BACKGROUND:Hidden blood loss is an important risk for the intertrochanteric fracture patients, especial y the elderly patients, which can cause anemia in patients after internal fixation and can affect wound healing and patient recovery. OBJECTIVE:To compare the perioperative hidden blood loss and the risk factors of proximal femoral anti-rotation intramedul ary nail internal fixation and dynamic hip screw fixation for the treatment of femoral intertrochanteric fracture. METHODS:We selected 70 cases of femoral intertrochanteric fracture patients who treated with proximal femoral anti-rotation intramedul ary nail and dynamic hip screw fixation, including 21 patients with the age ≥ 80 years and 49 patients with the age30 kg/m2 and 42 patients with the body mass index ≤ 30 kg/m2;30 patients received anti-rotation intramedul ary nail internal fixation and 40 patients received dynamic hip screw fixation. The perioperative blood loss was calculated with Gross formula according to the changes of height, body mass index and the hematocrit before and after fixation. RESULTS AND CONCLUSION:The mean total blood loss was 936 mL, the mean dominant blood loss was 237 mL and the mean hidden blood loss was 699 mL. The hidden blood loss was accounted for 74.7%in total blood loss. The dominant blood loss in the dynamic hip screw fixation group was higher than that in the anti-rotation intramedul ary nail internal fixation group, and the hidden blood loss was lower than the anti-rotation intramedul ary nail internal fixation group. The total blood loss and the hidden blood loss of the elderly patients were higher than those of the non-elderly patients;there was no significant difference between male and female patients, obesity and normal patients. The results indicate that hidden blood loss is the major reason for total blood loss of femoral intertrochanteric fracture after internal fixation. The hidden blood loss of anti-rotation intramedul ary nail internal fixation is larger than that of dynamic hip screw fixation, and elder is the risk factor for hidden blood loss.