Editorial Commentary : Patellar Tendon‐Lateral Trochlear Ridge Distance May Outperform Tibial Tubercle‐Trochlear Groove for Assessing Patellar Containment, but Trochlear Dysplasia and Patellar Height Are Likely the Culprits

Abstract

Recurrent patellofemoral instability is rarely explained by a single anatomic abnormality. Trochlear dysplasia, patellar height, torsional malalignment, and a laterally directed extensor mechanism vector each independently raise the risk of dislocation, and most patients who fail nonoperative treatment carry more than one of these risk factors at once. Because surgical decision‐making increasingly depends on identifying which factors are driving a given patient's instability, the search for the best measurements to indicate surgical procedures continues to evolve. A clean, reproducible measurement that quantifies how far a patient's anatomy is pulling their patella off track would make for an ideal algorithmic approach, but these anatomic risk factors do not occur independently of one another and often are dynamically influenced by tight retinacular structures and muscle imbalances. Additionally, any comparison between risk factors measured is only as informative as the degree to which the groups being compared are otherwise anatomically alike. For example, if the patients used to validate a patellar tendon‐lateral trochlear ridge measurement also happen to carry substantially more trochlear dysplasia or patella alta than the comparison group, that measurement may appear discriminative for instability, whereas it is, in fact, reflecting those better‐established risk factors instead. It is important for these measurements to be validated in a population matched for the full pathoanatomic picture, not just age, sex, and laterality, or it will remain difficult to know whether we have identified a new risk factor or simply detected a surrogate for patellar containment in lieu of patella alta and trochlear dysplasia.