Cervical Instability

Original Editor - <a href="User:Mary-Kate McCoy">Mary-Kate McCoy</a> and <a href="User:Heather Lampe">Heather Lampe</a> as part of the <a href="Temple University Evidence-Based Practice Project">Temple University EBP Project</a>

Top Contributors - Vanbeylen Antoine, Mary-Kate McCoy, Rachael Lowe, Admin, Pieter Piron, Sara Evenepoel, David Herteleer, Kim Jackson, Lucinda hampton, Heather Lampe, Laura Ritchie, Nick Van Doorsselaer, Daniele Barilla, Tony Lowe, Scott A Burns, WikiSysop, Simisola Ajeyalemi, Jess Bell, Olajumoke Ogunleye, Beth Potter, Evan Thomas and 127.0.0.1

Search strategy

Internet is a gigantic source of knowledge. Databases such as PubMed, Web of Science, PEDro or Google Scholar can be useful. Use keywords as ‘Cervical instability’, ‘Instability of the cervical spine’, etc. . For specific information you can add ‘AND’ followed by ‘physical therapy’, ‘characteristics’, ‘definition’, 'treatment', depending of the need.

Definition/Description

Cervical instability describes a wide range of conditions from neck pain and deformation without any clear proof over little malformations too complete failure of intervertebral connectionHunningher A, Calder I, (2007), Cervical Spine Surgery ,Contin Educ Anaesth Crit Care Pain (3): 81-84.. White et al (1975)White AA et al (1975), Biomechanical analysis of cervical stability in the cervical spine Clin Orthop Relat Res; (109):85-96.  and Panjabi (1992) Panjabi, M. M. “The Stabilizing System of the Spine. Part II. Neutral Zone and Instability Hypothesis.” Journal of Spinal Disorders 5, no. 4: 390–397, December 1992 (Level of evidence 5)described cervical stability as the loss of ability of cervical spine under physiological loads to maintain relationships between vertebrae in such a way, that spinal cord or nerve roots are damaged or irritated and deformity or pain develops.

Clinically Relevant Anatomy

The cervical spine consist of 7 separate vertebrae. The first two vertebrae (referred as upper cervical spine) are highly specialized and differ from the other 5 cervical vertebrae (lower cervical) regarding anatomical structure and function.

The upper cervical spine is made of the atlas (C1) and the axis (C2). It comprises of two joint structures: one in between os occipital and atlas (atlanto-occipital joint), the other one between atlas and axis, which forms the atlanto-axial joint. The atlantoaxial joint is responsible for 50% of all cervical rotation; the atlanto-occipital joint is responsible for 50% of flexion and extension. Windsor, R. “Cervical Spine Anatomy.” Updated april 9, 2013 (http://emedicine.medscape.com/article/1948797-overview#a30)

<img src="/images/thumb/e/e6/Cervical_instability_anatomy.png/250px-Cervical_instability_anatomy.png" _fck_mw_filename="Cervical instability anatomy.png" _fck_mw_location="left" _fck_mw_width="250" alt="" class="fck_mw_left" />

The craniocervical junction (atlanto-occipital joint), the lower atlanto-axial joint and other cervical segments are reinforced by internal as well as external ligaments. They secure the spinal stability of the cervical spine as a whole, together with surrounding postural muscles and allow cervical motion. They also provide proprioceptive information throughout the spinal nerve system to the brain.

The cervical spine has sacrificed stability for mobility and is therefore vulnerable to injury.
The total ROM of a spinal segment may be divided into two zones:
- Neutral zone: motion occurring in this zone is produced against a minimal passive resistance.
- Elastic zone: motion occurring in occurring near the end-range of spinal motion is produced against increased passive resistance.

<img src="/images/4/4f/Cervical_spine_anatomy.jpg" _fck_mw_filename="Cervical spine anatomy.jpg" _fck_mw_location="right" alt="" class="fck_mw_right" />

There are many authors that identified common components of spinal stability. Panjabi(1992)conceptualized the components into 3 functionally integrated subsystems of the spinal stabilizing system ^{K.A. Olson, D. Joder, Diagnosis and treatment of Cervical Spine Clinical Instability, Journal of Orthopaedic &amp;amp;amp; Sports Physical Therapy, April 2001. Level of Evidence 4M. Takeshi et Al., Soft-Tissue Damage and Segmental Instability in Adult Patients with Cervical Spinal Cord Injury Without Major Bone Injury, Spine Journal, December 2012.fckLRLevel of Evidence 2B} (LOE: 3B,2C):

• The passive subsystem:

- Consists of vertebral bodies, facet joints and capsules, spinal ligaments (lig. longitudinale anterius and posterius, ligamentum interspinosum, lig. Interspinosus and lig. Flavum).^{R. Banerjee et Al., Catastrophic Cervical Spine Injuries in the Collision Sport Athlete, Part 1 Epidemiology, Functional Anatomy, and Diagnosis, The American Journal of Sports Medicine, 2004. Level of Evidence 2A}(LOE 2A)
- Passive tension from spinal muscles and tendons.
- Provides significant stabilization of the elastic zone and limits the size of the neutral zone.
- Acts as a transducer and provides the neural control subsystem with information about vertebral position and motion

• The active subsystem:

- Consists of spinal muscles and tendons, such as: M. multifidus cervicis, M. Longus capitis and the M. Longus Colli.W.Platzer, Atlas van de Anatomie, Bewegingsapparaat, Sesam, 1999. Level of Evidence 5(LOE: 5)
- Generates forces required to stabilize the spine in response to changing loads.
- Controls the motion occurring within the neutral zone and contributes to maintain the size the size of the neutral zone.
- Acts also as a transducer by providing the neural control subsystem with information about the forces generated by each muscle.

• The neural control subsystem:

- Consists of peripheral nerves and the central nervous system.
- Receives information from the transducers of the passive and active subsystems about vertebral position, vertebral motion, and forces generated by spinal muscles. The subsystem determines the requirements for spinal stability and acts on the spinal muscles to produce the required forces.

Clinical instability of the spine occurs when the neutral zone increases relative to the total ROM, the stabilizing subsystems are unable to compensate for this increase, which causes a poor and uncontrolled quality of motion in the neutral zone. ^{Choudhary AK, Ishak R, Zacharia TT, Dias MS. Imaging of spinal injury in abusive head trauma: a retrospective study. Pediatr Radiol. 2014 Sep. 44 (9):1130-40.}(LOE: 3B, 2C, 2A).

Epidemiology /Etiology

Cervical instability is often diagnosed in patients with rheumatoid arthritis, due to the progressive destruction of the cervical skeletal structures. The most affected region is the suboccipital region and another regions of the cervical spine C4-C5. Macovei, Luana-Andreea, and Elena Rezuş. “CERVICAL SPINE LESIONS IN RHEUMATOID ARTHRITIS PATIENTS.” Revista Medico-Chirurgicală̆ a Societă̆ţ̜ii De Medici Ş̧i Naturaliş̧ti Din Iaş̧i 120, no. 1 (March 2016): 70–76. (Level of evidence 2B)(LOE: 2B)
The atlanto-axial instability (AAI) is considerd as a developmental anomaly often occurring in patient with the down’s syndrome (DS). It affects 6.8 to 27% of the population with DS.Myśliwiec, Andrzej, Adam Posłuszny, Edward Saulicz, Iwona Doroniewicz, Paweł Linek, Tomasz Wolny, Andrzej Knapik, Jerzy Rottermund, Piotr Żmijewski, and Paweł Cieszczyk. “Atlanto-Axial Instability in People with Down’s Syndrome and Its Impact on the Ability to Perform Sports Activities - A Review.” Journal of Human Kinetics 48 (November 22, 2015): 17–24. (Level of evidence 2A) (LOE: 2A)
Futhermore cervical instability can also be a cause of delayed or missed diagnosis of cervical spine injury occured after trauma(car accident, high impact on the neck…) . Altought this occures in very rare case its incidence is between 4.9 to 20%.Yeo, Chang Gi, Ikchan Jeon, and Sang Woo Kim. “Delayed or Missed Diagnosis of Cervical Instability after Traumatic Injury: Usefulness of Dynamic Flexion and Extension Radiographs.” Korean Journal of Spine 12, no. 3 (September 2015): 146–49 (Level of evidence 3B) (LOE: 3B)

Risk Factors

The following risk factors are associated with the potential for bony or ligamentous compromise of the upper cervical spineCook C, Brismee JM, Fleming R, et al (2005). Identifiers suggestive of clinical cervical spine instability: a Delphi study of physical therapists. Physical Therapy 85(9):895-906.:

• History of trauma (e.g. whiplash, rugby neck injury)
• Throat infection
• Congenital collagenous compromise (e.g. syndromes: Down’s, Ehlers-Danlos, Grisel, Morquio)
• Inflammatory arthritides (e.g. rheumatoid arthritis, ankylosing spondylitis)
• Recent neck/head/dental surgery.

Characteristics/Clinical Presentation

Until this day there is no golden standard or acceptable measurement to diagnose cervical instability. Cervical instability is diagnosed as a combination of clinical findings and X-ray both dynamic and static. It is generally accepted that cervical instability is caused by trauma (one major trauma or repetitive microtrauma), rheumatoid arthritis or a tumor. Cervical instability leads to degenerative changes which effects the motion segment but may not be confused with severe incapacity or other signs of spinal cord compression.
A list of clinical findings composed by Magee et alMagee DJ, Zachazewski JE, Quillen WS (2009) Cervical spine in Pathology an intervention in Musculoskeletal Rehabilitation p17-63 door Magee DJ, Zachazewski JE, Quillen WS, St-Louis, Saunders Elsevier:

• Neckpain
• Complaints of locking/catching in the neck
• Weakness of the neck
• Altered ROM
• Neck pain and/or headaches provoked by sustained weightbearing postures and a relieve of those complaints in non-weighbearing positions
• Hypermobility and soft end-feeling in passive therapie
• Poor cervical muscle strength (multifidus, longus capitis, longus colli)

The findings in X-ray from Cervical Spine by Clark CLClark CL et al, Functional anatomy of joints ligaments and disks in Cervical Spine 4th ed.p 46-54 door Clark CL, Philadelphia, Lipincott Wlliams &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp; Wilkins that combined with clinical findings can lead to a diagnosis of cervical instability.

Differential Diagnosis

It’s important to remember that problems in de neck region can be masked by problems in other regions of the body. A frozen shoulder (adhesive capsulitis) for example can be seen in conjunction with a cervical radiculopathy. Other shoulder pathologies such as brachial plexitis can also cause pain and weakness of muscles in the shoulder-neck-region. (LOE 5)

Neckpain, weakness and other characteristics also present in cervical spine instability can also be seen in the following cervical diseases (LOE 5):

• Central or lateral <a href="http://www.physio-pedia.com/Disc_Herniation">disc herniation</a>
• <a href="http://www.physio-pedia.com/Guillain-Barre_Syndrome">Guillain-Barré syndrome</a>
• <a href="http://www.physio-pedia.com/Cervical_Spondylosis">Cervical spondylosis</a>
• Pathologic fracture
• <a href="http://www.physio-pedia.com/Cervical_Stenosis">Cervical canal stenosis</a>
• <a href="http://www.physio-pedia.com/Facet_Joint_Syndrome">Facet joint pathologies</a>
• Cervical strain
• Cervical trauma or fracture
• Occipital headaches
• Degenerative disease of the spine
• Previously undiagnosed syndrome
• Neurological involvement
• Progressive neck pain
• Resistant neck pain 
  
• Infections: discitis, <a href="http://www.physio-pedia.com/Osteomyelitis">osteomyelitis</a>, etc. 

Diagnostic Procedures

Cervical instability is a diagnosis based primarily on a patient’s history (ie, symptoms) and physical examination because there is yet to be standardized functional X-rays or imaging able to diagnose cervical instability or detect ruptured ligamentous tissue without the presence of bony lesions. Volle E. Functional magnetic resonance imaging video diagnosis of soft-tissue trauma to the craniocervical joints and ligaments. Int Tinnitus J. 2000;6(2) (Level of evidence: 2B) (LOE 2B)
Furthermore, there is often little correlation between the degree of instability or hypermobility shown on radiographic studies and clinical symptoms. Even after severe whiplash injuries, plain radiographs are usually normal despite clinical findings indicating the presence of soft tissue damage. Van Mameren H, Drukker J, Sanches H, Beursgens J. Cervical spine motion in the sagittal plane (I) range of motion of actually performed movements, an x-ray cinematographic study. Eur J Morphol. 1990;28(1): 47–68 (Level of evidence: 2B) (LOE 2B)

MRI images could be useful to screen the integrity of the vertebral ligaments. Taking images during an anterior shear test or a distraction test shows a greater intervertebral distance and an increase in direct length of the ligamentsOsmotherly PG, Rivett DA, Rowe LJ. The anterior shear and distraction tests for craniocervical instability. An evaluation using magnetic resonance imaging. Man Ther. 2012 Oct;17(5):416-21. Level of evidence: 1B.
However, functional computerized tomography (fCT) and magnetic resonance imaging (fMRI) scans and digital motion x-ray (DMX) are able to adequately depict cervical instability pathology . Studies using fCT for diagnosing soft tissue ligament or post-whiplash injuries have demonstrated the ability of this technique to show excess atlanto-occipital or atlanto-axial movement during axial rotation . This is especially pertinent when patients have signs and symptoms of cervical instability, yet have normal MRIs in a neutral position.
Functional imaging technology, as opposed to static standard films, is necessary for adequate radiologic depiction of instability in the cervical spine because they provide dynamic imaging (flexion and extension images of the spine) of the neck during movement and are helpful for evaluating the presence and degree of cervical instability.Radcliff K, Kepler C, Reitman C, Harrop J, Vaccaro A. CT and MRI-based diagnosis of craniocervical dislocations the role of the occipitoatlantal ligament. Clin Orthop Rel Res. 2012 (Level of evidence: 2B)Antinnes J, Dvorak J, Hayek J, Panjabi MM, Grob D. The value of functional computed tomography in the evaluation of soft-tissue injury in the upper cervical spine. Eur Spine J. 1994;3: 98–101 (Level of evidence: 2B) (LOE 2B)

As Magee et al listed, poor cervical muscle endurance is one of the clinical findings we find with cervical instability. A good way to test these muscles (the deep cervical flexor muscles, the longus capitis and longus colli) is the craniocervical flexion test. The CCFT could be described as a test of neuromotor control.

The features that are tested are the activation and isometric endurance of the deep cervical flexors as well as their interaction with the superficial cervical flexors (the sternocleidomastoid and the anterior scalene) during the performance of five progressive stages of increasing craniocervical flexion range of motion. It is a low-load test performed in the supine position with the patient guided to each stage by feedback from a pressure sensor placed behind the neck. While the test in the clinical setting provides only an indirect measure of performance, the construct validity of the CCFT has been verified in a laboratory setting by direct measurement of deep and superficial flexor muscle activity. If the 5 stages can’t be completed by the patient, the deep cervical flexor muscles need to be trained. Gwendolen AJ et al; Clinical assessment of the deep cervical flexor muscles: the craniocervical flexion test. J Manipulative Physiol Ther 2008 Sep;31(7):525-33. (Level of evidence 2C)(LOE 2C)

Cook et al. (2005) tired to obtain consensus of symptoms and physical examination findings associated with clinical cervical spine instability (CCSI). The study resulted in a list of 16 symptoms and 12 physical examination findings that is associated with CCSI.

The related symptoms listed in descending rank of relationship are:

1. Intolerance to prolonged static postures
2. Fatigue and inability to hold head up
3. Better with external support, including hands or collar
4. Frequent need for self-manipulation
5. Feeling of instability, shaking, or lack of control
6. Frequent episodes of acute attacks
7. Sharp pain, possibly with sudden movements
8. Head feels heavy
9. Neck gets stuck, or locks, with movement
10. Better in unloaded position such as lying down
11. Catching, clicking, clunking, and popping sensation
12. Past history of neck dysfunction or trauma
13. Trivial movements provoke symptoms
14. Muscles feel tight or stiff
15. Unwillingness, apprehension, or fear of movement
16. Temporary improvement with clinical manipulation
    
    

Outcome Measures

To measure chronic neck pain we can use the neck disability index, the neck bournemouth questionnaire or the neck pain and disability scale. These three questionnaires are specific and valid instruments to evaluate the neckpain and dysfunction. Ralph E. Gay; Comparison of the Neck Disability Index and the Neck Bournemouth Questionnaire in a sample of patients with chronic uncomplicated neck pain; Journal of Manipulative and Physiological Therapeutics. Volume 30, Issue 4, May 2007, Pages 259–262 (Level of evidence 1B)Steven J Linton, A cognitive-behavioral group intervention as prevention for persistent neck and back pain in a non-patient population: a randomized controlled trial; Volume 90, Issues 1–2, 1 February 2001, Pages 83–90 (Level of evidence 1B)(LOE 1B)
The pain catastrophizing scale can be used to evaluate how the patient experiences the pain. It measures the rumination, magnification and helplessness of the patient. (LOE 1B)

Examination

Little is known about the diagnostic accuracy of upper cervical spine instability testsHutting N, Scholten-Peeters GG, Vijverman V, Keesenberg MD, Verhagen AP. Diagnostic accuracy of upper cervical spine instability tests: a systematic review.Phys Ther. 2013 Dec;93(12):1686-95. doi: 10.2522/ptj.20130186. Epub 2013 Jul 25..

• <a href="Sharp Purser Test">Sharp-Purser Test</a> 
• <a href="Transverse Ligament Stress Test">Transverse Ligament Stress Test</a>
  

Medical Management

In the past few decades nonoperative maneuvers like traction, cast immobilization and long periods of bed rest had been replaced by the use of instrumentation to stabilize the spine after a trauma. This method can reduce the risk of negative sequelae of long term bed restKandziora F, Pflugmacher R, Scholz M, Schnake K, Putzier M? Khodadadyan-Klostermann C, Haas NP. Posterior stabilization of subaxial cervical spine trauma: indications and techniques. Injury 2005 Jul;36 Suppl 2:B36-43. (Level of Evidence IA) Review. The cervical stability can be received by using posterior fixation such as lateral mass plating, processus spinosus or facet wiring and cervical pedicle screws. The choice of which fixation is best, can be made by the surgeon after seeing a CT-scan or MRI. In a retrospective study of Fehlings, the cervical spine stabilization was successful in 93% off the cases.  Obviously this fixation procedure also holds some risks. It is possible that the spinal cord, vertebral artery, spinal nerve and facet joints get injured. Levine et al. reported radicular symptoms in 6 of their 72 patientsEbraheim N. Posterior lateral mass screw fixation: anatomic and radiographic considerations. The University of Pennsylvania Orthopaedic Journal 12: 66-72, 1999. (Level of evidence Ia) Review.

Physical Therapy Management

The goal of the physical treatment is to enhance the function of the spinal stabilizing subsystems and to decrease the stresses on the involved spinal segments.

• Posture education and spinal manipulation:

- Decreases stresses on the passive subsystem.
- Proper posture: reduces the loads placed on the spinal segments at end-ranges and returns the spine to a biomechanically efficient position.
- Spinal manipulation can be performed on hypomobile segments above and below the level of instability, what eventually will result in a distribution of the spinal movement across several segments. Also the mechanical stresses on the level of clinical instability are believed to be decreased. ^{[10] Level of Evidence 4}
- Video over joint mobilization: https://www.youtube.com/watch?v=Rn1Ed2SxTx0

• Strengthening exercises:

- Enhances the function of the active subsystem.
- The cervical multifidus may provide stability via segmental attachments to cervical vertebrae.
- The m. longus colli and capitus provide anterior stability.
- Strengthening the stabilizing muscles may enable those muscles to improve the quality and control of movement occurring within the neutral zone.^{[10] Level of Evidence 4, [13] Level of Evidence 2B}

• Exercise video: Neck strength and stability

In a more specific situation such as post-operative revalidation for example in the case of a cervical fusion, the treatment can differ as described hereunder.

• The patient is not required to wear a brace. After 6 weeks it is not encouraged to do any lifting more than 4kg as also overhead work. The rehabilitation begins at week 6, mostly a basic stability exercises program. No cervical strengthening or ranges of motion exercises are encouraged in the first 6 months.The exercises or mainly focused on the neutral postural alignment, were the patients are recommended to us there trunk, hips and chest to produce proper cervical alignment. For other types of operations the treatment-plan will be defined in function of the critical nature of the trauma.^{[19]Level of Evidence 5}
  
  

Key Research

- P.G. Osmotherly et Al., Knowledge and use of craniovertebral instability testing by Australian physiotherapists, Elsevier, 2011. ^{[13] Level of Evidence 2B}

Resources

- K.A. Olson, D. Joder, Diagnosis and treatment of Cervical Spine Clinical Instability, Journal of Orthopaedic & Sports Physical Therapy, April 2001. ^{[10] Level of Evidence 4}

Clinical Bottom Line

Clinical cervical spine instability (CCSI) is controversial and difficult to diagnose. Within the literature, no clinical or diagnostic tests that yield valid and reliable results have been described to differentially diagnose this condition. ^[10]
The screening by tests for upper cervical instability cannot be done accurately at the moment. ^{[11] level of Evidence 2B}

Recent Related Research (from <a href="http://www.ncbi.nlm.nih.gov/pubmed/">Pubmed</a>)

http://www.ncbi.nlm.nih.gov/entrez/eutils/erss.cgi?rss_guid=1R9m212NERpyMp_66xm834NdnQhQNw_US8FenznWOVNw-oOoxU%7Ccharset=UTF-8%7Cshort%7Cmax=10

References

1. Inamasu J, Nakatsukasa M, Hirose Y. Computed tomography evaluation of the brain and upper cervical spine in patients with traumatic cardiac arrest who achieved return of spontaneous circulation. Neurol Med Chir (Tokyo). 2013. 53 (9):585-9. ^{[1] Level of Evidence 4}
2. Hill BW, Song B, Morgan RA, Kang MM. The Role of Adjustable Scout Lines in Advanced Cervical Spinal Imaging. J Spinal Disord Tech. 2013 Nov 6. ^{[2] Level of Evidence 2B}
3. Choudhary AK, Ishak R, Zacharia TT, Dias MS. Imaging of spinal injury in abusive head trauma: a retrospective study. Pediatr Radiol. 2014 Sep. 44 (9):1130-40.^[3]
4. Qualls D, Leonard JR, Keller M, Pineda J, Leonard JC. Utility of magnetic resonance imaging in diagnosing cervical spine injury in children with severe traumatic brain injury. J Trauma Acute Care Surg. 2015 Jun. 78 (6):1122-8.^[4]
5. Hannon M, Mannix R, Dorney K, Mooney D, Hennelly K. Pediatric cervical spine injury evaluation after blunt trauma: a clinical decision analysis. Ann Emerg Med. 2015 Mar. 65 (3):239-47. ^[5]
6. James IA, Moukalled A, Yu E, Tulman DB, Bergese SD, Jones CD, et al. A systematic review of the need for MRI for the clearance of cervical spine injury in obtunded blunt trauma patients after normal cervical spine CT. J Emerg Trauma Shock. 2014 Oct. 7 (4):251-5. ^[6]
7. Kanji HD, Neitzel A, Sekhon M, McCallum J, Griesdale DE. Sixty-four-slice computed tomographic scanner to clear traumatic cervical spine injury: systematic review of the literature. J Crit Care. 2014 Apr. 29 (2): 314.e9-13.^[7]
8. Hutting N., Diagnostic Accuracy of Upper Cervical Spine Instability: A systematic Review. Journal of the American Physical Therapist Association, July 2013, vol.93, 1686-1695 ^{[8]Level of Evidence 1A)}
9. Magee DJ, Zachazewski JE,Quillen Ws : Cervical spine in Pathology an intervention in Musculoskeletal Rehabilitation p17-63 ,2009, St-Louis, Saunders Elsevier ^{[9] Level of Evidence 5}
10. K.A. Olson, D. Joder, Diagnosis and treatment of Cervical Spine Clinical Instability, Journal of Orthopaedic & Sports Physical Therapy, April 2001. ^{[10]Level of Evidence 4}
11. M. Takeshi et Al., Soft-Tissue Damage and Segmental Instability in Adult Patients with Cervical Spinal Cord Injury Without Major Bone Injury, Spine Journal, December 2012.
^{[11]Level of Evidence 2B}
12. C. Cook et Al., Identifiers Suggestive of Clinical Cervical Spine Instability: A Delphi Study of Physical Therapists, Journal of the American Physical Therapy Association, September 2005 ^{[12]Level of Evidence 2C}
13. P.G. Osmotherly et Al., Knowledge and use of craniovertebral instability testing by Australian physiotherapists, Elsevier, 2011. ^{[13]Level of Evidence 2B}
14. Howard S. An, Scott D. Boden, William C. Lauerman, Lawrence G. Lenke, Robert F. McLain. “The adult and pediatric spine: Volume 2” by Lippincott Williams & Wilkins. 2004. (3th edition) ^{[14]Level of Evidence 5}
15. Kenneth A. Olson et al. “Diagnosis and Treatment of Cervical Spine Clinical Instability”.
Journal of Orthopaedic & Sports Physical Therapy 2001;31(4):194-206
^{[15] Level of Evidence 4}
16. Steilen D., Hauser R., Woldin B. and Sawyer S. “Chronic Neck Pain: Making the Connection Between Capsular Ligament Laxity and Cervical Instability” The Open Orthopaedics Journal, 2014, volume 8, 326-345. ^{[16]Level of Evidence 2B}
17. R. Banerjee et Al., Catastrophic Cervical Spine Injuries in the Collision Sport Athlete, Part 1 Epidemiology, Functional Anatomy, and Diagnosis, The American Journal of Sports Medicine, 2004. ^{[17]Level of Evidence 2A}
18. W.Platzer, Atlas van de Anatomie, Bewegingsapparaat, Sesam, 1999.^{[18]Level of Evidence 5}
19. C.Liebenson, Rehabilitation of The Spine, Lippincott Williams & Wilkins, p927, 2007.^{[19]Level of Evidence 5}

<a _fcknotitle="true" href="Category:Cervical_Conditions">Cervical_Conditions</a>