Part I: An anatomic-based tunnel in the fibular head for posterolateral corner reconstruction using magnetic resonance imaging

Purpose: Currently, there are no studies that clearly define a method for the placement of the fibular tunnel between the fibular collateral ligament (FCL) and popliteofibular ligament (PFL) insertions when performing an anatomic-based posterolateral corner reconstruction. The purpose of this study was to use magnetic resonance-based anatomic landmarks to describe the orientation of a fibular tunnel between the FCL and PFL insertions. Methods: Magnetic resonance imaging (MRI) of 105 patients with normal posterolateral corner knee anatomy was identified by a musculoskeletal radiologist, and the FCL and popliteofibular insertions were labelled. Three experienced providers independently evaluated the images. In the axial plane, the Cobb angle of a fibular tunnel from the FCL to the popliteofibular insertion was measured using the tibial tubercle as a reference. In the sagittal plane, the same tunnel was measured in reference to the lateral tibial plateau. Results: In the axial plane, the average Cobb angle for an anatomic-based fibular tunnel was 48.1° ± 10.7° (ICC(2,1) = 0.76, p < 0.01) externally rotated to the tibial tubercle. In the sagittal plane, the average Cobb angle for an anatomic-based fibular tunnel was 59.8° ± 11.9° (ICC(2,1) = 0.81, p < 0.01) cranial, referenced from the lateral tibial plateau. The average length of the fibular tunnel was 2.0 ± 0.4 cm (ICC(2,1) = 0.78, p < 0.01), at the point of the fibular insertion. The distance from the midpoint of the fibular tunnel to the posterolateral wall of the fibular head was 0.8 ± 0.2 cm (ICC(2,1) = 0.63, p < 0.01). Conclusions: The results of this study suggest that MRI can be used to identify the orientation between the FCL and PFL insertions to create an anatomic-based fibular tunnel, which is 50° externally rotated from the tibial tubercle in the axial plane and placed in a cranial direction of 60° relative to the lateral joint line. The clinical relevance of this study is that this information may aid surgeons in placing a fibular tunnel connecting the FCL and PFL insertions. Level of evidence: IV.