关键词: 股骨干骨折, 第三骨折块, 微创复位, 周径, 移位程度

Abstract: BACKGROUND: After the treatment of femoral shaft fracture with the intramedullary nail, the third fracture open reduction indications are controversial. Some scholars believe that limited open reduction can achieve anatomical reduction, conducive to fracture healing; but some scholars believe that no open reduction of the third fracture still has a high fracture healing rate.
OBJECTIVE: To investigate the effect of the circumference and displacement of the third fragment on fracture healing after intramedullary nailing of femoral shaft fractures with the third fragment. 
METHODS: A retrospective cohort study was conducted to analyze the clinical data of 142 patients suffered a femoral shaft fracture with a third fragment admitted to the Affiliated Lianyungang Hospital of Xuzhou Medical University from February 2016 to December 2021. The fracture were classified into three types according to the circumference of the third fracture with reference to the diaphyseal circumference at the fracture site: type 1 in 71 cases, type 2 in 52 cases, and type 3 in 19 cases. Referring to the diaphyseal diameter, the fractures were classified into three degrees according to the degree of the third fragment displacement: degree I in 95 cases, degree II in 31 cases, and degree III in 16 cases. All patients were treated with femoral interlocking intramedullary nails, and no intervention was performed for the displaced third fragment during the operation. Postoperative follow-up was performed to compare the fracture healing rate, healing time, and the modified Radiographic Union Scale for Tibia at month 9 after surgery in each group. The effect of third fracture fragment circumference and degree of displacement on fracture healing was assessed. 
RESULTS AND CONCLUSION: (1) All 142 patients were followed up for at least 12 months, with a mean of (14.7±4.1) months, and the overall healing rate was 73.4%. (2) When the third fragment was displaced by degree I, the healing rate, healing time, and modified Radiographic Union Scale for Tibia score at month 9 were not statistically significant among the three sub-groups of circumference classification. (3) When the third fragments were displaced by degree II or III, the healing rate and healing time were not statistically significant among the three subgroups of circumference classification; the modified Radiographic Union Scale for Tibia score at month 9 in the type 1 group was higher than that in the type 2 and 3 groups (P = 0.017). (4) Logistic regression analysis showed that a greater third fragment displacement and circumference were associated with lower fracture healing rates (P < 0.05). (5) These findings indicate that in the treatment of femoral shaft fractures with third fragment by intramedullary nails, when the fracture fragment is displaced to degree I, the circumference size has little effect on fracture healing, and no intervention is required during surgery. When the third fragment is displaced to degree II or III and the circumference of which is type 1, a higher modified Radiographic Union Scale for Tibia score can still be obtained with no intervention of the third fragment. However, when the circumference is of type 2 or type 3, it significantly affects the fracture healing. Consequently, intraoperative intervention to reduce the distance of displacement of the fragment is required to lower the incidence of nonunion. The displacement of the third fracture fragments has a greater impact on fracture healing than their circumference.

Key words: femoral shaft fracture, third fracture fragment, minimally invasive reduction, circumference, displacement degree