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The spinous process is one of two bony protrusions arising from the posterior side of each vertebra in the human spine. Extending backward and downwards from the main body of the vertebra, each is an extension of the lamina, two bony plates that converge at the back of each vertebra to form the vertebral arch. The protrusions curve outward from this junction.
In the cervical, thoracic, and lumbar regions of the spine, the spinous processes of each vertebra serve as a site of attachment for various muscles and their ligaments. Those in the cervical spine, for instance, act as attachment sites for the upper trapezius, splenius capitus, and rhomboideus minor muscles, all of which have fibers running up the back of the neck. They also serve as a point of insertion for several of the erector spinae muscles, which originate in the lumbar and thoracic spine and run vertically up the back.
Many other muscles of the back attach to the thoracic spinous processes, including the splenius cervicis, the rhomboideus major, the latissimus dorsi. Some of the erector spinae muscles also attach to this region of the spine. The lumbar spine is where many of the erector spinae muscles originate, but they are also where the latissimus dorsi muscle, the largest muscle of the back, originates.
Though fractures of these bones are a relatively uncommon injury, there are several possible types, particularly in the lower cervical and upper thoracic region of the spine. A rare version of this injury occurs from repetitive stress, such as that imposed by laborers who perform sudden overhead lifting movements, and therefore is known as clay-shoveler’s fracture. This occurs when the stress of the trapezius and rhomboid muscles pulling against their attachment sites causes a vertical break in this part of the vertebrae.
More common fractures are those caused by sudden trauma. High-impact accidents, like car crashes or falls, can lead to what is known as a spinolaminar breach, in which a fracture occurs between the spinous process and the adjacent lamina. This is a more severe and complex injury than a clay-shoveler’s fracture and may involve accompanying damage to the spinal canal and/or attaching ligaments.
Most fractures do not occur in isolation. Especially in the case of traumatic injury, they tend to be accompanied by damage to other vertebral structures as well as to nearby muscles and ligaments. Direct blows to the back of the neck, for instance, can result in spinous process fractures, laminar fractures, muscle and ligament damage, and even spinal cord injury, which may produce mild to severe neurological symptoms. These symptoms can be immediately evident or may be delayed; therefore, as with any spinal injury, immediate medical attention should be sought, even if symptoms appear mild.