Tibiofemoral joint contact area and stress after single-bundle anterior cruciate ligament reconstruction with transtibial versus anteromedial portal drilling techniques

Background: During single-bundle ACLR, femoral tunnel location plays an important role in restoring the intact knee mechanisms, whereas malplacement of the tunnel was cited as the most common cause of knee instability. The objective of this study is to evaluate, objectively, the tibiofemoral contact area and stress after single-bundle (SB) anterior cruciate ligament reconstruction (ACLR) with femoral tunnel positions drilled by transtibial (TT) or anteromedial (AM) portal techniques. Methods: Seven fresh human cadaveric knees underwent ACLR by the use of TT or AM portal techniques in a randomized order. These specimens were reused for ACL-R (TT and AM). The tibiofemoral contact area and stresses were gauged by an electronic stress-sensitive film inserted into the joint space. The knee was under the femoral axial compressive load of 1000 N using a biomechanics testing machine at 0 degrees, 10 degrees, 20 degrees, and 30 degrees of flexion. Three conditions were compared: (1) intact ACL, (2) ACLR by the use of the 7 method, and (3) ACLR by the use of the AM portal method. Results: Compared with AM portal ACL-reconstructed knees, a significantly decreased tibiofemoral contact area on the medial compartment was detected in the TT ACL-reconstructed knees at 20 degrees of knee flexion (P = .047). Compared with the intact group, the TT ACLR group showed a higher mean stress at 20 degrees and 30 degrees of flexion on the medial compartments (P = .001, P = .003, respectively), while the AM portal ACLR group showed no significant differences at 30 degrees of flexion (P = .073). The TT ACLR group also showed a higher mean maximum stress at 20 degrees of flexion on the medial compartments (P = .047) , while the AM portal ACLR group showed no significant differences at this angle(P = .319). Discussion: The alternation of the tibiofemoral joint contact area and stress in reconstructed knees may be caused by the mismatch of the tibiofemoral joint during knee movement procedures compared with intact knees. Conclusions: SB ACLR by the use of the AM portal method and 7 method both alter the tibiofemoral contact area and stress when compared with the intact knee. When compared with the TT technique, ACLR by the AM portal technique more closely restores the intact tibiofemoral contact area and stress at low flexion angles.