Editorial Commentary: Tibial Tubercle-Trochlear Groove Distance Should Be Prioritized Over Tibial Tubercle-Posterior Cruciate Ligament Distance, but the Source of Malalignment Must Guide Proximal or Distal Realignment

Objective patellar instability results from the interaction of multiple anatomic abnormalities, including trochlear dysplasia, patella alta, tibial tubercle lateralization, and rotational malalignment. The tibial tubercle-trochlear groove distance integrates the relation between the tibial tubercle and the femoral trochlea, whereas the tibial tubercle-posterior cruciate ligament distance is restricted to tibial landmarks. Consequently, the tibial tubercle-posterior cruciate ligament distance may underestimate the functional extensor mechanism malalignment, particularly in patients with trochlear dysplasia. In our view, the tibial tubercle-trochlear groove distance should remain the preferred measurement when planning patellofemoral realignment. Nevertheless, an elevated value should not automatically prompt tibial tubercle osteotomy because it may result from tibial tubercle lateralization, medialization of the trochlear groove, tibiofemoral rotation, or a combination of these factors. Surgical planning should therefore identify the origin of the malalignment and distinguish between proximal realignment through trochleoplasty and distal realignment through tibial tubercle osteotomy. The tibial tubercle-posterior cruciate ligament distance may complement this assessment, but it should not replace the tibial tubercle-trochlear groove distance.