Development of Atypical Ulnar Fracture is Associated with Bisphosphonate Therapy and Severe Spinal Deformity: A Case Report.

Atypical ulna fracture (AUF) is relatively rare and is known to be associated with prolonged bisphosphonate (BP) use. The developmental mechanism remains unclear. We report a patient with an AUF associated with BP and severe spinal deformity. The patient was an 85-year-old woman receiving oral alendronate for 8 years without vitamin D supplementation. During regular kitchen work, she needed left upper limb support. She presented with atraumatic pain over the ulna. Radiographs revealed a transverse fracture in the proximal ulna and ulna bowing deformity. Whole-spine standing radiographs showed severe degenerative kyphoscoliosis. The skin induration with pigmentation on her left elbow that suggested prolonged overload and during standing work, coincided exactly with fracture location. This report suggests that 'direct stress', with persistent local overload on the proximal ulna, is one of the developmental mechanisms of AUF, in addition to persistent suppression of bone remodelling by prolonged BP use and vitamin D deficiency. Level of Evidence: Level V (Therapeutic).