Relation Between Anterior Cruciate Ligament Graft Obliquity and Knee Laxity in Elite Athletes at the National Football League Combine

PurposeThe purposes of this study were to determine the incidence of vertical anterior cruciate ligament (ACL) reconstructions in elite athletes and to determine whether graft obliquity correlates with knee stability in this population.MethodsOne hundred thirty-seven knees in 125 athletes at the 2005-2009 National Football League Combine were identified as having had previous ACL reconstructions. The graft type, fixation, and physical examination findings were recorded for each athlete. Graft obliquity was measured by previously described methods based on plain radiography and magnetic resonance imaging (MRI). Radiographic measurements included tibial tunnel and femoral tunnel locations, as well as a sum of these tunnel positions on the lateral radiograph (sum score). MRI measurements included sagittal and coronal ACL angles and the ACL–Blumensaat line angle. The relation of graft obliquity to physical examination findings was assessed.ResultsSixty-four percent of knees had vertical grafts based on radiography and 35% based on MRI criteria. The average tibial tunnel location on radiography was 33% from the anterior tibial plateau in the oblique group compared with 42% in the vertical group (P < .0001). Knees with a sum score of 66 or less, tibial tunnel 37% or less from the anterior tibial plateau, and sagittal obliquity of 60° or less were less likely to have increased translation on the Lachman examination than knees with a sum score greater than 66, tibial tunnel greater than 37% from the anterior tibial plateau, and sagittal obliquity greater than 60° (P < .05).ConclusionsThere was a wide range of ACL graft obliquity in the examined cohort of elite athletes who continued to perform at high levels. Less oblique (more vertical) grafts were associated with greater anterior tibial translation on Lachman testing. ACL graft obliquity, which is particularly sensitive to tibial tunnel placement, can influence knee stability.Level of EvidenceLevel IV, therapeutic case series.