What is Baastrup’s disease?

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Baastrup's Disease: A Degenerative Spinal Condition

Baastrup's disease, also known as "kissing spine syndrome," is a degenerative condition characterized by abnormal close approximation and contact of adjacent spinous processes in the spine, most commonly affecting the lumbar region at L4-L5, resulting in back pain that worsens with extension and improves with flexion. 1

Pathophysiology and Mechanism

The condition develops when adjacent spinous processes come into abnormal contact due to degenerative changes of the spine, often associated with excessive lordosis that produces mechanical pressure and repetitive strains of the interspinous ligament with subsequent degeneration and collapse. 1 The contact between adjacent spinous processes leads to a cascade of pathological changes including edema, cystic lesions, sclerosis, flattening and enlargement of the articulating surfaces, bursitis, and occasionally epidural cysts or midline epidural fibrotic masses. 1

Epidemiology

  • Age distribution: The mean age of affected patients is 59.6 years, with a decade-on-decade increase in incidence peaking at 81.3% among patients older than 80 years. 2, 3
  • Gender: Male to female ratio is 1.3:1, with no significant gender predilection. 2, 4
  • Prevalence: Studies show Baastrup's disease occurs in 37.8% to 41.0% of patients undergoing imaging, making it far more common than previously considered. 3, 4
  • Most affected level: L4-L5 is the most commonly affected spinal level. 1, 3

Clinical Presentation

The hallmark symptom is midline back pain that worsens during spinal extension, is relieved during flexion, and is exaggerated upon direct finger pressure at the affected level. 1 This characteristic pain pattern is crucial for clinical diagnosis and distinguishes it from other causes of low back pain.

Diagnostic Approach

Imaging Modalities (in order of utility):

  1. MRI with STIR sequence (most sensitive): The STIR sequence shows heightened sensitivity to fluid and edema, demonstrating lumbar interspinous bursitis and hyperintense signal changes in adjacent spinous processes and ligaments. 4 This promotes consensus among radiologists regardless of experience level. 4

  2. Dynamic flexion-extension radiographs: Standard and dynamic radiographs were performed in 16.2% of cases and help demonstrate the mechanical nature of the contact. 2

  3. CT scan: Performed in 43.9% of cases, CT effectively demonstrates the hallmark finding of close approximation and contact of adjacent spinous processes with sclerotic changes at apposing surfaces. 2, 3

  4. FDG PET/CT or MDP SPECT/CT: Used in 5.9% of cases, particularly important to distinguish Baastrup's disease from spinal bone metastasis, showing characteristic uptake at the interspinous region. 2, 5

Diagnostic Criteria:

Baastrup's disease is diagnosed when imaging demonstrates any of the following: 4

  • Lumbar interspinous bursitis
  • Hyperintense signal changes in adjacent spinous processes on STIR sequence
  • Hyperintense signal changes in ligaments on STIR sequence
  • Close contact between adjacent spinous processes with sclerotic apposing ends 3

Association with Degenerative Changes

Critical caveat: Baastrup's disease is nearly universally associated with other degenerative spinal changes (899/901 affected levels in one large study), making it challenging to definitively attribute back pain solely to the kissing spines. 3

Significant associations include: 4

  • Disc bulging (P = 0.0012)
  • Disc herniation (P = 0.0033)
  • Disc degeneration (P = 0.0013)
  • Modic changes (P = 0.034)
  • Facet osteoarthritis (P = 0.0041)
  • Spinal stenosis (P = 0.005)
  • Anterolisthesis (P = 0.0049)

Because of this near-universal association with other degenerative changes, caution is urged before diagnosing Baastrup's disease as the sole cause of back pain. 3 The condition may represent part of the expected spectrum of degenerative changes in the aging spine rather than a distinct pathological entity. 3

Treatment Algorithm

First-line (Conservative): 2

  • Anti-inflammatory drugs combined with physical therapy (used in 35.7% of treated patients)
  • This approach should be attempted for at least 6-12 weeks before considering interventional options

Second-line (Interventional): 2

  • Percutaneous infiltrations (used in 28.9% of treated patients)
  • Consider when conservative management fails and clinical examination confirms pain reproduction at the affected level

Third-line (Surgical): 2

  • Surgical decompression including excision of the bursa or osteotomy (used in 70.7% of treated patients)
  • Reserved for refractory cases with documented mechanical pain from spinous process contact

Important limitation: There is a significant need for randomized clinical trials to establish optimal treatment protocols, as current evidence is based primarily on case series and retrospective studies. 2

Clinical Pitfalls to Avoid

  1. Do not attribute all back pain to Baastrup's disease when multiple degenerative changes are present—the condition may be an incidental finding in elderly patients. 3

  2. Do not overlook malignancy: In patients with cancer history, use nuclear medicine imaging to distinguish Baastrup's disease from spinal metastases. 5

  3. Do not rely on static imaging alone: Dynamic flexion-extension radiographs help confirm the mechanical nature of symptoms. 2

  4. Do not assume rarity: With prevalence reaching 87.5% in patients over 80 years, Baastrup's disease should be routinely considered in the differential diagnosis of low back pain in elderly patients. 4

References

4
Research

Baastrup's disease prevalence across various age groups and its association with degenerative changes: insights from STIR sequence in MRI.

European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society, 2024

5
Research

MDP SPECT/CT Demonstration of Baastrup Disease.

Clinical nuclear medicine, 2022

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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