Soft Tissue Impingement of the Ankle Joint

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CHAPTER 6 Soft Tissue Impingement of the Ankle Joint

Lateral ligament sprains of the ankle joint are the most common musculoskeletal injury. They are especially common in sports such as ballet dancing, cross-country running, soccer, and basketball. Ankle sprains account for 45% of all injuries in basketball and 31% of all injuries in soccer.¹^–³

After an ankle sprain, anterolateral impingement syndrome is a common cause of continued lateral ankle pain and disability. This syndrome, which has been well documented, occurs in 20% to 40% of patients.¹ The diagnosis is often elusive, especially in ankles that are stable on examination. Morris, who called the condition athlete’s ankle, first described impingement in the ankle in the literature in 1943.⁴ It was later called footballer’s ankle in a report by McMurray.⁵

The pathologic anatomy was first described as soft tissue pathology by Wolin and coworkers in 1950.⁶ They described nine patients with continued pain and swelling of the lateral aspect of the ankle after an inversion injury. Arthrotomy of the ankle in these patients revealed a dense mass of hyalinized connective tissue that extended into the joint from the anteroinferior portion of the anterior talofibular ligament (ATFL). Wolin called this a meniscoid lesion because of its resemblance to a torn meniscus in the knee (Fig. 6-1). He believed pain and disability resulted from entrapment of this tissue between the fibula and talus with dorsiflexion of the ankle. Excision of this tissue resulted in pain relief in all nine patients.

FIGURE 6-1 Partial tearing of the anterior talofibular ligament creates a meniscoid-type lesion that can become trapped in the joint.

Waller ⁷ later described an anterolateral corner compression syndrome that resulted in pain along the anteroinferior fibula and the anterolateral talus. Patients typically had a pronated foot with a valgus heel. This mechanism resulted in a synovial compression and chondromalacia of the lateral aspect of the talar dome. Guhl⁸ described this condition as anterolateral synovial impingement when there is no evidence of ligamentous tissue and only hypertrophied synovium in the pathologic specimen. Andrews and colleagues⁹ emphasized the meniscoid lesion and hypothesized that it was caused by partial tearing of the ATFL. They thought the partially torn ligament became entrapped in the anterolateral gutter. Pain relief was reported with excision of this tissue.

Based on histopathologic analysis, Ferkel and associates ¹⁰ thought the impingement was caused by hypertrophied synovium. Later, Bassett and colleagues¹¹ described a distal fascicle of the anterior-inferior tibiofibular (syndesmotic) ligament (Fig. 6-2). During dorsiflexion of the ankle, this ligament was shown to come into contact with the anterolateral aspect of the talar dome. Presence of this fascicle was confirmed in 10 of 11 cadaveric specimens.

FIGURE 6-2 A Bassett lesion, or distal fascicle of the anteroinferior tibiofibular ligament, comes in contact with the talar dome during dorsiflexion of the ankle.

NORMAL AND PATHOLOGIC ANATOMY

The lateral ligamentous complex consists of the ATFL, the calcaneofibular ligament (CFL), and the posterior talofibular ligament (PTFL). The ATFL arises from the anterior aspect of the distal fibula and inserts on the body of the talus just anterior to the articular facet. It is usually 1.5 to 2 cm long and spans the anterior aspect of the ankle joint. It is confluent with the anterior lateral capsule. The CFL arises just distal to the origin of the ATFL; it does not arise from the tip of the fibula. The ligament runs posterior, medial, and inferior to its origin to insert on the calcaneus. It becomes confluent with the peroneal tendon sheath near its insertion. The PTFL arises from the posteromedial aspect of the lateral malleolus and runs medially to insert on the posterior aspect of the talus. The insertion is broad and involves almost the entire lip of the talus. The PTFL, like the ATFL, is confluent with the joint capsule.¹^,¹²

The borders of the lateral gutter include the fibula laterally, the talus medially, and the tibia with the anterior and posterior tibiofibular ligaments superiorly. The anteroinferior portion of the lateral gutter is bordered by the ATFL, the CFL, and the anteroinferior tibiofibular ligament (AITFL). Posteriorly, the gutter is bordered by the PTFL, the CFL, and the posterior tibiofibular ligament.

The classic sequence of ligament tears during a lateral ankle sprain begins with tearing of the ATFL. It proceeds to the CFL and AITFL, and the last ligament damaged is the PTFL. The ATFL is more vertically oriented and placed under tension with the ankle plantar flexed, making the ATFL function as a collateral ligament in this position. The CFL is more vertically oriented with the ankle in dorsiflexion, making the CFL a collateral in this position. The ATFL therefore resists inversion with the ankle plantar flexed, and the CFL resists inversion with the ankle dorsiflexed. The PTFL inserts on the lateral aspect of the posterior process of the talus and is injured only in the most severe lateral ligament injuries.

There are three sites of impingement in anterolateral ankle impingement.¹ The first involves the ATFL and the area of the lateral gutter and lateral talar dome. The second involves the inferior fascicle of the AITFL, known as Bassett’s ligament. The third is the superior portion of the AITFL.

The anterolateral impingement process begins with an inversion sprain, which tears the ATFL and AITFL, with occasional injury to the CFL. The injury is not severe enough to cause chronic instability. Repetitive motion leads to incomplete healing and inflammation in the areas of the healing ligaments, which leads to synovitis and formation of scar tissue. As the synovium and scar tissue increase in size, the mass may become impinged on by the tibia, fibula, and talus, leading to further irritation and pain. This mechanism can increase inflammation and result in chronic lateral ankle pain.

PATIENT EVALUATION

History and Physical Examination

Patients with anterolateral impingement typically present with a history of multiple ankle sprains followed by chronic, persistent ankle pain, especially with ambulation. Other complaints include ankle weakness and a feeling of the ankle giving way. It is not uncommon to have persistent catching and swelling in the anterolateral aspect of the ankle. Pain often is vague and poorly localized. It may involve the sinus tarsi and the syndesmotic region, depending on the location of the impingement. Pain is usually absent at rest and commences with weight bearing.¹³^,¹⁴

Physical examination begins with observing the patient walk into the room. Because of marked inflammation and pain, the patient may have an antalgic gait. Inspection of the ankle frequently reveals swelling in the anterolateral aspect of the ankle and the lateral gutter. Palpation may elicit pain along the ATFL, along the lateral gutter, and occasionally along the CFL and the syndesmosis (Fig. 6-3). Pain over the ATFL and syndesmosis increases with dorsiflexion of the ankle during palpation. Tenderness depends on the location of the impingement. Determining the origin of the pain is important. Range of motion is typically normal with plantar flexion, but dorsiflexion may be limited because of the impingement. Excessive foot pronation, pes planus, and posterior tibial tendonitis can aggravate the condition. Patients usually do not have increased laxity with anterior drawer or varus stress testing. The examiner must be careful in differentiating pain in the anterolateral gutter from pain in the sinus tarsi. If injection of local anesthetic into the sinus tarsi eliminates the pain, the diagnosis is not anterolateral impingement.¹^,¹³^,¹⁴

FIGURE 6-3 A, Palpation over the syndesmosis, lateral gutter, and anterior talofibular ligament. B, Dorsiflexion of the ankle may increase pain.

Diagnostic Imaging

Imaging modalities include radiography, tomography, computed tomography (CT), and magnetic resonance imaging (MRI). Radiographs are typically negative. They show absence of fractures, no widening of the ankle mortise, and no significant degenerative changes. Anterior tibial osteophytes and a shallow talar neck may be present. Stress radiographs are negative because no instability is present.

Tomography and CT findings are typically negative. Hauger and colleagues ¹⁵ performed CT arthrography for patients with symptoms of anterolateral impingement. The investigators concluded that CT arthrography was a valid test if there was a nodular formation in the lateral gutter or if there was an irregular appearance of the edges of the lateral gutter. These findings corresponded to a meniscoid lesion or an abundant fibrous reaction on arthroscopy. These findings were also statistically associated with a chondropathy.

MRI has a sensitivity of 83.3%, a specificity of 78.6%, and a diagnostic accuracy of 78.8%.¹ Sagittal, T1-weighted and short tau inversion recovery (STIR) images can delineate edema or a soft tissue mass that has caused displacement of the subcutaneous fat normally found immediately adjacent to the lateral gutter. Rubin and coworkers¹⁶ described the use of T2-weighted and fast-spin or STIR images in at least two orthogonal planes to study soft tissue anterolateral impingement. They found that accurate assessment of the anterolateral gutter could be made only when fluid was distending the compartment. They also found that if the ATFL was not visualized, they could not differentiate whether the offending soft tissue was synovial tissue or the ligament. In such cases, they recommended physical examination and stress radiographs to help determine the cause of the impingement. They concluded that an MRI finding of an abnormal soft tissue mass in the lateral gutter distinct from the ATFL suggested the diagnosis of soft tissue impingement. Huh and associates¹⁷ showed that contrast-enhanced, three-dimensional, fast-gradient recalled acquisition in steady state with radiofrequency spoiling MRI revealed high specificity of soft tissue impingement evaluation in patients with chronic post-traumatic ankle pain. Kinematic MRI has also been used to evaluate soft tissue impingement with some success.

TREATMENT

Indications and Contraindications

Failure of conservative treatment, including a short period of immobilization, progressive weight bearing, physical therapy, nonsteroidal anti-inflammatory medications, and selective injections for 3 to 6 months, is an indication for arthroscopic evaluation and treatment. Contraindications are limited and include functional instability and complex regional pain syndrome.¹

Conservative Management

Initial treatment should include a period of at least 3 months of conservative care. Initial treatment methods are varied and include a period of immobilization. This may be a period of absolute immobilization in a cast or relative immobilization in a boot. Progressive weight bearing after immobilization is a good idea, especially if there was a recent ankle sprain. Beneficial physical therapy includes Achilles tendon stretching and anterior tibial and peroneal tendon strengthening. Ankle stabilization bracing or taping during athletic activities may alleviate some pain. Nonsteroidal anti-inflammatory medications for a short period may decrease some of the inflammation. Local steroid injections can help to decrease inflammation. Selective anesthetic injections may help differentiate anterolateral impingement from other diagnoses, such as sinus tarsi syndrome.¹^,¹³^,¹⁴

Arthroscopic Technique

Ankle arthroscopy can be performed using a 1.9-mm, 2.7-mm, or 4.0-mm arthroscope. The 2.7-mm arthroscope is helpful for smaller joints and tight spaces and for subtalar joint arthroscopy. It is somewhat delicate, and for normal ankle arthroscopy, we prefer the 4.0-mm arthroscope because it is sturdier, provides an excellent picture, and allows inflow on the arthroscope. The 30-degree, 4.0-mm arthroscope is our first choice for ankle procedures, but the 2.7-mm arthroscope should be available, particularly for posterior viewing and for tight joints. Most companies manufacture sets of small joint instruments for the elbow and ankle.

Curettes, picks, and elevators of appropriate size for ankle instrumentation should be available. Many small shavers can be used for soft tissue and bone to facilitate access to the ankle joint to remove pathologic tissue. Monopolar or bipolar, 2.0-mm radiofrequency probes are also helpful.

Ankle distraction has evolved considerably from the time when invasive distraction was always used. For arthroscopic procedures, particularly in the anterior compartment, several commercial products are available that enable soft tissue distraction. Noninvasive distraction can be gravity distraction or manual distraction, in which the operating surgeon uses a strap around the ankle to open the joint (Fig. 6-4). We prefer a Velcro strap to a metallic distractor because it allows easier on and off positioning and greater control of the amount of tension applied.

FIGURE 6-4 Noninvasive distraction. A strap around the ankle is attached to a bar off the end of the operating table. The surgeon can pull the bar distally to increase or decrease distraction.

Invasive distraction involves placing pins in the tibia and talus or calcaneus to distract the ankle joint. Contraindications to invasive distraction are open physes, use in athletes who plan to return to their sport quickly, and complex regional pain syndrome. Invasive distraction has been associated with complications, including stress fracture, infection, and neurovascular injury. The use of small joint arthroscopes along with noninvasive distraction techniques has obviated invasive distraction for ankle arthroscopy in most situations. Noninvasive distraction can be used in most any patient as long as there are no skin problems with the application of the harness.

Arthroscopy of the ankle is usually performed with the patient in the supine position and the knee level or flexed. The lateral decubitus position with the patient supported on a beanbag or the prone position can be used for subtalar and hindfoot arthroscopy. We use a special thigh holder that is located inferior to the thigh tourniquet to elevate the leg and avoid pressure to the popliteal area (Fig. 6-5). The holder should be well padded to avoid neurovascular injury. The hip is flexed 40 to 90 degrees. The entire table is raised, and the head is elevated so the foot of the table can be lowered. This position allows the surgeon to stand or sit. It also provides posterior access to the ankle.

FIGURE 6-5 A well-padded thigh holder is used to elevate the leg, and the foot of the table can be lowered for distraction.

Ankle arthroscopy is usually performed through the anterolateral and the anteromedial portals (Table 6-1). Use of a central portal has been discontinued because of the potential for neurovascular injury.

TABLE 6-1 Portal Anatomy

Portal Site	Landmarks	Structures at Risk
Anteromedial	Medial to anterior tibialis tendon	Saphenous vein and nerve Anterior tibialis tendon Extensor hallucis longus tendon

Anterolateral Lateral to peroneus tertius tendon

Superficial peroneal nerve

Extensor digitorum communis tendon

Peroneus tertius tendon

After the patient is prepared and draped, anatomic landmarks are outlined on the skin. These landmarks include the medial malleolus, lateral malleolus, distal tibia, and talus. The procedure can be performed with or without a tourniquet; however, we prefer application of a tourniquet and exsanguination. Using an 18-gauge needle, 30 mL of normal saline is injected through the medial portal to distend the joint. An incision is made through the skin, and using the nick and spread technique to protect the cutaneous nerve, a hemostat is used to create the portal. Next, we introduce the blunt cannula and observe for extravasation of fluid to ensure entry into the joint. The arthroscope is then introduced to visualize the joint.

The anterolateral portal is then established using an outside-in technique. An 18-gauge needle is used for correct localization of the portal. The skin is incised horizontally, it is spread with a hemostat, and a cannula and trocar are inserted.

The examination portion of the procedure begins in the lateral aspect of the ankle and includes visualization of the tibiotalar articulation and soft tissue in that area, the AITFL, the ATFL, and the inferior aspect of the fibula. The inferior fibular space should be inspected, particularly if preoperative symptoms include lateral ankle pain.

With proper distraction, the arthroscope can swing across the midportion of the joint. There is a sulcus between the tibia and talus that allows the arthroscope to be pushed posteriorly. From this position, the operator should be able to see the posterior capsule. The arthroscope is then moved to the medial portal, allowing the surgeon to look down the medial gutter. If after diag nostic examination of the joint the diagnosis of soft tissue impingement is made, the arthroscope is placed medially, and a motorized shaver is brought into the lateral portal. The soft tissue entrapped between the tibia and talus that can be seen with forced dorsiflexion is then removed. Care is taken to visualize the AITFL. If the ligament is thought to be causing part of the impingement or it is partly frayed, a portion of it can be removed with the shaver or the radiofrequency probe (Fig. 6-6).

FIGURE 6-6 A, A shaver is used to clear meniscoid-type tissue from the joint. B, After the trapped tissue has been removed, the ankle should be flexed and extended to check joint motion.

After decompression of the lateral compartment is complete, the arthroscope is placed laterally, and all soft tissue is removed from the medial compartment. The ankle joint is flexed and extended to ensure that all trapped tissue has been removed. If spurs are seen on the tibia or talus, they are removed at this time. Care must be taken with the shaver to avoid cutting anterior to the capsule, where the neurovascular structures lie. With proper distraction and fluid distention, arthroscopic removal of soft tissue is a very safe procedure. The radiofrequency probe is used to cauterize any residual bleeding, and the arthroscope is removed.

We prefer to close the portals postoperatively to prevent excess fluid leakage that can cross-contaminate and cause infection. We inject the joint with bupivacaine for postoperative pain relief, and a bulky wrap is applied. The tourniquet is then deflated.

The patient usually returns home the same day. He or she does not bear weight until the office visit in 4 to 5 days for evaluation and suture removal.

When soft tissue impingement is caused by mild ankle instability, ankle reconstruction is seldom indicated. However, if the ankle impingement is related to a chronically unstable ankle, we often perform arthroscopy before completing a modified Broström reconstruction procedure.

PEARLS& PITFALLS

• If the ankle joint space is tight in a smaller individual, a smaller arthroscope may be helpful.

• When using distraction, be sure there is ample room behind the ankle to allow for a posterior portal if needed.

• The nick and spread technique should be used for all incisions to avoid sensory nerve problems.

• Always use cannulas without side portals to prevent extravasation of fluid.

• Use the outside-in technique for establishing the operative portal to avoid scuffing articular cartilage.

• A monopolar or bipolar radiofrequency probe for tissue resection is helpful in limited space.

• After the diagnosis has been made, temporarily release the traction and flex and extend the ankle to detect soft tissue entrapment. Although most entrapment is in the lateral joint, both sides of the joint should be decompressed.

• Always close the portals to prevent oozing and possible secondary contamination.

• Rehabilitation must include exercises to restore proprioception to the ankle.

Postoperative Rehabilitation Protocol

Sutures are removed at 4 to 5 days after surgery.¹⁴ At that time, the patient is allowed to start active assisted range-of-motion exercises, strengthening, and touch-down weight bearing. Patients progress to partial and full weight bearing as motion and strength return.

Because soft tissue impingement is the most often the result of ankle sprain, a physical therapy program designed to strengthen and restore proprioception is continued until full strength and mobility are achieved.