The employer and insurer appeal from various findings related to the compensation judge's conclusions (1) that a previously litigated denial of prospective fusion surgery on the employee’s back is not res judicata as to the employee’s current claim for payment for completed fusion surgery at the same levels of the employee’s spine and (2) that such surgery, performed on April 18, 2003, was reasonable and necessary and causally related to the work injury.  We affirm.

On January 30, 1997, Ronald Odash sustained an injury to his low back when he fell from his truck in the course of his work as a delivery truck driver with Pepsi, Inc.  At the time of his injury, Mr. Odash [the employee] had been working for Pepsi, Inc. [the employer], for about ten years, during which time he had no physical inability performing his job duties, never any need for restrictions, and never any difficulty engaging in recreational activities such as waterskiing, snow skiing, and softball.  Mr. Odash [the employee] was twenty-eight years old on the date of his injury and was earning a weekly wage of $937.77.  Pepsi, Inc. [the employer], and its insurer acknowledged liability for the injury and commenced payment of benefits.  Subsequent to his injury, the employee experienced pain in his low back and legs that grew increasingly more severe and for which he has continued to be treated extensively by several different medical providers.

The matter came on for the first of several hearings on December 29 and 30, 1998, before Compensation Judge David S. Barnett.  Issues at hearing included whether the employee had reached maximum medical improvement [MMI] on July 17, 1998, relative to the work injury, “[w]hether exploratory low back surgery is reasonable and necessary treatment causally related to” that injury, and, if the employee had reached MMI and surgery was not reasonable and necessary, whether the employee had sustained a 10% whole-body permanent partial disability as a result of the injury.  By findings and order filed March 15, 1999, Judge Barnett concluded in part that the evidence of record failed to establish “that at the present time surgery on employee’s low back would be reasonable or necessary to cure or relieve the effects of the employee’s work-related personal injury.”  Concluding also that the employee’s work-related low back injury had “through the date of hearing, and continuing, constituted a substantial contributing factor to the employee’s disability” and that the employee had reached MMI with regard to that injury, Judge Barnett awarded the employee compensation for a 10% permanent partial disability of his whole body consequent to his work injury.  The employee appealed from Judge Barnett’s denial of surgery and certain other findings, and this court eventually affirmed the judge’s denial.

On April 6, 2000, the employee came under the care of orthopedic surgeon Dr. Timothy Garvey at the University of Minnesota Medical School, who concluded that surgery was an option for relieving the employee’s complaints of pain.  In a report to the employee’s attorney dated September 28, 2000, Dr. Garvey indicated in part that, assuming the truth and accuracy of the employee’s history, it was his opinion that the employee’s January 30, 1997, work injury had either caused, aggravated, or accelerated certain lumbar degenerative disc changes and a small central disc protrusion that were revealed on an MRI scan of the employee’s low back, for which Dr. Garvey had concluded that surgery was a reasonable and necessary treatment alternative.  Dr. Garvey did indicate, however, that certain contraindicating psychological factors did exist and that any final recommendation of surgery would only be made after further evaluation “and after all of your medical-legal circumstances are finalized.”

The matter came on again for hearing on January 25, 2001, this time before Compensation Judge Bradley J. Behr.  Issues at hearing as identified in Judge Behr’s eventual findings and order included “whether the proposed two-level fusion surgery is reasonable and necessary to cure and/or relieve the employee’s symptoms” and whether the employee had reached MMI from a psychiatric/psychological condition allegedly related to his work injury.  By findings and order filed April 17, 2001, Judge Behr concluded in part that the employee had reached MMI from the effects of his psychological condition and that “the evidence failed to demonstrate that the multi-level fusion surgery proposed by Dr. Timothy Garvey is reasonable and necessary to cure and relieve the effects of the employee’s 1/30/97 injury.”  No appeal was taken from Judge Behr’s findings and order.

The employee continued to see Dr. Garvey several times in 2001, who continued to recommend fusion surgery as an option in the treatment of the employee’s low back problems.  On September 25, 2001, the employee filed a medical request, requesting payment of $660.24 in medical bills from Dr. Garvey.  In their medical response filed October 18, 2001, the employer and insurer refused payment, on the simply asserted grounds that “[t]hese billed treatments were not reasonable and necessary or causally related to the Employee’s January 30, 1997 injury to cure and/or relieve the effects of that injury.”  No medical evidence or argument was offered in support of this denial. 

On November 13, 2001, the employee filed another medical request, this time seeking payment for the fusion surgery itself that was being recommended by Dr. Garvey, just as he had done before Judge Behr.  In a medical response filed December 3, 2001, the employer and insurer denied this request, copiously supporting their denial with detail from the employee’s medical history, to the sole effect that the treatment at issue was not reasonable and necessary or in compliance with the medical treatment parameters.  There was no reference in the medical response to any issue as to the causal relationship of the work injury to the employee’s alleged need for surgery.

The matter eventually came on again for hearing, on May 15, 2002, this time before Compensation Judge Danny P. Kelly, before whom the sole issue, as articulated by Judge Kelly in his eventual findings and order, was “[w]hether the recommended L4-sacrum decompression and fusion surgery is causally related, reasonable and necessary to cure and relieve the effects of the January 30, 1997 personal injury.”  The hearing was apparently suspended on that date, with the record held open for thirty days to permit the employee to obtain a supplemental report from Dr. Garvey.  The employee’s attorney subsequently wrote to Dr. Garvey, apparently inquiring as to whether or not the doctor’s opinions had changed since his previous narrative report, and Dr. Garvey replied on June 5, 2002, indicating essentially that they had not.  In his letter, Dr. Garvey stated that, “[o]n a risk/benefit ratio, I believe that it is not unreasonable to offer this human being the option of improving,” in that he was in substantial pain and “there is a chance that he would have a significant improvement,” although he “is high risk for nonresolution of his symptoms.”  There is no mention in Dr. Garvey’s letter of any issue as to the causal relationship of the work injury to the alleged need for the recommended surgery.

Dr. Garvey’s letter was apparently submitted to Judge Kelly on June 10, 2002, and the hearing before the judge was evidently completed and the record closed on June 26, 2002.  By findings and order filed August 19, 2002, Judge Kelly concluded in part that the employee had “failed to establish by a preponderance of the evidence that the surgery recommended by Dr. Garvey involving a decompression and fusion L4-sacrum is causally related, reasonable and necessary to cure the effects of the January 30, 1997 personal injury.”  Nowhere in his findings and order or accompanying memorandum does Judge Kelly discuss at all any issue as to the causal relationship between the work injury and the alleged need for the surgery at issue, although in the four most substantive of his seven findings the judge examines in detail issues of the reasonableness and necessity of the surgery.  On September 18, 2002, the employee appealed from Judge Kelly’s decision, raising only the specific issue of “[w]hether the Compensation Judge err[]ed by making a finding on an issue regarding the issue of causation not raised at the trial.”  On December 18, 2002, however, that appeal was dismissed for the employee’s failure to file a brief within thirty days after filing his notice of appeal.

On May 31, 2002, between the two dates of hearing before Judge Kelly, the employee had filed an additional medical request, seeking payment of various bills related to services by Dr. Garvey and by neurologist Dr. Steven Trobiani.  In their medical response filed June 14, 2002, the employer and insurer had refused to pay on grounds that they “deny that the Employee’s requested medical treatment is reasonable and necessary to cure and relieve the effects of his January 30, 1997 injury.”  In a treatment follow-up note dated July 24, 2002, Dr. Trobiani stated, “It remains my opinion that [the employee] is in need of surgical intervention in an effort to relieve his back pain and allow him to be weaned off narcotic medication.”  On November 6, 2002, the matter of the employee’s May 31, 2002, medical request was considered at an administrative conference before mediator/arbitrator Nell Nere, where the sole issue was the reasonableness and necessity of the services for which the employee had sought payment in his May 31, 2002, medical request.  In a decision and order filed January 24, 2003, mediator/arbitrator Nere concluded that some but not all of Dr. Trobiani’s billings were “reasonably required” and so payable, but she denied all of the claims for payment of the billings for Dr. Garvey’s services as “not reasonably required.”  On February 4, 2003, the employee filed a request for formal hearing.

The matter came on for hearing again on March 18, 2003, this time before Compensation Judge Ronald E. Erickson, where issues were those billings related to Dr. Garvey’s and Dr. Trobiani’s services that had been denied in the January 24, 2003, decision and order of mediator/arbitrator Nere.  In a follow-up treatment note dated March 31, 2003, prior to Judge Erickson’s findings and order, Dr. Trobiani reiterated that the employee “remains incapacitated as a consequence of his lumbar pain and, in my opinion, is still in need of surgery.”  In his findings and order filed April 1, 2003, Judge Erickson denied the employee’s claim for payment of the bills, reiterating throughout his decision a history of evidence and adjudicated conclusions that the surgery recommended by Dr. Garvey and medical services related to that recommendation were not reasonable and necessary, that the employee was “not a viable candidate” for the surgery at issue.  Only once in his seven-page decision does Judge Erickson make any reference to the causal relationship of the work injury to the proposed surgery, and that is in his simple reference in passing, in Finding 14, to Judge Kelly’s finding “that the employee had failed to establish by a preponderance of the evidence that the surgery recommended by Dr. Garvey involving a decompression and fusion of the L4-sacrum was causally related, reasonable and necessary to cure and relieve the employee from the effects of his work injury.”  The issue of such a causal relationship is nowhere discussed in Judge Erickson’s decision, although, again, the issue of the reasonableness and necessity of the proposed fusion surgery is addressed in copious detail.

Consequent to his work injury, the employee had been taking several pain medications, including MS Contin, Hydromorphine, Celebrex, and Neurontin, which he continued to take for increasing pain complaints up until the spring of 2003.  In February or March of 2003, he stopped treating with Dr. Garvey and was referred by his family practitioner, Dr. James Carrabre, to neurosurgeon Dr. Terry Hood, who ordered a lumbar discography.  The discography was read to reveal concordant low back pain at L5-S1, which extended into the lower extremities bilaterally, and “familiar but not identical” low back pain without leg pain at L4-5.  Dr. Hood subsequently referred the employee to a partner, neurosurgeon Dr. Matthias Feldkamp, who examined the employee on April 2, 2003.  Dr. Feldkamp recommended an interbody fusion from L4 through S1, such as had been suggested by Dr. Garvey, rating the employee’s chances of symptom reduction at seventy to eighty percent.  Notwithstanding his having been repeatedly denied payment for the proposed surgery and services related to it, on April 18, 2003, the employee went forward with the recommended L4-sacrum decompression and fusion surgery, performed by Dr. Feldkamp.  On follow-up with Dr. Feldkamp on May 12, 2003, the employee reported “that his back pain is dramatically better than it was prior to surgery,” “that he feels like a new man, and his wife is extremely happy.”  By July 30, 2003, the employee’s improvement had slowed and was still incomplete, but he continued to report to Dr. Feldkamp “that his symptoms are dramatically better than prior to surgery,” and Dr. Feldkamp continued to taper down the employee’s MS Contin prescription.  By March 29, 2004, Dr. Feldkamp was able to report that the employee’s “pain, despite being off all his narcotics, is considerably better than prior to surgery” and that “[h]e really looks very good.”  On that same date, the doctor also reported as follows:

On May 21, 2004, about a year after his surgery, the employee filed a claim petition, alleging entitlement to temporary total disability benefits continuing from April 18, 2003, to permanent partial disability benefits for an unspecified whole-body impairment rating less the 10% already paid, and to a rehabilitation consultation and job placement services.  On May 24, 2004, Dr. Feldkamp signed a health care provider report, indicating that the employee was subject to a permanent partial disability to 20% of his whole body, pursuant to Minnesota Rule 5223.0390, subparts 3C(2) and 5B, based on his lumbar pain syndrome and spinal fusion surgery.

On February 15, 2005, the employee was examined for the employer and insurer by orthopedic surgeon Dr. Michael Davis, who had also examined the employee in August of 1999.  It was Dr. Davis’s opinion in part that neither the symptoms of which the employee had complained in August of 1999 nor the symptoms leading up to his surgery in April of 2003 were causally related to the employee’s work injury.  It was his further opinion that the surgery at issue had not been reasonable and necessary.  About a month later, however, Dr. Feldkamp, in a letter to the employee’s attorney dated March 18, 2005,  reiterated that “[t]he records reviewed make it abundantly clear that the [employee], while not free of any back injuries in the past, was healthy and otherwise well until the work injury on 1-30-97" and that “the injury of 1-30-97 was either the cause or substantially contributed to [the employee’s] discogenic back pain.”  He stated further that “it would appear that the operation has been a success, and therefore was necessary to cure and relieve the effects of [the employee’s] 1-30-97 work injury,” noting also that “decompression at L5-S1 and fusion from L4 through S1 had been proposed by Dr. Garvey as well as by Dr. Pinto.”

The matter came on for hearing yet another time on May 19, 2005, before Compensation Judge John Ellefson.  Issues at this hearing included in part the following:  (1) whether res judicata or collateral estoppel barred a finding that the employee’s work injury was a substantial contributing cause of his need for fusion surgery in 2003 or that that surgery was reasonable and necessary treatment for his medical condition; (2) if not, whether the employee’s 2003 spinal fusion was reasonable and necessary and causally related to his work injury; and (3), if reasonable and necessary and causally related, what temporary total disability, permanent partial disability, and medical benefits was the employee entitled to receive.  At the hearing, the employee testified that, due to pain in the soft tissues at the site of his fusion, his back pain was still at about the same level as it had been before his surgery–about a level five or six on a scale of one to ten–but that his leg pain had receded from a level ten before the surgery to about a level six or seven at its worst, sometimes being much less than that.  He testified also that he was now able to participate in many household, parenting, and other activities that he had been unable to participate in prior to the surgery and that he had been able to discontinue use of MS Contin and most of the Hydromorphine, although he still needed to take “a lot of ibuprofen; a lot” for his soft tissue pain.  He testified that the surgery was in his mind “one hundred percent” worth the undertaking, because now “I can live,” “I can have a goal” “[t]hat I can live life again.  I can do something.”

By findings and order filed July 13, 2005, Judge Ellefson concluded in part, at Finding 6, that the findings of Judges Barnett, Behr, and Kelly

In reviewing cases 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 (1992).  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, “[f]actfindings are clearly erroneous only if the reviewing court on the entire evidence is left with a definite and firm conviction that a mistake has been committed.”  Northern States Power Co. v. Lyon Food Prods., Inc., 304 Minn. 196, 201, 229 N.W.2d 521, 524 (1975).  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 the evidence or not reasonably supported by the evidence as a whole.”  Id.

Compensation Judge Ellefson concluded that “[t]he findings of Judge Kelly [in April 2002] do not establish that any need for a fusion surgery that the employee may develop in the future would not be ca[us]ally related to the [employee’s] work injury.”  The employer and insurer contend that Judge Ellefson’s refusal to apply the doctrine of res judicata or collateral estoppel as to causation based on Judge Kelly’s decision is legally erroneous.  They argue that “[r]easonableness and medical necessity may change when an employee’s medical condition changes, but causation does not,” that “[j]ust because the Employee failed to prove all three elements in the 2002 [proceeding], does not mean that he gets a second chance to prove causation.”  (Italics in original.)  We are not persuaded.

"A fundamental rule embodied in the related doctrines of res judicata and collateral estoppel is that a `right, question or fact distinctly put in issue and directly determined by a court of competent jurisdiction . . . cannot be disputed in a subsequent suit between the same parties.'"  Kaiser v. Northern States Power Co., 353 N.W.2d 899, 902 (Minn. 1984), quoting Montana v. United States, 440 U.S. 147, 153 (1979) (further citations omitted).  Moreover, “[t]he doctrine of res judicata provides that ‘[a] judgment on the merits in a prior suit bars a second suit involving the same parties based on the same cause of action.’"   Salverda v. City of Roseville, slip op. (W.C.C.A. Jul. 21, 1993), quoting Hansen v. American Nat'l Bank, 396 N.W.2d 642, 645 (Minn. App. 1986).  Further, “Decisions of compensation judges involving the merits of a claim are res judicata if not appealed.”  Id., citing generally Brix v. General Accident & Assurance Corp., 254 Minn. 21, 25-27, 93 N.W.2d 542, 545-46, 20 W.C.D. 281, 286-87 (1958); Westendorf v. Campbell Soup Co., 309 Minn. 550, 550-51, 243 N.W.2d 157, 158, 28 W.C.D. 460, 460 (1976) (both discussing effects of res judicata).  However, res judicata does not preclude litigation of issues that were not specifically decided in a prior proceeding.  Fischer v. Saga Corp., 498 N.W.2d 449, 48 W.C.D. 368 (Minn. 1993), citing 3 Larson, The Law of Workmen’s Compensation § 79.72(f) at 15-426.272(100) (1992); see also Westendorf v. Campbell Soup Co., 309 Minn. 550, 243 N.W.2d 157, 28 W.C.D. 460 (Minn. 1976).  Finally, res judicata is not to be applied rigidly; “[a]s a flexible doctrine, the focus is on whether its application would work an injustice on the party against whom estoppel is urged.”  Johnson v. Consolidated Freightways, Inc., 420 N.W.2d 608, 613-14 (Minn. 1988) (citations omitted).

In this case, after careful scrutiny of the remarkably long and detailed record of litigation in this case,^[2] we can only conclude that the causal relatedness of the work injury to any need for fusion surgery was never truly at issue and certainly never fully litigated prior to the proceeding before Compensation Judge Ellefson.  Even in the proceeding before Compensation Judge Barnett in 1998, where causation of the need for surgery was nominally at issue, the denied surgery was exploratory, not fusion surgery, and the ultimate finding was only that the proposed surgery had not been proven to be reasonable and necessary.  Indeed, Judge Barnett then went on immediately to find that the work injury had, “through the date of hearing, and continuing, constituted a substantial contributing factor [in] the employee’s disability” (underscoring added), if not specifically in any alleged need for surgery.

Subsequently, in 2001, the surgical issue before Compensation Judge Behr was “[w]hether the proposed two level fusion surgery is reasonable and necessary to cure and/or relieve the employee’s symptoms.”  Judge Barnett had implied in his Finding 65 the possibility that, perhaps at a later time, surgery on the employee’s low back might be reasonable and necessary, but Judge Behr, in Finding 7, concluded that the evidence failed to demonstrate that the surgery at issue was “reasonable and necessary,” having found in Finding 6 that the employee had “failed to prove . . . that he is a good psychological candidate for surgery.”  There is never any suggestion in Judge Behr’s decision that the surgery at issue, had it been found to be sufficiently reasonable and necessary treatment under the circumstances, might nevertheless be noncompensable for being causally unrelated to the work injury.

Nor is there any indication in Judge Erickson’s April 2003 decision, on the compensability of Dr. Garvey’s and Dr. Trobiani’s treatment expenses, that the causal relationship of the work injury to the employee’s low back condition was being contested, although the reasonableness and necessity of the surgery-related care at issue remained frequently referenced.

We acknowledge that the issue in the hearing before Judge Kelly in 2002 was identified in the judge’s findings and order as “[w]hether the recommended L4-sacrum decompression and fusion surgery is causally related, reasonable and necessary to cure and relieve the [work] injury” and that the judge subsequently found that the employee had failed to prove that the recommended surgery was “causally related, reasonable and necessary to cure and relieve” that injury.  However, particularly in light of the extensive previous litigation of what had been, at least in the hearing before Judge Behr, a request for nearly identical surgery, we conclude that it was not legally improper for Judge Ellefson to conclude, as his memorandum makes evident that he did, that the causal relationship of the surgery to the work injury was not truly litigated before Judge Kelly.^[3]

The employer and insurer contend that, even if compensation for the fusion surgery here at issue is not precluded by res judicata, substantial evidence does not support Judge Ellefson’s decision that the employee’s decompression and fusion surgery on April 18, 2003, was both causally related to the work injury and reasonable and necessary in treatment thereof.

With regard to the reasonableness and necessity of the surgery, Judge Ellefson specifically found, at Finding 12, that, “[b]ased on the substantial reduction in pain, the surgery was successful and was reasonable and necessary treatment of the employee’s low back injury.”  The employer and insurer concede that a change in the employee’s back condition subsequent to Judge Kelly’s 2002 denial of compensation could have rendered the surgery nevertheless necessary in 2003.  They contend, however, that there is no evidence that the employee’s condition changed over the course of that year.  They acknowledge that the employee testified that his low back and leg pain level got progressively worse over the course of that year, but they argue that he also testified that it got progressively worse between 1997 and 2002 and that therefore the overall condition really did not change at all in the year following 2002.  Nor, they argue, did the judge cite in support of his decision any actual medical evidence, apparently relying solely on the employee’s testimony to those ends.  Moreover, even the employee’s testimony, they argue, was not consistently supportive of the judge’s conclusion.  They argue that, although the judge found that the surgery at issue “substantially” reduced the employee’s pain and essentially eliminated the employee’s use of narcotics, the employee himself testified that he was still taking the narcotic Hydromorphine and “a lot of ibuprofen; a lot,” that there was little change in his back pain, and that his leg symptoms had only decreased from a level “ten” to a level “seven” on a scale of one to ten.  We are not persuaded.

While there has certainly been a very legitimate question in this case for many years as to the employee’s candidacy for the fusion surgery long at issue, the fact remains that both Dr. Garvey and Dr. Tobriani for years, and more recently Dr. Feldkamp, have repeatedly concluded that the surgery at issue, however risky, was a reasonable treatment alternative for the employee, particularly in light of his evidently increasing pain.  It was not unreasonable for the compensation judge in this case to credit the opinions of Drs. Garvey, Trobiani, and Feldkamp over the opinion of Dr. Davis.  See Nord v. City of Cook, 360 N.W.2d 337, 342-43, 37 W.C.D. 364, 372-73 (Minn. 1985) ("the trier of fact's choice between experts whose testimony conflicts is usually upheld [unless] the facts assumed by the expert in rendering his opinion are not supported by the evidence"). Moreover, it was also not unreasonable, in light of the employee’s own testimony in addition to his reports to Dr. Feldkamp, for the compensation judge to conclude that the surgery so long requested has after all proven effective in curing and relieving the effects of the employee’s injury.  See Brening v. Roto-Press, Inc., 306 Minn. 562, 563, 237 N.W.2d 383, 385, 28 W.C.D. 225, 226 (Minn. 1975) (the employee is the person most familiar with the severity of his symptoms and the limitations they place on his physical activities); Brennan v. Joseph G. Brennan, M.D., 425 N.W.2d 837, 839-40, 41 W.C.D. 79, 82 (Minn. 1988) (assessment of a witness's credibility is the unique function of the trier of fact).  Because it was not unreasonable, we will not reverse Judge Ellefson’s conclusion that the employee’s surgery has been reasonable and necessary in the cure and relief of the effects of his low back condition.  See Hengemuhle, 358 N.W.2d at 59, 37 W.C.D. at 239.

With regard to the causal relationship between the work injury and the need for the fusion surgery that was awarded, Judge Ellefson specifically found, at Finding 14, that “severe chronic pain caused by the employee’s work injury was a substantial contributing cause of the employee’s need for his 2003 fusion surgery.”  The judge subsequently went on to reiterate in his memorandum that that necessary causal relationship was “clear,” explaining that “[the employee’s] chronic pain [that precipitated the surgery] is secondary to the work injury.  There have been no other injuries to his back.  While there may be other factors that contribute to his pain, it is a major and probably the primary cause of the pain.”  The employer and insurer contend that there is no substantial evidence to support this conclusion.  We are not persuaded.

As suggested above in our discussion of the res judicata issue, the causal relationship of the work injury to any alleged need by the employee for low back surgery over the history of his workers’ compensation litigation has apparently never been really contested by the employer and insurer prior to the hearing before Judge Ellefson.  In all of those earlier proceedings, it appears from the resulting findings and orders that the focus of the litigation was virtually exclusively on the reasonableness and necessity of the surgery at issue, not on its causal relationship to the work injury.  We acknowledge that the burden of proof in obtaining workers’ compensation medical benefits is on the injured employee making claim to those benefits.  See, e.g., Adkins v. University Health Care Center, 405 N.W.2d 231, 39 W.C.D. 898 (Minn. 1987) (the employee has the burden of proving the propriety and necessity of requested medical treatment); see also Salmon v. Wheelbrator Frye, 409 N.W.2d 495, 497-98, 40 W.C.D. 117, 122 (Minn. 1987) (the employee has the burden of proving that a work-related injury caused his disability); Brown v. Prospect Foundry, Inc., slip op. (W.C.C.A. Oct. 15, 2002) (where the employer and insurer denied liability for the injury, alleging that any need for medical treatment was the result of a disease process or nonwork-related incident, the compensation judge did not err by placing the burden of proof regarding causation on the employee).  However, particularly in light of Dr. Feldkamp’s express opinion on March 29, 2004, that the employee’s history “would likely qualify for a Gillette type of injury as well as a specific event that caused this pain,” we cannot conclude that it was unreasonable for the compensation judge to find, in apparent reliance on that opinion,^[4] that the employee’s need for the surgery here at issue was causally related to his work injury.  See Nord, 360 N.W.2d at 342-43, 37 W.C.D. at 372-73.

Because it was not unreasonable for Judge Ellefson to conclude that the fusion surgery here at issue was finally, after long denial, reasonable and necessary treatment for the employee’s low back condition, and because it was also not unreasonable for the judge to conclude that the employee’s work injury was causally related to the employee’s need for that surgery, we affirm Judge Ellefson’s award of the surgery at issue and all related findings.  See Hengemuhle, 358 N.W.2d at 59, 37 W.C.D. at 239.