The employee appeals the compensation judge’s findings that the employee sustained a 23% permanent partial disability to the whole body as a result of three work-related injuries that she sustained on August 12, 1997, October 31, 2001, and June 8, 2007, and that 22% of that disability rating should be apportioned pursuant to Minn. Stat. § 176.101, subd. 4a, so that the employee remains entitled to payment based on 1% permanent partial disability of the whole body, to be apportioned equitably between the insurers for her three work injuries.  We affirm in part and modify in part.

For twenty years, between June 1987 and June 2007, Ms. Brenda Settlemire worked as a licensed practical nurse for Innsbruck Health Care Center.  The dispute addressed on appeal arises from three low back injuries that Ms. Settlemire [the employee] sustained in 1997, 2001 and 2007, while employed by Innsbruck [the employer].  At issue is the employee’s claim for payment of benefits based on a rating of 10% permanent partial disability of the whole body - - a rating she claims is due based on the fusion surgery she underwent following her 2007 injury.^[1]

On August 12, 1997, the employee sustained a Gillette^[2] injury to her low back while working for the employer.  The employee had experienced tingling and pain extending from her right buttock area into her right leg since June 1997, and she finally sought medical attention on August 12 to address her pain.  Based on an MRI scan of the employee’s lumbar spine that showed disc herniations at the L4-5 level and L5-S1 levels, Dr. Daniel Ahlberg recommended surgery.  In September 1997, Dr. Ahlberg performed a right L5-S1 lumbar foraminotomy/facetectomy and a right L5-S1 lumbar laminectomy/discectomy, with lumbar spine micro dissection.  By October 25, he released the employee to return to work within restrictions, but because the employer had no available light-duty work, the employee remained off work until late January 1998, when she returned to her full-duty work.  By then, the employee reported that she felt no muscle spasm or tenderness in her low back, that she experienced no radicular symptoms, and that she had an excellent surgical result.

The employer and its insurer, Rampart Insurance Company [Rampart Insurance], denied primary liability for the employee’s injury, asserting that the employee’s condition was not related to her work, and, in November 1998, the employee filed a claim petition, seeking wage loss benefits and payment of medical expenses.

In March 1999, at the request of the employer and Rampart Insurance, Dr. Paul Wicklund examined the employee.  He diagnosed a right L5-S1 disc herniation treated surgically with an excellent result, and concluded that the employee’s work for the employer was a substantial contributing cause to her low back condition and need for surgery.  He concluded that the employee required no further medical care or treatment, and rated her with 11% permanent partial disability of the body as a whole, based on her herniation and surgery at L5-S1.  See Minn. R. 5223.0390, subp. 4.D. and 4.D.(2).^[3]

In November 1999, the parties entered into a stipulation for settlement on a to-date basis, whereby the employer and Rampart Insurance admitted liability for the employee’s 1997 low back injury and surgery and paid various benefits, including medical expenses.  Under the terms of the stipulation, the employer and Rampart issued payment which they stipulated was comprised of approximately twelve weeks of temporary total disability benefits and payment for permanent partial disability benefits based on a rating of 11% whole body impairment.  Following that settlement, the employee continued to work as an LPN for the employer.

On October 31, 2001, the employee sustained another low back injury while working for the employer.  After pulling a patient to apply dressings, the employee noticed a tingling sensation in her right buttock, which was the first time she had noted such symptoms since her 1997 surgery.  She sought medical treatment and underwent an MRI scan that showed a right sided L4-5 disc hernation impinging on her right L5 nerve root.  The employee consulted an orthopedist, Dr. Garry Banks, who diagnosed a right L4-5 disc herniation and lateral recess stenosis.  He concluded that the employee’s work activities were likely a substantial contributing factor to the development of the herniation and need for surgery, and that her condition appeared “to be a separate problem from her prior disc problem which was at the L5-S1 level.”  In December 2001, Dr. Banks performed surgery that included partial laminectomies at the L3-4 and L4-5 levels and microscopic dissection on the  right, from L3 to 5.  The employee eventually was able to return to work without restrictions, and reported an excellent recovery from surgery.

The employer and its insurer at that time, Royal and Sun Alliance Insurance Company [Royal Insurance], denied primary liability for the employee’s claimed 2001 injury.  In March 2002, the employee filed a claim petition for injuries sustained on August 12, 1997, and October 31, 2001, seeking payment of temporary total disability benefits from November 15, 2001, through January 14, 2002, payment of medical expenses, and payment of permanent partial disability benefits.  The employer and both insurers denied the claims against them, each insurer asserting that the employee’s injuries and condition resulted from an injury sustained during the other’s period of coverage.

In January 2003, Dr. William Simonet examined the employee at the request of the employer and Rampart Insurance.  He concluded that the employee’s 1997 work injury caused a right L5-S1 disc herniation and necessitated her 1997 surgery, and that the employee’s 2001 work injury necessitated her surgery in December 2001.  He also remarked that the employee had received excellent results from each of her surgeries, and recommended no further medical care or treatment.

In May 2003, Dr. David Boxall examined the employee at the request of the employer and Royal Insurance.  He concluded that the employee had not sustained an injury in October 2001, but that the employee’s herniated disc at L4-5 had spontaneously worsened, basing his opinion on the lack of contemporaneous medical records in 2001 referring to an injury at work or work activities causing an injury.  In response to an inquiry about permanent partial disability, however, Dr. Boxall concluded that it was unclear from the schedule whether the employee would be rated for a separate new injury at a different level, which would require an additional 11% permanent partial disability for her separate lesion and herniation at the L4-5 level, or whether she should be rated for an additional surgery under the previous rating, which would result in an additional 2% permanent partial disability under Minn. R. 5223.0390, subp. 4.D.(3).

In December 2003, the employee, the employer, Rampart Insurance and Royal Insurance entered into a stipulated settlement on a to-date basis, settling the employee’s claims related to her 1997 and 2001 injuries.  The employer and its respective insurers admitted primary liability for those injuries, and issued payment to the employee and paid medical expenses on her behalf, under terms delineating the proportionate share each insurer would pay.^[4]   The parties agreed to close out claims on a to-date basis, including claims for temporary total disability benefits for approximately eight weeks, medical expenses, and benefits to the extent of an 11% permanent partial disability rating.  The employee returned to her regular work for the employer as an LPN.

The employee sustained a third low back injury on either June 6 or 8, 2007.  She noted low back pain while working on June 6, and, on June 8, she sustained a low back injury while lifting a box of supplies at work.  Positive findings from an MRI scan taken in June 2007 included disc degeneration from L4 to S1, a broad disc protrusion at the L4-5 level, a small right L5-S1 disc herniation, and lateral recess stenosis at both the L4-5 and L5-S1 levels.  The employee returned to Dr. Banks, who recommended surgery and, on July 18, 2007, performed surgery that included, among other procedures, a posterior revision decompression L4 to S1, a posterior interbody fusion L4 to S1 and posterior intertransverse fusion L4 to S1.  In his surgical report, Dr. Banks stated that “the procedure was considerably more difficult than usual as a result of the severe peridural fibrosis and neural impingement at both levels as well as the need to initially try to preserve spinal stability.” The employee reportedly had a good result from that surgery, but, as of the time of the hearing in November 2008, had not yet returned to work.

The employer and its insurer at that time, Benedictine Group, denied primary liability for the alleged June 8, 2007, injury, asserting that the employee had not reported a specific incident, that no evidence showed that she had sustained a new injury, and that the employee’s condition was likely a natural progression of her earlier injuries.  In August 2007, the employee filed a claim petition for injuries sustained on August 12, 1997, October 31, 2001, and June 8, 2007, seeking wage loss benefits, payment of medical expenses, and additional permanency benefits based upon a 10% rating related to the employee’s fusion surgery.  The employer and its insurers objected to the petition, denying primary liability for the employee’s June 8, 2007, injury and for the claimed benefits.

During the course of the ensuing litigation, the employee attended three independent medical examinations.  In November 2007, Dr. Jeffrey Dick examined the employee at the request of the employer and Benedictine Group, the insurer at the time of the employee’s 2007 injury.  He diagnosed the employee’s condition as degenerative disc disease that had been accelerated by her 1997 and 2001 injuries.  He concluded that she had sustained neither a Gillette nor a specific injury in June 2007, and that her degenerative condition was attributable to her injuries in 1997 and 2001.  Dr. Dick apportioned 50% liability to each of those injuries for the employee’s wage loss and need for medical treatment in 2007.  He also concluded that the employee had sustained 23% permanent partial disability as a result of her 1997 and 2001 injuries.  See Minn. R. 5223.0390, subp. 4.D., subp. 4.D.(2), 4.D.(3), and 5.B.

In January 2008, Dr. Boxall re-examined the employee on behalf of the employer and its insurer at the time of the employee’s 2001 injury.  Dr. Boxall concluded that the employee’s pre-existing condition - - her disc excisions at the L4-5 and L5-S1 levels - - as well as her June 2007 injury substantially contributed to her time off work in 2007 and her need for medical treatment.  Dr. Boxall concluded that the employee would be entitled to payment of an additional 10% permanent partial disability “above and beyond any permanency that she was previously provided,” based on her 2007 fusion surgery.^[5]  Dr. Boxall apportioned the liability for benefits among all three injuries, including temporary disability benefits, need for medical treatment and additional permanent partial disability, as follows:  35% due to the 1997 injury, 35% due to the 2001 injury, and 30% due to the 2007 injury.

Dr. Simonet also re-examined the employee in January 2008, and concluded that her current condition and 2007 surgery were a “natural progression of degenerative disc disease accelerated by her 1997 and 2001 work injuries.”  He concluded that she had not sustained a Gillette or specific injury in June 2007, but that, instead, her degenerative condition was attributable to her earlier injuries.  He assigned a combined permanency rating of 23%, and attributed liability for portions of that rating as follows:  11%, based on Minn. R. 5223.0390, subp. 4.D. and 4.D.(2), attributed to the 1997 injury; 2%, based on Minn. R. 5223.0390, subp. 4.D.(3), attributed to the 2001 injury, and 10%, based on Minn. R. 5223.0390, subp. 5.B, attributed equally between the 1997 and 2001 injuries.

In February 2008, Dr. Banks, the employee’s treating surgeon, concluded that the employee sustained 11% permanent partial disability as a result of her 1997 injury, and agreed with Dr. Boxall that the employee was entitled to an additional 10% rating resulting from her fusion surgery.  He concluded that liability for the additional 10% permanency should be apportioned equally among all three of the employee’s work injuries.

Under the terms of a Temporary Order issued on April 18, 2008, the employer and Royal Insurance, the insurer at the time of the employee’s 2001 injury, paid wage loss benefits and medical expenses to and on behalf of the employee.

A hearing was held on August 15, 2008, to address the employee’s claims for payment of temporary total and temporary partial disability benefits following her 2007 injury, for medical expenses incurred following that injury, and for benefits based on an additional 10% permanent partial disability.  At issue before the compensation judge was whether the employee’s 1997 and 2001 injuries, as well as her continued work, culminating on or about June 6, 2007, and her specific lifting injury on June 8, 2007, substantially contributed to her disability and need for a fusion surgery in 2007.  The insurers at the time of the employee’s 1997 and 2001 injuries contended that the employee had resumed her full activity and work following those injuries, and that it was her 2007 injury alone that resulted in the employee’s disability and need for medical care following that last injury.  The insurer at the time of the employee’s 2007 injury denied liability for the employee’s condition.

In her findings and order of November 7, 2008, and relevant to this appeal, the compensation judge found:

The employee appeals from the finding that she is entitled to payment of permanency benefits limited to an additional 1% permanent partial disability of the body as a whole.

The compensation judge found the employee sustained a total of 23% permanent partial disability as a result of her personal injuries in 1997, 2001, and 2007.  The compensation judge further found this 23% permanent disability was subject to apportionment under Minn. Stat § 176.101, subd. 4a.  The judge found that under the “1999 and 2003 Stipulations for Settlement, the employee was paid 11% permanent partial disability benefits for her 1997 work injury and to the extent of 11% permanent partial disability for the 2001 work injury.” (Finding No. 23).  The judge then found the employee’s pre-existing permanent disability of 22% was to be apportioned or subtracted from her current permanent partial disability of 23% and concluded the employee was entitled to payment for a 1% permanent partial disability.  The employee appeals this finding and argues that as a result of her 2007 personal injury and the related fusion surgery necessitated by that injury, she is entitled to payment for an additional 10% permanent partial disability.  The employee argues statutory apportionment is not appropriate in this case and should not be applied to reduce her entitlement to the 10% permanent partial disability rated under Minn. R. 5223.0390, subp. 5.B.

In this case, five doctors rendered opinions regarding the extent of the employee’s permanent disability.  Dr. Paul Wicklund examined the employee in 1999 and opined that as a result of the 1997 personal injury, the employee sustained an 11% permanent disability rated under Minn. R. 5223.0390, subp. 4.D. and subp. 4.D.(2).  Dr. Dick examined the employee in 2007 and opined the employee did not sustain an injury in June 2007.  The doctor rated a total of 23% permanent partial disability caused by the 1997 and 2001 injuries.  This rating was comprised of a 9% rating for radicular pain or radicular paresthesia under Minn. R. 5223.0390, subp. 4.D., plus an additional 2% for the discectomy at L5-S1 under subp. (2) of the rule, 2% permanent disability under subp. 4.D.(3) of the rule for the second surgery in 2001, and 10% permanent partial disability under subp. 5.B. of the rule for the 2007 fusion surgery.  Dr. David Boxall first examined the employee in 2003.  Dr. Boxall agreed with Dr. Wicklund that the employee had an 11% permanent disability rating for the surgery at L5-S1 secondary to the 1997 injury.  The doctor was unclear, however, what the rating was for the second surgery in 2001 at the L4-5 level.  The doctor stated the employee would either be entitled to an additional 2% for the second surgery under Minn. R. 5223.0390, subp. 4.D.(3), or if the second surgery were to be rated as a new, separate condition, the rating would be 11% under subp. 4.D.(2) of the rule.  Dr. Boxall reexamined the employee in 2008 and rated the employee as having a 10% permanent partial disability for the fusion surgery in 2007.  The doctor stated this 10% permanent disability “would be above and beyond any permanency that she was previously provided to the lumbar spine. . . .”  (Cambridge Ex. 1.)  Dr. John Simonet examined the employee in 2008 and provided permanency ratings.  Dr. Simonet ascribed 11% to the 1997 injury, 2% to the 2001 injury, and 10% due to the 2007 fusion surgery.  Finally, Dr. Banks, the treating physician, rated the employee with a 10% permanent partial disability for the 2007 fusion surgery.

Dr. Banks, Dr. Boxall, Dr. Dick, and Dr. Simonet each opined the employee was entitled to a 10% permanent partial disability secondary to the 2007 fusion surgery under Minn. R. 5223.0390, subp. 5.B.  The compensation judge agreed and found the employee sustained a 10% disability secondary to the fusion surgery under Minn. R. 5223.0390, subp. 5.B.  No party contends this finding of a 10% rating is erroneous or unsupported by substantial evidence.  Rather, the employee contends that if Minn. Stat. § 176.101, subd. 4a, apportionment is applicable, the employee has a 32% total permanent disability rather than 23% as found by the compensation judge.  Thus, utilizing the compensation judge’s theory of apportionment and deducting 22% from the employee’s total permanent disability, the employee asserts she remains entitled to payment for a 10% permanent partial disability.  Alternatively, the employee contends statutory apportionment is not appropriate at all and the statute should not be applied to reduce her entitlement to the 10% permanent disability admittedly attributable to the 2007 fusion surgery.

Following the 2007 injury, the employee underwent a third surgery, a fusion at multiple levels of the spine.  Minn. R. 5223.0390, subp. 5.B. is clear that a fusion at multiple levels is rated at the 10% whole body disability.  In this case, Dr. Dick, Dr. Boxall, Dr. Simonet, and Dr. Banks all opined the employee sustained a 10% permanent disability for her 2007 multiple level fusion surgery.  The compensation judge agreed and found the employee sustained a 10% whole body disability under Minn. R. 5223.0390, subp. 5.B.  That finding is supported by substantial evidence and is affirmed.

We next turn to the issue of the compensation judge’s application of the doctrine of apportionment under Minn. Stat. § 176.101, subd. 4a.  The employee contends that she sustained three discrete injuries, separated by a period of years, each involving different and separately ratable conditions.  In reliance on the cases of Fleener v. CBM Indus., 564 N.W.2d 215, 56 W.C.D. 495 (Minn. 1997), and Clasen v. Pro Floor, Inc., No. WC07-242 (W.C.C.A. Mar. 25, 2008), the employee contends the compensation judge erroneously utilized statutory apportionment to reduce the 10% permanent disability which she sustained as a direct result of the 2007 fusion surgery.

Prior to the enactment of Minn. Stat. § 176.101, subd. 4a, in 1983, there was no apportionment between pre-existing non-work conditions and work injuries.  If a work injury aggravated such a pre-existing condition, the employer and insurer were liable for all of the permanent disability which resulted.  See, e.g., Wallace v. Hanson Silo Co., 305 Minn. 395, 235 N.W.2d 363, 28 W.C.D. 79 (1975); Vanda v. Minnesota Mining & Mfg. Co., 300 Minn. 515, 218 N.W.2d 458, 27 W.C.D. 379 (1974).  Minn. Stat. § 176.101, subd. 4a, allows the compensation payable for a permanent partial disability to be reduced by the portion of the permanent disability attributable to the pre-existing disability.  The statute, however, also provides authority for apportionment for pre-existing work-related disabilities.  In this regard, the purpose of subdivision 4a is less clear.^[7]

This case again highlights the difficulty of application of Minn. Stat. § 176.101, subd. 4a, to permanent partial disability resulting from multiple work injuries.  This difficulty is especially evident in cases involving permanent disability ratings for surgical procedures.  In the present case, the employee’s 1997 and 2001 injuries were separate injuries to different levels of the employee’s spine.  Each injury required surgery and each surgery is separately rated under the permanency schedule.  As a substantial result of the employee’s 2007 injury, she underwent a third surgery, a multi-level fusion.  A fusion at multiple levels is specifically rated at 10% under Minn. R. 5223.0390, subp. 5.B.  Apportionment under Minn. Stat. § 176.101, subd. 4a., is applicable if “a personal injury results in a disability which is attributable in part to a preexisting disability.”  Since the permanent disability resulting from a multi-level fusion surgery is separately rated under the rules, we have difficulty understanding how the 10% permanent disability is “attributable in part to a preexisting disability.”  The fact that the employee underwent two different surgeries before the fusion surgery does not lessen or minimize the effect on the employee of the fusion surgery.  We acknowledge there is merit to the employee’s argument that this case is not about the allocation of responsibility for permanent disability between a preexisting condition and a subsequent work injury, but is more about attributing to a single work injury the permanent disability resulting from that injury.

Based upon the facts of this case, however, we cannot conclude the compensation judge’s application of the doctrine of statutory apportionment was clearly erroneous.  We do not agree, however, with the compensation judge’s application of the doctrine.  The compensation judge apparently adopted the opinion of Dr. Simonet and found the employee was entitled to three separate permanent disability ratings for her three injuries: 11% permanent disability from the 1997 injury, 2% permanent disability from the 2001 injury, and a 10% permanent disability from the 2007 injury. In another finding, however, the compensation judge found the employee had a preexisting permanent partial disability of 22%.  These two findings are irreconcilable.  The employee’s preexisting disability is either 13% or 22%.  In this case, the employee’s permanent disability from the 1997 and 2001 personal injuries was not previously rated in any proceeding so, applying the doctrine of statutory apportionment, the compensation judge was required to rate the preexisting disability.^[8]  Dr. Simonet’s opinion that the employee had 13% permanent disability prior to 2007 was adopted by the compensation judge.  The judge’s finding to that effect is supported by substantial evidence and is affirmed.

The compensation judge found the employee was entitled to payment of permanent disability for her fusion surgery only to the extent that it exceeded the 22% to which the employee claimed entitlement in the two prior proceedings.  A reduction to the extent of the employee’s claim or to the extent of a close out in a prior proceeding is not statutory apportionment.  Rather, the compensation judge’s 22% reduction appears to be based on some form of credit theory in which the insurers for the first two injuries, by reason of their settlements with the employee, get a credit against the employee’s current claim for permanent disability.  We find no statutory basis for such a theory and we reverse this finding.  The employee’s preexisting disability was only 13% so the compensation judge erred in reducing the employee’s total permanent disability by 22%.  The employee’s permanent disability can only be reduced by the amount of the pre-existing disability, 13%, resulting in 10% permanent partial disability remaining to be paid to the employee.  We find no basis to give either insurer a credit against the 10% permanent disability due the employee for the fusion surgery because of the prior settlements.  In both 1999 and 2003, the employee claimed entitlement to an 11% whole body impairment.  Both cases were settled without an adjudication of the amount of permanent disability to which the employee was entitled.  Those payments were to settle the disputes which then existed.  No portion of the payment in either Stipulation for Settlement was or could be payment for some then unknown permanent disability which might arise in the future.

We affirm the compensation judge’s finding that equitable apportionment applies to the 10% permanent disability for the 2007 fusion surgery.  Where multiple injuries to the same body part result in a single permanency rating, representing a condition which is cumulative and essentially indivisible result of the multiple injuries, the principles of equitable apportionment determine liability for the employee’s current permanent partial disability.  Rauschendorfer v. Q. Carriers, Inc., 56 W.C.D. 241 (W.C.C.A. 1996), summarily aff’d (Minn. Feb. 28, 1997).  The compensation judge’s finding that equitable apportionment applies is amply supported in the medical records, including the opinion set forth by Dr. Banks - - accepted by the compensation judge - - and, in a similar fashion, by the opinion set forth by Dr. Boxall.

Minn. Stat. § 176.101, subd. 4a.(b), states, “[t]he compensable portion of the permanent partial disability under this section shall be paid at the rate at which the entire disability would be compensated but for the apportionment.”  The employee’s entire disability is 23% which is payable at the impairment rating level of 21 to 25% and an amount of $95,000 under Minn. Stat § 176.101, subd. 2a.  The employee is awarded $9,500.00 (10% x $95,000) for the 10% permanent disability due.  Each insurer shall pay the employee one-third of this award.