The employee appeals from the compensation judge’s finding that the employee’s work injuries were merely temporary and from his denial of claimed medical treatment expenses, including proposed spinal fusion and disc replacement surgery.  We affirm the judge’s decision as to the temporary nature of the employee’s work injuries and also affirm the judge’s denial of the employee’s request for approval of surgery, but we reverse and remand the matter to the judge for reconsideration on the issue of the compensability of certain other medical expenses.

The employee began working for Branch Manufacturing [Branch] in 1992.  The work was often heavy and involved substantial lifting.  In about 1995, the employee started receiving periodic chiropractic care for low back pain.  He apparently missed little or no time from work due to these symptoms.

In 2003, the employee’s low back pain increased significantly, and he began experiencing pain into his leg.  An MRI performed in August of 2003 disclosed extensive degenerative changes from L3 to the sacrum as well as a disc herniation at L4-5, stenosis at L3-4 and L4-5, and a disc protrusion at L5-S1.  Subsequently, in September of 2003, the employee underwent surgery, performed by Dr. Mahmoud Nagib, in the nature of a hemilaminectomy and discectomy at L4-5 on the left.

The employee returned to work for Branch, with restrictions, about six weeks after his surgery.  Ultimately his restrictions were lifted, and he resumed his usual job duties as a tool and die maker.

On September 16, 2004, the employee experienced sharp low back pain while moving a heavy plate at work.  He reported the incident to his supervisor and eventually sought treatment from several physicians, including Dr. Paula Rehder and Dr. Nagib.  The employee underwent conservative care for low back and leg pain, and another MRI scan was performed.  That scan, taken on November 2, 2004, showed mildly severe central stenosis due to broad-based disc herniations or bulges at L3-4 and at L4-5, as well as a small herniation causing displacement of the S1 nerve root.

After reviewing the MRI, Dr. Nagib recommended against fusion surgery in view of the employee’s weight^[1] and relatively young age.^[2]  Dr. Nagib did advise the employee to observe bending and lifting restrictions, but the employee nevertheless continued to perform most of his usual job duties.

The employee was later referred to Dr. Keith Davies for additional treatment, and yet another MRI was performed.  While noting that the L3-4 herniation had become smaller, Dr. Davies recommended surgery, and, on November 21, 2005, the doctor performed a L3-4 decompression and microdiscectomy.

Branch was insured by SFM Mutual Insurance Company at the time of the employee’s 2004 injury.  Branch and SFM admitted liability for the injury and voluntarily paid the employee various related benefits, including wage loss benefits, medical expenses, and benefits for an 18% whole body impairment.

The employee continued to work at his usual job at Branch until June of 2006, when he left to work in a family business.  In the interim between his surgery and the job change, the employee received sporadic treatment for low back pain.

In November of 2007, the employee began working for Minnesota Tool & Die Works [Minnesota Tool], performing heavy work similar to the work he had done for Branch.  He experienced a twinge in his low back at work on January 25, 2008, but lost no time and sought no treatment for those symptoms.  About six months later, on July 8, 2008, the employee had another episode of low back pain while lifting a piece of steel, again at work.  He stayed on the job and sought no medical treatment for several weeks.

In August of 2008, the employee was seen at Fairview Lakes Medical Center emergency department, complaining of low back pain, radiating into his right leg, which had reportedly started while he had been lifting.  Another lumbar MRI, performed on August 18, 2008, disclosed multilevel degenerative disc and facet disease, among other findings.  The employee by this time was treating with Drs. Steven Thompson and Richard Gregory.  After reviewing the most recent MRI, Dr. Gregory concluded that no one lumbar level was significantly worse than the rest.

Conservative treatment, including physical therapy in October and November of 2008, failed to alleviate the employee’s symptoms.  An EMG of the employee’s lower extremities, conducted by Dr. Laura Li, was interpreted to show chronic or prior radiculopathy at L4-5.  Dr. Li advised the employee to try medication, exercise, and weight loss to reduce his symptoms, characterizing surgery as a last resort option.  Dr. Gregory agreed with Dr. Li’s assessment.

The employee subsequently had additional diagnostic studies, including an additional MRI, another EMG, and injections.  Based on the results of these tests, Dr. Glenn Buttermann recommended that the employee undergo a disc replacement at L3-4 with fusions from L4-5 through L5-S1 as well as a left L5-S1 laminectomy and possible lateral recess decompression.

In August 2010, the employee filed a claim petition seeking approval for the surgery recommended by Dr. Buttermann.  Branch and SFM and Minnesota Tool and its insurer, Indiana Insurance, denied that the employee’s work injuries substantially contributed to his need for treatment.  Several medical providers and Blue Cross/Blue Shield Minnesota intervened.

The matter came on for hearing before a compensation judge on April 13, 2011.  At that time, the parties stipulated that the employee had sustained a work injury on September 16, 2004, while employed by Branch and had also sustained work injuries on January 25 and July 8, 2008, while employed by Minnesota Tool.  Evidence included the employee’s testimony, certain medical records, and opinions from Dr. Buttermann; Dr. John Sherman, who evaluated the employee on behalf of Branch and SFM; and Dr. Khalafalla Bushara, who evaluated the employee on behalf of Minnesota Tool and Indiana Insurance.

In a decision issued on August 5, 2011,^[3] the compensation judge concluded that the work injuries of September 2004, January 2008, and July 2008 were merely temporary exacerbations of the employee’s preexisting multilevel degenerative disc disease.  He also concluded that the proposed surgery was not reasonable, necessary, or causally related to the work injuries and that the intervenors were not entitled to payment.  All claimed benefits were denied.  The employee appeals.

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).

Three physicians provided narrative opinions concerning the nature and extent of the employee’s work injuries.  Dr. Buttermann, the physician recommending disc replacement and fusion surgery, reported that the September 2004 work injury was a substantial contributing cause of the employee’s current lumbar condition and need for treatment and that the 2008 injuries were also significant.  Dr. Bushara reported that the two 2008 work injuries were temporary and did not contribute to the employee’s current condition.  Dr.  Sherman reported that the employee’s condition was the result of the natural progression of the employee’s underlying degenerative disc disease and that the 2004 work injury was merely temporary.

The compensation judge expressly accepted the opinions of Drs. Sherman and Dr. Bushara, explaining in his memorandum, in part, as follows:

On appeal, the employee argues that the compensation judge erred in accepting Dr. Sherman’s opinion as to the nature of the 2004 injury, in that Dr. Sherman “failed to acknowledge” that the L3-4 disc was not shown to be herniated prior to the 2004 injury.  The employee also contends that, because Branch and SFM paid the employee benefits for an 18% permanent partial disability for the 2004 injury, that injury is essentially by definition permanent, and the fact that Dr. Sherman failed to acknowledge the 18% rating and payment makes it “clear that he did not have adequate foundation for his opinion.”  Finally, the employee argues that because Dr. Sherman demonstrated no expertise in the area of genetics, his opinion that the employee’s lumbar condition was “secondary to genetic predisposition” further renders his  opinion without the required foundation.  We find these arguments unpersuasive.

Causation was a primary issue at hearing.  For that reason, the parties asked the compensation judge to make a decision as to the nature and extent of the employee’s three admitted work injuries.  Counsel for Branch and SFM alleged, in opening statements, that the evidence, including the employee’s testimony, would “show and prove that the employee resolved his symptoms from the 2004 work injury.”  In support of their denial of the employee’s claim, Branch and SFM solicited and then submitted the expert opinion of Dr. Sherman, who concluded that the 2004 injury was temporary.^[4]  Contrary to the employee’s contention, SFM’s voluntary payment of benefits, even including permanent partial disability benefits, does nothing whatsoever to establish that the 2004 injury was in fact permanent.  See, e.g., Parker v. Univ. of Minn., 66 W.C.D. 373, 377 (W.C.C.A. 2006) (voluntary payment of benefits does not preclude an employer and insurer from later changing their position and asserting defenses to continued liability).  And we find nothing in the law that would require an employer and insurer who wish to contest continued liability to first claim that previous benefits were made under some kind of mistake.  Indeed, mistake is only relevant if the employer and insurer intend to seek a credit or repayment, and certainly they cannot be compelled to do so.  See Minn. Stat. § 176.179.  For all these reasons, the fact that Dr. Sherman failed to acknowledge prior payments for the 2004 injury is completely irrelevant to the question of whether the judge was entitled to rely on Dr. Sherman’s opinion.^[5]  Similarly, Dr. Sherman was in no way required to either acknowledge or  explain away the fact that the employee’s L3-4 disc was not herniated prior to the 2004 injury.  The temporal connection does not establish causation and does little or nothing to contradict expert opinion that the employee’s condition is merely the result of the natural progression of the employee’s underlying degenerative disc disease.  The employee’s argument concerning Dr. Sherman’s expertise in the area of genetics also provides no grounds for reversal.

The employee also contends that the compensation judge erred in relying on Dr. Bushara’s opinion that the two 2008 injuries, occurring during the employee’s employment with Minnesota Tool, were also temporary.  In support of his position on this issue, the employee relies again on the causation opinion of Dr. Buttermann.  The employee also contends that the judge erred in relying on the opinion of Dr. Bushara because there is no evidence as to what factual background was provided to Dr. Bushara, beyond his own listing of the medical records he reviewed. As such, according to the employee,  it is “speculative as to what factual information he had regarding [the employee’s] employment activities at Branch and Minnesota Tool.”^[6]  Again, the employee’s arguments are not persuasive.

Dr. Bushara is a medical doctor who examined the employee and issued an opinion after reviewing the employee’s medical records.  All of the employee’s arguments to the contrary notwithstanding, Dr. Bushara and Dr. Sherman clearly had foundation to issue opinions on causation.  See Drew v. Kohls, 55 W.C.D. 33, 39 (W.C.C.A. 1996).

A compensation judge’s choice between conflicting expert opinions is generally upheld if the facts assumed by the expert are supported by substantial evidence.  See Nord v. City of Cook, 360 N.W.2d 337, 342-43, 37 W.C.D. 364, 372-73 (Minn. 1985).  The fact that another judge might have weighed the evidence differently or chosen another expert opinion provides no basis for reversal.  Because we cannot conclude that the compensation judge erred in relying on the opinions of Drs. Sherman and Bushara, we affirm the compensation judge’s decision that the 2004 and 2008 work injuries were merely temporary.

The compensation judge concluded that the admitted work injuries did not substantially contribute to the employee’s current lumbar condition.  His decision to that effect is determinative as to the liability of Branch and SFM and Minnesota Tool and Indiana Insurance for the proposed disc replacement and fusion procedures.  As such, we need not address the judge’s decision that the proposed surgery is not reasonable or necessary treatment for the employee’s low back condition.  The judge’s denial of the employee’s request for approval of surgery is affirmed.

The compensation judge also denied all other claimed treatment expenses, including the claims of the intervening providers and Blue Cross/Blue Shield.  Presumably, the judge did so based on his conclusion that the claimed injuries were merely temporary.  However, some of the treatment at issue was provided relatively close in time to the employee’s injuries, and there has been no definite determination as to the duration of the temporary aggravations.  We therefore reverse the judge’s denial of these expenses and remand for reconsideration.  The judge may in his discretion require the parties to submit additional arguments or evidence to aid him in resolving the question of liability for the treatment at issue.

This case presents three issues for determination: first, whether the employee’s admitted work injuries were temporary exacerbations of a pre-existing condition; second, whether the medical treatment reflected in the intervention claims and the itemization of payments listed in the exhibit of Blue Cross and Blue Shield of Minnesota is reasonable, necessary and causally related to an admitted work injury; and three, whether the proposed surgery by Dr. Buttermann is reasonable, necessary and causally related to the admitted work injuries.  I concur with the majority’s affirmance of the compensation judge’s determination that the 2008 injuries were temporary exacerbations of the employee’s pre-existing multilevel degenerative disc disease, and further concur with the majority’s affirmance of the judge’s determination on surgery, and with the majority’s reversal and remand of claimed treatment expenses.

However, as to the majority’s decision regarding the determination that the September 16, 2004, work injury was a temporary exacerbation, I disagree.  Based on the analysis below, I would reverse the compensation judge’s finding that the 2004 work injury was a temporary exacerbation as not supported by substantial evidence; or alternatively, I would vacate the compensation judge’s finding that the 2004 work injury was a temporary exacerbation as being outside the scope of the issues at the hearing.

The majority notes that Branch and SFM did not need to allege that payments related to the 2004 work injury were made under a mistake of fact in order to contest continued liability.  While I agree with this part of the majority’s opinion, I believe this not to be the relevant issue.  The majority affirms the compensation judge’s finding that the 2004 work injury was a temporary aggravation.  The majority arrives at this conclusion despite the following uncontroverted evidence: (1) the 2004 work injury resulted in a surgical L3-4 decompression and microdiscectomy; (2) the employee did not reach maximum medical improvement until over two years after the 2004 work injury; (3) medical expenses paid by SFM were over $24,000.00; (4) SFM paid temporary partial disability benefits and temporary total disability benefits through January 15, 2006; and (5) SFM paid eighteen percent permanent partial disability after MMI and surgery.   I disagree with the majority based on the substantial evidence submitted in the record, and I would reverse the finding that the 2004 work injury was a temporary aggravation.

Additional background taken from the record is necessary to analyze whether substantial evidence supports the compensation judge’s finding.  On September 16, 2004, the employee was turning over a three by three foot steel plate that weighed over 70 pounds.  The plate “moved too quickly” and when the employee tried to stop it, he felt a sharp pain in his low back, heard a pop, and “progressively had pain after that.”^[7]  The employee reported the incident to his supervisor that day.  On October 8, 2004, the employee returned to Dr. Rehder, reporting nagging, aching pain in his low back radiating bilaterally.  Dr. Rehder recommended physical therapy and restrictions of no lifting over ten pounds, no bending, twisting, kneeling or squatting.  The employee returned to Dr. Rehder’s office in November 2004 and stated that he had not been following the doctor’s restrictions.  On October 12, 2004, the employee treated with Dr. Nagib, reporting a progression of pain into the right leg and some prior left leg pain.  Dr. Nagib noted symptoms consistent with an S-1 radicular component and recommended physical therapy and medication.  A November 2, 2004, MRI indicated mildly severe central spinal stenosis due to a small to moderate broad based disc herniation with moderate bilateral facet joint hypertrophy at L3-4, moderate severe stenosis due to a small broad based disc bulge with moderate left facet hypertrophy at L4-5, and a small left ventral disc herniation/protrusion causing slight dorsal displacement of the left S1 nerve root.

In January 2005, Dr. Nagib examined the employee and reviewed the November 2, 2004, MRI.  He noted degenerative changes in the lumbar spine, moderate neural foraminal stenosis, but no significant impression on the neural elements.  He indicated that the employee could be treated with a lumbar fusion, but did not recommend fusion surgery for the employee given his age and weight.  Dr. Nagib assigned restrictions of no lifting over twenty pounds, minimal bending, and no repetitive motion.  The employee continued to work his regular job despite the restrictions and “avoid[ed] any excessive lifting.”^[8]

On June 6, 2005, the employee treated with Dr. Davies, who recommended epidural steroid injections.  Another MRI scan was performed on September 21, 2005, which indicated a decrease in the disc extrusion at L3-4.  Dr. Davies reviewed the MRI and noted that the L3-4 disc herniation was smaller than in 2004, but that there was significant herniation and bilateral facet hypertrophy producing canal stenosis and that surgery was appropriate.  On November 21, 2005, the employee underwent a L3-4 decompression and microdiscectomy on the left, performed by Dr. Davies.  The employee reported improvement in his symptoms after the surgery.

Branch and SFM admitted liability for the September 16, 2004, work injury and paid for the employee’s November 2005 L3-4 decompression and microdiscectomy together with other medical expenses, which totaled $24,894.95 by May 2007.  In addition, Branch and SFM paid temporary partial disability benefits from October 22 through November 7, 2004, and temporary total disability benefits from November 21, 2005, through January 15, 2006.  Dr. Davies released the employee to return to regular duty work with no restrictions on January 18, 2006.  The employee was also assigned an eighteen percent permanent partial disability rating under Minn. R. 5223.0390, subp. 4E, based on the health care provider report from United Neurosurgery Associates.  Branch and SFM paid the eighteen percent permanency in accordance with the Minnesota workers’ compensation permanent partial disability schedule.  Branch and SFM assert that the employee reached maximum medical improvement for the 2004 injury as of November 21, 2006.  Final payment was issued on April 30, 2007.

The employee filed a claim petition seeking approval for the proposed surgery on August 6, 2010.  Branch and SFM filed an answer contending that (a) all due and owing workers’ compensation benefits causally related to the 2004 work injury had been paid; and (b) the employee had reached maximum medical improvement for the 2004 work injury by November 21, 2006.  Branch and SFM denied that the 2004 work injury was a substantial contributing factor of the employee’s current disability and need for current medical treatment.

Fact findings are clearly erroneous if the reviewing court, looking at the entire evidence, is left with a definite and firm conviction that a mistake has been committed.^[9]  In the present case, the judge’s finding that the 2004 work injury is a temporary exacerbation is clearly erroneous based on the additional facts stated above.  These uncontroverted facts regarding the 2004 injury are: first, the mechanism of the injury; second, the consistent medical treatment after the injury resulting in excess of $24,000.00 in medical expenses including surgery; third, the significant time off from work, wage loss, work restrictions, and a two year healing period to reach maximum medical improvement; and fourth, the eighteen percent permanent partial disability.  These facts are clearly substantial evidence in the record that compel a determination that the 2004 work injury was a permanent injury.  Therefore, I would reverse Finding 22 as clearly erroneous and unsupported by substantial evidence in view of the entire record as submitted as related to the 2004 work injury.

In the alternative, I would vacate the compensation judge’s finding that the 2004 injury was a temporary exacerbation because the judge went beyond the scope of the issues raised by the parties.  This issue was never raised in the pleadings or specifically at hearing.

The employee filed a claim petition under Minn. Stat. § 176.271 seeking approval for back surgery and preserving future rehabilitation benefits.  Surgery and rehabilitation benefits were additional benefits above and beyond those paid in the past by SMF.  Branch and SMF served and filed an answer pursuant to Minn. Stat. § 176.321 admitting the allegations contained in paragraphs 1, 2, 3, 4, 6, 7, 8, 9, and 12 of the employee’s claim petition.  Paragraph V of the answer reads as follows:

This answering employer and insurer affirmatively allege:

The issue at hearing was whether the 2004 injury remained a substantial contributing cause to the employee’s medical condition and need for surgery.  The employee claimed the admitted 2004 injury was a substantial factor in causing the employee’s present condition and need for surgery; and therefore, the nature and extent of the injury formed the basis of the claim.  Branch and SFM asserted that the nature and extent of the injury in 2004 did not establish a basis for the claim because the 2004 injury was not a substantial cause of the employee’s present condition and need for surgery.^[12]  Branch and SFM submitted defenses that covered the nature and extent of the injuries as it related to the medical treatment and request for surgery and that covered the reasonableness, necessity, and causal relationship of the medical treatment.  The judge was not asked to determine whether the 2004 injury was a temporary aggravation.

The issue of whether the 2004 injury was a temporary aggravation was not within the scope of the issues raised at hearing. This court has held that the compensation judge is limited to the issues raised by the parties in the pleadings and agreed to at the hearing.^[13]  In this case, the judge was limited to a determination of whether the surgery recommended was reasonable, necessary and causally related to the 2004 injury and whether certain intervenors were entitled to reimbursement for medical treatment within specific time periods.  The pleadings did not raise an affirmative defense of a temporary aggravation or payment under mistake of fact.  Nor did the parties agree to expand the issues beyond those set out in the pleadings.^[14]  Based on the pleadings, the transcript of the hearing, and the evidence in the record, I would partially vacate Finding 22 as being outside the scope of the issues at the hearing.