Understanding How The Lateral Ankle Triad Comes Into Play With Chronic Ankle Instability

Babak Baravarian, DPM, and Lindsay Mae Chandler, DPM

   Ankle instability may be defined as functional or mechanical. Functional instability is the subjective feeling of giving way of the ankle joint with the etiology being a proprioceptive disorder secondary to previous ankle injury resulting in motion beyond voluntary control but not exceeding physiologic range of motion. Proprioceptive exercises along with peroneal muscle strengthening are successful in treating functional instability. The objective measurement of instability or motion beyond the physiological range of motion is mechanical instability. One may use the anterior drawer and talar stress tests to quantify the degree of mechanical instability.

When There Is An Incomplete Diagnosis

At the University Foot and Ankle Institute, we have termed the lateral ankle “unhappy triad” as a combination of findings that frequently occur together: ankle instability, ankle synovitis and peroneal tendon tear.11 Frequently, clinicians make a single diagnosis based upon the mechanism of injury and when this diagnosis is incomplete, it may lead to suboptimal treatment. Accordingly, one would see incomplete healing, chronic pain, swelling and recurrence as a result.

   Common threads among patients with prolonged pain, swelling and instability of the lateral ankle are chronic ligamentous tears with associated peroneal tendon pathology ranging from tenosynovitis to tendinosis and ultimately tendon tears. Chronic tendon tears may result from repetitive activities in the presence of chronic ankle instability. The additional excursion available at the ankle joint over time can lead to synovitis and anterolateral fibrous bands.

Keys To Effectively Diagnosing And Treating The Lateral Ankle Triad

Treatment begins with a thorough history and physical. Typically, patients will present with a history of single or multiple ankle sprains, persistent pain and/or swelling, and a sense of instability in the ankle. Localized edema tends to be present about the anterolateral ankle joint and sinus tarsi regions, overlying the anterior talofibular ligament. One can appreciate point tenderness directly over the injured ligament(s) and tendon tear. Stress maneuvers of the ankle are key to incorporate in your workup. The anterior drawer test evaluates the strength of the anterior talofibular ligament. Increased anterior migration of the talus on the tibia is a strong indicator of the presence of a tear or attenuation of the anterior talofibular ligament.

   Imaging studies begin with weightbearing radiographs of the foot and ankle to rule out other pathology. We highly recommend stress radiographs such as the anterior drawer and talar tilt images, and one can compare them with the asymptomatic contralateral side. Magnetic resonance imaging (MRI) can rule out osteochondral lesions and is sensitive as well as specific in detecting pathology in the lateral collateral ligaments and the peroneal tendons. However, MRI is less consistent in identifying synovitis, fibrous bands and small loose bodies.

   We implement non-surgical care in all cases prior to surgery, including brace immobilization and physical therapy for a minimum of three months. When pain perseveres, surgical treatment consists of a combination of ankle stabilization, ankle arthroscopy and peroneal tendon repair. All cases begin with ankle arthroscopy including debridement of synovitic tissue, fibrous bands and loose bodies. We follow this with an open technique for lateral ankle stabilization and peroneal tendon repair.

   Postoperatively, we have the patients use a non-weightbearing cast for six weeks followed by a below-the-knee controlled ankle motion (CAM) walking boot for an additional two weeks. At week six, the patient can start physical therapy and at week eight, patients can transition out of the boot into a tennis shoe with an ankle brace. One can allow a full return to athletic activity at three months.

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