Baastrup’s Disease is a spinal condition affecting the lumbar region of the back, widely known as “Kissing Spines.” This condition causes low back pain when bony projections on adjacent vertebrae make contact and rub against each other. The resulting friction leads to degenerative changes in the spine’s structure.
Understanding the Pathology
Baastrup’s Disease is defined by the close approximation and impingement of the spinous processes, the bony knobs running down the center of the back. In a healthy spine, these processes are separated by the interspinous ligament, which acts as a natural cushion and stabilizer.
When the space narrows, the bones rub together, especially when the back is extended. This repetitive mechanical friction causes a localized inflammatory response. The constant rubbing can lead to the formation of an adventitious bursa, a fluid-filled sac known as interspinous bursitis, which often becomes a source of pain.
The chronic irritation triggers changes in the bone structure. Over time, the involved spinous processes may become enlarged, flattened, and remodeled due to degeneration and friction. This includes reactive sclerosis, a hardening of the bone tissue at the points of contact. The most common location for this condition is the lower lumbar spine, particularly at the L4-L5 level.
Recognizing the Signs
The primary sign of Baastrup’s Disease is pain centered directly on the midline of the lower back, corresponding to the affected spinous processes. This pain is mechanical, meaning it is aggravated when the spine is extended, such as when standing upright, walking, or leaning backward.
Conversely, the pain is often relieved when the spine is flexed, a position that separates the spinous processes, such as sitting down or bending forward. This movement-dependent pain pattern is a key indicator for diagnosis. Another characteristic symptom is highly localized tenderness upon palpation directly over the affected bony area.
The pain can sometimes radiate slightly upward or downward along the spine, but it does not typically extend far to the sides of the back, differentiating it from nerve root compression. In rare instances, if inflammation or an epidural cyst extends into the spinal canal, it can cause symptoms like neurogenic claudication (leg pain triggered by walking). Symptoms often worsen during periods of high activity or prolonged standing.
Primary Causes and Risk Factors
The fundamental cause of Baastrup’s Disease is a reduction in the space between adjacent spinous processes, allowing them to make contact. This loss of space is most often a consequence of age-related degeneration, the most significant risk factor; the condition is most commonly seen in people over the age of 70.
Degenerative disc disease plays a major role, as the intervertebral discs lose height over time, causing the vertebrae to settle closer together. This decreased disc height effectively shortens the space between the spinous processes. Another contributing factor is excessive lordosis, an exaggerated inward curve of the lower back.
Hyperlordosis increases the mechanical pressure on the posterior elements of the spine. Repetitive movements involving frequent spinal extension, such as certain sports or occupational activities, can exacerbate this mechanical stress. Previous spinal trauma or surgery, along with conditions like osteoarthritis of the facet joints, can also contribute to the development of this syndrome.
Diagnosis and Treatment Options
Diagnosing Baastrup’s Disease begins with a thorough physical examination, assessing movement-related pain and checking for characteristic midline tenderness. Imaging studies confirm the clinical suspicion and rule out other causes of back pain. Standard X-rays of the lumbar spine clearly show the close approximation or contact between the spinous processes. These images also reveal secondary bone changes, such as flattening, enlargement, and reactive sclerosis.
Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scans provide a detailed look at the soft tissues and are useful for visualizing associated inflammation. An MRI can detect interspinous bursal fluid, bone marrow edema, and the presence of any epidural cysts. A diagnostic test involves injecting a local anesthetic and a corticosteroid into the affected interspinous space; if the injection provides temporary pain relief, it strongly supports the diagnosis.
Treatment typically starts with conservative, non-surgical methods aimed at reducing inflammation and pain. These approaches include oral pain relievers, such as nonsteroidal anti-inflammatory drugs (NSAIDs), and physical therapy to improve core muscle strength and modify posture. Physical therapy focuses on strengthening the abdominal muscles to reduce excessive lumbar lordosis.
If conservative methods are not effective, the next step often involves injection therapy. These are usually fluoroscopically-guided injections of a corticosteroid and anesthetic mixture delivered directly into the interspinous space or the bursa itself. Surgical options may be considered for chronic pain unresponsive to non-surgical interventions. Surgical procedures aim to decompress the area, either by removing a portion of the impinging spinous process or by implanting an interspinous spacer device to keep the bones separated.