Editorial Commentary: Measuring Coronal (Mal)Alignment for Patients With Patellar Instability: Tibial Tubercle-to-Trochlear Groove Versus Tibial Tubercle-to-Posterior Cruciate Ligament Distance

Abstract

Excessive lateralization of the tibial tuberosity is one of the anatomic factors that contribute to lateral patellar instability, which we usually correct surgically with tibial tuberosity osteotomy. Traditionally, coronal alignment was determined clinically by measuring the Q angle, which has proven to be unreliable. Radiographic measurements of coronal alignment made using computed tomography and magnetic resonance imaging are more reliable and have become the standard for determining the need for corrective tibial tuberosity osteotomy. However, measurements of the distance between the tibial tuberosity and the trochlear groove vary substantially according to the imaging modality, knee-flexion angle, and other factors. An alternative approach is to measure the distance between the tibial tuberosity and the posterior cruciate ligament, which negates the confounding influence of the knee-flexion angle. Controversy remains as to the optimum measurement technique. It is crucial that knee surgeons understand the nuances of the technique used to measure coronal alignment so they can choose the optimum surgery to achieve the desired anatomic correction.