The claimant has the burden of proving all the essential elements of the claim for compensation. Proof as to medical causation need not be by absolute certainty, but rather by a reasonable probability. "Probable" means founded on reason and experience which inclines the mind to believe but leaves room for doubt. Tate v. Southwestern Bell Telephone Co., 715 S.W.2d 326, 329 (Mo.App. 1986).
"Medical causation, not within the common knowledge or experience, must be established by scientific or medical evidence showing the cause and effect relationship between the complained of condition and the asserted cause". Brundige v. Boehringer Ingelheim, 812 S.W. 2d 200, 202 (Mo.App. 1991); McGrath v. Satellite Sprinkler Systems, Inc., 877 S.W.2d 704, 708 (Mo.App. E.D. 1994). The ultimate importance of expert testimony is to be determined from the testimony as a whole and less than direct statements of reasonable medical certainty will be sufficient. Choate v. Lily Tulip, Inc., 809 S.W. 2d 102, 105 (Mo.App.1991).
Effective August 28, 2005, SB 1 \& 130 changed the standard for determining whether an injury by traumatic event, cumulative trauma, or disease process was sufficiently work related as to come under the provisions of the workers' compensation act. In Lawson v. Ford Motor Co., 217 S.W.3d 345 (Mo.App. E.D., 2007), at pp. 348-349, the court notes as follows with respect to the change in the legal standard:
As Ford correctly notes, in 2005 the legislature amended several sections of the Workers' Compensation Act. In particular, portions of section $\underline{287.067} and \underline{287.020}$ were rewritten. Specifically, section 287.067 .2 discusses when an injury by occupational disease
is considered compensable. Prior to 2005, the section stated that such an injury will be compensable if it "is clearly work related and meets the requirements of an injury which is compensable as provided in subsections 2 and 3 of section 287.020 ."
Subsections 2 and 3 of section 287.020 previously contained definitions for "accident" and "injury." Prior to 2005, those definitions included language which concluded that an injury was compensable if it is work related, which occurs *349 if work was a "substantial factor" in the cause of the disability.
As Ford correctly notes, in 2005 the legislature amended several sections of the Workers' Compensation Act. In particular, portions of section 287.067 and 287.020 were rewritten. Specifically, section 287.067.2 discusses when an injury by occupational disease is considered compensable. Prior to 2005, the section stated that such an injury will be compensable if it "is clearly work related and meets the requirements of an injury which is compensable as provided in subsections 2 and 3 of section 287.020." Subsections 2 and 3 of section 287.020 previously contained definitions for "accident" and "injury." Prior to 2005, those definitions included language which concluded that an injury was compensable if it is work related, which occurs *349 if work was a "substantial factor" in the cause of the disability.
After the 2005 amendments to the statutes, the definition of a compensable injury by occupational disease was changed to use the language "prevailing factor" in relation to causation. Specifically, section 287.067 .2 states:
An injury by occupational disease is compensable only if the occupational exposure was the prevailing factor in causing both the resulting medical condition and disability. The 'prevailing factor' is defined to be the primary factor, in relation to any other factor, causing both the resulting medical condition and disability. Ordinary, gradual deterioration, or progressive degeneration of the body caused by aging or by the normal activities of day-to-day living shall not be compensable.
Section 287.020.3 defines "injury" using similar terms.
Section 287.808 RSMo. Cum. Supp. 2008 provides that "The burden of establishing any affirmative defense is on the employer. The burden of proving an entitlement to compensation under this chapter is on the employee or dependent. In asserting any claim or defense based on a factual proposition, the party asserting such claim or defense must establish that such proposition is more likely to be true than not true." Further, Section 287.800 RSMo. Cum. Supp. 2008 provides as follows:
- Administrative law judges, associate administrative law judges, legal advisors, the labor and industrial relations commission, the division of workers' compensation, and any reviewing courts shall construe the provisions of this chapter strictly.
- Administrative law judges, associate administrative law judges, legal advisors, the labor and industrial relations commission, and the division of workers' compensation shall weigh the evidence impartially without giving the benefit of the doubt to any party when weighing evidence and resolving factual conflicts.
Dr. Schlafly concludes that the claimant's repetitive use of her hands to serve food and to perform her waitress duties was the prevailing factor in the resultant condition known as bilateral carpal tunnel syndrome. To the contrary, Dr. Brown concludes that the job description provided by Ms. Reale and his own understanding generally as to the repetitive nature of the duties of a waitress lead him to believe that her work as a waitress for the employer was not the prevailing or primary causative factor with regard to the carpal tunnel syndrome. Dr. Brown acknowledges that in the past he has had the occasion to conclude that work performed while waitressing can be a contributing factor to the development of carpal tunnel. In response to the question whether waitressing can be an occupational risk factor, he states "It's possible. I've rendered
opinions in cases where a waitress, a busy waitress over a long period of time --- it's possible that could be a contributing factor to symptoms or carpal tunnel syndrome. But in this case, I think it's clear it's not the most important factor." (Employer and Insurer's Exhibit No. 5, at p. 25).
Dr. Brown notes that he weighs both occupational and non-occupational risk factors on a case by case basis when determining causation with respect to a carpal tunnel diagnosis. With regard to Ms. Reale, Dr. Brown identifies four non-occupational risk factors that he believes to be involved in the analysis as to causation, and ranks them in the following order of importance: 1) increased body mass index; 2) osteoarthritis of the base of the thumbs; 3) age; and 4) female gender. Dr. Brown cites various empirical studies in The Journal of Hand Surgery that he believes to be authoritative, and cites those studies in support of his conclusion as to the relative importance of the nonoccupational risk factors. In sum, Dr. Brown affirms that repetitive flexion of the wrists while carrying food trays can be a cause of carpal tunnel syndrome. However, based on his understanding of the nonoccupational risk factors involved, and given his understanding of the frequency and extent of the use of the upper extremities by Ms. Reale in the course of a work day, he concludes that work is a possible causative factor but not the most important factor.
As a part of his conclusion as to causation Dr. Schlafly was able to rule out hand intensive hobbies and diabetes as possible nonoccupational risk factors. He acknowledges that carpal tunnel syndrome is statistically more common in females 40 to 60 years old (Ms. Reale was 52 years old as of her last day of work as a waitress for the employer). Dr. Schlafly further notes that he does not consider The Journal of Hand Surgery to be authoritative; that he is aware of studies as to body mass index and carpal tunnel syndrome; and that he has no opinion on the theory that there is a causal association between obesity and carpal tunnel syndrome. Dr. Schlafly acknowledges that osteoarthritis at the base of the thumb and carpal tunnel syndrome are fairly common and coexist; acknowledges that there is medical literature that suggests a possible causal connection between the two; and agrees that it is possible that there could be some causal connection between carpal tunnel, osteoarthritis at the base of the thumb, or some third factor causing both. Dr. Schlafly did not have the opportunity to review the x-rays of the hands performed by Dr. Brown; was not aware of the diagnosis of osteoarthritis of the base of the thumbs at the trapeziometacarpal joints; and was not asked to render any opinion as to the significance, if any, of such a finding.
The claimant is obliged to show that cumulative trauma suffered to the right and left wrists while performing her duties at the Falcon Diner was the prevailing factor in causing the bilateral carpal tunnel syndrome. The "prevailing factor" is defined to be the primary factor, in relation to any other factor, causing both the resulting medical condition and disability, Section 287.067.3 RSMo.
Drs. Schlafly and Brown disagree as to whether the work performed by Ms. Reale was the prevailing factor. Where the opinions of medical experts are in conflict, the fact finding body determines whose opinion is the most credible. Hawkins v. Emerson Electric Co., 676 S.W.2d 872, 877 (Mo. App.1984). "A medical expert's opinion must be supported by facts and reasons proven by competent evidence that will give the opinion probative force to be substantial evidence." Silman v. Montgomery \& Associates, 891 S.W.2d 173, 176 (Mo. App. 1995); Pippin v. St. Joe Minerals Corp., 799 S.W.2d 898, 903 (Mo. App. 1990).
At issue, then, is whether the opinion of Dr. Schlafly or of Dr. Brown is the most persuasive on the question whether the claimant's work as a waitress was sufficiently repetitive
to be deemed the primary factor in the development of a disabling bilateral carpal tunnel syndrome.
Dr. Schlafly was impressed that the claimant's use of her hands at work was sufficiently repetitive as to be the primary cause of her carpal tunnel syndrome, whereas Dr. Brown was not. The apparent difference is in the perceptions of the two physicians as to the nature of the repetitive use involved in the waitressing performed by Ms. Reale, and the relative weight to be given to nonoccupational factors. Dr. Brown acknowledges that he has rendered past opinions where he believed that busy waitressing over a long period of time could be a contributing factor to carpal tunnel syndrome, yet frames his opinion by describing waitressing as having busy and slow times, and by distinguishing waitressing from assembly line type of jobs that require constant and repetitive hand and wrist activity without rest intervals. Dr. Brown does not dispute the possibility of a causal relationship; he concludes that given the various nonoccupational risk factors, he is confident to state that work was not the prevailing factor.
Ms. Reale testified that she was always busy at work, serving the breakfast and lunch crowd from 6:00 a.m. to 2:00 p.m.; working six to twelve tables, with anywhere from two to 10 or as many as 15 people to a table; and staying busy during some of the down time by restocking the glass racks. Ms. Reale was the only witness to provide testimony as to the nature of her waitressing duties and the degree to which she was kept busy serving, cleaning tables, and restocking glass racks. Ms. Wojtulski, an associate manager, testified on behalf of the employer, and the entire focus of her testimony was on the circumstances surrounding the decision to terminate the employment of the claimant for suspicion of manipulating coupons, and on the question whether prior to her termination Ms. Reale had ever mentioned to Ms. Wojtulski her diagnosis of carpal tunnel syndrome.
The testimony of Dr. Schlafly as to causal relationship is found to be consistent with the claimant's work history of repetitive use of the hands over a long period of time while employed by Ameristar Casino as a waitress, and is deemed worthy of belief. The testimony of Dr. Brown as to the import of nonoccupational risk factors merits consideration, but fails to persuade in this matter. The claimant is found to have shown, as a matter of a reasonable degree of probability, that repetitive use of her upper extremities as a waitress was the prevailing factor in causing her bilateral carpal tunnel syndrome, disability, and need for treatment. The issues as to medical causation and injury by occupational disease arising out of and in the course of employment are found in favor of the claimant, Ms. Reale.