The Flexion-Distraction Test

The flexion-distraction test (FDT) is an essential test for any chiropractic practitioner treating patients involved in motor-vehicle collisions (MVC). The FDT can aid in the diagnosis of otherwise-undiscovered thoracic and lumbar central disc herniations, endplate fractures, vertebral body microfracture (VBMF), posterior ligamentous complex (PLC) injuries described by Denis, and posttraumatic syringomyelia (PTS).¹

The information provided in this article is specific to traumatic MVC injury diagnosis, although it may apply to acute home- / work-type injuries as well.

Performing the FDT

You can perform the FDT as early as 24 hours after injury. The test / manipulation allows for important early mobilization of the thoracic and lumbar vertebrae and injured soft tissues.^2-5

The FDT is performed first by properly positioning the patient in the prone position comfortably on a manual or mechanical flexion-distraction table with the patient's head over the headrest paper. Do not attach the ankle cuffs if the table is so equipped. If the patient has any flexion antalgia, bend (flex) the table so they can lie comfortably in the correct position.

Instruct the patient that the goals of the procedure are to simply provide stretch to the healing soft-tissue injuries. No sharp or spike pain is allowed. If spike or sharp pain is perceived by the patient, they are to notify you of the location of the painful sensation.

With your hand, apply minimal downward pressure over the test levels. Take care not to specifically anchor the spinous process, as with the COX technique or the Cox Tolerance Test.⁶

The FDT evaluates the patient for severe thoracic and lumbar MVC trauma. The FDT is applied with the following amount of downward pressure: at T2 (3-4 lbs), T10 (5 lbs), and L3 (5 lbs), and a knife-edge contact, fingers oriented laterally at the sacral base (5-10 lbs). Training with a mail scale is helpful to develop the correct pressure for testing purposes.

Begin the FDT by contacting each test section and flexing the table to the point at which only a light, comfortable stretch sensation is noted by the patient. Continued verbalization to the patient to allow only for light stretch without sharp pain is recommended during the test. In this manner, in the third to fourth week, the patient will be able to discern a normal light stretch vs. the significance of a sharp, localized pain (to be discussed later).

Continued verbalization to the patient to allow only for light stretch without sharp pain is recommended during the test, and builds patient confidence that the test / care should not hurt.

Contraindications / Considerations

Perform three FDT repetitions lasting 5-6 seconds, from neutral to flexed position and back to neutral, per segment. Beginning at T2, proceed to T10, then to L3 and finally to the sacrum on three successive passes unless the patient notes general soreness or sharp pain. If general soreness or sharp pain is noted on the first or second pass, end the test for the day even if only one pass through the 2-4 levels was made based upon the regions injured in the MVC.

It's extremely important to perform the test only at these specific levels. Performing the FDT at known spinal fracture or herniated disc (HD) levels could be a contraindication to care or at least prove ineffective in the patient's recovery.^7-9

Spinal segments T12-L2 are common fracture sites with MVC trauma.¹⁰ Lumbar spinal segments most commonly exhibiting herniated disc injury with decreasing probability are L5-S1, L4-L5 and finally L3-4.¹¹

The L3 segment was selected to test for more caudal herniated discs, as it is a less common HD site. Vertebral body microfracture (VBMF) in the mid-thoracic spine can occur with compression-type injuries; therefore, T3-T9 are avoided as test sites.¹²

If performed initially following the date of the MVC, you may not be able to flex (lower) the back of the table even to ½ inch following the above guideline to allow only the feeling of light stretch by the patient. Flexing the table too deep may produce a false-positive finding, as acute tissue strain and sprain may understandably depolarize nociceptors if healing tissues are overly tensioned prior to a sufficient recovery state.^13-15

This can occur if too much tension is applied to strained / sprained tissue still in the acute stage, which may last through the initial three-week post-collision time period according to the Quebec Task Force.¹⁶

The FDT successfully duplicates the primary MVC injury mechanics. Punjabi and White describe the Major Injuring Vector (MIV) of a disc herniation, ligamentous sprain (subfailure) and vertebral body injury (fracture,VBMF) to occur when there is forceful movement around the X axis. Vertebral body flexion with sheer loading are responsible for the injury.17

Farfan, et al., note that annular failure occurs with sheer loading.¹⁸ Traumatic spondylolisthesis occurs due to shearing or distraction-type MIV and is generally accompanied by anterior and/or posterior longitudinal ligament injuries.¹⁹

Pre-MVC flexion of the lumbar spine can occur with slumped posturing at impact and again when the abdomen comes into contact with the restraint mechanism of the lap belt if the impact occurs from the rear.²⁰

Test Relevance

If no sharp pain is felt by the patient during the performance of the FDT in the 3-4 weeks post-injury, the test is negative (-) and you should be confident that the patient is suffering from a strain or sprain condition in the thoracic and lumbar spine.

Beyond the third week following the MVC injury, Croft notes that muscle tissue is well on its way to symptomatic reduction and approximating full healing.²¹ A segmental level of sharp pain at the test segment or anywhere in the thoracic and/or lumbar spine indicates a positive (+) FDT.

The FDT has indicated acute central disc herniation, endplate fracture, VBMF, pars interarticularis fracture, PCL subfailure of Denis and PTS when later evaluated with MRI. Clarification of a (+) FDT by MR evaluation is suggested to diagnose the underlying pathology.

Clinical Significance

The test has been performed in my practice on more than 1,200 acutely injured MVC patients covering a seven-year period (ongoing). The FDT test has also been performed on 347 patients with confirmed MRI / CT scan-verified healed disc herniation, endplate or trabecular fracture. Acute disc herniations were discovered in 35% of the test cases with as little as 2-3 inches of FD table drop. No painful symptoms and only muscle stretch were identified with the non-acute MVC test subjects when the test was performed as described above.

No healed or stabilized posttraumatic syrinx or PCL subjects were tested, likely due to the rarity of the conditions. Posttraumatic syringomyelia (PTS) occurs in 1-7% of spinal-cord-injury cases, occurring predominantly in male patients.²² Two PTS cases that I have diagnosed utilizing the FDT were female following a contrast-enhanced MRI test. Two VBMF patients were identified during the seven-year period.

Clinical Pearls

The FDT in its administration provides 1-3 levels of chiropractic manipulative therapy (CMT), depending on how many regions are injured in the MVC. Like any other individual physical-examination test, it has no specific CPT or E&M coding. Flexion-distraction manipulation is graded as a CMT procedure and therefore is coded depending upon the region(s) of manipulation provided by the provider.²³

Uncontested injuries discovered by the FDT, when further documented by MRI evaluation, provide value-building points for Colossus and other injury-gauging algorithms.

Editor's Note: The author invites any comments or questions regarding the FDT via email (see address in bio).

References

1. Zhang A, Chauvin B. Denis Classification. Treasure Island, FL: StatPearls Publishing LLC, 2022.
2. Kellett J. Acute soft tissue injuries - a review of the literature. Med Sci Sports Exerc, November 1986;18(5):489-500.
3. Croft A. Foreman S. Whiplash Injuries, The Cervical/Deceleration Syndrome, 2nd Edition. Baltimore, MD: Williams and Wilkins, 1995: pg 455.
4. Cyriax J. Textbook of Orthopaedic Medicine. 8th Edition, Vol. 1. London: W.B. Saunders, 1982: pg 104.
5. Buerger A, Tobis J. Approaches to the Validation of Manipulative Therapy. Springfield, IL: Thomas Books, 1977: pg 300.
6. Cox J. Low Back Pain Mechanism, Diagnosis and Treatment. Baltimore, MD: Lippincott Williams & Wilkins, 1999: pp. 292-293.
7. Croft A. Foreman S. Op cit, pg 469.
8. Evans R. Neurology and Trauma. New York, NY: Oxford University Press, 2006: pg 325.
9. Haldeman S. Principles and Practice of Chiropractic. Norwalk, CT: Appleton & Lange, 1992: pg 565.
10. Rumboldt Z. Clinical Imaging of Spinal Trauma, A Case Based Approach. Cambridge, UK: Cambridge University Press, 2018: pg 37.
11. Evans R. Op cit, pg 310.
12. Rumboldt Z. Op cit, pg 55.
13. Dubin A, Patapoutian A. Nociceptors: the sensors of the pain pathway. J Clin Invest, 2010 Nov 1;120(11):3760-3772.
14. Pain and Nociception.Last reviewed at [url=http://en]http://en[/url]. wikipedia.org/wiki/pain-and-nociception.
15. Croft A, Foreman S. Op cit, pp. 451-454.
16. Rumboldt Z. Op cit, pg 31.
17. White A. Panjabi M. Clinical Biomechanics of the Spine.  Philadelphia, PA: J.B Lippincott Company, 1978: pp. 173-179.
18. White A. Panjabi M. Ibid, pg. 118.
19. Rumboldt Z. Op cit, pg 59.
20. Croft A, Foreman S. Op cit, pg 299.
21. Ibid, pg 332.
22. Goetz L, De Jesus O, Sean M. Posttraumatic Syringomyelia. Treasure Island, FL: StatPearls Publishing, 2022.
23. Collins S. "Billing Flexion-Distraction Services." Dynamic Chiropractic, July 29,2010.