The employer and insurer appeal from the compensation judge’s decision that the employee sustained a work-related injury and that the injury was a substantial contributing cause of her disability and need for medical care, including surgery.  We affirm in part, as modified, and reverse in part.

The employee was employed by First Student, Inc. [the employer], as a school bus driver.  On January 21, 2011, she allegedly slipped on ice or water on the bus stairs and twisted her back as she caught herself on the railing.  She was working in Kansas at the time, and she did not return to Minnesota until January 29, 2011.  A first report of injury, filed March 30, 2011, indicates that notice of injury was given to the employer on February 7, 2011.  The employer and insurer initially admitted liability for the injury and paid some benefits but at some point thereafter denied that a work injury had occurred.

On February 3, 2011, the employee was seen at Hennepin County Medical Center [HCMC] complaining that she had experienced low back pain for the past two weeks.  She did not report an injury at that time and was diagnosed with back pain of muscular etiology.  She was given Vicodin and released to recuperate on an outpatient basis.

The employee next sought treatment on February 16, 2011, seeing Dr. Nate Harris at HCMC.  Dr. Harris recorded that the employee’s low back pain had started three or four weeks previously when she slipped on ice and twisted wrong trying to maintain her balance.  The employee reported that her pain was worse with prolonged standing or walking and that she had “possible” mild lower extremity weakness.  Examination showed lumbar muscle spasm with no evidence for spinal cord involvement.  Dr. Harris treated the employee with muscle relaxants and encouraged “activity as tolerated.”  He noted that the employee might need further imaging or physical therapy if she did not improve in a few weeks, and he told the employee to follow up in two weeks.  Dr. Harris also discussed the employee’s diabetes and a cough during this office visit.  At the employee’s request, Dr. Harris sent a note to the employer, dated February 20, 2011, asking that the employee be excused from work until at least March 11, 2011.  He noted that the employee “has been dealing with several complex medical issues and would benefit from the time off to let them settle down.”

The employee treated at HCMC again on March 11, 2011, relating that she had slipped and nearly fallen at work in mid January.  She reported low back pain radiating to her thighs and that she had difficulty walking due to the pain.  The diagnosis at that time was musculoskeletal strain.

The employee returned to work with the employer on April 1, 2011, in a transitional duty position.^[1]  However, that job lasted only ninety days, after which the employee began a part-time, temporary position with ATT Home Health Care as a home health aide, providing personal care services to her daughter.  She worked at a wage loss in that job.

The employee began treating with orthopedist Dr. Nicolas Wills on April 12, 2011.  Dr. Wills recorded that the employee had slipped on the school bus steps on January 21, 2011, and had fallen on her back.  The employee reported that her low back and bilateral thigh pain was worse when she stood or walked.  On exam, Dr. Wills found no tenderness to palpation, no spasms, normal lumbar range of motion, equal strength in the lower extremities, and negative straight leg raising.  X-rays taken that day showed a 7.3 mm anterolisthesis of L4 on L5.

An MRI performed on April 21, 2011, showed moderate L4-5 degeneration with Grade I degenerative spondylolisthesis and mild central and moderate bilateral foraminal stenosis with L4 encroachment/impingement.

The employee continued to follow up with HCMC for her diabetes, and she continued to treat with Dr. Wills for her low back.  When the employee’s back and leg pain increased, Dr. Wills ordered bilateral L4-L5 epidural steroid injections.  The employee had no pain complaints immediately after the injections, which were performed on June 13, 2011.

The employee filed a claim petition on June 15, 2011, seeking temporary partial disability benefits, medical benefits, and rehabilitation services.

On June 23, 2011, Dr. Wills noted that the selective nerve blocks had helped the employee “for a short time,” and he opined that the employee was a surgical candidate, although he recommended that she lose weight.  Again on this date, the employee’s physical examination was normal, but Dr. Wills diagnosed degenerative spondylolisthesis at L4-L5 with neurogenic claudication.  He also indicated that the employee was not released to commercial driving, and he again placed restrictions on the employee’s activities.

On August 25, 2011, Dr. Wills indicated that he had explained to the employee that surgery would not change her low back pain but would likely improve her leg pain.  He modified the employee’s restrictions slightly to provide for increased lifting/carrying and pushing/pulling.  On October 17, 2011, he issued a narrative report setting forth his causation opinion and explaining why the recommended surgery was reasonable and necessary.  He also rated the employee as having a 10% whole body disability pursuant to Minn. R. 5223.0390, subp. 4.E.

The employer and insurer had the employee examined by Dr. Joel Gedan, on September 7, 2011.  Dr. Gedan noted no objective findings, but he did find evidence of decreased effort and symptom magnification.  He was unable to diagnose neurogenic claudication, and he was unclear as to whether the employee had an abnormality in her lumbar spine that would reasonably explain her symptoms.  He did not recommend lumbar surgery, he recommended no restrictions, and he advised that the employee could return to work driving a bus if she participated in a four-week rehabilitation program.

On November 23, 2011, after reviewing additional medical records, Dr. Gedan issued a supplemental report.  At that time, he opined that he was unable to state within a reasonable degree of medical certainty that the employee had sustained any work-related injury to her low back on January 21, 2011.  As explanation for this conclusion, Dr. Gedan cited two medical records generated after the alleged work injury that did not contain any history of that injury.

When the claim petition proceeded to hearing, the employee was claiming entitlement to temporary total disability benefits from January 22, 2011, to April 1, 2011, and temporary partial disability benefits from July 29, 2011, to January 27, 2012; benefits for a 10% permanent partial disability; medical benefits, including surgery; and rehabilitation benefits.  In findings and order filed on March 13, 2012, the compensation judge determined that the employee had sustained a work-related injury on January 21, 2011, and he awarded temporary total, temporary partial, and permanent partial disability benefits as claimed.  The judge also found the medical treatment to be reasonable and necessary, and he approved the requested surgery.  The employer and insurer appeal.

On appeal, the Workers’ Compensation court of Appeals must determine whether “the findings of fact and order [are] clearly erroneous and unsupported by substantial evidence in view of the entire record as submitted.”  Minn. Stat. §176.421, subd. 1 (2010).  Substantial evidence supports the findings if, in the context of the entire record, “they are supported by evidence that a reasonable mind might accept as adequate.”  Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 59, 37 W.C.D. 235, 239 (Minn. 1984).  Where evidence conflicts or more than one inference may reasonably be drawn from the evidence, the findings are to be affirmed.  Id. at 60, 37 W.C.D. at 240.  Similarly, findings of fact should not be disturbed, even though the reviewing court might disagree with them, “unless they are clearly erroneous in the sense that they are manifestly contrary to the weight of evidence or not reasonably supported by the evidence as a whole.”  Northern States Power Co. v. Lyon Food Prods., Inc., 304 Minn. 196, 201, 229 N.W.2d 521, 524 (1975).

The employer and insurer admit that assessment of a witness’s credibility is the unique function of the fact finder.  Nevertheless, the employer and insurer challenge the compensation judge’s finding that the employee testified credibly that she sustained a work-related injury.  The employer and insurer contend, for example, that “every part of Employee’s direct testimony was later contradicted by the Employee and/or the records introduced into evidence.”  This simply is not true.  Further, while it may well be, as the employer and insurer allege, that “there is ample motivation for the Employee to exaggerate, misstate or fabricate,” this is arguably true in nearly every contested case and is irrelevant to the question of whether the judge’s decision is supported by substantial evidence.

It is not the role of this court to evaluate the credibility and probative value of testimony or to choose different inferences from the evidence than those drawn by the compensation judge.  Krotzer v. Browning-Ferris/Woodlake Sanitation Serv., 459 N.W.2d 509, 513, 43 W.C.D. 254, 260-61 (Minn. 1990).  See also Even v. Kraft, Inc., 445 N.W.2d 831, 835, 42 W.C.D. 220, 225-226 (Minn. 1989).  There are no grounds here for us to overturn the compensation judge’s credibility determination.

The employer and insurer contend that substantial evidence does not support the compensation judge’s finding of a work-related injury, in part because the employee did not know the date of her injury, and she did not give a history of injury when she first sought treatment.  The employer and insurer also allege that the employee had intended to retire about the time of the alleged injury.  We are not convinced.

Admittedly the employee did not report the work injury on the day it happened, but she was temporarily working in another state at the time.  She returned to Minnesota on January 29, 2011, treated for low back pain on February 3, 2011, and reported the injury to her employer no later than February 7, 2011,  Medical records contain a reference to the injury by February 16, 2011.  These arguable “delays” do not rise to the level of establishing that a work injury did not occur.  The only reference to an intention to retire was a September 22, 2009, HCMC office note that stated that the employee “thinks that she will only [be driving bus] for another year or so.”  The employee’s testimony, her medical records as a whole, and the first report of injury provide substantial evidence to support the judge’s finding of a work injury occurring on January 21, 2011, and we affirm that finding.

The employer and insurer contend that the judge’s finding that the work injury contributed to the employee’s complaints of low back pain is unsupported by the evidence or is clearly erroneous.  Again, we are not persuaded.

Dr. Wills opined on October 17, 2011, that the employee’s work injury was a substantial contributing cause of the employee’s low back condition and leg problems.  He went on to explain that the injury had substantially aggravated a chronic underlying degeneration.  The employer and insurer contend that Dr. Will’s opinion is lacking in foundation because it falsely assumes that the employee fell on her back.  Dr. Wills’ office notes do contain that history, but the medical history form completed on the date of his first exam describes the injury as a “twist” and “pull,” and it also refers to the employee slipping and missing two or more steps.

A judge’s choice between expert opinions is generally upheld unless the facts assumed by the expert in rendering his opinion are not supported by the evidence.  Nord v. City of Cook, 360 N.W. 2d 337, 37 W.C.D. 364 (Minn. 1985).  We cannot conclude that Dr. Wills had an inaccurate history of the employee’s work injury.  We therefore affirm the judge’s choice of expert opinions as to causation.

The employer and insurer contend that the compensation judge’s award of temporary total and temporary partial disability benefits is unsupported by the evidence.  We disagree.

The employer and insurer allege, in part, that there is no medical opinion supporting a claim of any disability prior to February 16, 2011.  However, when the employee was seen at HCMC on February 3, 2011, the examining doctor took a history indicating that the employee had experienced two weeks of low back pain, sent the employee home with Vicodin, and opined that the employee should be “able to recuperate as an outpatient.”  Based on this evidence, the compensation judge could reasonably infer that the employee had been unable to work from January 30, 2011, to February 16, 2011.  The judge’s award of temporary total disability benefits is modified, however, to commence on January 30, 2011, as the employer’s records and the employee’s testimony both demonstrate that the employee lost no time from work through January 29, 2011.

The employer and insurer also argue that, according to his note from his February 16, 2011, examination, Dr. Harris removed the employee from work based on “several complex medical issues” that were not specifically delineated.  The doctor’s notes, however, clearly reflect that the employee had been seen primarily for low back pain, which has been determined to be related to her work injury.  Medical records thereafter contained restrictions that have prevented the employee from returning to work as a school bus driver.  The judge’s award of temporary total disability benefits is affirmed, as modified.^[2]

The employee returned to work with the employer in a light-duty temporary position on or about April 1, 2011.  When that job ended, the employee immediately found other work within her restrictions.  The employee did not have job placement services at that time and secured the work on her own.^[3]  The employee has had physical restrictions since January 30, 2011, she cannot return to her pre-injury job because of those restrictions, she has secured work within her restrictions at a wage loss, and no evidence was introduced of another job available to her at that time that paid more. The record contains substantial evidence to support the award of temporary partial disability benefits.  See Dorn v. A. J. Chromy Const. Co., 310 Minn. 42, 245 N.W.2d 451, 29 WCD 86 (1976).  We affirm.

At hearing, the employer and insurer contended that there was no ratable permanent partial disability under the permanency guidelines, and, on appeal, they contend that the judge’s finding of a 10% whole body impairment is not supported by substantial evidence.  After careful review of the record, we agree.

A rating under Minn. R. 5223.0390, subp. 4.E., requires, in part, “radicular pain or radicular paresthesia, with or without lumbar pain syndrome, and with objective radicular findings, that is reflex changes or EMG abnormality or nerve root specific muscle weakness in the lower extremity, on examination and myelographic, CT scan or MRI evidence of spinal stenosis . . . that impinges on a lumbar nerve root and the medical imaging findings correlate with the findings on neurologic examination . . . ten percent.”  (Emphasis added.)

The compensation judge accepted Dr. Wills’ rating of permanency under this subdivision but offered no explanation as to how the employee’s condition satisfied these requirements.  While the MRI provided evidence of spinal stenosis,^[4] all of Dr. Wills’ neurologic examinations were normal.  There are no medical records to support a finding of reflex change or nerve root specific muscle weakness on examination.  Since these criteria were not satisfied, the employee has not proven entitlement to benefits for a 10% permanent partial disability of the whole body.  We therefore reverse that award.

The employer and insurer make numerous arguments about the permanent treatment parameters and how the treatment rendered to date does not comply with those rules.  However, these arguments were not raised at hearing and may not be raised for the first time on appeal.  Dawson v. University of Minn., slip. op. (W.C.C.A. May 6, 1999).  In addition, while initially paying benefits, the employer and insurer later denied primary liability, and the treatment parameters do not apply to treatment rendered after such a denial.  Minn. R. 5221.6020, subp. 2.^[5]

In his September 7, 2011, report, Dr. Gedan stated that “past medical treatment was generally reasonable and necessary to cure and relieve the effects of the diagnosed condition,” but he went on to say that “steroid injections for nonradicular low back pain” were not reasonable or necessary.  Dr. Wills, on the other hand, opined that the employee’s medical treatment, including the steroid injections, was reasonable and necessary and related to the work injury.  This is again a judge’s choice between expert opinions, and we affirm the judge’s choice of Dr. Wills’ opinion over that of Dr. Gedan.

The employer and insurer also appeal from the judge’s finding that the employee is entitled to the surgery recommended by Dr. Wills.  However, at hearing, the employer and insurer argued only that the employee did not sustain a work-related injury and that, if she did, that injury was temporary and brief.  Now, on appeal, the employer and insurer argue that the treatment parameters do not support an award of surgery.  As indicated earlier, the treatment parameters are not applicable.  Dr. Wills has recommended the surgery and has explained that the employee’s response to the epidural steroid injections supports his recommendation.^[6]  Substantial evidence supports the judge’s approval of surgery, and we again affirm the judge on this issue.