Analysis of the influence of circumference and displacement of the third fracture fragment on the healing of femoral shaft fractures treated with intramedullary nailing
Authors: Yin Zhaoyang , Yang Shuo , Yu Jian , Chen Shuchang , Feng Tao , Huo Yongfeng , Yin Jian , Zhang Yanyan 
Published: January 2024

To investigate the effect of circumference and displacement of the third fracture fragments on fracture healing after intramedullary nailing of femoral shaft fractures with third fracture fragment. A retrospective cohort study was conducted to analyze the data of 142 patients suffered femoral shaft fractures with the third fracture fragments admitted to the First People's Hospital of Lianyungang from February 2016 to December 2021, among whom there were 88 males and 54 females, with an average age of 42.2 years; 81 cases with right side and 61 cases on the left side; 78 cases of isthmic fractures and 64 cases of non-isthmic fractures. The time from injury to operation was (4.3 ± 3.3) days. According to the circumference of the third fracture fragments, the fracture fragments were divided into 3 types: type 1: the circumference of the third fracture fragments was less than 1/3 of the diaphyseal circumference at the fracture site in 71 cases; type 2: the circumference of the third fracture fragments was greater than 1/3 of the diaphyseal circumference at the fracture site and less than 2/3 of the diaphyseal circumference in 52 cases; type 3: the circumference of the third fracture fragments was greater than 2/3 of the diaphyseal circumference at the fracture site in 19 cases. Based on the diaphyseal diameter, the degree of displacement of the third fracture fragment was classified into three degrees: degree I: third fracture fragment displacement was less than 1/3 of the diaphyseal diameter at the fracture site in 95 cases; degree II: third fracture fragment displacement was greater than 1/3 of the diaphyseal diameter at the fracture site while less than 2/3 of the diaphyseal diameter at the fracture site in 31 cases; degree III: third fracture fragment displacement was greater than 2/3 of the diaphyseal diameter at the fracture site in 16 cases. All patients underwent closed reduction and intramedullary nailing of femoral fractures, and no intervention was performed for displaced third fragments during surgery. Postoperative follow-up was performed to compare the fracture healing rate, healing time, and the modified Radiographic Union Scale for Tibia (mRUST) at 9th month after surgery in each group. All 142 patients were followed up after operation, with an average of (14.7 ± 4.1) months, and the overall healing rate was 73.4%. When the third fracture fragment was displaced in degree I, the healing rates were 98.1%, 90.3%, and 90.0% (P = 0.375), the healing times were (8.7 ± 0.8) months, (9.0 ± 0.7) months, and (9.4 ± 0.9) months (P = 0.054), and the mRUST at 9th month were (13.1 ± 1.5), (12.9 ± 1.9), and (12.5 ± 1.5) (P = 0.552) among the three subgroups of circumference classification, respectively, without statistical significance. When the third fracture fragments were displaced in degree II and III, the healing rates were 52.9%, 23.8%, and 11.1% (P = 0.053) and the healing time was (8.9 ± 1.1) months, (10.8 ± 2.5) months, and (12.0 ± 0.0) months (P = 0.097) among the three subgroups of circumference classification, respectively, without statistical significance; the mRUST score at 9th month in the type 1 group (11.6 ± 2.9) was higher than that in the type 2 group (9.3 ± 2.1) and the type 3 group (8.8 ± 1.6) (P = 0.017). Logistic regression analysis showed that greater displacement of third fracture fragments and greater circumference were associated with lower fracture healing rates (P < 0.05). In the treatment of femoral shaft fractures with 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 fracture fragment is displaced to degree II and III and the circumference of which is type 1, no intervention of the third fracture fragment can also obtain a higher mRUST score; whereas, provided that the circumference of which is type 2 or type 3, it significantly affects the fracture healing. Intraoperative intervention to reduce the distance of displacement of the fragment is required to reduce the incidence of nonunion. The displacement of third fracture fragments has a greater impact on fracture healing than its circumference.