Retraction of transporting bone segment during Ilizarov bone transport

Abstract Background: Retraction of transporting bone segment (TBS) may occur when fixator of TBS is removed before complete mineralization of the distraction callus and union of the docking site. However, there are few reports on the causes and influencing factors of the retraction of TBS.Methods: The clinical data of 37 cases with tibial bone defect treated by Ilizarov bone transport were analyzed retrospectively, in whom the fixator of TBS was removed before maturing of mineralization of the distraction callus and union of the docking site. Bivariate correlation was used to analyze relationship between retraction distance of TBS and factors including age, gender, disease course, length of bone defect, times of operation, size of TBS, transport distance, timing and time interval of removal of TBS fixator. Risk factors with significant level were further identified using multivariate linear regression. Results: Bivariate correlation analysis showed that the timing of removal was negatively correlated with the retraction distance while the time interval, transport distance were positively correlated with the transport distance（all p<0.05); the age, gender, disease course, length of bone defect, size of TBS and times of operation were not correlated with the transport distance（p>0.05). Multivariate linear regression analysis of the 3 risk factors showed that the timing of removal and time interval were the main risk factors for the retraction distance (p<0.05), of which, the timing of removal had the greatest impact, followed by the time interval, but the transport distance was not a main risk factor for the retraction distance (p>0.05).Conclusion: The TBS is subjected to distraction force from all the adherent soft tissues during Ilizarov bone transport, which has elastic properties and can make a retraction of TBS when its fixator is removed before complete mineralization of the distraction callus and union of the docking site. The timing of removal and the time interval are key factors influencing the retraction of TBS.