Soft Tissue Lesions of the Ankle



Soft Tissue Lesions of the Ankle


CHAD S. CONNER

RICHARD D. FERKEL



Soft tissue lesions of the ankle present a difficult diagnostic problem. Even after careful history, physical examination, and diagnostic testing, the diagnosis may not be readily apparent. These lesions usually involve the synovium, but the capsule or ligamentous tissues may also be affected. Soft tissue pathology accounts for about 30% to 50% of lesions seen in the ankle and subtalar joints.

In the past, acute and chronic soft tissue complaints in the ankle have been treated primarily by nonoperative means, with a specific diagnosis often lacking. If the patient’s symptoms persisted, aspiration and occasionally arthrotomy with synovial biopsy were done. Arthroscopy has allowed the entire visualization of the joint without obscuring tissue planes (unlike an arthrotomy). It allows complete diagnosis and treatment of soft tissue problems.


ANATOMY AND HISTOLOGY

Nearly all articulations of the extremities are synovial or diarthrodial joints. Because they have a joint cavity, they are fairly movable. Anatomic features of the synovial joint are shown in Figure 8-1. The articular cartilage and the articulation are enveloped by a joint capsule and supported by ligaments. The outer stratum of the joint capsule (fibrosum) is made up of dense fibrous tissue. The inner layer (synoviale) consists of loose, highly vascular connective tissue and synovium (synovial membrane).1 This synovial membrane is usually smooth and glistening and may exhibit infoldings (synovial folds) and slender projections, the larger ones called synovial villae. It is richly supplied with nerves, lymphatics, and blood vessels.






FIGURE 8-1. Cross-sectional view of a typical synovial joint of the ankle. (Illustration by Susan Brust.)

There are two types of membrane or synovial cells, type A and type B. Type B cells are the producers of hyaluronic acid of the synovial fluid.2

The joint cavity contains a viscous fluid, the synovial fluid, produced by the synovial membrane. Analysis of this fluid is helpful in the differential diagnosis of joint swelling because it can distinguish noninflammatory, inflammatory, and septic processes.3


CLASSIFICATION

Numerous classifications of synovial disorders can be made. The system presented below incorporates the source of synovial irritation and will be used throughout this chapter:


1. Congenital: plicae or congenital bands within the ankle

2. Traumatic: sprains, fractures, and previous surgery

3. Rheumatic: rheumatoid arthritis, pigmented villonodular synovitis, crystal synovitis, hemophilia, von Willebrand disease, and synovial chondromatosis

4. Infectious: bacterial and fungal

5. Degenerative: primary and secondary

6. Neuropathic: Charcot joint

7. Miscellaneous: ganglions and arthrofibrosis.



PATIENT EVALUATION

Patients with complaints of aching, swelling, tenderness, and other signs of joint inflammation should always be carefully evaluated to determine the specific causes of their symptoms. A detailed differential diagnosis must be considered and include the above problems or others as discussed later. A history of trauma or injury is more likely to cause a nonspecific type of synovitis, either localized or generalized; however, trauma can also trigger an underlying specific pathologic process.

Patient evaluation includes a careful history, physical examination, and radiologic testing. Arthritis tests should be used throughout for rheumatoid arthritis, lupus, gout, and other rheumatologic conditions whenever suspicion is present. CT scanning is helpful for three-dimensional imaging of the ankle, especially with bony and soft tissue lesions.4 MRI is particularly helpful in demonstrating soft tissue lesions about the foot and ankle: it allows the observer to distinguish blood vessels, nerves, fat, ligaments, tendons, bone marrow, muscles, and fluid clearly, as each has different signal characteristics.5 A detailed discussion of radiologic techniques is given in Chapter 2. An algorithm is useful to help evaluate and treat chronic sprain pain patients as seen in Table 8-1.








TABLE 8-1. Management of Chronic Ankle Pain





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CONGENITAL PLICAE

Plicae, or shelves, have been clearly demonstrated in the knee but are more difficult to find in the ankle. More commonly, congenital bands are seen as an incidental finding when examining the ankle for other types of pathology.


TRAUMA


Nonspecific Generalized Synovitis

This type of synovitis can be caused by sprains or after fractures or previous surgery. The ankle joint can respond to both indirect and direct trauma. With a traumatic episode, a generalized or localized synovitis can occur, as well as fibrous bands and adhesion formation. Patients with
generalized nonspecific synovitis usually complain of pain, swelling, and soreness, and their history may involve a traumatic event, either significant or trivial. Occasionally, no inciting event can be recalled. If, after adequate and appropriate workup, the patient fails to respond to conservative treatment, ankle arthroscopy is indicated.






FIGURE 8-2. Arthroscopic view of a fibrous band traversing the anterior lateral ankle in a 25-year-old patient. Excision of this band relieved his pain.

At surgery, chronically inflamed synovium is commonly seen and may contain hemosiderin or other fibrin debris. With synovitis, the villae produce a fibrin exudate. The formation of fibrous bands represents aggregates of the fibrin exudate. These are usually seen anteriorly but can also be seen in the syndesmosis or posteriorly. They are associated with minimal to mild chondromalacia, depending on the duration of the symptoms (Fig. 8-2).

The most common causes of nonspecific synovitis are ankle sprains and fractures. After such injuries, the hematoma produces exudate and swelling, followed by extensive cellular response, fibrous tissue reaction, hyalinization, and ultimately chronic synovitis. Significant synovitis, adhesive band formation, and scarring and fibrosis can be seen with severe injury and are usually associated with arthrofibrosis of the joint.

Van Dijk et al. reported on ankle arthroscopy results following fracture in 34 patients. They separated the patients into two groups based on whether a preoperative diagnosis was made of anterior bony or soft tissue impingement or whether the ankle arthroscopy was considered diagnostic for more diffuse symptoms. They found at 2 years follow-up, 76% of the impingement patients had a good or excellent result as opposed to 43% of the diagnostic arthroscopy patients. Of the impingement patients, 17/18 had removal of bony spurs and 14/18 had a partial synovectomy and removal of impingement lesions anteromedially (10) and anterolaterally (4). In the diagnostic group, 7 patients had removal of scar tissue and partial synovectomy with the others having debridement of cartilage (4) and removal of osteophytes (5). The diagnostic group did include 3 patients with grade III osteoarthritis. It appears that more consistent good to excellent results may be appreciated with a diagnosis prior to arthroscopy in postfracture patients.6 This problem is discussed further in Chapter 11.


Nonspecific Localized Synovitis

A localized synovitis of the medial, lateral, or anterior talomalleolar joint can develop after trauma and produces localized soreness and swelling. On physical examination, localized tenderness with minimal swelling and full range of motion is usually seen. The diagnostic workup is usually negative, although there may be some signal alteration on MRI. At arthroscopy, mild synovitis, papillary formation, and fibrosis are noted. Excision of this tissue in a localized area often produces excellent results if all conservative treatment methods have failed (Fig. 8-3).


Soft Tissue Impingement

Ankle sprains are one of the most common injuries in sports with one inversion ankle sprain occurring per 10,000 persons per day.7, 8, 9 Gerber et al. in a prospective study at West Point showed that ankle sprains represented 23% of all injuries seen in cadets,10 and another study showed ankle sprains as representing 40% of all athletic injuries.11 In the study at West Point, 55% of cadets had symptoms 6 weeks after an ankle sprain. At 6 months, all returned to full activity, but 40% still had symptoms.10 Other studies have shown that 10% to 50% of patients have some chronic pain following an ankle sprain.12, 13, 14 Commonly, ankle inversion injuries are associated with the following sequence: torn anterior talofibular ligament, torn calcaneofibular ligament, and torn posterior talofibular ligament. During this sequence, the syndesmotic ligaments, anteriorly, posteriorly, or both, can also be injured (Fig. 8-4).






FIGURE 8-3. Arthroscopic view of local synovitis of the anterior ankle joint in a 51-year-old male with chronic ankle pain.







FIGURE 8-4. Plantar flexion inversion injury of the right ankle leading to single and multiple tears of the lateral ligamentous complex. (Illustration by John Daugherty.)

The differential diagnosis of patients with a history of an ankle sprain with resultant chronic ankle pain may include chronic instability, osteochondral lesions, calcific ossicles beneath the malleoli, tarsal coalition, subtalar joint dysfunction, peroneal tendon tear or subluxation/dislocation, degenerative joint disease, occult fractures of the talus and calcaneus, nerve entrapment, reflex sympathetic dystrophy, and soft tissue impingement.15

The primary cause of chronic pain after an ankle sprain is soft tissue impingement. This can occur along the syndesmosis, the anterior gutter, the syndesmotic interval between the tibia and fibula, underneath the ankle, or posteriorly in the syndesmosis and posterior gutter. One recent study showed in 72 patients with residual ankle pain following a sprain an incidence of fibrous band impingement of 4% but 100% had significant synovitis.16


Anterolateral Impingement

Anterior impingement of the ankle is the most common type of soft tissue impingement because of the mechanism of most ankle sprains. At the Southern California Orthopedic Institute between 1983 and 1989, ˜2,000 patients were managed for an ankle sprain, and of those, 43 patients (2%) were diagnosed with anterolateral impingement syndrome and treated with arthroscopy.15 Deberardino et al. reported an incidence of 1.2% after review of 5,000 ankle sprains.17

Wolin and colleagues in 1950 first described 9 patients with persistent pain and swelling over the anterolateral aspect of the ankle several weeks to months after an inversion sprain.18 Arthrotomy of the ankle in these patients revealed a massive hyalinized connective tissue extending into the joint from the anterior inferior portion of the talofibular ligament. They called this a “meniscoid” lesion because it looked like a torn meniscus in the knee. They thought that disability resulted from entrapment of this tissue between the talus and the fibula; excision of the scar tissue relieved the symptoms in all cases. Waller described and termed the pathological process as “anterolateral corner compression syndrome” in 1982. This was thought to be a result of a single or repetitive ankle inversion injury.19

In a series of 31 patients followed at the Southern California Orthopedic Institute, all patients had experienced a previous ankle sprain. Six reported multiple previous sprains and 5 had had previous ankle surgery. This is similar to other studies.17, 20, 21, 22, 23 It is thought that in an inversion sprain, tears in the anterior talofibular ligament +/- the calcaneofibular ligament occur but without leading to residual instability. Then, through repetitive motion, the torn ligament becomes inflamed with resulting synovitis and scar tissue. As the tissue thickens and hypertrophies, anterolateral impingement ensues further inciting inflammation and pain to the surrounding fibula, tibia, and talus.15, 24 A proposed sequence for the development of chronic impingement of the ankle is described in Table 8-2.

Guhl had theorized that a minimal sprain may cause an intra-articular hematoma that is slowly absorbed by the lateral synovium, which leads to a reactive synovitis.25 Lahm postulated that because some of the resected meniscoid lesions that were removed were covered in synovium and the lesions may be a result of trauma to a pre-existing plical band.26.








TABLE 8-2. Sequence of Lateral Ankle Pain





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ANATOMY

A thorough understanding of the region’s anatomy is necessary. Impingement can occur at the anterior inferior tibiofibular ligament, the lateral gutter, the anterior talofibular ligament, and the anterior tibiotalar ligament (Fig. 8-5A-C). The anterior inferior tibiofibular ligament (AITFL) measures an average length of 23 mm and originates on the distal lateral tibia and then inserts on the anterior aspect of the fibula.27 The anterior talofibular ligament (ATFL) originates on the anterior aspect of the inferior oblique segment of the distal fibula (˜20 mm from the anterior tubercle of the fibula) and then inserts on the body of the talus anterior to the fibular articulating cartilage.28 Additionally, Keller et al. further described the anterior tibiotalar ligament, which originates just anterior to the tibial origin of the AITFL on
the anterolateral tibial plafond with often (58%) having fibers concurrently attached to the anterior fibula between the insertion of the AITFL and origin of the ATFL. The ligament then courses laterally and inferior (˜26 mm) to insert just medial to the insertion of the ATFL27 (Fig. 8-5D and E).






FIGURE 8-5. Anterolateral ankle anatomy. (A) Soft tissue impingement sites. Note the accessory fascicle of the anterior inferior tibiofibular ligament, which can impinge across the lateral talar dome. (B) Plane of cross-section through the lateral gutter. (C) Cross-sectional picture of lateral gutter. This gutter is bounded by the talus medially, the fibula laterally, and the anterior and posterior ligaments.






FIGURE 8-5. (Continued) (D) and (E) Type I anterior tibiotalar ligament configuration. Its origin is the anterolateral portion of the distal tibia border. The ligament passes the talar trochlea and inserts onto the anterolateral talar neck. It does not attach to the fibula. (Illustrations AD by Susan Brust. E from Keller K, Nasrilari M, Filler T, et al. The anterior tibio-talar ligament: one reason for anterior ankle impingement. Knee Surg Sports Traumatol Arthrosc 2010;18:225-232, with permission.)


CLINICAL PRESENTATION

Because the most common mechanism of ankle injury is plantar flexion inversion, chronic lateral ankle pain is much more common than chronic medial pain following a sprain. Typically, the patient complains of vague anterior pain, usually along the anterior and anterolateral aspect of the ankle, sometimes involving the syndesmosis and sinus tarsi regions. Pain is usually absent at rest and present with most activities, limiting the patient’s ability to participate in a given sport. It may be aggravated by ambulation with sensations of weakness and giving way15 or swelling, popping, or limited ankle motion.20 Often, the patient has seen several physicians and is frustrated by his or her lack of progress.

Physical examination typically reveals significant anterolateral ankle tenderness to palpation with normal or near normal ankle motion. It is not uncommon for patients to also have tenderness along the syndesmosis; anterior gutter, including the anterior talofibular ligament and the calcaneofibular ligament; and many times also the posterior subtalar joint or sinus tarsi. It is important to try to differentiate by selective anesthetic injection lateral gutter pain from subtalar pain, especially in the sinus tarsi. If anterolateral laxity was found, or pain in the subtalar joint was diagnosed, the diagnosis of anterolateral impingement was not made15 (Fig. 8-6).

Radiologic evaluation is done to evaluate for arthritis, osteochondral lesions, or other pathology as mentioned above, and stress radiographs are done to evaluate for instability.15 Radiographs may reveal calcification or heterotopic bone in the interosseous space, which indicates previous injury to the distal tibiofibular syndesmosis, with ossicles along the tip of the fibula and the lateral talar dome consistent with injuries of the anterior talofibular ligament. Often, the x-rays are normal, as are a bone scan and CT scan.

CT scan has been found to be helpful at times for diagnosing the cause of chronic ankle pain following a sprain due to its ability to visualize avulsed intra-articular and juxta-articular fragments that were not seen on the plain radiographs.29 Correlation of MRI findings with arthroscopic findings has been variably reported. Previous MRI studies have shown MRI to have a sensitivity of 39% to 42% and a specificity of 50% to 85% in detecting soft tissue impingement of the ankle.30, 31 Urguden et al. reported a 50% positive correlation of MRI findings with arthroscopic findings.20 With newer MRI techniques at the Southern California Orthopedic Institute, the sensitivity has increased to 83% and the specificity to 79% for diagnosing soft tissue impingement.32 The impingement lesion is
evaluated on the T1 sagittal MRI film at a slice just medial to the peroneal tendons. The impingement tissue will present as a low-intensity signal anterior to the fibula often extending anterior and into the lateral gutter32 (Fig. 8-7).






FIGURE 8-6. Differentiating pain in the lateral gutter from subtalar pain is done by careful palpation of the syndesmosis, lateral gutter, and sinus tarsi. Selective injections can also be helpful in distinguishing the area of maximum pain. (Illustration by Susan Brust.)






FIGURE 8-7. (A) Sagittal T1 MRI revealing a low-intensity signal anterior to the fibula displacing the normal fat just medial to the peroneal tendons indicative of soft tissue impingement. (B) Axial T2-weighted image showing fluid in the lateral gutter with torn remnant of syndesmotic ligament.

Additionally, a “contrast-enhanced, fat-suppressed, three-dimensional (3D), fast-gradient-recalled acquisition in the steady state with radiofrequency-spoiling” MRI sequence has been reported to have a sensitivity of 91.9% and a specificity of 84.4%.33


ARTHROSCOPIC APPEARANCE

At arthroscopy, the medial malleolar-talar articulation and the central portion of the ankle on the anterior gutter are usually normal. Pathology is generally limited to the syndesmosis and the lateral gutter. Patients generally have a synovitis surrounding the anterior inferior tibiofibular ligament, both in front and behind, as well as synovitis of the anterior talofibular ligament.15, 20 The synovitis is generally firmer with a more elastic consistency.15 Also noted at surgery is fibrosis of the lateral gutter and chondromalacia of the talus and the fibula in some cases.15, 20 In addition, a small ossicle or loose body may be hidden in the soft tissues at the tip of the fibula. Occasionally, an adhesive thick scar band, previously described as a meniscoid lesion or inflamed plical band, is present, extending between the anterior and posterior lateral gutter or extending anteriorly (Fig. 8-8).18, 20, 22, 26 Rarely, a synovial shelf may be present as well spanning across the anterior ankle.20




PREFERRED METHOD

The patient is placed in a supine position with a non-sterile thigh holder, and the foot is prepared and draped. Usually, a noninvasive distraction strap can be applied (see Chap. 3). Use of the strap allows complete inspection of the entire joint but still permits easy relaxation of distraction to allow surgery in the anterolateral portion of the ankle. All anatomic landmarks are carefully marked out, and the ankle is distended with 10 mL saline from the anteromedial portal. The anteromedial portal is then established and a 2.7-mm short videoscope with a 2.9-mm interchangeable cannula is inserted. The probe is placed through the anterolateral portal, and inflow is through the posterolateral portal.






FIGURE 8-9. Debridement of the lateral gutter. (A) Debridement is performed with a small joint shaver and includes removing inflamed synovium, thickened adhesive bands, osteophytes, and loose bodies. (B) Arthroscopic view through the anteromedial portal. A full-radius shaver is debriding the lateral gutter while avoiding injury to the anterior talofibular ligament. (Illustration A by Susan Brust.)

Initially, visualization with the 30° arthroscope should be done from the anteromedial, anterolateral, and posterolateral portals. The inflow cannula is then left in the posterolateral portal to give a high-flow system. The arthroscope is reinserted in the anteromedial portal, and the anterolateral gutter is debrided with the 2.9-mm full-radius shaver, baskets, and graspers as necessary. Debridement usually includes removing inflamed synovium, thickened adhesive bands, osteophytes, and loose bodies (Fig. 8-9).
All involved tissue is excised down to the underlying cartilage. The synovium, as well as any inflamed capsular or ligamentous tissue, is removed. Care must be taken not to excise the anterior talofibular ligament remnant. Inflammatory tissue may be seen not only in the lateral gutter but also in the syndesmosis in the articular space between the tibia and fibula.






FIGURE 8-10. The effect of dorsiflexion and plantar flexion of the ankle on the lateral gutter. (A) With plantar flexion, tension is applied across the lateral gutter, narrowing this space and making visualization difficult. (B) Dorsiflexion of the ankle relaxes the lateral gutter structures while the fibula is pulled slightly superiorly, optimizing visualization of this entire area. (Illustration by Susan Brust.)






FIGURE 8-11. Visualization of the lateral gutter of the left ankle from the anteromedial portal. (A) Picture obtained with a 30° arthroscope prior to debridement. It is difficult to see the fibula and the anterior talofibular ligament. (B) Using the 70° arthroscope to look over the lateral dome of the talus, the articulation of the fibula with the talus and the anterior talofibular ligament is well seen postdebridement in the same patient.

Following the work done while viewing with the 30° arthroscope, the distraction is released one click with the distractor and visualization is performed with the 70° arthroscope. With more distraction applied, anterolateral compartment of the ankle becomes more occluded, thereby making visualization difficult in this region. The best way to visualize the anterolateral gutter is to dorsiflex the ankle (with distraction relaxed) so the entire lateral gutter space opens up. With dorsiflexion of the ankle, the anterior capsule is relaxed and the lateral malleolus moves away from the medial malleolus. At the same time, the fibula is pulled slightly superiorly, while the fibers of the interosseous and tibiofibular ligaments tend to become more horizontal. In addition, the fibula is medially rotated with dorsiflexion (Fig. 8-10). The 70° arthroscope allows increased visualization of the syndesmosis, anterolateral gutter, and talus and allows better visualization along the posterior gutter from the anterior portals (Fig. 8-11).




PATHOLOGIC FINDINGS

With biopsy of the impingement lesions studied at the Southern California Orthopedic Institute, moderate synovial hyperplasia with subsynovial capillary proliferation was observed in all specimens with many displaying fibrosis and hyaline cartilage degeneration (Fig. 8-12). These findings were representative of a chronic inflammatory process.15 Further studies have supported the findings of meniscoid lesions having a hyalinized and fibrous stroma.26

In general, ligamentous tissue was not seen on histologic analysis.


Sep 25, 2018 | Posted by in RHEUMATOLOGY | Comments Off on Soft Tissue Lesions of the Ankle
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