Effect of Knee Flexion Angle on Tunnel Length and Articular Cartilage Damage During Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction (SS-54)

Abstract

SummaryAnatomic double-bundle ACL reconstruction is technically challenging and requires accurate placement of both tibial and femoral tunnels for an optimal outcome. In this study we examined the effect of knee flexion angle during guidewire placement for femoral anteromedial and posterolateral tunnels on the resultant tunnel length and relationship to the articular surface. We demonstrate the importance of obtaining maximal knee flexion during guidewire placement to maximize tunnel length and avoid penetration of the posterolateral femoral articular surface. Understanding tunnel length and location are critical when utilizing suspensory fixation such as the EndoButton device for femoral fixation.PurposeThe purpose of this study was to examine the effect of knee flexion angle and surgical technique (transtibial versus accessory medial portal) for drilling of the femoral anteromedial (AM) and posterolateral (PL) tunnels during anatomic ACL reconstruction on risk of articular cartilage penetration and tunnel length.MethodsSix cadaveric knees were prepared for anatomic ACL reconstruction. The knees were mounted to allow 0-130 degrees of flexion. Standard lateral, medial, and accessory medial portals were established. The ACL was debrided and the center of the AM and PL bundles were marked. Utilizing an ACL tip-guide set to 45-degrees, a 3.2mm guidewire was passed through the center of the PL tibial footprint. A second guidewire was then passed through the center of the AM tibial footprint. Seven and 8mm tunnels were drilled for the PL and AM bundles respectively. Femoral tunnel guidewires were then placed. The knee was held at 90-degrees of flexion and guidewires were placed from the accessory medial portal through the center of the PL and AM femoral footprints. This technique was repeated at 110- and 130-degrees of flexion. Two additional guidewires were placed for the AM femoral tunnel utilizing a transtibial technique through the AM and PL tunnels. Knee flexion was adjusted allowing optimal placement of the guidewire within the AM bundle footprint. Following guidewire placement, the lateral femur was exposed and the distance from the guidewire to the articular margin as well as the tunnel length were measured. ANOVA analysis was utilized to determine significance (p<0.05).ResultsPL bundle guidewires exited the lateral femoral condyle an average of 4.0mm, 9.2mm, and 16.3mm from the articular margin for 90-, 110-, and 130-degrees of knee flexion respectively. Sixty-seven percent and 17% of guidewires penetrated the articular surface at 90- and 110-degrees respectively. AM bundle guidewires exited the lateral femoral condyle an average of 5.8mm, 10.7mm, and 20.2mm from the articular margin for 90-, 110-, and 130-degrees of knee flexion respectively. Thirty-three percent of the guidewires penetrated the articular surface at 90-degrees. Guidewires passed transtibial through either the PL or AM tunnel averaged 34.4mm and 33.9mm from the articular margin respectively. PL and AM femoral tunnel length increased with knee flexion. PL tunnel lengths averaged 27.2mm, 31.5mm, and 31.7mm at 90-, 110-, and 130-degrees of knee flexion respectively. AM tunnel lengths averaged 24.2, 27.8mm, and 32.5mm at 90-, 110-, and 130-degrees of knee flexion respectively. Transtibial guidewire passage significantly increased AM tunnel length to 42.2mm for trans-PL tunnel passage and 46mm for trans-AM tunnel passage (p<0.05).ConclusionsFailure to obtain knee flexion greater than 110-degrees during preparation of either the AM or PL tunnel through an accessory medial portal risks penetration of the articular surface with the guidewire, drill, or fixation device. Additionally, tunnel length for the AM and PL femoral tunnels was found to increase with greater degrees of knee flexion. Transtibial AM tunnel placement generates the longest tunnels but tunnel placement within the anatomic center of the AM femoral footprint may be difficult to achieve. SummaryAnatomic double-bundle ACL reconstruction is technically challenging and requires accurate placement of both tibial and femoral tunnels for an optimal outcome. In this study we examined the effect of knee flexion angle during guidewire placement for femoral anteromedial and posterolateral tunnels on the resultant tunnel length and relationship to the articular surface. We demonstrate the importance of obtaining maximal knee flexion during guidewire placement to maximize tunnel length and avoid penetration of the posterolateral femoral articular surface. Understanding tunnel length and location are critical when utilizing suspensory fixation such as the EndoButton device for femoral fixation. Anatomic double-bundle ACL reconstruction is technically challenging and requires accurate placement of both tibial and femoral tunnels for an optimal outcome. In this study we examined the effect of knee flexion angle during guidewire placement for femoral anteromedial and posterolateral tunnels on the resultant tunnel length and relationship to the articular surface. We demonstrate the importance of obtaining maximal knee flexion during guidewire placement to maximize tunnel length and avoid penetration of the posterolateral femoral articular surface. Understanding tunnel length and location are critical when utilizing suspensory fixation such as the EndoButton device for femoral fixation. PurposeThe purpose of this study was to examine the effect of knee flexion angle and surgical technique (transtibial versus accessory medial portal) for drilling of the femoral anteromedial (AM) and posterolateral (PL) tunnels during anatomic ACL reconstruction on risk of articular cartilage penetration and tunnel length. The purpose of this study was to examine the effect of knee flexion angle and surgical technique (transtibial versus accessory medial portal) for drilling of the femoral anteromedial (AM) and posterolateral (PL) tunnels during anatomic ACL reconstruction on risk of articular cartilage penetration and tunnel length. MethodsSix cadaveric knees were prepared for anatomic ACL reconstruction. The knees were mounted to allow 0-130 degrees of flexion. Standard lateral, medial, and accessory medial portals were established. The ACL was debrided and the center of the AM and PL bundles were marked. Utilizing an ACL tip-guide set to 45-degrees, a 3.2mm guidewire was passed through the center of the PL tibial footprint. A second guidewire was then passed through the center of the AM tibial footprint. Seven and 8mm tunnels were drilled for the PL and AM bundles respectively. Femoral tunnel guidewires were then placed. The knee was held at 90-degrees of flexion and guidewires were placed from the accessory medial portal through the center of the PL and AM femoral footprints. This technique was repeated at 110- and 130-degrees of flexion. Two additional guidewires were placed for the AM femoral tunnel utilizing a transtibial technique through the AM and PL tunnels. Knee flexion was adjusted allowing optimal placement of the guidewire within the AM bundle footprint. Following guidewire placement, the lateral femur was exposed and the distance from the guidewire to the articular margin as well as the tunnel length were measured. ANOVA analysis was utilized to determine significance (p<0.05). Six cadaveric knees were prepared for anatomic ACL reconstruction. The knees were mounted to allow 0-130 degrees of flexion. Standard lateral, medial, and accessory medial portals were established. The ACL was debrided and the center of the AM and PL bundles were marked. Utilizing an ACL tip-guide set to 45-degrees, a 3.2mm guidewire was passed through the center of the PL tibial footprint. A second guidewire was then passed through the center of the AM tibial footprint. Seven and 8mm tunnels were drilled for the PL and AM bundles respectively. Femoral tunnel guidewires were then placed. The knee was held at 90-degrees of flexion and guidewires were placed from the accessory medial portal through the center of the PL and AM femoral footprints. This technique was repeated at 110- and 130-degrees of flexion. Two additional guidewires were placed for the AM femoral tunnel utilizing a transtibial technique through the AM and PL tunnels. Knee flexion was adjusted allowing optimal placement of the guidewire within the AM bundle footprint. Following guidewire placement, the lateral femur was exposed and the distance from the guidewire to the articular margin as well as the tunnel length were measured. ANOVA analysis was utilized to determine significance (p<0.05). ResultsPL bundle guidewires exited the lateral femoral condyle an average of 4.0mm, 9.2mm, and 16.3mm from the articular margin for 90-, 110-, and 130-degrees of knee flexion respectively. Sixty-seven percent and 17% of guidewires penetrated the articular surface at 90- and 110-degrees respectively. AM bundle guidewires exited the lateral femoral condyle an average of 5.8mm, 10.7mm, and 20.2mm from the articular margin for 90-, 110-, and 130-degrees of knee flexion respectively. Thirty-three percent of the guidewires penetrated the articular surface at 90-degrees. Guidewires passed transtibial through either the PL or AM tunnel averaged 34.4mm and 33.9mm from the articular margin respectively. PL and AM femoral tunnel length increased with knee flexion. PL tunnel lengths averaged 27.2mm, 31.5mm, and 31.7mm at 90-, 110-, and 130-degrees of knee flexion respectively. AM tunnel lengths averaged 24.2, 27.8mm, and 32.5mm at 90-, 110-, and 130-degrees of knee flexion respectively. Transtibial guidewire passage significantly increased AM tunnel length to 42.2mm for trans-PL tunnel passage and 46mm for trans-AM tunnel passage (p<0.05). PL bundle guidewires exited the lateral femoral condyle an average of 4.0mm, 9.2mm, and 16.3mm from the articular margin for 90-, 110-, and 130-degrees of knee flexion respectively. Sixty-seven percent and 17% of guidewires penetrated the articular surface at 90- and 110-degrees respectively. AM bundle guidewires exited the lateral femoral condyle an average of 5.8mm, 10.7mm, and 20.2mm from the articular margin for 90-, 110-, and 130-degrees of knee flexion respectively. Thirty-three percent of the guidewires penetrated the articular surface at 90-degrees. Guidewires passed transtibial through either the PL or AM tunnel averaged 34.4mm and 33.9mm from the articular margin respectively. PL and AM femoral tunnel length increased with knee flexion. PL tunnel lengths averaged 27.2mm, 31.5mm, and 31.7mm at 90-, 110-, and 130-degrees of knee flexion respectively. AM tunnel lengths averaged 24.2, 27.8mm, and 32.5mm at 90-, 110-, and 130-degrees of knee flexion respectively. Transtibial guidewire passage significantly increased AM tunnel length to 42.2mm for trans-PL tunnel passage and 46mm for trans-AM tunnel passage (p<0.05). ConclusionsFailure to obtain knee flexion greater than 110-degrees during preparation of either the AM or PL tunnel through an accessory medial portal risks penetration of the articular surface with the guidewire, drill, or fixation device. Additionally, tunnel length for the AM and PL femoral tunnels was found to increase with greater degrees of knee flexion. Transtibial AM tunnel placement generates the longest tunnels but tunnel placement within the anatomic center of the AM femoral footprint may be difficult to achieve. Failure to obtain knee flexion greater than 110-degrees during preparation of either the AM or PL tunnel through an accessory medial portal risks penetration of the articular surface with the guidewire, drill, or fixation device. Additionally, tunnel length for the AM and PL femoral tunnels was found to increase with greater degrees of knee flexion. Transtibial AM tunnel placement generates the longest tunnels but tunnel placement within the anatomic center of the AM femoral footprint may be difficult to achieve.