Heterotopic ossification in unidentified skeletal remains

Heterotopic ossification is a benign, ectopic bone growth that develops in muscle and other soft tissue. The exact cause is poorly understood, but it is a rarely serious complication of soft tissue trauma. Its most common form, myositis ossifications traumatica, occurs as a secondary complication of direct muscle injury. However, other forms are less common and can result from specific pathologic conditions, such as spinal cord trauma and metabolic disorders. In patients who have had spinal cord injury and subsequent paraplegia, heterotopic ossification often results in ankylosis of the hip and a loss in range of motion. Ectopic ossification occurs below the injury site, and, although the specific muscle groups can vary, it usually involves those for which the origin and insertion involve the anterior pelvis and proximal femur. In dried bone, heterotopic ossification can appear as a smooth, irregularly shaped benign tumor of mature bone, extending from the surface but not invading the cortical bone. These tumors range in size from a few millimeters to several centimeters. Because heterotopic ossification is often associated with specific types of injuries, it has a unique anthropological use in forensic cases.