Total cervical translation as a function of impact vector as measured by flexion-extension radiography.

BACKGROUND Clinical and cadaveric studies have implicated that sub-failure cervical instability likely occurs in a subset of whiplash injury patients. Cadaveric studies have suggested that female specimens suffer from more ligamentous stretch injury than males when exposed to simulated rear end crash vectors. However, these findings have never been tested in an in-vivo clinical setting. DESIGN A prospective evaluation of total cervical translation on sagittal flexion radiographs versus impact vector in a late whiplash population. OBJECTIVES To determine if total cervical translation on radiographs is correlated with impact crash vector. METHODS Consecutive late whiplash patients in a subspecialty pain clinic setting were sent for radiographs using a strict stress flexion-extension protocol. Information concerning crash vector and damage was recorded. Vertebral translation was read by a blinded reader and recorded. RESULTS Males did not significantly differ in total translation in flexion-extension radiographs when involved in sagittal plane crashes (n=75) compared to coronal plane crashes (n=10). In a front end collision, males (n=16) and females (n=26) did not differ in total translation in flexion-extension radiographs. In a rear end collision, females (mean translation 4.61 mm, n=103) did differ significantly in total translation in flexion-extension radiographs from their male counterparts (mean translation 3.29, n=48) (P<0.001). CONCLUSION This investigation suggests that specific crash vectors lead to particular patterns of radiographic translation in female subjects. A realization that sub-failure cervical instability occurs in whiplash may help design more effective treatments.