Retraction of transporting bone segment during Ilizarov bone transport

Abstract Background: Retraction of transporting bone segment (TBS) may occur when the TBS fixator was removed prior to full consolidation of the distracted callus, which has adverse effect on the healing of the docking site. However, there are few reports on the retraction of TBS. The purpose of this study is to analyze the causes and risk factors of 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 TBS fixator was removed prior to full consolidation of the distracted callus and union of the docking site. Bivariate correlation was used to analyze relationship between the retraction distance of TBS and potential risk factors including age, gender, course, length of bone defect, number of operations, 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 showed that the timing of removal was negatively correlated while the time interval and transport distance were positively correlated with the retraction distance（p<0.05), the age, gender, course, length of bone defect, size of TBS and number of operations were not correlated with the retraction distance（p>0.05). Multivariate linear regression 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), but the transport distance was not (p>0.05).Conclusion: The traction forces of TBS endured from the soft tissues and the unconsolidated distracted callus have elastic properties, which can make retraction of TBS. The timing of removal and time interval are the main factors of retraction distance. In the case of early removal, another external fixation should be performed or quickly converted to internal fixation to avoid the adverse effect of more retraction.