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.
Lamellar bone formation in an abnormal location is defined as heterotopic ossification. It is first described by Patin in 1962 [
Heterotopic ossification commonly occurs around the hip joint, especially after total hip arthroplasties, and most often involves the abductor muscles [
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
Anteroposterior X-ray of the pelvis at the initial presentation.
3D-BT of the pelvis, presenting bilateral heterotopic ossification masses.
We discussed the treatment options with the patient after making a diagnosis of heterotopic ossification, explaining the need for surgical excision for the symptomatic right hip and the appropriate timing of surgery. We gave detailed information about the prophylactic postoperative process, including the need of single dose of 700 cGy radiotherapy and indomethacin medication 75 mg orally for six weeks.
The patient was placed in a supine position with a sand bag under the ipsilateral hip. The skin was incised starting from the anterior superior iliac spine and curving down so that it runs vertically for 8 cm, heading toward the lateral side of the patella (modified Smith-Petersen incision). The incision was deepened first between the sartorius and the tensor fasciae latae and then between the rectus femoris and the gluteus medius. We could then find the 10 cm long bony mass and carefully isolated it with minimal bleeding, osteotomized at the proximal end, stripped from the adherent soft tissue, and removed (Figure
Photo of the excised mass.
The abductor musculature is the most common site where heterotopic ossification around the hip is observed. The iliopsoas and the quadratus muscles are rarely reported as the involvement sites [
The pathogenesis of heterotopic ossification is still elusive. Trauma is reported to be the most common cause; however, atraumatic causes have also been reported [
The principal disability in nonprogressive heterotopic ossification is usually mechanical and characterized by painless restriction of joint movements, the degree of limitation being dependent upon the amount, and site of ossification. Patients usually regain a full active range of motion within a few days of excision of the bony mass [
Direct radiographs, CT scans, MRI, ultrasound imaging, and three-phase scintigraphy all play distinguishable roles in monitoring the disease [
Preventive measures, such as meticulous dissection during surgery, appropriate immobilization and physical therapy, indomethacin medication, and prophylactic radiation therapy, are the mainstay of the management of heterotopic ossification [
A very important issue, especially in nontraumatic cases, is the differential diagnosis, which includes malignant conditions like osteosarcoma and chondrosarcoma, infections, calcified abscesses, and hematomas [
Taking in mind that heterotopic ossification can develop without antecedent trauma, excision after the maturation of the bony mass, taking care for surgical skills, and postoperative prophylactic measures, such as indomethacin medication and radiotherapy, ensure a good result for treating this chemical-mechanical block to motion.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors’ thanks are due to Atakan KUSKUN, MD, for radiologic evaluation of the patients’ images.