Mechanical evaluation of tibial fixation of the hamstring tendon in anterior cruciate ligament double-bundle reconstruction with and without interference screws

OBJECTIVE: The objective of this study was to compare two postero-lateral bundle (PLB) tibial fixation techniques for the reconstruction of the anterior cruciate ligament with double bundle: a technique without the use of an interference screw, preserving the native tibial insertion of the tendons of the gracilis and semitendineous muscles, and a technique with the use of an interference screw and without preserving the insertion of the tendons. METHODS: A comparative study was conducted in cadavers with a universal mechanical test machine. In total, 23 cadaver knees were randomized for tibial fixation of the PLB using the two techniques: Maintaining the tibial insertion of the tendons during reconstruction, without the use of an interference screw (group A, 11 cases); and fixating the graft with an interference screw, without maintaining the insertion of the tendons (group B, 12 cases). A continuous traction was performed (20 mm/min) in the same direction as the produced tunnel, and force (N), elongation (mm), rigidity (N/mm), and tension (N/mm(2)) were objectively determined in each group. RESULTS: Group A exhibited a maximum force (MF) of 315.4 +/- 124.7 N; maximum tension of 13.57 +/- 3.65 N/mm(2); maximum elongation of 19.73 +/- 4.76 mm; force at the limit of proportionality (FLP) of 240.6 +/- 144.0 N; and an elongation at the limit of proportionality of 14.37 +/- 6.58 mm. Group B exhibited a MF of 195.7 +/- 71.8 N; maximum tension of 8.8 +/- 3.81 N/mm(2); maximum elongation of 15.3 +/- 10.73 mm; FLP of 150.1 +/- 68.7 N; and an elongation at the limit of proportionality of 6.86 +/- 2.42 mm. When comparing the two groups, significant differences were observed in the variables of maximum force (p=0.016), maximum tension (p=0.019), maximum elongation (p=0.007), and elongation at the limit of proportionality (p=0.003). CONCLUSION: The use of the native insertion of the semitendineous and gracilis tendons, without an additional fixation device, presented mechanical superiority over their fixation with interference screws.