Measuring Malalignment on Imaging in the Treatment of Patellofemoral Instability.

Assessment of malalignment is an important factor in determining surgical treatment options for patellar instability. Measurement of tibial tubercle-trochlear groove (TT-TG) distance is valuable in planning surgical treatment for patellar instability, because it quantifies a component of malalignment and aids in deciding whether to perform tibial tuberosity osteotomy. In this paper we review how TT-TG distance should be understood in the context of many measurement factors to allow for an individualized procedure that addresses the specific contributors to patellar instability in each patient. Understanding the limitations of and variability in radiographic assessments of TT and TG positions can help in deciding whether to perform TT osteotomy for patellar instability.