Adductor Tubercle Appears More Posterior on Radiographs of Knees With Trochlear Dysplasia.

Purpose: The purpose of this study was to compare the radiographic positions of commonly utilized landmarks for medial patellofemoral complex (MPFC) reconstruction between symptomatic and normal knees and to assess the influence of morphologic risk factors.

Methods: Three-dimensional models were created from the knees of patients with patellar instability and compared to control knees. On 3-dimensional models, the adductor tubercle, medial epicondyle, and gastrocnemius tubercle were marked. A 2-dimensional view was created from these models to simulate radiographs, and the radiographic location of each landmark was described with respect to the antero-posterior relation to the posterior cortical line and the proximal-distal relationship to the posterior condylar line. The position of each landmark was compared between symptomatic and control groups and assessed for variations in position with the severity of anatomic risk factors.

Results: A total of 40 patients were included in this study. On the 2-dimensional views, the medial epicondyle was found to be more posterior and more proximal than in the control group. The association between the severity of trochlear dysplasia and the posterior position of the adductor tubercle trended toward significance (R = 0.43, R2 = 0.18, P = .058). In symptomatic knees with trochlear dysplasia, the radiographic landmark for the medial epicondyle was posterior by 3.3 mm (P = .052), adductor tubercle by 2.7 mm (P = .009), and gastrocnemius tubercle by 3.9 mm (P = .010) when compared to symptomatic knees without dysplasia.

Conclusions: This study demonstrates that commonly utilized anatomic landmarks on the medial femur are more posterior on radiographs in knees with patellar instability when compared to normal knees. Trochlear dysplasia is associated with the radiographic landmarks of the adductor and gastrocnemius tubercles appearing 3mm posterior to those without dysplasia, and its severity is associated with increased posterior radiographic appearance of the adductor tubercle.

Level Of Evidence: Level III, Retrospective Case Control.