Epidemiology of Whiplash
- Chronic pain occurs in 15% to 40% of patients after a whiplash injury
- Disc problems account for the minority of injuries
- Studies show that prevalence of chronic facet pain is as high as 54%-60% in whiplash patients
- In high speed accidents facet pain prevalence as high as 88%
Biomechanics
- Up to 10G’s applied to spine at 9 MPH
- Physiological disc limits exceeded everywhere but C4/5 disc at 10G’s
- Peak G forces in rear impact reached at lower speeds vs. frontal impacts
- Facet joint can be injured as low as 3.5G’s and speeds as low as 5 MPH
- Facet joints injured at much lower threshold than disc
Causes of Chronic Pain
- Sprains and strains resolve within 6 weeks.
- After 6 weeks injury is chronic
- 8%-33% of cases due to disc injury
- C5/6 is the most commonly injured disc
- 66%-90% of cases due to facet injury
- C2/3 facet injury is the most common cause of upper neck pain
- C5/6 facet injury is the most common cause of lower neck pain
- A disc herniation will commonly be associated with facet injury at the same or different level
Diagnosis of Herniation
- On standard MRI it is often impossible to distinguish disc herniation from degenerative spur
- Degenerative spurs are painless and pre-exiting
- Gradient echo (GE) MRI will distinguish spur from disc herniation
Spur or herniation?
Bright on GE MRI means herniation
Diagnosis of Facet Injury
- Imaging cannot be relied on to diagnose facet injury (SIS, AAPMR, ASIPP guidelines)
- Medial branch block is the only established means of diagnosis
- Positive blocks are “prima facie” evidence of facet injury
- Indications for blocks: Desire to know cause of chronic pain with non-elucidating MRI
Treatment of Facet Injury
- Cervical rhizotomy is a safe and validated out-patient means of treatment
- Largest published study co-authored by Dr. Rappard on behalf of Spine Intervention Society
- 2/3rd of patients pain free at 6 month follow up
- 2/3rd of patients require no additional procedures
- No significant recovery time or complications
- Significant value to chronic neck cases
Cervical Facet Injury Litigation Results
- 123 settled/litigated cases reviewed
- 2 cases tried in court
- Negative or degenerative MRI in almost all cases
- No indication for more invasive surgery
- Often only alternative treatment offered was epidural injection
- Average settlement $146,000
