Extracapsular placement of distal tibial transfixation wires

Abstract

Background: Treatment of tibial plafond fractures with external fixation may involve use of transfixation wires within the periarticular region. Pin track infections that develop along wires placed intracapsularly may lead to joint infection. To our knowledge, there have been no previous investigations assessing the circumferential reflection of the ankle capsule or the potential for communication between the distal tibiofibular joint and the tibiotalar joint. The purpose of this study was to define these anatomic entities to provide guidelines for safe extracapsular placement of distal tibial wires.

Methods: Twelve fresh-frozen cadaveric ankles and three ankles of living human volunteers were utilized for this study. High-resolution magnetic resonance imaging was performed on each ankle after pressurized distention of the joint capsule with gadolinium solution. The perpendicular distance from the subchondral bone at the joint line to the capsular synovial reflection was measured with use of a verified technique. The cadaveric ankles were sectioned, the capsular synovial reflections were measured by investigators who were blinded to the imaging results, and the corresponding measurements were compared.

Results: The anterolateral capsular synovial region displayed the most proximal reflection in all specimens (mean, 9.3 mm; maximum, 12.2 mm). The anteromedial region displayed less reflection (mean, 3.3 mm; maximum, 5.5 mm). All posteromedial and posterolateral synovial reflections were <or=2 mm. Capsular synovial reflections proximal to the medial and lateral malleoli were negligible. In all ankles, the distal tibiofibular joint communicated with the tibiotalar joint and had a maximum proximal extension of 20.6 mm.

Conclusions: Placement of distal tibial transfixation wires >12.2 mm from the subchondral surface of the plafond avoids penetration of the capsule. The distal tibiofibular joint communicates with the tibiotalar joint and thus should not be penetrated, to ensure extracapsular placement of the wires.