Incidence of Intracapsular Placement When Inserting Medial Talar Body Schanz Pins: An Anatomic Study

Medial talar body pins may be inserted to provide points of fixation in the hindfoot when applying external fixators. Because of the proximity to the ankle joint, there is a risk of intracapsular pin placement. We hypothesized that intracapsular placement is common when inserting medial talar body pins.

Medial talar body pins were inserted in 12 fresh frozen cadaver ankles. Arthrography of each ankle was then performed to determine whether the pin was intracapsular. Each pin was then removed, and fluoroscopy was repeated to evaluate for contrast extravasation from the pin insertion site. The distance from the apex of the talar head to the anterior extent of the ankle capsule was measured to determine a safe area for extracapsular pin placement.

Arthrograms of all 12 ankles demonstrated that the pins were intracapsular. After pin removal, there was contrast extravasation from the pin insertion site in all specimens. Contrast was present in the pin tract in all specimens. Mean distance from the talar head to the anterior ankle capsule was 20.95 ± 4.8 mm (range, 12.2-27.3 mm) on the lateral view and 15.5 ± 1.8 mm (range, 12.4-20.0 mm) on the anteroposterior view of the foot.

There is a high rate of intracapsular pin placement when inserting medial talar body pins. Pin placement within the joint capsule risks seeding a sterile joint with bacteria and fistula formation when the pin remains in place for prolonged periods. For this reason, talar body pins should be avoided in temporizing external fixation frames.