"Fragment Width Ratio" as a Predictor of Nonunion for Femoral Shaft Fracture With Third Fragments

Previous studies have reported that large fracture fragment with displacement might cause nonunion of femoral shaft fractures. We therefore intended to delineate significant risk factors for developing a nonunion predisposed by a major fracture fragment. We analyzed 61 patients who were operated on using interlocking nails for femoral shaft fractures from 2009 to 2018. We classified patients with modified Radiographic Union Scale for Tibia fractures scores of less than 11 or needing reoperations by 1 year postoperatively as nonunion. We thereafter measured parameters of the displaced fracture fragment and fracture site to identify the significant difference between the union and non-union groups. We also applied the receiver operating characteristic curve to demonstrate a threshold value for the fragment width (FW) ratio. Among 61 patients with complete follow-up, no significant difference was found regarding length, displacement, and angulation of fragments between patients with and without union. Except for higher mean FW (P=.03) and the FW ratio (P=.01) in patients with nonunion, the logistic regression analysis demonstrated that FW ratio significantly affected union (P=.018; odds ratio, 0.21; 95% CI, 0.001-0.522). Although a fracture fragment greater than 4 cm with displacement greater than 2 cm was reported to significantly cause nonunions, our study showed that an FW ratio greater than 0.55 instead of fragment size or displacement was predictive for the occurrence of nonunion adjoining to the fracture site. Fixation of the third fracture fragment should not be ignored for preventing a nonunion. More attention should be paid to achieve a better fixation for a major fracture fragment with an FW ratio greater than 0.55 to avoid the development of non-union following the use of interlocking nail for femoral shaft fracture. [Orthopedics. 2023;46(3):169-174.].