OTA 1999 Posters

Soft-Tissue Injuries with the Use of "Safe" Corridors for Transfixion Wire Placement During External Fixation of Distal Tibia Fractures - An Anatomic Study

Michael J. Vives, MD; Nicholas A. Abidi; Susan N. Ishikawa, MD; Rajiv V. Taliwal, MD; Peter F. Sharkey, MD, The Rothman Institute, Jefferson Medical College, Philadelphia, PA

Safe corridors for pin insertion in the lower leg above the ankle have been described for small tensioned-wire external fixators. The purpose of this study was to determine what soft tissue structures remain at risk during pin placement while adhering to published guidelines.

Five freshly embalmed cadaver legs were marked to simulate a distal tibia fracture five cm above the ankle. Four surgeons were shown diagrams that have been widely reproduced as guidelines for safe pin placement. Each surgeon was then asked to place two transfixion pins into each leg in a position to provide stable external fixation of the metaphysis to the diaphysis with a circular fixator (forty pins total). The specimens were dissected and pins impaling neurovascular structures, tendons or the ankle capsule were recorded. The superior capsular synovial reflections were measured >from the anterior joint line and the tip of the medial malleolus. These measurements were also performed on arthrograms of two extremities prior to their dissection.

Fifty-five percent of the pins placed impaled at least one tendon that crosses the ankle joint. The extensor digitorum communis tendon was impaled by 20 percent of the pins (eight out of forty total pins). Other commonly injured tendons were the peroneus longus, anterior and posterior tibial tendons (7.5 percent) and the extensor hallucis longus tendon (5 percent). Neurovascular structures that were impaled included the saphenous vein (10.5 percent) and the superficial peroneal nerve (7.5 percent). One pin violated the superior capsular synovial reflection, which was an average of thirty-two mm (± 1.58 mm) from the tip of the medial malleolus and twenty-one mm (±1.63 mm) from the anteromedial joint line.

This study demonstrates that tendons and neurovascular structures above the ankle are at risk during small pin placement, even while utilizing safe corridors. Pins placed within two cm of the anterior joint line or three cm from the medial malleolus may be intracapsular.