Diagnostic and Operative Ankle and Subtalar Joint Arthroscopy

Operative Setup

In general, the procedure is carried out as outpatient surgery under general anesthesia or epidural anesthesia. Patients can be placed in various positions according to the surgeon’s preference, with a supine position with slight elevation of the ipsilateral buttock being mostly used. The heel of the affected foot rests on the very end of the operating table in order to make it possible for the surgeon to fully dorsiflex the ankle by leaning against the sole of the patient’s foot. For the treatment of posterior ankle problems, the patient is placed in prone position and a small support is placed under the lower leg, making it possible to move the ankle freely ( Fig. 18.1 ). In both settings, a tourniquet is placed around the upper thigh.

There are some important considerations in deciding whether to use dorsiflexion or traction for routine anterior ankle arthroscopy. When saline is introduced in the dorsiflexion position, the anterior working area and any bony or soft-tissue impediment in front of the medial malleolus, in front of the lateral malleolus, at the talar neck, or at the distal tibia can be adequately visualized and treated. For the treatment of anterior impingement lesions, synovitis, ossicles, and loose bodies, it therefore is beneficial to perform the procedure without distraction. In this dorsiflexed position, the talus is concealed in the joint, thereby protecting the cartilage from potential iatrogenic damage. Moreover, loose bodies usually are located in the anterior compartment of the ankle joint and with dorsiflexion creating an anterior working area, removal is facilitated. On the other hand, distracting the joint makes it possible for the loose body to fall into the posterior aspect of the joint, thus making removal more difficult or impossible by an anterior approach. The same is true for the removal of ossicles and bony spurs by a chisel or burr. Distraction of the joint results in tightening of the anterior capsule, thus making it more difficult to identify anterior osteophytes, ossicles, loose bodies, and soft-tissue impediments. Furthermore, when portals are created and instruments are introduced in the distracted position, this may result in iatrogenic cartilage damage at the talar dome.

The main reason for inspection of the talar dome and tibial plafond is for treatment of an osteochondral lesion. A clinical diagnosis must be established preoperatively using history, physical examination, and standard x-rays. In case of doubt about the existence or the exact location and size of a defect, a preoperative spiral computed tomography (CT) scan or magnetic resonance imaging (MRI) can be performed. Knowing the exact location of a defect makes it possible to decide preoperatively whether distraction will be necessary or whether the osteochondral lesion can be approached in a forced plantarflexed position of the foot. In our experience, more than 90% of medial and lateral talar dome lesions can be treated in a hyperplantarflexed position. Distraction may be beneficial when an osteochondral lesion is located in the posterior part of the medial or lateral talar dome, the tibial plafond, or when a soft-tissue impediment, ossicles, or an impregnated loose body is located in the joint space between fibula and tibia (intrinsic syndesmotic area). For posterior ankle problems, for example an osteochondral lesion in the posterior quarter of the talar dome or in the posterior part of the tibial plafond, two-portal posterior ankle arthroscopy is an important alternative ( Fig. 18.2 ).

Arthroscopic equipment

Both a 4.0-mm and a 2.7-mm arthroscope with 30-degrees obliquity can be used for ankle arthroscopy, depending on the indication. Small-diameter, short arthroscopes yield an excellent picture that is difficult to distinguish from a standard 4.0-mm scope. The small-diameter arthroscope sheet, however, cannot deliver the same amount of irrigation fluid per time as the standard sheet, causing an important drawback when motorized instruments are used, since these cases must benefit from an adequate amount of irrigation fluid. For routine arthroscopic procedures such as anterior impingement syndrome, loose body removal, treatment of synovitis, and the vast majority of osteochondral defects, it is beneficial to use the 4.0- mm arthroscope. A 2.7-mm arthroscope should be reserved for the treatment of osteochondral lesions of the posterior third of the talar dome (when not approached by a posterior ankle arthroscopy), pathology of the articular part of the tibiofibular joint, such as a soft-tissue impediment or impregnated ossicles or loose bodies, or other posterior ankle problems that are treated by an anterior approach. Use of a 2.7-mm scope usually necessitates the creation of a third posterolateral portal to maintain adequate flow in the joint.

Instrumentation

An 18-gauge spinal needle is used to distend the joint and to locate the anterolateral portal by allowing precise positioning under direct vision of the portals. The probes used in ankle arthroscopy should be about 1.5 mm in diameter to reach the small recesses of the gutters and to lift up under loose articular cartilage. An angled tip is desirable to touch over the dome-shaped talus and flat tibia. Another important instrument is the grasper. For the removal of small, loose bodies in soft tissue, a flat-tipped grasping forceps with fine teeth can be used. For larger loose bodies and soft-tissue fragments, a cup-shaped, jaw-grasping forceps with serrated edges is better. Small-joint basket forceps with different tip designs help to remove soft-tissue and chondral fragments. Various small-joint curettes, either straight or curved, are particularly valuable for removing osteochondral lesions and trimming of articular cartilage edges. Small-joint osteotomes and chisels are available to remove osteophytes and ossicles and can facilitate tissue elevation. Sometimes a small periosteal elevator can be useful. Motorized instruments can excise larger volumes of tissue than conventional hand instruments and suction it quickly out of the joint. They also can be used for debridement of large osteochondral lesions. A power burr is useful for abrading or excising hard bone fragments.

Irrigation

Different fluids can be used for arthroscopic irrigation during ankle and foot arthroscopy. Lactated Ringer is used most common because it is physiologically compatible with articular cartilage and is rapidly reabsorbed if extravasated from the joint. Other options include glycine and normal saline. When a 4-mm arthroscope is used, gravity inflow usually is adequate if the fluid is introduced through the arthroscope sheet. When a 2.7-mm arthroscope is used, the gravity inflow should be introduced through a separate (posterolateral) cannula. An alternative is to use an arthroscopic pumping device.

Anterior Portals

Anteromedial Portal

The anteromedial portal should be made first, since it is easy to access. This is especially true with the ankle in hyperdorsiflexion. The exact point of entry in this position is easily reproducible, and the risk of neurovascular damage is minimal. The anteromedial portal is placed just medial to the anterior tibial tendon at the joint line ( Fig. 18.3 ). In the hyperdorsiflexed position, a local depression can be palpated. In the horizontal plane, this depression is located between the anterior tibial rim and the talus. During palpation the thumb first detects the interval in the horizontal plane and subsequently locates the vertical position. In the vertical position, the anterior tibial tendon is the landmark. One should palpate the anterior tibial in the dorsiflexed position. In this dorsiflexed position the anterior tibial tendon moves 1 cm lateral. The location of the anteromedial portal now can be marked onto the skin just medial from the anterior tibial tendon. Care must be taken not to injure the saphenous vein and nerve traversing the ankle joint along the anterior edge of the medial malleolus. By moving the ankle joint from the plantarflexed position to the dorsiflexed position, the talus can be felt to move in relation to the distal tibia. The thumb gets locked into the soft spot in the hyperdorsiflexed position. A small longitudinal incision is made through the skin only just medial from the anterior tibial tendon. Blunt dissection is performed with a mosquito clamp through the subcutaneous layer and through the capsule into the ankle joint. With the ankle in the forced dorsiflexed position, cartilage damage is avoided. In this forced dorsiflexed position, the arthroscope shaft with the blunt trocar is introduced. When the trocar is felt to contact the underlying bony joint line, the shaft with the blunt trocar is gently pushed further into the anterior working area in front of the ankle joint toward the lateral side. The anterior compartment is irrigated and inspected. The next portal to make is the anterolateral portal.

Anterolateral Portal

The anterolateral portal is the second standard anterior portal. In general, it is placed just lateral to the tendon of the peroneus tertius at or slightly proximal to the joint line ( Fig. 18.4 ) and is made under direct vision by introducing a spinal needle. In the horizontal plane, it is situated at the level of the joint line. In the vertical plane, the anterolateral portal is located lateral to the common extensor tendons and the peroneus tertius tendon. Care must be taken to avoid the superficial peroneal nerve because it runs subcutaneously. This subcutaneous nerve often can be palpated or visualized by placing the foot in forced hyperplantarflexion and supination. The intermediate dorsal cutaneous branch of the superficial peroneal nerve crosses the anterior aspect of the ankle joint superficial to the common extensor tendons. Damage to this branch can be avoided by staying lateral to the extensor tendons. Once the lateral branch is identified, its position can be marked with a marking pen on the skin.

It should be noted that the location of the anterolateral portal may vary depending on the location of the lesion in the ankle joint. For the treatment of anteromedial ankle pathology, the anterolateral portal can be placed slightly above the level of the ankle joint and as close to the peroneal tertius tendon as possible. For the treatment of lateral pathology, the anterolateral portal is placed at the level of the joint line and more laterally. After a small skin incision has been made, the subcutaneous layer and capsule are divided bluntly with a mosquito clamp.

Posterior Portals

Posterolateral Portal

The posterolateral portal is made 1.2–2.5 cm proximal to the tip of the lateral malleolus, just lateral to the Achilles tendon ( Fig. 18.5, A ). Both the small saphenous vein and the sural nerve are in close proximity and therefore may be at risk for damage. After making a vertical stab incision, the subcutaneous layer is split by a mosquito clamp. The mosquito clamp is directed anteriorly, pointing in the direction of the interdigital webspace between the first and second toe ( Fig. 18.5, B ). When the tip of the clamp touches the bone, it is exchanged for a 4.5-mm arthroscope shaft with a blunt trocar pointing in the same direction. By palpating the bone in the sagittal plane, the level of the ankle joint and subtalar joint most often can be distinguished because the prominent posterior talar process can be felt as a posterior prominence between both joints. It is not necessary to enter either joint capsule. The blunt trocar is situated extra-articular at the level of the ankle joint. Next, the blunt trocar is exchanged for a 30-degree, 4.0-mm arthroscope. In order to prevent damage to the lens system, the direction of view should be lateral.

Posteromedial Portal

This portal is made second, just medial to the Achilles tendon. In the horizontal plane, it is located at the same level as the posterolateral portal ( Fig. 18.6 ). Care should be taken, since the neurovascular bundle and its branches are at risk. After the skin incision has been made, a mosquito clamp is introduced and directed toward the arthroscope shaft, which already was introduced through the posterolateral portal. When the mosquito clamp touches the shaft of the arthroscope, the shaft is used as a guide to travel anterior in the direction of the ankle joint. All the way, the mosquito clamp must touch the shaft of the arthroscope until the mosquito clamp touches the bone. The arthroscope is pulled slightly backward and slides over the tip of the mosquito clamp until the tip of the mosquito clamp comes to view. The clamp is used to spread the extra-articular soft tissue in front of the tip of the camera and, when present, scar tissue or adhesions; the mosquito clamp is then exchanged for a 5-mm, full-radius shaver.

Transtibial and Tansmalleolar Portals

A transmalleolar portal may be used for debridement and drilling of lesions of the talar dome and is used most often in combination with distraction of the ankle. A special guide facilitates the placement of the portal and the Kirschner wires that are used to drill the defect. Transtibial or transmalleolar drilling with a guiding system is especially useful for tibial plafond lesions. For the treatment of talar dome lesions, the transmalleolar portal has the disadvantage of causing damage to the cartilage of the medial malleolus opposite the osteochondral talar defect and therefore is not recommended to perform on a routine basis.