The Biomechanics Behind Whiplash Associated Disorder: Difference between revisions

No edit summary
mNo edit summary
Line 23: Line 23:
'''Pathophysiology'''  
'''Pathophysiology'''  


The mechanism of injury in whiplash associated disorder occurs in 3 stages. In the first stage, both the upper and lower spine experience flexion, causing a loss of cervical lordosis. <ref name=":3">Gastown Physio Pilates. Whiplash Associated Disorder. Available from: <nowiki>https://gastownphysiopilates.com/blogs/3-whiplash</nowiki> (Accessed 28 March 2021)</ref> In stage two, extension of the lower vertebrae leads to extension in the upper vertebrae which causes the cervical spine to adopt an S-shaped curve. <ref name=":4">Chen HB, Yang KH, Wang ZG. Biomechanics of whiplash injury. 2009;5:305-14.</ref> Finally, in stage three extension moments acting on both ends cause the entire neck region to be extended with an intense shearing force causing compression of facet joint capsules. <ref name=":3" /><ref name=":4" />  
The mechanism of injury in whiplash associated disorder occurs in 3 stages. In the first stage, both the upper and lower spine experience flexion, causing a loss of cervical lordosis. <ref name=":3">Gastown Physio Pilates. Whiplash Associated Disorder. Available from: <nowiki>https://gastownphysiopilates.com/blogs/3-whiplash</nowiki> (Accessed 28 March 2021)</ref> In stage two, extension of the lower vertebrae leads to extension in the upper vertebrae which causes the cervical spine to adopt an S-shaped curve. <ref name=":4">Chen HB, Yang KH, Wang ZG. Biomechanics of whiplash injury. 2009;5:305-14.</ref> Finally, in stage three the neck is completely extended with a shearing force causing compression of facet joint capsules. <ref name=":3" /><ref name=":4" />  
----
----


Revision as of 18:13, 6 May 2021

Welcome to The University of Waterloo Clinical Biomechanics Project. This space was created by and for the students at The University of Waterloo in Ontario, Canada. Please do not edit unless you are involved in this project, but please come back in the near future to check out new information!!

Original Editors - Add your name/s here if you are the original editor/s of this page. User Name

Top Contributors - Rucha Gadgil, Natasha Ivanochko, Camila Trujillo, Kim Jackson, Simisola Ajeyalemi and Habibu Salisu Badamasi  

What is it?

Whiplash Associated Disorder (WAD) is a term that is used to describe injuries in and around the neck obtained from deceleration-acceleration movements that occur abruptly, such as from a motor vehicle collision[1]. The prognosis of WAD tends to be unknown and unpredictable, there can be two types of cases, acute or chronic. [2] Acute cases normally have a full recovery whereas chronic cases lead to long term pain as well as future disability. [2]  Most whiplash associated disorders are minor soft tissue injuries lacking evidence for fractures.[3]

Quebec Classification

The Quebec Task Force produced a mechanism used to classify patients suffering from whiplash associated disorder, based on the severity of both signs and symptoms.[4] There are different grades ranging from I to IV, these are described below.

·     Grade I: Patient experiences neck pain, stiffness or tenderness.

·     Grade II: Patient exhibits musculoskeletal signs which include decreased range of motion and point tenderness.

·     Grade III: Patient shows neurologic signs which may include sensory deficits as well as muscle weakness.

·     Grade IV: Patient shows neck dislocation or fracture. [1] [4]

Pathophysiology

The mechanism of injury in whiplash associated disorder occurs in 3 stages. In the first stage, both the upper and lower spine experience flexion, causing a loss of cervical lordosis. [5] In stage two, extension of the lower vertebrae leads to extension in the upper vertebrae which causes the cervical spine to adopt an S-shaped curve. [6] Finally, in stage three the neck is completely extended with a shearing force causing compression of facet joint capsules. [5][6]

Kinematics During Rear Impact

We must be able to understand the biomechanics during rear impact to be able to assess the severity of injury it can cause. From the perspective of the driver the impact vehicle is rapidly accelerated forward causing the seat to interact with them, this occurs in the seatback causing the thorax to drive anteriorly. [7] As the thorax is accelerated forward the inertia of the body deforms the seatback which deflects it towards the rear of the car. In time the seatback overcomes inertial loads from the torso and rebounds forward. [7] This drives the person’s body forward and into the seatbelt. This causes the head-neck complex to sustain inertial loading during the initial stages of the impact.[8] The specific loading that occurs will have a structural response on the cervical spine, but this would be dependent on the input acceleration applied at the cervicothoracic junction as well as the interaction of the head and its spinal components.[7])[8]

Clinical Evidence

Kinematics and kinetics have been studied using crash dummies, human cadavers, human volunteers, and computer models. Collectively these studies have shown that during rear-end collisions the cervical spine initially undergoes a horizontal shear or retraction. [9]The studies showed different tissues and joints that could be damaged/injured during impact.

  • Anterior Longitudinal Ligaments and Discs

Starting with anterior longitudinal ligaments, the studies identified tears as well as rim lesions of the anterior anulus fibrosus that were produced in cadavers subjected to whiplash injuries [9]. Strains in the anulus fibrosus of lower cervical discs can exceed physiologic limits. These observations provide a basis for tears of the anterior disc or the anterior longitudinal ligament being a source of nociception after whiplash injury.[9] 

  • Dorsal Root Ganglion

The dorsal ganglia can become damaged from a whiplash injury. They are at risk for injury because of the rapid changes that occur in the canal pressure, which are caused due to the rapid head motions from the impact.[9] This knowledge offers potential mechanism of how neck and shoulder pain may result from nerve root trauma caused due to whiplash. 

  • Vertebral Artery

A retrospective analysis of 500 whiplash patients indicated that the incidence of cervical arterial dissections was significantly higher than in controls. Vertebral artery injury originates from an intimal tear, most commonly at cervical spine 1 and 2, which is the primary site of cervical axial rotation.[9][10] Coupled cervical spine extension and axial rotation beyond the physiologic limit has been hypothesized to cause vertebral artery injury.[10] It is supported by biomechanical research, indicating elongation-induced vertebral artery injury may occur due to non-physiologic coupled neck motions during an automobile collision. [9]

  •  Muscles

Direct injury to muscles can occur from the imposed lengthening during reflex neck muscle activation which is the response caused from the impact.[11]Biomechanically, muscle fascicle strains in the sternocleidomastoid muscle and in the semispinalis capitis muscle were seen in human subjects[12] The strains were larger than those shown in the injury data showing that lesions to the muscles following a whiplash exposure are due to the acute rather than chronic phase of whiplash injury.[11]

Concluding statement

Biomechanics are important in both assessing and understanding treatment procedures that can be done. By appreciating the biomechanics behind whiplash associated disorder we can analyze better treatments as well as improve techniques that are more specific to how injuries are caused. By looking at the biomechanics we can interpret the lesions caused on the different structures around the neck and prepare better plans as well as researching further on how to prevent such lesions. 

References

  1. ↑ 1.0 1.1 1.      Pastakia K, Kumar S. Acute whiplash associated disorders (WAD). Open Access Emergency Med. 2011; 3:29-32. 
  2. ↑ 2.0 2.1 Stace R. and Gwilym S. Whiplash associated disorder: a review of current pain concepts. Bone & Joint. 2015; 4:360
  3. ↑ Bragg KJ, Varacallo M. Cervical Sprain. Available from: https://www.ncbi.nlm.nih.gov/books/NBK541016/ (Accessed 10 April 2021)
  4. ↑ 4.0 4.1 Steven J. MD, Richard A. Patrick, D.L. Convery, K. Keller R.B. Singer, D.E. * The Quebec Task Force Classification for Spinal Disorders and the Severity, Treatment, and Outcomes of Sciatica and Lumbar Spinal Stenosis, Spine.1996;21:2885-2892
  5. ↑ 5.0 5.1 Gastown Physio Pilates. Whiplash Associated Disorder. Available from: https://gastownphysiopilates.com/blogs/3-whiplash (Accessed 28 March 2021)
  6. ↑ 6.0 6.1 Chen HB, Yang KH, Wang ZG. Biomechanics of whiplash injury. 2009;5:305-14.
  7. ↑ 7.0 7.1 7.2 Stemper BD, Corner BD. Whiplash-Associated Disorders: Occupant Kinematics and Neck Morphology. Journal of Orthopaedic & Sports Physical Therapy.2016;46:834-844
  8. ↑ 8.0 8.1 De Pauw R, Coppieters I, Kregel J, De Meulemeester K, Danneels L, Cagnie B. Does muscle morphology change in chronic neck pain patients? - A systematic review. 2016 Apr;22:42-9.
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 Curatolo M, Bogduk N, Ivancic PC, McLean SA, Siegmund GP, Winkelstein BA. The role of tissue damage in whiplash-associated disorders: discussion paper 1. Spine. 2011;36:309-15
  10. ↑ 10.0 10.1 Hauser V, Zangger P, Winter Y, et al. Late sequelae of whiplash injury with dissection of cervical arteries. Eur Neurol. 2010;64:214–218
  11. ↑ 11.0 11.1 Chung YS, Han DH. Vertebrobasilar dissection: a possible role of whiplash injury in its pathogenesis. Neurol Res. 2002;24:129–138
  12. ↑ Chen H, King HY, Wang Z. Biomechanics of whiplash injury. Chinese Journal of Traumatology. 2009;12:305-314
Retrieved from "https://www.physio-pedia.com/index.php?title=The_Biomechanics_Behind_Whiplash_Associated_Disorder&oldid=272311"