankle is fully everted.

The calcaneocuboid joint also lies anterior and lateral to the sinus tarsi. Pain in this region can be confused for subtalar joint pain.

The subtalar joint can cause pain on its medial margin. On the medial side, the flexor hallucis longus, the flexor digitorum longus, and the posterior tibial tendon pass next to the medial facet. Tendonitis in this area can therefore confuse the physician.

Other sources of hindfoot pain include the Achilles tendon, plantar fascia, and talonavicular joint.

HISTORY AND PHYSICAL EXAMINATION

The patient should have both feet exposed to the level of the knees. Initial observation should be performed with the patient standing and walking. The hindfoot and forefoot position should be observed as the patient stands. Excessive hindfoot varus may be indicated by a peek-a-boo heel sign observed from the anterior ( Fig. 24-1 ). An excessively laterally translated forefoot in a planovalgus foot will be indicated by a too-many-toes sign observed from behind the patient.

An ankle demonstrating hindfoot varus via the “peek-a-boo” heel sign.

The patient should be asked to heel walk and toe walk. Excessive subtalar joint pain may prevent toe walking.

The patient should be asked to perform a single-legged heel raise. The patient may not be able to invert the hindfoot if the tibialis posterior tendon is disrupted. The patient may also fail to invert the hindfoot if the posterior tibial tendon is intact but the hindfoot is everted to the point that the lateral pull of the Achilles cannot be overcome by the tibialis posterior tendon. Inversion may be prevented if the subtalar joint does not move, such as in talocalcaneal tarsal coalitions. Finally, the subtalar joint may be too painful for the patient to tolerate the load of a single heel raise.

Subtalar joint pain is usually localized to just under the medial and lateral malleolus. The subtalar joint has both medial and lateral margins.

Palpation of these margins will determine if the source of pain is coming from the subtalar region.

The subtalar joint can be moved in isolation by holding the talar neck in the examiner’s left hand with the calcaneus held in the right hand ( Fig. 24-2 ). The subtalar joint will move in isolation. The range of motion can be determined, and the examiner can also determine if the subtalar joint is the source of pain.

Examination of subtalar joint motion. The left hand immobilizes the talar neck, and the right hand cups the calcaneus. Inversion and eversion at this level should move the subtalar joint alone.

Pain in the sinus tarsi on its own does not mean that the subtalar joint is the source of the pain. The lateral process of the talus can impinge on the calcaneus and cause pain in the planovalgus foot ( Fig. 24-3 ).

Subtalar impingement in a planovalgus foot. This impingement will cause lateral ankle pain next to a subtalar joint while the subtalar joint itself is not arthritic. Image is magnified and cropped.

Resisted eversion of the foot will determine if the pain is coming from the peroneus brevis. Resisted plantar flexion of the first ray will determine if the pain is coming from the peroneus longus.

Pain from anterior lateral impingement in the ankle will be located just superior to the subtalar joint at the junction of the talus, fibula, and tibia.

A painful os trigonum or posterior talar process will be painful during forced plantar flexion of the ankle. The pain will be localized posterior to the subtalar joint. The pain will be best localized from the medial side.

Flexor hallucis longus tenosynovitis will cause pain in the fibro osseous tunnel on the medial border of the posterior talar process. Resisted plantar flexion of the great toe will cause discomfort.

Tibialis posterior tendonitis will cause pain more medially and superiorly located than the medial joint line of the subtalar joint. The medial margin of the subtalar joint is located just above the sustentaculum tali.

The examination is completed by an examination of the surrounding joints. A neurovascular examination, including monofilament testing, completes the examination.