Documentation:FIB book/Sports-Related Injuries of the Thoracic Spine

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Importance of Thoracic Spinal Injuries

Unlike cervical spinal injuries which are commonly seen in sports, thoracic spinal injuries are a much rarer occurrence. Of all spinal injuries, 15% are due to sports;[1] however, between various sports there is a large discrepancy between what regions of the spine are most commonly injured. Thoracic spinal cord injuries are most prevalent in horseback riding and snowboarding, where they make up 26% and 28% of all spinal cord injuries for those sports respectively. In contrast, thoracic spinal cord injury only makes up 2% of diving and American football spinal cord injuries.[2] Nevertheless, these are still serious injuries which can result in paralysis and even death depending on the severity. Furthermore, due to the low frequency of thoracic spinal injury, thoracic spinal injuries are often neglected and overlooked, and can be especially difficult to treat.[1]

Spinal Fractures

The most common type of fracture experienced by the thoracic spine is a compression fracture, representing 52% of all fractures of the thoracic spine. Compression fractures of the thoracic spine are caused by high-energy axial loading,[3] with anterior wedge compression fractures combining axial loading with flexion.[1] Sports such as rugby, American football, and skiing provide opportunities for this to occur.[1][4] They are generally stable and are unlikely to cause neurological deficits. This stability is the result of the support of the ribcage.[1] Of similar severity are transverse process fractures, representing 37% of all thoracic spinal fractures.[1] They are the result of a variety of mechanisms which can result in such fractures, ranging from blunt trauma to violent lateral flexion-extension.[5] Also of low severity are fractures of the spinous processes. Such fractures can occur in two varieties: the Clay-shoveler’s fracture which is an isolated fracture of the spinous process of vertebrae C6-T3, and multilevel spinous process fractures occurring in any region.[6] The former is caused by a rapid hyperextension of the neck,[7] while the latter is often the result of a complex combination of hyperflexion or hyperextension with direct trauma.[6] The former has been observed in swimming,[8] and the latter in golf.[1] Characteristics of these three types of fractures are the preservation of the surroundings of the vertebral foramen, preventing any damage to the spinal cord. Thus, although pain and spinal instability may supervene, these injuries are often of minor concern, rarely requiring surgery.[1]

The more serious types of spinal fractures concern the narrowing of the vertebral foramen, and are of two main types: vertebral burst fractures and lamina fractures. Vertebral burst fractures occur in a variety of manners, depending on the orientation and curvature of the spine during the impact; however, they are always the result of high-energy loading.[1] They generally cause instability of the spine, and are particularly serious when there is retropulsion of the vertebral body into the vertebral foramen. Burst fractures often occur in the same high-impact sports which give rise to compression fractures, and have also been seen in situations of rapid hyperflexion in rodeo athletes.[9] Much less studied are lamina fractures, which are a common result of thoracolumbar trauma.[10] They can occur on their own, or can accompany burst fractures. Unlike other fractures of the spine, lamina fractures exhibit a great variety of forms: they can be unilateral or bilateral, and complete or greenstick (i.e. incomplete).[11] In addition, they can occur horizontally or vertically: the former from flexion-distraction, and the latter from either excess axial load when it accompanies a burst fracture or from a posterior impact such as falling on one’s back when only a lamina fracture occurs.[10][12][13] Lamina fractures have been seen in falls onto the back from horse racing.[13] Burst and lamina fractures can both result in retropulsion into the spinal cord; however, due to the larger size of the vertebral foramen of the lower thoracic spine, retropulsion does not necessarily lead to spinal cord injury. Nevertheless, lamina fractures can result in dural tears which can have neurological consequences and allow cerebrospinal fluid to leak, leading to the development of fistulae and abscesses.[14] These more serious spinal fractures will almost certainly require decompression and stabilisation surgery.[11]

Intervertebral Disc Herniation

The intervertebral discs are highly robust, but when they are subject to axial loading alongside rotation in a flexed spine, they are prone to herniating: that is the protrusion of the nucleus through a defect in the fibrous annulus of the intervertebral disc.[1] These defects are often the result of long-term degradation from repetitive motions. Disc herniation has resulted from falls during skiing,[15] from blocking and tackling during American football,[1] and from pitching during baseball.[16] While thoracic disc herniations only account for 2% of the total disc herniations experienced in the National Football League, they resulted in the longest hiatuses from the game.[1] Disc herniations can press on the spinal cord in some instances, and may cause neurological symptoms. In particular, thoracic disc herniations can result in chest pain as felt during a rib fracture, both being linked to the intercostal nerves.[16] Depending on the severity and direction of the herniation, surgery may or may not be required; most cases often being resolved through relaxation and the use of NSAIDs.[1]

Musculoligamentous Injuries

Thoracic musculoligamentous injuries are prevalent in situations where high-energy or high-repetition mechanisms are taking place. Whether it be acute or chronic, these injuries result from the rotational or bending forces the user is creating during their every-day routine. Similar to whiplash in the cervical spine, thoracic musculoligamentous injuries often occur when an athlete conducts a violent throwing action or undergoes a swinging action too quickly.[17] The damage is more frequently found on the contralateral side of the primary throwing/swinging arm,[18] and neurologic impairment is not normally present. There are, however, situations where neurologic symptoms may occur; this should not be taken lightly, and a more extensive evaluation should be conducted.

Athletes that participate in high-repetition sports such as rowing and golf tend to develop chronic overuse injuries, which lead to an increased prevalence of debilitating symptoms. Competitive rowers, for example, experience increased back and ribcage injury at 22% and 9% respectively.[19] These rib injuries often present as stress fractures, with posterior ribs being the most prevalent target due to forces applied by the serratus anterior. This is more likely to occur after an off-season, when athletes attempt to resume their normal training regime with lower endurance. Stress fractures are not limited to the ribs; these injuries also commonly involve the thoracic spine (specifically in the T4-T7 region) where the latissimus dorsi, rhomboids, and erector spinae exert their localized forces.[18]

Spinal Cord Injuries

Spinal cord injury (SCI) involves the disruption of sensory, motor, or autonomic functions; this kind of traumatic event can have long-lasting effects on a patient’s well-being. Overall incidence of SCI depends on a plethora of factors such as age, sex, race, and whether the data came from a developed or undeveloped nation. Looking at global results, literature suggests there are about 30-40 cases per million on average. The United States presented with the highest incidence at 906 per million, with the lowest incidence being Spain at 8 per million.[20] Using data from the United States, a few demographics stand out with regards to increased incidence of SCI. In 2019 about 78% of these SCI cases were from males, 59.5% of them belonging to the “non-Hispanic white” race group. These same studies suggest that single people have a higher incidence of injury at 44.9%, which is 7.6% higher than married people.[21] Disregarding country of origin, most studies presented a high male-to-female ratio and peak incidence age less than 30 years old.[20][21]

It should not be surprising that the United States has the highest incidence of SCI. The infrastructure is dense with a high volume of traffic, the incidence of violent acts is much higher than other countries, and their culture focuses on sports such as American football. Despite popular belief, diving has a higher incidence of SCI than American football.[22] While sports make up a small fraction of SCI cases at about 7-8%, car crashes and violence make up a much larger percentage at 40.4% and 15% respectively.[23] Even falls account for more accidents each year at roughly 28%.[21] Looking at sports, violence, and car accidents there are recurring demographics. Young white males are often put in these situations, whether it be collegiate football, automobile racing, or gang activity. This explains why previous research has yielded a high male-to-female ratio, and also why the peak incidence age is less than 30 years old. American football professionals often “age-out” before 30, and the incidence of car crashes in teenagers and young adults is higher than more experienced individuals.[24][25]

When dealing with SCI the terms “complete” and “incomplete” lesions are utilized to describe the severity of the injury. An incomplete SCI indicates partial loss of function, whereas a complete SCI indicates full loss of function. Evaluating research led to the discovery of an upward trend in neurologically incomplete lesions, currently accounting for 53% of all SCI.[26] This is most likely due to the increasing quality of on-site emergency services. Thoracic-level SCI account for roughly 35.6% of all SCI according to a national SCI database.[26] These such SCI impact the function of the upper chest, mid back, and abdominal region. Loss of function depends on which vertebrae is injured: ranging from T1 to T12. The first couple vertebrae (T1-T5) have a greater effect on the upper body; hand and arm coordination are typically unaffected unless T1 is severely injured. The lower half (T6-T12) typically lead to abdominal and back muscle impairment.[27] When any of the thoracic vertebrae become damaged, paraplegia is often incurred. This indicates either complete or incomplete loss of control in the trunk and legs.

Injury patterns can be determined through a detailed evaluation of existing cases. These patterns typically manifest as compression fractures, dislocations, burst fractures, and distraction injuries.[28] The most common injury patterns in SCI are dislocation and burst fractures, having a 45-58% and 9-35% incidence respectively.[29] Velocity of impact is also a key factor, having been validated in various animal models. While it is currently ethically impossible to conduct clinical studies on this subject, the results are plain enough to see that a faster impact will have more energy and thus do more damage.[30] Residual compression is often observed after the initial SCI occurs, specifically with burst fractures and dislocations. Many papers have been published on the importance of spinal decompression in neurological outcome.[31][32][33] These studies are not, however, in complete agreement about the results of such treatment. This is often justified based on the “heterogeneity of human injuries” leading to an inability to replicate specific injury biomechanics.[33]

Biomechanical Models of the Thoracic Spine

Figure 1: Photo of cadaveric ribcage in testing rig[34]

There have been many attempts to develop a biomechanical model which can accurately capture the motions of the thoracic spine using computational models and cadavers;[34] however, a great deal of these efforts have ignored the effect of the ribcage on the thoracic spine’s stability.[35][36][37] Yet, it has been estimated that the ribcage accounts for 30-40% of the thoracic spine’s stability.[34] Thus, it is important to consider both the ribcage and the thoracic spine as one whole functional unit when assessing the biomechanics. The most comprehensive cadaveric and computational will be discussed below.

Cadaveric models have been important for establishing the biomechanical tolerances of the thoracic spine. To investigate the thoracic spine’s range of motion and stiffness, Mannen et al. used a complete cadaveric thoracic spine and ribcage, excluding the floating ribs of T11 and T12 (Figure 1).[34] Seven cadavers with a mean age of 71 years were prepared with all the musculature removed and T1 and T12 mounted in autobody filler. T12 was rigidly mounted, while the mounting of T1 was free to move and would be responsible for applying the loads. The motion of the vertebrae was tracked by inserting Optotrak markers into the posterior aspects of the vertebrae, allowing the vertebrae to be tracked in 3D space, and capturing the flexion, extension, and rotation. The results of the testing are summarised in Table 1. Neutral represents no load being applied, while elastic represents a 5Nm pure moment being applied to T1.

Table 1: Range of Motion and Stiffness of Cadaveric Thoracic Spine [34]
Flexion Extension Lateral Bending Axial Rotation
Neutral ROM (deg) - - 4.5 3.0
Elastic ROM (deg) 6.6 8.4 9.4 11.6
Neutral Stiffness (Nm/deg) 0.40 0.44 0.23 0.26
Elastic Stiffness (Nm/deg) 2.12 1.22 1.48 1.47

Due to the limited volume and significance of existing cadaveric data, not many computational models exist for the complete thoracic spine. The original 3D computational model was developed in 1974 by researchers at the University of Illinois (Figure 2).[38] The thorax is a very computationally heavy part of the body being that, unlike the cervical spine, the rib cage is also involved for biofidelic calculations. For a model of this quality to appear at a time when computers were quite basic, the researchers were certainly ahead of their time. Even anatomical features such as the sagittal plane curves of the vertebral column, and the complicated shape of any given vertebra were incorporated into the model.

Figure 2: Visualisation of the original model [38]

The model these researchers developed divided each vertebra into what is called an “element”. These elements covered the thoracolumbar spine, the sacrum, rib pairs 1-10, and the sternum. Unlike modern computational models that look specifically at the thoracolumbar junction, this model contained each of the 17 thoracolumbar vertebrae from T1 to L5. These elements were modelled as rigid bodies, meaning that deformation was not considered. While this is a major limitation, and one that should be improved on in the future, it is acceptable to make this assumption if your sole aim is to examine how different forces build up between the vertebrae and the rib cage.

The analysis works based on a series of coordinate systems: each vertebra and rib having its own local coordinate system, and a global coordinate system existing to connect everything together. Through giving each element a local coordinate system, the location and orientation can be related to a global coordinate system in which every element is situated. The computational procedure makes use of forces and displacements through mathematical relationships. The rigid nature of each element combined with the deformable connections allows for the model to be relatively biofidelic.

Drawbacks of Current Biomechanical Models

Cadaveric tests on the thoracic spine have largely been limited to range of motion and stiffness analysis. Tolerance testing is largely absent likely due to the difficulty in creating a biofidelic test setup, and the limited use of the resulting data. Whereas the cervical and lumbar regions of the spine have the head and pelvis respectively, providing a somewhat stationary anchor point, the thoracic spine is located between two flexible regions, and thus it is challenging to isolate the motions of the thoracic spine without putting unrealistic constraints on T1 and T12.

Nevertheless, range of motion and stiffness tests also have major limitations. Cadaveric joints and ligaments do not always behave biofidelically, and often their degree of preservation is heavily dependent on the method chosen for freezing.[39] This would affect the motion of the spinal ligaments, intervertebral discs, facet joints, and the articulation of the ribcage. All of these factors could interfere with the range of motion, and more likely the stiffness values obtained by Mannen et al. biofidelically.

The range of motion and stiffness values are also of limited use due to the negation of the effects of musculature. The musculature of the thoracic spine is complex, and that of the ribcage more so, to the degree that the cadaveric tests cannot be considered to represent the stiffness or range of motion of an actual human spine. Nevertheless, these tests can be used to validate the range of motion and stiffness of computational models of the thoracic spine prior to the addition of musculature. In addition, intra-abdominal pressure was not factored into Mannen et al.’s tests. They postulated, however, that both musculature and intra-abdominal pressure would likely lead to increased stability of the thoracic spine.[34]

Computational models involving the thoracic spine are also currently extremely limited, primarily due to the lack of knowledge surrounding its mechanical interactions with the rib cage. Current models often require users to input biomechanical data, which means that this lack of knowledge prevents us from biofidelically representing thoracic interactions. In general, there is a huge lack of research on the full thoracic spine. The thoracolumbar junction is often analysed, but that only includes the last couple thoracic vertebrae and the beginning of the lumbar vertebrae.[40] Finite element modelling is often created utilizing cadaveric data, which is partially why such models do not already exist. Where there are no cadaveric data, there are no computational models.

Future Work

Future efforts in cadaveric testing should work alongside animal testing in order to develop a biofidelic computational model of the thoracic spine. While cadaveric testing can closely approximate the motions of the spine without any musculature, in vivo animal testing is only able to roughly approximate the motions of the spine with musculature. What is missing is the use of cadaveric pig spines and human volunteers to try and bridge these gaps. By comparing human cadaveric results with those of pigs, one can gain a better understanding of the differences between the mechanical responses of the spine and humans. One can then use this to better translate data acquired from in vivo porcine tests into approximate in vivo human data. Non-injurious tests of pigs and human volunteers can also be performed to further validate this translation. Already research into the differences between pig and human thoracic spines has been conducted, albeit for different reasons.[41]

As future cadaveric research is conducted, with new models and data regarding how the thoracic spine interacts with the rib cage, computational models will naturally begin to develop. Finite element modelling is very important for the validation of cadaveric models; thus, it makes sense that they will develop together going forward. These models should aim to include the entire thoracic spine, not just a section, as well as the entire rib cage. Musculature should be looked at as an addition, observing whether the results are significantly affected. Despite this, there should still be models without musculature, as it is more important to solidify the vertebral interactions without external bodily forces being added. Being able to stress test such a complete model would yield very important results regarding the diagnosis and prevention of SCI.[42]

While animal research for spinal cord injury has been conducted,[43] no animal models investigating the in vivo biomechanical responses of the thoracic spine appear to have been developed. In the future, however, tests similar to those performed by Mannen et al. should be performed on anaesthetised pigs in order to evaluate the differences. While the thoracic vertebrae cannot be fixed, they could be manipulated externally using rods like those seen in an Ilizarov apparatus.

In addition, impact tests trying to replicate various mechanisms of injury could be conducted on anaesthetised pigs. This could be used in conjunction with high-speed x-rays to evaluate damage to the spinal cord during the impact. These tests could also be combined with testing on human volunteers at non-injurious levels. By simulating the positions commonly seen during impact in sports, such as falling off onto one’s back, and covering the volunteer’s thorax with EMG electrodes, one could determine which muscles are generally being contracted and by what amount they are being contracted prior to impact. This could then be applied to porcine tests by using electrodes to stimulate those same groups of muscles prior to impact to better replicate the muscular response in humans.

References

  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 Menzer H, Gill GK, Paterson A. Thoracic Spine Sports-Related Injuries. Current Sports Medicine Reports. 2015 Jan;14(1):34–40.
  2. ↑ Chan CW, Eng JJ, Tator CH, Krassioukov A. Epidemiology of sport-related spinal cord  injuries: A systematic review. The Journal of Spinal Cord Medicine. 2016 Feb 18;39(3):255– 64.
  3. ↑ Donnally III CJ, DiPompeo CM, Varacallo M. Vertebral Compression Fractures [Internet]. PubMed. Treasure Island (FL): StatPearls Publishing; 2020. Available from: https://www.ncbi.nlm.nih.gov/books/NBK448171/
  4. ↑ Elattrache N, Fadale PD, Fu FH. Thoracic spine fracture in a football player. A case report. The American Journal of Sports Medicine [Internet]. 1993 Jan 1 [cited 2021 Nov 11];21(1):157–60. Available from: https://pubmed.ncbi.nlm.nih.gov/8427361/
  5. ↑ Newell N, Pearce AP, Spurrier E, Gibb I, Webster CE, Clasper JC, et al. Analysis of  isolated transverse process fractures sustained during blast-related events. Journal of Trauma  and Acute Care Surgery. 2018 Jul;85(1S):S129–33.
  6. ↑ 6.0 6.1 Kirsch JM, Nathani A, Patel RD. Multiple Adjacent Isolated Thoracic Spinous Process  Fractures in High-Energy Trauma. Case Reports in Orthopedics [Internet]. 2015 Jun 17 [cited  2021 Nov 11];2015:e921526. Available from: https://www.hindawi.com/journals/crior/2015/921526/
  7. ↑ Posthuma de Boer J, van Wulfften Palthe AFY, Stadhouder A, Bloemers FW. The Clay Shoveler’s Fracture: A Case Report and Review of the Literature. The Journal of Emergency Medicine [Internet]. 2016 Sep 1 [cited 2021 Nov 11];51(3):292–7. Available from: https://pubmed.ncbi.nlm.nih.gov/27262733/
  8. ↑ Everhart K. Clay Shoveler’s Fracture in High School Pole Vaulter. Journal of Sports  Medicine and Allied Health Sciences: Official Journal of the Ohio Athletic Trainers’  Association. 2020 Jun;6(1).
  9. ↑ Boham M, O’Connell K. Unusual Mechanism of Injury Resulting in a Thoracic Chance Fracture in a Rodeo Athlete: A Case Report. Journal of Athletic Training. 2014 Mar;49(2):274–9.
  10. ↑ 10.0 10.1 Aly MM, Al-Shoaibi AM, Al Fattani A, AlJuzair AH. Diagnostic Value of Various  Morphological Features of Horizontal and Vertical Laminar Fractures for Posterior  Ligamentous Complex Injury of the Thoracolumbar Spine as Defined by Magnetic  Resonance Imaging. World Neurosurgery [Internet]. 2021 Sep 1 [cited 2021 Nov 11];153:e290–9. Available from: https://pubmed.ncbi.nlm.nih.gov/34245884/
  11. ↑ 11.0 11.1 Chen Z, Wu J, Yao X-T, Cai T-Y, Zeng W-R, Lin B. Comparison of Wiltse’s paraspinal approach and open book laminectomy for thoracolumbar burst fractures with greenstick lamina fractures: a randomized controlled trial. Journal of Orthopaedic Surgery and Research [Internet]. 2018 Mar 2 [cited 2021 Nov 11];13(1):43. Available from: https://pubmed.ncbi.nlm.nih.gov/29499742/
  12. ↑ M’Donnell R. On the Operation of Trephining in Cases of Fracture of the Spine. Dublin  Quarterly Journal of Medical Science. 1866 Aug;42(1):1–35. 
  13. ↑ 13.0 13.1 Ivancic PC. Mechanisms of mid-thoracic spine fracture/dislocation due to falls during horse racing: A report of two cases. Chinese Journal of Traumatology. 2021 Jul;
  14. ↑ Kalevski SK, Peev NA, Haritonov DG. Incidental Dural Tears in lumbar decompressive  surgery: Incidence, causes, treatment, results. Asian Journal of Neurosurgery [Internet]. 2010  [cited 2021 Jun 24];5(1):54–9. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3198662/
  15. ↑ Brown CW, Deffer PAJ, Akmakjian J, Donaldson DH, Brugman JL. The Natural History of Thoracic Disc Herniation. Spine [Internet]. 1992 Jun 1 [cited 2021 Nov 11];17(6):S97. Available from: https://journals.lww.com/spinejournal/Abstract/1992/06001/The_Natural_History_of_Thorac ic_Disc_Herniation.6.aspx
  16. ↑ 16.0 16.1 Kato K, Yabuki S, Otani K, Nikaido T, Otoshi K, Watanabe K, et al. Unusual chest wall  pain caused by thoracic disc herniation in a professional baseball pitcher. Fukushima Journal  of Medical Science [Internet]. 2016 [cited 2021 Nov 11];62(2016). Available from:  https://www.jstage.jst.go.jp/article/fms/advpub/0/advpub_2015-25/_article/-char/ja/
  17. ↑ Donatelli R, Dimond D, Holland M. Sport-Specific Biomechanics of Spinal Injuries in the Athlete (Throwing Athletes, Rotational Sports, and Contact-Collision Sports). Clinics in Sports Medicine. 2012 Jul;31(3):381–96.
  18. ↑ 18.0 18.1 Watkins RG. The spine in sports. St. Louis: Mosby; 1996. 
  19. ↑ Hosea TM, Hannafin JA. Rowing Injuries. Sports Health: A Multidisciplinary Approach [Internet]. 2012 Apr 26 [cited 2019 Jul 26];4(3):236–45. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3435926/#bibr21-1941738112442484
  20. ↑ 20.0 20.1 Fehlings M, Singh A, Tetreault L, Kalsi-Ryan S, Nouri A. Global prevalence and  incidence of traumatic spinal cord injury. Clinical Epidemiology. 2014 Sep;6(2014):309.
  21. ↑ 21.0 21.1 21.2 NSCISC. Spinal Cord Injury Facts and Figures at a Glance 2019 SCI Data Sheet [Internet]. 2019. Available from: https://www.nscisc.uab.edu/Public/Facts%20and%20Figures%202019%20-%20Final.pdf
  22. ↑ Aito S, D’Andrea M, Werhagen L. Spinal cord injuries due to diving accidents. Spinal  Cord. 2004 Nov 23;43(2):109–16.
  23. ↑ NSCISC. Spinal Cord Injury Facts and Figures at a Glance. The Journal of Spinal Cord Medicine. 2012 Jan;35(1):68–9.
  24. ↑ RBC Wealth Management. Professional athletes need a retirement game plan - RBC  Wealth Management [Internet]. www.rbcwealthmanagement.com. Available from:  https://www.rbcwealthmanagement.com/us/en/research-insights/professional-athletes-need-a retirement-game-plan/detail/
  25. ↑ NSC Injury Facts. Deaths by Age Group [Internet]. Injury Facts. 2020. Available from: https://injuryfacts.nsc.org/motor-vehicle/historical-fatality-trends/deaths-by-age-group/
  26. ↑ 26.0 26.1 Zigler J. Spine Trauma 2nd Edition. American Academy of Orthopaedic Surgeons; 2011.
  27. ↑ SCI Progress. Spinal Cord Injury Levels [Internet]. 2020 [cited 2021 Nov 11]. Available from: https://sciprogress.com/spinal-cord-injury-levels/#Thoracic_Spinal_Cord_Injuries
  28. ↑ Mattucci S, Speidel J, Liu J, Kwon BK, Tetzlaff W, Oxland TR. Basic biomechanics of  spinal cord injury — How injuries happen in people and how animal models have informed  our understanding. Clinical Biomechanics. 2019 Apr;64:58–68.
  29. ↑ Sekhon LHS, Fehlings MG. Epidemiology, Demographics, and Pathophysiology of Acute Spinal Cord Injury. Spine. 2001 Dec;26(Supplement):S2–12.
  30. ↑ KEARNEY PA, RIDELLA SA, VIANO DC, ANDERSON TE. Interaction of Contact  Velocity and Cord Compression in Determining the Severity of Spinal Cord Injury. Journal  of Neurotrauma. 1988 Jan;5(3):187–208.
  31. ↑ Fehlings MG, Vaccaro A, Wilson JR, Singh A, W. Cadotte D, Harrop JS, et al. Early versus Delayed Decompression for Traumatic Cervical Spinal Cord Injury: Results of the Surgical Timing in Acute Spinal Cord Injury Study (STASCIS). Di Giovanni S, editor. PLoS ONE [Internet]. 2012 Feb 23 [cited 2019 Apr 19];7(2):e32037. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3285644/
  32. ↑ Grassner L, Wutte C, Klein B, Mach O, Riesner S, Panzer S, et al. Early Decompression  (< 8 h) after Traumatic Cervical Spinal Cord Injury Improves Functional Outcome as  Assessed by Spinal Cord Independence Measure after One Year. Journal of Neurotrauma.  2016 Sep 15;33(18):1658–66.
  33. ↑ 33.0 33.1 Wilson JR, Singh A, Craven C, Verrier MC, Drew B, Ahn H, et al. Early versus late surgery for traumatic spinal cord injury: the results of a prospective Canadian cohort study. Spinal Cord. 2012 May 8;50(11):840–3.
  34. ↑ 34.0 34.1 34.2 34.3 34.4 34.5 Mannen EM, Anderson JT, Arnold PM, Friis EA. Mechanical analysis of the human  cadaveric thoracic spine with intact rib cage. Journal of Biomechanics. 2015  Jul;48(10):2060–6. 
  35. ↑ Bruno AG, Anderson DE, D’Agostino J, Bouxsein ML. The effect of thoracic kyphosis  and sagittal plane alignment on vertebral compressive loading. Journal of Bone and Mineral Research: The Official Journal of the American Society for Bone and Mineral Research  [Internet]. 2012 Oct 1 [cited 2021 Sep 9];27(10):2144–51. Available from:  https://pubmed.ncbi.nlm.nih.gov/22589006/
  36. ↑ Ilharreborde B, Zhao K, Boumediene E, Gay R, Berglund L, An KN. A dynamic method for in vitro multisegment spine testing. Orthopaedics & traumatology, surgery & research: OTSR [Internet]. 2010 Jun 1 [cited 2021 Nov 11];96(4):456–61. Available from: https://pubmed.ncbi.nlm.nih.gov/20452304/
  37. ↑ Sangiorgio SN, Borkowski SL, Bowen RE, Scaduto AA, Frost NL, Ebramzadeh E. Quantification of Increase in Three-dimensional Spine Flexibility Following Sequential Ponte Osteotomies in a Cadaveric Model. Spine Deformity [Internet]. 2013 May 1 [cited 2021 Nov 11];1(3):171–8. Available from: https://www.sciencedirect.com/science/article/abs/pii/S2212134X13000075
  38. ↑ 38.0 38.1 Andriacchi T, Schultz A, Belytschko T, Galante J. A model for studies of mechanical  interactions between the human spine and rib cage. Journal of Biomechanics. 1974  Nov;7(6):497–507. 
  39. ↑ Panjabi MM, Krag M, Summers D, Videman T. Biomechanical time-tolerance of fresh cadaveric human spine specimens. Journal of Orthopaedic Research. 1985;3(3):292–300.
  40. ↑ Liebschner MAK, Kopperdahl DL, Rosenberg WS, Keaveny TM. Finite element  modeling of the human thoracolumbar spine. Spine [Internet]. 2003 Mar 15 [cited 2021 Nov  11];28(6):559–65. Available from: https://pubmed.ncbi.nlm.nih.gov/12642762/
  41. ↑ Bozkus H, Crawford NR, Chamberlain RH, Valenzuela TD, Espinoza A, Yüksel Z, et al. Comparative anatomy of the porcine and human thoracic spines with reference to thoracoscopic surgical techniques. Surgical Endoscopy And Other Interventional Techniques [Internet]. 2005 Dec 1 [cited 2021 Nov 11];19(12):1652–65. Available from: https://link.springer.com/article/10.1007%2Fs00464-005-0159-9.
  42. ↑ Campbell JQ, Tannous RE. Using a Finite Element Model to Predict Thoracic Injuries. IV  Latin American Congress on Biomedical Engineering 2007, Bioengineering Solutions for  Latin America Health. 2007;690–2.
  43. ↑ Lee JHT, Jones CF, Okon EB, Anderson L, Tigchelaar S, Kooner P, et al. A Novel Porcine Model of Traumatic Thoracic Spinal Cord Injury. Journal of Neurotrauma. 2013 Feb;30(3):142–59.
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