Posterior Impingement of the Ankle: “Can There Also Be a Tendinous Entity?”

Fig. 24.1

Transverse section at the level of the tibiofibular syndesmosis showing important structures susceptible to injury during ankle arthroscopy. 1 lateral malleolus, 2 tibia, 3 anterior neurovascular bundle (deep peroneal nerve and anterior tibial artery and veins), 4 intermediate dorsal cutaneous nerve (lateral branch of the superficial peroneal nerve), 5 medial dorsal cutaneous nerve (medial branch of the superficial peroneal nerve), 6 posterior neurovascular bundle (posterior tibial nerve and posterior tibial artery and veins), 7 sural nerve and small saphenous vein, 8 saphenous nerve and great saphenous vein, 9 anterior peroneal artery, 10 posterior peroneal artery, 11 tibialis anterior tendon, 12 extensor hallucis longus tendon, 13 extensor digitorum longus tendon, 14 peroneus tertius muscle belly, 15 peroneus brevis longus, 16 peroneus brevis tendon, 17 tibialis posterior tendon, 18 flexor digitorum longus tendon, 19 flexor hallucis tendon (musculotendinous), 20 calcaneal and plantaris tendons (Drawing courtesy of Pau Golano)

The main anatomical structure for orientation and to determine the safe working area is the flexor hallucis longus tendon (FHL). Just medial to this tendon runs the posterior neurovascular bundle (tibial nerve and posterior tibial artery and veins). Posterior ankle arthroscopy should therefore routinely be performed lateral to the FHL tendon.

Proper positioning of the ankle and the hallux results in better visualization of the tendinous portion of the FHL muscle and avoids unnecessary resection of some of the muscle fibers that reach the lateral tendinous border in a semipeniform morphology. Plantar flexion of the ankle or hallux flexion facilitates visualization of the FHL tendon proximal to the lateral talar process.

The posterior ankle ligaments are also important for orientation during the posterior ankle arthroscopy. These ligaments include the posterior talofibular ligament, the posterior intermalleolar ligament, also called the tibial slip in the arthroscopic literature, and the posterior tibiofibular ligament which is composed of a superficial and deep component or transverse ligament (Fig. 24.2).

Fig. 24.2

Posterior view of the anatomical dissection of something showing the boundaries and principal anatomical details to be recognized during posterior ankle arthroscopy. The neurovascular structures were removed. 1 flexor hallucis longus tendon and muscle belly, 2 lateral talar process, 3 flexor hallucis longus retinaculum, 4 subtalar joint line, 5 superficial component of the posterior tibiofibular ligament, 6 deep component of the posterior tibiofibular ligament or transverse ligament, 7 posterior talofibular ligament, 8 posterior intermalleolar ligament or tibial slip, 9 calcaneofibular ligament, 10 flexor digitorum longus tendon and muscle belly, 11 tibialis posterior tendon covered by the flexor retinaculum, 12 peroneal brevis tendon (cut). 13 peroneal longus tendon, 14 boundaries of the safe anterior working area (Drawing courtesy of Pau Golano)

When the posterior ankle compartment is visualized arthroscopically, the location of the FHL tendon should be determined first. Then the detailed anatomy of the posterior ankle can be identified more carefully.

The posterior talofibular ligament, a component of the lateral collateral ligament, originates from the malleolar fossa, located on the medial surface of the lateral malleolus, coursing almost horizontally to insert in the posterolateral surface of the talus. This ligament is also an important reference in posterior ankle arthroscopy. Its location is important to identify the site of the subtalar and talocrural working areas (Fig. 24.3). The posterior subtalar recess is plantar to this ligament and the talocrural joint is located dorsally [5–10].

Fig. 24.3

Posterior view of the anatomical dissection of ankle ligaments (dorsal flexion). The capsule was removed. 1 lateral malleolus, 2 malleolar fossa, 3 peroneal groove of the fibula and peroneal tendons traject, 4 posterior talofibular ligament, 5 posterior intermalleolar ligament or tibial slip (capsular insertion cut), 6 lateral talar process, 7 medial talar process, 8 superficial component of the posterior tibiofibular ligament, 9 deep component of the posterior tibiofibular ligament or transverse ligament, 10 calcaneofibular ligament, 11 malleolar insertion of fibulotalocalcaneal ligament or Rouvière and Canela-Lazaro ligament (cut), 12 tunnel for flexor hallucis longus tendon, 13 flexor hallucis longus retinaculum, 14 deep posterior tibiotalar ligament of the medial collateral ligament (deep layer), 15 tibiocalcaneal ligament of the medial collateral ligament (superficial layer), 16 tibialis posterior tendon (cut) and tendon traject, 17 calcaneal or Achilles tendon (cut), 18 interosseous membrane, 19 foramen in the interosseous membrane for the anterior peroneal artery (Drawing courtesy of Pau Golano)

24.4 Etiology

Posterior ankle impingement syndrome is a clinical pain syndrome that reflects the most common cause of posterior ankle pain. It can be provoked by a forced hyperplantar flexion movement of the ankle [11–13]. In the event of a soft tissue or bony posterior impingement of the ankle, plantar flexion induces conflict between the posterior malleolus of the distal tibia and the postero-superior calcaneal bone. A bony prominent posterior process of the ankle occurs in almost 7 % of the sports population and can present as a hypertrophic posterior talar process or as an os trigonum. Although apparent posterior bony prominences caused by acute or repetitive overload (micro-) trauma can induce posterior ankle pain, they are not necessarily associated with the posterior ankle impingement syndrome.

Soft tissue impingement in the posterior ankle region can also occur and is frequently disregarded. It is triggered mainly by hypertrophic FHL musculo-tendinous tissue, additional tendinous or doubled tendon structures and post traumatic scarification [9].

Since an acute forced hyperplantar flexion movement on the ankle or a repetitive overload induces the bony or soft-tissue conflict in the posteriorly located components of the ankle joint, these lesions are seen mainly in a sport specific population. The classical example of repetitive overload is seen in ballet dancers, where the forced plantar flexion during “en pointe” and “demi pointe” positioning induces repetitive impingement on the posteriorly located soft tissue components. Other types of sports that often lead to the posterior ankle impingement syndrome include football, swimming, cycling and any other sport in which the mechanism of injury is a repetitive forced plantar flexion or an acute setting (for example during a blocked kicking action in football). If the lesion occurs due to compression of the os trigonum between the distal tibia and calcaneal bone, it can lead to displacement of the os trigonum, disabling soft tissue inflammatory processes, or even fractures of the processus posterior tali or distal tibia (Fig. 24.4) [9].

Fig. 24.4

Lateral radiograph of the right ankle shows the os trigonum, a possible bony impingement trigger in the ankle

24.5 Clinical and Diagnostic Features

Clinically, posterior impingement can be much more difficult to detect and diagnose than other types of ankle impingement because the affected structures lie much deeper, and it can be mimicked by or coexist with other disease processes such as peroneal tendinopathy, retrocalcaneal bursitis, osteochondral lesions of the posterior talar dome, Achilles tendinopathy, flexor halluces longus tendinopathy or tenosynovitis, posterior tibial osteochondral injuries, tarsal tunnel compression, tarsal coalition, and Haglund deformity. Patients will complain of chronic deep posterior ankle pain that is worsened with push-off activities such as jumping. Physical examination includes palpation over the posterolateral and posteromedial process. Patients that suffer from posterior ankle impingement present with a posteriorly localized ankle pain during a (forced) plantar flexion movement. The posterior ankle impingement test is a pathognomonic test to identify the clinical diagnosis of posterior ankle impingement. In the test, the ankle is passively and quickly forced from neutral to hyperplantar flexion position; if the patient encounters suddenly recognizable posteriorly located ankle pain the diagnosis is confirmed. To increase compression on the posterolateral structures of the ankle, plantar flexion, external rotation and eversion movements can be applied during clinical testing.

Since the neurovascular structures and tendons are localized in the posteromedial region of the ankle, this area is not always easily palpated compared to the clinical examination of the posterolateral part of the ankle [7].

Diagnosis can be confirmed with significant reduction in pain following injection of an anesthetic into the posterolateral capsule of the tibiotalar joint. MRI is useful for more accurately identifying the anatomic site of abnormality, as well as revealing coexisting pathologies. Fortunately, rest is often adequate therapy regardless of whether the symptoms are acute or chronic. When non-operative measures have failed, open or arthroscopic removal of the os can quickly return the footballer to play. Calder et al. demonstrated the effectiveness of posterior ankle arthroscopy in the treatment of posterior ankle impingement syndrome in the elite footballer, with return to training expected at an average of 5 weeks.

24.6 Fractures

24.6.1 Fractures of the Lateral Tubercle and OS Trigonum Complex

The lateral tubercle serves as an attachment to the talocalcaneal and the posterior talofibular ligament. An avulsion type (Shepherd) fracture may be the result of a plantarflexion and inversion force, while a compression type fracture is usually the result of the posterior process being squeezed between the posterior tibia and calcaneus in extreme plantarflexion. The same mechanisms can lead to injuries to the os trigonum in individuals that have it. Athletes will usually present with pain and swelling in the posterolateral ankle. They will often ascribe the onset of symptoms to kicking the ball, and will have tenderness to deep palpation in the area between the Achilles tendon and the lateral malleolus, and exacerbation of symptoms on plantar flexion of the ankle; compression of the fracture by the FHL by dorsiflexion of the great toe can also be occasionally seen. A plain lateral radiograph provides a good view of the lateral tubercle. Care must be taken when reviewing the radiograph so as not to consider a fracture of the lateral tubercle as a normal os trigonum. The latter when present usually has a smooth cortical rim, compared to an irregular outline in the case of a fracture of the tubercle. Fractures of the os trigonum can also be found, but are rare. A fine-cut CT scan is useful to identify fractures and assess displacement, but an MRI scan is also advisable to identify possible bone bruising or injury to the synchondrosis between the os trigonum and the lateral tubercle [13].

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