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The Biomechanics of Chiropractic Adjustments

by Jul 1, 2022

Home » Chiropractic Student Blog - Florida » The Biomechanics of Chiropractic Adjustments

Here’s a wild concept…you can have a leg length discrepancy when you turn your head to a certain side due to a cervical restriction. Initially, this sounds preposterous, but when you think about it logically, it makes sense. All our muscles work together somewhat in a weaved-appearance so when one vertebra rotates or a muscle becomes overly toned (hypertonic), it causes a cascade of events including tightening of muscles, inflammation, and stiffness. Chiropractic adjustments serve to maintain postural integrity, myotatic reflexes, visceral reflexes, and to restore the structural relationship of the vertebral and pelvic segments. After an adjustment, there should be a return of homeostasis. During an adjustment, a noise (called a cavitation) can sometimes be heard. Cavitations result from mobilization of the facet joint capsules during a spinal manipulation. When you increase the space in a cavity, you increase its volume and reduce the pressure, which allows gases to escape from the joint space.

In our Advanced Manual Therapy Techinques course, taught by Dr. Young, we learned about the Thompson protocol, which analyzes the cervical spine and occiput, the pelvic region, and the SI region. To start, leg checks! With thumbs on heels, forefinger and middle finger splitting the malleoli, you identify if there is a short left by viewing the medial malleoli. For example, your patient (laying prone) has a right leg shorter than the other. If your patient rotates their head to the left and it causes a leg length change, then the patient has a unilateral cervical syndrome (specifically a left rotation restriction). You would then palpate for hypertonicity, tenderness, and restrictions prior to a cervical adjustment on the contralateral side with a single drop of the cervical drop table. In the image, Chris is analyzing Jared’s leg lengths as Jared rotates his head to the right.

Alex Photos

Left: Chris performing a leg length check on Jared.

Center: Negative Derifield: Leg that was short in extension remained short upon flexion resulting in a pelvic adjustment performed with the patient supine.

Right:  Chris assessing Jared’s sacral mobility as Jared raises each leg independently.

Once the adjustment is completed and you have reassessed the leg lengths, you flex the patient’s knees 90 degrees and determine if there is a leg length disparity. For example, if your patient had a right short leg in extension that lengthened during knee flexion, it would be noted as “Positive Derefield” and the PI ilium would need to be adjusted on the side that lengthened.

During the sacral analysis, the patient is prone while the doctor places his/her heel on the patient’s sacral base and applies a posterior-anterior pressure to stabilize the sacrum. The patient then raises each leg straight off the table independently, while the doctor analyzes sacroiliac extension and movement under the hand. If the right leg raised higher than the left leg, then there would be a left sacroiliac extension restriction. The doctor would contact the sacral apex with his/her pisiform while stabilizing the medial PSIS and performing a lateral to medial adjustment torque using the lumbar drop table.

If this blog post confused you, don’t worry….you’ll learn all about it in Tri-6! It can be confusing at first, but with lots of practice, you will manage to complete the whole protocol in under five minutes confidently!

Learn why an in-depth education in extremity adjusting is important here!

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About the Author

Alexandra Simic Hachmann

Alexandra Simic Hachmann

My name is Alexandra Simic Hachmann and I am currently in my 10th trimester of the Doctor of Chiropractic program here at NUHS - Florida. I am officially an intern at the HEC clinic! I have obtained a B.A. in Biology and Biomedical Sciences, as well as a Master of Medical Science degree. While I believe my educational background has helped me succeed in this challenging program, I appreciate all the professors’ efforts in helping us excel and prepare for our careers. As a hands-on visual learner, I am embracing the palpation courses and anatomy labs offered! I am still determining which field in chiropractic I would like to pursue; thus, readers should stick around to discover this with me! I hope to bring insightful content to this blog and demonstrate what student life is like at NUHS in sunny Florida.


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