The employer and ACE USA/ESIS appeal from the compensation judge’s finding that the employee sustained an SI joint injury as a result of his work-related injuries on April 19, 2004, and August 8, 2006, and from the award of payment for the recommended SI joint fusion surgery, related medical expenses and related disability benefits.  We affirm, as modified.

The employee, Peter A. Bode, has worked as a diesel technician for the employer, River Valley Truck Center, since June 1995.  In the course of his work for the employer, the employee sustained admitted injuries in 2004 and 2006.

The employee’s medical history pre-dating his work for the employer includes multiple injuries, including an injury he sustained in 1994 when he was struck by an automobile.  As a result of that accident, he developed low back mid dorsal pain, left knee pain, and pain in his right buttock, extending into his right leg and foot.  He sought orthopedic treatment, and underwent physical therapy to treat his symptoms.  The employee eventually sought treatment from a neurosurgeon, attended a pain management clinic through Abbott Northwestern Hospital, and also received chiropractic treatment for his continued low back and right leg pain.  He remained off work following this accident until April 1995, when he was released to return to work without restrictions.  According to the employee, his symptoms resulting from this injury subsided by approximately 1998.

The employee was also involved in a snowmobiling accident in December 2000, following which he sought treatment at an emergency room, reporting pain in his mid low back and in his upper back between his shoulder blades, as well as right shoulder discomfort.  Lumbar spine, thoracic spine and shoulder x-rays at that time were interpreted as being normal.

In July 2001, the employee was injured while driving an all-terrain vehicle.  He sustained various lacerations and abrasions; he injured his right hand and fractured his left great toe, and has undergone periodic medical treatment for those injuries.  He has also sustained various work injuries over the course of his employment with the employer since 1995; the only injuries at issue in this appeal occurred in April 2004 and August 2006.

On April 19, 2004, as the employee stood on a stool while working on a diesel truck engine, the stool gave way, and he fell, striking the front truck tire with the right side of his low back, and landing on the floor.  The employee developed a bulge in his low back on the right side, which later resolved, and he also experienced pelvic pain.  The employee initially consulted Dr. Kara Jorve at the New Ulm Medical Center, reporting acute low back pain and bilateral buttocks pain; x-rays of his lumbar spine were interpreted as normal.  Dr. Jorve diagnosed musculoskeletal low back pain, and prescribed medication, ice and heat, and physical therapy.  The employee continued to work within restrictions for two weeks.

The employer and ACE USA/ESIS, the insurer at the time of the employee’s 2004 injury, admitted primary liability for the employee’s injury, and provided payment for medical expenses and related temporary disability benefits.  The employee sought continued medical treatment, including chiropractic care from Dr. Steve Hawkins, who provided treatment and assigned work restrictions to limit the employee’s work hours.  Dr. Hawkins diagnosed lumbar subluxations, a lumbar strain/sprain, and a subluxation of the sacrum and pelvis.

The record contains extensive medical records documenting the treatment the employee underwent following his injury.  He consistently reported pain following his injury, including pain in his low back, radiating into his groin area and into his legs.  The employee initially consulted physicians at the Mankato Clinic for his continued pain, and was diagnosed with low back pain with radiculopathy to the bilateral legs and groin.  His radiographic studies focused on his low back and hip area, and were essentially normal.  The employee underwent pool therapy, which seemed to aggravate his pain, and he developed pelvic and coccyx pain.  Following consultations with a neurosurgeon and neurologist at the Mankato Clinic, the employee ultimately was diagnosed with right sacroiliitis.  The employee underwent a right SI joint injection in June 2004, underwent additional physical therapy, and also consulted a urologist for evaluation of his groin pain.  At medical examinations in 2004 and early 2005, the employee continued to report chronic pelvic pain.

In March 2005, the employee consulted Dr. James Attarian at the Mankato Clinic, reporting chronic back and pelvic pain, and also seeking a second opinion concerning treatment.  Dr. Attarian concluded that the employee had some component of lumbar radiculopathy and a component of inguinal nerve entrapment, and suggested an inguinal nerve block and selective lumbar nerve root block, and possibly a cortisone injection to relieve nerve entrapment. It is unclear from the record whether he received injections at that point.

In May 2005, the employee sought chiropractic treatment from Dr. Frederic Falentin.  He reported lower back pain on his right side, with radiating symptoms along the front of his thigh, his groin and along his lateral thigh, and that he had dealt with this condition since his April 2004 injury.  The employee received approximately seven treatments between May and late July 2005, and he testified that he obtained only short-lived relief from these treatments.

The employee also testified that his low back pain and pain in his pelvic area never dissipated after his 2004 injury.  He continued to work on a full-time basis as a truck mechanic, however, following his 2004 injury.

The employee sustained a second work related injury on August 8, 2006, when he fell backwards while climbing down from inspecting a truck engine.  As he stepped down, he stepped on a transmission jack.  The jack, which was on wheels, rolled and he lost his footing.  He fell backwards, landing on top of the jack, and landing on his tailbone and lower back.  The employee consulted physicians at the Mankato Clinic, reporting low back pain, tailbone pain and bilateral buttock pain.  He continued to receive medical care in the occupational medicine department of the Mankato Clinic, and was prescribed medications and a course of physical therapy and was assigned work restrictions.  X-rays of the employee’s lumbar spine and pelvic area were normal; and MRI scan of the lumbar spine showed a mild disc protrusion at the L4-5 level.

Due to his continued symptoms, the employee was referred for an orthopedic consultation.  Dr. Paul Matson, at the Orthopaedic and Fracture Clinic, evaluated the employee in October 2006.  He recommended epidural injections, which provided no pain relief.  Dr. Matson also referred the employee for continued physical therapy, to treat his persistent low back, right hip and right leg pain, but the employee reported limited progress from the therapy.  Dr. Matson noted that the employee’s pain had persisted in spite of extensive conservative treatment, including physical therapy and epidural injections, and concluded that the employee’s pain might be related to a right iliopsoas and sacroiliac joint and hip pain.  Dr. Matson also referred the employee for an MRI scan of the pelvis, hips and sacrum area; that MRI scan, conducted in November 2006, was interpreted as being negative.

By late November, Dr. Matson noted that the employee’s symptoms were unresponsive to physical therapy, and so he referred the employee for chiropractic treatment with Dr. Keith Kuch, noting that Dr. Kuch had past success with other SI patients.  The employee underwent treatment for approximately one month, and by mid-January 2007 reported that the chiropractic treatment had not helped significantly with his right sacroiliac joint pain.  Two right sacroiliac joint injections provided very temporary relief to the employee and so, by April 2007, Dr. Matson referred the employee to the Twin Cities Spine Center for further evaluation.

In May 2007, the employee consulted Dr. Francis Denis at the Twin Cities Spine Center, complaining of low back and bilateral leg pain.  Dr. Denis diagnosed chronic low back pain and bilateral leg pain, and recommended conservative treatment before considering surgery.  Dr. Denis also referred the employee to Dr. John Stark, for further evaluation.  Before consulting Dr. Stark, the employee chose to undergo a bone scan, which showed an uptake in both the left and the right sacroiliac joints.  He also consulted Dr. Matson again in December 2007, at which time his examination demonstrated tenderness over both joints and an increase in pain with hip rotation.  Dr. Matson also referred the employee to Dr. Stark for a surgical consultation.

Dr. Stark initially examined the employee on February 8, 2008, at which time the employee reported pain in his right SI area.  Dr. Stark diagnosed the employee as having “[c]linical signs and symptoms of right sacroiliac, mild suggestion of bilateral radicular complaint, [and] possible low-grade lateral recess stenosis.”  Dr. Stark recommended a diagnostic and therapeutic injection and a CT scan, and noted that he would review the employee’s previous MRI scans.  Dr. Stark also concluded that the employee might require surgery in the future.

Shortly thereafter, the employee underwent a sacroiliac joint CT scan which was interpreted as showing mild degenerative changes at the SI joints bilaterally and mild degenerative changes at L4-5 without high grade spinal canal stenosis or nerve root distortion.  The employee also underwent a right sacroiliac joint injection.  He testified that he received immediate relief from his joint injection that lasted about one hour, and that he also had some additional temporary relief for approximately one week.  Dr. John Stark ultimately diagnosed right SI pain, and recommended that the employee undergo an SI joint fusion surgery.

In April 2008, the employee filed a claim petition seeking authorization for the recommended surgery.  The employer and both insurers denied liability for the claimed surgery, denying that the employee required the surgery, and contending that the employee’s alleged disability and need for medical treatment were unrelated to the employee’s work injuries during their respective periods of coverage.  The employer and GAB/Robins, however, petitioned for a temporary order under Minn. Stat. § 176.191, agreeing to pay for certain medical expenses and related Roraff fees pending the judicial determination of the employee’s claim.

In July 2008, the employee again consulted Dr. Stark, reporting no change in his symptoms or complaints, and referring to his pain level as being at 5 on a scale of 1 to 10.  According to the employee, his symptoms by that point included a “boring” pain from his back into the front, pain into his right leg, pain into his right testicle, and a grinding and popping sensation in his hip, which he first noticed after his August 2006 injury.  Dr. Stark again diagnosed a “work-related sacroiliac injury with limiting pain and functional loss,” and concluded that “[b]ased on his functional limit localizing symptoms and the diagnostic criteria I think he meets the indications for fusion.”

During the course of litigation, the employee attended two independent medical examinations.  On July 17, 2008, he was examined by Dr. Nolan Segal at the request of the employer and ESIS, the insurer at the time of the employee’s 2004 injury.  Dr. Segal concluded that the employee’s subjective complaints were not consistent with his objective examination findings or the findings on radiological studies.  He noted that the employee might have some minimal degenerative disease in his SI joints, but he saw no evidence of SI dysfunction.  Dr. Segal also noted some mild arthritic changes in the employee’s lumbar spine, including mild disk bulging, but determined that there was nothing from a radiological perspective to explain the employee’s lower extremity symptoms.  He diagnosed idiopathic degenerative disease, and concluded that the employee’s April 19, 2004, incident was, at most, a strain and temporary aggravation of his preexisting condition and was not a factor in his current condition.  Dr. Segal also concluded that the employee was not a candidate for any type of back surgery, including the proposed SI joint fusion surgery.

By contrast, Dr. Terry Hood, who examined the employee on August 19, 2008, at the request of the employer and GAB Robins, insurer at the time of the employee’s 2006 injury, agreed that a right SI joint fusion would be reasonable.  At the time of Dr. Hood’s examination, the employee reported multiple symptoms, including right-sided pain in his low back, extending into his buttock, right leg and foot, in addition to pain radiating into his right groin, occasional left leg pain, diffuse right leg weakness, and numbness in his right buttock and his right leg.  Dr.  Hood concluded that the employee had persistent pain emanating from his right sacroiliac joint, and that this condition was 50% due to his 1994 motor vehicle accident, 40% to his April 2004 injury, and 10% to his August 2006 injury.  Dr. Hood explained that he apportioned a minimal portion to the employee’s 2006 injury based on the employee’s report that the only new symptom he experienced after his 2006 injury was temporary left-sided pain.

According to his report issued on September 3, 2008, Dr. Stark concluded that both of the employee’s work injuries in 2004 and 2006 substantially contributed to his “disabling pain, dysfunction, and probable need for surgery” due to his diagnosis of right sacroiliac pain or sacralgia.  Dr. Stark explained that

Dr. Stark apportioned liability for the employee’s condition as being 75% due to his 2004 injury and 25% due to his 2006 injury, concluding, as follows:

On November 6, 2008, Dr. Segal issued a supplemental report, following his review of Dr. Hood’s report.  He again concluded that the findings on the employee’s February 18, 2008, CT scan were related to neither the employee’s April 2004 nor his August 2006 work injury, and that the employee’s 2004 injury “was at most a strain and temporary aggravation of a pre-existing condition with no evidence to suggest any structural musculoskeletal injuries.”  Dr. Segal again stated his opinion that the employee was not a candidate for sacroiliac joint fusion surgery, citing various reasons: the employee had not experienced complete relief of his symptoms from the SI joint injections, and “the findings noted on his radiologic studies, including the February 18, 2008 study, did not suggest a problem that would warrant sacroiliac joint fusion surgery.”

The employee’s claim was addressed at a hearing on November 10, 2008.  At the hearing, the employee testified that he has continued to work for the employer, performing the same technician work he performed before his injuries.  He testified that his job duties have resulted in an increase in his symptoms, and that his difficulty performing his duties increased after his 2004 injury and to an even greater extent after his 2006 injury.  He testified that his right leg symptoms are more severe than they were in 2004, and he has experienced bilateral leg pain since his 2006 injury.

The hearing record closed on December 1, 2008, after submission of letter briefs from the parties.  In his Findings and Order served and filed January 30, 2009, as amended on February 5, 2009, the compensation judge found that the employee sustained an SI joint injury, and that the recommended SI joint fusion surgery was reasonable and necessary.  He concluded that the surgery was causally related to the employee’s injuries in 2004 and 2006, and apportioned liability consistent with that outlined by Dr. John Stark, that is, 75% due to the work injury of April 2004 and 25% due to the work injury of August 2006.  The employer and ESIS, the insurer at the time of the employee’s 2004 injury, appeal.

The employer and ESIS appeal the compensation judge’s determination that the employee sustained an SI joint injury due to his work related injury of April 19, 2004, and from the finding that the SI joint fusion surgery recommended by Dr. Stark is reasonable, necessary, and causally related to that injury.  They also appeal from the apportionment of liability assessed by the compensation judge as between the employee’s 2004 and 2006 injuries, arguing that there not legally sufficient evidence to support the compensation judge’s findings and orders.

The compensation judge relied on the opinions of Drs. Stark and Hood when concluding that the employee sustained an SI joint injury as a result of his 2004 and 2006 injuries and that the recommended SI joint fusion surgery was reasonable and necessary.  The judge also noted that both Drs. Stark and Hood apportioned liability for the employee’s condition and need for surgery between both injuries, and specifically chose the apportionment ratio determined by Dr. Stark.  The employer and ESIS argue that the compensation judge’s decision is lacking because he refers primarily to the medical expert opinions and not to the ongoing treatment provided to the employee since 2004.  They further argue that the compensation judge “does nothing more than cite the conclusions reached by Dr. Stark and Dr. Hood, and report that these support a finding that surgery is reasonable and necessary.”  In conjunction with that argument, they contest the foundation for Dr. Stark’s opinion, asserting that he lacks adequate foundation for his opinion.  They argue that there is no indication that Dr. Stark had an accurate history of the 2004 injury, or that he reviewed the medical records and diagnostic studies performed in 2004 and 2006.

To be of evidentiary value, an expert medical opinion must be based on adequate foundation.  Welton v. Fireside Foster Inn, 426 N.W.2d 883, 41 W.C.D. 109 (Minn. 1988).  The competence of a witness to render expert medical testimony depends upon both the degree of the witness’s scientific knowledge and the extent of the witness’s practical experience with the matter at issue.  Reinhardt v. Colton, 337 N.W.2d 88 (Minn. 1983).  Our review of Dr. Stark’s records shows that he examined the employee on three occasions in 2008.^[1]  Over the course of his treatment of the employee, Dr. Stark conducted physical examinations of the employee, took a history from him, provided him with an epidural injection, reviewed the employee’s bone scan and the films from at least one of his MRI scans of his lumbar spine, and referred him for a CT of his SI joint in February 2008, before reaching the conclusion that the employee’s 2004 and 2006 injuries substantially contributed to his SI joint condition and his need for surgery.  As a general rule, this level of knowledge establishes a doctor’s competence to render an expert opinion.  See Grunst v. Immanuel-St. Joseph’s Hosp., 424 N.W.2d 66, 40 W.C.D. 1130 (Minn. 1988).  Dr. Stark had adequate foundation for his medical opinion.

The employer and ESIS also argue that Dr. Stark’s opinion was deficient as he did not explain the mechanism of injury, that is, how the reported injuries in 2004 and 2006 caused injury to the SI joint.  An expert medical opinion does not lack foundation because the doctor fails to explain the mechanism of injury or the underlying reasons for the expert opinion.  Rather, the presence or absence of such testimony goes to the weight that may be afforded the opinion by the compensation judge.  All that is required, under the facts of the case when considered as a whole, is that a competent medical witness opined that the injuries causally contributed to the disabling condition.  See, e.g., Goss v. Ford Motor Co., 55 W.C.D. 316 (W.C.C.A. 1996); Darnick v. Swett & Crawford, slip op. (W.C.C.A. Oct. 29, 2002).  Here, Dr. Stark clearly expressed his opinion that the 2004 and 2006 injuries caused injury to the SI joint resulting in a need for surgical treatment.  His opinion was adequately founded, and the compensation judge could reasonably rely on that opinion.

In addition, the compensation judge relied on the expert medical opinion of Dr. Hood; the employer and ESIS also contest the foundation for Dr. Hood’s opinion, arguing that it appears that he simply deferred to Dr. Stark for his recommendation for surgery, that he is a neurosurgeon and therefore is not fully versed in this type of condition or surgery, and that he did not explain in his report why a right SI joint fusion would be appropriate or why it would be related to the employee’s 2004 injury.  We are not persuaded.

As noted by the employer and GAB Robins, Dr. Hood took a complete history from the employee at the time of his examination and reviewed all of the relevant medical records documenting the employee’s previous medical treatment.  Dr. Hood also performed a physical examination of the employee.  Dr. Hood had adequate foundation to render his opinion, and the compensation judge reasonably relied on that opinion when reaching his conclusions concerning the employee’s claim.^[2]

The employer and ESIS also argue that the compensation judge failed to make a determination concerning the nature and extent of the employee’s 2004 injury.  They contend that the compensation judge instead simply recited the employee’s testimony and did not discuss any of the contemporaneous medical records, diagnostic studies or diagnoses issued by doctors treating the employee in 2004.  They contend that without such a determination and a basis for that determination, the reviewing court cannot conclude that substantial evidence supports this “apparent conclusion” that the employee sustained an SI joint injury as result of his April 19, 2004, injury.  The employer and ESIS therefore request that this “implied determination” by the compensation judge must be reversed, with that issue remanded to the compensation judge for further review.

The compensation judge’s findings, when read as a whole, include his determination that the employee sustained a SI joint injury as a result of his work injuries.  The compensation judge’s findings specifically refer to the employee’s injuries on April 18, 2004, and August 8, 2006, and the symptoms he experienced after each injury.  At Findings No. 8 and 10, and in his memorandum, the compensation judge determined that the employee had sustained an SI joint injury, relying on Dr. Hood’s and Dr. Stark’s opinions when making that determination.  The compensation judge also referred to the employee’s testimony, which he found to be credible, that his chronic pelvic pain symptoms never completely resolved following his work injury in 2004, and that those symptoms were aggravated following his 2006 injury.  We recognize that it is the trier of fact's responsibility to assess the credibility of a witness, and therefore defer to the judge’s determination concerning the employee’s credibility when testifying about his symptoms and the effects of his injuries.  See Tolzmann v. McCombs-Knutson Associates, 447 N.W.2d 196, 198, 42 W.C.D. 421, 424 (Minn. 1989) (citing Even v. Kraft, Inc., 445 N.W.2d 831, 835, 42 W.C.D. 220, 225 (Minn. 1989)).  It is clear from his findings that the compensation judge determined that the employee sustained a SI joint injury as a result of both his 2004 and 2006 injuries.

The employer and ESIS also argue that even if this court determines that the compensation judge did make a factual determination concerning the employee’s 2004 injury, substantial evidence does not support a conclusion that the 2004 incident resulted in an SI joint injury.  They argue that the employee’s testimony concerning his post-2004 symptoms is not supported by his contemporaneous medical records and diagnostic studies following his 2004 incident.  They refer in detail to the seemingly inconsistent information provided to various medical providers by the employee concerning the details and nature of the 2004 incident.  They also refer to the normal or negative results from radiographic studies conducted in 2004 and 2006, and a neurological examination in June 2004.  The employer and ESIS argue that the compensation judge did not refer to any of those medical records, and provided no basis or explanation for his determination, but instead cited solely to the employee’s testimony and the expert medical opinion reports issued by Drs. Stark, Hood, and Segal.  As a result, the employer and ESIS argue that there is no logical basis on which to conclude that the employee sustained an SI joint injury in April 2004.

We again evaluate these arguments by reviewing the record as a whole and the findings as a whole.  While it is true that the compensation judge did not refer specifically to the employee’s records generated by various physicians and chiropractors following his 2004 and 2006 injuries, he does refer, in his findings and memorandum, to the background information cited by Drs. Segal, Stark, and Hood and to the history outlined by the employee. A compensation judge is not required to relate or discuss each piece of evidence introduced at the hearing.  Midtling v. Schwan’s Sales Enters., slip op. (W.C.C.A. Sept. 22, 2003) (citing Braun v. St. John’s Univ., slip op. (W.C.C.A. July 20, 1992)).  The compensation judge’s reliance on the medical expert’s opinions and reports was sufficient.

The employer and ESIS also argue that there is no evidence in the record to support the compensation judge’s conclusion that the SI joint fusion surgery, as recommended by Dr. Stark, represents reasonable and necessary medical treatment or that such surgery is causally related to the employee’s 2004 and 2006 injuries.  They contend that the employee’s need for proposed surgery is unrelated to his 2004 injury, based on the normal results on his radiographic studies conducted after his 2004 injury.  They also argue that the compensation judge failed to analyze factors that courts have referred to in the past when reviewing the appropriateness of fusion surgery, contending that although such factors are not necessarily dispositive for the issue presented in this case, they would certainly be instructive for determining whether surgery would be reasonable and necessary.  The employer and ESIS’s underlying argument is that there is little indication that the compensation judge considered any factors other than the employee’s ongoing complaints.

The employer and its 2006 insurer, GAB Robins, also argue that the surgery proposed by Dr. Stark is not reasonable or necessary, at this time, to cure or relieve the employee from the effects of his injury, primarily because the employee has not exhausted all conservative treatment prior to undergoing this radical surgery.  They contend that the employee should undergo a series of injections to determine whether or not surgery will actually relieve his symptoms.  Relying on Dr. Segal’s report, they contend that to proceed with the surgery at this time is premature, as there is no certainty that the employee’s symptoms will be substantially improved by that surgical procedure.

The record contains conflicting medical opinions concerning the employee’s diagnosis and need for surgery and on the issue of causation.  The compensation judge reviewed the various medical records and opinions, and specifically accepted Drs. Stark’s and Hood’s opinions that the employee’s 2004 and 2006 work injuries substantially contributed to his SI joint condition and need for 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).

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 insurers.  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, including expert medical opinions, we conclude that substantial evidence supports his findings that as a result of his April 19, 2004, and August 8, 2006, injuries, the employee sustained a SI joint injury, and that there is a causal connection between the employee’s SI injury and his current condition and his need for the recommended surgery.  Accordingly, we affirm those findings.

The employer and ESIS also appealed the compensation judge’s determination of apportionment, arguing that if the compensation judge’s findings regarding causation were reversed, the findings regarding apportionment must also be reversed.  Because we have affirmed the findings that there is a causal connection between both of the employee’s injuries and his current medical condition and need for the recommended surgery, there is no basis to reverse the compensation judge’s findings regarding apportionment.  We therefore affirm those findings.