Dynamic elongation of the vertebral artery during an in vitro whiplash simulation

Vertebral artery compression of the medulla oblongata: A benign radiological finding?

Background:

To the best of our knowledge, no study has documented the natural history of rostral medullary compression of the vertebral artery (RMCVA) as radiological finding. The aim of this study was to explore it.

Methods:

A total of 57 patients with RMCVA and not presenting symptoms of medullary compression syndrome were enrolled. These participants underwent cerebral magnetic resonance imaging with contrast, and 19 of them who were followed for 5.7 ± 1.9 years (range: 3.0–10.3 years) were analyzed in detail. For comparison, clinical courses of two other patients with vertebrobasilar dolichoectasia (VBDE) were presented.

Results:

RMCVA was well delineated in all 57 patients. In the 19 patients analyzed, RMCVA was found in 17 sides on the right and 15 on the left. Moreover, the ventrolateral medulla was the most frequent compression site, and it was found in 69% of cases, with 84.2% presenting as mild compression and 15.8% as considerable compression. During the follow-up period, no patients showed neurological deterioration or radiological progression. In contrast, the two VBDE patients demonstrated both neurological and radiological progressions during the follow-up period.

Conclusion:

Unlike VBDE, RMCVA seems to be a benign condition without progression, even when with a considerable compression. Degree of the compression in RMCVA may not be relevant to the patient’s neurological status.

The Hemodynamic Response of the Vertebral Artery to 3 Time Durations of the Static Stretching Exercise in the End Position of Contralateral Cervical Rotation

OBJECTIVES

To evaluate the effect of 3 different time durations of sustained end-range cervical rotation during static stretching exercises on the hemodynamics of the vertebral artery.

METHODS

This observational study used Doppler ultrasonography to measure the average vertebral artery hemodynamics at the sustained end-range cervical rotation after 3 time durations of static stretching exercise: 10 seconds, 30 seconds, and 60 seconds. The sustained end-range cervical rotation was applied to 30 asymptomatic male participants.

RESULTS

The peak systolic velocity 35.2 ± 6.9 cm/s and the end systolic velocity 12.7 ± 1.6 cm/s reduced significantly, while resistive index 0.74 ± 0.03 increased after 60 seconds of sustained end-range contralateral cervical rotation by 39.1%, 32.4%, and 8.8%, respectively, compared with the neutral position. There were no significant differences found between peak systolic velocity and resistive index after a stretching duration of 60 and 30 seconds. Similarly, there were no notable changes in end systolic velocity when comparing 10 seconds with 30 seconds.

CONCLUSION

The static stretching exercise using sustained end-range cervical rotation for 60 seconds induced marked changes in the hemodynamics of the vertebral artery.

Vertebral Artery Dissection in Sport: A Systematic Review

BACKGROUND

Vertebral artery dissection (VAD) is a potentially catastrophic injury that may occur during sports participation. A comprehensive review is needed to collate documented cases to improve understanding and inform future preventative approaches.

OBJECTIVE

This review aimed to understand the extent of VAD in sport and characterise trends suggestive of mechanisms of injury.

METHODS

Electronic databases were searched using terms related to VAD and sport. Records were included if they described one or more cases of VAD attributed to sport.

RESULTS

A total of 79 records described 128 individual cases of VAD in sport, of which 118 were confirmed by imaging or autopsy and included in analyses. Cases were attributed to 43 contact and non-contact sports. The median age of cases was 33 years (IQR 22-44), and 75% were male. There were 22 cases of fatal injury, of which ten involved an impact to the mastoid region and seven involved an impact to the head or neck. Non-fatal cases of VAD were attributed to impact to the head or neck (not mastoid region), movement or held position without impact, and in some cases no reported incident.

CONCLUSIONS

VAD attributed to sports participation is uncommonly reported and the mechanisms are varied. Impact to the mastoid region is consistently implicated in fatal cases and should be the focus of injury prevention strategies in sport. Efforts may also be directed at improving the prognosis of cases with delayed presentation through clinical recognition and imaging. The review was registered on the international prospective register for systematic reviews ( http://www.crd.york.ac.uk/PROSPERO ) (CRD42018090543).

Dynamic vertebral artery elongation during frontal and side impacts

BACKGROUND CONTEXT

Elongation-induced vertebral artery (VA) injury has been hypothesized to occur during nonphysiological coupled head motions during automobile impacts. Although previous work has investigated VA elongation during head-turned and head-forward rear impacts, no studies have performed similar investigations for frontal or side impacts.

PURPOSE

The present study quantified dynamic VA elongations during simulated frontal and side automotive collisions, and compared these data with corresponding physiological limits.

STUDY DESIGN/SETTING

In vitro biomechanical study of dynamic VA elongation during simulated impacts.

METHODS

A biofidelic whole cervical spine model with muscle force replication and surrogate head underwent simulated frontal impacts (n=6) of 4, 6, 8, and 10 g or left side impacts (n=6) of 3.5, 5, 6.5, and 8 g.

RESULTS

Average (SD) maximum physiological VA elongation was 7.1 (3.2) mm, measured during intact flexibility testing. Average peak dynamic elongation of right VA during left side impact, up to 17.4 (2.6) mm, was significantly greater (p<.05) than physiological beginning at 6.5 g, whereas the highest average peak VA elongation during frontal impact was 2.5 (2.4) mm, which did not exceed the physiological limit. Side impact, as compared with frontal impact, caused earlier occurrence of average peak VA elongation, 113.8 (13.5) ms versus 155.0 (46.2) ms, and higher average peak VA elongation rate, 608.8 (99.0) mm/s versus 130.0 (62.9) mm/s.

CONCLUSIONS

Elongation-induced VA injury is more likely to occur during side impact as compared with frontal impact.

Vertebral artery injury after blunt cervical trauma: an update

BACKGROUND

Vertebral artery injury (VAI) after blunt cervical trauma has been considered to be rare. The incidence of VAI has increased dramatically within the last decade after a heightened awareness of this entity on the part of spine surgeons. Diagnostic or therapeutic guidelines for VAI have not been established fully, however.

METHODS

A review of the literature published between 1990 and 2004 was conducted.

RESULTS

The incidence of VAI among total blunt trauma admissions ranged from 0.20% to 0.77%. Most VAI patients remained asymptomatic, but sudden unexpected deterioration was often reported. Distraction/extension, distraction/flexion, and lateral flexion injuries were the major mechanisms of injury. Dissection and occlusion were the frequent vascular injury patterns. Facet joint dislocations and the fractures extending into the transverse foramen were the spine injury patterns closely associated with VAI. Digital subtraction angiography was the most sensitive imaging study, but because of invasiveness, its role as a screening study remained questionable. Neuroradiological intervention was used successfully to treat hemorrhagic VAI and progressing vertebrobasilar stroke. Systemic anticoagulation with heparin was the preferred treatment for mild ischemia. Treatment of asymptomatic patients has been controversial because the natural history of VAI has not been elucidated. Prophylactic anticoagulation with heparin or the use of antiplatelet agents was advocated in recent studies.

CONCLUSIONS

Preemptive treatment may be reasonable in selected patients considering the devastating potentials of VAI. The potential risks of heparin or antiplatelet agents in relation to early cervical spine surgery have not been addressed fully, however, and spine surgeons have to weigh the risk and benefit of such treatment cautiously.

Calculation of dynamic spinal ligament deformation

OBJECTIVE

Previous methods to determine spinal ligament deformation have included either custom-designed transducers or computational methods using rigid body transformation of kinematic data. Goals of the present study were to describe a computational methodology to determine dynamic deformations of an arbitrarily oriented ligament in a spine specimen and its associated errors.

METHODS

Calculation of ligament deformation in a spinal segment with vertebral motion tracking flags utilized digital stereophotography, lateral neutral posture radiograph, and detailed quantitative anatomy to develop geometrical relationships between flag markers and ligament attachment points. A custom jig, consisting of two flags each with four markers, was constructed to quantify errors associated with computed ligament deformation, flag marker translation, and flag rotation.

RESULTS

Average error in ligament deformation was dependent upon motion direction and ranged between 0.03 mm (SD 0.45 mm) and 0.28 mm (SD 0.18 mm). Average error for flag marker translation ranged between 0.02 mm (SD 0.14 mm) and 0.11 mm (SD 0.39 mm), and for flag rotation ranged between -0.06 degrees (SD 0.17 degrees ) and 0.07 degrees (SD 0.12 degrees ).

CONCLUSIONS

Accuracy of the present technique was equivalent to or greater than that of previous methods. The present technique utilized relatively cost-effective digital stereophotography, and may be used to calculate strain in ligaments not readily accessible for transducer application. The methodology has wide-spread applicability for analyses of dynamic or static spinal or other ligament strains, and may be used to determine spinal canal and intervertebral foramen narrowing and area reduction.

Effect of rotated head posture on dynamic vertebral artery elongation during simulated rear impact

BACKGROUND

Elongation-induced vertebral artery injury has been hypothesized to occur during non-physiological coupled axial rotation and extension of head. No studies have quantified dynamic vertebral artery elongation during head-turned rear impacts. Therefore, we evaluated effect of rotated head posture vs. forward head posture at the time of impact on dynamic vertebral artery elongation during simulated rear impacts.

METHODS

A whole cervical spine model with surrogate head and muscle force replication underwent either simulated head-turned (n = 6) or head-forward (n = 6) rear impacts of 3.5, 5, 6.5 and 8 g. Continuous dynamic vertebral artery elongation was recorded using custom transducer and compared to physiological values obtained during intact flexibility testing.

FINDINGS

Average (SD) peak dynamic vertebral artery elongation of up to 30.5 (2.6) mm during head-turned rear-impact significantly exceeded (P < 0.05) the physiological beginning at 5 g. Highest peak elongation of 5.8 (2.1) mm during head-forward rear impact did not exceed physiological limit. Head-turned rear impact caused earlier occurrence of average peak vertebral artery elongation, 84.5 (4.2) ms vs. 161.0 (43.8) ms, and higher average peak vertebral artery elongation rate, 1336.7 (74.5) mm/s vs. 211.5 (97.4) mm/s, as compared to head-forward rear impact.

INTERPRETATION

Elongation-induced vertebral artery injury is more likely to occur in those with rotated head posture at the time of rear impact, as compared to head-forward.

Cervical Artery Dissection. A Comparison of Highly Dynamic Mechanisms: Manipulation versus Motor Vehicle Collision

OBJECTIVE

To examine the similarities and dissimilarities between cervical chiropractic manipulative therapy and whiplash, and their respective relation to cervical artery dissection.

DATA SOURCES

A literature synthesis used MEDLINE-PubMed and MANTIS literature searches. A total list of 99 relevant articles was generated. Additional references were collected from citations incorporated within the included articles.

RESULTS

Both neck manipulation and motor vehicle collision events apply loads to the spinal column rapidly. While neck manipulation loads are slower to develop and displacements smaller, they may reach peak amplitudes on maximum effort comparable to those seen in low-velocity collision experiments. In contrast to reports that the vertebral artery experiences elongations exceeding its physiological range by up to 9.0 mm during simulated whiplash, strains incurred during cervical manipulative therapy have been reported to be approximately one ninth of those required for mechanical failure, comparable to forces encountered in the course of diagnostic range of motion examination. Additionally, long-lasting abnormalities of blood flow velocity within the vertebral artery have been reported in patients following common whiplash injuries, whereas no significant changes in vertebral artery peak flow velocity were observed following cervical chiropractic manipulative therapy.

CONCLUSIONS

Perceived causation of reported cases of cervical artery dissection is more frequently attributed to chiropractic manipulative therapy procedures than to motor vehicle collision related injuries, even though the comparative biomechanical evidence makes such causation unlikely. The direct evidence suggests that the healthy vertebral artery is not at risk from properly performed chiropractic manipulative procedures.

Causes of complications from cervical spine manipulation

Cervical manipulation occasionally causes serious vertebrobasilar complications. The usual cause is vertebral artery dissection, however in some cases there has been no obvious arterial injury. The present paper reviews the mechanisms by which complications occur, particularly when the applied force is trivial or there is no injury to the vertebral arteries, and the factors that increase risk of complications. In addition, implications are drawn for use of the recently revised Australian Physiotherapy Association (APA) guidelines. In the absence of vertebral artery rupture, complications are proposed to arise from vasospasm, haemostasis, endothelial injury or turbulent flow. These mechanisms have a sound scientific basis but have yet to be demonstrated as specifically causing vertebrobasilar complications. The most important risk factors for vertebrobasilar complications appear to be prior trauma to the vertebral arteries and symptoms of vertebrobasilar ischaemia from previous manipulation. There is weak evidence that hypoplasia of the vertebral arteries also increases the risk of complications. Neither general vascular factors nor pre-existing degenerative conditions of the cervical spine increase risk of vertebrobasilar complications. The procedures described in the APA guidelines test adequacy of total cerebral perfusion during cervical movements rather than patency of the vertebral arteries or their susceptibility to injury. The guidelines may therefore indicate potential for surviving a complication from manipulation. They may also identify patients at risk of complications from minor trauma. It is recommended that the procedures described in the APA guidelines be applied prior to every manipulation, and that manipulation be avoided in the presence of any signs of vertebrobasilar insufficiency.

Injury threshold: whiplash-associated disorders

OBJECTIVES

To review current knowledge and recent concepts of the causes of injuries after minor impact automobile collisions and to acquaint those who treat these types of injuries with possible injury thresholds and mechanisms that may contribute to symptoms.

DATA SOURCES

A review of literature involving mechanisms of injury, tissue tensile threshold, and neurologic considerations was undertaken. A hand-search of relevant engineering, medical/chiropractic, and computer Index Medicus sources in disciplines that cover the variety of symptoms was gathered.

RESULTS

Soft-tissue injuries are difficult to diagnose or quantify. There is not one specific injury mechanism or threshold of injury. With physical variations of tissue tensile strength, anatomic differences, and neurophysiologic considerations, such threshold designation is not possible.

CONCLUSIONS

To make a competent assessment of injury, it is important to evaluate each patient individually. The same collision may cause injury to some individuals and leave others unaffected. With the variability of human postures, tensile strength of the ligaments between individuals, body positions in the vehicle, collagen fibers in the same specimen segment, the amount of muscle activation and inhibition of muscles, the size of the spinal canals, and the excitability of the nervous system, one specific threshold is not possible. How individuals react to a stimulus varies widely, and it is evident peripheral stimulation has effects on the central nervous system. It is also clear that the somatosensory system of the neck, in addition to signaling nociception, may influence the control of neck, eyes, limbs, respiratory muscles, and some preganglionic sympathetic nerves.

The devastating potential of blunt vertebral arterial injuries

OBJECTIVE

To formulate management guidelines for blunt vertebral arterial injury (BVI).

SUMMARY BACKGROUND DATA

Compared with carotid arterial injuries, BVIs have been considered innocuous. Although screening for BVI has been advocated, particularly in patients with cervical spine injuries, the appropriate therapy of lesions is controversial.

METHODS

In 1996 an aggressive arteriographic screening protocol for blunt cerebrovascular injuries was initiated. A prospective database of all screened patients has been maintained. Analysis of injury mechanisms and patterns, BVI grades, treatment, and outcomes was performed.

RESULTS

Thirty-eight patients (0.53% of blunt trauma admissions) were diagnosed with 47 BVIs during a 3.5-year period. Motor vehicle crash was the most common mechanism, and associated injuries were common. Cervical spine injuries were present in 71% of patients, but there was no predilection for cervical vertebral level or fracture pattern. The incidence of posterior circulation stroke was 24%, and the BVI-attributable death rate was 8%. Stroke incidence and neurologic outcome were independent of BVI injury grade. In patients treated with systemic heparin, fewer overall had a poor neurologic outcome, and fewer had a poor outcome after stroke. Trends associated with heparin therapy included fewer injuries progressing to a higher injury grade, fewer patients in whom stroke developed, and fewer patients deteriorating neurologically from diagnosis to discharge.

CONCLUSIONS

Blunt vertebral arterial injuries are more common than previously reported. Screening patients based on injury mechanisms and patterns will diagnose asymptomatic injuries, allowing the institution of therapy before stroke. Systemic anticoagulation appears to be effective therapy: it is associated with improved neurologic outcome in patients with and without stroke, and it appears to prevent progression to a higher injury grade, stroke, and deterioration in neurologic status.

Cervical vertigo after hair shampoo treatment at a hairdressing salon: a case report

STUDY DESIGN

A case report of cervical vertigo that occurred after shampoo treatment in a hairdressing salon. Abnormalities were detected on magnetic resonance images and magnetic resonance angiography scans.

OBJECTIVES

To describe the diagnosis of cervical vertigo caused by neck hyperextension.

SUMMARY OF BACKGROUND DATA

Neck hyperextension may induce vertigo and dizziness; the pathophysiology remains unclear, however, because subjective findings are usually difficult to document.

METHODS

The diagnosis, treatment, and outcome of a patient with cervical vertigo that occurred after hair shampoo treatment in a hair dressing salon were assessed.

RESULTS

Magnetic resonance angiography demonstrated narrowing of the left vertebral artery, whereas magnetic resonance imaging showed cerebellar infarction. Treatment included rest and drugs that activate cerebral circulation and prevent platelet aggregation. Improvement was noted within few days.

CONCLUSIONS

The authors suggest that the hyperextended neck position during hair shampoo treatment in a beauty parlor may be a risk factor for back lifting or cerebellum vascular insufficiency. Public education should lead to avoidance of this position during hair shampoo treatment at hair dressing salons.

Mechanism of whiplash injury

OBJECTIVE: To propose a different hypothesis of whiplash injury mechanism based on a series of experimental studies summarized in this communication. DESIGN: A series of biomechanical studies simulating whiplash trauma using isolated human cadaveric spine specimens. BACKGROUND: Whiplash injuries are on the rise as reported in several recent studies, due primarily to the increased traffic density. Although the symptoms associated with whiplash have been described, our understanding of the injury mechanism remains poor. The prevailing view of neck hyper-extension causing the injury has not been supported by recent experimental studies. METHODS: Eight fresh human cadaveric cervical spine specimens were prepared and traumatized to varying degrees under controlled conditions using a bench-top model of whiplash trauma. Before and after each trauma, the specimen was studied by functional radiography and flexibility test to document changes in the anatomic alignment and biomechanical properties at each level indicating injuries sustained. At the end of all testing, CT-scans, MRI and cryomicrotome images were obtained. During each trauma, relative motions of all intervertebral joints were recorded with a high speed movie camera. Elongations of the vertebral artery and several capsular ligaments were also monitored during the trauma using specially designed transducers. RESULTS: The hyper-extension hypothesis of injury mechanism was not supported by these studies. We found a distinct bi-phasic kinematic response of the cervical spine to whiplash trauma. In the first phase, the spine formed an S-shaped curve with flexion at the upper levels and hyper-extension at the lower levels. In the second phase, all levels of the cervical spine were extended, and the head reached its maximum extension. The occurrence of anterior injuries in the lower levels in the first phase was confirmed by functional radiography, flexibility tests and imaging modalities. The largest dynamic elongation of the capsular ligaments was observed at C6-C7 level during the initial S-shaped phase of whiplash. Similarly, the maximum elongation of the vertebral artery occurred during the S-shape phase of whiplash. CONCLUSION: We propose, based upon our experimental findings, that the lower cervical spine is injured in hyperextension when the spine forms an S-shaped curve. Further, this occurs in the first whiplash phase before the neck is fully extended. At higher trauma accelerations, there is a tendency for the injuries to occur at the upper levels of the cervical spine. Our findings provide truer understanding of whiplash trauma and may help in improving the diagnosis, treatment, and prevention of these injuries.

Simulation of whiplash trauma using whole cervical spine specimens

STUDY DESIGN

Whiplash injuries were studied in an experiment using whole cervical spine specimen.

OBJECTIVES

To develop a whiplash trauma model that uses a whole cervical spine specimen, and to show the feasibility and unique features of such a model.

SUMMARY OF BACKGROUND DATA

Whiplash trauma has been simulated in biomechanical experiments using volunteers, whole body cadavers, animals, anthropometric dummies, and mathematic models. These experiments require large facilities, are expensive, and provide limited information about cervical spine injuries.

METHODS

An alternate approach, in which a bench-top sled accelerating apparatus is used to produce whiplash trauma, has been developed to study such trauma in whole cervical spine specimens. Several transducers were developed to monitor soft tissue injuries during the trauma. The model also provides quantification of injuries to the cervical spine.

RESULTS

To assess the feasibility and usefulness of the model, a specimen was traumatized, and the following parameters were monitored during the trauma: linear acceleration of the sled, linear and angular acceleration of the head surrogate, displacements of the head surrogate, loads at T1 and C1 vertebrae, and linear deformations of capsular ligaments and vertebral artery.

CONCLUSIONS

This model, which incorporates a fresh cadaveric whole human cervical spine specimen, can simulate whiplash trauma effectively and is useful in providing a comprehensive set of clinically relevant information during the trauma. This model gives insight into the complex events and interactions that cause the injuries that occur during whiplash trauma.