Head-Turned Postures Increase the Risk of Cervical Facet Capsule Injury During Whiplash

• Published in: Spine (Philadelphia, Pa. 1976) Vol. 33; no. 15; pp. 1643 - 1649
• Main Authors: SIEGMUND, Gunter P, DAVIS, Martin B, QUINN, Kyle P, HINES, Elizabeth, MYERS, Barry S, EJIMA, Susumu, ONO, Kishiri, KAMIJI, Koichi, YASUKI, Tsuyoshi, WINKELSTEIN, Beth A
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA Lippincott 01-07-2008; Hagerstown, MD
• Subjects: Analysis of Variance; Biological and medical sciences; Cadaver; Cerebrospinal fluid. Meninges. Spinal cord; Cervical Vertebrae - injuries; Cervical Vertebrae - physiology; Female; Humans; Injuries of the nervous system and the skull. Diseases due to physical agents; Joint Capsule - injuries; Joint Capsule - physiology; Medical sciences; Nervous system (semeiology, syndromes); Neurology; Posture - physiology; Risk Factors; Torque; Traumas. Diseases due to physical agents; Whiplash Injuries - physiopathology; Motion; Nervous system diseases; Vertebral canal; Coup de fouet syndrome; Whiplash injury; Joint; coupled motion; Rotation; Head turn; Posture; Strain; Osteoarticular system; Eye disease; Central nervous system disease; Risk factor; axial rotation; Neck; Oculomotor syndrome; Spinal cord disease; zygapophysial joint; Facet; tissue strain
• ISSN: 0362-2436; 1528-1159
• DOI: 10.1097/BRS.0b013e31817b5bcf

In vitro experiments using cadaveric cervical spine motion segments to quantify facet capsular ligament strain during whiplash-like loading.
To quantify facet capsule strains during whiplash-like loading with an axial intervertebral prerotation simulating an initial head-turned posture and to then compare these strains to previously-published strains for partial failure and gross failure of the facet capsule for these specimens.
Clinical data have shown that a head-turned posture at impact increases the severity and duration of whiplash-related symptoms.
Thirteen motion segments were used from 7 women donors (50 +/- 10 years). Axial pretorques (+/-1.5 Nm), axial compressive preloads (45, 197, and 325 N), and quasi-static shear loads (posteriorly-directed horizontal forces from 0 to 135 N) were applied to the superior vertebral body to simulate whiplash kinematics with the head turned. Three-dimensional displacements of markers placed on the right facet capsular ligament were used to estimate the strain field in the ligament during loading. The effects of pretorque direction, compression, and posterior shear on motion segment motion and maximum principal strain in the capsule were examined using repeated-measures analyses of variance.
Axial pretorque affected peak capsule strains more than axial compression or posterior shear. Peak strains reached 34% +/- 18% and were higher for pretorques toward rather than away from the facet capsule (i.e.-, head rotation to the right caused higher strain in the right facet capsule).
Compared to previously-reported data for these specimens, peak capsule strains with a pretorque were double those without a pretorque (17% +/- 6%) and not significantly different from those at partial failure of the ligament (35% +/- 21%). Thus a head-turned posture increases facet capsular ligament strain compared to a neutral head posture-a finding consistent with the greater symptom severity and duration observed in whiplash patients who have their head turned at impact.