Effect of Initial Graft Tension on Knee Stability and Graft Tension Pattern in Double-Bundle Anterior Cruciate Ligament Reconstruction

PurposeTo determine the initial minimal tension for restoring knee stability during double-bundle anterior cruciate ligament (ACL) reconstruction in vivo.MethodsPatients who underwent primary double-bundle ACL reconstruction with an autologous semitendinosus tendon during 2012 were included. The bundles were fixed to a graft-tensioning system during surgery. Initial graft tensions were set to the following tensions per 6 mm in graft diameter: (1) 30 N, (2) 25 N, and (3) 20 N. Bundle tension was recorded during knee flexion-extension and in response to anterior or rotatory loads. In addition, anterior knee laxity was measured with the KT-1000 arthrometer (MEDmetric, San Diego, CA), and the pivot-shift test was evaluated.ResultsSixty patients were evaluated. The tension curves of both bundles among different initial tension settings were significantly different (P < .0001), with the tension in the 30-N setting being highest and that in the 20-N setting being lowest. The tension in both bundles showed reciprocal pattern during flexion-extension (P = .019). The tension of the posterolateral bundle graft was significantly lower than that of the anteromedial bundle graft in response to the anterior load at all settings (P = .0017, P = .0019, and P = .0021 at 30° in the 30-N, 25-N, and 20-N settings, respectively, and P < .0001 at 90° at all settings), whereas the tensions in both bundles in response to rotatory loads were equivalent. Two cases showed a grade 1 pivot shift in the 20-N setting, whereas no case showed a positive pivot shift in the other settings. KT measurements in the 30-N and 25-N settings showed no difference.ConclusionsIn double-bundle ACL reconstruction, initial tension could be set as low as 25 N; however, initial tension of 20 N is not recommended because it might result in residual pivot shift in some cases, although the pivot-shift difference was not significant.Level of EvidenceLevel IV, therapeutic case series.