Diagnostic Imaging

Diagnostic Imaging is a snapshot of living Anatomy!

“Normal” anatomical variation and pathoanatomy – you MUST know your anatomy and pathology well to understand and interpret diagnostic imaging reports and images! If you are weak in anatomy it is time to ‘bone-up’ – pun intended 🙂

Order diagnostic imaging only if there is high likelihood that information will lead to a change in treatment.

When is diagnostic Imaging warranted; is using this diagnostic imaging technique going to…
- …rule out/rule in a pathology? (cancer, fracture, etc.)
- …change my diagnosis or treatment options?
If the Answer is NO then don’t waste the patient’s or your own time & money!

Selected Imaging Modality Uses

Special Imaging Choices ♦♦♦ = excellent ♦♦ = good ♦ = fair
Condition	Xray	CT	MRI	Bone Scan	Ultrasound
Disc Herniation		♦♦	♦♦♦
Infection		♦♦	♦♦♦	♦♦
Inflammatory. Arthropathy	♦♦	♦
Instability	♦♦♦				♦♦♦
Neoplasm	♦	♦♦	♦♦♦	♦♦
Spondylolisthesis	♦♦♦	♦		♦ (acute)
Stenosis		♦♦♦	♦♦
Trauma	♦♦	♦♦ bone	♦♦♦ soft tissue
Blood Flow or Aneurysm		♦♦♦	♦♦♦		♦♦♦
Metabolic Activity			♦♦	♦♦♦

Diagnostic ultrasound – mainly used to detect soft tissue abnormalities, abdominal aortic aneurysm, genitourinary abnormalities or during pregnancy

Video fluoroscopy – limited use in LBP, may be used in flexion/extension functional studies, high radiation exposure – thus of little clinical use

General Concepts

Few patients with low back pain require plain film radiographs, even fewer require special imaging
Considerations in selecting appropriate imaging examination for individual patients:
Inherent risk of examination to patient
Likelihood that examination will be of benefit in establishing or refuting a diagnosis
Potential risk of liability if examination is requested or not requested
Patient selection (those who require or do not require diagnostic testing)
Indicated by findings obtained by patient’s history & physical examination
Is diagnostic study going to help confirm a diagnosis & if so how much?
Will study information change diagnostic thinking, significantly changing choice of treatment?

Order diagnostic imaging only if there is high likelihood that information will lead to a change in treatment.

High Risk Patients – patients with clinical indications (history & exam findings):

History: significant trauma, > 50 years old, neuromotor deficits, unexplained weight loss, ankylosing spondylitis, drug or alcohol abuse, history of cancer, corticosteroid use, fever > 100°F, no improvement in condition
Exam: cachexia, deformity & immobility, scars (surgical, accidental), lymphadenopathy, motor or sensory deficit, elevated ESR or ALP, (+) RH factor, (+) HLA-B27 antigen, serum gammopathy

Low Risk – patients that fail to exhibit any of high-risk signs of symptoms. These patients seldom exhibit significant abnormalities on radiographs & therefore findings will not alter treatment

Plain Film Radiography in Low Back Pain: When is it reasonable?

Pathologic Diagnosis

To establish or confirm a clinical (pathologic) diagnosis
High risk patients most probable of pathologic radiograph on initial visit
Low risk patients (absence of neurologic deficit) radiographs are contradicted during first week of acute episode of low back pain & probably are unnecessary unless symptoms persist for a 7-week period (Quebec Task Force on Spinal Disorders)
Frontal & lateral views are indicated at time of initial examination for high risk patients
Special views are indicated in high risk patients only when frontal & lateral films are insufficient or equivocal
Plain film radiographs are typically used as first imaging procedure in patients requiring imaging because: accessible, inexpensive, comfortable, convenient for patient & involves only minimal radiation exposure
Sensitivity for plain film = 90% for many conditions
For bone destruction (ie. malignancy, infection) 30-50% destruction must be present to view on plain film; 3-5% bone destruction necessary on radionuclide bone scans (more sensitive/less specific)
Plain film is insensitive to many diagnoses: spinal stenosis, herniated nucleus pulposus, intraspinal neoplasms~ require more expensive imaging methods
The role of radiography in evaluating biomechanics & posture is controversial
Scoliosis: full spine radiographic evaluation of patients with scoliosis is an effective diagnostic & analytic procedure with an effective risk/benefit ratio
Spinographic analysis: with exception of disc space narrowing it is an unreliable predictor of present or prior history of low back complainants; with exception of scoliosis there is no clinical justification for taking radiographs exclusively for spinographic analysis
Functional radiography: functional or “stress” radiography has been used extensively in orthopedic practices in an attempt to identify & explain biomechanical abnormalities that might contribute to low back pain
Lateral bending or flexion/extension studies
Generally excepted that greater than 3 mm of translational movement & greater than 10° angular motion (L1-L4) represents instability
Greater than 4 mm & 20° (L5-S1) represent instability
Lumbosacral anomalies (tropism, transitional vertebrae, spina bifida, & Schmorl’s nodes) reveal no higher incidence of back pain than in patients without these abnormalities
Leg length inequality studies may have an increased incidence of back pain
Radiographic findings of vertebral anomalies & pelvic tilt may mislead clinician & patient & they frequently lead to inappropriate diagnosis
Use of radiographic screening to identify contraindications to care is unjustified
Most conditions that contraindicate treatment are evident via history and/or physical examination (high risk patients) or other diagnostic methods
Radiographs are almost always contraindicated because treatment will not be altered
Exceptions are: progressive scoliosis, unstable degenerative spondylolisthesis or severe degenerative spinal stenosis (CT, MRI) or flexion-extension studies, identification of anomalies, contraindication screening, monitoring degenerative processes