RICHARD SNYDER, Employee/Appellant, v. SUBURBAN AIR CONDITIONING and FEDERATED MUT., Employer-Insurer, and SUBURBAN AIR CONDITIONING and AMERICAN HARDWARE, Employer-Insurer, and SUBURBAN AIR CONDITIONING and TRANSPORTATION INS. CO., Employer-Insurer, and HARRIS CO./UNITED TRADES and GALLAGHER BASSET, Employer-Insurer, and GREEN MECHANICAL and MID-CENTURY INS., Employer-Insurer, and NORTHWEST SHEETMETAL and CONTINENTAL WESTERN/BERKLEY ADM=RS, Employer-Insurer, and SHEETMETAL #10 BENEFIT FUND, Intervenor.

 

WORKERS= COMPENSATION COURT OF APPEALS

JANUARY 8, 2002

 

HEADNOTES

 

PERMANENT TOTAL DISABILITY - SUBSTANTIAL EVIDENCE; CAUSATION - PRE-EXISTING CONDITION.  Where there was no evidence that the judge presumed that the work must be the sole cause of an injury for it to be compensable, where there was no evidence that the judge was of the opinion that the employee=s work played no role in his disability and/or restrictions, and where the judge=s decision was supported by expert medical opinion, the compensation judge=s denial of permanent total disability benefits on grounds that the employee=s ongoing disability was caused not by his seven work injuries but by his pre-existing osteoarthritis was not clearly erroneous and unsupported by substantial evidence.

 

WAGES - IRREGULAR; WAGES - CONSTRUCTION INDUSTRY; STATUTES CONSTRUED - MINN. STAT. ' 176.011, SUBD. 3. Where the judge could reasonably have concluded that there was no reliable way to ascertain the employee=s daily wage and therefore no reasonable way to provide the employee with the benefit of the provision applicable to construction workers, and where the alternative method chosen by the judge for determining the employee=s average weekly wage was not unreasonable, the compensation judge=s determination of the employee=s average weekly wage on the date of his injury was neither erroneous as a matter of law nor unsupported by substantial evidence.

 

Affirmed.

 

Determined by Pederson, J., Wilson, J. and Johnson, J.

Compensation Judge:  Carol A. Eckersen

 

OPINION

 

WILLIAM R. PEDERSON, Judge

 

The employee appeals from the compensation judge's conclusion that the employee=s current disability is unrelated to his work injuries and from the judge=s determination of the employee=s weekly wage.  We affirm.

 

BACKGROUND

 

Richard Snyder began receiving continuing treatment for gout in the 1980s.  Over a period spanning five and a half years beginning in December 1988, Mr. Snyder [the employee] sustained four injuries to his knees and right shoulder apparently in the course of his employment as a sheet metal worker with Suburban Air Conditioning [Suburban].  The first of these injuries, on December 20, 1988, was to his left knee, while Suburban was insured by Federated Mutual [Federated].  X-rays showed degenerative changes with probable loose bodies, and orthopedic surgeon Dr. Gary Sager took the employee off work for a week.  On January 17, 1989, Dr. Sager released the employee to work without restrictions.

 

The employee=s second injury with Suburban was also to his left knee, on December 20, 1990, while Suburban was insured by American Hardware [American].  Subsequent to this second injury, the employee underwent an MRI scan on January 15, 1991, which revealed Grade I to II chondromalacia, and the employee was referred back to Dr. Sager, who performed an arthroscopy on February 8, 1991.  Upon arthroscopy, the employee=s medial meniscus appeared by its yellow color to be calcified and degenerated, and Dr. Sager discovered State III to IV chondromalacia and diffuse osteoarthritis, which he concluded was not due to the employee=s work activities.  By June 25, 1991, the employee reported that his left knee was Aperfect@ again, although he was having some pain in his right knee.  On November 8, 1991, the employee was served with Dr. Sager=s opinion that the employee had reached maximum medical improvement with a 1% whole-body permanent partial disability.

 

The employee=s third injury with Suburban was to his right knee, on March 19, 1993, while Suburban was once again insured by Federated.  Subsequent to this third injury, in April of 1993, the employee underwent arthroscopic right knee surgery to repair a meniscal tear, again performed by Dr. Sager.  Dr. Sager=s follow-up notes for May 23, 1993, indicate that the repaired meniscal tear had been a degenerative one and that the employee had severe osteoarthritic changes also in his right knee.  The doctor indicated that the employee was

 

somewhat frustrated since I cannot relate his work comp injury to the severe arthritis at this point.  He states that certainly it is related to doing heavy labor and certainly, there is a wear and tear factor, as well as probably some genetic factor to it.  However, from the recent injury, I cannot relate it to that specifically.

 

The fourth of the employee=s injuries with Suburban was to his right upper extremity, on June 24, 1994, initially the elbow and wrist and eventually the shoulder.  The employee was fifty years old on that date, and Suburban was insured by Transportation Insurance Company [Transportation].  The employee saw first Dr. Robert Hart and then Dr. Sager again, who diagnosed right lateral epicondylitis, carpal tunnel syndrome, wrist tendinitis, and shoulder complaints. Following the injury the employee was off work, and benefits were commenced based on a weekly wage of $902.40, but after one week they were reduced to reflect a wage about a third less than that.  The employee was injected with cortisone and returned to work with restrictions on August 8, 1994, but problems persisted.  On September 27, 1994, an EMG was reported to reveal carpal tunnel syndrome on the right, but the employee=s shoulder symptoms were reported to be even more bothersome.  On November 25, 1994, the employee underwent surgery for repair of a right rotator cuff tear, a partial anterior inferior acromioplasty, and a modified Mumford procedure with a distal clavicle resection.  He was ultimately paid 62.4 weeks of temporary total disability benefits and never returned to work for Suburban.  Dr. Sager was continuing the employee=s restriction in September 1995, but the December 11, 1995, treatment notes of Dr. Philip Hoversten record the employee=s report that he had been released to regular duty by Dr. Sager, and Dr. Hoversten=s Report of Work Ability of that same date reflect no continuing shoulder-related restrictions other than the wearing of in immobilizer.  Eventually the employee apparently returned, on January 8, 1996, with rehabilitation assistance, to work with another sheet metal company.

 

In the years following his employment and injuries with Suburban, the employee alleged three more work-related injuries, with three other employers.  On November 18, 1997, he sustained an injury to his left ankle, left knee, left shoulder, and low back when he fell from a ladder while employed with Harris Co./United Trades [Harris], which was at that time insured against workers= compensation liability by Gallagher Bassett [Gallagher].  X-rays of his left knee and low back on December 8, 1997, revealed advanced degenerative changes in the left knee and prominent spondylolysis at L5 with stage 1 spondylolisthesis at L5-S1 and degenerative changes at L3-4, and the employee was off work for 2.4 weeks.  On March 18, 1998, Dr. Daniel Goldblatt concluded that the employee=s November 18, 1997, low back, left knee, and left ankle injuries were work related and were unaffected by any preexisting condition.  But he concluded also that the employee had reached maximum medical improvement [MMI] with regard to those injuries on January 12, 1998, without any permanent partial disability and could return to work without restrictions.  On June 4, 1998, Dr. Goldblatt concluded also that the employee now had full range of motion in his left shoulder, with pain-free and normal rotation against resistance.  The doctor indicated also on that date that the employee=s also problematic left elbow now had full extension, flexion, supination, and pronation and that his left wrist now had Anormal and strong@ flexion and extension.  On those findings, Dr. Goldblatt equipped the employee with a wrist splint and released him to full duties with regard to those conditions as well.

 

Subsequent to his injury with Harris, the employee worked for Green Mechanical [Green], with whom he alleged sustaining injuries to his left shoulder, left elbow, left wrist, left hand, and right ankle on May 26, 1998, in the course of hand-crafting sheet metal products with out-of-date equipment.  Green was insured at that time by Mid Century Insurance [Mid Century].  The employee sought treatment for his symptoms from Dr. Sean Flood, who concluded that the employee=s underlying problem was not work related but rather was due to Asome sort of a rheumatological problem involving the joints,@ although Ahis work could possibly aggravate the condition.@  The employee was referred for follow-up with Dr. Goldblatt, who diagnosed mild left rotator cuff tendinitis, mild bursitis, and tendinitis of the left elbow and wrist.  Dr. Goldblatt prescribed medications and took the employee off work for a week.  The employee stayed off work for about two weeks.  Upon Dr. Goldblatt=s release to return to full duties, the employee returned to Green, which terminated his employment.

 

The employee subsequently went to work with Northwest Sheetmetal [Northwest], against which he alleged an apparently Gillette-type work injury to his knees and low back with onset of symptoms on September 18, 1998.  Northwest was insured at that time by Continental Western/Berkley Administrators [Continental].  X-rays on September 28, 1998, revealed degenerative changes but no significant change since the December 8, 1997, x-rays.  Dr. Goldblatt concluded that the employee=s left knee symptoms were due to gout and prescribed medication.  With regard to his back symptoms, the employee underwent a lumbar MRI scan on October 16, 1998, which revealed bilateral spondylolysis defects and spondylolisthesis at L5-S1, with moderately severe to severe left nerve root canal stenosis and moderate right nerve root canal stenosis, with possible impingement on the left L5 nerve root.

 

The employee was referred to orthopedist Dr. David Lindgren and to spine specialist Dr. David Kraker.  The employee first saw Dr. Lindgren on November 2, 1998, and Dr. Kraker on December 4, 1998.  Dr. Lindgren diagnosed low back pain due primarily to facet arthritis, with spondylolisthesis and probable spinal stenosis, Abased on the facet arthritis and the spondylolisthesis together.@  Dr. Lindgren diagnosed also osteoarthritis and gout in the knees, with acute inflammation on the right, and gout in the right MTP joint.  Dr. Kraker diagnosed spondylolisthesis, foraminal stenosis, and a small herniated disc at L5-S1 of the employee=s back, finding also degenerative disc disease at L2-3, L4-5, and L5-S1, with mild right scoliosis.  Dr. Kraker referred the employee for physical therapy and a nerve root block, and he restricted the employee from working for three months.

 

The employee apparently last worked as a sheetmetal worker in September of 1998.  On December 7, 1998, he filed a claim petition, alleging entitlement to temporary total disability compensation continuing from September 28, 1998, as well as to statutory rehabilitation benefits, consequent to work injuries in December 1990, March 1993, June 1994, November 1997, May 1998, and September 1998.  A January 11, 1999, discography ordered by Dr. Kraker indicated concordant pressure and pain from L3 through S1 of the employee=s back, and Dr. Kraker noted that the employee had a full thickness anterior and posterior annular tearing at L2-3 and L1-2.  The doctor concluded, however, that the employee was a poor surgical candidate.  On January 27, 1999, Dr. Lindgren performed a total arthroplasty on the employee=s right knee.  On February 2, 1999, the employee amended his claim petition to allege entitlement also to retraining benefits under Minn. Stat. ' 176.102.  On March10, 1999, Dr. Kraker extended the employee=s restriction from working until June of 1999.

 

On March 22, 1999, the employee was examined for Suburban/American by orthopedist Dr. Paul Cederberg, with specific reference to the employee=s left knee injury of December 1990.  In his report on that date, Dr. Cederberg rendered opinions that, in light of the overriding impact of the employee=s low back and right knee conditions and the severity of his preexisting osteoarthritis in the left knee, the employee=s December 1990 left knee injury was not a substantial contributing cause of his current temporary total disability, of his medical expenses or need for retraining since June 1991, or of his current needs for left knee replacement and rehabilitation assistance.  Dr. Cederberg also opined at that time that fifty percent of the employee=s low back, left knee, ankle, and shoulder conditions were attributable to the employee=s November 1997 injury, but at his subsequent deposition on February 19, 2001, Dr. Cederberg testified to a revised opinion, that none of those conditions was causally related to that injury.

 

On April 27, 1999, the employee was examined for Northwest/Continental by orthopedist Dr. David Boxall, with specific reference to the knee and back injury of September 1998.  In his report on that date, Dr. Boxall diagnosed in part a history of gout and degenerative arthritis involving multiple joints including foot and hip.  After first concluding that the employee=s November 1997 low back and left lower extremity and shoulder injury had also been only temporary, a flare-up of underlying spondylolisthesis at L5-S1 that had essentially resolved by December 15, 1997, Dr. Boxall opined that there was no evidence to support an injury to the left knee in September 1998, in that findings on evaluation after that injury were consistent instead with gout.  Nor was there, the doctor concluded, any evidence that the employee=s September 1998 work activities played any role in his current right knee complaints or participating in causing any injury to his low back.  It was ultimately Dr. Boxall=s opinion that none of the employee=s work injuries played any part in his overall current inability to work - - that A[the employee=s] injuries consisted of a strain to the low back area which resolved and a flare-up of some underlying degenerative arthritis of the right and left knee and degenerative lateral meniscus tear of each knee.@^[1]

 

On April 28, 1999, the employee was examined for Green/Mid Century by orthopedist Dr. Larry Stern, with specific reference to the employee=s left shoulder and upper extremity and right ankle injuries of May 1998.  In his report on that date, Dr. Stern concluded that no objective problem existed regarding the employee=s left shoulder or left upper extremity, that the employee still required treatmentBmost likely total knee replacement--for his left knee, and that Anone of the [employee=s] current wage loss, medical expenses and permanent partial disability relates to any injury that he sustained at Green Mechanical in May or June of 1998,@ in part because Athe [employee=s] history given on this date is that his left arm complaints are not keeping him or limiting him from work.@

 

On May 25, 1999, the employee was examined for Suburban/Federated by orthopedic surgeon Dr. Mark Engasser, with specific reference to the employee=s left and right knee injuries of December 1988 and March 1993, respectively.  In reports issued May 25 and November 1, 2000, Dr. Engasser rendered an opinion that, while the employee did sustain permanent aggravations of preexisting degenerative conditions in December 1990, March 1993, and June 1994, the injury in December 1988 was only a temporary aggravation and Athe injury in 1993 is not at all related to any of [the employee=s] [current] orthopedic conditions including his low back condition, left knee condition, shoulder condition or other upper extremity condition.@

 

In treatment notes on June 4, 1999, Dr. Kraker indicated that he considered the employee a candidate for back surgery, but he recommended that the employee lose weight and have his left knee repaired before considering that option.  On August 25, 1999, Dr. Lindgren performed a total arthroplasty on the employee=s left knee, as he had earlier performed on the right, and on December 9, 1999, he restricted the employee to sedentary work.  On October 29, 1999, Dr. Kraker, referred the employee to physical therapy for back-stabilization exercises and released the employee to return to work four to six hours a day at light duty, recommending Afull evaluation by a psychiatrist@ for depression prior to considering any surgical treatment because the employee was Anot a surgical candidate at this point.@  Dr. Kraker did not render an opinion as to the cause of the employee=s low back complaints. 

 

On February 9, 2000, the employee was examined by Dr. Jack Bert, at the request of his own attorney.  By a report on that same date, Dr. Bert rendered opinions in part as follows: (1) that  in December 1988 and December 1990 the employee sustained permanent aggravations  of a preexisting osteoarthritic condition in his left knee; (2) that the employee had an 8% whole-body impairment in that knee, a third due to the 1988 injury, a third due to the 1990 injury, and a third due to the preexisting condition; (3) that the employee had an 8% whole-body impairment also in his right knee, 50% due to his March 1993 accident and 50% due to his preexisting condition; (4) that the necessity of the employee=s surgery on his right shoulder in June 1994 was due to a work-related permanent aggravation of a preexisting condition 50% due to his employment and that the employee was subject to a 6% whole-body impairment as a result of that aggravation; (5) that the employee=s November 1997 low back and left knee injury resulted in a permanent aggravation of a preexisting condition, the employment being responsible for 50% of the employee=s low back condition and the low back injury constituting a 7% whole-body impairment; (6) that 75% of the employee=s May 1998 bilateral carpal tunnel syndrome was due to his May 1998 hand and wrist injury and that that injury had resulted in a 3% whole-body impairment related to each wrist; (7) that the employee=s September 1998 low back work injury constituted a permanent aggravation that was responsible for about 25% of his chronic lumbar spine condition.

 

On May 1, 2000, the employee was evaluated for Harris/Gallagher by orthopedist Dr. H. William Park, with specific reference to the employee=s injury of November 1997.  In a report dated that same day, Dr. Park rendered an opinion that the employee was subject to Aa diffuse osteoarthritis type of condition of systemic nature that affects both knees as well as lower lumbar spine.@  Dr. Park concluded that the employee=s Asymptoms of degenerative changes accelerated after the work injury dating back to December 20, 1990,@ but that

 

the work activities that occurred in 1997 did not contribute to the ongoing degenerative joint disease as well as initial acceleration of the degenerative process that occurred [i]n December 1990.  The work injury in November 1997 was a temporary aggravation of the preexisting condition resulting in ankle sprain as well as aggravating temporarily the degenerative joint disease of the left knee.

 

Dr. Park indicated that the employee=s shoulder condition also was a degenerative condition, Athat was significantly aggravated by the work injury dating back to January 1994" and that Athere was no injury that occurred permanently as the result of the November 1997 work injury.@ 

 

On May 25, 2000, Dr. Lindgren confirmed his recommendation that the employee should do only sedentary work, indicating, however, that he could Aadvance as tolerated.@  The doctor did not restrict the number of hours a day that the employee could work.  The employee=s union, intervenor Sheetmetal #10 Benefit Fund, has paid a total $43,210.29 in medical benefits and $12,999.93 in disability benefits for the period from September 28, 1998, through April 4, 1999.

 

Beginning in October 2000, the employee searched for work without rehabilitation assistance.  In a letter to the employee=s attorney dated October 25, 2000, Dr. Bert indicated that the employee=s activity with regard to his knees, his right shoulder, his carpal tunnel syndrome, and his low back should be restricted.  With regard to the knees, Dr. Bert indicated that the employee should Adefinitely@ avoid any crawling, climbing, kneeling, stooping, prolonged standing or sitting, and lifting over ten pounds.  With regard to the right shoulder, Dr. Bert indicated that the employee should avoid all overhead work, should do virtually no work above shoulder level, and should avoid lifting over five pounds.  With regard to the carpal tunnel syndrome, the doctor indicated that the employee should avoid any repetitive grasping, manipulation, and lifting of over five pounds.  Finally, with regard to the employee=s low back, Dr. Bert indicated that, given the employee=s spondylolisthesis and spondylolysis, the employee should avoid any repetitive bending or stooping, any prolonged sitting or driving maneuvers, and any climbing or lifting of over five pounds.  Eventually, on November 3, 2000, the employee found a security guard job, at which he evidently continues to work.

 

The matter came on for hearing on February 22 and 23, 2001.  Issues at hearing included the compensability, nature, and extent of the employee=s seven alleged injuries with the four defending employers and their six insurers, together with related issues including the employee=s weekly wage at the time of his fourth injury with Suburban.^[2]  By findings of fact, conclusions of law, and order filed May 4, 2001, the compensation judge concluded in part that all of the employee=s seven injuries has been temporary in nature as follows: (1) that the December 1988 injury was a temporary aggravation of preexisting osteoarthritis that had fully resolved by January 17, 1989; (2) that the December 1990 injury had been a temporary aggravation of preexisting osteoarthritis that had fully resolved by June 25, 1991; (3) that the March 1993 injury had been a temporary aggravation of right knee osteoarthritis that had fully resolved by August 11, 1993, and that Dr. Sager=s rating of permanency on the latter date was for a degenerative tear of the meniscus that was not causally related to the employee=s temporary work aggravation; (4) that the June 1994 injury had been a temporary injury of the employee=s right shoulder that had fully resolved by January 8, 1996; (5) that the November 1997 injury had been a temporary aggravation of a preexisting osteoarthritis that had fully resolved by March 18, 1998; (6) that the May 1998 injury had been a temporary injury of the employee=s left rotator cuff, left elbow, and left wrist that had resolved by June 4, 1998; and (7) that the September 18, 1998, injury had been a temporary aggravation of the employee=s knees and low back conditions and that that temporary aggravation had resolved by October 5, 1998. 

 

The judge also concluded in part that the employee had not been permanently totally disabled from September 18, 1998, through February 22, 2001, and continuing as claimed, although he had been temporarily totally disabled from September 18, 1998, through October 5, 1998.  From the latter date through December 9, 1999, the judge concluded, the employee had been temporarily totally disabled due to his nonwork-related preexisting bilateral osteoarthritic knee condition.  The judge found also that the employee had been temporarily totally disabled due to his nonwork-related low back condition from October 5, 1998, through October 29, 1999, when he had been released to work without restrictions.  The judge also found in part that the employee was not entitled to temporary partial disability benefits from November 3, 2000, through February 22, 2001, and continuing as claimed, nor had he sustained a reduction in earning capacity as a result of a work injury, nor were his earnings insubstantial.  The judge found also in part that the employee had returned on January 8, 1996, to work at his regular sheet metal work without restrictions related to his right shoulder injury.  Finally, the judge concluded that the employee=s weekly wage on June 24, 1994, had been $611.65 rather than $902.40 as alleged, based on wage records for the twenty-six-week period preceding that injury.  The employee appeals.

 

STANDARD OF REVIEW

 

In reviewing cases on appeal, the Workers= Compensation Court of Appeals must determine whether Athe 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, Athey 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, A[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, Aunless 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.

 

DECISION

 

In effect, the compensation judge concluded in part that none of the employee=s admitted or alleged work injuries constituted a continuing and substantial contributing factor in the employee=s current potentially permanent total disability.  The judge concluded also in part that the employee=s weekly wage on June 24, 1994, had been $611.65 rather than $902.40 as alleged.

 

1.  Causation

 

With regard to the causation issue, the employee contends that, even granting that the employee=s osteoarthritis may have preexisted rather than been induced by his work injuries, Athe Compensation Judge erred in not considering the affect that Mr. Snyder=s employment activities and related trauma had on his condition and the compensability of his claim.@ He argues that A[s]ubstantial evidence does not support the Compensation Judge=s determination that Mr. Snyder=s work activities and/or his work-related injuries played no role in his disability and/or restrictions.@  We are not persuaded.

 

In support of his position, the employee cites well established case law in arguing that A[c]ontrary to the approach seemingly taken by the Compensation Judge, work activities need not be the sole cause, but need only be a substantial contributing factor to causing or aggravating or accelerating the overall disability in order for the disability to be compensable@ (quoting the employee=s brief).  See Salmon v. Wheelbrator Frye, 409 N.W.2d 495, 497-98, 40 W.C.D. 117, 122 (Minn. 1987); Roman v. Minneapolis Street Railway Co., 268 Minn. 367, 129 N.W.2d 550, 23 W.C.D. 573 (1964).  The employee=s assertion is, of course, correct, but we find no evidence in the judge=s decision that she was presuming otherwise.  Indeed, several of the numerous medical experts whose opinions and records are in evidence made very clear that the employee=s work participated in his initial injury, and the judge herself expressly found work injuries on at least six of the seven dates alleged.  The judge=s concluded, however, that these injuries were temporary aggravations that eventually resolved and did not participate in any permanent total disabilityBin effect, that the employee=s ongoing disabilities would have evolved to their present state even without the work-related aggravations.  This conclusion by the judge was not unreasonable, in light of the substantial medical records and opinions in evidence.

 

Nor do we find any evidence that the judge was necessarily of the opinion that the employee=s Awork activities and/or his work-related injuries played no role in his disability and/or restrictions.@  In order for compensation to be due, the work must be not just a contributing factor but a Asubstantial@ contributing factor in the disability at issue.  Id.  In this case the judge found that not to be the case.  With regard to the employee=s early left and right knee injuries with Suburban, the judge=s conclusion is substantially supported not only by Dr. Engasser=s May 25 and November 1, 2000, independent medical examination [IME] reports and Dr. Cederberg=s March 22, 1999, and February 19, 2001, IME reports, but also by the records of Dr. Sager and that doctor=s notation that the employee himself had reported at least his left knee to be returned to Aperfect@ condition already by June 25, 1991.  With regard to the employee=s 1994 right upper extremity injury, the judge=s conclusion is substantially supported by Dr. Hoversten=s December 11, 1995, treatment notes and Report of Work Ability, which record the employee=s report that he had been released by Dr. Sager to regular duty and which reflect no continuing right shoulder related restrictions. With regard to the employee=s 1997 left ankle and knee and low back injuries, the judge=s conclusion is substantially supported by Dr. Goldblatt=s March 18, 1998, conclusion that the employee could return to full duties.  With regard to the employee=s left shoulder injury and his reinjury of it in May 1998, along with his left elbow, left wrist, left hand, and right ankle, the judge=s conclusion is supported not only by Dr. Goldblatt=s June 4, 1998, release of the employee to full duties with regard to those conditions but also by Dr. Stern=s April 28, 1999, IME report.  Finally, with regard to the employee=s September 1998 knees and low back injury, the judge=s conclusion is substantially supported both by Dr. Boxall=s April 27, 1999, IME report and by Dr. Cederberg=s March 22, 1999, IME report and his February 19, 2001, deposition testimony.

 

Dr. Bert rendered opinions essentially to the contrary, but, absent any clear challenges to the foundation for the opinions, the judge=s apparent decision to credit other medical opinion over the opinions of Dr. Bert was not unreasonable.  See Nord v. City of Cook, 360 N.W.2d 337, 342-43, 37 W.C.D. 364, 372-73 (Minn. 1985) (a 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).  Because it was not unreasonable, we affirm the judge=s conclusion denying work causation of the employee=s ongoing disability.  See  Hengemuhle, 358 N.W.2d at 59, 37 W.C.D. at 239.

 

2.  Weekly Wage

 

Minn. Stat. ' 176.011, subd. 18, which defines AWeekly wage,@ provides in part as follows:

 

AWeekly wage@ is arrived at by multiplying the daily wage by the number of days and fractional days normally worked [in a week].  If the employee normally works less than five days per week or works an irregular number of days per week, the number of days normally worked shall be computed by dividing the total number of days in which the employee actually performed any of the duties of employment in the last 26 weeks by the number of weeks in which the employee actually performed such duties.

 

Minn. Stat. ' 176.011, subd. 18.  Subdivision 3 of that same section, which defines ADaily wage,@ provides in part as follows:

 

If the amount of the daily wage received or to be received by the employee in the employment engaged in at the time of injury was irregular or difficult to determine, or if the employment was part time, the daily wage shall be computed by dividing the total amount the employee actually earned in such employment in the last 26 weeks, by the total number of days in which the employee actually performed any of the duties of such employment, provided further, that in the case of the construction industry, mining industry, or other industry where the hours of work are affected by seasonal conditions, the weekly wage shall not be less than five times the daily wage.

 

Minn. Stat. ' 176.011, subd. 3 (emphasis added).

 

At Finding 8 and Conclusion of Law 2, the compensation judge determined that the employee=s average weekly wage on June 24, 1994, was $611.65, based on the employee=s average earnings over the course of the twenty-six weeks preceding June 24, 1994.  The judge noted that the employee=s hourly wage varied from week to week depending on whether the job was residential or commercial--$16.00 per hour for residential work and $22.56 per hour for commercial work.  Respondent=s Exhibit 1D(A) provides the employee=s weekly earnings for the twenty-six weeks preceding the injury but no basis for determining the number of days the employee performed any of the duties of his employment during any given week.  The employee concedes that the judge did not have the necessary evidence to calculate the employee=s daily wage according to the statute, but he suggests that, as a construction worker, he nevertheless remains statutorily entitled to have his weekly wage calculated at Anot . . . less than five times the daily wage@ by other available means.  He argues that it is still possible in this case for his daily wage to be determined by reference to the First Report of Injury and his contract, which set forth his hourly rate of pay as $22.56 and his normal work week as forty hours, hence permitting calculation of a Anormal@ daily wage. We are not persuaded.

 

The primary object of wage calculation is to "arrive at a fair approximation of [the employee's] probable future earning power which has been impaired or destroyed because of injury."  Knotz v. Viking Carpet, 361 N.W.2d 872, 874, 37 W.C.D. 452, 455 (Minn. 1985), quoting Sawczuk v. special School Dist. No. 1, 312 N.W.2d 435, 437-38, 34 W.C.D. 282, 287 (Minn. 1981).  In unusual factual situations, a compensation judge has certain discretion in application of the statute to achieve the statute=s objectives. See Loberg v. Northome Healthcare Ctr., 57 W.C.D. 113 (W.C.C.A. 1997).  Where the evidence necessary to comply with the statutory wage calculation directives is not available, the compensation judge may even use another method to calculate the employee's wage, as long as that method reasonably reflects the employee's injury-related loss of earning power.  Decker v. Red Wing Shoe Co., 41 W.C.D. 763 (W.C.C.A. 1988).  Given the evidence presented in this case, including the employee=s fluctuating hourly and weekly wage, the compensation judge could reasonably conclude that there was no reliable way to ascertain the employee=s daily wage and therefore no reasonable way to provide the employee with the benefit of the provision applicable to construction workers.  Because the method chosen by the judge in this case was not unreasonable, we affirm her calculation of the employee=s weekly wage on June 24, 1994.  See Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 37 W.C.D. 235 (Minn. 1984).