Coen A. Wijdicks

The Anterolateral Ligament An Anatomic, Radiographic, and Biomechanical Analysis

Background: Recent publications have described significant variability in the femoral attachment and overall anatomy of the anterolateral ligament (ALL). Additionally, there is a paucity of data describing its structural properties. Purpose: Quantitative data characterizing the anatomic and radiographic locations and the structural properties of the ALL may be used to guide graft selection and placement and to facilitate the future development of an evidence-based approach to ALL reconstructions. Study Design: Descriptive laboratory study. Methods: Identification of the ALL was performed by a combined outside-in and inside-out anatomic dissection of 15 nonpaired fresh-frozen cadaveric knees. Quantitative anatomic relationships were calculated using a 3-dimensional coordinate measuring device. Measurements on anteroposterior (AP) and lateral radiographs were obtained by use of a picture archiving and communications system program. Structural properties were characterized during a single pull-to-failure test using a tensile testing machine. All anatomic, radiographic, and biomechanical measurements were reported as mean values and 95% CIs. Results: The ALL was identified as a thickening of the lateral capsule coming under tension with an applied internal rotation at 30° of flexion. Its femoral attachment was located 4.7 mm (95% CI, 3.5-5.9 mm) posterior and proximal to the fibular collateral ligament attachment and coursed anterodistally to its anterolateral tibial attachment approximately midway between the center of the Gerdy tubercle and the anterior margin of the fibular head; the tibial attachment was located 24.7 mm (95% CI, 23.3-26.2 mm) and 26.1 mm (95% CI, 23.9-28.3 mm) from each structure, respectively. On the AP radiographic view, the ALL originated on the femur 22.3 mm (95% CI, 20.7-23.9 mm) proximal to the joint line and inserted on the tibia 13.1 mm (95% CI, 12.3-13.9 mm) distal to the lateral tibial plateau. On the lateral view, the femoral attachment was 8.4 mm (95% CI, 6.8-10.0 mm) posterior and proximal to the lateral epicondyle. The tibial attachment was 19.0 mm (95% CI, 17.1-20.9 mm) posterior and superior to the center of the Gerdy tubercle. The mean maximum load was 175 N (95% CI, 139-211 N) and the stiffness was 20 N/mm (95% CI, 16-25 N/mm). Failure occurred by 4 distinct mechanisms: ligamentous tear at the femoral (n = 4) or tibial (n = 1) attachment, midsubstance tear (n = 4), and bony avulsion of the tibial attachment (Segond fracture; n = 6). Conclusion: Defined ALL attachment locations can be reproducibly identified with intraoperative landmarks or radiographs. The biomechanical analysis suggests that most traditional soft tissue grafts are sufficient for ALL reconstruction. Clinical Relevance: The ALL was consistently found in all knees. Segond fractures appear to occur primarily from the avulsion of the ALL.

Medial Knee Injury: Part 1, Static Function of the Individual Components of the Main Medial Knee Structures

Background There is a lack of knowledge on the primary and secondary static stabilizing functions of the posterior oblique ligament (POL), the proximal and distal divisions of the superficial medial collateral ligament (sMCL), and the meniscofemoral and meniscotibial portions of the deep medial collateral ligament (MCL). Hypothesis Identification of the primary and secondary stabilizing functions of the individual components of the main medial knee structures will provide increased knowledge of the medial knee ligamentous stability. Study Design Descriptive laboratory study. Methods Twenty-four cadaveric knees were equally divided into 3 groups with unique sequential sectioning sequences of the POL, sMCL (proximal and distal divisions), and deep MCL (meniscofemoral and meniscotibial portions). A 6 degree of freedom electromagnetic tracking system monitored motion after application of valgus loads (10 N·m) and internal and external rotation torques (5 N·m) at 0°, 20°, 30°, 60°, and 90° of knee flexion. Results The primary valgus stabilizer was the proximal division of the sMCL. The primary external rotation stabilizer was the distal division of the sMCL at 30° of knee flexion. The primary internal rotation stabilizers were the POL and the distal division of the sMCL at all tested knee flexion angles, the meniscofemoral portion of the deep MCL at 20°, 60°, and 90° of knee flexion, and the meniscotibial portion of the deep MCL at 0° and 30° of knee flexion. Conclusion An intricate relationship exists among the main medial knee structures and their individual components for static function to applied loads. Clinical Significance: Interpretation of clinical knee motion testing following medial knee injuries will improve with the information in this study. Significant increases in external rotation at 30° of knee flexion were found with all medial knee structures sectioned, which indicates that a positive dial test may be found not only for posterolateral knee injuries but also for medial knee injuries.

Injuries to the Medial Collateral Ligament and Associated Medial Structures of the Knee

*The superficial medial collateral ligament and other medial knee stabilizers-i.e., the deep medial collateral ligament and the posterior oblique ligament-are the most commonly injured ligamentous structures of the knee. *The main structures of the medial aspect of the knee are the proximal and distal divisions of the superficial medial collateral ligament, the meniscofemoral and meniscotibial divisions of the deep medial collateral ligament, and the posterior oblique ligament. *Physical examination is the initial method of choice for the diagnosis of medial knee injuries through the application of a valgus load both at full knee extension and between 20 degrees and 30 degrees of knee flexion. *Because nonoperative treatment has a favorable outcome, there is a consensus that it should be the first step in the management of acute isolated grade-III injuries of the medial collateral ligament or such injuries combined with an anterior cruciate ligament tear. *If operative treatment is required, an anatomic repair or reconstruction is recommended.

Arthroscopically Pertinent Landmarks for Tunnel Positioning in Single-Bundle and Double-Bundle Anterior Cruciate Ligament Reconstructions

Background: Quantification of the overall anterior cruciate ligament (ACL) and anteromedial (AM) and posterolateral (PL) bundle centers in respect to arthroscopically pertinent bony and soft tissue landmarks has not been thoroughly assessed. Hypothesis: A standardized anatomical measurement method can quantitate the locations of the ACL and AM and PL bundle centers in reference to each other and anatomical landmarks. Study Design: Descriptive laboratory study. Methods: Quantification of the ACL and its bundle attachments was performed on 11 cadaveric knees using a radio frequency-tracking device. Results: The tibial ACL attachment center was 7.5 mm medial to the anterior horn of the lateral meniscus, 13.0 mm anterior to the retro-eminence ridge, and 10.5 mm posterior to the ACL ridge. The femoral ACL attachment center was 1.7 mm proximal to the bifurcate ridge and 6.1 mm posterior to the lateral intercondylar ridge. The tibial AM attachment center was 8.3 mm medial to the anteromedial aspect of the lateral meniscus anterior horn, 17.8 mm anterior to the retro-eminence ridge, and 5.6 mm posterior to the ACL ridge. The femoral AM attachment center was 4.8 mm proximal to the bifurcate ridge and 7.1 mm posterior to the lateral intercondylar ridge. The tibial PL bundle attachment center was 6.6 mm medial to the posteromedial aspect of the lateral meniscus anterior horn, 10.8 mm anteromedial to the root attachment of the lateral meniscus posterior horn, and 8.4 mm anterior to the retro-eminence ridge. The femoral PL bundle attachment center was 5.2 mm distal to the bifurcate ridge and 3.6 mm posterior to the lateral intercondylar ridge. Conclusion: The authors developed a comprehensive compilation of measurements of arthroscopically pertinent bony and soft tissue landmarks that quantitate the ACL and its individual bundle attachment centers on the tibia and femur. Clinical Relevance: These clinically relevant arthroscopic landmarks may enhance single- and double-bundle ACL reconstructions through improved tunnel placement.

Force Measurements on the Posterior Oblique Ligament and Superficial Medial Collateral Ligament Proximal and Distal Divisions to Applied Loads

Background There is limited information regarding load responses of the posterior oblique and superficial medial collateral ligaments to applied loads. Hypotheses The degree of knee flexion affects loads experienced by the posterior oblique ligament and both divisions of the superficial medial collateral ligament. The posterior oblique ligament provides significant resistance to valgus and internal rotation forces near knee extension. Different load responses are experienced by proximal and distal divisions of the superficial medial collateral ligament. Study Design Descriptive laboratory study. Methods Twenty-four nonpaired, fresh-frozen cadaveric knees were tested. Buckle transducers were applied to the proximal and distal divisions of the superficial medial collateral and posterior oblique ligaments. Applied loads at 0°, 20°, 30°, 60°, and 90° of knee flexion consisted of 10 N.m valgus loads, 5 N .m internal and external rotation torques, and 88 N anterior and posterior drawer loads. Results External rotation torques produced a significantly higher load response on the distal superficial medial collateral ligament than did internal rotation torques at all flexion angles with the largest difference at 90° (96.6 vs 22.5 N). For an applied valgus load at 60° of knee flexion, loads on the superficial medial collateral ligament were significantly higher in the distal division (103.5 N) than the proximal division (71.9 N). The valgus load response of the posterior oblique ligament at 0° of flexion (19.1 N) was significantly higher than at 30° (10.6 N), 60° (7.8 N), and 90° (6.8 N) of flexion. At 0° of knee flexion, the load response to internal rotation on the posterior oblique ligament (45.8 N) was significantly larger than was the response on both divisions of the superficial medial collateral ligament (20 N for both divisions). At 90° of flexion, the load response to internal rotation torques reciprocated between these structures with a significantly higher response in the distal superficial medial collateral ligament division (22.5 N) than the posterior oblique ligament (9.1 N). Conclusion The superficial medial collateral ligament experienced the largest load response to applied valgus and external rotation torques; the posterior oblique ligament observed the highest load response to internal rotation near extension. Clinical Relevance This study provides new knowledge of the individual biomechanical function of the main medial knee structures in an intact knee and will assist in the interpretation of clinical knee motion testing and provide evidence for techniques involving repair or reconstruction of the posterior oblique ligament and both divisions of the superficial medial collateral ligament.

Qualitative and Quantitative Anatomic Analysis of the Posterior Root Attachments of the Medial and Lateral Menisci

Background: The clinical importance of the meniscal posterior root attachments has been recently reported by both biomechanical and clinical studies. Although several studies have been performed to evaluate surgical techniques, there have been few studies on the quantitative arthroscopically pertinent anatomy of the posterior meniscal root attachments. Hypothesis: The posterior root attachments of the medial and lateral menisci are consistent among specimens, and repeatable quantitative measurements using arthroscopically pertinent landmarks are achievable. Study Design: Descriptive laboratory study. Methods: Twelve nonpaired, fresh-frozen cadaveric knees were used. The positions of the posterior root attachments of the medial and lateral menisci were identified, and 3-dimensional measurements to arthroscopically pertinent landmarks were performed using a coordinate measuring system. Results: The direct distance (±standard error of the mean) between the medial tibial eminence apex and the medial meniscus posterior root attachment center was 11.5 (±0.9) mm. When split into directional components along the knee’s main axes, the medial meniscus posterior root attachment center was 9.6 (±0.8) mm posterior and 0.7 (±0.4) mm lateral along the bony surface from the medial tibial eminence apex. It was located 3.5 (±0.4) mm lateral from the medial articular cartilage inflection point and directly 8.2 (±0.7) mm from the nearest tibial attachment margin of the posterior cruciate ligament. The direct distance between the lateral tibial eminence apex and the lateral meniscus posterior root attachment center was 5.3 (±0.3) mm. When it was split into directional components using the knee’s main axes, the lateral meniscus posterior root attachment center was 4.2 (±0.4) mm medial and 1.5 (±0.7) mm posterior from the lateral tibial eminence apex. The lateral meniscus posterior root attachment center was located 4.3 (±0.5) mm medial from the nearest articular cartilage margin and directly 12.7 (±1.1) mm from the nearest margin of the tibial attachment of the posterior cruciate ligament. Conclusion: This quantitative study reproducibly identified the posterior root attachment centers of the medial and lateral menisci in relation to arthroscopically pertinent landmarks and guidelines. Clinical Relevance: These data can be directly applied to assist in anatomic meniscal root repairs.

Radiographic Identification of the Primary Medial Knee Structures

BACKGROUND Radiographic landmarks for medial knee attachment sites during anatomic repairs or reconstructions are unknown. If identified, they could assist in the preoperative evaluation of structure location and allow for postoperative assessment of reconstruction tunnel placement. METHODS Radiopaque markers were implanted into the femoral and tibial attachments of the superficial medial collateral ligament and the femoral attachments of the posterior oblique and medial patellofemoral ligaments of eleven fresh-frozen, nonpaired cadaveric knee specimens. Both anteroposterior and lateral radiographs were made. Structures were assessed within quadrants formed by the intersection of reference lines projected on the lateral radiographs. Quantitative measurements were performed by three independent examiners. Intraobserver reproducibility and interobserver reliability were determined with use of intraclass correlation coefficients. RESULTS The overall intraclass correlation coefficients for intraobserver reproducibility and interobserver reliability were 0.996 and 0.994, respectively. On the anteroposterior radiographs, the attachment sites of the superficial medial collateral ligament, posterior oblique ligament, and medial patellofemoral ligament were 30.5 +/- 2.4 mm, 34.8 +/- 2.7 mm, and 42.3 +/- 2.1 mm from the femoral joint line, respectively. On the lateral femoral radiographs, the attachment of the superficial medial collateral ligament was 6.0 +/- 0.8 mm from the medial epicondyle and was located in the anterodistal quadrant. The attachment of the posterior oblique ligament was 7.7 +/- 1.9 mm from the gastrocnemius tubercle and was located in the posterodistal quadrant. The attachment of the medial patellofemoral ligament was 8.9 +/- 2.0 mm from the adductor tubercle and was located in the anteroproximal quadrant. On the lateral tibial radiographs, the proximal and distal tibial attachments of the superficial medial collateral ligament were 15.9 +/- 5.2 and 66.1 +/- 3.6 mm distal to the tibial inclination, respectively. CONCLUSIONS The attachment locations of the main medial knee structures can be qualitatively and quantitatively correlated to osseous landmarks and projected radiographic lines, with close agreement among examiners.

Altered Tibiofemoral Contact Mechanics Due to Lateral Meniscus Posterior Horn Root Avulsions and Radial Tears Can Be Restored with in Situ Pull-Out Suture Repairs

BACKGROUND An avulsion of the posterior root attachment of the lateral meniscus or a radial tear close to the root attachment can lead to degenerative knee arthritis. Although the biomechanical effects of comparable injuries involving the medial meniscus have been studied, we are aware of no such study involving the lateral meniscus. We hypothesized that in situ pull-out suture repair of lateral meniscus root avulsions and of complete radial tears 3 and 6 mm from the root attachment would increase the contact area and decrease mean and peak tibiofemoral contact pressures, at all knee flexion angles, relative to the corresponding avulsion or tear condition. METHODS Eight human cadaveric knees underwent biomechanical testing. Eight lateral meniscus conditions (intact, footprint tear, root avulsion, root avulsion repair, radial tears at 3 and 6 mm from the posterior root, and repairs of the 3 and 6-mm tears) were tested at five different flexion angles (0°, 30°, 45°, 60°, and 90°) under a compressive 1000-N load. RESULTS Avulsion of the posterior root of the lateral meniscus or an adjacent radial tear resulted in significantly decreased contact area and increased mean and peak contact pressures in the lateral compartment, relative to the intact condition, in all cases except the root avulsion condition at 0° of flexion. In situ pull-out suture repair of the root avulsion or radial tear significantly reduced mean contact pressures, relative to the corresponding avulsion or tear condition, when the results for each condition were pooled across all flexion angles. CONCLUSIONS Posterior horn root avulsions and radial tears adjacent to the root attachment of the lateral meniscus significantly increased contact pressures in the lateral compartment. In situ pull-out suture repairs of these tears significantly improved lateral compartment joint contact pressures. CLINICAL RELEVANCE In situ repair may be an effective treatment to improve tibiofemoral contact profiles after an avulsion of the posterior root of the lateral meniscus or a complete radial tear adjacent to the root. In situ repairs should be further investigated clinically as an alternative to partial lateral meniscectomy.

An In Vitro Analysis of an Anatomical Medial Knee Reconstruction

Background An anatomical medial knee reconstruction has not been described in the literature. Hypothesis Knee stability and ligamentous load distribution would be restored to the native state with an anatomical medial knee reconstruction. Study Design Controlled laboratory study. Methods Ten nonpaired cadaveric knees were tested in the intact, superficial medial collateral ligament and posterior oblique ligament—sectioned, and anatomically reconstructed states. Each knee was tested at 0°, 20°, 30°, 60°, and 90° of knee flexion with a 10-N·m valgus load, 5-N·m external and internal rotation torques, and 88-N anterior and posterior drawer loads. A 6 degrees of freedom electromagnetic motion tracking system measured angulation and displacement changes of the tibia with respect to the femur. Buckle transducers measured the loads on the intact and reconstructed proximal and distal divisions of the superficial medial collateral ligament and the posterior oblique ligament. Results A significant increase was found in valgus angulation and external rotation after sectioning the medial knee structures at all tested knee flexion angles. This was restored after an anatomical medial knee reconstruction. The authors also found a significant increase in internal rotation at 0°, 20°, 30°, and 60° of knee flexion after sectioning the medial knee structures, which was restored after the reconstruction. A significant increase in anterior translation was observed after sectioning the medial knee structures at 20°, 30°, 60°, and 90° of knee flexion. This increase in anterior translation was restored following the reconstruction at 20° and 30° of knee flexion, but was not restored at 60° and 90°. A small, but significant, increase in posterior translation was found after sectioning the medial knee structures at 0° and 30° of knee flexion, but this was not restored after the reconstruction. Overall, there were no clinically important differences in observed load on the ligaments when comparing the intact with the reconstructed states for valgus, external and internal rotation, and anterior and posterior drawer loads. Conclusion An anatomical medial knee reconstruction restores near-normal stability to a knee with a complete superficial medial collateral ligament and posterior oblique ligament injury, while avoiding overconstraint of the reconstructed ligament grafts. Clinical Significance This anatomical medial knee reconstruction technique provides native stability and ligament load distribution in patients with chronic or severe acute medial knee injuries.

Femoral Cortical Suspension Devices for Soft Tissue Anterior Cruciate Ligament Reconstruction A Comparative Biomechanical Study

Background: Optimization of anterior cruciate ligament (ACL) fixation is desired to improve graft healing. New soft tissue cortical suspension devices for femoral tunnel fixation should be biomechanically evaluated. Hypothesis: All femoral fixation devices would prevent a clinically significant amount of displacement and support loads significantly larger than in situ forces experienced by the ACL during early rehabilitation. Study Design: Controlled laboratory study. Methods: Four cortical soft tissue ACL graft suspension devices were tested under cyclic and pull-to-failure loading conditions in both an isolated device-only setup and as a complete bone-device-tendon construct in porcine femurs using a tensile testing machine. Results: There were significant differences in the ultimate failure loads among the devices. The highest ultimate failure loads when tested as a construct were observed for the XO Button (1748 N), followed by the Endobutton CL (1456 N), ToggleLoc with ZipLoop (1334 N), and TightRope RT (859 N). Cyclic displacement after 1000 cycles during isolated device testing was less than 1 mm for all devices. Cyclic displacements after 1000 cycles in the porcine construct were 1.88 mm, 2.74 mm, 3.34 mm, and 1.82 mm for the Endobutton, TightRope, ToggleLoc, and XO Button, respectively; all were significantly different from each other except when the Endobutton was compared with the XO Button. The ToggleLoc exceeded the 3.0-mm displacement threshold defined as a clinical failure. The most displacement occurred during the first cycle, especially for the adjustable-length loop devices. Stiffness reapproximated the native ACL stiffness for all constructs. Conclusion: The Endobutton, TightRope, and XO Button have the necessary biomechanical properties with regard to ultimate failure strength, displacement, and stiffness for initial fixation of soft tissue grafts in the femoral tunnel for ACL reconstruction. The ToggleLoc had sufficient ultimate failure strength but crossed our 3.0-mm clinical failure threshold for cyclic displacement. Although this study was not designed to compare fixed and adjustable-length loop devices, it was noted that both fixed-loop devices allowed less cyclic displacement and initial displacement. Clinical Relevance: Adjustable-length loop devices may need to be retensioned after cycling the knee and fixing the tibial side to account for the increased initial displacement seen with these devices.