P3.R359: Avascular Necrosis of the Hip in a Basketball Player

Introduction: A 15-year-old male basketball player presented to pediatric sports medicine with three weeks of left hip pain. He was diagnosed with a left hip avulsion fracture and advised to return for follow up in 2 weeks after physical therapy. 6 weeks later, he returned due to worsening pain and an inability to lift his leg, concerning for avascular necrosis (AVN). He was placed on crutches and referred to pediatric orthopedic surgery.

Case Description: Physical examination on the left side revealed tenderness over the anterior inferior iliac spine, failed straight leg test, pain with internal and external rotation, and limited range of motion (30° hip flexion, 5° external rotation, 0° internal rotation). X-rays revealed flattening, contour deformity, mild lateral displacement, an acetabular avulsion fracture (Figure 1) and AVN with crescent sign (Figure 2) of the left femoral head. MRI confirmed AVN and subchondral collapse of the femoral head.

Right lower extremity was normal. The patient’s biological mother was a cocaine user. The patient takes guanfacine, atomoxetine, and methylphenidate for ADHD and mood disorder.

Discussion: Avascular necrosis (AVN) of the hip is rare in youth and involves an interruption of blood supply, ultimately leading to bone death. If untreated, fractures and femoral head collapse are probable. Further, AVN limits proximal femur growth and may lead to overall growth disturbances in childhood.

AVN is associated with steroid use and sickle cell disease. Psychostimulants, including guanfacine and atomoxetine for ADHD, may impair bone cell differentiation to osteoblasts and disrupt mesenchymal stem cell migration. These medications may lead to decreases in bone mineralization and reductions in cell viability, providing impactions on bone health and perhaps increasing risks of avascular necrosis. Methylphenidate has been associated with negative influences on bone metabolism. An estimated 1 in every 10 US children has ADHD, for which these medications are common treatments.

AVN may be suspected based on history, physical examination and imaging. Patient age, growth plate development and femoral head placement are important treatment considerations for AVN. Non-surgical interventions include rest, activity restriction, physical therapy, and non-weight bearing, though these activities only slow progression. For adolescents, crutches are beneficial, and for children, bracing is an option. Surgical intervention is commonly necessary to avoid complete collapse of the femoral head.

Considerations on adherence to non-weight bearing walking in children with behavioral disorders may be needed considering the newly associated risks of psychostimulant medications on bone health and the vital importance of nonsurgical therapeutics in reducing the chance of AVN progression.

Conclusion: In young athletes with hip or thigh pain, AVN must be considered. Risks and therapeutic considerations for AVN need further research, especially considering the increasing amount of children on psychostimulants for behavioral needs.