Vascular Anatomy of the Medial Femoral Neck and Implications for Surface Plate Fixation

OBJECTIVES: To describe the inferior retinacular artery (IRA) as encountered from an anterior approach, to define its intraarticular position, and to define a safe zone for buttress plate fixation of femoral neck fractures. METHODS: Thirty hips (15 fresh cadavers) were dissected through an anterior (Modified Smith-Petersen) approach after common femoral artery injection (India ink, blue latex). The origin of the IRA from the medial femoral circumflex artery and the course to its terminus were dissected. The IRA position relative to the femoral neck was described using a clock-face system: 12:00 cephalad, 3:00 anterior, 6:00 caudad, and 9:00 posterior. RESULTS: The IRA originated from the medial femoral circumflex artery and traveled within the Weitbrecht ligament in all hips. The IRA positions were 7:00 (n = 13), 7:30 (n = 15), and 8:00 (n = 2). The IRA was 0:30 anterior to (n = 24) or at the same clock-face position (n = 6) as the lesser trochanter. The mean intraarticular length was 20.4 mm (range 11-65, SD 9.1), and the mean extraarticular length was 20.5 mm (range 12-31, SD 5.1). CONCLUSIONS: The intraarticular course of the IRA lies within the Weitbrecht ligament between the femoral neck clock-face positions of 7:00 and 8:00. A medial buttress plate positioned at 6:00 along the femoral neck is anterior to the location of the IRA and does not endanger the blood supply of the femoral head. The improved understanding of the IRA course will facilitate preservation during intraarticular approaches to the femoral neck and head.