Don Harrison received his B.S. (Mathematics) from the University of Washington in 1968, his M.S. (Mathematics) from the University of Texas at El Paso in 1971, a Secondary Teaching Certificate in education from Western Washington State University in 1973, and his DC degree from Western States Chiropractic College in 1979. He received his M.S.E. (Mechanical Engineering) in 1997 and his Ph.D. (Mathematics) in 1998, both from the University of Alabama in Huntsville. He has taught mathematics in junior high, high school, two community colleges in Washington and Oregon, and at Washington State University. He had private practices in Sunnyvale, California and Evanston, Wyoming from 1979-1993. He originated CBP® Technique in 1980 and is the author of two CBP® text books, a CBP® x-ray workbook, and more than thirty articles in peer-reviewed indexed journals.

AJCC Jan 2000

 Blue Cross Blue Shield of Alabama Attempts to Redefine Mechanical Traction

In December 1999, Blue Cross Blue Shield of Alabama (BCBS) sent out a new description of “mechanical traction” in their form BS 99-17, dated December 1999. They are attempting to limit chiropractors using “CPT Code 97012 Mechanical Traction and CPT Code 97140 Manual Therapy Techniques”. Prior to January 2000, BCBS did not allow chiropractors to file for services using the new CPT code 97140 (manual therapy techniques), which was originated in January 1999. Effective January 1, 2000, Alabama DCs are allowed to use this code with restrictions expressed by BCBS in their form letter (BS 99-17) to all Alabama chiropractors. Since BCBS ideas often filter down to other insurance companies in all states, I have elected to respond in this column to their arbitrary description of “mechanical traction” in the above mentioned form letter.

The BCBS definition of “mechanical traction” shows their complete ignorance of mechanical engineering definitions and principles.

From their form letter (BS 99-17), their definition is “Mechanical traction is defined as the application of a mechanical force to the body in a way that separates or attempts to separate the joint surfaces and elongate the surrounding soft tissues.”  “Spinal traction is used to distract joint surfaces and stretch soft tissues.” “ Joint distraction is defined as the separation of two articular surfaces perpendicular to the plane of the articulation.”

After providing the above definition, the BCBS December 1999 (BS 99-17) letter proceeds to state what BCBS considers the “appropriate” forces to “separate the vertebrae”.

 With BCBS’s purpose in mind (to eliminate procedures & charges to maximize their profits), let’s investigate the actual definition of traction in the dictionary and in engineering. First, Webster’s defines “traction” as “a pulling force exerted on skeletal structure by means of a special device” and “a state of tension created by such a pulling force”. Webster’s defines “tension” as “the act of stretching” and “the stress resulting from the elongation of an elastic body”.¹

Secondly, in mechanical enginering², “stress” is defined as “force per unit area”. Since force is a vector, stress is a vector. We will use arrows to indicate vectors. Engineers are taught four basic types of loads on structures. The stress vectors can be visualized in these four basic types of loadings applied to structures in Figure 1 below.              

Thirdly, we note that spinal tissues have been shown to be visco-elastic. That is, they have a “sigmoidal” shaped curve in a plot of deformation versus time. From Figure 1, it is noted that each of the four types of load will cause some fibers of a structure to be “elongated” or “in tension” compared to the particular fiber’s normal length.

BCBS believes that the only type of “traction” is “longitudinal” or “axial load”. From Figure 1, we note that their assumption is false. In fact, “3-point bending” (a type of traction that can be considered pure bending or transverse load in Figure 1 depending on the resultant shape of the structure) is used in spinal traction routinely. Figure 2AB illustrate two types of 3-point bending applied in skeletal traction (i.e. one cervical and one lumbar example).

Figure 2.  Three-point bending is applied to the cervical spine in A and the lumbar spine in B. Note that, depending upon the shape of the spinal region (i.e. either circular or not), the stresses will be as in Figure 1C and 1G or Figure 1D and 1H.

Actually, skeletal traction can be applied in all degrees of freedom of each body part. These are known as rotations (Rx,Ry,Rz) and translations (Tx,Ty,Tz) in a 3-D Cartesian coordinate system (x-y-z). In Figure 2, 3-point bending is being used in Rx (flexion/extension, which is considered forward/backward bending).

Figure 3. Supine “Segmental Traction” is “mechanical traction” of the 3-point bending variety. It causes tensile stresses in the anterior spinal region directly above the roller. Note the similarity to transverse loading in Figure 1D and 1H.

If one looks at the inherent stress vectors in Figure 1C/1G and 1D/1H, then it is obvious that this is a type of  “mechanical traction” no matter what BCBS happens to print, send out, and/or believe. If you have a similar difficulty over “mechanical traction” with BCBS or any other third party, I have now provided you with your defense of your terminology and deserved reimbursement.

1.      Webster’s New Collegiate Dictionary. Springfield, Massachusetts: G & C Merriam Company, 1977.

2.      Beer FP, Johnston ER Jr. Mechanics of materials, 2^nd edition. New York: McGraw-Hill, Inc., 1992.

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