Q3 Urgent Caring- Imaging Challenges—What Are Those Lines?

An 11-year-old female presents to Urgent Care with complaints of right knee pain. Mom states she has been complaining of a vague pain after exercising and would like an X-ray to make sure there is no pathologic fracture. There was no injury. The radiograph was performed per protocol by the technologist prior to evaluation by the provider. There was no significant past medical history disclosed prior to the X-ray.

These lines are called “Zebra lines” and are seen in patients with osteogenesis imperfecta (OI) who have received bisphosphonate therapy during childhood¹². Upon further questioning, Mom forgot to mention the child had OI and had received pamidronate in the past.

These lines represent metaphyseal bands, which vary in space according to the age of the patient, the rate of growth, and the location of the metaphysis. Each line corresponds temporally to the administration of a bisphosphonate. The lines are caused by the increased bone mineralization by the bisphosphonate therapy.

OI is a phenotypically diverse group of inherited connective tissue disorders that share similar skeletal abnormalities causing bone fragility and deformity. There is wide variation in the severity of the disease. The initial diagnosis is based on clinical and radiographic findings. Fractures from mild trauma, bowing deformities of long bones, and growth deficiency are the hallmark features. Dependent on age and severity, skeletal features can include macrocephaly, flat midface and triangular facies, dentinogenesis imperfecta, chest wall deformities such as pectus excavatum or carinatum, barrel chest, and scoliosis or kyphosis.³

Bisphosphonates are antiresorptive drugs which are widely used to treat children with OI. Treatment aims to increase bone volume by counteracting the high turnover of bone.