We’ve all been there at some point – trapped on an impromptu YouTube video binge or afternoon infomercial. A practitioner of some kind, typically a chiropractor or physical therapist, holds & gently manipulates the relaxed head & neck of a patient who complains of stiffness & pain. You wait in anticipation for 2-3 seconds, then… “snap, crackle, pop!” The patient sits up from the treatment table with a look of both satisfaction & surprise & rotates their head fully left, right, up, down, pain-free!
So, what exactly happened? Although there have been many proposed explanations of spinal manipulation (some quite contentiously argued), this article will discuss its researched, evidence-based purpose, effectiveness & safety.
This technique is called an HVLAT (high velocity, low amplitude thrust) manipulation. “High velocity” refers to the very short duration (on average 0.158 seconds1); whereas “low amplitude” refers to the small range of motion experienced (on average 40o cervical [neck] rotation2). Because of the high velocity & low amplitude nature of the thrust, very little force is required to achieve a productive manipulation, allowing for very low risk. A popping, clicking, or cracking phenomenon (called “cavitation”) occurs regularly with this technique & in some cases is required for the desired response.
First, we’ll dive into the literature that describes the effectiveness of HVLAT spinal manipulation. There are many studies that show that spinal manipulation (lumbar, thoracic, cervical) can be quite effective for a variety of pathologies.
In people with neck pain, disability, motor deficits & range of motion limitations, a single session of cervical and thoracic (mid-back) HVLAT manipulation has been shown to be more effective than a more conservative, non-thrust mobilization.1
Bronfort et al 5 concluded cervical manipulation to be more effective at reducing headache symptoms than massage therapy & it had a comparable effect to that of pharmaceutical drugs.
Lumbar disc herniation with associated radiculopathy symptoms (commonly called “sciatica”) have been shown to improve with lumbar HVLAT manipulation10,11.
Several different types of shoulder pain have been shown to improve after a thoracic (upper & middle back) HVLAT manipulation12, as well as improvements in shoulder range of motion & function. It has even been found that rib HVLAT manipulations can have similar results13.
Most interestingly, in my humble (or nerdy!) opinion, is that HVLAT manipulation has been shown to augment incoming signals to the central nervous system (brain and spinal cord), thereby reducing pain pathways! For people experiencing long term pain due to hyperexcitable neurons, HVLAT manipulation may actually reduce their overall perception of pain7. This is a very exciting finding, especially for treatment options involving patients with complex, chronic, or multifactorial pain patterns.
Although HVLAT spinal manipulation has proven to be a powerful intervention for pain, disability, range of motion, headaches & motor (muscle) performance, like many other interventions, it will likely be much more effective if coupled with other interventions or modalities (i.e. dry needling, soft tissue manipulation, therapeutic exercise, etc.). In many cases a patient would benefit further from a combination of HVLAT manipulation with a therapeutic/corrective exercise prescription, especially to reduce chronic symptoms6. This is where a skilled, well-rounded physical therapist can be invaluable.
Just as it is important to manipulate the appropriate patient, it is also as important to NOT manipulate the inappropriate patient. Like many practices, there are intrinsic limitations to HVLAT manipulative therapy. Specific contraindications exist in certain populations. Individuals with osteoporosis, a history of CVA (stroke), uncontrolled hypertension, suspicion of bone fracture, or a poor patient/doctor rapport generally would be inappropriate for this technique, & potentially, this technique could actually be dangerous.
Like many progressive, advanced techniques, HVLAT manipulation should be extensively examined for not only merit, but more importantly, for safety.
A big concern for many people is the stress/strain a cervical manipulation may cause on the vertebral artery (the artery supplying blood to the brain & spine). Historically, when performed incorrectly to an inappropriate patient, this is the artery that, if damaged, could cause stroke. For this reason, it is imperative that the clinician is well qualified, typically a Doctor of Physical Therapy, Doctor of Osteopathy, or Doctor of Chiropractic.
Now, let’s put into perspective some numbers to better understand the relative safety of this technique.
During passive rotation (comfortably rotating the head to the left or right…which we all do multiple times every day), the vertebral arteries experience up to 12.5% strain. During HVLAT cervical manipulation, these arteries experience far less strain (6.2%). It is important to understand that these arteries do not undergo mechanical failure (damage) until they reach 139-162% strain8,9. These results demonstrate the remarkably low strain levels a cervical HVLAT manipulation produces; in many cases the strain created by HVLAT manipulation is significantly lower than simply rotating your neck comfortably to the side!
Cassidy et al4 describe the limited risk associated with HVLAT spinal manipulations & interestingly even went as far as to conclude there to be no greater risk of vertebrobasilar artery (VBA) stroke with cervical HVLAT manipulation than with a standard general practitioner (family doctor) medical visit.
Ultimately, when performed correctly to an appropriate patient population, cervical HVLAT manipulation proves to be quite safe & an effective option to treat a wide array of pathology from discomfort & stiffness to headaches & chronic pain.
Interested in more info about HVLAT manipulation? Feel free to contact Jerrod at 208-375-5511 or email. For more about Jerrod, visit Jerrod Ackerman (rockandarmor.com).
1. Ngan JM, Chow DH, Holmes AD: The kinematics and intra- and inter-therapist consistencies of lower cervical rotational manipulation. Med Eng Phys. 2005, 27 (5): 395-401. 10.1016/j.medengphy.2004.10.009
2. Triano J, Schultz AB. Loads transmitted during lumbosacral spinal manipulative therapy. Spine 1997;22(17):1955–64.
3. Dunning J, Cleland J, Waldrop M, Arnot C, Young I, Turner M, Sigurdsson G. Upper Cervical and Upper Thoracic Thrust Manipulation Versus Nonthrust Mobilization with Patients with Mechanical Neck Pain : A Multicenter Randomized Clinical Trial
4. Cassidy JD, Boyle E, Cote P, He Y, Hogg-Johnson S, Silver FL, Bondy SJ. Risk of vertebrobasilar stroke and chiropractic care: results of a population-based case–control and case-crossover study. Spine (Phila Pa 1976) 2008;33(4):S176–S183
5. Bronfort G, Assendelft WJ, Evans R, Haas M, Bouter L. Efficacy of spinal manipulation for chronic headache: a systematic review. J Manipulative Physiol Ther. 2001 Sep;24(7):457-66. PMID: 11562654.
6. Gross et al. Spinal manipulative therapy (SMT) for neck pain and associated disorders in adults. 2014 Evidence-Based Guidelines
7. Boal RW, Gillette RG. Central neuronal plasticity, low back pain and spinal manipulative therapy. J Manipulative Physiol Ther. 2004 Jun;27(5):314-26. doi: 10.1016/j.jmpt.2004.04.005. PMID: 15195039.
8. Symons BP, Leonard T, Herzog W. Internal forces sustained by the vertebral artery during spinal manipulative therapy. J Manipulative Physiol Ther. 2002 Oct;25(8):504-10. doi: 10.1067/mmt.2002.127076. PMID: 12381972.
9. Symons B, Herzog W. Cervical artery dissection: a biomechanical perspective. J Can Chiropr Assoc. 2013;57(4):276-278.
10. Hahne, Andrew J. BPhysio*; Ford, Jon J. PhD*; McMeeken, Joan M. MSc† Conservative Management of Lumbar Disc Herniation With Associated Radiculopathy, Spine: May 15, 2010 – Volume 35 – Issue 11 – p E488-E504 doi: 10.1097/BRS.0b013e3181cc3f56
11. Oliphant D. Safety of Spinal Manipulation in the Treatment of Lumbar Disk Herniations: A Systematic Review and Risk Assessment. Journal of Manipulative and Physiologic Therapeutics: Volume 27, Issue 3
12. Derrick G Sueki & Eric J Chaconas (2011) The effect of thoracic manipulation on shoulder pain: a regional interdependence model, Physical Therapy Reviews, 16:5, 399-408, DOI: 10.1179/1743288X11Y.0000000045
13. Joseph B. Strunce, Michael J. Walker, Robert E. Boyles & Brian A. Young (2009) The Immediate Effects of Thoracic Spine and Rib Manipulation on Subjects with Primary Complaints of Shoulder Pain, Journal of Manual & Manipulative Therapy, 17:4, 230-236, DOI: 10.1179/106698109791352102