Impingement syndromes of the ankle

                 Impingement syndromes of the ankle

                                         DR KS DHILLON

Introduction

A painful mechanical limitation of ankle movements caused by an osseous or soft-tissue abnormality is known as ankle impingement. Patients often present with chronic ankle pain of varying etiology. Ankle impingement syndrome, though rare, is one of the cause of chronic ankle pain [1]. 
There is no official classification for ankle impingement syndromes. The syndromes are described, depending on their location, as anterior, anterolateral, anteromedial, posterior, posteromedial, hindfoot extra-articular, and syndesmotic impingements [2].

Anterior ankle impingement

Anterior ankle impingement is usually seen in athletes such as football and soccer players, ballet dancers, gymnasts, and runners who are involved in activities that require repetitive ankle dorsiflexion.

Osseous anterior bony impingement occurs from osteophyte impingement of the anterior rim of the tibia and the talar sulcus. Repetitive forces are believed to lead to impaction-related microtrauma of the anterior chondral margin of the tibiotalar joint which over time leads to osteophyte formation from attempted repair with fibrosis and fibrocartilage proliferation [3]. The contact between opposing bone or the entrapment of soft tissues between the bones may produce pain. These osteophytes are located inside the joint and away from the capsular attachment.

Others believe that repetitive traction injury to the anterior joint capsule due to hyper plantar flexion leads to the formation of these osteophytes [4,5].

Although the anterior tibiotalar osteophytes are often referred to as “kissing osteophytes”, they do not actually overlap and abut. CT scan studies show that talar spurs usually lie medial to the midline of the talar dome and tibial spurs are usually located lateral to the midline [6]. There is a trough in the articular talar dome which usually “accepts” the tibial osteophyte during ankle dorsiflexion. Some refer to it as a “tram-track lesion” [7], and others refer to it as a “divot sign” [8]. Other studies have shown a high rate of  talar cartilage lesions (80.7 %) which correspond to the distal tibial osteophytes and also the presences of multiple loose bodies in these patients [9].

There is a triangular soft tissue mass which is composed of adipose and synovial tissues in the joint space in front of the ankle joint. This soft tissue mass can be compressed when dorsiflexion of the ankle exceeds 15° [10].

The presence of anterior osteophytes may further limit the space available for this soft tissue mass and cause entrapment, leading to chronic inflammation and synovitis[2]. Some of the other causes of anterior ankle pain include post-traumatic fibrous bands [11], thickened anterior tibiofibular ligaments [12,13], and synovial plica [14]. Although various types of lesions have been described, their exact etiology is not well understood.

Asymptomatic anterior tibiotalar spurs on lateral view x rays of the ankle may be present in 45% to 59% of professional athletes[15].

The clinical symptoms of anterior ankle impingement include pain and a subjective feeling of blocking on dorsiflexion. On examination, the dorsiflexion movements are painful and limited and occasionally a soft tissue swelling may be palpable [16]. The symptoms are usually due to degeneration of the joint rather than the spurs.

Usually plain x rays of the ankle are sufficient to detect the spurs. MRI of the ankle may show synovitis, effusion and bone marrow edema. However MRI is usually not necessary for anterior ankle impingement.

The mainstay of treatment is conservative with NSAIDs and rehabilitative  physiotherapy(16-18), but in resistant cases surgery appears to show  long-term benefit (16). Usually arthroscopic debridement of the spurs and soft tissues with a washout is carried out [16]. The prognosis depends on the severity of the degeneration of the joint [16]. A hundred percent to 77% excellent function after surgery at 6.5 years has been reported [16]. The evidence however remains weak.

Anterolateral Impingement

The anterolateral recess of the ankle is formed by the tibia posteromedially and the fibula laterally. Anteriorly and laterally lies the tibiotalar joint capsule, the anterior tibiofibular, anterior talofibular and the calcaneofibular ligaments.

Supination injuries, recurrent lateral ligament sprains and chronic lateral ligament instability can predispose a patient to anterolateral soft tissue impingement of the ankle. Chronic inflammation and hypertrophic changes of the synovial tissue occurs between the talus and the tibia [19]. Thickened synovial and scar tissue get entrapped in the anterolateral gutter  leading to pain and swelling after activity as well as limitation of ankle dorsiflexion and supination [20,21].

Rarely hypertrophy of the inferior portion of the anterior tibiofibular ligament and occasionally osseous spurs can cause anterolateral impingement [22,23].

Symptoms of anterolateral impingement include focal anterolateral pain
which is aggravated by supination or pronation of the foot. Examination usually shows anterolateral tenderness, swelling, pain on single-leg squatting, and pain on ankle dorsiflexion and eversion [22,23].
X rays of the ankle are usually of not much value in the diagnosis of anterolateral impingement. The role of MRI in the diagnosis is also controversial. MR arthrography has been able to detect abnormalities such irregular or nodular contour of the anterolateral soft tissues which correlated with anterolateral scarring or synovitis in the anterolateral recess of the ankle. However such finding are also seen in asymptomatic individuals [24]. Chondral defects, spurs, and laxity or rupture of the anterior talofibular ligament may also be seen in patients with anterolateral impingement.

Rehabilitative physiotherapy and NSAIDs usually relieve symptoms in most patients. Those who do not respond to conservative treatment are often treated with arthroscopic debridement of the joint. The published reports on the outcome of arthroscopic surgery for treatment of anterolateral impingement are level 4 retrospective studies[25 ] or involve small numbers of cases [26,27].

Anteromedial Impingement

The exact cause of anteromedial impingement is not know but it is believed to be caused by inversion or eversion injury leading to tearing of the anteromedial capsule and the tibiotalar ligament. Repeated microtrauma leads to synovitis and capsular thickening. Bony injury and cartilage damage may lead to spur formation with synovial and capsular thickening [1].

The clinical features include chronic anteromedial pain which is aggravated by ankle dorsiflexion. Examination shows anteromedial tenderness and limitation of ankle dorsiflexion and foot inversion [28,29].

MR arthrographic would show focal capsular and synovial thickening in
tibiotalar joint anterior to the tibiotalar ligament [29]. Bone spurs with anteromedial synovitis may also be seen.

There are no studies which document the effectiveness of conservative treatment in the treatment of anteromedial impingement syndrome. Neither has the outcome of steroid injections been well studied. Some authors recommend surgery (arthroscopic debridement) as the first line of treatment. Level 4 evidence (case series) shows excellent functional outcomes at a minimum of 2 years follow up [30].

Posterior Impingement

Posterior impingement is also known as the os trigonum syndrome and posterior tibiotalar compression syndrome [31]. Posterior impingement results from compression of soft tissues between posterior process of the calcaneus and the posterior tibia on plantar flexion of the ankle. The posterior talus contributes significantly to posterior impingement due to the presences of os trigonum or Stieda’s process in some patients.

Besides bony structures at the back of the ankle there are several ligamentous structures at the back of the ankle which include, the posteroinferior talofibular ligament, the transverse tibiofibular ligament, the tibial slip or the posterior intermalleolar ligament, and the posterior talofibular ligament [32].
Patients with posterior impingement syndrome usually present with pain at the back of the ankle on activities which involve extreme plantar flexion such as soccer, football, ballet and running downhill [31].

An acute plantar hyperflexion injury and chronic repetitive microtrauma are believed to lead to posterior impingement syndrome. Hypertrophy of the posterior tissue with compression leads to chronic pain at the back of the ankle. There may be damage to regional ligaments and tendon. Flexor hallucis tenosynovitis is often present in many patients [33].

Presence of a Stieda's process or an os trigonum is not diagnostic of impingement because these bony abnormalities are also present in asymptomatic individuals. A MRI can be useful in detecting bone marrow oedema within the talus, calcaneus or an os trigonum. It will also show synovitis and thickening of the posterior ligaments [32].

The first line of treatment is conservative, as with other impingement syndromes, and surgery can be carried out if conservative treatment fails. Surgery consists of arthroscopic debridement.

Posteromedial impingement 

The posteromedial joint space is bound by the medial malleolus and posterior tibiotalar ligament (PTTL) anteriorly and talar dome and posterior process of the talus laterally. Posteriorly it is bound by the posteromedial joint capsule, neurovascular bundle and flexor hallucis longus tendon.
The precipitating injury usually is plantar flexion, inversion and internal rotation trauma which leads to PTTL damage and synovitis ensues affecting the tibialis posterior, flexor hallucis longus and/or the flexor digitorum longus tendons [34].

It is one of the least common ankle impingement syndromes. Patients usually present with pain over the posteromedial aspect of the ankle with movements of the ankle.

Plain radiographs are of not much value in diagnosis of posteromedial impingement. A MRI would show abnormal pathology in the PTTL consisting of thickening and loss of the normal fibrillar pattern. Fluid collection, synovitis and irregular soft tissue may be seen in the posteromedial recess [35].
Treatment is usually conservatively, but surgical treatment may be contemplated in patients not responding to conservative treatment.

Extra-articular lateral hindfoot impingement syndrome (ELHIS)

The extra-articular lateral hindfoot impingement syndrome is not caused by trauma but results from a pathological tibialis posterior tendon which produces a flatfoot and hindfoot valgus deformity [36]. Commonly  impingement is seen between the lateral talus and calcaneus (talocalcaneal impingement) and also between the calcaneus and fibula (subfibular impingement) [36].

 Accessory anterolateral talar facet is also known to cause ELHIS. The accessory anterolateral facet can cause pathological impingement of the neck of the calcaneus in patient with flatfoot/hindfoot valgus deformity [37].

Repeated talocalcaneal and fibulocalcaneal impingement will lead to arthrosis at the contact points. Patients usually present with pain in the region of the sinus tarsi. Conventional radiography is useful in the diagnosis. Oblique x rays and valgus stress views are useful. Coronal oblique CT scans will also show the site of impingement. An MRI is useful for evaluating the degree of tibialis posterior tendon pathology. The MRI will also show cystic changes and bone marrow oedema within the lateral talus in addition to soft-tissue thickening between the fibula and the calcaneus and also show fibula tip oedema [36].

Initially treatment includes physical therapy, a period of immobilization, orthotics, and non-steroidal anti-inflammatory medications. In the event of failure of conservative treatment surgical intervention with preservation of the subtalar joint is carried out. Resection of the accessory anterolateral talar facet is carried out with correction of the hindfoot deformity. In patients with advanced arthritis subtalar arthrodesis is carried out [37].

Conclusion

Ankle impingement syndromes are an uncommon cause of chronic ankle pain. There is no classification for ankle impingement syndromes but they are named according to the location of the impingement around the ankle both anterior and posterior to the ankle. There are soft tissue and bony abnormalities involved in the pathology of impingement syndromes.
Symptoms with anterior impingement occur with terminal dorsiflexion and with posterior impingement on hyper plantar flexion.
The mainstay of diagnosis is history and physical examination. Imaging helps to confirm the diagnosis in most cases. Initially treatment is conservative, failing which open or arthroscopic surgery is carried out for treatment of impingement syndromes.
Although most authors claim good to excellent outcomes with arthroscopic surgery, the level of evidence however is low (level 4). Currently there is a lack of good quality outcome studies (level 1) in the literature for the treatment of impingement syndromes of the ankle.

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