Retrospective evaluation of factors affecting fracture healing after intramedullary nail application in femoral shaft fractures

The intramedullary nail application for femoral shaft fractures provides a mechanically and biologically advantageous environment to support the proper healing of the fracture. This method allows micro-mobility at the fracture site while providing continuous internal fixation between the distal and proximal ends of the fracture, emphasizing the importance of achieving optimal fit between the patient's bone structure and the implant to stabilize the fracture. This single-center retrospective study aims to evaluate the factors that influence fracture healing after intramedullary nail osteosynthesis in femoral shaft fractures. The main focus of the research is to determine the optimal size relationship that can positively affect the fracture healing between the femoral isthmus diameter and the intramedullary nail diameter. For this purpose, the medical records of 421 patients with femoral fractures treated at the Orthopedics and Traumatology Clinic of Akdeniz University Hospital between January 2014 and January 2021 were examined. Intramedullary nails were applied to 274 of these patients. Forty-one patients who did not meet the study criteria were excluded, and 46 out of 223 patients with 233 femoral shaft fractures were excluded from the study due to irregular follow-up. As a result, 177 patients with 187 femoral shaft fractures formed the study group. The nail diameter/isthmus diameter ratio was determined for all cases. X-rays taken at 3, 6, 9, and 12 months for the patients were separately analyzed, RUSF scoring was performed, and the fracture healing was evaluated. Univariate and multivariate statistical evaluations were conducted to determine the impact of other potential factors (demographic characteristics, clinical findings, postoperative radiological measurements) on fracture healing. When evaluating the effect of the ratio between nail diameter and isthmus diameter on healing, a ROC analysis was performed on fractures that corresponded to radiological healing values at the 6-month mark, and the cutoff value for the measurements was determined to be 0.89. This value was found at a 54% consistency level, with a sensitivity level of 60% and a specificity level of around 50%, and no statistically significant relationship was found with fracture healing. When examining other parameters, it was determined that fracture healing was significantly higher in young patients,in males compared to females. The commonly used Winquist-Hansen and AO/OTA classifications for femoral shaft fractures were evaluated, and it was observed that fracture healing significantly increased in stable fractures (0-1-2) compared to unstable fractures (3-4) when assessed according to the Winquist-Hansen classification. When evaluated according to the AO/OTA classification, it was observed that being in class A3 in Group A and in class B2 in Group B statistically increased fracture healing. When all groups were evaluated together in the AO/OTA classification, being in class B1 and B2 increased the likelihood of healing compared to being in class A1. It was observed that open fractures showed longer radiological healing term compared to closed fractures. Smoking was found to have negative effects on fracture healing, while alcohol use did not have a significant impact. Having a high ASA and BMI score or the presence of diabetes did not show a significant effect on fracture healing. When examined according to the reduction technique, it was observed that closed reduction, where the fracture site did not open, significantly increased fracture healing compared to open reduction. Key Words: Femoral shaft fracture, intramedullary nail, fracture healing.