Risk factors associated with transport gap bending deformity after bone transport in the treatment of lower extremity bone defects caused by infection

Abstract Background: The objective of this study was to observe the efficacy of bone transport using Orthofix external fixator in the treatment of lower limb bone defects caused by infection, and analyze the mechanism and risk factors of transport gap bending deformity (TGBD).Methods: From January 2008 to December 2019, 326 cases of infected bone defects of the lower extremities were treated by bone transport in our medical institution. The location and other relevant information of TGBD were collected, summarized, and analyzed. The Association for the Study and Application of the Method of Ilizarov (ASAMI) standard was applied to assess the bone and functional outcomes. Results: A total of 326 patients have reconstructed the bone defects in the lower extremities successfully, with a mean size of 6.2 centimeters (3.4 - 9.1 cm). TGBD was observed in 42 patients (12.8%) after removing the external fixator, including 32 tibias and 10 femurs, after a mean follow-up of 28.6 months (22 – 47 months). Age>45years, BMI>25kg/m2, defect of the tibia, diabetes, osteoporosis, glucocorticoid intake, duration of bone infection>24months, EFT>9months, EFI>1.8months/cm were associated significantly with a higher incidence of TGBD in the binary logistic regression analysis. The independent risk factors associated with TGBD included age>45 years, BMI>25 kg/m2, defect of tibia, diabetes, osteoporosis. Conclusions: The bone transport using the Orthofix external fixator is a safe and practical method in the treatment of lower limb bone defects caused by infection. The incidence of TGBD was 12.8%, and the top five risk factors included defect of tibia, BMI>25kg/m2, duration of bone infection>24 months, age>45years, and diabetes. Age>45years, BMI>25kg/m2, defect of tibia, osteoporosis, diabetes were the independent risk factors. The higher incidence of TGBD may be associated with more risk factors.