Johanna Monsalve MD, Presenter: Nothing to Disclose

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

Lorell Ruiz-Flores MD, Abstract Co-Author: Nothing to Disclose

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

Patellofemoral maltracking may lead to superolateral Hoffa’s fat pad impingement due to asymmetric force in the lateral patellofemoral joint soft tissues during knee motion. The purpose of this study was to determine the utility of T2 mapping in identifying additional occult chondral injuries when classic imaging findings of superolateral Hoffa’s fat pad impingement were identified on conventional sports medicine knee MRI exams in children.

This was a retrospective case-control study. The study group consisted of 31 patients (8 male, 23 female, average age: 15 years) who underwent MR imaging of the knee. All children underwent multiplanar T2 and proton density sequences as well as T2 mapping sequences performed in the axial plane. 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; 160 mm FOV; voxel size of 0.29x0.29x2.5 mm3, slice gap of 0.25 mm, 10 slices, acquisition time of 5:54 minutes. Patients were included in the study population if there were features of superolateral fat pad impingement (presence of increased signal on fluid sensitive sequences in the superolateral region of Hoffa’s fat pad-Figure 1) in the absence of lateral compartment chondral injury identified on conventional anatomic MR sequences. ROI values were measured of the lateral patellar and trochlear cartilage. This was compared with a normal knee MRI population (16 male, 15 female, average age:14.5 years).

Review of the T2 color maps for both superolateral impingement and normal patients show no focal areas of increased T2 values in lateral patellar or trochlear cartilage. Lateral patellar T2 values in children with superolateral fat pad impingement and normal patients were 37.9 +/-8.1 and 36.7 +/-6.4 msec, respectively (P=0.399). Lateral trochlear T2 values in children with superolateral fat pad impingement and normal patients was 42.5 +/-4.6 and 46.2 msec, respectively (P=0.098).

T2 mapping of the lateral patellofemoral compartment in the setting of superolateral fat pad impingement does not appear to identify occult chondral injuries when conventional anatomic T2 and PDW MR sequences of cartilage are normal.

Patellar maltracking with superolateral fat pad impingement identified by MR is not associated with chondral edema identified on T2 mapping sequences in children.

Monsalve, J, Kan, J, Ruiz-Flores, L, Chu, Z, Patellofemoral Compartment T2 Mapping MRI Evaluation of Occult Chondral Injury in Children with Superolateral Fat Pad Impingement.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14045810.html