CHAPTER 4 Diagnostic Arthroscopy for the Ankle and Subtalar Joints

The ankle is a highly constrained joint composed of complex, curved articular surfaces that are stabilized by ligaments with various degrees of laxity. These anatomic constraints make arthroscopy of the ankle joint more difficult than in larger joints such as the knee and shoulder. Early attempts to perform arthroscopy of the ankle joint were met with various degrees of success. In a 1931 cadaver study, Burman suggested that the ankle joint “… is not suitable for arthroscopy.”¹

Arthroscopists in the 1980s began to apply modern techniques to instrumentation of the ankle and defined the basic portals with which to approach the joint.²^–⁴ Since then, two technical advances have facilitated routine performance of ankle arthroscopy for diagnosis and surgical procedures. First, the development of high-quality, small-diameter arthroscopes has allowed instrumentation of the ankle with increased ability to visualize the entire joint while decreasing the likelihood of iatrogenic articular cartilage injury. Second, techniques have been developed for noninvasive joint distraction to facilitate instrument passage and decrease joint injury.⁵ Without distraction, it is often impossible to visualize the central and posterior compartments of the joint from the anterior portals. Early attempts to distract the joint used pins placed into the tibia and calcaneus that were connected to a distractor device similar to an external fixator. The use of these devices was associated with significant complications, including pin tract infection and neurovascular injury.⁶ Elimination of these complications while effectively distracting the joint with noninvasive strap distraction is a major advantage, and invasive ankle joint distraction is no longer recommended.

PATIENT POSITIONING

The patient is placed supine on the operating table with the hip and knee flexed and supported by a well-padded leg holder (Fig. 4-1). I prefer a leg holder with a long thigh segment and short knee segment to diffuse the distraction force over the wide area of the thigh rather than concentrating the force in the popliteal space and potentially causing obstruction to venous outflow. Sterile drapes are applied after skin preparation.

FIGURE 4-1 Position for ankle arthroscopy. The patient is supine, and the hip and knee are supported by a well-padded leg holder. The leg holder has a broad thigh support so that as distraction force is applied to the ankle, it is dissipated over a wide area of the thigh rather than concentrated in the popliteal fossa.

A sterile clamp is attached to the operating table side rail over the sheets, and a bar is fixed to the clamp. The noninvasive ankle distractor strap is placed around the hindfoot and midfoot and connected to the bar using a segment of sterile two-sided Velcro. This distraction setup allows the ankle and foot to rest in a plantigrade position while retaining the ability to move the ankle in dorsiflexion and plantar flexion intraoperatively (Fig. 4-2).

FIGURE 4-2 The leg is prepared and draped with sterile sheets, and the noninvasive distractor is applied to the ankle. The strap that is placed around the hindfoot and midfoot is attached to the bar using a strip of Velcro, with which the distraction force can be varied.

Invasive distraction is not required for standard ankle arthroscopy. It poses unnecessary risks to neurovascular structures, along with risks of infection and stress fracture.

Anatomic landmarks are then marked with a sterile marking pen. I outline the medial malleolus and the anterior joint line along with the contour of the distal fibula. Also marked are the position of the tibialis anterior tendon medially, the peroneus tertius tendon laterally, and the lateral border of the Achilles tendon posteriorly. The position of the superficial peroneal nerve branch passing over the anterolateral ankle can often be appreciated by plantar flexing and inverting the ankle.

PEARLS& PITFALLS

PEARLS

• Noninvasive ankle distraction assists in exposure of the entire ankle joint for arthroscopy.

• Small joint arthroscopes with a 2.7-mm diameter and with 30- and 70-degree viewing angles provide the best visualization.

PORTAL CREATION

Careful attention to portal creation technique can minimize the incidence of iatrogenic injury to neurovascular structures. The nick and spread technique is advised. Each portal is created by incising only the skin, avoiding penetration of the subcutaneous tissues with the knife blade. A small hemostat clamp is used to spread the subcutaneous tissues down to the level of the capsule. The capsule is penetrated using a blunt trocar to minimize the risk of iatrogenic articular cartilage injury.

The three standard working portals for ankle arthroscopy are the anteromedial portal, the anterolateral portal, and the posterolateral portal (Fig. 4-3). The anterocentral portal was used in the early days of ankle arthroscopy because of the purported benefit of increased visualization in the central compartment. However, this portal placement poses significant risk of injury to the deep peroneal nerve and the dorsalis pedis artery. The use of small joint arthroscopes and noninvasive joint distraction obviates the use of this portal for ankle arthroscopy.