Proprioception as a Prerequisite to SG Cell Response in Inhibiting Musculoskeletal Pain Using Manipulation under Anesthesia

This paper represents a hypothesis regarding patient response to spinal manipulation under anesthesia (MUA) and the response to follow-up care after the MUA procedure has been completed. In caring for patients following the spinal MUA procedure, we noticed that the majority of patients were not comfortable lying in the prone position for the after care (post-MUA therapy). After the first few patients described the same discomfort, we began to see that the position the patient assumed after the MUA procedure was significant to after care response and recovery rate. We observed that some of the patients who could never lie in the supine position (because of a high level of discomfort prior to the MUA) prefered the supine or side lying position to the prone position after the MUA procedure. We began to wonder if the position(s) that we took the patient's body through during the MUA procedure had anything to do with the patient's response to post-MUA therapy.

This paper describes our hypothesis, describes the procedure used, and gives some definition to the idea that we may be redirecting higher central nervous center responses to accept body position changes (proprioception) during the MUA procedure. Since body changes or position change (proprioception) also affects SG cell response to inhibit pain (Melzach, Wall, Kirkaldy-Willis), then taking the body through the positioning and stretching that is accomplished during the MUA procedure may have a direct effect on the inhibition of pain that occurs with this procedure.

Key words: proprioception; manipulation; anesthesia; postural kinesthesis.

Scientific Theory

"Pain is a perception rather than a sensation. A person's physical state, past experience, and anticipation all contribute to the way a given stimulus will be interpreted, implying that pain messages can be modified at many levels of the nervous system."¹

The "gate control theory" proposed by Melzach and Wall^2,3,4 identify cellular structures in the substantia gelatinosa in the gray matter of the dorsal horns of the spinal cord, which act as a "gate" that when "open" allows the perception of pain through the reticular formation and thalmus, with response from the limbic system, among others. When the mechanism is stimulated to "close," the gate inhibits the perception of pain. This is a simplistic version of the gate control theory, but it helps to set the foundation for the substance of this paper.

Two types of fibers as identified by Melzach and Wall affect the way pain "gets past, or affects the gate."^3,4 Small fibers (S) affect the "T cell" and act to "open the gate" when noxious stimulation occur. Larger (L) fibers affect the "SG cells" located in the substantia gelatinosa in the gray matter of the dorsal horn to act in response to proprioception and touch during changes in body movement. They inhibit the T cell response and "close the gate." This in theory changes the course of noxious or painful stimuli, and causes a natural analgesic effect. "Inhibition of pain is increased by stimulating the mechanoreceptors (L-fibers) in two ways: by movement and activity of muscles and joints, and by manipulation of the joint."³

Introduction

MUA has been recorded to have been successful as far back as the late '30s by the osteopathic profession. The anesthetics used were not as sophisticated, and the techniques were not what has been considered by recent literature as site specific.^5,6,7 The anatomy and physiology of the motion unit was not well understood,⁷ and the techniques were more general than specific. ^6,8

Manipulation of the spine with the patient under a sedative/hypnotic is one of the most gentle, yet effective, methods of altering chronic fibroadhesive neuromusculoskeletal conditions, and as articular disrelationships and disc abnormalities. For years chiropractic physicians have been limited to the care that they are able to render to the patient in the therapeutic environment of the office. If the standard adjustive or physiotherapeutic care was ineffective, the doctor had only one recourse: refer out for either drug therapy or other allopathic intervention to help relieve the patient's discomfort.⁹

The purpose of using MUA is to provide mobilization, manipulations and adjustments of the spinal motion units and the surrounding soft tissue in an atmosphere where there is a decrease in muscle splinting and contracture and where the patient loses their apprehension to the maneuver.^10,11,12 It is also used because the patient is more responsive to the manipulative procedure than they could be in the office setting. When used on the properly selected patients, it is more cost effective and more productive to the patient's return to a normal lifestyle than prolonged conservative care or surgical intervention.^5,8

The chiropractic physician who has been trained in the proper postgraduate certification course in MUA is able to take chiropractic therapy with all the specificity of these maneuvers into the operating room, make significant changes in the level of the patient's pain and discomfort, and as described below, also make corrections in biomechanical disrelationships which affect the way the patient responds and perceives discomfort.^13,14

The techniques have been refined over the years. Specific maneuvers can be accomplished to re-establish much of the integrity of the involved joint(s) and accommodate physiological and biomechanical reintegrated or postural kinesthetic^13,14 integration of the elements of the articulations and the surrounding soft tissue.

Protocols for this procedure¹⁰ demand that the highest standards of chiropractic care be rendered before placing the patient into the MUA program. This period depends on patient response to conservative care, progression of the normal healing phase, and the patient's ability to function in normal daily activity. As a standard, the conservative period varies from two weeks in acute cases, with medical intervention, to between 4-6 weeks with little or no patient improvement in conservative office therapy. ^10,15

Standard parameters for determining if a patient's condition is treatable by chiropractic care is the predominant first step toward whether the patient would ever become an MUA candidate. MUA is very much a chiropractic procedure except it is done in a different environment. The same protocols for determining the patient's status as a chiropractic patient are adhered to as far as consultation, examination, diagnostic testing, and reaching a diagnostic conclusion from which to base standard conservative care.¹⁰

The techniques are relatively the same no matter what chiropractic college teaches the course, however, not all chiropractic colleges teach MUA. Of those that do, the postgraduate faculty usually teach the basic maneuvers that have been passed down over the years, but add additional specifics which may be individual to that faculty member. This procedure has many facets, and can be accommodating to many types of conditions which have been shown to respond to MUA. This paper will not be specific for the indications or contraindications for MUA. These areas are described in the literature, and have been mentioned in numerous articles over the years. The most important fact that we want to relate in this paper is that this procedure is not complete without the continuation of post-MUA therapy. It is the post-MUA therapy following the specific MUA procedure and the patient positioning that this paper is concerned with. It is this area of the total procedure that we would like to address.

To fully understand the importance of the patient positioning during post-MUA therapy, it is important that the MUA procedure be described. "No amount of experience in the office will qualify a physician for manipulation of the patient under a general anesthetic. No hospital should permit the physician to perform such manipulation until he has been observed and has received supervision and the approval of an experienced operator who himself has been previously approved by certification and hospital proficiency standards" (Siehl, D.1952).¹⁶ This procedure as described is taught by Robert Gordon,DC, postgraduate faculty, National College of Chiropractic.¹⁰ This is just one instructor's approach to full spine MUA. Each case must be treated individually and requires variation in the full spine procedure to initiate the best results for a specific condition. The "basic" procedure gives the practitioner a base to start to cover all areas if full spine MUA is completed and a technique source to choose from if only portions of the full procedure are needed.

The Procedure The patient is draped in the appropriate gowning and is taken by gurney to the operative area and asked to lie supine on the operative table. The patient is placed on the appropriate monitors for this procedure. When the patient and doctor are ready, the anesthesiologist will administer the appropriate medications to assist the patient into twilight sedation using medications which allow the stretching, mobilization and adjustments necessary for the completion of the outcome the doctor desires.

The Cervical Spine

With the patient in the supine position on the operative table, the upper extremities are flexed at the elbow and crossed over the patient's chest to achieve maximum traction to the patient's thoracic spine. The first assistant holds the patient's arms in the proper position and assists in rolling the patient for the adjustive procedure. With the help of the first assist, the patient is rolled on the right side, selection is made for the contact point, and the patient is rolled back over the doctor's hand. The elastic barrier of resistance is found and a low velocity thrust is achieved using a specific closed reduction anterior to posterior/superior manipulative procedure.

The Lumbar Spine

With the patient supine on the procedure table, the primary physician addresses the patient's lower extremities, which are elevated alternatively in a straight leg raising manner (approximately 90 degrees from the horizontal). Linear force is used to increase the hip flexion gradually during this maneuver. Simultaneously, the first assisting physician applies a myofascial release technique to the calf and posterior thigh musculature. Each lower extremity is independently bent at the knee and tractioned cephelad in a neutral saggital plane, lateral oblique cephelad traction, and medical oblique cephelad traction maneuver. The primary physician then approximates the opposite single knee from the patient's position from neutral to medial slightly beyond the elastic barrier of resistance. (A piriformis myofascial release may be accomplished at this time.) This is repeated with the opposite lower extremity. Following this, a Patrick-Fabere maneuver is performed up to and slightly beyond the elastic barrier of resistance.

With the assisting physician stabilizing the pelvis and femoral head (as necessary), the primary physician extends the right lower extremity in the saggital plane, and while applying controlled traction, gradually stretches the para-articular holding elements of the right hip by means of gradually describing an approximately 30-35 degree horizontal arc. The lower extremity is then tractioned straight caudad and internal rotation is accomplished. Using traction, the lower extremity is gradually stretched into a horizontal arch to approximately 30 degrees. This procedure is then repeated using external rotation to stretch the para-articular holding elements of the hips bilaterally. These procedures are then repeated on the opposite lower extremity.

By approximating the patient's knees to the abdomen in a knee-chest fashion (ankles crossed), the lumbopelvic musculature is stretched in the saggital plane by both the primary and first assistant, contacting the base of the sacrum and raising the lower torso cephalad. This results in passive flexion of the entire lumbar spine and its holding elements beyond the elastic barrier of resistance. With the patient's lower extremities kept in hip/knee flexion, the patient's torso is secured by the first assistant. The lumbar fasciae/musculature is elongated obliquely to the right of mid-line, in a controlled manner up to and beyond the elastic barrier of resistance. (Cavitation may be noted.) This is repeated on the opposite side.

With the use of the undersheets, the patient is carefully placed in the left/right decubitus position and positioned so that the lumbar spine overlays the kidney plate to the point where the lumbar spine attains the horizontal and is derotated to avoid facet imbrication. The patient's body is stabilized by the first assistant. The knee and hip of the upper leg is flexed and the lower leg stabilized in the extended position by the first assist. Segmental localization of the appropriate lumbar motion-units is made by the primary physician and the elastic barrier of resistance found. A low-velocity impulse-thrust is applied and achieves cavitation. (The PSIS is then adjusted on the opposite side with the patient in the same position as above.)

The patient is then repositioned supine by means of the undersheets. With appropriate assistance, the patient is transferred from the procedure table to the gurney and is returned to the recovery room, where appropriate monitoring equipment monitors vital signs. The IV is maintained until the patient is fully alert and stable. The patient is then transferred to a sitting recovery position and given fluids and a light snack. Following this, the patient is discharged with appropriate home instructions.¹⁷

Discussion

The MUA procedure is about 65-70% mobilization and stretching, and about 30-40% articular adjustment. The patients are taken through a variety of movements to alter adhesions, stretch muscles that have been shortened due to disuse, and provide increased range of motion to joints, and joint capsules which have become hypomobile and fixated.

Literature suggests that an altered adhesion reforms again in approximately 24-48 hours.^18,19,20,21 There is immediate follow- up post MUA therapy to prevent the reformation of the adhesions and to continue the flexibility and motion in the fixated joints and surrounding soft tissue structures.

We have observed that if the patient is treated with post-therapeutic MUA techniques in the same body positions (supine and side posture) that were used during the procedure, the response to the procedure, the post-MUA therapy, and the follow-up results are considerably better than if the patient is placed back in the usual prone position for office therapy. This phenomena only seems to be a factor for the first 3-5 days following MUA, but does have a significant affect on the patient's comfort and recuperation time.

Since we see a considerable change in pain perception in more than 80-90% of the MUA cases which have been completed in the U.S.^22,23,24 We suspect that if a proprioceptive response to body positions is occurring, it may be affecting the SG cells in the substantia gelatinosa causing an inhibitory response to pain and "closing the gateway" to higher CNS pain perception centers. Reasonable review of the effects of the usual medications given for this procedure -- propofol (Deprivan) -- also indicates that this medication is only responsive for the time it is being titered and is metabolized within about eight hours. Since that would lead one to believe that this medication was responsible for the patient response to post-MUA therapy, we ask why would body position recognized consciously post-MUA be so definitive in making the patient comfortable if not for proprioceptive change occurring as part of the procedure?

Inhibition of pain from proprioceptive response to body position change for years has been a theory for decreased discomfort after the use of manipulation.^25,26,27

Wyke²⁵ specifically describes what he calls "postural kinesthesis" as being a resultant phenomenon from the use of manipulation of the spinal articulations relative to his theories that manipulation has a direct affect on nociception Type IV mechanoreceptors, and Type I and Type II articular mechanoreceptors. Since we are enhancing the manipulative values some 10-fold using the MUA technique,²⁷it is certainly within reason to believe that change from proprioception response could be causing the results that we have been seeing with this procedure.

Conclusion

Our review of patient response to position following the MUA procedure was the same whether the procedure was completed on a full-spine format or in specific areas (such as the cervical spine, cervicothoracic spine, thoracolumbar spine, lumbar spine, or lumbopelvic areas). If the patient was kept in the supine position or the side-lying position they responded more rapidly and had considerably less discomfort than if other positions (e.g., prone position) were used for the post-therapy.

Proprioception, whether considered of articular, muscular, tendonous or ligamentus receptor origin, or of position sense from higher center activators, does play a role in changing painful stimuli when the MUA procedure is used. How this occurs and the significance is not fully known, but the authors whom we have referenced certainly lead us to believe that prior studies have indicated that directed body positioning (such as what occurs in MUA) has a great deal to do with changing painful stimuli perception.

Although considerable research needs to continue in this field, the thousands of procedures that have been clinically documented, and the excellent results obtained by these cases cannot be denied as "experimental." When scientific literature confirms most of what we have described in this article, and clinical trial proves it to be observable in 80-90% of the cases we have suggested this procedure for, we must glean substantiation to some degree in using this approach for post-MUA. It is our opinion that if post-MUA therapy is disregarded as only a small portion of the whole of the MUA procedure, then the patient response will not be as great as the doctor would like. It is important to recognize that this procedure is only going to be as good as we make it. If we deny the validity of a procedure that benefits so many people just because we have not completed hundreds of research projects, then we deny our patient the benefits of what we have done and what we are now doing.

We hope this article will bring some new insight to the MUA procedure and the post-MUA therapy and create interest in pursuing more investigation into this procedure. This procedure is here to stay. It's not experimental, if it ever was, and it benefits too many people today to be put on the back burner or denied for third-party discrimination.

References

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