Shu L, Ni Q, Yang X, et al. - A comparative study was performed to describe tibial tubercle-trochlear groove distance assessed in two ways and tibial tubercle-posterior cruciate ligament distance in patients with patellofemoral instability. Researchers conducted CT and MRI in 47 patients with or without patellofemoral instability (PFI). Two observers assessed the tibial tubercle-trochlear groove (TT-TG) distance through conventional CT and three-dimensional CT reconstruction (TDR-TT-TG) respectively and the tibial tubercle-posterior cruciate ligament distance with MRI. They applied the intraclass correlation coefficient (ICC) to analyze the interobserver reliability. They further compared the differences of three measurements between different patients. The Bland-Altman method was applied to examine the consistency of TT-TG and TDR-TT-TG. All three methods can be applied to evaluate PFI; the TDR-TT-TG measurement method has superior operability and better interobserver consistency. The results considered that it may be an alternative procedure to the conventional TT-TG distance measurement.