Minimizing the Risk of Vascular Injury: Anatomy of the Popliteal Artery in the Pediatric Knee.

ABSTRACT

BACKGROUND: Displaced pediatric tibial tubercle fractures are commonly stabilized with screws directed posteriorly toward neurovascular structures. Here, we (1) characterize the variation of the popliteal artery among pediatric patients; and (2) recommend a safe screw trajectory for fixation of tibial tubercle fractures. METHODS: We retrospectively identified 42 patients (42 knees; 29 female) aged 12-17 years with lower-extremity magnetic resonance imaging (MRI) at a tertiary academic center. The mean patient age was 14.5 (range 12-17) years, and the mean body mass index value was 19.1 (range 14.9-25.1). We included patients with open physes or visible physeal scars and excluded those with prior instrumentation or lower-extremity injury. Using sagittal MRI, we measured the distances from 5 levels each on the anterior and posterior tibial cortex to the popliteal artery (level 1, midpoint of proximal tibial epiphysis; level 2, the proximal extent of the tubercle; level 3, tubercle prominence; level 4, 2 cm distal to the proximal extent of the tubercle; level 5, 4 cm distal to the proximal extent of the tubercle). Using coronal MRI, we measured the width of the tibia at each level and the distance from the lateral-most and medial-most cortex to the artery. RESULTS: The popliteal artery was laterally positioned in all knees. The mean distance between the artery and lateral-most aspect of the tibia at each level ranged from 1.9 to 2.4 cm, and from 2.3 to 3.9 cm from the medial-most aspect of the tibia. The mean distance that a screw can advance before vascular injury was 5.1 cm at level 1. The shortest mean distance to the popliteal artery was 1.7 cm, at level 5. There is minimal distance between the posterior tibial cortex and the artery at all levels. CONCLUSIONS: Understanding the position of the popliteal artery in pediatric patients can help when stabilizing tibial tubercle fractures. Because the artery is close to the posterior cortex, a drill exiting in line with the popliteal artery risks vascular injury. Therefore, we recommend that screws exit within the medial 60% of the tibia. LEVEL OF EVIDENCE IV.