Spinous processes are bony projections extending from each vertebra, forming the ridge felt along the center of your back. These structures are part of the vertebral column, supporting the body and protecting the spinal cord. They are located where the two laminae, or flat arched bones, of a vertebra meet at the back.
Anatomy and Location
Each vertebra features a spinous process, projecting from its vertebral arch. These processes vary in shape, size, and orientation depending on their location within the cervical, thoracic, and lumbar regions. The cervical spine has smaller spinous processes. The spinous processes of C2 through C6 are bifid, meaning they are split into two parts, which facilitates muscle and ligament attachments. The C7 vertebra, known as the vertebra prominens, has a larger and non-bifid spinous process that is easily felt at the base of the neck.
In the thoracic spine, spinous processes are longer and angle sharply downward, overlapping the vertebrae below them. This angulation provides stability and limits extension, aiding in the protection of the thoracic cavity. Lumbar vertebrae have larger, more robust, and horizontally oriented spinous processes. This design helps them bear a significant portion of the body’s weight and allows for greater flexibility in the lower back compared to the thoracic region. The distinct shapes and directions of these processes across the spinal regions are directly related to the specific movements and stability required at each level.
Role and Function
Spinous processes serve as attachment points for various muscles and ligaments that contribute to spinal stability and movement. The supraspinous ligament runs along the tips of these processes, providing support and limiting excessive flexion. Interspinous ligaments connect adjacent spinous processes, further enhancing stability and restricting movement between vertebrae.
Muscles such as the semispinalis cervicis and components of the transversospinalis group attach to spinous processes, enabling movements like extension, rotation, and lateral flexion. These bony projections also act as levers, increasing the mechanical advantage of the muscles that attach to them, thereby facilitating efficient spinal motion. Beyond movement, the spinous processes contribute to protecting the underlying spinal cord and nerves by forming a posterior bony barrier.
Common Conditions Affecting Spinous Processes
Spinous processes can be affected by various conditions, including fractures, inflammation, and degenerative changes, leading to localized pain and discomfort. One specific type of fracture is the clay-shoveler’s fracture, an avulsion fracture occurring in the lower cervical or upper thoracic spinous processes. This injury results from sudden, forceful muscle contractions that pull a piece of bone away from the main vertebra. Symptoms include immediate pain between the shoulder blades or at the base of the neck, accompanied by reduced head and neck motion, though neurological symptoms like tingling or numbness are absent. Diagnosis is confirmed with X-rays or MRI, and treatment involves rest and pain management, as these fractures are stable.
Inflammation can also affect the spinous processes and the surrounding soft tissues. Spinous process bursitis involves the inflammation of bursae, small fluid-filled sacs that can develop between closely approximated spinous processes. This condition presents as dull, constant midline pain that may worsen with prolonged activity or hyperextension of the neck. It can be associated with inflammatory conditions like polymyalgia rheumatica or calcium pyrophosphate deposition disease.
Baastrup’s disease, also known as “kissing spine syndrome” or interspinous bursitis, is a degenerative condition where adjacent spinous processes in the lumbar spine come into close contact and rub against each other due to degenerative changes or excessive spinal curvature (lordosis). This repetitive contact can lead to inflammation, bursa formation, and degenerative changes like bone sclerosis or flattening. Patients experience midline back pain that intensifies with spinal extension and may be relieved by flexion. Diagnosis is made using imaging techniques like X-rays, CT scans, or MRI, which reveal characteristic close approximation and soft tissue changes. Management involves conservative approaches, though injections or surgical intervention may be considered.