Recurrent lateral patella instability is primarily a result of lateral patella entry to the femoral trochlea. Using 3-D imaging, one can accurately assess this lateral entry more accurately than with plain radiographs, making 3-D imaging important for optimal surgical planning, particularly when deciding whether to do an anteromedial tibial tubercle transfer osteotomy (AMTTO). To understand the laterality of patella entry to the femoral trochlea of a patient, one must understand the patella entry zone and its midpoint, defined as the entry point (EP) to the trochlea, and then measure its coronal distance from the central femoral trochlea groove (TG)-the EP-TG distance. This fixed EP-TG distance, when considered together with the more variable (and therefore potentially misleading) TT-TG distance and patella height, provides a strong basis for surgical decision-making with regard to anteromedial tibial tubercle transfer planning.
Fulkerson et al. (Mon,) studied this question.