Morphology of the femoral insertion of the lateral collateral ligament and popliteus tendon.

PURPOSE: To clarify the femoral insertion of the lateral collateral ligament (LCL) and popliteus tendon (PT) and related osseous landmarks on three-dimensional images. METHODS: Twenty-six non-paired, formalin-fixed human cadaveric knees were evaluated in this study. Femoral insertion of the LCL and PT was identified and marked. Three-dimensional images were created, and the surface area, location, positional relationships, and morphology of the femoral insertion of the LCL, PT, and related osseous structures were analysed. RESULTS: The mean surface areas of the LCL and PT femoral insertions were 55.8 ± 25.0 and 52.5 ± 24.2 mm(2), respectively. Variations in the positional relationships between the LCL and PT insertions (PT inserted parallel and posterior to the LCL insertion to the long axis of the femur) were observed. The lateral epicondyle and popliteal sulcus could be clearly identified as osseous landmarks on three-dimensional images in all knees. Most of the LCL was inserted postero-distal to the apex of the lateral epicondyle, and the PT was inserted at the anterior end of the popliteal sulcus in all knees. CONCLUSION: We observed variation in the positional relationship between the femoral insertion of the LCL and PT. However, the relationships between their insertions and osseous landmarks were consistent. The findings of this study contribute to the understanding of the PLC osseous anatomy and should assist surgeons in performing PLC surgery with a more anatomic perspective.

Ribbon like appearance of the midsubstance fibres of the anterior cruciate ligament close to its femoral insertion site: a cadaveric study including 111 knees.

PURPOSE: Recently, the configuration of the anterior cruciate ligament (ACL) from its direct femoral insertion to midsubstance was found to be flat. This might have an important impact for anatomical ACL reconstruction. The purpose of this anatomical study was to evaluate the macroscopic appearance of the ACL from femoral to midsubstance. METHODS: The ACL was dissected in 111 human fresh frozen cadaver knees from its femoral insertion to midsubstance, and the shape was described. The anatomical findings were documented on digital photographs and on video. Thirty knees were sent for computed tomography (CT), magnetic resonance imaging (MRI) and histology of the femoral ACL insertion. RESULTS: Two millimetres from its direct femoral insertion, the ACL fibres formed a flat ribbon in all dissected knees without a clear separation between AM and PL bundles. The ribbon was in exact continuity of the posterior femoral cortex. The width of the ribbon was between 11.43 and 16.18 mm and the thickness of the ACL was only 2.54-3.38 mm. 3D CT, MRI and the histological examination confirmed above findings. CONCLUSION: This is a detailed anatomical study describing the ribbon-like structure of the ACL from its femoral insertion to midsubstance. A key point was to carefully remove the surface fibrous membrane of the ACL. A total of 2-3 mm from its bony femoral insertion, the ACL formed a flat ribbon without a clear separation between AM and PL bundles. The ribbon was in exact continuity of the posterior femoral cortex. The findings of a flat ligament may change the future approach to femoral ACL footprint and midsubstance ACL reconstruction and to graft selection.

Failure load of the femoral insertion site of the anterior cruciate ligament in a porcine model: comparison of different portions and knee flexion angles.

BACKGROUND: This study compared the failure load of the femoral insertion site of the anterior cruciate ligament between different portions and knee flexion angles. METHODS: In total, 87 fresh-frozen, porcine knees were used in this study. Three knees were used for histological evaluation; the remaining 84 knees were randomly divided into 4 groups: anterior anteromedial bundle, posterior anteromedial bundle, anterior posterolateral bundle, and posterior posterolateral bundle groups (n=21 per group). The anterior cruciate ligament femoral insertion site was divided into these four areas and excised, leaving a 3-mm square attachment in the center of each bundle. Tibia-anterior cruciate ligament-femur complexes were placed in a material testing machine at 30°, 120°, and 150° of knee flexion (n=7), and the failure load for each portion was measured under anterior tibial loading (0.33 mm/s). RESULTS: Histological study showed that the anterior cruciate ligament femoral insertion site consisted of direct and indirect insertions. Comparison of the failure load between the knee flexion angles revealed that all the failure loads decreased with knee flexion; significant decreases were observed in the failure load between 30 and 150° knee flexion in the posterior anteromedial bundle and posterior posterolateral bundle groups. Comparison of the failure load according to different portions revealed a significant difference between the anteromedial and posterolateral bundle groups at 150° of knee flexion, but no significant difference among the groups at 30° of flexion. CONCLUSIONS: Although the failure load of the posterior portion decreased significantly in the knee flexion position, it (mainly consisting of indirect insertion) plays a significant role against anterior tibial load in the knee extension position; this appears to be related to the characteristics of the insertion site. Reflecting the complex structure and function of the ACL, this study showed that the failure load of the femoral insertion site varies with differences in positions and knee flexion angles.