Defining the width of the normal tibial plateau relative to the distal femur: Critical normative data for identifying pathologic widening in tibial plateau fractures.

Tibial plateau widening in the setting of fracture is an indication for surgical treatment, and restoring width is an important goal of surgery. In order to identify and correct pathological widening, the width of the normal tibial plateau must first be defined. The aim of this study was to establish normative data for the width of the tibial plateau relative to the distal femur to enable surgeons to identify and correct pathological widening in the setting of tibial plateau fracture. Fifty-one uninjured anteroposterior (AP) knee radiographs and 11 XR and CT scans of lateral tibial plateau fractures were retrospectively reviewed. The distances measured included maximal distal femoral width, femoral articular width, tibial articular width, and lateral plateau widening. On average, lateral plateau widening was +0.02 ± 2.03 mm, indicating that the most lateral aspect of the tibial plateau is collinear with the most lateral aspect of the lateral epicondyle of the femur. In the fracture population, average widening was 7.13 ± 3.59 mm on XR and 6.57 ± 3.34 mm on CT, with an absolute difference between XR and CT of 1.19 ± 0.66 mm. In conclusion, this study is the first to define the radiographic anatomy of the proximal tibia quantitatively. In the setting of tibial plateau fracture, residual widening of 2.1 mm could be within normal variation. However, the authors consider widening >2.1 mm pathological. These values can be used for assessing pathological widening of tibial plateau fractures. Clin. Anat. 31:688-692, 2018.