Abstract: BACKGROUND: How to achieve satisfactory reduction quickly, minimally invasively and effectively is difficult in the operation of irreducible intertrochanteric femoral fracture. Fracture classification helps to formulate a reasonable reduction plan before surgery, but a simple and feasible classification of irreducible intertrochanteric femoral fracture is still lacking currently.  
OBJECTIVE: To explore the classification and reduction strategy of irreducible intertrochanteric femoral fracture based on anatomy.
METHODS:  The clinical data of 531 patients with irreducible intertrochanteric fracture treated in Sichuan Academy of Medical Sciences & Sichuan Provincial People’s Hospital from June 2006 to May 2020 were analyzed retrospectively, including 187 males and 344 females, at the age of 60-101 years old. According to whether the greater trochanter/lesser trochanter was connected to the proximal end of the fracture, the irreducible intertrochanteric fractures were divided into type I (proximal free), type II (greater trochanter connected), type III (lesser trochanter connected), and type IV (both greater and lesser trochanters connected). Periosteum stripper, hemostatic forceps and/or bone hook were used to assist the reduction, and InterTan or proximal femoral nail anti-rotation was used for internal fixation. X-ray films were taken during postoperative follow-up to assess the quality of fracture reduction and fracture healing. At the last follow-up, the patient’s hip function recovery was assessed by Harris score.  
RESULTS AND CONCLUSION: (1) Among the 531 cases of irreducible femoral intertrochanteric fractures, the types I, II, III, and IV were 357, 87, 13, and 74 cases respectively, and 489 cases (92.1%) achieved satisfactory reduction. (2) Of the 531 patients, 26 were lost to follow-up, and 23 died of pneumonia, heart failure and other causes before the fracture healing. 482 patients were followed up for more than one year, and all fractures healed with an average time of 4.7 months. (3) During the postoperative follow-up, there was no adverse event related to internal fixation materials. (4) At the last follow-up, the Harris score of 482 patients was 95.7±4.8, of which 433 cases (89.8%) had excellent evaluation results. (5) These results confirm that for irreducible intertrochanteric fractures, satisfactory reduction and hip joint function can be obtained by adopting our classification and reduction techniques.

Key words: intertrochanteric fracture, reduction, greater trochanter, lesser trochanter, classification, internal fixation, proximal femoral nail anti-rotation