SCOTT G. MATYKIEWICZ, Employee, v. GENERAL TIRE and LIBERTY MUT. INS. CO., Employer-Insurer, and DENNY HECKER’S ROSEDALE DODGE and FARM BUREAU MUT. INS. CO., Employer-Insurer/Appellants, and CENTER FOR DIAGNOSTIC IMAGING, Intervenor.
WORKERS’ COMPENSATION COURT OF APPEALS
JULY 21, 2009
CAUSATION - PERMANENT AGGRAVATION. Substantial evidence, including expert opinion and the employee’s testimony regarding increased symptoms and a change in his restrictions, supported the compensation judge’s decision that the employee’s last work injury permanently aggravated the employee’s preexisting low back condition.
TEMPORARY PARTIAL DISABILITY - CALCULATION. Although the employee’s post-injury earnings varied for some of the same reasons that the employee’s pre-injury earnings varied, the compensation judge did not err in awarding temporary partial disability benefits calculated on a week-by-week basis, where the employee was paid on a regular basis, post-injury, and testified that he lost some pay due to the restrictions imposed as a result of his work injury. Week-by-week calculation of temporary partial disability benefits is the preferred method.
APPORTIONMENT - PERMANENT PARTIAL DISABILITY. Where the employer and insurer had argued that the employee’s ratable permanent partial disability remained the same after the employee’s last work injury as it had been before that injury and had submitted medical records in support of that contention, but the compensation judge apparently neglected to consider that argument and instead simply based her apportionment decision on the 20% rating that had been assigned following the employee’s 1977 and 1978 injuries, remand was required for reconsideration and further findings on the issue of apportionment. The issue in claims for apportionment under Minn. Stat. § 176.101, subd. 4a, is not so much what rating was assigned, in the past, to the employee’s preexisting disability but rather the actual extent of the employee’s preexisting permanent impairment.
Affirmed in part, reversed in part, and remanded.
Determined by: Wilson, J., Johnson, C.J., and Stofferahn, J.
Compensation Judge: Cheryl LeClair-Sommer
Attorneys: Charles M. Cochrane, Cochrane Law Office, Roseville, MN, for the Respondent Employee. Joseph G. Twomey, Hansen, Dordell, Bradt, Odlaug & Bradt, St. Paul, MN, for the Respondents General Tire/Liberty Mutual. Thomas L. Cummings, Jardine, Logan & O’Brien, Lake Elmo, MN, for the Appellants.
DEBRA A. WILSON, Judge
Denny Hecker’s Rosedale Dodge and its insurer appeal from the compensation judge’s decisions regarding the nature of the employee’s September 17, 2003, work injury, the extent of the employee’s preexisting permanent impairment, and the method of calculating temporary partial disability benefits. We reverse the judge’s decision regarding the extent of the employee’s preexisting permanent impairment and remand the matter to the judge for reconsideration. The judge’s decision on the remaining issues is affirmed.
The employee has a history of low back injuries and treatment dating back to at least November 2, 1977, when he sustained a work-related injury while employed by Farmers Union. About a year later, on November 11, 1978, he injured his low back again, this time while working for Knapton Tire Company. The employee subsequently underwent extensive diagnostic testing and treatment over the years, including surgeries, laminectomies at L4-5, in January 1979 and April 1982. Then, in March of 1991, the employee injured his back yet again at work, while employed by General Tire Company. Claims related to these three injuries were the subject of several hearings and settlement agreements. At some point following the first two work injuries, the employee was apparently paid benefits for a 20% permanent partial disability of the back.
In 1991, Dr. Richard Koller, the employee’s treating neurologist at the time, recommended permanent restrictions on lifting, bending, twisting, and prolonged sitting or standing, setting the employee’s lifting limit at 20 pounds. The employee testified that, despite these restrictions, he had no significant problem working. He acknowledged, however, that he had some ongoing problems with his low back.
At some point, the employee obtained work as a line mechanic for Denny Hecker’s Rosedale Dodge [Rosedale Dodge], performing what he characterized as heavy repair work on things such as head gaskets, motors, transmissions and automobile rear ends. On September 17, 2003, the employee felt and heard a snap in his low back while bent over to work on the air bag of a minivan, experiencing immediate severe pain in his low back and both legs. He initially sought treatment from his chiropractor. However, when his symptoms failed to improve, the chiropractor referred him to Dr. Thomas Kraemer for further evaluation.
The employee underwent lumbar MRI scans in 2004, 2005, and 2008, all showing degenerative disc disease and/or disc bulges at multiple levels. Although physicians have increased his restrictions, he has been able to continue working. However, he now uses several prescription medications for his low back and leg symptoms, including Vicodin, Darvocet, tramadol, a Lidoderm patch, and prescription-strength ibuprofen.
Following his 2003 work injury, the employee left Rosedale Dodge but continued to work as an auto mechanic. He is paid a salary plus a kind of incentive pay that varies depending on the type of work performed and the amount of time the employee takes to perform a given repair. He apparently received the same kind of incentive pay while employed by Rosedale Dodge.
The matter came on for hearing before a compensation judge on November 5, 2008, for resolution of the employee’s claim for wage loss benefits, medical expenses, and permanent partial disability benefits related to his low back condition. It was stipulated that the employee’s weekly wage at the time of the 2003 work injury was $709.87. Issues included whether the employee’s 2003 work injury was permanent; the extent of the employee’s permanent impairment; apportionment of preexisting permanent partial disability; the employee’s entitlement to temporary partial disability benefits and the appropriate method of calculating those benefits; and the employee’s entitlement to a surgical consultation. Claims relating to the 1977, 1978, and 1991 injuries, except claims for medical expenses, had been closed out by prior settlements or decisions, and, also pursuant to settlement, General Tire’s insurer had agreed to assume responsibility for payment of any medical expenses awarded as a result of these three injuries.
Evidence submitted at hearing included select medical records and causation opinions from Drs. Bruce Peterson, D.C., David Florence, Robert Wengler, and Paul Wicklund. Dr. Wengler and Dr. Wicklund also testified by deposition.
In a decision issued on January 5, 2009, the compensation judge concluded that the employee’s September 2003 work injury had permanently aggravated the employee’s preexisting condition and that the claimed medical expenses, including the requested surgical consultation, were reasonable, necessary, and causally related to the employee’s 1977, 1978, and 2003 work injuries, with liability apportioned 40% to the 1977 injury, 40% to the 1978 injury, and 20% to the 2003 injury. The judge further concluded that the employee had a 22% whole body impairment under the current schedules, in accordance with the opinion of Dr. Wicklund, and that, after apportioning out the employee’s preexisting 20% permanent partial disability of the back, Rosedale Dodge and its insurer were liable for payment of benefits for a 5.8% whole body impairment. Finally, the judge concluded that the employee was entitled to temporary partial disability benefits for the period claimed, calculated on a week-by-week basis. Rosedale Dodge and its insurer appeal.
STANDARD OF REVIEW
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).
1. Nature of the 2003 Injury
Rosedale Dodge and its insurer appeal from the compensation judge’s conclusion that the employee’s 2003 injury permanently aggravated the employee’s preexisting low back condition, contending that the evidence establishes that nothing “happened in 2003 to change the underlying condition of the employee’s lumbar spine” and that the employee’s “functional disability has not increased since 1991.” We are not persuaded.
As noted by the compensation judge, factors relevant to determining whether an injury is temporary or permanent include (1) the nature and severity of the preexisting condition and the extent of restrictions and disability resulting therefrom; (2) the nature of the employee’s symptoms and extent of medical treatment rendered prior to the aggravating incident; (3) the nature and severity of the aggravating incident and the extent of restrictions and disability resulting therefrom; (4) the nature of the employee’s symptoms and extent of medical treatment following the aggravating incident; (5) the nature and extent of the employee’s work duties and non-work activities during the relevant period; and (6) medical opinions on the issue. “Which of these factors are significant in a particular case and the weight to be given to any factor is generally a question of fact for the compensation judge.” Wold v. Olinger Trucking, Inc., slip op. (W.C.C.A. Aug. 29, 1994).
In the present case, it is undisputed that the employee had significant back injuries, treatment, and need for restrictions prior to his 2003 injury at Rosedale Dodge. However, the record reasonably supports the compensation judge’s conclusion that the employee’s symptoms and functional disability were more severe after that injury, in that the employee began to require much more medication to manage his symptoms, his treating physician has recommended that he no longer perform work under the dash of automobiles, he has been referred for a surgical consultation, and the employee testified that he has additional symptoms that had not been present for a number of years prior to the 2003 injury. In addition, three out of the four physicians offering opinions on the issue indicated that the 2003 injury substantially contributed to the employee’s ongoing symptoms, disability, and need for treatment.
Because the record as a whole amply supports the judge’s conclusion that the employee’s 2003 work injury permanently aggravated the employee’s preexisting low back condition, we affirm her decision on that issue.
2. Temporary Partial Disability Benefit Calculation
The parties stipulated that the employee’s weekly wage at the time of his 2003 injury was $709.87, apparently calculated using the statutory 26-week averaging formula because the employee’s weekly pay varied depending on the work performed and the amount of time the employee took to complete a given repair. See Minn. Stat. § 176.011, subds. 3 and 18. At hearing, the employee claimed entitlement to temporary partial disability benefits for the period December 10, 2006, through August 25, 2007, during which he was employed as a mechanic for other employers. Rosedale Dodge and its insurer took the position that temporary partial disability benefits were not payable because the 2003 work injury did not cause any additional functional impairment or need for restrictions. Rosedale Dodge also argued that, even if the employee had been temporarily partially disabled, due to the 2003 injury, for the period in question, the employee’s post-injury wages should be averaged for purposes of the temporary partial disability benefit calculation. The compensation judge rejected both arguments, concluding that the employee was subject to additional restrictions as a result of his 2003 injury and that the week-by-week method of benefit calculation was appropriate. Benefits were awarded on that basis.
On appeal, Rosedale Dodge and its insurer contend that the compensation judge erred by using the week-by-week method of benefit calculation, arguing that, if the employee’s post-injury earnings are looked at “as a whole,” the employee actually had no overall wage loss as compared to his pre-injury wage. Therefore, the argument goes, the averaging method more accurately reflects the employee’s earning capacity.
We are not entirely unsympathetic to Rosedale Dodge’s position. The employee’s pre-injury wage varied because of the incentive system that is apparently a common feature in the automobile repair business. Because his pre-injury wage varied, the 26-week averaging formula was applicable for purposes of determining his weekly wage. Then, following the 2003 injury, the employee moved on to other employment that utilized the same basic method for compensation, providing incentive pay based in part on the kind of work performed and the time the employee took to perform that work. Treating the employee’s post-injury earnings the same as the employee’s pre-injury earnings at least arguably provides the most accurate basis for ascertaining the extent of the employee’s injury-related loss of earning capacity.
At the same time, this argument may be made in virtually every case in which the employee’s earnings fluctuate both pre- and post-injury, and we have nevertheless indicated on several occasions that the week-by-week method for temporary partial disability benefit calculation is preferred and should be used in most cases. Erdrich v. Ford Motor Co., 49 W.C.D. 528, 533 (W.C.C.A. 1993). Using an averaging method for post-injury earnings presents practical difficulties. For example, the accuracy of payment can only be determined sometime after the fact; a post-injury wage history is necessary to establish the applicable “average.” Id. We also agree with the judge that the present matter is distinguishable from some other cases in which the averaging method was used, in that the employee testified that he sometimes lost income when he could not do certain work because of his restrictions. See Nutter v. United Parcel Serv., 58 W.C.D. 183 (W.C.C.A. 1997) (use of the averaging method was appropriate where the employee’s post-injury wage varied based primarily on seasonal variations in the employer’s business). Finally, we note that decisions as to the method of post-injury wage loss calculation are factual in nature and are for the compensation judge to make on a case-by-case basis. Id.; Murphy v. B.F. Nelson, Co., slip op. (W.C.C.A. Oct. 8, 1998).
Again, the week-by-week method of temporary partial benefit calculation is preferred, and, finding no compelling reason to substitute the averaging method here, we affirm the judge’s decision on this issue.
3. Permanent Partial Disability - Apportionment/Causation
Dr. Wengler concluded that the employee’s current condition warrants a 27% whole body rating under the current disability schedules, Minn. R. 5223.0390, subps. 4E, 4E(4), 4E(1), and 4E(2). Dr. Wicklund, on the other hand, rated the employee’s current condition at 22%, pursuant to Minn. R. 5223.0390, subd. 4D, 4D(2), 4D(3), and 4D(4). In her decision, the compensation judge concluded that the employee did not have the stenosis specified by subpart 4E. For that reason, she rejected the opinion of Dr. Wengler and accepted the opinion of Dr. Wicklund, concluding that the employee’s current condition was best rated at 22% under subpart 4D. The judge’s decision on this issue is undisputed on appeal.
On the issue of apportionment for preexisting permanent impairment pursuant to Minn. Stat. § 176.101, subd, 4a, the judge took the 20% rating previously assigned to the employee’s condition following the employee’s first two injuries and converted it to a whole body rating using the tables in the permanent partial disability rules, arriving at a 14.2% whole body rating applicable to the employee’s preexisting impairment. See Minn. R. 5223.0315. The judge then indicated that the 14.2% rating should be subtracted from the employee’s current 22% whole body rating, and she ordered Rosedale Dodge and its insurer to pay the employee benefits for a 5.8% whole body rating.
On appeal, Rosedale Dodge and its insurer argue that the judge erred in determining their liability, in that the employee’s preexisting disability would qualify for a 22% whole body rating under the current rules. As such, they argue, the employee has no more ratable permanent partial disability now than he had prior to the 2003 injury, meaning that they have no liability for permanent partial disability benefits.
We conclude that the matter must be remanded for reconsideration and further findings. Rosedale Dodge and its insurer specifically argued, at hearing below, that the employee’s level of permanent partial disability is no greater now than it was prior to the 2003 injury, and they offered medical records, including scan and surgical reports, sufficient to allow the judge to make that determination. It appears, however, that the judge neglected to consider their argument in this regard, instead simply using the prior 20% rating as if the fact of the prior rating by itself established the extent of the employee’s preexisting impairment. The issue, however, is not what rating may have been assigned to the employee’s preexisting condition prior to the 2003 injury, or even the rating for which the employee received payment. In fact, the rating applicable to the employee’s 1977 and 1978 injuries is not necessarily determinative. Rather, the issue is the actual extent of the employee’s permanent impairment - - from whatever source - - prior to the injury for which apportionment is at issue. See Settlemire v. Innsbruck Health Care Ctr., No. WC08-244 (W.C.C.A. May 18, 2009).
Because the compensation judge apparently failed to consider Rosedale Dodge and its insurer’s argument regarding the true extent of the employee’s preexisting permanent impairment, we reverse the judge’s decision and remand the matter for reconsideration and further findings. If, as Rosedale Dodge and its insurer allege, the employee’s preexisting condition would warrant a 22% whole body rating under the rules, no permanent partial disability benefits are payable. In this regard, the issue may fairly be characterized as one of causation, as much as apportionment. The compensation judge may in her discretion allow the parties to submit additional arguments on this issue.
 Only a limited number of records related to the employee’s first two injuries were submitted as evidence at the most recent hearing. The list of imaged documents is lengthy, but no reference was made at hearing about including any part of the division file in the record. See Minn. R. 1420.2900, subp. 7B(3). This court is limited to reviewing the record as submitted at the trial level. Material that the parties wish to have considered on appeal must generally be submitted as evidence at hearing or incorporated by reference, on the record. Beckwith v. Sun Country Airlines, 63 W.C.D. 511 (W.C.C.A. 2003); Moore v. University of Minn., No. WC07-195 (W.C.C.A. Nov. 30, 2007).
 Minn. R. 5223.0390, subp. 4E, provides as follows:
E. 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 scan evidence of spinal stenosis, as defined in part 5223.0310, subpart 47, that impinges on a lumbar nerve root, and the medical imaging findings correlate with the findings on neurological examination, ten percent with the addition of as many of subitems (1) to (4) as apply, but each may be used only once:
(1) if chronic radicular pain or radicular paresthesia persist despite treatment, add three percent;
(2) if a surgery other than fusion performed as part of the treatment, add five percent, if surgery included a fusion, the rating is as provided in subpart 5;
(3) for additional surgery, other than a fusion, regardless of the number of additional surgeries, add three percent, if additional surgery included a fusion, the rating is as provided in subpart 5;
(4) additional concurrent lesion on contralateral side at the same level or on either side at other level, which meets all of the criteria of this item or item D, add nine percent.
 Minn. R. 5223.0390, subp. 4D, provides as follows:
D. Radicular pain or radicular paresthesia, with or without lumbar pain syndrome, and with objective radicular findings, that is, hyporeflexia or EMG abnormality or nerve root specific muscle weakness in the lower extremity, on examination and myelographic CT scan, or MRI scan evidence of intervertebral disc bulging, protrusion, or herniation that impinges on a lumbar nerve root, and the medical imaging findings correlate anatomically with the findings on neurological examination, nine percent with the addition of as many of subitems (1) to (4) as apply, but each may be used only once:
(1) if chronic radicular pain or radicular paresthesia persist despite treatment, add three percent;
(2) if a surgery other than a fusion performed as part of the treatment, add two percent, if surgery included a fusion, the rating is provided in subpart 5;
(3) for additional surgery, other than a fusion, regardless of the number of additional surgeries, add two percent, if the additional surgery included a fusion, the rating is as provided in subpart 5;
(4) additional concurrent lesion on contralateral side at the same level or on either side at other level, which meets all of the criteria of this item or item E, add nine percent.
 Minn. Stat. § 176.101, subd. 4a, provides:
Subd. 4a. Preexisting condition or disability; apportionment. (a) If a personal injury results in a disability which is attributable in part to a preexisting disability that arises from a congenital condition or is the result of a traumatic injury or incident, whether or not compensable under this chapter, the compensation payable for the permanent partial disability pursuant to this section shall be reduced by the proportion of the disability which is attributable only to the preexisting disability. An apportionment of a permanent partial disability under this subdivision shall be made only if the preexisting disability is clearly evidenced in a medical report or record made prior to the current personal injury. Evidence of a copy of the medical report or record upon which apportionment is based shall be made available to the employee by the employer at the time compensation for the permanent partial disability is begun.
 The judge’s 5.8% rating was clearly the result of an error in subtraction. 22% - 14.2% = 7.8%. The employee did not appeal from the judge’s award, but the arithmetic error may be corrected, if necessary, on remand.
 As indicated earlier, Minn. R. 5223.0315 contains a table applicable to convert old-law impairment ratings to whole body ratings for purposes of apportionment. The rules specify that the table applies to injuries producing permanent impairment prior to January 1, 1984. However, use of the table presumes that the old-law rating is either correct or undisputed. Certainly a subsequent employer and insurer cannot be bound by a rating given in a report, settlement, or decision issued prior to their involvement in the matter.
 For example, two components of the employee’s current overall 22% rating are applicable solely because of the employee’s surgeries in 1979 and 1982. See Minn. R. 5223.0390, subp. 4D(2) and 4D(3). Obviously these surgeries had no relationship whatsoever to the 2003 injury.