Bilateral neck of femur fractures in a paediatric patient with graves' disease.

Abstract

A 13-year-old boy presented with bilateral neck of femur fractures on a background of Graves' disease. The fractures were sustained after minimal trauma, following a fall from standing height. The patient was unable to bear weight and sought treatment immediately. There was no deformity of either limb. Plain radiographs and computed tomography showed bilateral basicervical femoral fractures with minimal displacement. The fracture of the left hip was valgus impacted, while the right side had fallen into a small degree of varus angulation (Fig. 1). There was evidence of generalised osteopenia on plain radiographs of the pelvis, femurs and hands. The patient sustained these fractures 2 months following a diagnosis of Graves' disease. He described symptoms of thyrotoxicosis, including increased appetite, weight loss and tremors. On examination, he was diaphoretic, tremulous, tachycardic, and displayed proximal muscle weakness, a large diffuse goitre and exophthalmos. Serum biochemistry was performed: measured T4 was 45.5 pmol/L, T3 was >46.1 pmol/L and thyroid-stimulating hormone <0.005 mU/L. Thyroglobulin, thyroid peroxidase and thyroid-stimulating hormone receptor antibodies were all strongly positive. Other causes of osteoporosis were excluded, with serum calcium, vitamin D, adrenocorticotropic hormone, cortisol and oestradiol levels within physiological ranges. Testing for hypogonadism and coeliac disease were negative. The patient had no significant medical history. Family history included thyrotoxicosis in his mother and maternal aunt, while his father was thyroid antibody positive but euthyroid. There were no other risk factors for osteopenia. Therapy with carbimazole and propranolol was prescribed. Operative fixation of both femoral neck fractures was carried out using cannulated hip screws without complication. Full weight bearing was allowed on the left leg post-operatively, with partial weight bearing on the right leg due to the initial varus angulation. The patient progressed well with physiotherapy and his symptoms of thyrotoxicosis were controlled with pharmacotherapy. A bone mineral density (BMD) scan was performed post-operatively. BMD was measured at the lumbar spine (0.660 g/cm2, Z score −2.4), total body (0.759 g/cm2, Z score −3.1) and right radius (0.369 g/cm2). The patient's chronological age was 13 years 11 months, while a bone age between 14 and 15 years was determined by bilateral hand radiographs per the Greulich and Pyle standards. The patient weighed 43 kg, his height was 167.5 cm, with a body mass index of 15.3. The effects of thyroid hormones on bone remodelling are well described in adults, with increased bone resorption, decreased BMD and an increased incidence of hip and long bone fractures.1-3 However, for children, fragility fractures secondary to Graves' disease are a rare occurrence. The literature describing such fractures in children is limited to two case reports, including a distal radius fracture3 and an oblique non-displaced femur fracture.4 Both reports describe a mechanism of injury consistent with the isolated injury, while the patient presented here sustained these fractures after minimal trauma, having fallen from standing height. Of note, 3 months following bilateral neck of femur fractures, the patient also sustained a fracture of the right distal tibia when transferring from a wheelchair, again a mechanism of low energy. This report highlights the significant risk of insufficiency fractures in paediatric patients with Graves' disease even with minimal trauma. We recommend that all paediatric patients with Graves' disease be assessed by their endocrinologist with regards to their risk of insufficiency fracture and that a high index of suspicion for fracture be maintained even for seemingly minor musculoskeletal complaints.