Isometry of the lateral, posterolateral and anterolateral knee complex: a cadaveric study

Objectives: There is no consensus on the insertion points for reconstruction of lateral ligament complex injuries. The aim of this study is to evaluate the relative isometry between easily identifiable bony ridges in order to recommend adequate reconstruction of the external structures: the lateral collateral ligament, the popliteus complex and the anterolateral ligament. Methods: After dissection of the cutaneous and subcutaneous planes of six lower limbs from 3 anatomical subjects, metal markers were fixed on 7 anatomical edges of interest: no. 1: posteroproximal to the lateral epicondyle, within a bony depression - no. 2: at the tip of the lateral epicondyle - no. 3: 18 mm distal and 0.84 mm anterior to the LCL insertion - no. 4: at Gerdy’s tubercle - no. 5: at the anterior part of the fibular head - no. 6: at the posterior part of the fibular head - no. 7: at the popliteal fossa of the tibia, 10 mm medial to the proximal tibiofibular joint, and 10 mm inferior to the joint space. The distance between these points was measured with a caliper at 0, 30, 60 and 90 degrees of flexion in neutral rotation. Results: We noted a decrease in the distance between anatomic femoral and fibular LCL (pair) insertions 1-5 during flexion (63 mm ± 2.6 to 50 mm ± 4.8). The most isometric positions were identified for the following point pairs: 2-5 (57 mm ± 3.4 to 55 mm ± 3), 3-6 (60 mm ± 3.5 to 59 mm ± 3.2), 2-4 (52 mm ± 4.6 to 55 mm ± 2.7) and 3-7 (53 mm ± 6.4 to 52 mm ± 4.6). We noted no difference between knees. Conclusion: These results show that the anatomical structures are not isometric. However, some easily identifiable point pairs of the lateral aspect of the knee show an isometric feature. Therefore, we recommend using pairs 2-5 for the LCL, 2-4 for the ALL and 3-7 for the PC.