Magnetic resonance imaging and joint outcomes in boys with severe hemophilia A treated with tailored primary prophylaxis in Canada

. Background/objectives: Tailored primary prophylaxis (TPP) is a reduced-intensity treatment program for hemophiliacs with the goal of preventing arthropathy. Our primary aim was to evaluate the joint outcomes of treated subjects using magnetic resonance imaging (MRI) and physical examination as outcome measures. Methods: Ankles, elbows and knees (index joints) of 24 subjects (median [range] age at start of therapy, 1.6 [12.5] years) with severe hemophilia A enrolled in the Canadian Hemophilia Primary Prophylaxis Study (CHPS) were examined by MRI at a median age of 8.8 years (range 6.211.5 years). Subjects were treated with TPP using a recombinant factor VIII concentrate, starting once weekly and escalating in frequency and dose according to frequency of bleeding. Results: Osteochondral changes (cartilage loss/subchondral bone damage) were detected in 9% (13/140) of the index joints and 50% (12/24) of study subjects. Osteochondral changes were restricted to joints with a history of clinically reported joint bleeding. Soft tissue changes were detected in 31% (20/65) of index joints with no history of clinically reported bleeding (ankles 75% (12/16); elbows 19% (6/32); and knees 12% (2/17)). In these apparently bleed free index joints hemosiderin deposition was detected by MRI in 26% (17/65) of joints (ankles 63% (10/16); elbows 16% (5/32), and knees 12% (2/17)). Conclusion: TPP did not completely avoid the development of MRI-detected structural joint changes in hemophilic boys in this prospective study. A longer period of follow-up is required for assessment of the longitudinal course of these early changes in hemophilic arthropathy, detected using a sensitive imaging technique (MRI).