The design and clinical application of a new type of dynamic Hoffmann external fixator for tibial shaft fractures / 中华创伤骨科杂志

ABSTRACT

Objective To explore biomechanical properties and clinical results of a new type of dynamic Hoffmann external fixator(NDHEF)for tibial shaft fractures.Methods Fifteen specimens of adult tibia were randomly divided into three groups and osteotomized obliquely in the mid part of the tibia.These specimens were fixed with NDHEF,improved Hoffmann external fixator(IHEF)and maltifunctional external fixator(MEF)re- spectively.The axial compression,bending,torsion and stress shielding tests were performed on the specimens in each group for biomechanical comparison.From 1995 to 2004,40 cases of open tibiofihular fractures were treated with NDHEF and 88 cases with IHEF and their clinical results were analyzed and compared.Results The biomechanical tests showed that the compressive rigidity,bending rigidity and torsion rigidity of NDHEF were similar to those of IHEF(P＞0.05)but significantly stronger than those of MEF(P＜0.05).The stress shielding of NDHEF was obviously weaker than that of other external fixators(P＜0.05).All the 128 cases were followed up for 12 to 36 months(average,16.8 months).The mean substantial bone healing time for NDHEF treatment was 22.3 weeks and that for IHEF was 26.8 weeks.The difference was significant(P＜0.05).The rates of delayed union and malunion were all 7.5% for NDHEF,but 15.9% and 4.5% respectively for IHEF.The difference was insignificant (P＞0.05).Conclusions The biomechanical performance of NDHEF is superior to that of IHEF,for it can diminish the stress shielding and accelerate bone healing.It is a good external fixator for tibial fractures.