Operative Techniques in Orthopaedic Surgery (4 Volume Set) 1st Edition

496. Endoscopic Treatment of Posterior Ankle Impingement Through a Posterior Approach

Phinit Phisitkul and Annunziato Amendola

DEFINITION

images Posterior ankle impingement syndrome is a clinical disorder characterized by posterior ankle pain that occurs in forced plantarflexion. It can be caused by an acute or chronic injury, with the os trigonum or trigonal process of the talus as the most offending structure.10,19

images Synonyms used for posterior ankle impingement syndrome include posterior block of the ankle, posterior triangle pain, talar compression syndrome, os trigonum syndrome, os trigonum impingement, posterior tibiotalar impingement syndrome, and nutcracker-type syndrome.4,11,20,36

images The os trigonum is a secondary ossification center of the talus. It mineralizes between the ages of 11 and 13 years in boys and 8 and 11 years in girls. It fuses with the posterior talus within 1 year, forming the posterolateral process, often called the Stieda or trigonal process. The os trigonum remain as a separate ossicle in 1.7% to 7% of normal feet, twice as often unilaterally as bilaterally.3,8,16,24

ANATOMY

images The posterior process of the talus is composed of a smaller posteromedial process and a larger posterolateral or trigonal process flanking the sulcus for the flexor hallucis longus (FHL) tendon.

images The os trigonum may be found in connection with the posterolateral tubercle (FIG 1). It is completely corticalized and has three surfaces: anterior, inferior, and posterior.

images

FIG 1 • Os trigonum.

images The anterior surface connects to the posterolateral tubercle via fibrous, fibrocartilaginous, or cartilaginous tissue. The inferior surface forms the posterior part of the talocalcaneal joint.

images The posterior surface is nonarticular and has the attachments of posterior talofibular ligament, posterior talocalcaneal ligament, deep layer of the flexor retinaculum, and the talar component of the fibuloastragalocalcaneal ligament of Rouviere and Canela Lazaro.28

images The tibialis posterior tendon, the flexor digitorum longus tendon, and the flexor hallucis longus tendon situate in their own fibrous tunnels in continuity with the fascia of the deep posterior compartment.

images The neurovascular bundles are just medial and posterior to the flexor hallucis longus tendon at the level of the ankle joint, with the tibial nerve as the most lateral structure (FIG 2).

images In some variants, the posterior tibial artery can be thin or absent (0–2%), with the dominant peroneal artery traversing across the posterior ankle toward the tarsal tunnel.2,6

PATHOGENESIS

images Most cases of posterior ankle impingement syndrome occur in athletes such as ballet dancers or soccer players who have sustained acute or repetitive injuries with the ankle in forced plantarflexion, causing the “nutcracker effect”12,20 (FIG 3). Ankle sprain may cause avulsion fracture of the posterior talofibular ligament and secondary impingement.15,21,25,34

images Symptoms can be aggravated by any structures localized between the posterior tibial plafond and the calcaneal facet of the posterior subtalar joint, such as the os trigonum, long trigonal process, flexor hallucis longus tendon, posterior inferior tibiofibular ligament, intermalleolar ligament, and any osseous, articular cartilage, capsule, or synovial lesions of the posterior ankle or subtalar joint.

images FHL tenosynovitis is commonly associated with posterior ankle impingement due to the intimate relationship between the tendon and the os trigonum or the trigonal process at the posterior aspect of the talus. This lesion can be an associated injury or secondary to the inflamed surrounding structures.17,26,30

images

FIG 2 • Neurovascular bundle posteromedial to the FHL tendon.

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FIG 3 • Forced plantarflexion as a cause of the nutcracker effect in the os trigonum.

NATURAL HISTORY

images The natural history of posterior ankle impingement is currently unknown. Os trigonum is a benign condition and usually is asymptomatic.

images When symptomatic, nonoperative treatment has been found to be successful in 60% of cases. However, Hedrick and McBryde10 reported that only 40% of those successfully treated patients could achieve full preinjury activity levels. The prognosis with nonoperative treatment is generally poor in high-activity patients such as ballet dancers.20

PATIENT HISTORY AND PHYSICAL FINDINGS

images The routine history should include sex, age, occupation, sports activities, and mechanism of the injury.

images Patients should be asked for the description of pain, its location, and any aggravating positions or activities. Pain from the impingement usually is directly posterior or posterolateral to the ankle joint. Pain in the posteromedial aspect may be associated with tenosynovitis of the FHL tendon, which is usually described as pain along the tendon longitudinally. Aggravation of the symptoms with the ankle in full plantarflexion is essential to the diagnosis.

images Examination must be performed to rule out other pathologies causing posterior ankle and hindfoot pain, such as Achilles tendinopathy, Haglund syndrome, “pump bump” syndrome, tibialis posterior tendinitis, and peroneal tendon injuries. Diligent palpation of the described structures for pain is recommended.

images The physical examination should include:

images Examination for retromalleolar swelling. Mild swelling occurs in posterior ankle impingement syndrome. Significant swelling should raise the suspicion of peroneal or tibialis posterior tenosynovitis.

images Passive ankle plantarflexion. In a positive test, sharp pain or crepitus is produced at full plantarflexion.

images In FHL tenosynovitis, pain is produced with active/passive motion of the hallux while a thumb palpates the tendon for tenderness and crepitus. The presence of FHL tenosynovitis should be documented, and it should be treated accordingly.

images

FIG 4 • Lateral radiograph of the ankle.

images Tenderness from FHL tenosynovitis is produced with active/passive motion of the hallux while a thumb palpates the tendon for tenderness and crepitus. The presence of FHL tenosynovitis should be documented, and it should be treated accordingly.

images Tenderness of other posterior ankle structures. Individual palpation of the peroneal tendons, tibialis posterior tendon, Achilles tendon, and posterior aspect of the calcaneal tuberosity is essential to exclude other pathologies. Palpation of the os trigonum itself is difficult due to its depth. Other diagnoses should be considered if there is no pain with passive ankle plantarflexion and the positive test for other possible lesions in spite of the presence of the os trigonum on radiographs.

IMAGING AND OTHER DIAGNOSTIC STUDIES

images A lateral radiograph of the ankle usually demonstrates the osseous lesions sufficiently (FIG 4). Lateral radiographs can be taken in full ankle plantarflexion and slight external rotation of the limb to visualize impingement from the os trigonum.9

images Bone scanning has been reported to identify the symptomatic os trigonum. It is not routinely obtained, however, and does not replace accurate history taking and physical examination (FIG 5). False-positive results in patients with high activity levels make this study less useful.29

images CT scan can help clarify osseous or osteochondral lesions, especially when the posteromedial facet fracture is suspected.7

images MRI is the most useful imaging examination for posterior ankle impingement syndrome (FIG 6). Anatomic variants and a range of osseous and soft tissue abnormalities have been found to be associated with this condition. Posterior tibiotalar synovitis and marrow edema within one or more of the tarsal bones were found in all cases. In contrast, os trigonum was found in only 30% of cases.5,23,26

images Diagnostic injection can be helpful when the signs and symptoms are inconclusive.14,25 The postinjection symptoms have been shown to be parallel to results after surgical excision of the os trigonum. However, injection directly into the junction between the os trigonum and the talus is difficult and must be done under fluoroscopic guidance in experienced hands.

images

FIG 5 • Positive bone scan.

DIFFERENTIAL DIAGNOSIS

images Haglund syndrome

images Tendinitis (Achilles tendon, peroneal tendons, posterior tibial tendons)

images Loose bodies

images Ankle or subtalar arthritis

NONOPERATIVE MANAGEMENT

images Nonoperative treatment is always the first approach. However, it has shown less than optimal results in the published literature, with, at best, a 60% rate of improvement plus long-term modification of activities.10

images Avoidance of aggravating activities such as forced plantarflexion is the most important factor, because it will avoid impingement and aggravation of the inflammatory response. This measure may not be tolerable in athletes who routinely require this position, such as ballet dancers and soccer players.

images

FIG 6 • MRI examination for posterior ankle impingement syndrome.

images Supportive treatments include rest, ice, anti-inflammatory medications, and immobilization in a short-leg walking cast.

images One or two cortisone injections under fluoroscopic guidance have shown more than 80% response rate at 2 years.25 Its use was not routinely recommended due to the risk of FHL tendon rupture and potential disabilities especially in ballet dancers.

images Physical therapy can be instituted as symptoms improve. It consists of phonophoresis, isometric exercises, heel cord stretching, and selected isometric strengthening.

SURGICAL MANAGEMENT

images Indications

images Failure of nonoperative treatment after at least 3 months

images Inability to to return to required activities after nonoperative treatment

Preoperative Planning

images All imaging studies are reviewed. MRI is helpful in the evaluation of associated lesions.

images All the pathologies should be carefully detected. Surgical steps with informed consent can be added accordingly, such as loose body removal, treatment for osteochondritis dissecans lesions, or an open FHL repair.

images When surgery is indicated, the treatment for an os trigonum, an acute or chronic fracture of the trigonal process, or an intact large trigonal process is virtually the same. Further studies, eg, CT scan, to distinguish them may not be necessary.

images If arthroscopic or open surgery is planned, the posterior tibial pulse must be palpable in the soft spot posterior to the medial malleolus, because an absence or a minor artery may be associated with a dominant peroneal artery. This artery traverses across the posterior ankle and is at high risk during arthroscopy.

Positioning

images The patient is placed in the prone position with standard padding (FIGS 7 AND 8).

images The patient's ankles are at the level just distal to the end of the bed to leave enough room for possible anterior or lateral arthroscopic portals.

images The surgeon's body can be used to dorsiflex the ankle by leaning forward.

images

FIG 7 • Prone positioning.

images

FIG 8 • Ensure adequate padding of all surfaces.

Approach

images The posterior aspect of the ankle and subtalar joints can be accessed open or arthroscopically.

images Open approaches can be posteromedial or posterolateral, on either side of the Achilles tendon.

images The posteromedial approach is recommended by the author. When the bony impingement is accompanied by pathologies in the neurovascular bundles or lesions in the FHL tendon that may require a repair, a posteromedial approach is advantageous.

images The posterolateral approach also may be used for cases that require only excision of the os trigonum and trigonal process or release of the FHL tendon.

images The arthroscopic approach has advantages over open surgeries in terms of minimizing surgical injury, postoperative pain, and early return to activities.

images We prefer the prone over the supine or lateral decubitus position because it provides a more direct approach, minimizing the risk of instrument skiving off toward the neurovascular bundles.

images Apart from the magnification advantage, we have found that this method also aids in visualization of intra-articular pathologies.27

images This technique requires familiarity with the hindfoot anatomy and arthroscopic skills.

TECHNIQUES

ESTABLISHMENT OF PORTALS

images The anatomic landmarks of the posterior ankle are drawn, including the Achilles tendon, the medial and lateral malleoli, and the superior aspect of the calcaneal tuberosity.

images The posterolateral and the posteromedial portals are located 1.5 cm proximal to the superior aspect of the calcaneal tuberosity on either side of the Achilles tendon (TECH FIGS 1 AND 2).

images Ankle joint injection can be performed through the posterolateral portal, but it is not necessary, because the joint will be inspected easily after the os trigonum or the trigonal process has been removed.

images

TECH FIG 1 • Placement of posteromedial and posterolateral portals with the patient in the prone position.

images The posterolateral portal is established first with a vertical skin incision, followed by blunt dissection with a straight hemostat. The tip of the hemostat should be kept just next to the Achilles tendon laterally to minimize injury to the sural nerve.

images The dissection proceeds through a fat layer directly anteriorly.

images The os trigonum usually is palpable, and a blunt trocar is inserted toward its superior aspect.

images A 4-mm arthroscope is inserted through the cannula.

images Next, the posteromedial portal is established at the same level just medial to the Achilles tendon.

images A straight hemostat is used to dissect into the same soft tissue tunnel as the arthroscope. The hemostat is advanced while it is kept in contact with the arthroscopic cannula until the tip is seen by the arthroscope.

images The soft tissue is gently dilated. A full-radius 3.5-mm shaver is inserted into the posteromedial portal until the tip is seen (TECH FIGS 3 AND 4).

images

TECH FIG 2 • Topographical landmarks of the pertinent structures.

images

TECH FIG 3 • The hemostat is visualized when creating the second portal.

images

TECH FIG 4 • The 3.5 mm shaver is visualized through the second portal.

DÉBRIDEMENT OF THE SOFT TISSUE

images The initial débridement of the fatty tissue is performed first to make room for the arthroscopic maneuvers. This step will improve visualization tremendously.

images The shaver is kept deep just above or below the os trigonum, with its cutting surface turned laterally.

images The shaver is gradually moved medially until the FHL tendon is seen. The FHL tendon indicates the location of the neurovascular bundles, which lie medial and superficial to it.

images The os trigonum is débrided off all the attached soft tissue circumferentially (TECH FIG 5).

images

TECH FIG 5 • The os trigonum is débrided of soft tissue attachments with a shaver circumferentially.

images Medially, the retinaculum of the FHL is released off the os trigonum with a shaver or arthroscopic scissors (TECH FIG 6).

images Tenosynovitic lesions of the FHL, if seen, may require a release and débridement further distally. Great care is taken to release the fibrous sheath from only the posterior attachment on the calcaneal wall. A partial tear of the FHL can be débrided, but a tear greater than 50% may require an open repair.

images The posterior talofibular ligament attached on the lateral aspect of the os trigonum is released.

images

TECH FIG 6 • The FHL is visualized and released from its soft tissue attachments to the os trigonum.

RESECTION OF THE OS TRIGONUM AND TRIGONAL PROCESS

images The synchondrosis is palpated by a Freer elevator coming from the superior aspect.

images Next, the tip of the instrument is pushed into the synchondrosis.

images Cracking of the synchondrosis is performed by levering maneuvers from either the superior or inferior surface (TECH FIG 7).

images

TECH FIG 7 • Lever the os trigonum loose from its talar attachments with a Freer elevator.

images The os trigonum is removed as a whole using a grasper (TECH FIG 8). In the presence of an intact enlarged trigonal process it is removed entirely with a burr.

images The posterior aspect of the talus is evaluated, and any sharp bony edges are rounded off (TECH FIG 9).

images

TECH FIG 8 • The os trigonum is removed as a whole using a grasper.

images The most posterior aspect of the articular cartilage of the posterior talar facet of the subtalar joint is always removed together with the os trigonum.

images

TECH FIG 9 • The posterior aspect of the talus is evaluated and rounded off, particularly around the FHL tendon.

EVALUATION OF ASSOCIATED LESIONS

images The posterior aspect of the ankle joint is evaluated. Synovitis or a thickened intermalleolar ligament is débrided. Stay lateral to the FHL tendon. Loose bodies are removed if present. Intra-articular views of the ankle joint are best achieved with a 2.7-mm arthroscope.

images The subtalar joint is evaluated in the same manner (TECH FIG 10). The dynamic view of the hindfoot is inspected when the ankle is manipulated into full plantarflexion.

images There should be no impingement at the completion of the procedure.

images If arthroscopic evaluation or treatment of the anterior ankle joint is required, it can be performed in two ways.

images The first way is to reposition the patient into the supine position and redrape the limb.

images The second way is to bend the knee to 90 degree and perform the anterior ankle arthroscopy in the upsidedown manner. This requires experience and familiarity of the ankle anatomy.

images

TECH FIG 10 • Multiple views of the ankle and subtalar joint.

images

POSTOPERATIVE CARE

images Portal incisions routinely are left unsutured.

images A compressive soft dressing is applied. The patient is informed about the possibility of some drainage in the first couple of postoperative days. The dressing can be changed if necessary.

images Leg elevation is encouraged.

images No immobilization is required.

images Patients can bear weight as tolerated in a postoperative shoe.

images When acute pain subsides, usually 2 to 3 days postoperatively, patients can begin early range-of-motion and strengthening exercise.

images Full activities are allowed gradually as tolerated.

OUTCOMES

images Nonoperative treatment has not shown promising results, especially in high-demand athletes, but a success rate of more than 80% could be achieved when cortisone injections are routinely given under fluoroscopic guidance.10,25

images When nonoperative treatment has failed, excellent outcomes have been reported with either open or arthroscopic resection of the os trigonum.1,13,18,20,22,32,33

images Arthroscopic techniques can help minimize morbidities associated with open dissection, such as a painful scar, severe postoperative pain, and wound complications. It requires arthroscopic skills and familiarity with hindfoot anatomy.31,35

COMPLICATIONS

images Neurovascular injuries are possible with either arthroscopic or open approaches. Neurapraxia of the tibial, peroneal, and sural nerves has been reported; most patients recovered spontaneously. Permanent sensory deficit and neuroma formation have occurred when the nerves were transected, especially the sural nerve when the open posterolateral approach is used.1

images Symptoms can persist after operative treatment. Correct diagnosis and adequate treatment of all associated pathologies are the keys.

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