Postencephalitic bilateral heterotopic ossification of the hip in a pediatric patient.

Abstract

Heterotrophic ossification has been defined as abnormal formation of mature lamellar bone in soft tissues. Neurogenic heterotopic ossification has been well described in adults. However, it is uncommon in the pediatric population, where it has been noted to recede in some cases. There are very few reports of postmeningitis bilateral involvement of the hip. We describe a case of bilateral heterotopic ossification of hip in a 13-year-old female. The patient had a history of encephalitis, prolonged vegetative state, and intubation for 6 weeks. The patient had fixed deformities of both hips in 30° of flexion and 30° of external rotation. A diagnosis of Brooker stage 4 heterotopic ossification was made. The patient underwent a staged procedure for excision of the heterotopic mass. Postoperatively, the patient was administered radiotherapy and indomethacin for 6 weeks. At the 2-year follow-up, there was no recurrence and both the hips were mobile with full range of motion. The patient was satisfied with the result. The incidence of heterotopic ossification is less than that observed in the adult population and alkaline phosphatase levels are not significantly elevated unlike in adults. To our knowledge, there is no reported case of postencephalitic bilateral anterior heterotopic ossification of the hip in a pediatric patient treated with excision successfully. Postencephalitic heterotopic ossification in children is an uncommon condition. This condition can be treated successfully with surgical excision, combined postoperative protocol of radiotherapy, indomethacin, and immediate postoperative mobilization of the joint.