Bilateral Simultaneous Heterotopic Ossification of the Reflected Head of Rectus Femoris Muscle: A Case Report and Review of the Literature

Lamellar bone formation in an abnormal location is defined as heterotopic ossification. It commonly occurs around the hip joint and most often involves the abductor muscles. It is a benign condition; however, its etiology remains largely unknown. Most previously reported cases have been due to trauma or intramuscular hemorrhage. In this paper, we present a case of bilateral heterotopic ossification of the reflected head of rectus femoris muscle without antecedent trauma or any other known cause, as the first and unique case in the literature. She was treated by excision of the right symptomatic bony mass via a modified Smith-Petersen approach. Postoperatively, she received 75？mg indomethacin daily for six weeks. She was pain-free and obtained full range of motion 3 weeks after the first intervention. 1. Introduction Lamellar bone formation in an abnormal location is defined as heterotopic ossification. It is first described by Patin in 1962 [1]. It is a benign condition; however, its etiology remains largely unknown. The most common cause is trauma [2]. Although it is a self-limiting condition, it can cause significant morbidity, as restriction of range of motion, when it occurs close to joints [2, 3]. Heterotopic ossification commonly occurs around the hip joint, especially after total hip arthroplasties, and most often involves the abductor muscles [4, 5]. Involvement of the iliopsoas and quadratus muscles, as in very few cases, has been reported [1, 6–9]. Most previously reported cases have been due to trauma or intramuscular hemorrhage. In this paper, we present a case of bilateral heterotopic ossification of the reflected head of rectus femoris muscle without antecedent trauma or any other known cause, as the first and unique case in the literature. 2. Case Report A 35-year-old amateur dancer woman presented to our outpatient department with a history of gradual, progressive, and painless restriction of movement of her right hip over the previous five years. There was no history of surgery, bleeding disorder, or systemic illness. Local clinical examination revealed fullness in the right femoral triangle, but any palpable mass. There was no distal neurovascular deficit. She had significant restriction of hip flexion and internal rotation. Wasting in her hip and thigh musculature was absent. Radiological evaluation revealed bilateral ossified mass lying anterior to the hip joint originating from the anterior superior margin of the acetabulum and extending to the lesser trochanter (Figure 1).？ ？A 3-dimensional computerized tomography (3D-CT) scan