Appropriateness Criteria in the evaluation of back pain

Edgar Colón Negrón, MD

Angel Gómez Cintrón, MD, MPH

Diagnostic Radiology

UPR-RCM

www.acr.org

UNIVERSITY OF PUERTO RICO · SCHOOL OF MEDICINE · DIAGNOSTIC RADIOLOGY

Introduction• Acute low back pain is the leading cause of

disability for persons younger than 45 in the US• High prevalence and high cost in dealing with this

problem• After multiple studies it is clear that uncomplicated

LBP is a benign self-limited condition that does not warrant any imaging studies

• Vast majority of patients are back to their usual activities in 30 days

• The challenge for the clinician is to distinguish who should be evaluated to exclude a more serious problem

Indications for radiographic evaluation of the spine

• Red Flags:

– Significant trauma, or milder if age >50– Unexplained weight loss– Unexplained fever– Immunosuppression– History of Cancer– IV Drug use– Osteoporosis, prolonged use of steroids– Age > 70– Focal neurologic deficit or disabling symptoms– Duration longer than 6 weeks

Imaging Modalities

• Plain films• Bone scintigraphy• CT• MRI• Myelography

Plain films

• Inexpensive• Available• Screening ( trauma )• Assessment of subluxation and alignment

Normal AP, Lat, Obl and Swimmer’s view of cervical spine

Look for alignment, vertebral body shape, posterior elements and prevertebral soft tissues. Examination must include C7. Oblique views forevaluation of uncovertebral joints, neural foramina stenosis and facet alignment

Legend:1, v. body2, transverse process 3, posterior arch atlas4, 5 facet joints6, lamina7, spinous process8, uncinate process10, disc space11, articular facet joint12, left neural foramina14, pars interarticularis15, pedicle

Indications for radiographic evaluation of the spine

• Red Flags:– Significant trauma, or milder if age >50– Unexplained weight loss– Unexplained fever– Immunosuppression– History of Cancer– IV Drug use– Osteoporosis, prolonged use of steroids– Age > 70– Focal neurologic deficit or disabling symptoms– Duration longer than 6 weeks

Isotope Bone Scan

• Moderately sensitive for the presence of tumors, infection or occult fractures; not specific

• Bone scintigraphy with SPECT followed with CT is more sensitive in the diagnosis of spondylolysis than MR

• SPECT may localize the source of pain in patients with articular facet OA

CT of the spine

• Superior bone detail, not as useful as MR in depicting disc protrusions

• CT is useful in depicting spondylolysis• Poor visualization of the cord, intrathecal

contrast needed.• Great technique for the assessment of

pseudoarthosis, scoliosis, post surgical evaluation of bone graft integrity, surgical fusion and instrumentation

MRI

• Examination of choice in complicated LBP• Multidisciplinary agreement on terminology

facilitates reporting of MR findings• No radiation• Excellent contrast resolution• Multiplanar capabilities• Great visualization of the spinal cord

– Higher soft tissue contrast than CT

MR in low back pain

• Acute back pain with radiculopathy suggests the presence of demonstrable nerve root compression on MR

• MR findings of Modic endplate changes, anterolisthesis or disk extrusion are more strongly associated with low back pain than disk changes without endplate changes

• Particularly efficacious in the detection of red flags diagnosis

• Post operative patients enhanced MR allows distinction between disc and scar tissue

T1 (left) and T2 (right) weighted images of a normal dorsal spine

T2 weighted images ofthe lumbar spine. Extreme parasagital views demonstratingroot foraminas

dorsal root ganglion

T2 T1

Normal Lumbar Spine

CT vs MRI

Imaging in the diagnosis of spinal diseases

Degenerative diseases and back pain; epidemiologic facts

• Affects 5% of the adult population per year with a lifetime incidence of 70%-80%

• 90% of patients recover within 3 months• 286,000 surgeries per year • The estimated cost of this entity to the society is

between 16 – 60B, with 10B in direct medical care alone

• 2B in MRI alone

Modic MT, MRI Clinics of North Amer, Aug 1999

Spinal Degeneration

• Normal consequence of the aging process, that can be predisposed or accelerated by developmental and acquired factors

• Two major degenerations;– Osteochondral which affects the intervertebral

disc ( synchondral articulation)– Osteoarthritic affecting the synovial joints

(uncovertebral joints in the cervical spine and the facet joints)

Multisegmental degenerative osteochondral changes

Sagital fluid sensitivePulse sequences

Normal sagital fluid sensitivePulse sequence

T2 T1

annular fissure

Spinal canal stenosis

Degenerative osteoarthritic changes to the right uncovertebral joint of the cervical spine with nerve root foramina narrowing

Annular displacement

Displacement of the nucleus pulposus (disc herniations)

• Due to degeneration of the annular fibers• Displacement can be superior, inferior or

most commonly posterior• Definition

– Protrusion: within the annulus, annular fissure– Extrusion: beyond the annulus but contained by

the PLL– Sequestrum = free fragment

A-C normal variants, D protruded , E extruded, F and G free fragments

Degenerative osteochondral changes in the with resultant

end plate herniations (Schmorl’s nodes)

Protruded disc

T2 T1

small annular fissures

Central extruded disc limited by the posterior Longitudinal ligament

Free fragment

Correlation of symptoms

• The three most important for localization and causal differential are:– Pain– Sensory changes– Weakness

Patients more likely to have a favorable outcome from surgery should have;

- A clear history of sciatica- Straight leg raising of less than 30- Objective neurologic signs- Imaging evidence of a disc herniation

that corresponds with the anatomical area of concern

Poor surgical outcome is likely when treating for;- Disc disruption syndrome- Degenerative segmental instability- Bulging discs- Pain alone

When to use contrast?

• Post operative spine, failed back syndrome• Evaluation of infection• Metastatic disease• R/O intramedullary lesion

Axial T1WI pre and post gadolinium injection demonstrating scar at surgical site

Contrast enhancement is needed for all post op patients.

Relative Radiation Level

• “There is potential for adverse health effects associated with radiation exposure, therefore it is an important factor to consider when ordering imaging studies.”

• RRL is used to estimate population total radiation risk associated with an imaging procedure.

The bottom line

• Imaging correlates with outcome only when combined with clinical data

• Most patients with low back pain will go into clinical response and may not need imaging procedures unless a red flag is raised

• Knowing of the red flags is important in order to perform the most appropriate imaging procedure, when needed

• Back pain will continue to be an important clinical topic in the near future due to its economic implications.

Remember the RED FLAGS

– Significant trauma, or milder if age >50– Unexplained weight loss– Unexplained fever– Immunosuppression– History of Cancer– IV Drug use– Osteoporosis, prolonged use of steroids– Age > 70– Focal neruologic deficit or disabling symptoms– Duration longer than 6 weeks

Reference

• ACR Appropriateness Criteria ©

•acr.org