Description
Purpose: Recently, the sagittal tibial tubercle trochlear-groove distance (sTTTG) has been identified as a risk factor for patellofemoral cartilage deterioration. As patients with trochlear dysplasia (TD) demonstrate an increased incidence of patellofemoral cartilage damage, the aim of the herein presented study is to compare the sTTTG in patients with and without TD.
Methods: All patients between January 2017 and December 2020 with high-grade TD (Dejour type B, C and D) who underwent patellar stabilizing surgery for patellar instability at a single institution were included in the current study. Patients without preoperative magnetic resonance imaging (MRI), any prior osteotomy on the affected lower extremity or cruciate ligament insufficiency were excluded. Patients who underwent knee arthroscopy for meniscal repair/debridement without any signs of TD or any of the above-mentioned criteria served as control group. Preoperative magnetic-resonance imaging (MRI) was retrospectively assessed to compare common patellofemoral anatomic parameters including patellar angle, patellar tilt, patella morphology according to Wiberg, Caton-Deschamps index (CDI), PF index, trochlear sulcus angle, sulcus depth, lateral inclination angle of the trochlea, tibiofemoral rotation, TTTG and sTTTG distance, between both groups. The sTTTG is measured as the distance between the nadir point of the cartilaginous trochlear groove and the most anterior point of the tibial tubercle on an axial MRI. Independent predictors for the sTTTG were assessed for patients with TD.
Results: Patients with high-grade TD (n=82) showed an increased patellar tilt, CDI, trochlear sulcus angle, lateral tibiofemoral rotation angle, TTTG and sTTTG (9.16 ± 4.47 mm vs. 2.66 ± 4.21 mm) compared to the control group (n=83) (p<0.001). Patellar angle, PF index, sulcus depth and lateral inclination angle of the trochlear were significantly decreased in the TD group (p<0.001). The sTTTG was similar in all TD groups (n.s.). Among patients with TD, both tibiofemoral rotation and patellar height were independent predictors of the sTTTG (p<0.05).
Conclusion: Patients with high-grade TD show not only abnormal values in common patellofemoral instability risk factors, but also a significantly increased sTTTG compared to patients without TD.
Level of Evidence: Retrospective case comparative study, III
