How to diagnose and manage an acute Achilles tendon rupture

The Achilles tendon is the most commonly ruptured tendon in the body.¹ It is also the largest and strongest tendon.^2,3 Rupture of the Achilles tendon is a disabling injury that can vary in complexity.

Anyone can rupture his or her Achilles tendon; however, athletes who play running sports, such as softball, basketball, or soccer, or racket sports, such as racquetball or tennis, are most likely to incur this injury.⁴ Additional risk factors for acute rupture include preexisting conditions, such as tendinosis and Haglund's deformity; participation during learning phase of a new physical activity; administration of corticosteroid injections into the Achilles tendon; use of oral corticosteroid therapy to treat inflammation or pain; age 30 to 50 years; and use of fluoroquinolones.⁵

The mechanism of injury is usually an abrupt change in direction and speed with a stop-short-and-go action. The acute injury is described as the feeling of being kicked or hit on the back of the ankle and lower calf muscles from behind. An Achilles tendon rupture is painful, heals slowly, and requires long-term follow-up. Treatment options are casting, functional bracing, and/or surgery. Patients must walk with crutches for an extended period of time, which can severely limit activities of daily living. Patients may also experience additional soft-tissue damage from the acute injury and postoperative complications, including rupture recurrence.

ANATOMY AND PATHOPHYSIOLOGY

The Achilles tendon forms from the distal ends of the gastrocnemius and soleus (calf) muscles and inserts at the superior posterior aspect of the calcaneus. The plantar fascia on the bottom of the foot is anchored to the inferior aspect of the calcaneus, which forms the tendocalcaneal junction (the bone and soft tissues at the ankle). Dorsiflexion and plantar flexion of the foot occur when the Achilles tendon pulls against connective tissue of the plantar fascia. Blood supply is carried to the Achilles tendon via the calf mus cles and at the tendocalcaneal junction.

Rupture of the Achilles tendon can occur with an abrupt dorsiflexion of the foot; a rapid, forced plantar flexion; then dorsiflexion of the plantar-flexed foot.⁵ Most tears occur approximately 3 to 6 cm proximal to the insertion at the calcaneus because this area has the lightest vascular flow4 (Figure 1). The major blood vessel to the Achilles tendon is the posterior tibial artery. The ability to plantar flex the foot is controlled by the tibial nerves S1 and S2. A severed Achilles tendon provides no tension to hold the foot up, leaving the foot in plantar flexion.

Achilles tendinopathy includes two types of tendinitis that can occur at the tendocalcaneal junction: Insertional tendinitis manifests where the Achilles tendon is anchored on the calcaneus. Noninsertional tendinitis manifests in the areas proximal to the retrocalcaneal bursa.⁶ Haglund's deformity is a protuberance of bone originating on the calcaneus at the tendocalcaneal junction. Haglund's deformity becomes more of a concern over time, as it rubs against the Achilles tendon at the posterior heel when a person is wearing shoes and promotes a cyclic inflammatory process. Thus, it can be a contributing factor in Achilles tendinopathy. Haglund's syndrome results when a patient with the deformity develops pain and swelling in the posterior aspect of the ankle.

Sports that incorporate running activities involve a constant alternation between dorsiflexion and plantar flexion. A weak area in the Achilles tendon coupled with a strong force can result in a rupture. A sudden takeoff from a stopped position puts a significant amount of force through the Achilles tendon. Still, many patients say that they were running when the injury occurred, and they looked to see who hit them from behind because the injury can mimic a kick.⁷ The rotational motion used on elliptical trainers, bicycles, and when swimming are safer exercises for the Achilles tendon than running and jumping.

PHYSICAL EXAMINATION

The Simmonds' test, also known as the Thompson test, is a gross screening examination for an Achilles tendon rupture. The patient lies prone on the examination table with the feet and ankles positioned over the edge of the table. In a person with an intact Achilles tendon, the foot should move into plantar flexion when you squeeze the calf muscles bilaterally. No movement in the foot indicates a rupture. This is a modified technique used by some clinicians; the standard technique is to flex the knee 90° with the patient prone and squeeze the calf, observing for plantar flexion.⁷

The acute Achilles tendon rupture is a closed wound unless the tendon was cut by an external object or as a result of a penetrating injury. Patients often present with swelling in the posterior ankle, foot, and toes (Figure 2); pain can be variable. The foot on the affected leg is more equinus than the unaffected leg when the patient sits on the examination table. Patients who have not elevated the foot or applied ice before the examination may have significant swelling. The neurovascular status of the injured leg must be checked for signs of vascular compromise and neuritis. Most patients cannot resist passive dorsiflexion of the foot because a complete rupture drastically weakens the ankle. Some patients with a partial tear can resist dorsiflexion but with obvious weakness compared to the degree of resistance in the uninjured leg. Thus, muscle strength in the affected ankle would be less than 5/5 on physical examination. The examiner can often feel the defect when palpating the contour and shape of the Achilles tendon. People with a marked Haglund's deformity have a palpable prominence on the back of the lower leg at the tendocalcaneal junction. However, the prudent clinician performs a thorough orthopedic examination of all limbs, especially both lower limbs, to decrease the probability of missing other injuries.

DIAGNOSTIC TESTS

Conventional plain film radiographs are of limited usefulness unless Haglund's deformity, a fracture, or presence of a foreign body is suspected. In uncomplicated cases, health care providers rely on the physical examination to make the diagnosis. MRI is obtained only if trauma to other soft-tissue structures is suspected. However, a more cost-effective method of evaluating the thickness and shape of an Achilles tendon is musculoskeletal ultrasonography (US). Traditionally, US is quick and does not use ionizing radiation.⁵ CT is used regularly to confirm fractures and osteochondral lesions, but it is not commonly used to evaluate acute Achilles tendon rupture. Thus, radiographic studies are the most effective adjuncts to the history and physical examination.