Magnetic Resonance Imaging Characteristics of the Medial Patellofemoral Ligament Lesion in Acute Lateral Patellar Dislocations Considering Trochlear Dysplasia, Patella Alta, and Tibial Tuberosity–Trochlear Groove Distance

Does Landmark Selection Affect the Reliability of Tibial Tubercle-Trochlear Groove Measurements Using MRI?

“…Measuring the TT-TG distance using CT images is well established and is considered the gold standard [13,20,23,29]. Owing to better observation of soft tissues and the absence of radiation, the use of MRI to measure this distance is increasing [2,3,20,21,30], although the evidence for doing so is lacking [23]. Only one study [20] addresses the interobserver reliability of using MRI to measure this distance, but does not address intraobserver reliability.…”

“…Only one study [20] addresses the interobserver reliability of using MRI to measure this distance, but does not address intraobserver reliability. Although the landmarks chosen to measure the TT-TG using CT are more uniform [1,7,8,13,20,29], the studies using MRI to measure the lateral offset are far more variable in their choice of landmarks [2,3,20,30], creating a source of variability. Given the small difference between what is considered a normal lateral offset and what is considered pathologic distance, the reliability of the measurement must be determined before using this measurement to plan a surgical procedure.…”

“…Although measuring lateral offset of the extensor mechanism using MRI has been reported [2,3,14,20,30], the methods for doing so have not yet been validated [23,26]. One deficiency is in defining which landmarks should be chosen to measure lateral offset.…”

“…One deficiency is in defining which landmarks should be chosen to measure lateral offset. The tibial tubercle and the osseous trochlear groove are uniform landmarks in numerous studies using CT [7,12,13,16,29], but better observation of soft tissues has led to variability in landmark selection in studies using MR images [2,3,14,20,30]. One study [20] compared MR and CT images for measurement of lateral offset using traditional osseous landmarks and a more functional soft tissue landmark (the distance from the center of the patellar tendon to the trochlear groove [PT-TG]), concluding that there was no difference and that they could be used interchangeably.…”

“…Given the variability in how this distance is measured using MRI, and the insufficient evidence [23] to support its use for this purpose, we sought to (1) determine variability in the insertion of the patellar tendon relative to the tibial tubercle and how this affects measurement of the traditional TT-TG distance versus the functional PT-TG distance, (2) determine the reliability of measuring the osseous TT-TG distance, (3) determine the reliability of measuring the soft tissue PT-TG distance, and (4) compare the reliabilities of using osseous versus soft tissue landmarks.…”