The relationship between the angle of the tibial tunnel in the coronal plane and loss of flexion and anterior laxity after anterior cruciate ligamentreconstruction

Tension in an anterior cruciate ligament graft is greater with the knee in flexion when the angle of the tibia[ tunnel in the coronal plane is vertica l or more perpendicular to the medial joint line of the tibia; however, the relationship of the angle of the tibial tunnel to knee function has not be en studied. Greater graft tension may limit knee flexion or stretch the gra ft and increase anterior laxity. Five surgeons treated 119 subjects by reco nstructing a torn anterior cruciate ligament using a double-looped semitend inosus and gracilis graft and a standardized technique. The femoral tunnel was drilled through the tibia] tunnel. Radiographs were analyzed for tibial tunnel placement and a clinical evaluation was made 4 months postoperative ly. Knees were assigned to subgroups according to the angle of the tibial t unnel in the coronal plane (65 degrees to 69 degrees, 70 degrees to 74 degr ees, 75 degrees to 79 degrees, 80 degrees to 84 degrees, and 85 degrees to 89 degrees), with the angle of the latter subgroup being most vertical. Los s of flexion increased significantly from 0.5 degrees to 6.5 degrees and an terior laxity increased significantly from 0.5 to 2.2 mm as the tunnel angl e was increased. The average angle of the tibial tunnel varied significantl y, degrees 11 between surgeons (range, 69 degrees to 80 degrees). We found a tibial tunnel angle of 75 degrees or more is associated with greater loss of flexion and anterior laxity. Surgeons do not drill the angle of the tib ial tunnel in the coronal plane accurately. We now routinely drill the tibi al tunnel at an angle of 65 degrees to 70 degrees in the coronal plane beca use it may reduce loss of flexion and anterior laxity.