On October 12, 1992, the employee saw Dr. Kuiper at the Luverne Medical Center complaining of low back pain since lifting a resident at the nursing home three weeks before.  The doctor diagnosed a lumbar strain and prescribed Flexeril.  The employee returned to the Luverne Medical Center on October 23, 1992, and saw Dr. Larry Lyon.  An x-ray showed significant disc space narrowing at L5-S1 and the doctor diagnosed an acute back strain and advanced degenerative disc disease at L5-S1.  Dr. Lyon recommended the employee stop working, avoid heavy lifting and further recommended the employee give serious consideration to changing jobs on a long-term basis.  By November 6, 1992, Dr. Lyon noted the employee=s acute back strain was resolving.  The doctor recommended the employee continue to wear her back brace and avoid heavy lifting.  The doctor again opined the employee needed to avoid lifting patients.  By December 4, 1992, the employee stated her back pain no longer bothered her, but she continued to wear her back brace at work and received assistance lifting patients.  The doctor concluded the employee=s acute back strain was resolved.  His diagnosis remained advanced degenerative joint disease at L5-S1 and he recommended the employee continue to wear a back brace when she worked.  By a report dated April 20, 1993, Dr. Lyon concluded the employee had reached maximum medical improvement and rated no permanent partial disability as a result of the 1992 personal injury.

The employee was seen by Dr. Walter Carlson at the Midwest Orthopedic Center on January 30, 1997, complaining of low back pain which had worsened over the prior six months.  The doctor ordered an MRI scan which showed bulging discs and degenerative changes at L4-5, and L5-S1.  On February 18, 1997, Dr. Carlson advised the employee she would not require surgery for her low back condition.

On June 5, 1997, the employee sustained a second personal injury while lifting a patient in the course of her employment with the employer.  The employer was then insured by Farm Bureau Mutual Insurance Company.  The employer and insurer admitted liability for the employee=s personal injury.

On June 16, 1997, the employee returned to see Dr. Carlson.  A second MRI scan was read as unchanged from the February 1997 examination.  By July 1997, the doctor noted the employee was becoming incapacitated by pain.  Dr. Carlson ordered a CT scan which he stated showed the employee=s L4-5 disc was satisfactory and L5-S1 disc was the source of the employee=s pain.  In September 1997, Dr. Carlson performed an anterior fusion at L5-S1 with BAK instrumentation.  By report dated January 14, 1998, Dr. Carlson stated the June 1997 personal injury was a permanent aggravation of a pre-existing condition.

Dr. Robert B. Hartman, an orthopedic surgeon, examined the employee on February 2, 1998, at the request of Farm Bureau.  The doctor obtained a history from the employee, reviewed her medical records and performed a physical examination.  Initially, the doctor noted a February 1990, MRI scan documented degenerative changes at L5-S1 and early degenerative disc changes at L4-5.  The doctor stated the medical records evidenced that the employee sustained a work injury in September 1992, which resulted in restrictions on the employee=s work activities.  Dr. Hartman diagnosed chronic low back pain secondary to multi-level degenerative disc disease of the lumbar spine status post-fusion surgery with instrumentation.  The doctor opined that in June 1997, the employee sustained a temporary aggravation of her pre-existing degenerative disc disease from which she returned to her pre-injury status no more than 12 weeks following the injury.  Dr. Hartman opined the employee=s need for the fusion surgery was related to her underlying degenerative disc disease which predated the June 5, 1997 injury.  Finally, Dr. Hartman opined the employee reached maximum medical improvement from the June 5, 1997, injury by September 5, 1997, and rated no permanent partial disability as a result of that injury.

The employer and Farm Bureau filed a petition for contribution and reimbursement seeking payment from the self-insured employer of all or a portion of the benefits the petitioners paid following the employee=s 1997 injury.  The self-insured employer denied liability.

In April 2002, Dr. Hartman reviewed additional medical records and reviewed the employee=s deposition obtained on August 13, 1998.  The doctor again noted the medical information clearly documented the employee had degenerative disc disease at L4-5 and L5-S1 dating back to 1990.  The doctor stated:

The injury of September 25, 1992, necessitated the imposition of restrictions on lifting, pushing, pulling, and carrying.  That is, the injury in September of 1992, necessitated a significant change in treatment, and restrictions.  Therefore, the September 1992 injury must be considered significant or substantial.  In apportioning the need for medical and surgical treatment, 30% of the responsibility must be attributed to the injury of September 25, 1992.  Finally, the alleged injury of June 5, 1997, represents a minor injury.  This injury resulted in a temporary aggravation of Ms. Cook=s pre-existing problem.  In apportioning responsibility for medical and surgical treatment, 10% must be apportioned to this event.  The small apportionment reflects the minimal nature of the injury.  The June 5, 1997, injury is 100% responsible for the temporary disability for the 12 weeks following June 5, 1997.  However, after September 5, 1997, the responsibility for ongoing symptoms must be apportioned as discussed previously: 60% due to the pre-existing condition, 30% due to the September 25, 1992 injury, and 10% due to the June 5, 1997 injury.

(Pet. Ex. A2b).

Dr. Thomas Litman, an orthopedic surgeon, examined the employee on January 23, 2003, at the request of the self-insured employer.  Dr. Litman obtained a history from the employee, reviewed her medical records and performed a physical examination.  The doctor opined the September 25, 1992, injury was a temporary aggravation of the employee=s underlying degenerative arthritis in her lumbar spine which completely resolved.  The doctor opined the June 5, 1997, injury was a permanent and substantial aggravation of the underlying degenerative process which led directly to the employee=s surgery.  Dr. Litman rated a 15 percent permanent partial disability which he apportioned solely to the June 5, 1997, personal injury.

In a Findings and Order served and filed January 7, 2004, the compensation judge found the September 25, 1992, personal injury was a permanent aggravation of the employee=s pre-existing degenerative disc disease at the L4-5 and L5-S1 levels.  The compensation judge found the June 5, 1997, injury was also a permanent aggravation of that condition and that both injuries were substantial contributing causes of the employee=s disability and need for treatment from and after June 5, 1997.  The judge apportioned 75 percent of the employee=s disability to the 1992 injury, and 25 percent to the 1997 injury.  The self-insured employer appeals from these findings.

DECISION

The self-insured employer contends the employee=s testimony does not support the compensation judge=s decision that the 1992 injury was a permanent aggravation of her pre-existing condition.  Specifically, the appellant points to the following testimony from the employee=s deposition in which the employee was asked about the effects of the 1992 injury:^[1]

Q:  And after that week of rest, do you remember how your back was?

A:  It felt better.

Q:  Was it like cured or just improved? Do you remember?

A:  No, I think it was okay.  I went right back to work and did everything else - everything I did before.

Q:  Did it seem like after that that you would injure your back more easily - -

A:  No.

Q:  From that point forward?

A:  No.

Q:  Did it seem like after that you would have pain in your back more often with lifting?

A:  No, because it wasn=t in that spot.

Q:  Okay.

A:  It was more in the middle of my back.

(Pet. Ex. B, p. 37).

The medical records of Dr. Lyon document that the employee=s condition resolved by December 1992, and she sought no medical treatment for her low back thereafter until she sustained a personal injury in June 1997.  In December 1992, Dr. Lyon opined that the September 25, 1992, injury had resolved without permanent partial disability and the employee could resume her former employment.  The appellant contends Dr. Hartman=s opinions concerning the nature and extent of the 1992 injury are inconsistent, unclear, and unsupported by the evidence.  Accordingly, the appellant contends the compensation judge=s decision is unsupported by substantial evidence and must be reversed.  We are not convinced.

The employee also testified that in 1992 Dr. Lyon assigned restrictions which the employer honored by giving her a job which did not require her to lift or transfer patients.  Dr. Lyon further recommended a change in the employee=s job to avoid lifting patients.  The employee testified her supervisor gave her a restorative aide job, which was somewhat lighter, and required less lifting.  The employee testified after 1992, she continued to be careful with her back because she knew that if she overdid it, her back would flare up.

The compensation judge accepted the opinion of Dr. Hartman that the 1992 injury was a substantial aggravation of the employee=s pre-existing degenerative disc disease.  The petitioner does not argue nor can we conclude Dr. Hartman=s opinions lack foundation.  It is the function of the compensation judge to choose between conflicting expert medical opinion.  Nord v. City of Cook, 360 N.W.2d 337, 342, 37 W.C.D. 364, 372 (Minn. 1985).  The testimony of the employee, coupled with the medical opinions of Dr. Hartman, provide substantial evidentiary support for the findings of the compensation judge, and they are affirmed.