Ankle and Hindfoot Injections

Anesthetic injections of the ankle and subtalar joints can be performed under fluoroscopic or computed tomography (CT) guidance. Needle choice is by personal preference. A 22-gauge, 1.5 in needle works well for all of the ankle injections. The author prefers fluoroscopic guidance for the ankle and subtalar joints.

The ankle joint is entered by first marking the desired needle entry location at the medial third of the tibiotalar joint in the anterior projection to avoid the location of the dorsalis pedis artery. This is best accomplished using a vertical mark with an indelible marker. The skin entry site is then determined in the lateral projection where the exact location of the anterior margin of the tibiotalar joint can be visualized rather than the talar dome, which is visualized in the anterior projection (9). A horizontal skin mark is made, which will intersect the vertical line previously drawn, indicating the exact point of skin entry (Fig. 3). The test injection with a water-soluble contrast material is then performed in the lateral projection (Fig. 4). Reasonable injection volume is 10 to 12 cc.

The posterior subtalar joint can be entered with fluoroscopic guidance. Difficult cases such as patients suffering from advanced osteoarthrosis of the hind foot may benefit from CT guidance. For fluoroscopic guidance, the patient is positioned with the contralateral side down

FIGURE 3 Intersecting vertical and horizontal skin markings depicting the needle entry site for ankle injection, based on location of medial third of joint from pulmonary artery fluoroscopy and anterior margin of joint from lateral fluoroscopy, respectively.

and the ankle of interest positioned medial side down (Fig. 5). The desired approach to the posterior subtalar joint is from the lateral aspect of the ankle anterior or posterior to the lateral malleolus (Fig. 6) (10). Abnormal communication between tarsal compartments should be noted because the passage of anesthetic into adjacent compartments can lead to diagnostic uncertainty, that is, communication between the posterior subtalar and ankle joints, which occurs in roughly 10% of patients (Fig. 6).

Due to its communication with the talonavicular joint, the anterior subtalar joint is readily accessible from a medial approach under fluoroscopic guidance with patient supine and foot placed lateral side down (Figs. 7 and 8). Significant navicular curvature requires an oblique

FIGURE 4 Lateral fluoroscopic image during ankle injection. Source: Courtesy of Guerdon Greenway M.D., Baylor University Medical Center, Dallas, Texas, U.S.A.
FIGURE 5 Patient positioning for posterior subtalar injection. Source: Courtesy of Drew Small M.D., Baylor University Medical Center, Dallas, Texas, U.S.A.

FIGURE 6 Lateral fluoroscopic image demonstrating the posterolateral approach to the posterior subtalar joint. Note the passage of contrast into the ankle joint, which occurs in 10% of patients.

FIGURE 7 Patient positioning for anterior subtalar (talonavicular) injection.

FIGURE 6 Lateral fluoroscopic image demonstrating the posterolateral approach to the posterior subtalar joint. Note the passage of contrast into the ankle joint, which occurs in 10% of patients.

FIGURE 7 Patient positioning for anterior subtalar (talonavicular) injection.

FIGURE 8 Lateral fluoroscopic image during talonavicular joint injection with expected opacification of the anterior subtalar joint.

needle path, as shown on this PA fluoroscopic image (Fig. 9). A dorsal approach to the talonavicular joint can be used but is often difficult due to dorsal osteophyte formation.

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