A Biomechanical Comparison of the EndoButton CL Using Transtibial Drilling and EndoButton Direct Using Anteromedial Arthroscopic Drilling

PurposeTo compare the biomechanical properties of the EndoButton Direct (Smith & Nephew, Andover, MA) with the EndoButton CL (Smith & Nephew) using 2 different drilling techniques. Only the femoral side (and not the tibial side) of the graft fixation complex (bone–fixation device–anterior cruciate ligament [ACL] graft) was examined in this study.MethodsACL reconstructions were performed on 20 cadaveric knees (10 matched pairs), with an age range from 73 to 89 years, by use of a doubled semitendinosus and gracilis tendon graft. Ten knees underwent femoral tunnel drilling from a standard anteromedial arthroscopic portal, and the EndoButton Direct was used for fixation. Ten knees underwent femoral drilling through a medial transtibial approach, and the EndoButton CL was used for fixation. All graft fixation complexes were subjected to 1,000 loading cycles. Graft elongation after 1,000 cycles, stiffness, ultimate load, and mode of failure were determined for each specimen.ResultsThe mean failure load was significantly higher for the EndoButton CL (959.9 ± 190.4 N) compared with the EndoButton Direct (697.7 ± 341.8 N) (P = .05). There was no significant difference in overall stiffness or graft elongation after 1,000 cycles between the 2 fixation devices.ConclusionsThe maximum load during ultimate failure testing was higher for the EndoButton CL with transtibial drilling when compared with the EndoButton Direct with anteromedial drilling. There were no differences found between the EndoButton Direct and EndoButton CL with regard to overall stiffness or elongation after cyclic loading.Clinical RelevanceReduced ultimate failure strength has implications in reconstructed patients if forces imparted on the ACL exceed the strength of graft fixation.