Retraction and force analysis of transporting bone segment during Ilizarov bone transport

Background: Previous research rarely reported the cause and relevant factors of retraction of transporting bone segment (TBS). The purpose of this study is to analyze the force and cause of retraction of TBS during Ilizarov bone transport after removal of its fixator. Methods: 37 cases with tibial bone defect treated by Ilizarov bone transport, in whom the fixator of TBS was removed before mature of mineralization of the distraction callus or union of the docking site, were analyzed retrospectively. Bivariate correlation was used to analyze relationship between retraction distance of TBS and age, gender, disease course, length of bone defect, times of pre-operation, size of TBS, transport distance, cause of removal, 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 the timing of removal was negatively correlated while the time interval, cause of removal, transport distance and size of TBS were positively correlated with the transport distance（all p0.05). Multivariate linear regression analysis showed the timing of removal, transport distance and size of TBS were significant risk factors for the retraction distance (p<0.05), of which, the timing of removal had the greatest impact, followed by the transport distance and size of TBS, however the cause of removal and time interval were not significant for the retraction (p>0.05). Conclusion: The traction force of the TBS endured from soft tissue , not from the distraction callus, is elastic and can induce a retraction of TBS when its fixator is removed in advance. The retraction distance is related to the size of TBS, transport distance and timing of removal, especially the timing of removal is an independent risk factor.