Effects Of Graft Fixation Angle And Initial Graft Tension On Knee Stability In Anatomic Single-bundle Anterior Cruciate Ligament Reconstruction

Objective: Successful anterior cruciate ligament reconstruction(ACLR)depends on several important factors including knee flexion angle(namely,"graft fixation angle") and initial graft tension when fixing the graft.But there is not yet consensus regarding the knee flexion angle or the initialgraft tension at the time of graft fixation in single-bundle ACLreconstruction(SB ACLR). The range varies from0°(full extension) to30°ofknee flexion for graft fixation angle, and from20N to80N for initial grafttension. In additional, many investigators are paying close attention toanatomic SB ACLR and rotational stability of the knee postoperatively inrecent years. However, there has been few study evaluating the effects ofdifferent graft fixation angles and initial graft tensions on the knee stabilityespecially for the rotational stability during anatomic SB ACLR.Therefore, the purpose of this study is to measure the time-zero anteriortibial translation(ATT), internal rotation(IR) and external rotation(ER) appliedwith different graft fixation angles and initial graft tensions in anatomic SBACLR, and explore the impact of both variables on the stability of knee.Method: Ten human cadaveric knees were included in this study. Therewas no ligament damage, apparent joint deformity and osteoarthritis in everyknee specimen. The femur and tibia were cut approximately13cm from thejoint line. The surrounding skin and muscles more than9cm away from thejoint line were removed to expose the bones, and the fibula was then rigidlyfixed to the tibia with a cortical screw. The allogenic hamstrings were suturedinto the graft for anatomic SB ACLR.Maximal anterior tibial translation(ATT) at30°as well as maximalinternal rotation(IR) and external rotation(ER) at0°,30°,60°and90°of knee flexion were measured by the Electroforce biomechanical system(3520-AT,BOSE company, USA) respectively at (1) ACL-intact,(2) ACL-deficient,(3)6anatomic SB ACLR groups in different graft fixation settings, which wereseparately as the assessment indicators of anterior stability and rotationalstability of the knee.6kinds of graft fixation settings were as follows:(1) kneeflexion at0°and initial graft tensions20N (F₀T₂₀),(2) knee flexion at0°andinitial graft tensions50N (F₀T₅₀),(3) knee flexion at0°and initial grafttensions80N (F₀T₈₀),(4) knee flexion at30°and initial graft tensions20N(F₃₀T₂₀),(5) knee flexion at30°and initial graft tensions50N (F₃₀T₅₀),(6)knee flexion at30°and initial graft tensions80N (F₃₀T₈₀). Every knee wasmeasured3times in each setting and the average value was recorded.The kinematic data from this study were analyzed using the ANOVA(SPSS13.0, SPSS Inc., USA). Significance was set at p<0.05.Results: Anterior tibial translation(ATT): All the anterior translations in6SB ACLR groups(F₀T₂₀, F₀T₅₀, F₀T₈₀, F₃₀T₂₀, F₃₀T₅₀and F₃₀T₈₀) weresignificantly less than in the ACL-deficient group(p<0.05). Though there wereno significant differences among ACL-intact, F₀T₅₀, F₀T₈₀, F₃₀T₅₀andF₃₀T₈₀(P=0.255), the average values of F₃₀T₅₀and F₃₀T₈₀were both less thanthe other groups(F₀T₅₀and F₀T₈₀), which suggested that anatomic SB ACLR inthe graft fixation settings of knee flexion at0°or30°, initial graft tensions50N or80N(F₀T₅₀, F₀T₈₀, F₃₀T₅₀and F₃₀T₈₀) could restore enough anteriorstability of the intact knee.Tibial IR and ER control:6SB ACLR groups(F₀T₂₀, F₀T₅₀, F₀T₈₀, F₃₀T₂₀,F₃₀T₅₀and F₃₀T₈₀)were significantly improved in both of tibial IR and ERcontrol compared with the ACL-deficient group at0°,30°,60°and90°of kneeflexion(p<0.001). At0°of knee flexion, there were no significant differencesamong ACL-intact, F₀T₅₀, F₀T₈₀, F₃₀T₅₀and F₃₀T₈₀in the rotationalstability(PIR=0.982, PER=0.904); at30°of knee flexion, there were nosignificant differences among ACL-intact, F₃₀T₂₀, F₃₀T₅₀and F₃₀T₈₀in therotational stability(PIR=0.937, PER=0.900); at60°, there were no significantdifferences only among ACL-intact, F₃₀T₅₀and F₃₀T₈₀in the rotational stability(P_IR=0.961, P_ER=0.966); and at90°, none of the6ACLR groups wasable to efficiently restore the nomal rotational stability of knee(P<0.05), butthere were no significant differences only among all the6groups(PIR=0.649,PER=0.381). All these outcomes suggested that anatomic SB ACLR in the graftfixation settings of knee flexion at30°, initial graft tensions50N or80N(F₃₀T₅₀and F₃₀T₈₀) could more closely restore the rational stability of theintact knee.Conclusions: Different graft fixation angles and initial graft tensions inanatomic SB ACLR paly an important role in restoring the time-zero ATT, IRand ER of the knee. Though all the SB ACLR groups can't regain the perfectknee stability of the intact knee, anatomic SB ACLR in the graft fixationsettings of knee flexion at30°, initial graft tensions50N or80N could moreclosely restore anterior stability and rational stability of the intact kneeespecially for the rational stability. In sum, the optimal graft fixation angle andinitial graft tension would extremely improve the biomechanical stability ofthe knee when performing an anatomic SB ACLR.