Victor Ho MD, Presenter: Nothing to Disclose

Camilo Enrique Jaimes MD, Abstract Co-Author: Nothing to Disclose

Diego Jaramillo MD, MPH, Abstract Co-Author: Nothing to Disclose

To describe MR changes of tibia, femur, menisci, and ligaments in Blount disease

We reviewed all knee MRIs showing Blount disease in the last 10 years. 17 children (10 girls, 7 boys), 2-14 years old, had 27 affected knees. We excluded 2 children (4 knees) with suboptimal studies. In the remaining 23 knees, two observers graded by consensus abnormalities of signal intensity (SI) and morphology of menisci, ligaments, femur and tibia. We performed independent readings to assess interobserver variability. We retrieved age, gender, race and BMI. 15 children were used as age-matched controls.

Thirteen children (86%) were Black. 8(53%) had bilateral deformities (7 girls, 1 boy). Of 11 children with available BMI data, 9(81%) had BMIs over the 95th percentile (mean: 31.03 kg/m2). In the tibia MRI showed high T2 SI in the medial metaphysis (n=21, 91%); medial physeal closure (n=18, 78%); or medial physeal widening (n=5, 22%); lateral physeal widening (n=8, 34%); medial perichondral deformity (n=8, 78%); irregular medial epiphyseal contour (n=16; 69%); and abnormal SI in the cartilaginous epiphysis (n= 20, 86%). Ten cartilaginous epiphyses had a unique mottled appearance. Size and SI of all medial menisci were increased. Mean width (18.5 mm) and height (6.4 mm) of medial menisci were greater than the corresponding lateral menisci (11.9 mm and 5.02 mm respectively. p< .001) and than the medial menisci of controls (9.5 and 4.13 mm, p< .001). There was patella alta (n= 10, 44%) and lax anterior cruciate ligaments (n=6, 26%). In the femur, the ossification center was more often irregular medially (n=9, 39%) than laterally (n=2, 9%) (p<.02); and there was medial physeal widening (n=7, 30%). All bony irregularities had adjacent epiphyseal cartilage cysts. We saw physeal widening medially (n=7, 30%) and laterally (n=6, 26%); and increased metaphyseal SI medially (n=4, 17%) and laterally (n=3, 13%). All patients with femoral epiphyseal abnormalities had medial tibial physeal bridging. Overall interobserver agreement was excellent (k=0.76).  

Blount disease involves many structures beyond the tibia in the medial compartment of the knee.

Blount disease is a developmental abnormality resulting in tibial deformity and genu varum. Although the radiographic abnormalities have been described, the MR characteristics are not well established

Ho, V, Jaimes, C, Jaramillo, D, MR Imaging Findings of Blount Disease.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11034601.html