Heterotopic Ossification

Heterotopic ossification is the formation of mature lamellar bone in soft tissues outside the normal skeleton typically following musculoskeletal trauma surgery or neurologic injury. The condition develops through inappropriate differentiation of mesenchymal cells into osteoblasts driven by inflammation and altered local signaling. Common locations include the hip after acetabular fracture or arthroplasty the elbow after fracture dislocation and large joints in patients with traumatic brain or spinal cord injury.

Risk factors include male sex severe trauma surgical approach particularly extended iliofemoral approaches for acetabular fracture neurologic injury particularly traumatic brain injury and spinal cord injury and genetic predisposition. Symptoms include pain decreased range of motion warmth and erythema typically appearing two to twelve weeks after the inciting event. Plain radiographs show maturing bone within soft tissues with serial alkaline phosphatase elevation paralleling activity.

Prevention strategies include nonsteroidal anti inflammatory drugs particularly indomethacin for six weeks after high risk surgery low dose radiotherapy single fraction within seventy two hours of surgery and bisphosphonates in selected cases. Surgical excision is reserved for symptomatic mature heterotopic ossification typically waiting six to eighteen months for lesion maturation. Postoperative prophylaxis is essential to prevent recurrence. Physical therapy maintains range of motion and prevents contractures during the active and recovery phases. Multidisciplinary management optimizes functional outcomes.