The employer and Western National Mutual Insurance Company appeal from the compensation judge’s determination that Western National is liable for the employee’s April 10, 2007, minute trauma to his low back, with no apportionment of liability between that injury and his earlier low back injuries.

This case is before the court to review findings and order issued on remand, and concerns multiple injuries to his neck and low back that Randall Manthei, the employee, sustained while in the employ of Layne Minnesota Company between 1996 and 2007.

The employee began working for Layne Construction, the employer, in October 1975, at age 19, and has been employed there since 1975 except for approximately two years between 1979 and 1981, when he farmed with his brother.  Between 1975 and until some point before December 2005, the employer was insured for workers’ compensation liability in the state of Minnesota by CNA Commercial Insurance (CNA).  As of at least December 18, 2005, the employer was insured for workers’ compensation liability by Western National Mutual Insurance Company (Western National).

The employee has continuously worked for the employer since 1981, and has worked as a crane operator, a groundsman, and a foreman crane operator, working at job sites in a five-state area, and performing jobs that involved significant physical activity.  At some point between March 2000 and August 2002, the employee began working as a foreman or working supervisor.  That position included more supervisory and management work and less crane operation than he had performed in the past, although the employee spent at least 10 to 20 percent of his time performing physically demanding job duties, and, to the extent he was physically able to do so, he also performed the job duties of co-workers when they missed work due to illness.

In addition to his work for the employer, the employee has also performed farming work on his family farm where he and his family reside.  In the past, he typically worked approximately 20 hours per weekend on his farm.  According to the employee’s testimony, by August 2002 he eased up on both his farming activities and the heavy work for his employer due to his ongoing symptoms.

Between 1988 and 2005, the employee sustained multiple injuries to his low back and neck.  The disputes on appeal arise from admitted and alleged injuries the employee sustained between 1996 and 2007 while working for the employer, including specific injuries sustained between 1996 and 2005, a minute trauma injury to his neck and low back that the employee claimed culminated on January 24, 2003, a minute trauma injury to his neck that culminated in disablement on May 4, 2004, and a minute trauma injury to his low back that culminated in disablement on April 10, 2007.^[1]  CNA insured the employer at the time of the employee’s injuries before December 2005; Western National insured the employer at the time of the employee’s December 18, 2005, and April 10, 2007, injuries.  The employer and its insurers have admitted liability for the injuries, but initially contended that they all were temporary in nature.

The employee has received periodic chiropractic and medical treatment for his neck and low back since his first work injury in 1988 and following his later work injuries.  He was ultimately diagnosed with degenerative facet disease at the L4-5 and L5-S1 levels and foraminal stenosis on the left side at the L5 level causing left L5 radiculitis, and an MRI scan showed disc herniations at two vertebral levels.  By December 2001, Dr. Robert Wengler diagnosed degenerative disc disease and small contained disc herniations at the C4-5 and C5-6 levels of the cervical spine, and grade 1 spondylolisthesis at the L5-S1 level with a central left-sided disc herniation.  Dr. Wengler determined that the employee had sustained 10% permanent partial disability to the whole body as a result of his neck injuries and 12% permanent partial disability as a result of his low back injuries, and concluded that the employee’s cervical and lumbar disc conditions resulted from “multiple episodes of subacute trauma sustained during the course of his activities as a heavy equipment operator.”

Litigation on this matter commenced June 6, 2002, when the employee filed a claim petition, listing six injury dates between 1995 and 1999, and claiming entitlement to permanent partial disability benefits relative to his neck and low back, in addition to payment of medical and chiropractic expenses.  The employee continued operating a crane until he sustained an additional injury on November 5, 2002, when he fell off the track of a crane, landed on his low back, and either hit or jarred his neck.  He ceased operating the crane after that injury, but continued to work for the employer, on a lighter-duty basis.  According to the employee’s testimony at a hearing held in December 2003, his symptoms in his neck and low back were permanently worsened by this injury, and he had experienced headaches and pain in his left arm and in his legs.  He also testified that he continued to work because of his financial obligations and because he enjoyed his work, but that he eventually would need to quit or perform other work due to his medical condition and persistent symptoms.

Dr. Wengler opined that the employee sustained an ongoing Gillette injury due to his work as a heavy equipment operator, and that while he continued to work, he was “continually subjected to Gillette phenomenon.”  He concluded that the employee was a candidate for anterior discectomy and interbody fusion at two levels of the cervical spine.  In April 2003, the employee obtained a second opinion from Dr. Jeffrey Dick, who recommended that the employee quit smoking and undertake a six-month walking exercise program, and that if his symptoms did not significantly improve after six months, the employee then would be a candidate for surgical treatment.  The employee followed that advice, but his neck and low back symptoms persisted.

The employee’s claim initially was addressed at a hearing on December 30, 2003.  In dispute were claims related to injuries that occurred between 1995 and November 2002, as well as a claimed Gillette injury of September 24, 2003.^[2]  As part of his claims, the employee sought approval for cervical fusion surgery, based upon the medical opinions of Drs. Wengler and Dick.  The employer and insurer denied the employee’s claims, relying on the opinion of Dr. Stephen Barron, who had examined the employee in September 2002, July 2003 and December 2003, at the request of the employer and CNA.  Dr. Barron concluded that the employee’s work injuries had all been temporary in nature, and that the employee was not a candidate for cervical spine surgery, based on the results of his discogram and lack of objective findings on examination.

On March 15, 2004, the compensation judge issued her findings and order, in which she denied the employee’s claims in their entirety, except for a portion of his claimed chiropractic expenses.  She found that the employee’s work injuries of April 5, 1996, January 13, 1999, and November 5, 2002, were temporary in nature.  The compensation judge also found that the employee had not sustained a minute trauma injury to his neck or low back on September 24, 2003.  The employee appealed from the original findings and order.  On May 4, 2004, while his appeal was pending, the employee underwent a two-level anterior cervical fusion at C4-5 and C5-6, performed by Dr. Wengler.

Following the employee’s appeal, this court issued a decision in which it vacated the original findings and order and remanded the matter to the compensation judge for reconsideration, including whether the employee sustained a Gillette injury as a result of his work activities, in view of all the medical evidence of record, including post-hearing medical reports submitted by the parties.  Manthei v. Layne Minn. Co., slip op. (W.C.C.A. Jan. 20, 2005).

On December 18, 2005, while the case was being considered on remand, the employee sustained an additional injury to his low back.  As he worked as a foreman, he fell about ten feet off a crane, landing on his right foot and then hitting the ground with his right side and low back.  Since that time, he has experienced back pain and right-sided radicular pain.  On January 11, 2007, the employee underwent a two-level discography, and underwent fusion surgery at the L5-S1 level on April 10, 2007.

During the litigation on remand, it became apparent that Western National, the insurer at the time of the employee’s December 2005 injury, should be joined to the case.  The employee filed an amended claim petition on August 28, 2006, to join Western National as a party and to claim that he sustained a permanent low back injury on December 18, 2005.  The employee later pled, in the alternative, that he also had sustained a number of specific injuries to his low back and, in addition, a Gillette injury culminating in disablement on either January 24, 2003, or April 10, 2007, which was the date of his low back fusion surgery.  With respect to his neck, the employee claimed that one or more specific injuries were permanent and that he also had sustained a Gillette injury to his neck culminating in disablement on either January 24, 2003, or on May 4, 2004, which was the date of his cervical fusion surgery.

On August 2, 2007, a second hearing was held before the compensation judge.  Issues included not only those remanded by this court, but also issues arising out of the employee’s work after 2003, including the employee’s claimed minute trauma injuries to his neck and low back that led to his 2004 and 2007 surgeries.  Updated medical records and reports placed in evidence at hearing included Dr. Barron’s December 2006 report from his re-examination of the employee in which he concluded that all of the employee’s specific injuries were temporary in nature and that the employee had not sustained Gillette injuries to his cervical or lumbar spine.  The evidence also included a December 2006 report, issued by Dr. John Dowdle following an independent examination requested by the employer and CNA, in which he concluded that the proposed lumbar spine surgery was reasonable and necessary.

Following the 2007 hearing, the compensation judge found that the employee sustained a minute trauma injury to his neck, as a result of his work, which culminated on May 4, 2004, and a minute trauma injury to his lower back, as a result of his work, which culminated on April 10, 2007.^[3]  The compensation judge concluded that CNA was 100% responsible for benefits, including medical expenses, arising out of the injury to the employee’s neck on May 4, 2004, and that Western National was 100% responsible for benefits arising out of the employee’s injury to his low back on April 10, 2007.  The compensation judge ordered that the employer and its two insurers pay temporary total disability benefits to the employee for a period of time following each of the employee’s 2004 and 2007 surgeries, as well as permanent partial disability benefits and payment for medical expenses related to treatment and surgery to the employee’s neck and low back.

The compensation judge also determined that various specific injuries that the employee had sustained in the course of his employment with the employer were only temporary in nature and did not permanently contribute to his current neck and back condition.  She specifically found that the employee did not sustain a permanent injury to his low back on December 19, 1997, nor December 27, 1999. The compensation judge also concluded that she was precluded by the doctrine of res judicata from addressing the issue of whether one or more of the employee’s injuries predating the December 2003 hearing were temporary or permanent.

The employer and Western National, the insurer at the time of the employee’s December 2005 and April 2007 injuries, appealed from the compensation judge’s findings that the employee’s injuries before the December 2003 hearing were temporary in nature; that the employee sustained a minute trauma injury to his lumbar spine that culminated on April 10, 2007; and that the employee was entitled to payment for post-surgery temporary total disability benefits, permanency benefits and  medical expenses related to treatment for his low back, to be paid entirely by the employer and Western National.

The employer and Western National also appealed from the compensation judge’s determination that the doctrine of res judicata precluded her from assigning any liability to injuries occurring before the December 2003 hearing, and contended that the evidence showed that all of the employee’s earlier injuries to the employee’s low back were permanent and played a substantial contributing role in the employee’s need for surgery in 2007, and that equitable apportionment should have been assigned among the employee’s earlier low back injuries and the adjudicated April 10, 2007, injury.  No appeal was taken by the employer and CNA concerning the findings attributing liability to CNA for the employee’s neck injury that culminated on May 4, 2004.

On appeal, this court concluded that, at the time of the December 2007 hearing, the compensation judge was not precluded by the doctrine of res judicata from determining whether the employee’s injuries predating the December 2003 hearing were temporary or permanent.  The court vacated the portions of the findings and orders concerning the employer and Western National’s liability for benefits due as a result of the employee’s April 10, 2007, low back injury, and remanded the matter to the compensation judge for further consideration.  Manthei v. Layne Minnesota Co., No. WC07-267 (W.C.C.A. June 30, 2008).

On remand, the compensation judge considered the issue of whether any apportionment of liability for the employee’s low back condition should be made as between the employee’s earlier low back injuries and his April 10, 2007, injury.  In her findings and order issued on January 30, 2009, the compensation judge concluded that the employee’s low back injuries through December 18, 2005, were temporary in nature, relying on the medical expert opinion of Dr. Barron.  She therefore concluded that no apportionment of liability was applicable between the employee’s April 10, 2007, injury to his low back and any of his earlier low back injuries.

As a result, the compensation judge determined that the employer and Western National Insurance Company were 100% responsible for benefits arising out of the minute trauma injury to the employee’s low back on April 10, 2007, and ordered payments consistent with her 2007 findings and orders.  The compensation judge acknowledged that the employee had experienced low back and leg symptoms over the years, beginning in 1988, but that he had continued to work for the employer through December 2003 without permanent restrictions on his activities.  The compensation judge explained that it was not until April 2007 that the employee’s injury-related condition disabled him from work, necessitated work restrictions, and resulted in more extensive medical treatment than he had received in the past.  The employer and Western National appeal.

The employer and Western National Insurance Company appeal from the compensation judge’s finding that they are entirely responsible for benefits arising out of the employee’s low back injury on April 10, 2007, and from her related findings that the employee’s earlier low back injuries were temporary in nature and, therefore, no apportionment of liability to those injuries is appropriate.  The employer and Western National argue that the employee’s injuries to his low back between 1996 and 2005 all played a role in the employee’s need for lumbar fusion surgery in April of 2007.  They rely, in part, on the employee’s testimony that he had ongoing permanent symptoms in his low back and left leg, as well as his right leg, following each of his earlier injuries.  They also rely on the findings noted on radiographic studies conducted prior to December 2003 and on the medical opinions of Drs. Dowdle and Wengler, who concluded that the employee’s fusion surgery was required to treat his spondylolisthesis and foraminal stenosis, conditions which were noted on the employee’s pre-December 2003 radiographic studies.  In summary, they argue that the employee’s testimony and his medical records substantiate their argument that the employee’s earlier work injuries were permanent and substantially contributed to the employee’s need for surgery in 2007.

The compensation judge addressed these arguments in her findings and order.  She relied on the opinion of Dr. Stephen Barron that the employee’s injuries and related symptoms through his December 2005 injury were temporary in nature and eventually resolved.  She concluded that it was the employee’s April 10, 2007, injury and not his earlier injuries, which had contributed to the employee’s need for surgery in 2007.

A Gillette injury is a gradual breakdown of a body part or an aggravation of a pre-existing condition as the result of repetitive, minute trauma in the performance of an employee’s ordinary work activities.  Gillette v. Harold, Inc., 257 Minn. 313, 101 N.W.2d 200, 21 W.C.D. 105 (1960).  To establish a Gillette injury, the employee must “prove a causal connection between [his] ordinary work and [the] ensuing disability.”  Steffen v. Target Stores, 517 N.W.2d 579, 581, 50 W.C.D. 464, 467 (Minn. 1994).  Questions of causation fall within the province of the compensation judge.  Felton v. Anton Chevrolet, 513 N.W.2d 457, 50 W.C.D. 181 (Minn. 1994).  The determination of a Gillette injury “primarily depends on medical evidence.”  Steffen, id. (citing Marose v. Maislin Transp., 413 N.W.2d 507, 40 W.C.D. 175 (Minn. 1987)).

Earlier cases involving Gillette injuries required an employee’s cumulative trauma to be sufficiently serious to disable him from work in order for the injury to be compensable.  See Carlson v. Flour City Brush Co., 305 N.W.2d 347, 350, 33 W.C.D. 594, 598 (Minn. 1981).  Minnesota courts since have recognized several other “ascertainable events” that can establish the date of “ultimate breakdown,” which is the time when repetitive micro-trauma becomes a compensable injury.  The date of injury should “be determined on all the evidence bearing on the issue,” including other “ascertainable events” evidencing disability.  Schnurrer v. Hoerner-Waldorf, 345 N.W.2d 230, 233, 36 W.C.D. 504, 509 (Minn. 1984).  For example, ascertainable events may include the initiation of medical treatment, the imposition of work restrictions and modification of work duties, or the last date of employment.  See Lowrey v. Gagnon, Inc., No. WC08-249 (W.C.C.A. July 2, 2009); see also Dillon v. Pennco Constr., No. WC08-127 (W.C.C.A. Sept. 5, 2008).

The record contains conflicting medical opinions on the issue of causation.  The compensation judge reviewed the various medical records and opinions, and specifically accepted Dr. Barron’s opinion, and, in part, the opinions of Drs. Wengler and Dowdle, that the employee’s work injuries through his December 2005 injury were not substantial contributing factors to his low back condition, that they were all temporary in nature, and that they had resolved without permanent partial disability or the need for permanent work restrictions.  The compensation judge concluded that the employee sustained a minute trauma injury to his low back culminating in disablement on April 10, 2007, when he had low back surgery.  It is the compensation judge's responsibility, as trier of fact, to resolve conflicts in expert testimony.  Nord v. City of Cook, 360 N.W.2d 337, 342, 37 W.C.D. 364, 372 (Minn. 1985).  As we have held in other cases as well, this court will generally affirm a compensation judge’s decision which is based on a choice between competing medical opinions.  Perry v. ADB Constr., Inc., 68 W.C.D. 491 (W.C.C.A. 2008).

The employer and Western National also argue that by assigning all responsibility for the employee’s low back condition to his April 10, 2007, injury, the compensation judge erroneously relied on the case of Carlson v. Flour City Brush Co., 305 N.W.2d 347, 33 W.C.D. 594 (Minn. 1981).  They argue that the analysis in Carlson is not applicable to the facts of this case, since the matter before the court now involved a series of admitted specific injuries to the employee’s low back, followed by medical treatment, ongoing symptoms, and a diagnosis of spondylolisthesis and radiculopathy.  They argue that this case “met the requirements for equitable apportionment between all the injuries.”  We disagree.

The compensation judge found that the facts in this case are quite similar to those in the Carlson case, wherein the employee performed the same physically demanding job for a number of years, developing symptoms from time to time serious enough to require medical treatment before finally being advised by her physicians to change occupations.  In this case, the compensation judge acknowledged that the employee sustained numerous work related injuries during his years of work for the employer, but stated that

This court has stated that equitable apportionment is not merely a medical determination and that apportionment of liability cannot be based on “predetermined and precise formulas, but must be determined based on the facts of each case.”  See Harvala v. Noeske Lumber, 44 W.C.D. 118, 125 (W.C.C.A. 1990).  See also Goetz v. Bulk Commodity Carriers, 303 Minn. 197, 200, 226 N.W.2d 888, 891, 27 W.C.D. 797, 800 (1975).  Here, the compensation judge accepted Dr. Barron’s opinions regarding the temporary nature of the employee’s earlier multiple injuries and, in reliance on his opinion, concluded that no apportionment of liability to the employee’s earlier injuries would be appropriate.  The compensation judge also relied on the opinion of Dr. Wengler that the employee’s work over the years represented a substantial contributing factor in the development of his cervical spine degeneration and in the permanent aggravation and acceleration of his juvenile discogenic disease in his lumbar spine.  In summary, there is ample medical support in the record for the compensation judge’s determinations concerning the temporary nature of the employee’s earlier work injuries to his low back and the nature of his 2007 Gillette injury.

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.  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).

Based on our review of the evidence as a whole, we conclude that the record supports the compensation judge's findings.  We are mindful that there is evidence in the record that supports the arguments presented by the employer and Western National.  The record also contains evidence to the contrary.  The issue under this court's standard of review is not whether the facts will support findings different from those made by the compensation judge, but, rather, whether substantial evidence supports the findings of the judge.  Land v. Washington County Sheriff's Dep't, slip op. (W.C.C.A. Dec. 23, 2003) (citations omitted).  Because the compensation judge’s decision is supported by substantial evidence in the record, we conclude that substantial evidence supports her findings that on April 10, 2007, the employee sustained a Gillette or minute trauma injury to his low back, and that there is a causal connection between that injury and the employee's current condition and his need for surgery on April 10, 2007.  We also conclude that the compensation judge’s determination that no apportionment would be appropriate as between the employee’s 2007 injury and his earlier injuries, and therefore affirm her determination that the employer and Western National are entirely liable for the benefits owed to the employee as a result of his April 10, 2007, injury.