Lorenzo Nardo, Presenter: Nothing to Disclose

David Nathan Sandman MD, Abstract Co-Author: Nothing to Disclose

Warapat Virayavanich, Abstract Co-Author: Nothing to Disclose

Michele Guindani PhD, Abstract Co-Author: Nothing to Disclose

Lynne S. Steinbach MD, Abstract Co-Author: Research Consultant, Pfizer pharmaceuticals

Thomas M. Link MD, PhD, Abstract Co-Author: Consultant, General Electric Company

To describe the MR imaging findings of disuse osteopenia (DO) in the knee joints of patients that were immobilized for the last 4-12 weeks.

MRI knee examinations in 53 patients (24 men, 29 women, aged 18-65 years) were performed following 4 to 12 weeks of ipsilateral lower extremity immobilization therapy for ACL injuries (28), ankle/foot fractures (15), ankle tendon injuries (7) and metatarsal osteotomies (3). Using fat-suppressed, fluid sensitive, intermediate-weighted sequences, bone marrow signal abnormalities were analyzed by 2 radiologists and scored according to 1) severity of signal abnormalities, 2) signal intensity relative to cartilage, 3) morphology, and 4) degree of increased intraosseous focal signal in the distal femur and proximal tibia epiphysis and metaphysis as well as the patella. In addition to Pearson’s chi-square test, Spearman rank correlation test and Kendall’s tau comparing individual scores using a p<0.05 level of confidence, Cohen’s Kappa values were calculated for intraobserver and interobserver agreement.

All 53 patients presented abnormal bone marrow findings in the femur epiphysis. T2 hyperintense signal abnormalities were significantly more severe in the subchondral and intramedullary compartments of the femoral epiphysis and in the patellar intracortical compartments, than in other compartments (Pearson’s chi-square test; p=0.0024). High scores of severity were associated with confluent and patchy signal patterns (Spearman rank correlation and Kendall’s tau; p<0.0001). Increased focal signal abnormalities suggestive of increased vascularity were noted in the intracortical compartments of the femoral and the tibial metaphyses and patella in 33% of the cases. Weighted Cohen’s Kappa values for intraobserver and interobserver agreement of the scoring system were 0.79 and 0.68, respectively.  

DO manifestations in the knee on fat-suppressed fluid sensitive sequences were most prevalent and severe in the distal femoral epiphysis where both confluent and patchy hyperintense patterns predominated. In addition findings suggestive of increased intracortical vascularity were observed in the patella.

Radiologists need to be familiar with the specific MRI pattern associated with DO to differentiate this from other bone marrow abnormalities.

Nardo, L, Sandman, D, Virayavanich, W, Guindani, M, Steinbach, L, Link, T, MRI Findings of Disuse Osteopenia.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11014139.html