The posterior projection of the vertebral arch, the Spinous Processes, are palpable through the skin from C7 through L5, and present as the median sacral crest. The spinous processes serve as reference landmarks and attachment sites for multiple muscle systems (spinal, transversospinal, sacrospinal (erector spinae), spinotransverse, short nuchal, spinoscapular, and spinohumeral).
C7 is referred to as the vertebra prominens because of its palpable nature at the cervicothoracic transition. The spinous processes of cervical vertebrae C2-C6 are not easily palpable. The most common congenital malformation of vertebrae is spina bifida occulta. This defect, usually in the arch of L5 and/or S1 vertebrae, occurs in about 10% of individuals. The skin hides the bifid arch, but its location is often marked by a tuft of hair. Most spina bifida occulta patients are asymptomatic, while some may exhibit low back pain. Patients with more severe malformation (spina bifida cystica, or spina bifida with meningocele) often exhibit spinal cord and/or spinal nerve root dysfunction (paralysis of the limbs and incontinence of urine and feces).