Neck ligament strength is decreased following whiplash trauma

Abstract

BackgroundPrevious clinical studies have documented successful neck pain relief in whiplash patients using nerve block and radiofrequency ablation of facet joint afferents, including capsular ligament nerves. No previous study has documented injuries to the neck ligaments as determined by altered dynamic mechanical properties due to whiplash. The goal of the present study was to determine the dynamic mechanical properties of whiplash-exposed human cervical spine ligaments. Additionally, the present data were compared to previously reported control data. The ligaments included the anterior and posterior longitudinal, capsular, and interspinous and supraspinous ligaments, middle-third disc, and ligamentum flavum.MethodsA total of 98 bone-ligament-bone specimens (C2–C3 to C7-T1) were prepared from six cervical spines following 3.5, 5, 6.5, and 8 g rear impacts and pre- and post-impact flexibility testing. The specimens were elongated to failure at a peak rate of 725 (SD 95) mm/s. Failure force, elongation, and energy absorbed, as well as stiffness were determined. The mechanical properties were statistically compared among ligaments, and to the control data (significance level: P < 0.05; trend: P < 0.1). The average physiological ligament elongation was determined using a mathematical model.ResultsFor all whiplash-exposed ligaments, the average failure elongation exceeded the average physiological elongation. The highest average failure force of 204.6 N was observed in the ligamentum flavum, significantly greater than in middle-third disc and interspinous and supraspinous ligaments. The highest average failure elongation of 4.9 mm was observed in the interspinous and supraspinous ligaments, significantly greater than in the anterior longitudinal ligament, middle-third disc, and ligamentum flavum. The average energy absorbed ranged from 0.04 J by the middle-third disc to 0.44 J by the capsular ligament. The ligamentum flavum was the stiffest ligament, while the interspinous and supraspinous ligaments were most flexible. The whiplash-exposed ligaments had significantly lower (P = 0.036) failure force, 149.4 vs. 186.0 N, and a trend (P = 0.078) towards less energy absorption capacity, 308.6 vs. 397.0 J, as compared to the control data.ConclusionThe present decreases in neck ligament strength due to whiplash provide support for the ligament-injury hypothesis of whiplash syndrome.

Strain rate dependent properties of younger human cervical spine ligaments

“…Damage to these ligaments has been associated with injuries, such as neck strain (Webb et al, 1976;Harris et al, 1992) and whiplash associated disorders Tominaga et al, 2006;Ito et al, 2004). The mechanical properties of the cervical spine ligaments are needed for a younger population, at relevant strain rates, for more accurate predictions of head/neck kinematic response and the prediction of injury using detailed finite element models.…”

Characterization of Acute and Chronic Whiplash-Associated Disorders

“…It was proposed that microscopic subfailure injuries of the segmental cervical ligaments may injure embedded mechanoreceptive and nociceptive nerve endings, and thereby lead to pain, inflammation, and chronic symptoms. 121 Upper cervical ligament injuries have also been proposed as a factor in the development of chronic WAD symptoms, and support for such lesions can be found in studies using high-resolution protondensity-weighted MRI, demonstrating high signal intensity (indicative of damage) in both the alar and transverse ligaments, and in the tectorial membrane in some subjects with chronic WAD. 71 Later follow-up studies indicated a strong relationship between severity of alar ligament damage, head position (turned at time of impact), Neck Disability Index (NDI) 128 scores, 62,63 and reproduction of pain and excessive mobility with the manual examination techniques for the upper cervical ligaments.…”

“…40,50 Ligamentous injuries in the mid-and lower-cervical segments have also been suggested as contributing to the development of persistent symptoms following a whiplash injury. Tominaga et al 121 demonstrated reduced strength, subfailure injury, and altered mechanical properties of cervical spine ligaments secondary to simulated rear-end vector impact injuries. It was proposed that microscopic subfailure injuries of the segmental cervical ligaments may injure embedded mechanoreceptive and nociceptive nerve endings, and thereby lead to pain, inflammation, and chronic symptoms.…”

Retropharyngeal abscess with secondary osteomyelitis and epidural abscess: proposed pathophysiological mechanism of an underrecognized complication of unstable craniocervical injuries: case report

“…16,33,47 Ivancic et al found that the ruptured ligaments were associated with significantly greater dynamic intervertebral extension, peak ligament strain, and joint laxity compared with the uninjured ligaments.…”

“…12 In vitro investigations have demonstrated that transection or injury to the anterior longitudinal ligament (ALL) and anterior annulus resulted in increased flexibility under extension loading, implying that injury to these components could lead to instability. 16,33,47 Ivancic et al found that the ruptured ligaments were associated with significantly greater dynamic intervertebral extension, peak ligament strain, and joint laxity compared with the uninjured ligaments. 16 We also agree that these lacerations in the ALL could serve as the path through which the infection could progress to osteomyelitis and epidural abscess.…”