Background: Accidental graft contamination is a likely complication to occur in an orthopaedic sports medicine surgeon’s career. There are no clinical outcome studies to direct management, and a recent survey showed that preferred management varied. Three liters of 2% chlorhexidine power irrigation has been shown to be an efficient and effective disinfection protocol; however, the biomechanical sequelae of this disinfection protocol to the graft are unknown.
Purpose: The purpose of this study was to determine if 3 L of 2% chlorhexidine power irrigation used to disinfect contaminated anterior cruciate ligament (ACL) grafts significantly weakens the graft at time zero.
Study Design: Controlled laboratory study.
Methods: Eight fresh bovine superficial digital flexor tendons underwent disinfection protocol with 3 L of 2% chlorhexidine power irrigation. Contralateral tendons served as the control. Tendons were preconditioned and loaded to failure.
Results: The average ultimate failure load for the control tendons and disinfected tendons was 4081 ± 654.4 N and 4146 ± 723.2 N, respectively. The average ultimate failure stress for the control tendons and disinfected tendons was 97.10 ± 12.03 MPa and 95.18 ± 11.79 MPa, respectively. The average stiffness for the control tendons and disinfected tendons was 546.20 ± 28.16 N/mm and 539.2 ± 25.93 N/mm, respectively. The P values for ultimate failure load, ultimate failure stress, and stiffness showed no statistically significant difference between the chlorhexidine and control tendons.
Conclusion: Disinfecting tendons with 3 L of 2% chlorhexidine power irrigation does not adversely weaken the tendon’s tensile mechanical properties.
Clinical Relevance: Three liters of 2% chlorhexidine power irrigation can effectively disinfect a contaminated ACL graft without weakening the graft.
Background: Although both anatomic double-bundle and single-bundle anterior cruciate ligament reconstruction procedures are in use, it remains controversial whether the anatomic double-bundle procedure is biomechanically superior.
Hypothesis: The anatomic double-bundle procedure would be better than both laterally placed anatomic and nonanatomic transtibial single-bundle procedures at restoring to normal the tibial anterior translation, internal rotation, and pivot-shift instability. It was also hypothesized that tibial internal rotation would be closer to normal after laterally placed anatomic single-bundle reconstruction than after the nonanatomic reconstruction.
Study Design: Controlled laboratory study.
Methods: Eight cadaveric knees were mounted in a 6 degrees of freedom rig and tested using the following loading conditions: 90-N anterior and posterior tibial forces, 5-N·m internal and external tibial rotation torques, and a simulated pivot-shift test. Tibiofemoral kinematics during the flexion-extension cycle were recorded with an optical tracking system for (1) intact, (2) anterior cruciate ligament–deficient knee, (3) anatomic double-bundle reconstruction, (4) nonanatomic single-bundle reconstruction, and (5) laterally placed single-bundle reconstruction.
Results: Rotational laxity with internal tibial torque and anterior laxity in the simulated pivot shift were significantly less in the double-bundle reconstruction and laterally placed single-bundle reconstruction compared with the nonanatomic single-bundle reconstruction. There were no significant differences between the 3 procedures when anterior and posterior tibial translation forces and external rotation torques were applied. In addition, there were no significant differences between the double-bundle reconstruction and laterally placed single-bundle reconstruction.
Conclusion: The postoperative rotational and pivot-shift laxity after anatomic double-bundle anterior cruciate ligament reconstruction was significantly better than that after nonanatomic single-bundle reconstruction. However, there were no significant differences between the double-bundle reconstruction and laterally placed single-bundle reconstruction.
Clinical Relevance: This work suggests that a single-bundle reconstruction may be better able to control both knee laxity and pivot-shift instability if the femoral tunnel is moved to a more lateral position and that then the double-bundle reconstruction may not offer significant further advantages.
Background
Traditionally, a standard femoral tunnel for a single-bundle anterior cruciate ligament (ACL) reconstruction is positioned 6 to 7 mm anterior to the posterior wall at an 11 o’clock orientation in the femoral notch (right knee). However, some surgeons have advocated placing the femoral tunnel at a more oblique orientation at or near the femoral footprint of the ACL’s posterolateral bundle (at approximately 9:30 to 10 o’clock in the notch) to provide the graft with a better mechanical advantage for controlling tibial rotation and eliminating the pivot shift.
Hypothesis
Moving the femoral tunnel from the standard location to an oblique position in the femoral notch will significantly reduce the magnitude of a simulated pivot shift.
Study Design
Controlled laboratory study.
Methods
Internal-external tibial rotation and anteroposterior (AP) displacement of the lateral tibial plateau were measured in 17 fresh-frozen cadaveric knees during a simulated pivot-shift event with a single-bundle ACL reconstruction placed in standard and oblique femoral tunnels. Baseline kinematic measurements were taken with the graft tensioned to restore intact AP knee laxity at 30° of flexion. The measurements were repeated as graft tension was decreased to produce approximately 2-mm incremental increases in laxity (up to +10 mm). Correlations between lateral tibial plateau displacement and tibial rotation during the pivot shift were determined for both tunnels.
Results
There were no significant differences in tibial rotations or tibial plateau displacements during the pivot shift between standard and oblique femoral tunnels when the graft was tensioned to restore intact knee laxity. The relationship between pivot-shift magnitude and AP laxity was highly linear for each knee specimen over the range of laxities tested; the mean slopes for anteromedial (AM) and posterolateral (PL) tunnels were not significantly different. There were near perfect linear correlations (mean r2 >.98) between lateral plateau displacement and tibial rotation for both femoral tunnel positions; the slope of the regression line was not significantly different between tunnels.
Conclusion
Moving the femoral tunnel from the standard location to a more oblique position in the notch did not significantly alter pivot-shift kinematics. Lateral plateau displacement was strongly correlated with tibial rotation, and either can be used to quantify the pivot shift.
Clinical Relevance
The rationale for placing the femoral tunnel at an oblique position in the notch to reduce the pivot shift is questioned.
Background: Sterilization of anterior cruciate ligament (ACL) allografts is an important prerequisite to prevent disease transmission. However, mechanical tissue properties are compromised by most current sterilization procedures, so that uncompromised sterilization of allografts is difficult to achieve.
Hypothesis/Purpose: The aim of this study was to evaluate the effect of the novel electron beam sterilization procedure on the biomechanical properties of human patellar tendon allografts at various irradiation dosages. Electron beam sterilization may be an appropriate alternative to gamma sterilization.
Study Design: Controlled laboratory study.
Methods: Thirty-two human 10-mm wide bone-patellar tendon-bone grafts were randomized into 4 groups of sterilization with 15, 25, or 34 kGy of electron beam irradiation, respectively. The grafts’ biomechanical properties were evaluated at time zero. Unsterilized grafts functioned as controls. Biomechanical properties were analyzed during cyclic and load-to-failure testing.
Results: Strain and cyclic elongation response showed no significant differences between the groups. Electron beam irradiation had no significant effect on stiffness and failure load with the exception of 34 kGy, which resulted in a significant decrease in failure load (1300.6 ± 229.2 N) compared with unsterilized grafts (1630.5 ± 331.1 N).
Conclusion: This study showed that electron beam might be an appropriate alternative in sterilization of patellar tendon allografts with minimal effect on mechanical properties of tendon grafts in vitro. Future studies will have to evaluate the effect of the process on the biological properties of allografts in vitro and in vivo.
Clinical Relevance: Terminal sterilization of patellar tendon allografts with electron beam irradiation can ensure higher safety of transplanted grafts and hence improve patient safety and acceptance.
Background: Several trials have compared the clinical results between anatomic double-bundle and single-bundle anterior cruciate ligament reconstruction procedures. However, it remains controversial whether the anatomic double-bundle procedure is superior to the single-bundle procedure.
Hypothesis: The anatomic double-bundle procedure will be better than the single-bundle procedure at resisting anterior laxity, internal rotation laxity, and pivot-shift instability.
Study Design: Controlled laboratory study.
Methods: Eight cadaveric knees were tested in a 6 degrees of freedom rig using the following loading conditions: 90-N anterior tibialforce, 5-N·m internal and external tibial torques, and a simulated pivot-shift test. Tibiofemoral kinematics during the flexion-extension cycle were recorded with an optical tracking system for (1) intact, (2) anterior cruciate ligament–deficient knee, (3) anatomic double-bundle reconstruction, and (4) single-bundle reconstruction placed at 11 o’clock in the intercondylar notch.
Results: There were significant reductions of anterior laxity of 3.5 mm at 20° of flexion, internal rotational laxity of 2.5° at 20° of flexion, and anterior translations (2 mm) and internal rotations (5°) in the simulated pivot-shift test in the double-bundle reconstruction com-pared with the single-bundle reconstruction. There were no significant differences between the 2 procedures for external rotation laxity.
Conclusion: The postoperative anterior translation and internal rotation stability after anatomic double-bundle anterior cruciate ligament reconstruction were significantly better than after single-bundle reconstruction, in both static tests and the pivot shift.
Clinical Relevance: Unlike previous laboratory studies, this work used clinical arthroscopic methods for anterior cruciate ligament reconstruction, and found that the anatomic reconstruction was superior to a single graft placed at 11 o’clock.
