Surgical management of bilateral atypical tibial fractures associated with long-term bisphosphonate therapy in a cat

Case summary: An 8-year-old, indoor, male neutered Oriental mixed-breed cat was presented with acute bilateral pelvic limb lameness without preceding trauma. The cat had received oral alendronate for 4.5 years for the management of feline idiopathic hypercalcaemia. Radiographs revealed bilateral, closed, comminuted proximal tibial and fibular fractures with cortical sclerosis. Staged bilateral open reduction and internal fixation were performed using orthogonal locking compression plates. Alendronate therapy was discontinued, and the cat remained normocalcaemic during 8 months of follow-up. Despite robust stabilisation, traumatic re-fracture of the right tibia occurred after inadequate confinement, necessitating revision fixation with longer implants and the addition of allogeneic demineralised bone matrix (DBM). Delayed union and marked callus formation were observed in the left tibia, consistent with suppressed bone remodelling secondary to chronic alendronate therapy. In contrast, the revised right tibial fracture, treated with adjunctive DBM, demonstrated faster progression of healing. Radiographic monitoring demonstrated osseous union without further complications or evidence of additional fractures, illustrating that favourable outcomes are achievable in cats with bilateral bisphosphonate (BP)-associated insufficiency fractures when appropriately managed. Relevance and novel information: This report represents the second documented case of BP-associated fractures in a cat managed surgically with extensive follow-up. It is the first to describe bilateral tibial fracture repair and the use of adjunctive DBM for BP-associated fractures. It highlights that favourable outcomes are achievable in these cases through orthogonal plating combined with adjunctive DBM, and discontinued BP therapy to reduce future fracture risk. This report also supports serial radiographic monitoring, particularly within 5 years of treatment initiation.