Effect of the degree of displacement of the third fragment on healing of femoral shaft fracture treated by intramedullary nailing

Objective To investigate the effect of the degree of displacement of a femoral shaft fracture with the third fragment on fracture healing after intramedullary nailing. Methods In total, 216 patients with closed comminuted femoral fracture admitted to Lianyungang Hospital affiliated to Xuzhou Medical University from February 2010 to February 2016 were analyzed retrospectively. Among these patients, 142 were males and 74 were females, the mean age was 38 years (range 17–64 years), and 95 cases were on the right, while 121 cases were on the left. All patients were treated with a femoral interlocking intramedullary nail. Referring to the femoral shaft diameter, the degree of displacement of the third fragment was classified into four grades: grade I (displacement was less than a third of the diameter of the shaft): 121 cases; grade II (greater than a third of the diameter and less than two thirds): 52 cases; grade III (greater than two thirds of the diameter): 28 cases; and grade IV (fracture fragment turnover): 15 cases. According to the modified Radiological Union Scale for Femur (mRUSF), the fracture union rate and the mean union time of the fracture, the effect of the degree of displacement of the third fragment on fracture healing was evaluated. Results In total, 216 patients with a mean follow-up of 15.9 months (range 6–31 months) met the inclusion criteria. The best fracture healing was the grade I displacement, with a union rate of 89.2% and a mean union time of 7.7 months. The poorest fracture healing was for the grade IV displacement, with a union rate of 13.3% and a mean union time of 16.5 months. The healing was moderate in the grade II and III displacements, with a union rate of 46.2% and 28.6%, respectively, and a mean union time of 8.6 months and 13.5 months, respectively ( P < 0.05). Conclusions The third fragment with grade I displacement requires no intervention, whereas fractures with grade IV displacement should be reduced to as near as possible to the diaphyseal bone defect to avoid nonunion. The third fragments with the grade II or III displacement should be treated with closed reduction whenever possible to achieve a displacement within the range of grade I to minimize the incidence of nonunion.