P042 Beyond synovitis: recognising methotrexate osteopathy

Background/Aims There is increasing understanding of methotrexate-related stress fractures (methotrexate osteopathy, MTXO). The following should be fulfilled for diagnosis: (1) prolonged methotrexate use, (2) typical appearance of incomplete fracture with band-like fracture lines along the growth plate, (3) anatomical location, including metaphysis of distal or proximal tibia, distal femur, calcaneus and talus, and (4) low-impact fractures. Common fracture sites are: distal tibia (70%), calcaneus (70%), proximal tibia (36%), talus (33%), and distal femur (21%). Methods Case 1: A 60-year-old female on MTX 25mg weekly for psoriatic arthritis (PsA) for 7 years developed right knee pain. MRI revealed proximal tibial stress fractures. Vitamin D, CRP, alkaline phosphatase (ALP)-normal. Time to diagnosis 24 months. MTX was stopped. MRI left knee also showed proximal tibial fractures. Case 2: A 61-year-old female on MTX 25mg for 4 years for PsA developed right ankle pain. MRI showed stress fractures in calcaneus and talus and distal tibia. Vitamin D, CRP normal, ALP-158. Time to diagnosis 19 months. MTX was stopped. Pain resolved within 4 months. Case 3: A 61-year-old female on MTX 25mg weekly for 3.5 years for psoriasis developed bilateral ankle pain. MRI confirmed fractures in distal tibia and calcaneus bilaterally, in talus and cuboids on right. Vitamin D, CRP normal, ALP-170. Time to diagnosis 24 months. MTX was stopped. Further MRI revealed fractures in proximal tibia in left knee; distal femur, medial plateau and femoral condyle in right knee. She was treated with teriparatide. Results None were on glucocorticoids nor had osteoporosis. Unaware of MTXO, case 1 underwent open reduction and internal fixation. She was subsequently treated with teriparatide injections. Misdiagnosing joint swelling and pain as a flare of arthritis with continuation of methotrexate led to a significant delay in diagnosis. Osteoporosis may coexist; however, the mechanism of fracture is different to that of MTXO. Anabolic therapy is reported to be more effective in treating MTXO. Conclusion Physicians’ awareness of MTXO is important in getting timely diagnosis to reduce further fracture risk. The most effective treatment is the cessation of methotrexate. Plain X-rays do not always show stress fractures. If doubtful, consider further imaging with MRI.