Lorell Ruiz-Flores MD, Presenter: Nothing to Disclose

J. Herman Kan MD, Abstract Co-Author: Nothing to Disclose

Johanna Monsalve MD, Abstract Co-Author: Nothing to Disclose

Megan May MD, Abstract Co-Author: Nothing to Disclose

Zili David Chu PhD, Abstract Co-Author: Nothing to Disclose

T2 mapping has been shown to improve detection of occult cartilage injury that may normally not be seen on conventional anatomic MRI sequences. Cartilage injuries are common in the medial patellar facet in the setting of lateral patellar dislocation (LPD), but are less common in the lateral patellar facet and trochlea. The purpose of this study is to determine the utility of T2 mapping in identifying occult lateral compartment chondral injuries in the setting of LPD in children.

This retrospective case-control study with waiver of informed consent. The study group consisted of 27 patients (11 male, 16 female, average age of 14.6 years,) who underwent MRI in the setting of LPD. All patients underwent multiplanar T2 and proton density fat saturated sequences and T2 mapping in the axial plane (Fig 1). T2 mapping sequence is a SENSE Multi-slice multi-echo sequence providing 6 echoes with TR of 2000 ms; TEs of 13*n ms, where n=1, 2, 3,4,5,6; FOV of 160 mm; voxel size of 0.29x0.29x2.5 mm3, slice gap of 0.25 mm, 10 slices, acquisition time of 5:54 minutes. To be included in the study group, patients had to have a clinical history and classic MRI findings of LPD with no cartilage injury identified in the lateral patellofemoral compartment on multiplanar proton density and T2W sequences. T2 mapping measurements of the lateral patellar and lateral trochlear facets were obtained. A control group of 27 patients with normal knee MRI’s was used for reference (14 male, 13 female, average age of 14.4 years).

Review of the T2 color maps for both LPD and normal patients show no focal areas of increased T2 values in lateral patellar or trochlear cartilage.The T2 values of the lateral patellar facet in LPD and normal patients were 35.89 +/-5.62 msec and 36.93 +/-6.77 msec, respectively (P=0.388). The T2 values of the lateral trochlear facet in LPD and normal patients were 40.97 +/-5.39 msec and 42.45 +/- 6.61 msec, respectively (P=0.205).

In the absence of anatomic cartilage injury seen on conventional MRI sequences, T2 mapping does not appear to identify additional lateral patellofemoral compartment chondral injuries in the setting of LPD in children.

Lateral patellofemoral compartment cartilage injuries are rare in LPD, and T2 mapping sequences does not identify additional cartilage injuries that are not already present on conventional cartilage MRI sequences in children.

Ruiz-Flores, L, Kan, J, Monsalve, J, May, M, Chu, Z, T2 Mapping Evaluation of Occult Lateral Patellofemoral Compartment Chondral Injury in Children with Patellar Dislocation.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14019632.html