The employee appeals from the judge’s decision that the employee’s work-related shoulder injuries were temporary aggravations of a preexisting condition and did not substantially contribute to the employee’s current need for surgery.  We affirm.

The employee first treated for right shoulder complaints in September of 2008, after a lifting injury while working for Culvers, an employer not involved in the current proceedings.  She received chiropractic treatment for a possible rotator cuff tear.

The following month, in October of 2008, the employee fell and again injured her right shoulder.  She underwent surgery in March of 2009, which consisted of debridement of a superior lateral anterior posterior tear and partial thickness rotator cuff tear.  At the time of that surgery, Dr. Paul T. Rud noted extensive degenerative fraying of the labrum.  The employee continued to have problems with her right shoulder thereafter and received some chiropractic treatments and physical therapy through August of 2009.

On October 17, 2009, the employee dislocated her right shoulder when she slipped and fell while working for Brambleberry Farm [the employer], which was insured for workers’ compensation purposes by Auto-Owners Insurance Group [Auto-Owners].  The employee treated that day at Cayuna Medical Clinic, where the shoulder was reset.  A few days later, on October 23, 2009, the employee saw Dr. Benjamin Robertson.  He ordered an MRI, which showed a Hill-Sachs deformity of the posterolateral humeral head and a soft tissue and osseous Bankart lesion.  He prescribed physical therapy.  When seen by Dr. Robertson on November 18, 2009, the employee continued to be quite symptomatic, and the doctor noted that the employee had experienced no improvement with physical therapy.  He decided to proceed with a labral repair.  The employee underwent surgery on January 29, 2010.  In his operative report, Dr. Robertson noted Grade IV arthritic change on the majority of the humeral head with near complete loss of cartilage on the humeral head.  He also found Grade IV arthritic change on the anterior aspect of the glenoid.  Given the advanced arthritic changes, Dr. Robertson elected to forgo the labral repair.

On May 24, 2010, Dr. Robertson restricted the employee to no overhead lifting and on June 29, 2010, stated that the employee was at maximum medical improvement [MMI].  The employee continued to treat with Dr. Robertson for advanced glenohumeral arthritis in the right shoulder, which the doctor opined was caused by the employee’s October 2009 work injury.

On December 14, 2010, Dr. Robertson proposed total right shoulder replacement surgery.  Auto-Owners paid the employee 17 weeks of temporary total disability benefits, 28 weeks of temporary partial disability benefits, and medical expenses but denied liability for the proposed right shoulder replacement.

On December 17, 2010, the employee fell while working for the employer and dislocated her left shoulder.  The employer was then insured by Farm Bureau Mutual Group [Farm Bureau].  The anterior inferior dislocation of the glenohumeral joint of the left shoulder was reduced at St. Joseph’s Medical Center.

The employee followed up with Dr. Robertson, and an MRI of the employee’s left shoulder revealed a Bankart lesion with a loose body.

On April 5, 2011, Dr. Robertson operated on the employee’s left shoulder, arthroscopically removing loose bodies and debriding the glenohumeral joint, the anterior labrum, and the glenoid and articular surface of the humeral head.  Dr. Robertson noted advanced osteoarthritis in the left shoulder, with complete loss of cartilage on the humeral head and on the glenoid.

When the employee continued to experience symptoms, despite physical therapy, Dr. Robertson recommended a total left shoulder replacement.  It was his opinion that the significant degenerative changes in the employee’s left shoulder were caused by the December 17, 2010, left shoulder dislocation.  Farm Bureau paid the employee temporary total disability benefits continuing from December 17, 2010, permanent partial disability benefits for a 3% whole body impairment for the left shoulder dislocation, and medical expenses, but it denied liability for the proposed surgery.

Dr. Jeffrey Nipper performed an independent medical examination at the request of the employer and Auto-Owners.  In his report of January 11, 2012, Dr. Nipper opined that the end-stage degenerative arthritis in both of the employee’s shoulders was not related to the right and left shoulder dislocations but was instead idiopathic and the result of a chronic degenerative process pre-dating these work injuries.  He disputed Dr. Robertson’s contention that the December 2010 work injury caused the Grade IV arthritis, stating that it “could not possibly have been caused by the anterior dislocation and the Bankart lesion.”  He agreed that the employee needed shoulder replacement surgeries but opined that the work injuries were not substantial contributing causes of the employee’s need for those surgeries.

Dr. Nipper subsequently reviewed additional records and on April 9, 2012, issued an addendum to his report.  His diagnosis and impression remained unchanged.  With regard to the left shoulder injury and the degenerative changes found during the April 2011 surgery, he stated, “it is absolutely impossible that degenerative changes of that nature could have been caused by that event within that short period of time.”

Dr. Richard C. Strand conducted an independent medical examination of the employee for the employer and Farm Bureau, issuing a report on June 16, 2011.  It was his opinion that the employee had two diagnoses for her left shoulder: “anterior dislocation . . . relocated and resolved” and “end stage severe degenerative arthritis of the glenohumeral joint pre-existent disease.”  He did not dispute that the employee needed left shoulder replacement but opined that that surgery was not related in any way to the dislocation occurring in December of 2010.

Dr. Strand conducted a second examination and in a report dated August 31, 2011, opined that the employee had reached MMI from the left shoulder dislocation within three months of that injury.  He rated the employee as having a 3% whole body impairment pursuant to Minn. R. 5223.0450, subp. 2.B.(1) for a single-episode shoulder dislocation.  The doctor later reviewed additional medical records and issued an addendum report on March 22, 2012.  He opined that degenerative arthritis of the shoulder does not commonly develop from a dislocation and it “is just not reasonable medically” for such arthritis to develop in a short period.  He also did not believe that a dislocation would accelerate a preexisting degenerative condition.  He further disagreed with Dr. Robertson’s opinion that the dislocation caused the employee’s end-stage arthritis.

On November 30, 2011, the employer and Farm Bureau filed a petition to discontinue benefits based on Dr. Strand’s opinion that the employee’s left shoulder dislocation was not a substantial contributing cause of the employee’s claims for ongoing medical treatment and wage loss benefits.  Auto-Owners was joined in that action.  The employee subsequently filed a medical request, seeking approval of left shoulder replacement surgery.  The matters were consolidated for hearing, which took place in April of 2012.  Issues at hearing included the nature and extent of the admitted work injuries and whether the work injuries continued to contribute to the employee’s overall disability and need for right and left shoulder replacement surgery.  In findings and order filed on June 4, 2012, the compensation judge found, in part, that the work injuries were temporary aggravations of the employee’s preexisting degenerative shoulder conditions and were not substantial contributing causes of the employee’s ongoing disability or need for bilateral shoulder replacement.  He also found that reasonable grounds existed to discontinue wage loss benefits.  The employee appeals from the judge’s finding as to causation.^[1]

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 (2012).  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).

The employee argues that substantial evidence does not support the judge’s decision that the employee’s work injuries do not substantially contribute to her need for bilateral shoulder replacement.  More specifically, the employee disputes the judge’s finding that the employee’s work injuries were temporary aggravations of a preexisting condition, contending that no medical support exists for that conclusion.  However, we note that, in his March 22, 2012, report, Dr. Strand stated that while “a dislocation of the shoulder is not going to accelerate the preexisting degenerative condition; it may temporarily aggravate it.”  And both Dr. Strand and Dr. Nipper opined that the degenerative condition of the employee’s shoulders preexisted the work injuries.  In contrast, Dr. Robertson, in his April 10, 2012, report, stated that “it is debatable whether [the employee] had some degenerative change prior to her [left] shoulder dislocation.”  He also stated that the employee did not have preexisting arthritis in her right shoulder prior to the 2009 work injury, basing his opinion on his review of the intraoperative photos from the March 25, 2009, surgery.  He opined that those photos showed some “mild degenerative fraying at the labrum . . . but no arthritic change.”  We note, however, that the surgeon who performed that surgery reported “extensive” degenerative changes in the labrum, and Dr. Strand opined that labral degeneration was common with severe degenerative arthritis of the shoulder.  Also, Dr. Robertson’s finding of no degenerative condition in March of 2009 is not the equivalent to a finding that no degenerative changes existed at the time of the work injury in October of 2009.  Dr. Nipper’s and Dr. Strand’s opinions provided substantial evidence to support the judge’s finding of a temporary aggravation of the employee’s preexisting arthritis. ^[2]

The employee also contends that the judge discounted “as unfounded” the medical opinion of the treating doctor, Dr. Robertson, pointing to language in the judge’s memorandum that “there is no evidence to support a conclusion that the employee’s work injuries caused the condition requiring the surgery.”  Again, we are not persuaded.  In the findings portion of his opinion, the judge specifically referenced office notes and reports of Dr. Robertson, wherein the doctor indicated that the arthritis found in the employee’s shoulders was caused by the dislocations.  The findings clearly indicate that the judge reviewed and considered the medical records of Dr. Robertson, Dr. Strand, and Dr. Nipper.  The judge’s adoption of the opinions of Dr. Strand and Dr. Nipper constituted a choice between expert witnesses.  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.  Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985).

The employee also contends that there is no medical opinion to support the judge’s assumption that the employee had prior trauma to her left shoulder, referring to the judge’s finding that imaging taken at the time of the December 17, 2010, injury “showed irregularities consistent with previous dislocation of the left shoulder.”  This finding comes directly from the December 20, 2010, x-ray report, which read, “[t]here is some irregularity consistent with previous dislocation.”

The employee also references the judge’s comment in his memorandum that “the left shoulder displayed evidence of long term arthritic changes that indicated a serious condition existing prior to the employee’s left shoulder work injury.”  That comment, however, is likely a reference to the findings of advanced osteoarthritis found at the time of surgery in April 2011.  Both Drs. Nipper and Strand have cited the surgical findings as evidence of a preexisting condition.

While the judge referenced the x-ray finding of a possible prior dislocation of the left shoulder, neither Dr. Strand nor Dr. Nipper relied on such a finding in rendering their causation opinions, and the judge clearly accepted the opinions of those doctors.  Whether the employee had a prior dislocation or not, Drs. Strand and Nipper share the opinion that dislocations did not cause the employee’s end-stage degenerative arthritis.  The judge was entitled to accept that opinion.

The judge’s findings are affirmed in their entirety.