Abstract
A 55-year-old female with psoriatic arthritis developed left ankle pain, without preceding injury or repetitive trauma. She had psoriatic arthritis for 10 years, with subcutaneous methotrexate controlling arthritis for the past 6 years.
She had intra-articular steroids once to right shoulder and rescue intramuscular steroids twice. Her weight was 49kg. Left ankle MRI showed transverse fracture of her distal tibia. She had no risk factors for secondary osteoporosis. Her T score ranged -1.7- -2.3 and Z score was >-1.5 in 2020. Alendronate was started.
She developed non-traumatic right ankle and heel pain the following year. Serial MRI showed non-healing fractures of the left distal tibia and transverse fracture of right distal tibia and right calcaneum. T scores of both NOF declined to -2.6 and -2.5 at the spine. Not tolerating alendronate, she was switched to IV zoledronic acid.
Three years after initial fracture, she developed non-traumatic left knee pain. Radiographs confirmed transverse fracture of the proximal tibia and calcaneum.
Individual episodes of fracture were not obviously attributed to methotrexate initially but the pattern of recurrent, non-traumatic, non-healing lower limb fractures over 3 years raised concern for methotrexate osteopathy. Methotrexate was replaced by sulphasalazine.
The calcaneum and proximal tibia are common sites for stress fracture or avascular necrosis, but she had no previous recurrent stress injury or thrombosis. Methotrexate osteopathy was first noted in children with leukaemia receiving high dose methotrexate. The exact pathophysiology is unclear but methotrexate is known to reduce osteoblast, osteocytes and chondrocytes in the growth plate. At least 80 adult patients with rheumatic disease have been reported with stress fractures associated with methotrexate osteopathy. Characteristics include atypical fractures in the lower limbs, most commonly distal tibia, calcaneum, proximal tibia, tarsus and metatarsus. Fractures also tend to be bilateral, multiple, slow healing and recurrent, with have band- or meandering appearance along the growth plate, as seen in this patient. Learning point: Methotrexate osteopathy is rare but should be considered in patients with multiple, recurrent or non-healing atypical bilateral lower limb fractures without pre-existing osteoporosis.
E.P. Chua: None. S. Bilgrami: None. R. Proctor: None.
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