Imaging for back pain

Some issues in spine imaging
Dr Greg Cowderoy

• Radiation exposure: is it important?
• Role of X-ray, bone scan and other modalities
• CT vs MRI for back pain
• Guidelines for imaging of low back pain
• Imaging appearances of disc herniation and spinal st
• The young athlete with back pain
• Indications for vertebroplasty
• A few cases

• Imaging appearances of disc herniation and
spinal stenosis
• Indications for vertebroplasty
• A few cases

CT radiation dose
• Background average 2-3 mSv/year
– Natural background 85%
– Medical 14%
– CT 40-67% of medical
• CT use increased by 600-820% over 20 years
from mid-80s
– Plateaued/ decrease more recently

CT dose reduction strategies
• Only use CT where appropriate (US, MRI)
• Scan parameters: pitch, kvp, mAs
– Paediatrics
– Built-in protocols
– Automatic tube current modulation
– Iterative image reconstruction
• Minimize phases
– No pre-contrast for trauma, oncology follow-up
• Minimize coverage
– L3 to S1 in most cases

Radiation doses
Imaging test Effective
dose (mSv)
CXRs Background
exposure
Flying hours
CXR 0.02 1 3 days 4
Lumbar X-ray 1.5 75 6/12 300
Lumbar CT 2-10 100-500 8/12 - 3 years 400 - 1800
Bone scan 6 300 2 years 1200

CT risk controversies
• Validity of linear, no threshold model
• Variable literature
– Increased cancer risk in some
– Beneficial effect of low level radiation in others
• Children more radiosensitive and at greater risk
for decades
• Triple risk secondary tumours
– Leukaemia 50mGy
– Brain tumour 60mGy
• Lancet 2012;380:499-505

Imaging modalities
• Radiographs (X-rays)
• Scintigraphy (bone scan)
• CT
• MRI

Radiographs
What you see
• Bony anatomy and
alignment
• Disc height

Radiographs
What you see
alignment
• Disc height
Disadvantages
• Radiation
• Nonspecific
– OA changes in most
adults
• Insensitive
– No direct visualisation
of neural and other
nonbony structures

Bone scan
What you see
• Bone pathology
– Osteoblastic activity

Bone scan
What you see
• Bone pathology
– Osteoblastic activity
Disadvantages
• Radiation
• Very nonspecific
• Relatively poor
anatomical resolution
– (Improved with
SPECT; SPECT/CT)
– No direct visualisation
of neural and other
nonbony structures

CT
What you see
alignment
• Cross sectional view
of spinal canal and
foramina
• Disc, thecal sac,
nerve roots

CT
What you see
alignment
• Cross sectional view
of spinal canal and
foramina
• Disc, thecal sac,
nerve roots
Disadvantages
• Nonspecific
– Most adults have
‘findings’
• Poor visualisation of
individual neural
structures and disc
anatomy
• Radiation

MRI
What you see
alignment
• Bone pathology
• Multiplanar view of
spinal canal and
foramina
• Disc: hydration and
structure
• Neural structures:
cord, nerve roots

MRI
What you see
alignment
• Bone pathology
• Multiplanar view of
spinal canal and
foramina
• Disc: hydration and
structure
• Neural structures:
cord, nerve roots
Disadvantages
• Nonspecific
– Most adults have
‘findings’
• Availability
• Expense
– Rebate

MRI: T1
– Fat bright
• Bone marrow
– Bone cortex black
– Anatomy

MRI: T2
– Bone cortex black
– Anatomy
– Fluid bright
– Fat bright
• Bone marrow
– Oedema bright
• Difficult to
differentiate

MRI: STIR or T2FS
– Fat ‘saturated out’
• Bone marrow black
– Fluid bright
– Differentiate oedema
from marrow

MRI: T1FS-Gd
– Fat ‘saturated out’
• Bone marrow and other
fat black
– Non-fat T1 bright
• Haemorrhage
• Movement
• Enhancement
Pathology
Veins
Nerve root ganglia
T1 T1FS-Gd

Ineffectiveness of imaging for
nonspecific LBP
• Favourable natural Hx
– Most improve by 4 weeks; unaffected by imaging
• Nonspecificity: loose association between findings
and symptoms
– ‘Abnormalities’ or normal aging?
• Potential harms:
– Radiation
– ‘Labelling’
– Incidental findings
Ann Intern Med 2011;154:181-190

Degenerative changes on imaging
• Ubiquitous and nonspecific
Brinjikji AJNR 2015;36:811
Imaging Finding
Age (yr)
20 30 40 50 60 70 80
Disk degeneration 37% 52% 68% 80% 88% 93% 96%
Disk signal loss 17% 33% 54% 73% 86% 94% 97%
Disk height loss 24% 34% 45% 56% 67% 76% 84%
Disk bulge 30% 40% 50% 60% 69% 77% 84%
Disk protrusion 29% 31% 33% 36% 38% 40% 43%
Annular fissure 19% 20% 22% 23% 25% 27% 29%
Facet degeneration 4% 9% 18% 32% 50% 69% 83%
Spondylolisthesis 3% 5% 8% 14% 23% 35% 50%

Appropriate imaging for back
pain
• Clinical presentations: classification into 3 broad
categories
1. Nonspecific low back pain
2. Back pain associated with radiculopathy
3. Back pain associated with a specific cause requiring
prompt evaluation

Back pain categories
1. Nonspecific (mechanical) low back pain
– Acute: < 12 weeks
– Chronic: > 12 weeks
– Ligament/ muscle strain/ tear
– Intervertebral disc degeneration
– Osteoarthritis
– Facet joints
– SI joints
– Spondylolysis/ spondylolisthesis

2. Back pain associated with radiculopathy
a) Unilateral acute nerve root compression (sciatica)
– Leg pain >> back pain
– Disc herniation
a) Unilateral chronic nerve root compression
– Disc herniation or spinal stenosis
a) Bilateral chronic nerve root compression
– Spinal stenosis
– DD vascular claudication
a) Bilateral acute nerve root compression = ‘cauda equina
syndrome’

Cauda equina syndrome
• Bilateral acute nerve root compression
– Massive disc protrusion/ sequestration
• Sudden onset bilateral leg pain
• Saddle anaesthesia
• Rapidly progressive or severe neurological
deficits
– Motor deficits at >1 level
– Faecal incontinence
– Urinary retention

3. Back pain associated with a specific cause requiring
prompt evaluation
− Cauda equina syndrome
− Cancer
− Vertebral infection
− Vertebral compression fracture
− Ankylosing spondylitis (inflammatory
spondyloarthropathy)

LOW BACK PAIN GUIDELINES
Diagnostic triage
1. Non-specific LBP
2. Radiculopathy
3. Specific LBP
• ‘Red flags’
‘Red Flags’
• Cauda equina syndrome
• Known 10
tumour
• Weight loss
• Severe symptoms, not
settling
• Fever
• Recent infection or Sx
• Osteoporosis
• Steroid use
• Non-mechanical pain
• Child*

1.Focused Hx and examination to place patients
into 1 of 3 categories
2.No imaging for nonspecific LBP
3.Imaging for LBP + severe or progressive
neurological deficits OR risk factors for specific
cause
4.Imaging for LBP and radiculopathy if candidates
for surgery or epidural injection

• American College of Physicians & American
Pain Society Recommendations
– Ann Intern Med 2007;147:478-491
• Choosing Wisely Australia
– www.choosingwisely.org.au
• National Institute for Clinical Excellence (NICE)
UK
• ACR Appropriateness Criteria

www.imagingpathways.health.wa.gov.au

Diagnostic work-up
Possible cause Imaging Additional studies
Nonspecific LBP None None
Radiculopathy MRI (CT)
Cauda equina MRI
Cancer MRI for known 10
X-ray for other eg wt loss
Staging: bone scan; PSMA
ESR
Vertebral infection MRI ESR, CRP
Vertebral compression # X-ray
MRI pre vertebroplasty
Ankylosing spondylitis X-ray, incl pelvis (MRI) HLA-B27; ESR, CRP
Ann Intern Med 2007;147:478-491

NOMENCLATURE
• Consistent
• Reflect common usage where appropriate
• Surgically relevant
• ‘Able to visualize over the phone’
• 2 morphological characteristics:
– Nature of disc pathology
– Location
• Able to add further descriptors
– Neural structures
– Clinical context
• www.asnr.org/spine_nomenclature/reporting
• Spine Journal 2014;14:2525-2545

Annular tear/ fissure
• Annular fissure = degeneration
• Annular tear: outdated
– When ‘tear’ obvious result of trauma use the term
‘rupture’
• Annular high intensity zone (HIZ)
– Not synonymous with ‘fissure’
– Does not imply trauma
– Does not imply pain generator

Disc bulge
• Extension of disc tissue beyond intervertebral
disc space = displacement of annulus
• >25% circumference (>900
)
• Relatively short distance, <3mm
• Normal at L5/S1

Herniated disc
• Localised displacement of disc material beyond
intervertebral disc space (ie disrupted annulus) OR break in
vertebral end plate (Schmorl’s node)
• ‘Localised’ = <25% circumference (<900
)
– No longer divide into ‘broad based’ and ‘focal’
• ‘Herniation’ or ‘protrusion’
• Disc between but not beyond osteophyte OR adaptive to
subluxation/ listhesis is NOT herniation
• ‘HNP’ not accurate
– Herniation may include NP, cartilage, annulus, bone
• ‘Rupture’ tends to refer to trauma/ acute event
• ‘Prolapse’ and ‘bulging disc’ outdated

Protrusion vs extrusion
• Based on appearance
• Extrusion = greatest distance in any
plane between edges > base
OR
• Protrusion: contained
• Extrusion: uncontained = ruptured PLL
• Presence or absence of containment
more clinically relevant:
– Surgical approach
– Prediction of resorption

Sequestered disc
• Extruded disc material that has no continuity
with the disc of origin
• = free fragment
• Migrated disc:
– Disc material displaced away from site of extrusion

Location of herniation
• Anatomic system that correlates with surgery
• Landmarks, transverse plane:
– Sagittal and coronal planes at centre of disc
– Medial edge of articular facet
– Medial, lateral borders of pedicles

Location of herniation
• Locations, transverse plane:
– ‘Central’ = midline
– ‘Right central’ & ‘left central’ =
paracentral/ posterolateral
– ‘Subarticular’ = lateral recess
– ‘Foraminal’
– ‘Extraforaminal’ = far lateral

Volume: degree of canal
compromise
• X-sectional area at site of maximal narrowing
• ‘Mild’: <1/3
• ‘Moderate’: 1/3 – 2/3
• ‘Severe’: > 2/3
• Correlation with fluid around cauda and
‘crowding’ of neural structures
• Other descriptors such as compression of
specific neural structures

Modic 1
• Vascularised bone marrow
• Oedema
• Overlap with inflammatory
changes
T2 T1

Modic 2
• Proliferation of fatty tissue
• Most common form T2 T1

Modic 3
• Sclerotic bone
• Long standing
degenerative change
T2 T1

Nomenclature: summary
• No consensus for cervical and thoracic
• Cannot date disc pathology without serial
imaging
• Definitions based on morphology and pathology
• No implication of aetiology
• No distinction between symptomatic and
asymptomatic findings

Pars protocol
 LBP in 40% children and adolescents
 Structural causes 12-26%
 Pars defect = spondylolysis
 Common cause
 Pars interarticularis (interarticular
part) = weakest part of neural arch
 Often accelerated by athletic
activity
 2 key concepts:
 Spectrum of pars pathology
 DD: other causes of pain
12F

Pars pathology
 Developmental deficiency
 Asymmetry of posterior elements: laminae and facet
joints
 Traumatic fracture: uncommon
 Stress injury
 Chronic repetitive low grade trauma
 Oedema early
 Sclerosis or fracture/ defect later

Pars stress injury
 Lumbar, esp L5
 Often bilateral
 Spondylolisthesis
 Disc pathology
 Unilateral defect →
contralateral stress
 Symptoms:
 Often asymptomatic
 LBP
 Hamstring tightness
 Increased by activity

Imaging of LBP in children
 Radiography
 CT
 SPECT/ SPECT-CT
 RadioGraphics 2015;35:819-834
 MRI
 Radiation dose in
children
 Triple risk secondary
tumours
 Leukaemia 50mGy
 Brain tumour 60mGy
 Lancet 2012;380:499-505

Imaging of LBP in children
Radiography CT SPECT-CT MRI
Defect
•Recent
•Old
+/-
+/-
+
+
+
+
+
+
Stress
•Oedema
•Sclerosis
-
+
-
+
+
+
+
+
Spondylolisthesis + + + +
Disc changes
•Dehydration
•Narrowing/ end-
plate deformity
-
+
-
+
-
+
+
+

T1 GEFS STIR
11F gymnast, back pain
Fracture + oedema = acute

T1
STIR
18M
LBP
Fracture, corticated, no oedema = chronic

T1 GEFS STIR
16F Unilateral LBP
Incomplete defect + oedema = acute stress reaction/
partial defect

15M Bilateral pars defects, assess healing at 6 months
T1 STIR

T1 STIR
Oedema resolved, right unhealed, left healed

LBP in children: DD
 Pedicle fracture
 Unilateral
 Vertical
 Often contralateral pars
 Spinous process avulsion
 Stress fracture
 Transverse process
 Spinous process
 Sacrum

LBP in children: DD
 Disc degeneration
 Discitis
 Tumour eg osteoid osteoma
T2
T1

17F Left LBP, acute on chronic
T1 GEFS T2
Multiple findings:
Left pars defect + oedema
Degenerate discs L4/5, L5/S1
Muscle tear or denervation left multifidus

• Imaging appearances of disc herniation and
spinal stenosis
• Vertebroplasty
• A few cases

Indications
• Painful crush fracture
– Osteoporosis
– Acute: 4-6 weeks
• Malignant crush fracture
– +/- biopsy
• Haemangioma
– Galibert Neurochirurgie 1987;33:166-8

Patient selection = key to
success
• Back pain
– Sudden onset
– May radiate anteriorly
– NOT sciatica
– Mechanical
– Restricted activity
– Poor sleep
• Local tenderness
• Imaging

Imaging techniques
• MRI:
– Confirm presence of crush fracture
– Confirm that crush fracture is acute
– Diagnose other acute levels
– Integrity of spinal canal
– Accurately localise level

Post procedure care
• Lie prone for 20 minutes
• Bed rest for 2-3 hours
• Discharge if well
– Post-sedation instructions
– Rest 24 hours
– Mobilize according to pain
• Advise re muscle pain
• Follow-up phone call(s)

Complications: rare
• Mild fever; nausea for 24 hours
• Rib fracture
• Foraminal leak
• Spinal canal leak
• Venous emboli

My results
• Audit of first 250 patients, 2001 to 2006
• Complete or near complete response
– No or minimal pain
– Good return of activity level
– 83.0 %
• Moderate response
– Still suffer pain, though noticeably reduced
– Some return of activity, though still restricted
– 12.0 %
• No response
– 5.0 %

Percutaneous vertebroplasty
Keys to success
• Patient selection
– Early referral
– MRI
• High quality fluoroscopy
– Accurate needle placement
– Cement injection
• Nursing care
– Cement preparation
– Patient care: pre and post

So, what happened?
• Buchbinder NEJM 2009;361:557-68
– Multicentre, randomized, double blind
– Vertebroplasty vs placebo ‘sham’ procedure
– N = 78: 38 vertebroplasty, 40 sham
– No difference in pain scales or quality of life
• MJA (Editorial) 2009;191:476-7
– ‘Percutaneous vertebroplasty is not an effective
treatment for acute osteoporotic vertebral fractures’

• Patient selection
– Up to 12 months pain
• Recruitment
– Majority of eligible
patients not recruited
• Technique
– Up to 3ml cement
– Stopped injection if
leaking

Where are we now?
• Uncommon in most places
• Ongoing studies
– Clark Lancet 2016;388:1408-1416
– ‘Vertebroplasty is superior to placebo for pain
reduction in acute osteoporotic spinal fractures of less
than 6 weeks' in duration. These findings will allow
patients with acute painful fractures to have an
additional means of pain management that is known
to be effective’.
• Included in appropriateness guidelines in UK
and USA
• No Medicare rebate
• Our cost: 1200 + day bed about 700

• 68M
• Sudden onset bilateral leg pain and weakness
• Urinary retention

• Dx: Cauda equina syndrome
• Cause: massive sequestration
• Other causes:
– Tumour
• Primary of lower cord: ependymoma
• Primary of nerve: BPNST
• Primary of dura: meningioma
• Primary of vertebral body: chordoma, giant cell
tumour
• Secondary
– Trauma

Cauda equina syndrome
30M 60F 70M
T2

30M
T2 T1 T1FS con
T1 T1FS con

60F
T2 T1 T1FS con
T1 T1FS con

70M
T2 T1 T1FS con
T1 T1FS con

• 62 year old male
• Severe low back pain of rapid onset
• Febrile and unwell
• 4 weeks ago underwent abdominal surgery for
perforated diverticulitis

• 45 year old male
• 2 weeks post discectomy L4/5
• Recurrent bilateral leg pain

• Dx: recurrent disc:
– Central herniation + huge sequestration virtually filling
the spinal canal
• Note peripheral enhancement pattern
• DD: fibrosis

• 51 year old female
• Left sciatica
– Intermittent pain and paraesthesia

What is the most likely diagnosis?
1. Massive disc sequestration
2. Discitis complicated by abscess
3. Synovial cyst
4. Benign peripheral nerve sheath tumour

• Dx: benign peripheral nerve sheath tumour
(BPNST) of left L3 nerve root
– Many clinicians use the term ‘neuroma’
• Pathologically imprecise term
– Most are benign
• Schwannoma or neurofibroma
• Difficult (impossible) to differentiate on imaging
– BPNST is probably the best terminology
– Associated with NF1 and ‘NF2’ (MISME)

• 66 year old female
• Severe lower back pain on and off for years
• More recent (2 months) development of right
sciatica

• Severe OA of facet (zygoapophyseal) joints
• Round heterogeneous lesion projecting into right
spinal canal
• Note: close relationship to facet joint
• Dx: synovial cyst

Synovial cyst lumbar facet joint
• Fairly common
• Key is relationship to degenerate facet joint
• Density may vary from pure cyst to varying levels of
calcification and heterogeneity
• Usually present clinically with intractable sciatica
• May respond to aspiration and steroid injection, but
usually treated surgically

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