Analysis of the graft bending angle at the femoral tunnel aperture in anatomic double bundle anterior cruciate ligament reconstruction: a comparison of the transtibial and the far anteromedial portal technique.

The aim of this study is to investigate and compare the three dimensional bending angle of the graft at the femoral tunnel aperture in the transtibial and the far anteromedial portal technique. Seven fresh-frozen human cadaveric knees were used. Six degrees-of-freedom of knee kinematics and knee position data were measured using an electromagnetic device and the three dimensional bending angles of the each graft at the femoral tunnel aperture were calculated by computer simulation. Additionally, in order to assess the stress on the graft, the length change between the femoral and tibial attachment sites of the AM and PL bundle were calculated. The maximum length of each bundle was detected at full extension of the knee. The relative change of the length of the PL bundle in the range of 70 degrees -0 degrees of knee flexion was significantly larger than that of the AM bundle. (P < 0.05) Maximum graft bending angles in both techniques were obtained at full extension where the graft was fully stretched. The AM and PL graft bending angles in the transtibial technique were significantly larger than in the far anteromedial portal technique at low flexion angle (AM: 0 degrees -10 degrees , PL: 0 degrees -50 degrees ) (P < 0.01). This suggests use of the far anteromedial portal technique might result in lower stress on the graft at the femoral tunnel aperture and therefore might reduce graft damage.