We\u2019ve all been there at some point \u2013 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\u2026 \u201csnap, crackle, pop<\/em>!\u201d 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! <\/p>\n\n\n\n

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.<\/p>\n\n\n\n

This technique is called an HVLAT (high velocity, low amplitude thrust) manipulation. “High velocity” refers to the very short duration (on average 0.158 seconds^{1<\/sup>); whereas “low amplitude” refers to the small range of motion experienced (on average 40o<\/sup> cervical [neck] rotation2<\/sup>). 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”<\/em>) occurs regularly with this technique & in some cases is required for the desired response.  <\/p>\n\n\n\n}

First, we\u2019ll 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.<\/p>\n\n\n\n

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<\/sup><\/p>\n\n\n\n}

Bronfort et al ^{5<\/sup> concluded cervical manipulation to be more effective at reducing headache symptoms than massage therapy & it had a comparable effect to that of pharmaceutical drugs.<\/p>\n\n\n\n}

Lumbar disc herniation with associated radiculopathy symptoms (commonly called \u201csciatica<\/em>\u201d) have been shown to improve with lumbar HVLAT manipulation^{10,11<\/sup>.<\/p>\n\n\n\n}

Several different types of shoulder pain have been shown to improve after a thoracic (upper & middle back) HVLAT manipulation^{12<\/sup>, as well as improvements in shoulder range of motion & function. It has even been found that rib HVLAT manipulations can have similar results13<\/sup>.<\/p>\n\n\n\n}

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 pain^{7<\/sup>.  This is a very exciting finding, especially for treatment options involving patients with complex, chronic, or multifactorial pain patterns.<\/p>\n\n\n\n}

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<\/a>, 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 symptoms^{6<\/sup>. This is where a skilled, well-rounded physical therapist can be invaluable.<\/p>\n\n\n\n}

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.<\/p>\n\n\n\n

Like many progressive, advanced techniques, HVLAT manipulation should be extensively examined for not only merit, but more importantly, for safety.<\/p>\n\n\n\n

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 <\/strong>that the clinician is well qualified, typically a Doctor of Physical Therapy, Doctor of Osteopathy, or Doctor of Chiropractic. <\/p>\n\n\n\n

Now, let\u2019s put into perspective some numbers to better understand the relative safety of this technique.<\/p>\n\n\n\n

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% strain^{8,9<\/sup>. 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!<\/p>\n\n\n\n}

Cassidy et al^{4<\/sup> 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.<\/p>\n\n\n\n}

Ultimately, when performed correctly to an appropriate patient population<\/strong>, 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.   <\/p>\n\n\n\n