Scheuermann's Disease: Radiographic Pathomorphology and Association with Clinical Features

Scheuermann's Disease

Scheuermann's disease is a rigid progressive kyphosis occurring in late childhood to adolescence. It is the most common cause of sagittal imbalance and angular progressive kyphosis in adolescents associated with back pain. The exact etiology of the disease is unclear, but it is characterized by defective growth of the end plate that may result from excessive mechanical stress on a weakened end plate during spinal growth. Several other theories have been proposed, and it is thought to be a multifactorial disease occurring as a result of the interplay of multiple factors. The radiographic features consist of anterior vertebral body wedging, irregular end plates, Schmorl's nodes, and intervertebral disk degeneration. The natural history and evolution of this disease is also unknown. Conservative management with physiotherapy, rehabilitation, and bracing is the first line of treatment. Mechanical bracing helps prevent further progression of the kyphotic deformity. Surgery is mostly indicated in patients with failure of conservative management, with neurologic compromise, and for cosmetic reasons.

Loss of CSF-contacting neuron sensory function is associated with a hyper-kyphosis of the spine reminiscent of Scheuermann's disease

Scheuermann's disease, also referred to as Scheuermann's kyphosis, is the second most frequent spine deformity occurring in humans after adolescent idiopathic scoliosis (AIS), both with an unclear etiology. Recent genetic studies in zebrafish unraveled new mechanisms linked to AIS, highlighting the role of the Reissner fiber, an acellular polymer bathing in the cerebrospinal fluid (CSF) in close proximity with ciliated cells and mechanosensory neurons lining the central canal of the spinal cord (CSF-cNs). However, while the Reissner fiber and ciliary beating have been linked to AIS-like phenotypes in zebrafish, the relevance of the sensory functions of CSF-cNs for human spine disorders remains unknown. Here, we show that the thoracic hyper-kyphosis of the spine previously reported in adult pkd2l1 mutant zebrafish, in which the mechanosensory function of CSF-cNs is likely defective, is restricted to the sagittal plane and is not associated with vertebral malformations. By applying orthopedic criteria to analyze the amplitude of the curvature at the apex of the kyphosis, the curve pattern, the sagittal balance and sex bias, we demonstrate that pkd2l1 knock-outs develop a phenotype reminiscent of Scheuermann's disease. Altogether our work consolidates the benefit of combining genetics and analysis of spine deformities in zebrafish to model idiopathic spine disorders in humans.