Effects of Graft Bending Angle on the Tensile Behavior of Bone Tunnel-Graft Constructs for Anterior Cruciate Ligament Reconstruction Using Bone-Patellar Tendon–Bone Graft

Bone–patellar tendon–bone (BPTB) grafts used in anterior cruciate ligament reconstruction bend at the femoral tunnel aperture, forming a graft bending angle (GBA). However, the mechanical effects of GBA-related angled loading on bone–BPTB graft constructs remain unclear. This study investigated the effects of GBA and cyclic tensile loading on stiffness and elongation using porcine BPTB grafts. Fourteen specimens were assigned to tibial bone plug constructs (Type T, n = 7) or patellar bone plug constructs (Type P, n = 7). Each construct was cyclically loaded between 10 and 50 N for 50 cycles under GBA conditions of 0°, 30°, 60°, and 90°. Regardless of GBA condition, cyclic loading produced substantial increases in stiffness and elongation during the first 10 cycles, followed by smaller changes. Stiffness tended to decrease under greater GBA conditions, particularly in Type T constructs, where 60° and 90° reduced stiffness and increased elongation. Type P stiffness showed little dependence on GBA. At 0° and 30°, Type P showed lower stiffness and greater elongation than Type T. These findings indicate that bone–BPTB graft tensile behavior is governed by GBA-related loading geometry and bone plug–tendon junction morphology.