The employee appeals from the compensation judge’s determination that he failed to establish a work injury as claimed and from the denial of his claim for benefits.  We affirm.

Terrance Sloan claimed he suffered an injury to his low back on January 26, 2007, while he was working as a driver/guard for Loomis Fargo & Co., an armored car company.  At the hearing before Compensation Judge Cheryl LeClair-Sommer on May 2, 2008, the employee was seeking payment for a fusion surgery done in December 2007, which he alleged was related to the January 2007 claimed work injury.

Mr. Sloan had an earlier work injury to his low back in 1994 when he was employed as a machinist at Nobles Manufacturing.  As a result of the 1994 work injury, the employee had a hemi-laminectomy in April 1994 and a low back fusion with BAK instrumentation in January 1995.  Nobles Manufacturing accepted liability for the work injury and paid for the surgeries as well as other benefits.  In 1997, Mr. Sloan and Nobles Manufacturing entered into an agreement in which Mr. Sloan was paid a lump sum in return for a full, final, and complete settlement of all claims except for future medical.

After his 1995 fusion surgery, Mr. Sloan became part of a study on the effectiveness of the BAK instrumentation.  The surgery was done by Dr. Stephen Kuslich and the study was done through his office at St. Croix Orthopaedics.  By August 1995, Dr. Kuslich believed Mr. Sloan had made a satisfactory recovery, but was still reporting some discomfort in his back and some tingling in his left leg.  Dr. Kuslich released Mr. Sloan to work without restrictions as of October 16, 1995.

Mr. Sloan continued to have low back pain, however, and in January 1996 Dr. Kuslich placed work restrictions and recommended an FCE.  Dr. Kuslich’s notes refer to an R33 he prepared based on the FCE, but that form is not in evidence.  In September 1997, Dr. Kuslich noted that the low back pain was mostly resolved, but that Mr. Sloan still had intermittent sharp pain in his left leg and numbness in his left leg and foot, which Dr. Kuslich thought was “probably unresolvable.”  Work restrictions were still recommended.

Follow up in June 1999 indicated that Mr. Sloan was doing well, having “very little, if any” discomfort in his low back and some tingling in his left thigh as his only symptom.  Mr. Sloan was working full-time at that point and was able to lift up to 70 pounds.  In October 2000, when seen for his 6 year follow up, Mr. Sloan was felt to be doing well.  He reported continued pain  in his left leg which he said he had since the injury and which occurred when he was standing still.

After the 1994 work injury, Mr. Sloan continued to work at Nobles Manufacturing for a time, leaving there in 1997 or 1998.  He then worked for a company renting out storage units and was employed for a couple of years doing janitorial maintenance.  He started working for Loomis on December 11, 2000, and began working as a driver/guard right away.

As a driver/guard, Mr. Sloan and a co-worker operated an armored truck and made pick-ups and deliveries of cash and coins.  Mr. Sloan had an assigned route in downtown Minneapolis, worked Monday through Friday, and testified that the number of stops varied.  The work day began with Mr. Sloan, either by himself or with a co-worker, loading the truck with cash and coins needed for the day.  The cash and coins would be brought on a pallet to the loading area with a forklift and would then be loaded into the truck by hand.  Bags of coins could weigh as much as 60 pounds.  During the day, Mr. Sloan and his partner would work either as a guard or as a driver.  The guard would make the deliveries and pick-ups at the stops and between stops sat in the back of the truck.  The driver drove the truck and was expected to stay in the cab at all times while the truck was on the route.  Mr. Sloan testified at the hearing that he had no physical problems performing either of the jobs before January 26, 2007.

On January 26, 2007, Mr. Sloan was working as a driver.  His partner that day was Tamas Szoboszlai.  Mr. Sloan testified that before starting work that day he had experienced no problems in his low back.  It was Mr. Sloan’s testimony that at about 12:30 p.m., the truck was traveling on Sixth Street and was in the far left lane.  There was an area on Sixth Street where road work had been done recently and there was a depression of a couple of inches in the roadway.  As the truck went over the edge of the depression, it went down and the driver’s seat bottomed out.  The driver’s seat is a suspension seat and uses a pin to adjust the height.  Mr. Sloan testified that when the seat bottomed out, the adjustment pin was broken.  According to Mr. Sloan, Mr. Szoboszlai was thrown out of his seat and a number of cassettes used in ATMs went flying in the back of the truck.

Mr. Sloan testified that within a few minutes of the incident he began experiencing pain in his low back and right leg.  January 26th was a Friday.  On Monday, January 29, Mr. Sloan saw Dr. Susan Richner at Minnesota Occupational Health and provided her the history of the onset of back pain while driving the truck on Friday.  Mr. Sloan was referred for an MRI, which was done on March 8, 2007, and which was read as showing, “severe degenerative changes.”  Ultimately, Mr. Sloan was referred to Dr. Bruce Bartie at St. Croix Orthopaedics and low back surgery was done on December 10, 2007.  The surgery performed was an anterior fusion at the L4-5 and L5-S1 levels accompanied by instrumentation and decompression at L4-5.

Mr. Sloan continued to work for Loomis for some time after the incident and continued to be employed as a driver/guard.  Mr. Sloan was assigned a particular truck, vehicle 3919.  Mr. Sloan stated that when he drove the truck after the incident, he replaced the adjusting pin with a nail that he had found.  He stated that the adjustment pin was replaced within two months by the company.

At the hearing on May 2, 2008, the parties stipulated that the medical treatment received by Mr. Sloan was reasonable and necessary.  The issues for the compensation judge were whether the employee sustained a work injury on January 26, 2007, and if so, whether that injury was a substantial contributing factor in the need for the medical treatment and surgery.

At the hearing, the employer presented the testimony of three other employees.  John Huey worked with Mr. Sloan as a driver/guard for almost two years beginning in July 2003.  After that he was promoted to a supervisory position where he continued to have multiple contacts with Mr. Sloan during the week.  Mr. Huey testified to observing pain behavior, including limping, that was severe enough for Mr. Huey to question Mr. Sloan’s ability to continue doing his job.  On cross-examination, he stated he did not know if Mr. Sloan’s pain was due to his low back or to psoriatic  arthritis, a condition Mr. Sloan had been treated for since 2006.

Tamas Szoboszlai also testified.  He remembered an incident on January 26, 2007, when Mr. Sloan complained about his back pain after the truck hit an indentation in the roadway.  Mr. Szoboszlai remembered it as being in a different location than Mr. Sloan and he indicated that it was a fairly typical occurrence.  He also testified that he was not thrown about in the back of the truck.  Mr. Szoboszlai did not recall any conversation about the adjusting pin being broken or any commentary by Mr. Sloan about leg pain.  He was also of the impression that Mr. Sloan had some back pain before the incident and he had also observed Mr. Sloan limping.

The third employee of Loomis to testify at the hearing was Glenn Wilkoske, who had worked for Loomis for 29 years and was the fleet manager for the company.  As fleet manager, Mr. Wilkoske was responsible for the maintenance and repair of the company’s vehicles.  Mr. Wilkoske stated that every vehicle was inspected once a month and he produced a form showing the numerous items checked by the technician in the inspection.  Mr. Wilkoske testified and showed a maintenance  form for vehicle 3919 indicating that it was inspected on February 21, 2007, and no problems were found.  He subsequently found some chafing on the driver’s seatbelt in vehicle 3919 and replaced it on February 21.  He said that the adjusting pin was not broken at that time because he sat in the driver’s seat and would have been aware of a broken pin.  Mr. Wilkoske produced a work order showing that the adjusting pin was replaced on September 27, 2007.  Mr. Wilkoske testified from his review of the maintenance records that no other driver’s seat repair was done on vehicle 3919.

Mr. Sloan based his medical causation argument on the report of Dr. Bartie dated September 10, 2007.  In his report, Dr. Bartie assumed that there had been an incident on January 26, 2007, in which the driver’s seat Mr. Sloan was using had bottomed out and that he had been symptomatic ever since with no back problems before that date.  Dr. Bartie stated that “the additional trauma reported in January 2007 was likely sufficient enough to create additional soft tissue instability at the fact joints.”  He concluded that this incident represented an aggravation of a pre-existing condition which was responsible for Mr. Sloan’s current treatment.

Dr. John Dowdle conducted an IME of Mr. Sloan on June 18, 2007.  In his initial report dated June 19, 2007, Dr. Dowdle assumed a history of a sudden increase in low back pain after the vehicle he was driving went over a bump and the “seat bottomed out and there was a sudden jarring effect to his low back.”  Dr. Dowdle’s conclusion was that Mr. Sloan’s disc degeneration and stenosis at the L4-5 level was “a transitional disease that is chronic and is in direct relationship to the previous fusion that was done 10 years ago.”  Dr. Dowdle stated the January 26, 2007, incident was a temporary aggravation of this previous condition.

Dr. Dowdle issued a second report on January 28, 2008, after he was provided with additional medical records and Mr. Sloan’s deposition testimony.  In the second report, Dr. Dowdle concluded, based on this information, that the incident of January 26, 2007, represented a permanent aggravation of his previous condition.  Dr. Dowdle prepared a third report after being provided additional information by the employer’s attorney that the co-worker was not thrown about in the January 26, 2007, incident, and that there was no damage to the vehicle.  Based on that information, Dr. Dowdle concluded that none of Mr. Sloan’s treatment or lost time from work was related to the claimed January 26, 2007, work injury.

In her findings and order of August 11, 2008, the compensation judge determined that the employee had “failed to prove by a preponderance of the evidence that he sustained a personal injury that arose out of and in the course of scope of employment with the employer on January 26, 2007.”  In her memorandum the compensation judge discussed the evidence presented at the hearing.  She stated, “while it is entirely possible that the incident on January 26, 2007, resulted in soft tissue injury that aggravated the underlying condition, the employee’s credibility was sufficiently questioned so as to place doubt on the history of symptoms, particularly relevant considering the extensive pre-existing low back condition.”  In summarizing her consideration of the issues the compensation judge said,

On appeal, the employee argues that the findings of the compensation judge are not supported by substantial evidence and must be reversed.  The employee’s primary argument is based  on what he refers to as a “simple before and after analysis.”  Before the injury, according to the employee, he was fully capable of performing his job, which was quite physical.  He had not received treatment for his low back for some years.  After the injury, the employee had constant low back and right leg pain which required his extensive treatment.  According to the employee, this analysis alone should have led to a conclusion by the compensation judge that the work injury was the cause of his present symptoms in the absence of any other explanation.  We disagree.

The employee’s position, both at hearing and on appeal, required the compensation judge to accept the employee’s testimony as to the nature and especially the severity of the incident, which the employee alleges occurred on January 26, 2007.  However, the compensation judge did not accept the employee’s version of that event.  In his testimony at hearing, the employee described an incident  in which the driver’s seat bottomed out with sufficient force to break an adjusting pin and in which his co-worker was thrown around in his seat in the back of the truck.

There was evidence contrary to the employee’s testimony on this issue, however.  While Mr. Szoboszlai stated that the incident was serious enough for a comment to be elicited from him, he denied being jostled in his seat.  More importantly, the employee’s testimony of an incident sufficiently forceful to break the adjusting pin on the seat was essentially refuted by Mr. Wilkoske’s testimony and records that there was no broken pin or repair of an adjusting pin until September 2007.  The employee’s testimony that an adjusting pin was replaced within two months was directly inconsistent with Mr. Wilkoske’s testimony.

The employee also argues that there is no substantial evidence in the form of a medical opinion to support the compensation judge’s decision.  According to this argument, Dr. Dowdle’s last report, that of April 15, 2008, lacked foundation and would not support the compensation judge’s decision.  First, we find Dr. Dowdle’s opinion to have adequate foundation.  He based his opinion on hypothetical facts set out in a letter from the employee’s attorney.  The employee contends that those facts were not established at hearing, but we have previously summarized the evidence and we believe the evidence is consistent with the hypothetical given to Dr. Dowdle.

More importantly, however, the issue in this matter is not one of medical opinion, but is primarily one of credibility.  If the compensation judge had accepted the employee’s version of the January 2007 incident, even Dr. Dowdle would have been of the opinion that the employee’s current condition was the result of a work injury.  As the compensation judge pointed out in her memorandum, the employee had the burden of proof in establishing his claim by a preponderance of the evidence.  The compensation judge, in her memorandum, recounted the factors that led to her conclusion that the employee had failed to meet his burden.

We find the compensation judge’s decision to be supported by substantial evidence.  The decision is affirmed.