Anatomy and Pathologies of the Spinous Process

The spinous processes act as a lever for attachments of muscles and ligaments. Spinal imaging is commonly performed as a diagnostic test for pain and radiculopathy. A myriad of incidental or unexpected findings, both potentially asymptomatic and symptomatic, may be encountered during the interpretation of these images, which commonly comprise radiographs, Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). Isolated lesions of the spinous process, although less common, are some of the lesions that may be encountered and can present a diagnostic dilemma. These can range from congenital abnormalities, traumatic lesions, neoplasms and lesions of inflammatory, infective and metabolic aetiology. The literature specifically reviewing these lesions is sparse. The article reviews a range of pathologies affecting the spinous process, along with their pertinent imaging features, based on isolated pathologies of spinous process lesions identified on imaging by the authors at a tertiary orthopaedic centre over a 10-year period. A search on the hospital Picture Archive and Communication System (PACS) and Radiology Information System (RIS) was performed using the keyword "spinous process" and a list of the isolated pathologies of the spinous process based on the imaging reports was compiled for the purpose of this narrative review. It is important that radiologists consider these lesions when they are identified on routine imaging of the spine.