In patients with patellar instability tibial tubercle-trochlear grout distance relationship with patella height

Purpose: The diagnosis and treatment of patellofemoral disorders remain subjects of ongoing debate. Patellofemoral instability necessitates a comprehensive, individualized evaluation of numerous parameters due to the complex anatomy of the patellofemoral joint. In our study, following Dejour's objective definition of patellar instability, we aimed to investigate the relationship between the tibial tuberosity-trochlear groove(TT-TG) distance and patella alta in patients with and without objective patellar instability. Patients and Methods: We assessed the TT-TG distance, trochlear dysplasia, facet asymmetry, and axial engagement index in patients with and without objective patellar instability using MRI imaging. We evaluated the interrelationships among these parameters and their potential effects on the patellofemoral joint based on our findings, aiming to provide guidance to prevent acute and long-term adverse outcomes. We organized two patient groups for our study: one with objective patellar instability and the other without. The group with objective patellar instability included 32 patients, comprising 20 females and 12 males. Each of these patients had a history of at least one dislocation event. According to Dejour's criteria, a significant factor in patients with objective patellar instability was the presence of patella alta. In the group without objective patellar instability, none of the individuals exhibited patella alta. In the group without objective patellar instability, there were 39 individuals, comprising 21 females and 18 males. Both groups were similar in terms of age and gender distribution. Our study is retrospective. magnetic resonance imaging(MRI) scans of the knee were performed for both groups using a 1.5 Tesla MRI scanner. Measurements of TT-TG distance, trochlear dysplasia, facet asymmetry, and axial engagement index were taken by establishing reference points and were conducted using the PACS v4.1.2.22 application. Results: No significant difference was found in age, gender, and side between the two groups. Significant differences were observed between the groups in terms of TT-TG distance, trochlear dysplasia (TD), facet asymmetry, and axial engagement index (AEI). In the multivariate logistic regression analysis, facet asymmetry (%) had a significant and independent effect in distinguishing between the two patient groups. A significant efficacy of increased TT-TG distance was observed in differentiating patients with and without objective patellar instability. A negative correlation exists between TT-TG distance and facet asymmetry. Conclusion: In patients with objective patellar instability and patella alta, an increase in the TT-TG distance was often noted. Facet asymmetry emerged as the most significant value in patients with objective patellar instability. An increase in TT-TG distance has led to a decrease in the percentage of trochlear facet asymmetry. Trochlear facet asymmetry may be one of the major factors of patellofemoral instability. Further studies are needed to investigate the impact of trochlear facet asymmetry on patellofemoral instability. Keywords: Patella alta, objective patellar instability, TT-TG distance, Trochlear facet asymmetry