What causes referred back pain between the scapulae?

Causes of Referred Back Pain Between the Scapulae

Interscapular pain arises from either local thoracic spine pathology, referred visceral sources, or neurologic conditions affecting the cervical or thoracic spine. The most critical initial step is distinguishing benign musculoskeletal causes from serious underlying conditions requiring urgent intervention.

Primary Etiologies

Visceral Referred Pain

• Intrathoracic, gastrointestinal, renal, and vascular pathologies commonly refer pain to the interscapular region through viscero-somatic convergent neurons in the spinal cord 1, 2.
• Conditions include pancreatitis, nephrolithiasis, aortic aneurysm, cardiac ischemia, and pleural irritation 1, 3.
• Referred visceral pain results from central sensitization triggered by massive afferent visceral input and reflex muscle contraction 2.
• Pleuritis typically presents unilaterally when infectious or inflammatory 3.

Thoracic Spine Pathology

• The thoracic spine is a common site for inflammatory, neoplastic, metabolic, infectious, and degenerative conditions 1.
• Thoracic disc herniations occur most commonly below T7, are often calcified (20-65%), and present with midback pain (76% of cases), motor/sensory deficits (61%), and spasticity (58%) 1.
• Spinal stenosis from facet arthropathy, ligamentum flavum ossification, or disc herniations causes compressive myelopathy 1.
• Malignancy has a 0.7% prevalence in primary care back pain patients, increasing to 9% with prior cancer history 1, 4.
• Vertebral compression fractures occur in 4% of cases, particularly in patients >65 years or with chronic steroid use 1.
• Spinal infection has 0.01% prevalence but must be considered with fever, recent infection, IV drug use, or immunocompromised status 1, 4.

Inflammatory Conditions

• Axial spondyloarthritis (axSpA) involves the thoracic spine and thoracolumbar junction as the most common sites of spinal involvement in a minority with isolated spine disease 1, 3.
• Inflammatory back pain improves with exercise, worsens with rest, occurs at night, and has insidious onset before age 40 1, 3.
• Bilateral sacroiliitis is typical, but isolated thoracic involvement occurs 1.

Neurologic Causes

• Cervical radiculopathy refers pain to the periscapular region, typically with neck pain, arm symptoms, or neurologic deficits 3.
• Dorsal scapular nerve neuropathy causes mid-scapular and upper back pain from postural strain or overhead activities 5.
• Thoracic radiculopathy results from mechanical nerve root compression due to degenerative, metabolic, infectious, or neoplastic causes 1.

Myofascial Pain

• Muscle trigger points and myofascial pain are common causes of interscapular pain 6.
• Referred pain from deep somatic structures spreads through central sensitization to adjacent spinal segments 2.

Red Flags Requiring Urgent Evaluation

Immediate imaging with MRI is mandatory when any of the following are present 1, 3, 4:

• History of cancer (increases probability to 9%) 1
• Unexplained weight loss (positive likelihood ratio 2.7) 1
• Age >50 years (positive likelihood ratio 2.7) 1
• Fever, recent infection, IV drug use, or immunocompromised status 1, 3, 4
• Rapidly progressive neurologic deficits 3, 4
• Bladder or bowel dysfunction (cauda equina syndrome) 1, 4
• Failure to improve after 1 month (positive likelihood ratio 3.0) 1
• Significant trauma or known osteoporosis 1

Diagnostic Approach

Initial Assessment Without Red Flags

• No imaging is warranted for acute (<4 weeks) uncomplicated thoracic back pain without red flags or neurologic deficits 1.
• Conservative management with physical therapy and medical management should be attempted for 4-6 weeks 1.
• Consider imaging after 4-6 weeks if no improvement occurs with conservative treatment 1.

When Red Flags Are Present

• MRI thoracic spine without contrast is the initial imaging modality of choice for evaluating myelopathy, radiculopathy, or suspected serious pathology 1.
• If visceral pathology is suspected based on clinical presentation, chest imaging (radiograph or CT) should be obtained 3.
• Laboratory studies including CBC, ESR, and CRP should be obtained when infection or inflammatory conditions are suspected 3.

Specific Clinical Patterns

• Pain worsening with hunching suggests musculoskeletal etiology rather than inflammatory spondyloarthritis 3.
• Pain accompanied by neurologic deficits requires immediate MRI to evaluate for cord compression or radiculopathy 1.
• Unilateral presentation with pleuritic features should prompt evaluation for pulmonary/pleural pathology 3.

Common Pitfalls

• Failing to recognize visceral referred pain patterns leads to delayed diagnosis of serious conditions like cardiac ischemia or aortic pathology 1, 2.
• Ordering imaging for acute uncomplicated thoracic back pain provides no clinical benefit and increases costs 1.
• Missing red flags in older patients (>65 years) who have higher risk for compression fractures and malignancy 1.
• Attributing all interscapular pain to musculoskeletal causes without considering inflammatory conditions like axSpA, especially in younger patients with characteristic pain patterns 1, 3.