Defining Clinically Relevant Proximal Junctional Kyphosis

Proximal junctional kyphosis and failure are not infrequent complications of adult spinal deformity reconstructions. Efforts to define proximal junctional kyphosis have ranged from expert opinions to statistical analyses of large databases. These approaches fail to recognize that proximal junctional kyphosis/failure/breakdown is likely a spectrum of manifestations secondary to spinal fusions and spinal alignment. The dichotomization (clinically irrelevant vs clinically relevant) of continuous measures will lead to misclassification and misdiagnosis. As adult spinal deformity moves to a precision-medicine-based approach (also known as personalized medicine), work is required to develop probabilistic models to inform patients and surgeons about the likely survivorship of a proximal junctional failure. As such, it is likely better to call proximal junctional segment kyphosis without symptoms "asymptomatic proximal junctional kyphosis" rather than to determine thresholds for "symptomatic" or "clinically relevant."