Safe extracapsular placement of proximal tibia transfixation pins.

OBJECTIVE: To identify the anatomic detail of the knee joint capsular insertion site on the proximal tibia, specifically as it relates to transfixation pins. DESIGN: Identification of capsular anatomy by anatomical dissection of cadaveric specimens, with radiography and arthroscopy of patients. SETTING: Cadaveric dissection. OUTCOME MEASURES: Anatomic observation of the capsular attachment site in relation to the tibial articular surface. RESULTS: The capsule inserts four to fourteen millimeters below the articular surface in a regular pattern. The anterior half of the circumference is close to the joint line (less than six millimeters). Posteromedially and posterolaterally, there are extensions distally to fourteen millimeters, occasionally communicating with the tibiofibular joint. CONCLUSION: Transfixing wires and half-pins can be placed in the proximal tibia without capsular penetration if kept more than fourteen millimeters from the subchondral line. If wire placement closer to the joint is required, wires should be placed in Zone 1 (the anterior half) and at least six millimeters from subchondral bone to avoid capsular penetration.