Editorial Commentary: Sagittal Tibial Tubercle-Trochlear Groove Distance Refines Patellar Instability Phenotyping but Should Not Yet Dictate Surgical Correction.

Patellofemoral instability is a 3-dimensional disorder, yet surgical planning remains dominated by axial and coronal measurements. Recent literature reports that greater preoperative sagittal tibial tubercle-trochlear groove (sTT-TG) distance was associated with better quality of life, less pain, and better function after combined sulcus-deepening trochleoplasty and medial patellofemoral ligament reconstruction in patients with high-grade trochlear dysplasia. The finding is compelling because trochleoplasty directly modifies the femoral landmark used to calculate sTT-TG. A greater sTT-TG may, therefore, identify an instability phenotype, particularly responsive to surgical correction of the sagittal mismatch, whether through posteriorization of the trochlear floor during sulcus-deepening trochleoplasty or anteriorization of the tibial tubercle. However, the models explained little outcome variance, postoperative sTT-TG was not measured, the measurement is influenced by tibiofemoral rotation and imaging technique, and nearly 1 in 5 patients also underwent tibial tubercle osteotomy. These limitations preclude definitive conclusions regarding the mechanistic or therapeutic relevance of sTT-TG in the setting of trochleoplasty. At present, sTT-TG should become a part of comprehensive patellar instability phenotyping, but it should not yet independently dictate the indication, procedure, or magnitude of surgical correction.