Seagate Technologies, Inc., and its insurer appeal from the compensation judge’s decision that the employee sustained a compensable injury on March 1, 2001, that the employee’s August 2008 surgery was reasonable, necessary, and causally related to the 2001 injury, and that equitable apportionment is not appropriate.  We affirm.

The employee has an extensive history of low back symptoms and treatment dating back to at least February 17, 1981, when he sustained a work-related low back injury while lifting a heavy panel in his job with Rosemount Office Systems [Rosemount].  Following this injury, the employee received treatment, primarily at the Airport Medical Clinic, for nearly two years.  Physicians initially diagnosed a low back strain; a CT scan performed in April of 1981 revealed a bulging disc at L4-5 on the left.  Lifting restrictions were recommended, and permanent partial disability ratings ranged from 10% to 15% of the back.  The employee was evidently transferred to another department at Rosemount to accommodate his restrictions.  In September of 1982, Rosemount submitted an application for registration of the employee’s physical impairment, which was accepted the following year.  Medical records attached to the application classified the employee’s condition as a chronic strain.

The employee left Rosemount in late 1982 or early 1983 to pursue other job opportunities, working over the next eight years first as a bartender and then as a sanitation worker on a recycling truck.  He testified somewhat inconsistently as to whether he continued to experience significant low back symptoms while working at these jobs, but he indicated on a 1987 employment application that he had had no low back problems for more than five years, and he passed the pre-employment physical examination.^[1]  He testified that he also continued to engage in numerous sports and leisure activities during this period.

In February of 1991, the employee began working for Seagate Technologies [Seagate], a technology manufacturing company.  The work was light and the employee apparently had no back problems for more than a year after starting this job.  Then, in July of 1992, he experienced severe low back and leg pain while playing golf.  He first sought treatment for these symptoms about a week and a half later - - the first treatment for his low back condition in nearly ten years.^[2]  He underwent his first low back surgery shortly thereafter, on July 29, 1992, a discectomy at L5-S1 on the right.

The employee continued to work for Seagate and sustained several injuries or aggravations over the next eight or nine years, some apparently work-related, some not.^[3]  During this same period, he underwent three additional back surgeries: a redo hemilaminectomy with excision of disc fragments at L5-S1, performed on September 12, 1996; a bilateral decompression at L4-5 and a decompression on the right at L5-S1, performed on May 11, 1998; and a discectomy and fusion at L4-5 and L5-S1, performed on June 16, 1999.  The employee testified that, within a few months of the 1999 fusion, he had no problems with his back, that he thought he was “cured.”  He also testified that he subsequently worked substantial overtime in his job with Seagate and that he was able to perform his usual activities without difficulty.

On March 1, 2001, the employee experienced severe right-sided low back and right leg pain while bending over at work to put on booties, or shoe covers, which he was required to wear when entering the “clean room.”  Conservative treatment failed to alleviate his symptoms, and, on April 18, 2001, he underwent his fifth low back surgery, a discectomy at L3-4, with removal of hardware used in the prior fusion procedure.  Following this surgery, the employee apparently worked intermittently.  Seagate and its insurer admitted liability for the March 1, 2001, injury and paid various benefits.

The employee underwent a sixth low back operation on June 23, 2004, a discectomy at L2-3.  Later that year, Dr. David Holte, the employee’s surgeon, recommended that he not return to work at Seagate.  In January of 2005, the employee began receiving Social Security disability benefits.  A seventh low back procedure was performed on October 5, 2005, this time an anterior discectomy and fusion at L3-4.

In early 2006, the employee and Seagate entered into a stipulation for settlement, wherein the employee settled all claims relating to the March 1, 2001, injury, except claims for medical expenses.  In the stipulation, Seagate acknowledged that the employee had sustained “a personal injury to his spine in the course and scope of his employment” on March 1, 2001, and both parties agreed that the employee had been permanently and totally disabled since May 5, 2004, with $25,000 in permanent total disability benefits paid as of March 28, 2005.  The agreement also provided that Seagate “reserve[d] all rights and defenses in this matter.”  An award on stipulation was issued on March 1, 2006.

On October 11, 2006, the employee underwent his eighth low back surgery, a posterior fusion and bilateral decompression at L3-4.^[4]  This procedure was apparently unsuccessful in relieving the employee’s pain, and, in the fall of 2007, the employee attempted suicide.  Following an administrative decision, Seagate paid for treatment related to this incident.

The employee testified that the pain and weakness in his legs became intolerable and, consequently, he underwent his ninth back surgery on August 28, 2008, an anterior fusion from T10 to L3, again performed by Dr. Holte.  He testified that his pain improved considerably following this operation.

The matter came on for hearing before a compensation judge on July 22, 2009, for consideration of the employee’s request for payment of medical expenses related to his 2008 low back surgery and Seagate’s petition for contribution and/or reimbursement from Rosemount.^[5]  Issues included whether Seagate was precluded by the terms of the stipulation from denying primary liability for the March 1, 2001, injury; if not, whether the employee sustained a compensable injury on that date; whether Seagate was entitled to contribution and/or reimbursement from Rosemount; and whether the employee’s 2008 fusion surgery was reasonable, necessary, and causally related to the employee’s work injury or injuries.  Evidence included the employee’s testimony, his voluminous treatment records, and opinions from Dr. Holte, Dr. Terry Hood, Dr. Robert Barnett, Dr. Paul Arbisi, Dr. Paul Cederberg, and Dr. Nolan Segal, who also testified by deposition, post-hearing.  Following that deposition, Seagate requested but was denied the opportunity to obtain and submit testimony or another report from Dr. Hood.

In a decision issued on October 9, 2009, the compensation judge concluded that the employee had sustained a permanent, compensable injury to his low back on March 1, 2001, while employed by Seagate; that the employee’s 1981 injury at Rosemount was not a substantial contributing cause of the employee’s disability or need for the medical treatment at issue, and that the employee’s 2008 surgery was reasonable, necessary, and causally related to the March 1, 2001, injury.  Seagate was therefore ordered to pay the disputed medical expenses, with no contribution or reimbursement from Rosemount.  Seagate 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 (2008).  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).

“[A] decision which rests upon the application of a statute or rule to essentially undisputed facts generally involves a question of law which [the Workers’ Compensation Court of Appeals] may consider de novo.”  Krovchuk v. Koch Oil Refinery, 48 W.C.D. 607, 608 (W.C.C.A. 1993).

At hearing, the compensation judge indicated that he would leave the record open to allow Rosemount to depose its expert, Dr. Segal, in part for questioning about the effects of two other injuries allegedly sustained by the employee while he was working for Seagate.  On appeal, counsel for Rosemount and Seagate agree that, off the record, Seagate’s counsel asked the compensation judge for the opportunity to obtain another report or testimony from Seagate’s expert, Dr. Hood.  The judge apparently denied Seagate’s request at that time.

Following the deposition of Dr. Segal, which took place less than a week after the hearing,^[6] counsel for Seagate again requested permission to obtain an additional report or testimony from Dr. Hood.  Rosemount objected and, in his decision on the merits of the substantive issues, the compensation judge denied Seagate’s request.  On appeal, Seagate contends that the judge’s ruling prevented Seagate “from preparing a complete defense to all claims.”  We find no error in the judge’s decision on this issue.

We note initially that Seagate failed to make its arguments on the record when the issue came up initially at the start of the hearing.  As such, with respect to the judge’s initial ruling, at hearing, there is nothing for this court to review.  Moreover, in its post-hearing request to the judge, Seagate seemed to be arguing primarily that an additional opinion from Dr. Hood was necessary to address the other alleged injuries at Seagate.  Because the judge concluded, in the end, that those alleged injuries did not contribute to the employee’s disability, it is hard to see any prejudice to Seagate on that account.

We would also note that it was Seagate, not Rosemount, that was seeking contribution, and it was therefore Seagate that had the burden of proof.  As such, Seagate had no need to prepare a “complete defense” as to causation or contribution.  And, in post-hearing correspondence, Seagate noted that Dr. Hood would not be able to issue an addendum report until mid-September at the earliest, nearly two months after the hearing, potentially further delaying disposition of the claims.  And, had the judge granted Seagate’s request for an additional report from Dr. Hood, Rosemount had asked to be allowed another report from Dr. Segal, to respond to the newest report from Dr. Hood.  At some point, litigation must end, and the record must close.  Finally, and importantly, Dr. Hood had already issued two detailed reports about the primary matters in controversy, explaining, among other things, his disagreement with the conclusions expressed in Dr. Segal’s reports.

Evidentiary rulings are generally within the sound discretion of the compensation judge.  See, e.g., Ortiz v. State, Bemidji State Univ., 58 W.C.D. 13 (W.C.C.A. 1998).  Seagate had ample opportunity to obtain expert opinion on the issues of causation and apportionment as between the employee’s 1981 injury at Rosemount and the employee’s 2001 injury at Seagate.  The judge’s evidentiary ruling is therefore affirmed.

The compensation judge concluded that the employee had sustained a permanent, compensable work injury on March 1, 2001, while employed by Seagate, “in the nature of a herniated disc at L3-4 superimposed upon the multi-level degenerative disc disease and the effects of four prior non-work-related spinal lumbar surgical procedures.”  The judge further determined that the March 1, 2001, injury was a substantial contributing cause of the employee’s need for the disputed medical treatment, including the 2008 surgery.  In his memorandum, the judge also concluded that, given the terms of the parties’ 2006 stipulation, Seagate was precluded from denying primary liability for the March 1, 2001, injury, absent vacation of the award.

On appeal, Seagate argues that the judge erred both in his conclusion as to the effect of the stipulation and in finding that the 2001 injury arose out of the employee’s employment.  We are not persuaded.

Seagate concedes that it initially admitted liability for a March 1, 2001, low back injury and paid substantial benefits related to the employee’s subsequent disability, and Seagate also specifically acknowledged the occurrence of a March 1, 2001, work-related injury to the employee’s spine in the parties’ 2006 stipulation for settlement.  Seagate contends, nevertheless, that, because the stipulation also includes a provision whereby Seagate expressly reserved “all defenses,” Seagate has the right to maintain a retroactive denial of primary liability without first obtaining vacation of the award.  We disagree, in that Seagate’s construction of the stipulation renders meaningless the provision in which Seagate acknowledged that the employee had sustained a compensable back injury on March 1, 2001.  That is, except for purposes of future claims by the employee, Seagate had no reason whatsoever to admit the occurrence of the 2001 injury.  Furthermore, none of the other provisions in the settlement agreement even suggest that Seagate was reserving the right to deny primary liability for future claims.  On the contrary, when read as a whole, the stipulation clearly envisions Seagate’s continued liability for future medical treatment as long as that treatment is reasonable, necessary, and causally related to the employee’s March 1, 2001, “spine injury.”^[7]

There is only one way to give meaning to all of the provisions in the settlement, and that is to interpret Seagate’s reservation of “all defenses” to apply only to matters not specifically conceded by Seagate in the agreement.  The compensation judge therefore correctly determined that Seagate was barred, by the terms of the settlement, from denying primary liability for the March 1, 2001, injury.^[8]

The parties submitted a massive amount of evidence relevant to the issues of medical causation and apportionment, including apparently all of the employee’s extensive treatment records from 1981 onward, and opinions from Drs. Holte, Segal, and Hood.^[9]  Both Dr. Holte and Dr. Hood concluded that the employee’s 1981 injury at Rosemount was a substantial contributing cause of the employee’s disability and need for the medical treatment at issue.^[10]  Dr. Segal, on the other hand, testified that the employee’s 1981 injury was, at most, a temporary strain, which would have resolved within months, and he apportioned no responsibility for the employee’s later low back treatment to that injury.  The compensation judge concluded that the employee’s 1981 work injury was not a substantial contributing cause of the employee’s subsequent low back surgeries and disability after the 2001 injury, and he held Seagate solely responsible for the benefits at issue.

On appeal, Seagate argues initially that, because Rosemount paid permanent partial disability benefits and applied for registration of the employee’s impairment^[11] following the 1981 injury, the compensation judge erred as a matter of law in concluding that that injury was not permanent and did not contribute to the employee’s subsequent disability.  The gist of Seagate’s argument on this issue is that registration is the equivalent of a judicial determination as to the permanent nature of the registered condition.  However, this is simply not the case.  Just as importantly, the question of whether an injury is permanent is separate from the question of whether that injury substantially contributes to an employee’s disability and need for treatment in any given period.  The fact that the employee’s impairment was registered after the 1981 injury may constitute some evidence that the employee’s impairment was permanent, but, standing alone, that registration says nothing about whether the 1981 injury was a substantial contributing cause of the employee’s disability after the 2001 injury.^[12]

Seagate also contends that substantial evidence does not support the judge’s decision that the 1981 injury was not permanent and did not substantially contribute to the employee’s disability and need for treatment following the 2001 injury.  We are also unpersuaded by this argument.

We note at the outset that the compensation judge made no express finding that the 1981 injury was not permanent, only that the 1981 injury was not a substantial contributing cause of the employee’s disability and need for treatment after the employee’s 2001 injury at Seagate.  Again, these are separate questions.  Furthermore, the compensation judge’s decision denying apportionment is supported by both the opinion of Dr. Segal and by some pertinent underlying facts.

It is true that Rosemount paid benefits following the 1981 injury, including benefits for permanent partial disability, and some physicians had recommended that the employee observe permanent lifting restrictions.  However, the employee sought no medical care for low back symptoms, whatsoever, from December of 1982 until July of 1992, a period of nearly ten years.  During this same period, he regularly engaged in leisure and athletic activities including golf, tennis, racketball, league softball, and hunting and fishing, all without any apparent difficulties, until he injured himself playing golf in the summer of 1992.  Furthermore, after he left employment with Rosemount in late 1982 or early 1983, he worked as a bartender and then on a recycling truck, which required some heavy lifting, and he indicated in a 1987 job application that he had not experienced low back problems for more than five years.  Also, as the compensation judge noted, while the CT scan after the 1981 injury showed a disc bulge at L4-5, the employee’s first two surgeries, in 1992 and 1996, addressed abnormalities at the employee’s L5-S1 level, and the employee’s first surgery at L4-5 did not come until 1998 - - 17 years after the 1981 injury.  According to Dr. Segal, the two L5-S1 surgeries would by themselves have led to additional problems.

Factors relevant to the issue of equitable apportionment include the nature and severity of the initial injury, the employee’s symptoms between the initial injury and the second injury, and the period of time between injuries.  Goetz v. Bulk Commodity Carriers, 303 Minn. 197, 226 N.W.2d 888, 27 W.C.D. 797 (1975).  In the present case, it appears to us that the compensation judge reasonably evaluated the evidence in light of these factors, and the opinion of Dr. Segal further supports the judge’s decision.  While the enormous record would also have supported apportionment of liability to the 1981 injury, as well,^[13] that fact is essentially irrelevant given our standard of review.  See, e.g., Giem v. Robert Giem Trucking, 46 W.C.D. 409, 418 (W.C.C.A. 1992) (where the record will support any number of decisions as to apportionment, the Workers’ Compensation Court of Appeals will not substitute its judgment for that of the compensation judge).  We therefore affirm the judge’s decision denying Seagate’s claim for contribution and/or reimbursement.

The employee’s 2008 surgery included an anterior/posterior fusion from T10 to L3.  Both Dr. Segal and Hood were of the opinion that this surgery was a bad idea, for a number of reasons,^[14] and also that the employee’s arguable need for the surgery was not causally related to the 2001 injury in any event.  Dr. Holte disagreed, writing as follows on the issue:

On appeal, Seagate contends that the judge erred by failing to specifically address certain case law standards relevant to evaluating the reasonableness and necessity of fusion surgery and by failing to address Seagate’s arguments that the employee should have been required to undergo a psychological examination to determine his fitness for surgery.^[16]

We find no reversible error.  None of the cases cited by Seagate mandates any particular analysis for fusion surgery claims.  Nor is there any case law dictating that compensation judges must address, in detail, all of the specific arguments of the parties.  The opinion of Dr. Holte is easily sufficient to support the judge’s factual conclusion as to reasonableness and necessity, and the judge was entitled to rely on that opinion in making his decision.  See also Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985).  We therefore affirm the judge’s decision on this issue, as well.