Objective To evaluate the effect of ultrasound-guided K-wire reduction of irreducible femoral neck fractures.Methods A retrospective analysis was made on 21 patients with irreducible femoral neck fractures hospitalized from January 2011 to January 2014.There were 13 males and 8 females,aged 23-60 years (mean,41.5 years).The fractures of nine patients were caused by road traffic accidents,seven by slipping,and five by fall from the height.According to the Garden classification,four patients were classified as type Ⅱ,eleven type Ⅲ,and six type Ⅳ.Patients were placed in traction bed for limb traction.After 3-times unsuccessful reduction with limb traction,the patients were performed ultrasound-guided localization of superficial femoral artery,vein and nerve in the hip,marked and stabilized with two K-wires into the surface markers.Position relations of femoral artery,vein and nerve with the femoral head were determined under fluoroscopic guidance.After operation,the part with K-wire insertion was routinely reviewed by ultrasound,the anterior and lateral positions of the hip joint were routinely reviewed,and the sensorimotor function of the area of femoral nerve and sense function of the anterolateral femoral cutaneous nerve were routinely examined.Quality of reduction was assessed with the Garden index.Hip function was assessed with Harris score.Results All patients were followed up for mean 18 months (range,6-28 months),which showed satisfactory reduction.No major vascular or nerve injury occurred intraoperatively.Postoperative ultrasound examination revealed no local hematoma formation,normal functions of the femoral nerve and normal superficial sensibility of the anterolateral femoral cutaneous nerve.No deep vein thrombosis of the lower limb occurred postoperatively.According to the Garden index,reduction was reached grade Ⅰ in fourteen patients and grade Ⅱ in seven patients.Harris hip score was excellent in 14 patients,good in six and poor in one,with the excellent-good rate of 95％.One patient underwent total hip arthroplasty for the postoperative femoral head necrosis,and none had screw displacement and implant loosening.Conclusion Ultrasound guided K-wire reduction of irreducible femoral neck fractures is associated with simple equipment,high repeatability,safe and effective results,and decreased iatrogenic injury.