ั่ั้่ัุ้่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่่ั่ั่ ุHeterotopic ossification of varying severity can be caused by surgery or trauma to the hips and legs. About every third patient who has total hip arthoplasty (joint replacement) or a severe fracture of the long bones of the lower leg will develop heterotopic ossification, but is uncommonly symptomatic. Between 50% and 90% of patients who developed heterotopic ossification following a previous hip arthoplasty will develop additional heterotopic ossification.
Heterotopic ossification often develops in patients with traumatic brain or spinal cord injuries, other severe neurologic disorders or severe burns, most commonly around the hips. The mechanism is unknown. This may account for the clinical impression that traumatic brain injuries cause accelerated fracture healing.