Objective:To evaluate natural reduction at prone position in the treatment of femoral subtrochanteric fractures with intramedullary nailing.Methods:The clinical data of 7 patients with subtrochanteric fracture were retrospectively analyzed who had been treated at Orthopaedic Department, Beijing Tsinghua Changgung Hospital from August 2016 to April 2018. They were 4 males and 3 females, aged from 31 to 87 years (average, 55.6 years). Their fractures happened on the left side in 3 patients and on the right side in 4. By the Seinsheimer classification, there were 3 cases of type Ⅱ, 2 cases of type Ⅲ and 2 cases of type Ⅴ. The time from injury to surgery ranged from 9 to 44 hours, averaging 26 hours. All patients were treated by intramedullary nailing after natural reduction at prone position. Their preoperative preparation time, time required for reduction, total operation time, fluoroscopic frequency for guide pin insertion, fluoroscopic frequency for reduction, reduction quality, complications and curative effect were recorded.Results:Closed reduction and intramedullary nail fixation were completed uneventfully in all the 7 cases. Their preoperative preparation time averaged 29.4 min (from 21 to 42 min), reduction time 6.3 min (from 3 to 10 min), and total operation time 157 min (from 82 to 275 min). Their fluoroscopic frequency averaged 37 times (from 14 to 96 times) for guide pin insertion and 23 times (from 10 to 49 times) for reduction, totaling 244 times (from 121 to 360 times). According to the modified Baumgaetner criteria, the fracture reduction was evaluated as excellent in 6 cases and as fair in one. The 7 patients were followed up for 12 to 34 months (mean, 20.1 months). A drill broke at the interlocking nail hole during operation in one patient, deep venous thrombosis occurred at a lower extremity in another during hospitalization, and fracture nonunion was observed after operation in another, but no complications related to the prone position were observed. The curative effect evaluated by Harris hip score at the last follow-up was excellent in 4 cases, as good in 2 cases and as fair in one.Conclusion:In the treatment of femoral subtrochanteric fractures with intramedullary nailing, the prone position benefits natural reduction and maintenance of reduction and allows convenient fluoroscopy and nail placement during operation, especially for obese patients.