Spinous Process Impingement | Interspinous Bursitis | Degenerative Condition
IMAGING CLASSIFICATION
Critical Must-Knows
- Kissing spine = close approximation of adjacent spinous processes with pain on extension
- L4-L5 most common level, often multilevel involvement
- MRI shows interspinous bursitis as T2 hyperintense signal between spinous processes
- CT shows sclerosis and flattening of articulating spinous process surfaces
- Pain worse with extension, improved with flexion (opposite of disc herniation)
Clinical Pearls
- "First described by Baastrup in 1933
- "Often coexists with facet arthropathy and disc degeneration
- "Interspinous bursa is acquired, not congenital (develops from friction)
- "May cause dorsal epidural cyst from bursal extension
- "Injection is both diagnostic and therapeutic
Clinical Imaging
Imaging Gallery
Critical Baastrup Disease Exam Points
Clinical Diagnosis
Pain pattern is key: Midline low back pain worse with extension (standing, walking downhill), improved with flexion (sitting, bending forward). Tender over spinous processes. Distinguish from facet arthropathy (paramedian tenderness) and discogenic pain (flexion-aggravated).
Imaging Features
X-ray: Kissing spinous processes, sclerosis. CT: Sclerosis, flattening, enlargement of spinous processes. MRI: T2 hyperintense signal at interspinous ligament (bursitis), bone marrow edema. MRI is most sensitive for active disease.
Differential Diagnosis
Must distinguish from: Facet arthropathy (similar extension pain, paramedian), discogenic pain (flexion-aggravated), spinal stenosis (neurogenic claudication), spinous process fracture, interspinous ligament sprain. May coexist with other pathology.
Treatment Approach
Conservative first: Activity modification (avoid extension), NSAIDs, physical therapy. Injection: Interspinous bursa injection diagnostic and therapeutic. Surgery: Spinous process excision (partial/complete) if refractory.
Imaging Findings in Baastrup Disease
| Modality | Findings | Clinical Significance |
|---|---|---|
| X-ray (Lateral) | Kissing spinous processes, sclerosis | Screening, shows bony contact |
| CT | Sclerosis, flattening, enlargement, cyst | Best for bony detail |
| MRI STIR/T2 | Bone marrow edema in spinous processes | Indicates active inflammation |
| MRI T2 | Interspinous bursa - high signal fluid | Confirms symptomatic bursitis |
| MRI T1 post-Gd | Enhancement of interspinous tissue | Active synovitis/bursitis |
At a Glance
Baastrup disease ("kissing spine syndrome") is a degenerative condition caused by close approximation and impingement of adjacent spinous processes, most commonly at L4-L5. Pain is worse with extension (standing, walking downhill) and improved with flexion—the opposite pattern of disc herniation. An interspinous bursa develops from repetitive friction and appears as T2 hyperintensity on MRI between spinous processes. CT shows sclerosis and flattening of the articulating spinous process surfaces. Distinguish from facet arthropathy (paramedian tenderness) and discogenic pain (flexion-aggravated). Injection into the interspinous bursa is both diagnostic and therapeutic. Conservative management is first-line; refractory cases may require partial spinous process excision.
KISS - BKISS - Baastrup Features
| K | Kissing spinous processes Close approximation visible on lateral X-ray/MRI |
| I | Interspinous bursitis T2 hyperintense signal on MRI - key finding |
| S | Sclerosis of spinous tips Reactive bone formation from repetitive contact |
| S | Symptomatic with extension Pain worse standing, walking downhill, arching back |
| K | Kissing spinous processes Close approximation visible on lateral X-ray/MRI | S | Sclerosis of spinous tips Reactive bone formation from repetitive contact |
| I | Interspinous bursitis T2 hyperintense signal on MRI - key finding | S | Symptomatic with extension Pain worse standing, walking downhill, arching back |
Hook:KISS - the spinous processes are kissing, causing pain
BFSSExtension Pain DDx - BFSS
| B | Baastrup disease Midline, over spinous processes |
| F | Facet arthropathy Paramedian, over facet joints |
| S | Stenosis (spinal) Neurogenic claudication, leg symptoms |
| S | Spondylolisthesis Step-off palpable, instability |
| B | Baastrup disease Midline, over spinous processes | S | Stenosis (spinal) Neurogenic claudication, leg symptoms |
| F | Facet arthropathy Paramedian, over facet joints | S | Spondylolisthesis Step-off palpable, instability |
Hook:Extension aggravates all BFSS conditions - location of tenderness differentiates
BEEMRI Findings - BEE
| B | Bursitis (interspinous) T2 hyperintense between spinous processes |
| E | Edema (bone marrow) STIR hyperintense in spinous processes |
| E | Enhancement (post-gadolinium) Active inflammation/synovitis |
| B | Bursitis (interspinous) T2 hyperintense between spinous processes |
| E | Edema (bone marrow) STIR hyperintense in spinous processes |
| E | Enhancement (post-gadolinium) Active inflammation/synovitis |
Hook:BEE on MRI indicates active Baastrup disease
Overview and Epidemiology
Baastrup Disease (also called kissing spine syndrome) is a painful condition caused by close approximation of adjacent spinous processes with degeneration of the interspinous ligament and development of an adventitious bursa.
History:
Christian Ingerslev Baastrup, a Danish radiologist, first described this condition in 1933. He noted the characteristic radiographic finding of close approximation of spinous processes in patients with low back pain.
Epidemiology:
| Factor | Details |
|---|---|
| Age | Typically over 60 years, increases with age |
| Prevalence | 8-15% in elderly populations on imaging |
| Gender | Slight male predominance |
| Level | L4-L5 most common (81%), often multilevel |
| Symptomatic | Only minority of radiographic findings are symptomatic |
Associated Conditions:
Baastrup disease frequently coexists with other degenerative spine conditions. This reflects the common degenerative process affecting multiple structures.
- Facet joint arthropathy (very common)
- Disc degeneration and loss of height
- Spinal stenosis
- Spondylolisthesis
Symptomatic vs Incidental
Many patients have radiographic evidence of Baastrup disease without symptoms. The presence of interspinous bursitis on MRI (T2 hyperintense signal) and bone marrow edema on STIR sequences correlates better with symptomatic disease than simple kissing spinous processes on X-ray.
Anatomy of the Interspinous Region
Spinous Process Anatomy
Structure:
The spinous processes are posterior projections from the vertebral arch. In the lumbar spine, they are thick, broad, and quadrilateral, projecting horizontally backward.
| Level | Spinous Process Characteristics |
|---|---|
| L1-L3 | Horizontal orientation |
| L4 | Transitional, slight inferior angulation |
| L5 | Shortest, most horizontal |
Normal Interspinous Space:
| Structure | Function |
|---|---|
| Interspinous ligament | Connects adjacent spinous processes |
| Supraspinous ligament | Runs along tips of spinous processes |
| Fat tissue | Fills interspinous space |
| Potential bursa space | Develops from friction (adventitious) |
Interspinous Ligament
Composition:
The interspinous ligament is composed of three layers:
- Ventral - thin, close to ligamentum flavum
- Middle - main bulk, collagen fibers
- Dorsal - merges with supraspinous ligament
Changes with Degeneration:
With aging and disc degeneration, the interspinous ligament undergoes changes. Loss of disc height brings spinous processes closer together, leading to increased contact pressure. The ligament may undergo myxoid degeneration, cyst formation, and eventually frank bursitis.
Interspinous Bursa
Key Concept:
The interspinous bursa is NOT congenital. It is an adventitious bursa that develops from repetitive friction between adjacent spinous processes. This distinguishes it from congenital bursae elsewhere in the body.
Development:
- Disc degeneration leads to loss of height
- Spinous processes approximate
- Repetitive contact causes friction
- Adventitious bursa develops to reduce friction
- Bursa may become inflamed (bursitis)
- May extend posteriorly or into epidural space (cyst formation)
Pathophysiology
Mechanism of Disease
Primary Driver:
Loss of disc height (disc degeneration) is the primary driver of Baastrup disease. As the disc loses height, the spinous processes approximate and begin to contact during extension.
Cascade of Changes:
Loss of disc height with intervertebral space narrowing. This is the initiating event.
Adjacent spinous processes come into closer contact, especially during extension.
Interspinous ligament undergoes myxoid degeneration, develops clefts and cysts.
Adventitious bursa develops from repetitive friction (protective mechanism).
Bursa may become inflamed. Spinous processes develop sclerosis, flattening, and enlargement.
Osseous Changes
Spinous Process Morphology:
| Change | Mechanism |
|---|---|
| Sclerosis | Reactive bone formation from repetitive contact |
| Flattening | Remodeling of articulating surfaces |
| Enlargement | Hypertrophy response to stress |
| Cyst formation | Degenerative cysts within spinous process |
Extension Mechanism
Why Extension Hurts:
During lumbar extension, the spinous processes are brought closer together. In Baastrup disease, this causes direct bone-on-bone contact and compression of the inflamed interspinous bursa, generating pain.
Protective Flexion:
Lumbar flexion separates the spinous processes, decompressing the interspinous space. This is why patients often prefer sitting (flexed posture) and have difficulty with prolonged standing or walking (extended posture).
Complications
Dorsal Epidural Cyst:
In some cases, the interspinous bursa may extend posteriorly into the spinal canal, forming a dorsal epidural cyst. This can cause spinal stenosis symptoms (neurogenic claudication) in addition to axial back pain.
Reported in less than 10% of cases but important to recognize on MRI as it may require surgical excision.
Epidural Cyst
If a patient with Baastrup disease develops leg symptoms consistent with neurogenic claudication, look for a dorsal epidural cyst on MRI arising from extension of the interspinous bursa. This is an indication for surgical treatment rather than injection alone.
Classification
Imaging-Based Classification
No universally accepted classification exists, but the following imaging-based staging is useful:
Grade 1 - Contact Only
Imaging Features:
- Close approximation of spinous processes
- No sclerosis or reactive changes
- Normal interspinous signal on MRI
Clinical Significance: Often asymptomatic or minimally symptomatic. May represent early or pre-clinical disease.
Management: Observation if asymptomatic. Conservative measures if symptomatic. Generally responds well to non-operative treatment.
Associated Findings
Often coexists with other degenerative pathology:
| Associated Finding | Prevalence | Clinical Implication |
|---|---|---|
| Facet arthropathy | Very common | May need facet injections also |
| Disc degeneration | Universal | Part of same degenerative cascade |
| Spinal stenosis | Common | May have neurogenic claudication |
| Spondylolisthesis | Occasional | Contributes to spinous approximation |
Clinical Presentation
History
Pain Characteristics:
| Feature | Baastrup Pattern |
|---|---|
| Location | Midline low back |
| Character | Aching, sometimes sharp |
| Aggravating | Extension (standing, walking, arching back) |
| Relieving | Flexion (sitting, bending forward) |
| Radiation | Usually none, may have local radiation |
| Neurological | None (unless epidural cyst) |
Important History Points:
- Duration (usually chronic, insidious onset)
- Occupation (jobs requiring prolonged standing)
- Activities that worsen symptoms (walking downhill, lying prone)
- Activities that improve symptoms (sitting, leaning forward)
- Previous spine problems or surgery
Physical Examination
Inspection:
- May have exaggerated lumbar lordosis
- Antalgic posture (flexed)
Palpation:
- Tender over spinous processes (midline)
- May feel prominent spinous processes
- Paramedian tenderness suggests facet involvement
Range of Motion:
- Extension limited by pain
- Flexion typically full
- May have stiffness from associated degeneration
Provocation Tests:
| Test | Technique | Significance |
|---|---|---|
| Extension stress | Passive lumbar extension | Reproduces midline pain |
| Spinous pressure | Press on spinous processes | Local tenderness |
| Kemp test | Extension + rotation | May be positive (also positive in facet) |
Neurological Examination:
Typically normal in uncomplicated Baastrup disease. Abnormalities suggest associated stenosis, radiculopathy, or epidural cyst.
Red Flags
Red Flags to Exclude
Rule out serious pathology: night pain (tumor, infection), fever (infection), weight loss (tumor), bladder/bowel dysfunction (cauda equina), progressive neurological deficit. Baastrup disease should be mechanical, extension-aggravated pain without red flags.
Differential Diagnosis of Extension-Aggravated Low Back Pain
Differentiating Baastrup Disease from Mimics
| Condition | Pain location | Aggravated by | Key discriminator |
|---|---|---|---|
| Baastrup disease | Midline, over spinous processes | Extension | Midline spinous tenderness; T2/STIR interspinous bursitis; relieved by interspinous block |
| Facet (zygapophyseal) arthropathy | Paramedian (2-3 cm lateral) | Extension + ipsilateral rotation | Paramedian tenderness; relieved by medial branch block, not interspinous block |
| Lumbar spinal stenosis | Buttock/legs more than back | Standing/walking (extension) | Neurogenic claudication, relief with flexion/sitting; canal narrowing on MRI |
| Discogenic pain | Midline/deep | Flexion, sitting, loading | Flexion-aggravated (opposite pattern); high-intensity zone/Modic changes |
| Spondylolisthesis | Midline with instability | Extension, activity | Palpable step-off; slip on lateral/flexion-extension films |
| Spinous process stress fracture | Midline, acute focal | Any loading | Acute onset, often athletic/trauma; lucency on CT, edema on MRI |
Investigations
Imaging Protocol
X-ray (First Line):
- Lateral view essential
- Shows kissing spinous processes
- Sclerosis of spinous tips
- Loss of disc height at affected levels
CT Scan:
- Best for bony detail
- Shows sclerosis, flattening, enlargement
- Cystic changes within spinous processes
- Useful for surgical planning
MRI (Most Sensitive):
| Sequence | Finding | Significance |
|---|---|---|
| T1 | Spinous process morphology | Baseline anatomy |
| T2 | Interspinous hyperintensity | Bursitis (key finding) |
| STIR | Bone marrow edema | Active inflammation |
| Post-Gd | Enhancement | Active synovitis |
Diagnostic Injection
Interspinous Bursa Injection:
This is both diagnostic and therapeutic. Response to injection confirms Baastrup disease as the pain generator.
Technique:
- Patient prone
- Fluoroscopic or ultrasound guidance
- Needle into interspinous space at affected level
- Inject local anesthetic and steroid
Interpretation:
- Good relief = Baastrup confirmed as pain source
- Partial relief = may have coexisting pathology
- No relief = consider other diagnosis
Laboratory Studies
Usually not required. If concern for infection or inflammatory arthropathy:
- ESR, CRP (normal in Baastrup)
- HLA-B27 (if concern for spondyloarthropathy)
Management
Treatment Algorithm
Conservative Management (First Line):
| Intervention | Details |
|---|---|
| Activity Modification | Avoid prolonged extension, use lumbar support |
| NSAIDs | First-line pharmacotherapy |
| Physical Therapy | Core strengthening, flexion-based exercises |
| Weight Loss | Reduces lumbar lordosis and load |
Injection Therapy:
Indications:
- Failed conservative management (6-12 weeks)
- Diagnostic confirmation
- Therapeutic trial
Technique:
- Fluoroscopic or ultrasound-guided
- Into interspinous space at affected level(s)
- Corticosteroid and local anesthetic
Outcomes:
- 60-70% good response reported
- May need repeat injections
- Duration of relief variable
Surgical Management
Indications:
- Refractory to conservative and injection therapy
- Epidural cyst causing neurogenic symptoms
- Significant functional impairment
Surgical Options:
Spinous Process Excision
Options:
- Partial excision (just articulating surfaces)
- Complete spinous process resection
Technique:
- Midline posterior approach
- Remove interspinous bursa
- Excise portion of spinous process to eliminate contact
- Preserve supraspinous and interspinous ligaments if possible
Outcomes: Good to excellent pain relief in 70-85% reported. Minimal morbidity.
Treatment Selection
Most patients respond to conservative measures and injection therapy. Surgery is reserved for refractory cases. When epidural cyst is present, surgery is often required for decompression. The choice of surgical technique depends on associated pathology and surgeon preference.
Complications
Disease Complications
Dorsal Epidural Cyst:
- Extension of interspinous bursa into spinal canal
- May cause spinal stenosis symptoms
- Requires surgical excision
Adjacent Level Disease:
- Ongoing degeneration may affect other levels
- May develop Baastrup disease at other levels
Treatment Complications
Injection-Related:
- Infection (rare)
- Bleeding
- Temporary numbness
- Steroid side effects (if repeated)
Surgical Complications:
| Complication | Prevention/Management |
|---|---|
| Infection | Sterile technique, prophylactic antibiotics |
| Dural tear | Careful dissection |
| Instability | Preserve ligaments, avoid excessive resection |
| Recurrence | Adequate excision of bursa and bone |
| Adjacent level | May need to address multiple levels |
Long-Term Outcomes
Natural History:
Without treatment, Baastrup disease typically follows a chronic, waxing and waning course. Progressive degeneration may lead to increasing symptoms over time.
Prognosis:
With appropriate treatment (conservative, injection, or surgery), prognosis is generally good. Most patients achieve adequate pain control with conservative measures.
Postoperative Care
Spinous Process Excision Protocol
Day 0-1:
- Mobilization: Same day or next morning mobilization
- Wound care: Drain rarely required
- Pain management: Oral analgesia usually sufficient
- Activity: Sitting and standing tolerated
Week 1-2:
- Activity: Walking as tolerated
- Wound check: 10-14 days for suture removal
- Restrictions: Avoid heavy lifting, extension, bending
- Return to sedentary work: Often by 1-2 weeks
Week 2-6:
- Progressive activity: Gradual return to normal activities
- Physical therapy: Core strengthening, flexibility exercises
- Avoid: Repetitive extension movements
- Return to manual work: 4-6 weeks typically
Long-term:
- Follow-up: 6 weeks, 3 months, then as needed
- Maintenance: Ongoing core strengthening program
- Activity modification: Avoid prolonged extension
Outcomes
Treatment Outcomes by Modality
| Treatment | Success Rate | Duration of Benefit | Notes |
|---|---|---|---|
| Conservative | 50-70% | Variable | First-line for all patients |
| Injection therapy | 60-70% | 3-12 months | Diagnostic and therapeutic |
| Spinous process excision | 70-85% | Long-term | Definitive treatment |
| Interspinous spacer | 60-75% | Variable | Device complications possible |
Prognostic Factors
Favorable:
- Isolated Baastrup disease without stenosis
- Single level involvement
- Good response to diagnostic injection
- No epidural cyst
Unfavorable:
- Multilevel involvement
- Associated spinal stenosis or facet arthropathy
- Workers' compensation claims
- Poor response to injection
Patient Satisfaction
- Conservative management: 50-60% satisfied
- Post-injection: 60-70% good/excellent
- Post-surgery: 70-85% good/excellent pain relief
Evidence Base
Original Description by Baastrup (1933)
- First description of close approximation of adjacent lumbar spinous processes
- Associated with low back pain in a subset of patients
- Radiographic finding best seen on lateral lumbar X-ray
- Gave rise to the descriptive term 'kissing spines'
Prevalence and Associations on MRI
- Cross-sectional review of 539 symptomatic patients on lumbar MRI
- Interspinous bursitis (Baastrup disease) present in 8.2% (44 of 539)
- Significantly associated with older age, central canal stenosis, disc bulging and anterolisthesis
- NO significant association with disc degeneration, herniation, Modic changes, scoliosis or gender
Imaging Spectrum: Pictorial Review
- L4-L5 is the most commonly affected level; higher occurrence over age 70 with no gender predilection
- Hallmark is close approximation/contact of adjacent spinous processes
- Associated findings: oedema, cystic lesions, sclerosis, flattening, enlargement, bursitis, occasional epidural cysts/fibrotic masses
- Therapy spectrum: conservative care, percutaneous infiltration, surgical bursa excision or osteotomy
Posterior Epidural Cysts in Baastrup Disease
- Report of 10 patients with posterocentral epidural cysts arising from interspinous bursal fluid
- Interspinous bursal fluid can extend into the posterocentral epidural space and cause central canal stenosis
- Interspinous bursography (alone or with CT) documents the communicating channel between bursa and cyst
- Explains the mechanism linking axial Baastrup disease to neurogenic symptoms
Fluoroscopy-Guided Interspinous Infiltration
- Consecutive series of 55 patients, 67 fluoroscopy-guided interspinous infiltrations (corticosteroid plus local anaesthetic)
- Mean pain score fell from 8.18 to 0.62 on the NVS scale (mean reduction 7.56, p less than 0.001) at up to 1 year
- A second infiltration was needed in 22% (12 of 55) within 7-10 days
- No clinically significant complications
Full-Endoscopic Interspinous Plasty
- First report of full-endoscopic interspinous plasty for Baastrup disease (3 patients, local anaesthesia)
- Back-pain VAS improved from 7-8 preoperatively to 1-2 at 12 months
- Oswestry Disability Index improved markedly in all three cases
- CT confirmed an enlarged interspinous gap (1-4 mm) with little recurrent osteoproliferation
Partial Spinous Process Decompression
- Case report and literature review of surgical decompression for isolated symptomatic Baastrup disease
- Diagnosis confirmed with CT, MRI, SPECT and a positive local anaesthetic infiltration test
- Partial spinous process resection performed only after conservative therapy failed
- Highlights the lack of consensus on a consistent treatment strategy in the literature
Clinical Decision Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Extension-Aggravated Low Back Pain
"A 68-year-old retired teacher presents with 2-year history of midline low back pain. The pain is worse when standing and walking, and improved when sitting. Examination shows tenderness over L4 and L5 spinous processes. Lateral X-ray shows close approximation of L4-L5 spinous processes with sclerosis."
Baastrup with Neurogenic Claudication
"The same patient returns 6 months later with new symptoms of bilateral leg heaviness and numbness after walking 200 meters, relieved by sitting. MRI now shows a fluid-filled cyst extending from the L4-L5 interspinous space into the dorsal epidural space, causing thecal sac compression."
Multilevel Baastrup Disease
"A 72-year-old man presents with chronic midline low back pain. MRI shows interspinous bursitis at L3-L4, L4-L5, and L5-S1 with bone marrow edema at all levels. He has failed conservative management and wants to discuss injection options."
BAASTRUP DISEASE (KISSING SPINE)
Clinical summary
Definition
- •Close approximation of adjacent spinous processes
- •Interspinous bursitis develops from friction
- •First described by Baastrup 1933
- •L4-L5 most common level
Clinical Features
- •Midline low back pain
- •Worse with EXTENSION (standing, walking)
- •Improved with FLEXION (sitting)
- •Tender over spinous processes
- •Usually no neurological symptoms
Imaging Findings
- •X-ray: Kissing spinous processes, sclerosis
- •CT: Sclerosis, flattening, enlargement
- •MRI T2: Interspinous bursitis (hyperintense)
- •MRI STIR: Bone marrow edema
- •MRI most sensitive for active disease
Differential Diagnosis
- •Facet arthropathy (paramedian tenderness)
- •Discogenic pain (flexion-aggravated)
- •Spinal stenosis (leg symptoms)
- •Often coexists with other degeneration
Management
- •Conservative: Activity modification, NSAIDs, PT
- •Injection: Interspinous bursa (diagnostic/therapeutic)
- •Surgery: Spinous process excision if refractory
- •Epidural cyst requires surgical excision
Key Exam Points
- •Extension pain = BFSS (Baastrup, Facet, Stenosis, Spondy)
- •Location of tenderness differentiates
- •MRI confirms active bursitis (T2 hyperintense)
- •Interspinous bursa is ADVENTITIOUS (not congenital)
- •Epidural cyst = complication needing surgery
MCQ Practice Points
Classic Imaging Finding
Q: What is the pathognomonic MRI finding in symptomatic Baastrup disease?
A: T2 hyperintense signal within the interspinous space representing interspinous bursitis. This is an adventitious bursa that develops from repetitive friction between kissing spinous processes. Bone marrow edema on STIR sequences in the spinous processes indicates active inflammation.
Clinical Distinction
Q: How do you differentiate Baastrup disease from facet arthropathy clinically?
A: Both cause extension-aggravated low back pain, but:
- Baastrup disease: MIDLINE tenderness over spinous processes
- Facet arthropathy: PARAMEDIAN tenderness over facet joints (2-3cm lateral to midline)
Both improve with flexion and worsen with extension, standing, and walking downhill.
Most Common Level
Q: At which level does Baastrup disease most commonly occur?
A: L4-L5 (81% of cases). This level has the greatest range of motion in the lumbar spine and is subjected to the highest mechanical stress during extension. Multilevel involvement is common in advanced cases.
Treatment Approach
Q: What is the first-line treatment for symptomatic Baastrup disease?
A: Conservative management: Activity modification (avoid extension), NSAIDs, and physical therapy focusing on core strengthening and flexion-based exercises. Interspinous bursa injection (corticosteroid + local anesthetic) is both diagnostic and therapeutic. Surgery (spinous process excision) is reserved for refractory cases.
Guidelines, Registries & Global Practice
Baastrup disease has no dedicated society guideline; it is managed under the broader frameworks for non-specific and degenerative low back pain. There is no condition-specific implant registry. The themes below apply worldwide.
Global Epidemiology
| Measure | Figure | Source / context |
|---|---|---|
| MRI prevalence (symptomatic) | 8.2% of lumbar MRIs | Maes 2008, N=539, mixed-age symptomatic cohort |
| Most affected level | L4-L5, then L5-S1 | Greatest lumbar extension range |
| Peak age | Over 70 years | Degenerative, rises with age |
| Gender | No consistent predilection | Maes 2008 found no association; older series suggested mild male excess |
| Symptomatic fraction | Minority of radiographic cases | Most "kissing spines" are incidental |
Society Guidance: How Baastrup Fits Low Back Pain Pathways
| Body | Relevant recommendation | Implication for Baastrup |
|---|---|---|
| NICE (UK) NG59 | No routine imaging in primary care; risk-stratified care; exercise and self-management first | Reserve MRI for failed conservative care or red flags; do not over-investigate incidental kissing spines |
| AAOS / North American (US) | Multimodal conservative care; image-guided injection as targeted diagnostic-therapeutic tool | Supports interspinous block to confirm the pain generator before surgery |
| AO Spine / EFORT (Europe) | Confirm symptomatic level before any intervention; surgery only for refractory, anatomically concordant pain | Mandates a positive diagnostic block prior to spinous process resection |
| Interventional radiology / pain societies | Image guidance (fluoroscopy or ultrasound) for all interspinous infiltration | Defines standard of care for the injection step |
The common thread across societies: conservative first, confirm the level with an image-guided block, operate only on concordant refractory disease.
High- vs Limited-Resource Practice
- Well-resourced settings: MRI (sagittal T2/STIR) to confirm bursitis and exclude mimics, fluoroscopic/ultrasound-guided infiltration, and endoscopic or open spinous process surgery available.
- Limited-resource settings: Diagnosis often rests on lateral radiograph plus the clinical extension-pain pattern and a landmark-guided (non-image) infiltration as both test and treatment. Open partial spinous process excision is the realistic surgical option where endoscopy is unavailable.
Areas of Uncertainty / Controversy
- Symptomatic attribution: Because kissing spines are frequently incidental, the chief controversy is whether Baastrup disease is a true pain generator or a bystander. A positive diagnostic interspinous block is the only reliable arbiter.
- No accepted classification: The Grade 1-3 imaging staging used here is descriptive, not validated against outcomes.
- Surgical evidence is weak: All operative data are small case series or reports (Corr 2023, Lin 2021); no comparative trials exist, so surgery remains a last resort for image-confirmed, refractory, isolated disease.
- Interspinous spacers: Devices such as X-STOP have been withdrawn in several markets; evidence for spacers in isolated Baastrup disease (as opposed to stenosis) is minimal.
References
- Baastrup CI. On the spinous processes of the lumbar vertebrae and the soft tissues between them, and on pathological changes in that region. Acta Radiologica. 1933;14(1):52-55. (Historical primary source; predates PubMed indexing.)
- Maes R, Morrison WB, Parker L, Schweitzer ME, Carrino JA. Lumbar interspinous bursitis (Baastrup disease) in a symptomatic population: prevalence on magnetic resonance imaging. Spine (Phila Pa 1976). 2008;33(7):E211-5. PMID: 18379391. doi:10.1097/BRS.0b013e318169614a
- Filippiadis DK, Mazioti A, Argentos S, et al. Baastrup's disease (kissing spines syndrome): a pictorial review. Insights Imaging. 2015;6(1):123-128. PMID: 25582088. doi:10.1007/s13244-014-0376-7
- Chen CKH, Yeh L, Resnick D, et al. Intraspinal posterior epidural cysts associated with Baastrup's disease: report of 10 patients. AJR Am J Roentgenol. 2004;182(1):191-194. PMID: 14684538. doi:10.2214/ajr.182.1.1820191
- Filippiadis DK, Velonakis G, Malagari A, et al. Fluoroscopy-guided infiltration for pain reduction in patients with Baastrup's disease: clinical experience and results. Skeletal Radiol. 2015;44(9):1327-31. PMID: 25930945. doi:10.1007/s00256-015-2154-0
- Lin WT, Xie FQ, Lin SH, et al. Full-endoscopic approach for chronic low back pain from Baastrup's disease: interspinous plasty. Orthop Surg. 2021;13(3):1102-1110. PMID: 33783125. doi:10.1111/os.12988
- Corr F, Grimm D, Rothoerl RD. Partial spinous process decompression in Baastrup's disease: a case report and literature review. Cureus. 2023;15(1):e34070. PMID: 36843812. doi:10.7759/cureus.34070