Whiplash causes increased laxity of cervical capsular ligament

Abstract

Background-Previous clinical studies have identified the cervical facet joint, including the capsular ligaments, as sources of pain in whiplash patients. The goal of this study was to determine whether whiplash caused increased capsular ligament laxity by applying quasi-static loading to whiplash-exposed and control capsular ligaments.Methods-A total of 66 capsular ligament specimens (C2/3 to C7/T1) were prepared from 12 cervical spines (6 whiplash-exposed and 6 control). The whiplash-exposed spines had been previously rear impacted at a maximum peak T1 horizontal acceleration of 8 g. Capsular ligaments were elongated at 1 mm/s in increments of 0.05 mm until a tensile force of 5 N was achieved and subsequently returned to neutral position. Four pre-conditioning cycles were performed and data from the load phase of the fifth cycle were used for subsequent analyses. Ligament elongation was computed at tensile forces of 0, 0.25, 0.5, 0.75, 1.0, 2.5, and 5.0 N. Two factor, non-repeated measures ANOVA (P<0.05) was performed to determine significant differences in the average ligament elongation at tensile forces of 0 and 5 N between the whiplash-exposed and control groups and between spinal levels.Findings-Average elongation of the whiplash-exposed capsular ligaments was significantly greater than that of the control ligaments at tensile forces of 0 and 5 N. No significant differences between spinal levels were observed.Interpretation-Capsular ligament injuries, in the form of increased laxity, may be one component perpetuating chronic pain and clinical instability in whiplash patients.

Spinal Facet Joint Biomechanics and Mechanotransduction in Normal, Injury and Degenerative Conditions

“…For simulations of whiplash exposures, the strains in the capsular ligament were found to be 2-5 times greater than those sustained during physiologic motions of the cervical spine [198]. In a similar but separate study, the facet joints of cervical spines that were previously exposed to a whiplash injury were then exercised under low-level tension and found to undergo elongations nearly three times greater than unexposed ligaments for the same tensile loads [194]. Those capsular ligaments were also found to exhibit greater laxity after the purported injury [194].…”

“…In a similar but separate study, the facet joints of cervical spines that were previously exposed to a whiplash injury were then exercised under low-level tension and found to undergo elongations nearly three times greater than unexposed ligaments for the same tensile loads [194]. Those capsular ligaments were also found to exhibit greater laxity after the purported injury [194]. Since increased laxity may be linked to a reduction in the joint's ability to stabilize the motion segment during sagittal motion [226], this finding suggests that whiplash exposure may alter the structure of the individual tissues of the facet, such as the capsular ligament, and/or the mechanotransduction processes that could maintain and repair the ligamentous structure.…”

“…Whiplashassociated disorders are particularly challenging in terms of understanding the biomechanics of the tissue injury and the physiological consequences because there is often no radiologic or other imaging evidence that reveals any obvious indicators of tissue trauma [200,222,223]. However, many volunteer and cadaveric studies have been performed to define the kinetics and kinematics of the cervical spine during vehicular rear impacts in order to define local tissue responses, their relationship to spinal kinematics, symptom and tissue injury risks, and tolerance for injury [8,194,[197][198][199]224,225]. More specifically, these investigations have focused on measuring the deformation imparted to the spinal tissues (ligaments and disc, mainly) by the rear impact and the associated changes in their mechanical properties.…”

Magnetic resonance imaging signal changes of alar and transverse ligaments not correlated with whiplash-associated disorders

“…But the pathogenesis of whiplash complaints is still poorly understood. Injury to longitudinal ligaments [5][6][7], facet joints [7,8], discs [7], spinal cord [9], or muscles [10,11] has been studied as possible sources of chronic pain. However, no detectable findings are significantly different from asymptomatic subjects, and there is no known association between structure damage and symptoms.…”

The Physiological Basis of Cervical Facet-Mediated Persistent Pain: Basic Science and Clinical Challenges

“…37,44,67,90 Mechanical facet capsule loading, in addition to having the potential to load nociceptive afferents embedded in it, also produces laxity under some conditions that produce pain. 39,70 All of these local tissue-loading environments have the potential to result in joint instability, which can lead to other alterations in the kinematics of the overall joint and its capsular ligament during normal activities. 41 Maximum principal strains quantify the greatest relative deformation in a tissue and are estimated using changes in the tissue configuration.…”