Evaluation of tunnel position of posterolateral corner reconstruction using 3-dimensional computed tomogram

To evaluate the isometry of different tunnel positions in posterolateral corner (PLC) reconstruction using 3-dimensional computed tomography.

In 10 fresh-frozen cadaveric knees, fibular tunnels were made from the anterodistal surface of the fibular neck to the posteroproximal fibular tip. Tibial tunnels were made from just medial to the Gerdy tubercle to a point 1 to 1.5 cm medial to the proximal tibiofibular joint. Femoral condyles were marked at 3 different locations: (1) epicondyle, (2) 5 mm distal-anterior to the epicondyle, and (3) 18 mm distal-anterior to the epicondyle. All specimens were scanned by computed tomography at different ranges of motion. Relative length changes between the tunnels were calculated by use of medical imaging software, and the center of rotation (COR) of each distal tunnel was obtained by use of a least-squares circle-fitting algorithm.

The anterior fibular tunnel to lateral epicondyle and the posterior fibular or posterior tibial tunnel to 5 mm distal-anterior to the lateral epicondyle showed the best results in terms of isometry. The COR of the posterior fibular tunnel is distal and anterior to the epicondyle, whereas the COR of the posterior tibial tunnel is distal and slightly posterior to the epicondyle (8.4 mm away from the epicondyle, with a -8.4° angle along the longitudinal axis of the femur). The COR of the anterior fibular tunnel is located posterior and distal to the epicondyle.

Contrary to our hypothesis, the distal tunnels for PLC reconstruction each have different isometric points. The isometric point of the posterior fibular tunnel is distal and anterior to the epicondyle, whereas the isometric points of the posterior tibial and anterior fibular tunnels are distal and posterior to the epicondyle.

The isometric pattern of each tunnel combination should be considered in PLC reconstruction; currently, popliteus tendon reconstruction is non-isometric.