Clinical translation and challenges of biodegradable magnesium-based interference screws in ACL reconstruction

As one of the most promising fixators developed for anterior cruciate ligament(ACL)reconstruction,biodegradable magnesium(Mg)-based interference screws have gained increasing attention attributed to their appropriate modulus and favorable biological properties during degradation after surgical insertion.However,its fast degradation and insufficient mechanical strength have also been recognized as one of the major causes to limit their further application clinically.This review focused on the following four parts.Firstly,the advantages of Mg or its alloys over their counterparts as orthopaedic implants in the fixation of tendon grafts in ACL reconstruction were discussed.Subsequently,the underlying mechanisms behind the contributions of Mg ions to the tendon-bone healing were introduced.Thirdly,the technical challenges of Mg-based interference screws towards clinical trials were discussed,which was followed by the introduction of currently used modification methods for gaining improved corrosion resistance and mechanical properties.Finally,novel strategies including development of Mg/Titanium(Ti)hybrid fixators and Mg-based screws with innovative structure for achieving clinically customized therapies were proposed.Collectively,the advancements in the basic and translational research on the Mg-based interference screws may lay the foundation for exploring a new era in the treatment of the tendon-bone insertion(TBI)and related disorders.

Biomechanical evaluation of a novel transtibial posterior cruciate ligament reconstruction using high-strength sutures in a porcine bone model

Background:Multiple techniques are commonly used for posterior cruciate ligament(PCL)reconstruction.However,the optimum method regarding the fixation of PCL reconstruction after PCL tears remains debatable.The purpose of this study was to compare the biomechanical properties among three different tibial fixation procedures for transtibial single-bundle PCL reconstruction.Methods:Thirty-six porcine tibias and porcine extensor tendons were randomized into three fixation study groups:the interference screw fixation(IS)group,the transtibial tubercle fixation(TTF)group,and TTF+IS group(n=12 in each group).The structural properties of the three fixation groups were tested under cyclic loading and load-to-failure.The slippage after the cyclic loading test and the stiffness and ultimate failure load after load-to-failure testing were recorded.Results:After 1000 cycles of cyclic testing,no significant difference was observed in graft slippage among the three groups.For load-to-failure testing,the TTF+IS group showed a higher ultimate failure load than the TTF group and the IS group(876.34±58.78 N vs.660.92±77.74 N[P<0.001]vs.556.49±65.33 N[P<0.001]).The stiffness in the TTF group was significantly lower than that in the IS group and the TTF+IS group(92.77±20.16 N/mm in the TTF group vs.120.27±15.66 N/m in the IS group[P=0.001]and 131.79±17.95 N/mm in the TTF+IS group[P<0.001]).No significant difference in the mean stiffness was found between the IS group and the TTF+IS group(P=0.127).Conclusions:In this biomechanical study,supplementary fixation with transtibial tubercle sutures increased the ultimate failure load during load-to-failure testing for PCL reconstruction.