Dynamic intervertebral foramen narrowing during simulated rear impact.
METHODS
A biomechanical study of intervertebral foraminal narrowing during simulated automotive rear impacts.


OBJECTIVE
To quantify foraminal width, height, and area narrowing during simulated rear impact, and evaluate the potential for nerve root and ganglion impingement in individuals with and without foraminal spondylosis.


BACKGROUND
Muscle weakness and paresthesias, documented in whiplash patients, have been associated with neural compression within the cervical intervertebral foramen. To our knowledge, no studies have comprehensively examined dynamic changes in foramen dimensions.


METHODS
There were 6 whole cervical spine specimens (average age 70.8 years) with muscle force replication and surrogate head that underwent simulated rear impact at 3.5, 5, 6.5, and 8 g, following noninjurious baseline 2 g acceleration. Peak dynamic narrowing of foraminal width, height, and area were determined during each impact and statistically compared to baseline narrowing.


RESULTS
Significant increases (P < 0.05) in average peak foraminal width narrowing above baseline were observed at C5-C6 beginning with 3.5 g impact. No significant increases in average peak foraminal height narrowing were observed, while average peak foraminal areas were significantly narrower than baseline at C4-C5 at 3.5, 5, and 6.5 g.


CONCLUSIONS
Extrapolation of the present results indicated that the highest potential for ganglia compression injury was at the lower cervical spine, C5-C6 and C6-C7. Acute ganglia compression may produce a sensitized neural response to repeat compression, leading to chronic radiculopathy following rear impact.
Panjabi
Manohar M
MM
Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, CT 06520-8071, USA. manohar.panjabi@yale.edu
Maak
Travis G
TG
Ivancic
Paul C
PC
Ito
Shigeki
S
D000063:Accidents, Traffic; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae / Q000293:injuries / Q000473:pathology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D013115:Spinal Canal / Q000293:injuries / Q000473:pathology* / Q000503:physiopathology; D013117:Spinal Cord Compression / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D013119:Spinal Cord Injuries / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D014911:Whiplash Injuries / Q000150:complications / Q000473:pathology* / Q000503:physiopathology