Posterior Ankle Arthroscopy

James D.F. Calder

Abstract

Posterior ankle arthroscopy was first published by van Dijk in 2000 ¹ who described using a two-portal endoscopic approach, making it possible to appropriately visualize the posterior ankle structures and safely manage these. Since then, the spectrum of different pathologies involving the posterior ankle that can be addressed arthroscopically has grown significantly. This chapter outlines these pathologies and describes how they can be addressed arthroscopically through minimal incisions, with limited soft-tissue disruption, allowing faster return to activities and athletic function.

Keywords: posterior ankle, arthroscopy, impingement

38.1 Indications and Pathology

• Posterior ankle impingement (PAI)—soft tissue or bone (os trigonum, avulsed bone fragments, and loose bodies).

• Release of flexor hallucis longus (FHL) tendon.

• Soft-tissue release for restricted ankle dorsiflexion (DF).

• Treatment of ankle osteochondral lesion (OCL).

• Achilles tendon (AT) pathology—noninsertional Achilles tendinopathy (NIAT) with release of plantaris tendon and insertional AT symptoms with Haglund’s deformity and retrocalcaneal bursitis.

• Hindfoot arthritis—subtalar joint (STJ) fusion and also posterior ankle joint fusion when there is concern regarding anterior soft-tissue envelope (e.g., following trauma).

38.1.1 Clinical Evaluation of Pathology

• PAI—posterior ankle pain on forced plantar flexion of the ankle with or without restricted plantarflexion.

• FHL pathology—posteromedial (P/M) ankle pain with or without crepitus or “ratcheting” of the FHL tendon during FHL movement.

• Restricted ankle DF—usually several months following severe ankle trauma such as ankle dislocation. No obvious tightness of Achilles/gastrocnemius but a block coming up into DF frequently associated with anterior ankle pain but without obvious bone impingement anteriorly on imaging.

• OCL ankle—deep ankle pain during activities.

• Insertional AT pathology—swelling and tenderness medial and lateral to AT sometimes with “ballotable” bursa palpable.

• Hindfoot arthritis—generalized swelling and stiffness around hindfoot. Important to assess quality of soft tissues and scarring in relation to AT for planning of incisions for fixation.

38.1.2 Radiographic Evaluation

• Weight-bearing X-rays (anteroposterior [AP]/lateral). Os trigona are more easily demonstrated on lateral views with 20-degree internal rotation. AP ankle in 30 degrees may demonstrate OCL posterior talus. Lateral view of calcaneus will demonstrate bone spur within the AT and this may not be amenable to endoscopic excision but may suggest open surgery if indicated.

• Magnetic resonance imaging (MRI). Useful for assessment of OCL and presence of active pathology in subchondral bone rather than just an incidental finding. Soft-tissue PAI is demonstrated well as is pathology surrounding the FHL. Bone marrow edema in the synchondrosis of the os trigonum and posterior talus demonstrates whether there is active bone pathology contributing to PAI symptoms (Fig. 38.1), and pathology such as ganglion cyst may be identified (Fig. 38.2). Assessment of AT pathology is important—if there is significant degenerative change with multiple partial tears, fissures, or incomplete avulsions from the tendon insertion, then endoscopic treatment of the Haglund or retrocalcaneal bursitis alone may be unsuccessful and a formal open procedure should be considered.

• Computed tomography (CT). Very useful to confirm the presence of fragmentation of an os trigonum and avulsed fragments or loose bodies. Small fragments from avulsion of the posterior inferior tibiofibular ligament (PITFL) may be more easily demonstrated on CT (Fig. 38.3).

• Ultrasound (US). Accurate assessment of presence and degree of tendinosis of AT.

38.1.3 Nonoperative Options

• PAI—strapping to prevent excessive plantarflexion and proprioceptive training and strengthening to reduce lateral ankle ligament instability which may exacerbate PAI symptoms. US-guided injections of corticosteroid and local anesthetic may reduce PAI—more effective and even curative in soft-tissue PAI but frequently only temporary benefit in bone PAI (os trigonum), and reports suggest longer recovery and less successful outcome following multiple injections for bone PAI.²

Fig 38.1 MRI scan demonstrating bone marrow edema in the os trigonum, the synchondrosis and the adjacent talus.

Fig 38.2 MRI demonstrating ganglion cyst in patient with posterior ankle impingement.

• OCL ankle and hindfoot arthritis—modification of activities and use of oral analgesics. Hyaluronic acid injections.³^,⁴

• AT pathology—eccentric stretching and strengthening exercises, heel raise, oral analgesics. Avoid deep DF eccentric exercises in insertional AT pathology given this may exacerbate irritation of bursitis. Extracorporeal shockwave therapy. US-guided paratenon stripping injections (high-volume injection of local anesthetic without corticosteroid) may help with paratendinitis and NIAT. US-guided corticosteroid injection into a retrocalcaneal bursitis is controversial because of the risk of AT rupture but may be considered in the absence of significant AT tendinosis, and consider temporary protection in a boot for 2 weeks.⁵

• FHL pathology—US-guided injection of corticosteroid and local anesthetic.

• Soft-tissue contractures—physiotherapy stretching and night splints. US-guided injections tend to be unhelpful.

38.1.4 Relevant Contraindications

• Usual medical and vascular assessment.

• Local scar tissue from previous trauma and surgery (particularly important around the AT where there is a poor blood supply to local soft tissues).

• Smoking and diabetes are significant risk factors for soft-tissue complications following surgery related to the AT; however, endoscopic/posterior ankle arthroscopy has the advantage of less soft-tissue dissection compared to open procedures.

38.2 Goals of Surgical Procedure

• Reduce symptoms of pain or stiffness.

• Enable predictable and earlier return to activities than seen with open procedures.

• Reduce risk of complications seen with open procedures.

Fig 38.3 CT scan demonstrating avulsed fragments from avulsion of PITFL resulting in posterior ankle impingement.

38.3 Advantages of Surgical Procedure

• Clear views of pathology—it is easier to visualize the posterior ankle with an arthroscope than through a small incision.

• Minimal soft-tissue dissection and less scarring—improves wound healing and enables rehabilitation to commence earlier with improved speed of recovery.

38.4 Key Principles

• A standard 4-mm 30-degree knee arthroscope is routinely used. The cannula is 6 mm, which allows for good fluid flow and excellent vision. The small joint (2.7 mm × 67 mm) 30-degree arthroscope may be used, but with the 2.9-mm cannula, the fluid flow is more restricted and thus less optimal views are obtained. The author prefers the longer small joint 30-degree arthroscope (2.7 mm × 120 mm) using the 4.6-mm cannula given that this gives the best fluid flow and good views (Smith & Nephew, Boston, MA).

• A fluid management system is not a perquisite but is preferred by the author, ensuring pressure is kept to 35 mm Hg.

38.5 Operative Technique

38.5.1 Preoperative Preparation and Patient Positioning

• Fully informed consent and appropriate marking of the leg (the author insists on an “X” on the heel to avoid any confusion of site of surgery when the patient is turned).

• Thigh tourniquet is applied prior to turning the patient—it is more difficult to apply after turning.

• Spinal or general anesthesia.

• Patient is turned semi-prone into the “recovery position” with the operated leg lowermost.⁶ This reduces the need for intubation and paralysis during general anesthetic, and a laryngeal mask may be used. A bolster is placed to support the chest in three-fourths turned position but the pelvis should be flat on the table so that the foot points vertically down. The foot should be supported with a gel pad under the ankle to raise it from the table and the foot placed over the end of the bed. It is important to ensure that the ankle may be fully dorsiflexed during the procedure and it is not restricted by the end of the table.

38.5.2 Surgical Procedure

Universal Technique for Posterior Ankle Arthroscopy

• Identify sites for posterior portals—medial and lateral to AT (Fig. 38.4).

• Standard positioning of the portals as described by van Dijk et al.¹

• Use a hemostat through the posterolateral (P/L) portal to dissect toward the posterior talar process using “push and spread” technique. It is important to aim for the first web space as deviation may injure neurovascular structures medially or peroneal tendons laterally (Fig. 38.5).

• Introduce the arthroscope and then use a hemostat through the P/M portal perpendicular to the arthroscope. Once it reaches the arthroscope, follow along to the end of the arthroscope, and under direct vision, spread the hemostat to create a working space in the hindfoot into which a 4.5 or 5.5-mm shaver may be introduced (e.g., Incisor or Bone Cutter blades, Dyonics, Boston, MA).

• Ensure that the blade is pointing directly toward the camera and use suction to bring tissue into the blade in oscillating mode with a sweeping action proximally and distally to clear tissue from the posterior ankle/STJ. Normally, the STJ is first to be seen. Clear tissue from the superior surface of the posterior talar process until the FHL comes into view, always keeping the blade toward the camera.

• Therefore, the arthroscope is kept “extra-articular” as only rarely does it need to be placed “inside” the ankle.

FHL Release and Excision of Os Trigonum

• Once the FHL is observed, ensure that dissection is not made medial to this, as this may compromise the neurovascular bundle.

• The FHL tendon sheath may be released with the shaver or sharp cutting instruments.

• Occasionally, loose bodies become trapped in the FHL sheath causing irritation of the FHL and pseudolocking of the ankle. The may be “milked” digitally from the distal sheath (around the inferior sustentaculum tali) and then removed arthroscopically (Fig. 38.6).

• The os trigonum can be shaved away. The synchondrosis may be identified with a small osteotome or periosteal elevator loosening the os trigonum enabling it to be removed whole.

Treatment of Ankle OCL

• Gaining access to the ankle joint for treatment of an OCL or fusion of the ankle requires excision of the posterior intermalleolar ligament.⁷ The 30-degree angle of the arthroscope may then be used to gain excellent vision of the posterior talar and tibial surfaces by rotating the camera.

• Standard techniques of debridement and microfracture are used.