In the last issue of Neuromechanical News I listed the various tests and procedures that we teach to determine the presence of a sacroiliac subluxation. One of the tests was hip extension. This article will attempt to demonstrate how a decrease in hip extension is related to a sacroiliac subluxation.
As those of you who have been to an Impulse Technique seminar will recall, the context of the hip extension test is the “Prone Hip Extension Test,” also known as the “Sacral Cup Test,” as described in the work by Dr. Major Bertrand DeJarnette. Dr. DeJarnette was the founder of the Sacral-Occipital Technique and began his extensive writing, publishing, and teaching career in 1935 with Sacro-Occipital Therapy.
Dr. DeJarnette’s “sacral cup test” was a test he devised to determine if the sacroiliac joint was adversely affecting hip extension on that side. The patient’s pelvis was
stabilized to prevent pelvic rotation (by laying prone on a table with the examiner applying a downward pressure on the posterior aspect of the pelvis). The patient was told to lift one thigh and knee off the table as high as possible, lower it, and then repeat on the contralateral side. The side with reduced height of the leg off the table was said to have less hip extension than the other side. Dr. DeJarnette then had the doctor locate the “superior” and “inferior sacral cups” of the patient’s sacroiliac joints. He described these “cups” as depressions in the sacroiliac joint. The doctor would then apply digital pressure into the “superior cup” of the sacroiliac joint of the restricted hip and have the patient re-perform the hip extension movement. If this did not improve the degree of hip extension, the doctor would next apply digital pressure into the “inferior cup.”
If this increased the hip extension, then the “cup” was treated by applying a doublethumb thrust into it. If the pressure into the “superior cup” had increased the hip extension rather than the “inferior cup,” then the superior cup would have been treated.
What happened when digital pressure was applied into the “cup” that improved the hip extension? We can assume that the affected sacroiliac joint was the cause of the reduced hip extension, but the mechanism that improved it is difficult to understand. Did the digital pressure “correct” the SI subluxation and “allow” the hip to extend further?
Did the digital pressure increase the strength of the hip extensors without affecting the SI subluxation? Was there even an SI subluxation in the first place? Did the digital pressure affect the mechanoreceptors in the SI ligaments thereby producing a neurological improvement in muscle function? We do have some insight as to what Dr. DeJarnette thought as he stated that the pressure increased the strength of the hip extensors, so he must have believed that there was a connection between the SI joint, it ligaments, and the strength of the hip extensors.
To understand this better, let’s consider both the SI joint and the hip joint. Checking many orthopedic books found that the general consensus was that the hip joint allowed up to 30 degrees of extension. And during hip extension there was a combination of pelvic rotation of the ilium into an anterior tilt about the frontal axis in the sagittal plane on the side of the hip being extended; a backward (posterior) rotation of the pelvis on the hip extension side about the vertical axis in the transverse plane; and an elevation of the pelvis on the hip extension side about the sagittal axis in the frontal plane. The opposite side of the pelvis moved about the same axes in the same planes, but in the opposite directions. Thus the 30 degrees of extension was not a pure 30 degrees in the hip socket but rather a composite of many motions. If the pelvis were to be rigidly “locked” down, true hip extension would be less.
But now comes the controversial part. The literature states that the SI joint is very rigid and allows only a degree or two of motion. Most chiropractors are taught that when there is a sacroiliac subluxation the sacrum has subluxated relative to the ilium or that the ilium has subluxated relative to the sacrum, and the treatment is to adjust the subluxated bone (which ever it is) “back” to its “correct” position with the other bone. This is thought to reduce the subluxation and “unlocks” or “freesup”
normal movement within the SI joint. However, since the degree of movement within the SI joint is so small, it is hard to see how “correction” of the SI joint would allow the usually large increase in hip extension seen after the SI adjustment. It has to be more than just an increase of the range of motion within the SI joint from the adjustment.
Tullberg et al, through the use of stereophotogrammetric analysis, showed that manipulation of the SI joint did not alter the position of the sacrum relative to the ilium. So the belief that the sacrum and ilium were “out of position” relative to each and that the adjustment moved the “out of place” bone back into “place” looks doubtful. He further stated that the manipulation improved clinical findings and that something happened, but it “wasn’t a detectable positional change between the sacrum and the ilium.” Could it be that the reduced hip extension was the more the product of a weak or inhibited gluteus maximus muscle than a sacrum or ilium “out of place”?
Dr. Colloca founded Neuromechanical Innovations over a decade ago. He was convinced through various studies that he came across that the “real” effect of an adjustment was the neurophysiological changes produced when a mechanical force was applied to a joint or tissues related to the joint – hence the two-part
name – Neuro and Mechanical. The “function” of a joint is improved when appropriate mechanical stimulation is applied to it, and this “function” may be an increase in range of motion (that we see so obviously in the cervical spine, shoulder joint, and other areas after an Impulse adjustment) or an increase in the strength of the muscles related to that joint without much of an actual increase in the joint’s range of motion. The work by Dr. Moshe Solomonow found that the ligaments inside and around a joint are “desensitized” when a joint has been traumatized (either through the high forcefast acceleration force of an injury or the low forceslow acceleration stress typical of faulty posture – either way, the joint is said to be “subluxated”). They then fail to “signal” the nervous system to activate supporting and stabilizing muscles when the joint is moved or stressed.
Research by Hungerford and Bruno & Bagust showed that pain in the SI joint inhibited the gluteus maximus (while exciting the QL and lateral hamstring) (referred to in the literature as arthrogenic muscle inhibition). It appears that manipulation of the SI joint reduces the inhibition of the gluteus maximus making it more effective in producing hip extension. And it appears that this “manipulation” can be as minimal as a “doublethumb thrust.”
Research by Keller and Colloca demonstrated that when an acceleration force is applied to a bone, the bone “oscillated” at a certain frequency. This means that it moved in a direction away from the force but then “rebounded” back. This back and forth oscillation continued until the movement dampened and ceased (usually within 75 milliseconds). This would explain why stereophotogrammetric analysis did not show a change in the positions of the bones comprising the SI joint. Colloca et al also showed that spinal manipulative thrusts resulted in positive EMG and compound action potentials in the muscles neurologically related to the area being manipulated. Additional research by these authors demonstrated a 21% increase in erector spinae muscle sEMG output following a mechanical force spinal manipulation. This shows that the adjustment reduced the muscle inhibition (increased electrical activity within the muscle).
In conclusion, the advent of more sophisticated research equipment has shown that the adjustment is probably more of a “resetting” of the neurological system than the “repositioning” of bones “out of place.” This seems to be the result of the stimulation of the many types of proprio and mechanoreceptors residing within the joint sending impulses along the afferent fibers to the spinal cord to produce reflex changes. The quality and quantity of these impulses is directly related to the speed and frequency of the thrust being administered. Multiple thrusts create a compounding effect for a stronger result. The Impulse iQ instrument maximizes the beneficial effects by continually “reassessing” the motion pattern of the joint during the repetitive thrusts and speeding up to match the new motion pattern. Once the joint has achieved maximum acceleration the instrument shuts off automatically and emits a single beep.
If you have not experienced or adjusted with the Impulse iQ instrument, be sure to attend a seminar soon and “feel” the difference.