The Ideal Cortical Button Location on the Lateral Femur for Anterior Cruciate Ligament Suspensory Fixation is 30 mm Proximal to the Lateral Epicondyle

Abstract

Purpose: To determine the ideal location for anterior cruciate ligament (ACL) suspensory cortical button placement on the lateral femur with the highest failure load and to establish the relationship of tunnel diameter and cortical thickness on load to failure. Methods: Computed tomography (CT) data were obtained from 45 cadaveric distal femurs. A Cartesian coordinate system was established along the lateral femur with the lateral epicondyle (LE) as a reference point. Locations 0, 20 and 30 mm from the LE along lines 0 , 25 , 50 , and 75 posterioproximal from the axial plane were created. Tunnels connecting from each location to the center of the ACL footprint were simulated. Cortical thickness and long axis diameter of the oval cortical holes were determined for each location. Based on the CT data, custom drill guides were created and used to drill 4.5 mm tunnels at each lateral femur location to the ACL footprint on the cadaver femurs. Cortical buttons were placed at each location and pulled using a servohydraulic testing system. The correlation of tunnel diameter and cortical thickness to button failure load were analyzed using a regression analysis. Results: Significant differences were found for failure load (P<.0001) and cortical thickness between the locations tested (P<.0001). The location 30 mm proximal from the LE and 75⁰ from the axial plane had the highest failure load of 573 N. A regression analysis (R 2 ¼ .15) indicated that the cortical thickness was significantly correlated with load to failure (P <.0001), whereas the long-axis diameter was not (P ¼ .33). Conclusion: The ideal cortical button location on the lateral femur for ACL suspensory fixation was located 30 mm proximal from the lateral epicondyle, based on this area's high failure load. Oblique tunnel drilling of this proximal location may cause a larger long-axis diameter cortical hole, but the cortex is also thicker, which is more closely correlated with failure load. Clinical Relevance: Different ACL suspensory cortical button locations on the lateral femur have different failure loads based on the cortical thickness of the bone supporting the button. It is important for surgeons to understand which drilling techniques place the button in a proximal and posterior location, especially if the bone quality of the patient is of concern.

Three-Dimensional Modeling and Simulation of Normal Knee Joint Motion

“…Besides, it allows the surgeon reduces the risk of breaching the posterior femoral cortex by not going too low and posteriorly during femoral tunnel preparation. The finding of this study strengthens the report by previous studies that have discussed the importance of sagittal and axial drill angle in determining the FTO and the length of the femoral tunnel [6], [7]. However, this study did not evaluate the relationship between the drill angles and the arthroscopic portals used in transportal ACLR.…”

Compressibility of Osteochondral Autograft Transfer Donor Grafts: A Comparison of Different Donor Regions and How Much Shortening Occurs of Plugs After Impaction

“… 5 , 25 , 26 It has also been shown that different regions of bone can have different densitomes, or different bone density leading to differing amount of structural integrity. 20 Ideally, all grafts will sit flush with the surrounding articular surface; however, a delicate balance exists between proud grafts, flush grafts that are difficult to seat, and oversunk grafts. Our study shows that OAT donor grafts show the highest compressibility in the medial trochlea and lateral IC notch.…”

Quantitative cotyloid fossa thickness and proximity to obturator neurovascular bundle: implications for arthroscopic ligamentum teres reconstruction

“…Since the most available hip joint suture anchors are more than 5 mm in length [ 16 ], a medial wall perforation, with possible insufficient fixation, is to be expected in about 63% of the patients, suggesting that bone anchors might not be suitable for fixation of the graft in LTR, and an alternative implant such as cortical button should be considered. Nevertheless, in some patients, the cortical bone at the cotyloid fossa is very thin, and therefore, an excessive tightening of the graft should not be performed to avoid cortical button cut through the bone, as the maximal load to failure of the cortical button is positively correlated with the tunnel diameter and cortical thickness [ 17 ].…”