Baastrup’s disease, commonly known as “kissing spines” syndrome, is a spinal condition where the bony projections at the back of adjacent vertebrae in the lower back touch or rub against each other. This abnormal contact can lead to localized pain and discomfort. This article explores the factors contributing to its onset.
Anatomical Context
The spine consists of individual vertebrae, each with a bony projection at its rear called the spinous process. These processes serve as attachment points for muscles and ligaments. Normally, soft tissues, including the interspinous ligament, maintain a space between the spinous processes. This ligament limits excessive forward bending, ensuring spinal stability.
In a healthy spine, spinous processes and interspinous ligaments allow for controlled movement. The lumbar region, or lower back, is particularly susceptible due to its role in supporting body weight and its range of motion. Proper spacing between these bony structures is important for pain-free movement and overall spinal function. When this spacing is compromised, it can set the stage for conditions like Baastrup’s disease.
Primary Mechanisms
Baastrup’s disease primarily arises from degenerative changes within the spine. As people age, the intervertebral discs, which act as cushions between vertebrae, can lose water content and height. This reduction in disc height brings the adjacent vertebrae and their spinous processes closer together. The narrowing of the space between these processes is a fundamental step in the condition’s development.
Once the spinous processes are in close proximity, they rub against each other during spinal movements, particularly extension. This repeated mechanical stress and friction lead to localized inflammation in surrounding tissues and can cause interspinous bursitis, an inflammation of fluid-filled sacs. Over time, this chronic irritation triggers bone remodeling, resulting in sclerosis (hardening and thickening of bone) and osteophytes (bone spurs). These bony changes further exacerbate contact and lead to pain.
The continuous rubbing and bone changes represent repetitive microtrauma. This ongoing wear and tear on the spinous processes and the interspinous ligament contributes to the progression of Baastrup’s disease. The body’s attempt to stabilize the affected area through bone growth inadvertently increases the impingement, creating a cycle of irritation and structural alteration.
Factors That Increase Risk
Several factors increase the risk of developing Baastrup’s disease. Age is a major factor, with the condition becoming more common in older individuals due to natural degenerative processes in the spine. The incidence rises notably in those over 70 years of age.
Prolonged or poor posture, such as excessive lumbar lordosis (an exaggerated inward curve of the lower back), also contributes to this condition. This posture increases mechanical pressure and contact between the spinous processes. Additionally, obesity places increased stress on the lumbar spine, which can contribute to disc degeneration and alter spinal mechanics, elevating the risk.
Certain activities or occupations involving repetitive spinal extension or high-impact movements can accelerate wear and tear on spinal structures. While these factors do not directly cause the disease, they create conditions that promote degenerative changes and mechanical stresses leading to abnormal contact of the spinous processes.