1, Objective To investigate the clinical application and efficacy of the expandable PF intramedullary nail (PFN) in the treatment of rotor fractures of the femur in the elderly. 2.Methods From June 2004 to October 2005, 34 elderly patients with femoral rotor fractures were fixed with expandable PFN, and the fractures were classified according to Evans’ type: 4 cases of type II, 6 cases of type IIIA, 8 cases of type IIIB, and 16 cases of type IV; 2 of them were combined with femoral stem fractures. 3. Results Thirty-four patients were followed up for 8 to 52 weeks (mean 25 weeks). All fractures healed with a healing time of 8 to 20 weeks, with a mean of 12 weeks. There were no complications such as infection, fat embolism, deep vein thrombosis, non-healing fracture, hip inversion and rotational deformity. 4.Conclusion Expandable PFN treatment of femoral rotor fracture has the advantages of simple operation, small trauma, consistent with the principle of biological fixation, stable fracture fixation, early release of the patient from bed for weight-bearing and few complications, which is especially suitable for elderly patients. 5.Surgical method Continuous epidural anesthesia or general anesthesia is used, and the patient is placed on an orthopedic traction bed with the healthy limb flexed at the hip and knee and abducted, and the affected limb is straightened and adducted to make the greater trochanter protrude as much as possible. A C-arm X-ray machine is placed between both lower limbs to obtain good frontal and lateral fluoroscopic images. The fracture was repositioned by traction and internal rotation of the affected limb, and a 5 cm long incision was made from the tip of the greater trochanter to the proximal end, with a trigon opening 0.5 cm medially from the tip of the trochanter toward the medullary cavity of the femur. The expandable PFN mounted on the sighting handle was inserted into the proximal medullary cavity of the femur with force, and the anterior tilt angle was adjusted after the depth was suitable. Remove the drill and the guide pin, place the femoral head peg, pump saline to 1/4 of the pressure pump lumen, drain the gas from the pressure pump, and inject saline into the peg until the pressure stabilizes at 120 Bar (1 Bar = 105 Pa) and the head of the femoral head peg expands to an olive shape on fluoroscopy. The pressure was gradually increased to 70 Bar, and the nail stem was significantly expanded, the transverse spokes were in close contact with the wall of the medullary cavity, and the original lateral displacement of the fracture was completely reset. A locking screwdriver is inserted into the connecting sleeve at the end of the femoral intramedullary nail, and the 360° cis-rotation locking femoral peg sliding restrictor prevents its rotation and withdrawal. To enhance resistance to rotation, an additional reinforcing nail can be screwed into the femoral neck through the proximal locking hole of the sight. The pressure pump and sighting device are removed, the sealing cap on the caudal end of the intramedullary nail is tightened, and the incision is closed after flushing. 6. Postoperative treatment Postoperatively, wear anti-rotation shoes and start doing active muscle contraction exercises the next day, and practice hip and knee flexion and extension functions after the pain response ends in 3 d. Patients with inter-rotator fractures should start partial weight-bearing on the affected limb at 3 weeks and complete weight-bearing at 6 weeks. Weight-bearing was started at 10 weeks for Evans type IV, subrotor fractures and combined femoral stem fractures. After discharge from the hospital, patients were reviewed once a month and X-ray films were taken for fracture healing. Clinical healing of the fracture was determined if there was no pain on weight-bearing, no local percussion, good scab growth on X-ray, and faint fracture line.