Baastrup Syndrome

Original Editors - Sofie Bourdinon

Top Contributors -

Sofie Bourdinon, Nikki Rommers, Ceulemans Lisa and Aarti Sareen  


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Keywords: Baastrup syndrome, Baastrup AND etiology, Baastrup disease, kissing spines, Baastrup’s sign, Baastrup syndrome AND physical therapy, Baastrup syndrome AND exercise, Kissing spines AND conservative therapy, Baastrup disease AND surgical management, hyperlordosis AND physical therapy.


Baastrup Syndrome is named after Christian Ingerslev Baastrup, a Danish radiologist (1855-1950). It is also known as ‘kissing spines’. Kissing spines is a common disorder of the vertebral column. It is characterized by close approximation and contact of the spinous processes of two neighboring vertebrae. This can result in the formation of a new joint between them. This possibly causes mechanical back pain. The hypertrophied spinous processes of adjoining lumbar vertebrae in close approximation or in actual contact may undergo reactive sclerosis or degeneration. This is mostly observed in the lumbar segment, but has also been reported to occur in the cervical spine in some cases.[1][2][3]

Clinically Relevant Anatomy

The spinous processes of the lumbar spine are orientated dorsally and caudally. All of the muscles that are involved in spinal movement and stabilization are only attached to the posterior elements of the spine. Therefore the spinous processes are subjected to major forces with movement or stabilization of the spine.[4]


                                                         Abnormal downward pointing and thickening of spinous process

The interspinous ligament arches between two adjoining spinous processes. Anteriorly, it is continuous with the ligamentum flavum and posteriorly it fuses with the supraspinous ligament. The external layer of the interspinous ligament contains fibers of the aponeuroses of the M. longissimus, which contributes to the stability at that level. The interspinous ligament functions primarily to prevent excessive spinal flexion and thereby separation of two adjacent spinous processes. Secondary it has been suggested that the interspinous ligament also aids with controlling vertebral rotation during flexion helping the facet joints remain in contact while gliding.[4]

The supraspinous ligament is attached to the posterior tips of the spinous processes from approximately C7 to L4-L5. It contributes to limit spinal flexion and resist separation of two neighboring spinous processes.
The posterior part of the interspinous and supraspinous ligaments are sensory innervated. Its role is thought to give proprioceptive information and protect against excessive forces.[4]

Epidemiology /Etiology

The exact etiology of Baastrup’s sign is unknown. The hypothesis is that an excessive lordosis or extensive loss of intervertebral space is linked to degeneration of the vertebral disc which can lead to contact between spinous processes and to degeneration of intervening ligaments.
Incorrect posture and traumatic injuries can also cause this condition. Other possible causes of kissing spines are: excessive lordosis due to scoliosis and kyphoscoliosis, spondylolysthesis, tuberculous spondylitis, bilateral forms of congenital hip dislocation and obesity. Also increased spinous process dimensions linked to several rare disorders can cause kissing spines.[1][2]

It can also be caused when the thoracic spine or the thoracolumbar transition is stiff[5].
The Baastrup syndrome is only one aspect or symptom that can appear in several disorders[6] and it has some risk factors[7] attached like painful lumbar extension. [5]

There is controversy regarding the etiology of pain in this condition. The cause of pain has been described to be mainly mechanical because of the neighboring spinous processes coming into contact. This is worse with hyperextension or increased lordosis, as in patients with obesity or limitation of hip movements and champion swimmers.[1][8]

The epidemiology of Baastrup’s sign in the general population is unknown. It seems to be high according to the relatively frequent abnormal changes of the interspinous spaces and spinous
processes seen at autopsy.[2]

Characteristics/Clinical Presentation

The patient will talk about localized interspinous or spinous process pain with or without a referral pattern, although the cause of the pain in Baastrup’s disease is unclear [8][9][10]. The role of Baastrup’s disease as a substantial nociceptor is controversial. Surgical excision of the involved spinous processes has not been proven to be effective in pain relief[9]. There are also many other possible pain generators in the lower back region[9][10]

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In case of propagation of the bursa into the dorsal epidural space, Baastrup’s disease can result in intraspinal cysts that may rarely cause symptomatic spinal stenosis and neurogenic claudation[1]. Those bursae can produce back pain that responds to injection of local anesthetics[9][10].

In 8.2% of patients with low back pain, lumbar interspinous bursitis was present in a study using MRI[8]. In a study using CT scans of a general population, 41% of that population had evidence of Baastrup’s disease[9].

Baastrup’s disease is age related with an increasing occurrence with increasing age[8][9]. L4-L5 is most commonly affected[9].

Extension is the most painful lumbar movement, the spinous processes can touch, wich might cause irritation of the interspinal ligament [11][5]. When the rotation and lateral flexion is examined, it will be painful. Flexion is the least painful of all lumbar movements[11].


Differential Diagnosis

• Central spinal canal stenosis
• Infection
• Lumbar spondylosis
• Muscle strain
• Paracentral disc herniation
• Spinous process fracture
• Spondylolisthesis
• Vertebral compression fracture

Diagnostic Procedures

Radiology and CT

Using radiology, the opposing surfaces of the spines are seen. They develop sclerosis and can also become hypertrophied and flattened. It shows a decreased space between adjacent spinous processes. There is a typical enlargement and flattening of the superior and inferior surfaces of the spinous processes resulting in a faceted appearance. Osteophytes may arise from the spinous processes. [12][9]


MRI may demonstrate interspinous bursal fluid and a postero-central epidural cyst(s).
Lumbar interspinous bursitis can be diagnosed when hyperintense bursal fluid collections are present between and adjacent to spinous processes.[8][12] MRI can be very helpful in determining whether there is resulting posterior compression of the thecal sac. It provides insight into the soft-tissue.[8]


Outcome Measures

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The pain can be described as a sharp or deep ache, often worse with activities that increase lumbar lordosis or compression of these structures.[4]
History often reveals an insidious onset without associated trauma.

It is difficult to assess proximity of spinous processes on manual palpation due to their overlapping nature. There could be a palpable tenderness of the supraspinous ligament with the patient in a side lying – fetal position.

Palpation of the midline back and spinous processes may reproduce the symptoms.
Physical examination like the ‘Stork test’ (standing on one leg with passive extension of the lumbar spine) or active spinal extension can also reproduce the symptoms.
When the patient bends forward or puts the knees to the chest, relief is gained. [11]

Medical Management


If the complaints are the cause of a single trauma, then an injection with a corticosteroid on the painful place, will be very effective.[13] If the condition is the cause of a chronic micro trauma, then two to four infiltrations are indicated. The injection is given once every two weeks. During the treatment period, extension movements of the lumbar spine should be avoided. In intractable cases, surgery is sometimes indicated.[14]


There’s one study that investigates the results of surgical activities following partial or total excision of the processus spinosi. These were not very satisfactory. Of the 64 patients who participated, only 11 were free of complaints after the operation. In the other 53 patients, the complaints remained or returned after a short time. [15] The discussion is that the kissing spines are phenomenon due to another pathology, especiallyLumbar Spondylosis with osteophyte formation.

Physical Therapy Management

One source tells conservative treatment should consist of local modalities, over-the-counter analgesics and physical therapy. Physical therapy is focussed on neuromuscular education of the core muscles, posture in a flexion bias and stretching of the hip flexor groups. [16][17]

Another source says that the treatment goals of physical therapy are reducing the pressure and the lordosis. The lordosis can be reduced by stretching the tight myofascia and strengthening the abdominal muscles. [11][17]

A cohort studie investigates whether a training program can modify lumbar posture. Goals of the training program, for patients with lumbar hyperlordosis, were increasing the muscle activity of the abdominal and gluteal muscles (thereby reducing the relative contribution of the erector spinae muscles) and increasing the length of the hip flexor muscles. The results of this study suggest that training has the possibility to change lumbar positions, which decreases or increases lumbar passive tissue strain.[18]

Pilates exercises could possibly improve hyperlordosis.[19]


Key Research

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Clinical Bottom Line

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Recent Related Research (from Pubmed)

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  1. 1.0 1.1 1.2 1.3 S. Rajasekaran et al. Baastrup’s Disease as a Cause of Neurogenic Claudication. SPINE Volume 28, Number 14, pp E273–E275 ©2003, Lippincott Williams &amp;amp; Wilkins, Inc. (Level of evidence 3)
  2. 2.0 2.1 2.2 S. Kacki et al. Baastrup’s sign (kissing spines): A neglected condition in paleopathology. International Journal of Paleopathology 1 (2011) 104– 110. (Level of Evidence 4)
  3. P.S. Pinto. Spinous process fractures associated with Baastrup disease. Journal of Clinical Imaging 28 (2004) 219–222. (Level of Evidence 4)
  4. 4.0 4.1 4.2 4.3 M.J.Depalma. Ispine: Evidence based interventional spine care. 2011, Demos Medical Publishing. (Level of Evidence 2)
  5. 5.0 5.1 5.2 Winkel D. Orthopedic medicine and manual therapy part 4b SPINE. Houten/Zaventem: Bohn Stafleu Van Longhum, 1991.
  6. Orthopedische geneeskunde en manuele therapie: Wervelkolom.
  7. Spine &amp;amp;amp;amp;amp; Sports medicine of New York fckLR;amp;amp;amp;amp;p=202
  8. 8.0 8.1 8.2 8.3 8.4 8.5 R. Maes et al. Lumbar Interspinous Bursitis (Baastrup Disease) in a Symptomatic Population. 2008, Spine, pE211-E215 (Level of Evidence 3)
  9. 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 Y. Kwong et al. MDCT Findings in Baastrup Disease: Disease or Normal Feature of the Aging Spine? 2011, American Journal of Radiology, p1156-1159 (Level of Evidence 3)
  10. 10.0 10.1 10.2 C. Hui, I. Cox. Two Unusual Presentations of Baastrup’s Disease. 2007, Clinical Radiology, p495-497 (Level of Evidence 4)
  11. 11.0 11.1 11.2 11.3 D.Hertling, R.M.Kessler. Management of common musculoskeletal disorders: Physical Therapy Principles and Methods. 4th edition. 2006, Lippincott Williams &amp; Wilkins. (Level of Evidence 2)
  12. 12.0 12.1 M.J. DePalma et al. Interspinous bursitis in an athlete. 2004, Journal of Bone &amp; Joint Surgery, p1062-1064 (Level of Evidence 5)
  13. Raj Mitra, MD, Usama Ghazi, DO, Dhiruj Kirpalani, MD, Ivan Cheng, MD.Interspinous Ligament Steroid Injections for the Management of Baastrup’s Disease: A Case Report. Arch Phys Med Rehabil. 2007;88:1353-6.(Level of Evidence 3)
  14. T.J. Lamer, J.M. Tiede, D.S. Fenton. Fluoroscopically-Guided Injections to Treat “Kissing Spine” Disease.2008. ( (Level of Evidence 2)
  15. J.W.F.Beks. Kissing Spines: Fact or Fancy? 1998, Neurosurgical Clinic University Hospital, Groningen, The Netherlands. (Level of Evidence 2)
  16. 8
  17. 17.0 17.1 A.Panagos. Spine. 2009. Demos Medical Publishing. (Level of Evidence 4)
  18. J.P.Scannell, S.M.McGill. Lumbar posture-should it, and can it, be modified? A study of passive tissue stiffness and lumbar position during activities of daily living. 2003, Physical Therapy. (Level of Evidence 2)
  19. V.Razaeei, M.Ghofrani. Effect of two month Pilate's exercises on the lumbar hyperlordosis of 15-18 years old girl students. Annals of Biological Research, 2012, 3 (6):2667-2672 (Level of Evidence 2)

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