The self-insured employer cross-appeals the compensation judge’s finding that the employee sustained an 18% whole body disability secondary to severe spinal stenosis at the L1-2 spinal level.  We affirm this finding.  The employee appeals the compensation judge’s method of calculation of the amount of permanent disability benefits due.  We modify this portion of the compensation judge’s decision.

Chris M. Addington, the employee, sustained a personal injury on February 1, 1990, while employed by Allina Health System d/b/a Abbott Northwestern Hospital, the employer, then self-insured with claims administered by Gallagher Bassett Services, Inc.  The self-insured employer admitted liability for the employee’s personal injury.

Prior to her personal injury, the employee suffered from non-work-related lumbar spine problems.  In 1986, the employee underwent surgery for a diagnosed L5-S1 disc herniation on the right.  In April 1988, the employee underwent fusion surgery from L5 to the sacrum.  In May 1989, the employee underwent fusion surgery at the L4-5 level.

As a result of her personal injury, the employee underwent several more operations.  In April 1991, the employee had fusion surgery at the L3-4 level.  In June 1992, the employee underwent surgery consisting of placement of an intra-articular catheter at the L2-3 facet joint on the right.  In November 1992, the employee had fusion surgery at the L2-3 level and in September 2003, a repeat fusion surgery was performed at the L2-3 level.  On January 6, 2004, the employee underwent a fusion of the left sacroiliac joint based upon a diagnosis of left sacroiliac joint dysfunction and hypomobility secondary to the spinal fusions from L2 to the sacrum.  The self-insured employer voluntarily paid the employee for a 5% permanent disability for the L3-4 fusion surgery and an additional 5% following the L2-3 fusion surgery.

Dr. Richard Salib diagnosed the employee with a spinal condition called “flat back” that the doctor described as a loss of lumbar lordosis resulting from a degeneration of a spinal disc.  Dr. Salib rated this permanent disability at 10% of the whole body.

In 2007, the parties entered into a stipulation for settlement.  In the settlement agreement, the employee stipulated that she suffered from a 22.5% permanent disability that pre-dated her personal injury.  This rating was comprised of 17.5% for the fusion at L5-S1 and an additional 5% for the fusion at L4-5.  The settlement agreement recites that the employee claimed entitlement to a 22.5% permanent partial disability related to her personal injury representing 17.5% for the L3-4 fusion in 1991 plus 5% for the L2-3 fusion in 1992.  In addition, the employee claimed entitlement to 5% permanent disability for the left sacroiliac joint fusion in 2004, 7% for pain or stiffness at a single vertebral level, and 10% permanent disability for a flat back syndrome.  By way of settlement, the employee agreed to accept a lump sum of $27,500.00 in payment for the claimed permanent partial disability.  In exchange, the employee granted the self-insured employer and the Special Compensation Fund a “close out on permanent partial disability related to the February 1, 1990, lumbar spine injury of 60% to the body as a whole of which 22.5% relates to a preexisting condition prior to February 1, 1990; 17.5% relates to the February 1, 1990, fusion surgery at L4-5 and an additional 5% at L5-S1; 5% related to the alleged consequential left SI joint fusion; 10% related to the consequential alleged “flat back syndrome.”^[2]  An Award on Stipulation was served and filed on February 22, 2007.

Thereafter, the employee brought a claim for permanent partial disability of 18% for spinal stenosis at the L1-2 level.  Following a hearing, the compensation judge adopted the opinion of Dr. Salib that the employee’s stenosis condition at the L1-2 level was severe which qualified for an 18% permanent disability under Minn. R. 5223.0070, subp. 1.C.(2)(1990).^[3]  The self-insured employer appeals this finding.

The compensation judge next determined the total amount of the employee’s permanent partial disability in order to calculate the dollar amount of the benefits to which the employee was entitled, applying the schedules contained in Minn. Stat. § 176.101, subd. 2a.(b).^[4]  The compensation judge first made factual findings regarding the total permanent partial disability that existed prior to the additional 18% for the spinal stenosis.  The judge found that, prior to her February 1, 1990, personal injury, the employee had a preexisting low back permanent partial disability of 21.5%.^[5]  The compensation judge next found that as a result of her personal injury, the employee sustained a 5% whole body disability for fusion surgery at the L3-4 level, an additional 5% whole body disability for the fusion surgery at the L2-3 level,^[6] and a 5% whole body disability attributable to the fusion surgery of the left sacroiliac joint.^[7]  Finally, the compensation judge found the employee was not entitled to any permanent disability for the “flat back” condition rated by Dr. Salib as such a rating would be cumulative.

The compensation judge next concluded the A+B (1-A) formula of Minn. Stat. § 176.105 applied to all of the permanent disability.  To the preexisting disability of 21.5%, the compensation judge added 5% for the L3-4 fusion and 5% for the L2-3 fusion.  After application of the A+B (1-A) formula, the compensation judge determined the employee had a 29.16% whole body disability prior to any additional permanency for the stenosis.  After adding the stenosis rating and applying the formula, the compensation judge found the employee had a total 41.9% permanent partial disability of which 29.16% was settled in the stipulation.  The judge found the employee was entitled to payment for a 12.74% whole body disability (41.9% - 29.16%) for the spinal stenosis.  The compensation judge concluded that based upon the employee’s total permanent partial disability of 41.9%, the 12.74% permanency was payable at the $95,000.00 level, equaling a payment of $12,103.00.  The employee appeals the compensation judge’s method of calculating the amount of permanent partial disability benefits due for the stenosis.

The self-insured employer appeals the compensation judge’s finding that the employee sustained an 18% permanent partial disability for severe spinal stenosis at L1-2.  The employer and the Special Compensation Fund (SCF) point to a September 2003 MRI scan of the employee’s lumbar spine which states, “L1-2: Moderate disk space narrowing, desiccation, disk bulge, and marginal spurring.  A left posterior-lateral disk extrusion is present which results in left lateral recess and foraminal stenosis impinging on the left L2 and L1 nerve roots respectively.  Moderate facet arthrosis.”  (Pet. Ex. M.)  An MRI scan on September 24, 2007, noted “degenerative disc disease at L1-2 with significant thickening of the ligamentum flavum and mild degenerative central stenosis with osteophytic spurring flattening the ventral thecal sac.”  (Pet. Ex. I.)  These scans, the cross-appellants argue, reflect mild central stenosis, not severe stenosis as opined by Dr. Salib.  In his report of September 27, 2007, Dr. Sherman opined the employee suffered from mild left foraminal narrowing and minimal central stenosis at L1-2.  Dr. Sherman opined the employee did not sustain any additional permanent disability to the L1-2 level, noting a lack of specific anatomic findings.  Based upon the MRI scans and Dr. Sherman’s opinion, the employer and the SCF contend the compensation judge’s finding of a 18% permanent disability is unsupported by substantial evidence.  We are not persuaded.

In a November 2004 chart note, Dr. Salib noted the employee was starting to develop pain radiating around her thoracic cage, “which is mostly likely coming from the irritation of the L1 or L2 nerve root caused by the developing spinal stenosis or synovitis of the facet joints.  Chris realizes that more likely than not she will some day require surgery at the L1-2 level. . . .  This problem at the L1-2 level is clearly and unequivocally related to the original work injuries and previous fusion performed.”  (Pet. Ex. E.)  Dr. Salib was deposed on December 27, 2005.  When asked whether the employee would need further surgery, Dr. Salib testified, “[t]he L1-2 level, which I would, you know, certainly feel that at any time that Chris feels that she can no longer tolerate the discomfort and the limitations that she has as a result of the L1-2 degeneration and development of some spinal stenosis at that level, she’ll require a decompression and fusion of L1-2.”  (Pet. Ex. Q at 31.)  By December 2006, Dr. Salib noted the employee’s stenosis had “reached a severe level.”  (Pet. Ex. E.)  By report dated December 20, 2006, Dr. Salib stated the employee had “severe spinal stenosis with bilateral leg symptoms with degeneration at a single level.”  (Pet. Ex. E.)

In August 2007, the employee began treating with Dr. John Heller for urinary urgency and urge incontinence.  The doctor noted these symptoms began following back surgery for the employee’s work injury.  By report dated October 15, 2007, Dr. Heller noted the employee had severe stenosis at L1-2 which was the cause of her urgency and urge incontinence.

On August 27, 2007, Dr. Salib reviewed an MRI scan of the employee’s lower thoracic and lumbar spine, and stated the scan “confirms the fact that she has severe central stenosis at the L1-2 level.  This has changed slightly from the 2004 images in that she has a greater degree of kyphosis.  There is no question that these changes are simply time-related changes because of the fusions that she has had previously related to the work injuries.”  (Pet. Ex. E.)  The employee saw Dr. Salib on October 8, 2007, “to review an MRI scan that was done to assess her increasing symptoms of back pain at the thoracolumbar junction and other symptoms that she is having relating to urinary incontinence and development of right sacroiliac pain.”  The doctor stated, “[t]he new MRI scan shows that there has been progression of the spinal stenosis to now include the T12-L1 level.  The spinal stenosis and the facet changes are simply getting worse.”  (Pet. Ex. E.)

The employee testified that doctors advised her as early as 2003 that she had developed spinal stenosis.  She acknowledged Dr. Salib stated surgery would be necessary to treat the stenosis, but she stated she wished to avoid additional surgery if possible.  The employee testified to persistent bilateral leg pain with an accompanying loss of function that impairs her ability to function in her daily life and to sleep.  The employee also testified she has developed urinary problems which Dr. Heller attributes to the spinal stenosis.

Minn. Rule 5223.0070, subp. 1.C.(2), provides for an 18% rating for “severe spinal stenosis with bilateral leg pain requiring decompressive laminectomy, single vetebral level with or without surgery.”  Under the rule, the stenosis must be proven by computerized axial tomography or myelogram.  In this case, the spinal stenosis is documented on MRI scans performed on May 11, 2004, April 21, 2005, and September 24, 2007.  Dr. Salib opined the employee was experiencing bilateral leg symptoms and had severe spinal stenosis that he rated at 18%.  The employee complained of constant low back pain which caused difficulty walking, sitting, sleeping, and climbing stairs.  In addition, the employee complained of bilateral leg symptoms and urinary incontinence which Dr. Heller attributed to the spinal stenosis.  The compensation judge adopted Dr. Salib’s opinion that the employee’s stenosis at L1-2 was severe.  While Dr. Sherman disagreed, it is the function of the compensation judge to choose between conflicting medical opinions.  See Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985).  The opinions of Dr. Salib were adequately founded and the compensation judge properly relied upon them.  Accordingly, the compensation judge’s award of an 18% permanent partial disability for severe spinal stenosis is affirmed.

   The compensation judge found the employee had a preexisting permanent disability of 21.5 %.  The employer and the SCF contend the compensation judge inadvertently used an incorrect percentage of preexisting permanent partial disability and contend the correct rating should have been 22.5%. The employee agrees.  The compensation judge does not state in the findings and order how the 21.5% rating was determined.  We further note Dr. Salib, Dr. Paul Wicklund, and Dr. John Sherman all opined the employee had a 22.5% permanent partial disability prior to her personal injury, secondary to the two fusion surgeries.  Minn. R. 5223.0070, subp. 1.D., provides a 17.5% rating for a spinal fusion plus an additional 5% for fusion surgery at an adjacent level.  We agree the compensation judge made an inadvertent error and modify his decision to reflect a preexisting permanent partial disability of 22.5%.

   The parties agree the employee’s personal injury resulted in a disability that was attributable, in part, to a preexisting disability.  Accordingly, under Minn. Stat. § 176.101, subd. 4a.(a), the compensation payable for the employee’s permanent partial disability must be reduced by the permanent partial disability attributable only to the preexisting condition.  The parties agreed in the 2007 stipulation for settlement that the employee had a 22.5% preexisting permanent partial disability that was subject to apportionment.  The employee is now entitled to payment for additional permanent disability for the spinal stenosis.  Minn. Stat. § 176.101, subd. 4a.(b), provides the “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.”  Accordingly, to determine the amount of the payment due to the employee for the permanent partial disability for the stenosis, it is necessary to determine the employee’s entire permanent partial disability.

The employee first argues that the compensation judge improperly made findings which recalculated the permanent disability that comprised the 60% permanent partial disability closed out in the stipulation for settlement.  Rather, the employee argues the compensation judge and this court should start with the 60% permanent disability closed out by the stipulation and then add the 18% for the stenosis.^[8]  To do otherwise, the employee argues, would require that in any case in which there is a claim for subsequent permanent disability, the entire matter must be relitigated from the beginning.  Such a procedure, the employee contends, will substantially complicate the later proceedings and require more complex and extended litigation which is contrary to public policy.  We are not persuaded.

Minn. Stat. § 176.101, subd. 4a.(b), provides that payment to the employee for the stenosis must be paid at the rate at which the entire disability would be compensated but for the apportionment.  While the phrase “entire disability” is not defined, the meaning and the intent of the statute is clear.  We reject the employee’s argument that the words “entire disability” includes the amount of the employee’s entire claim in a prior proceeding or the amount of closeout in a prior settlement.  What either party claimed in that prior proceeding is not relevant, nor is the extent of the close out relevant.  Since the employee’s prior claim for permanent disability was settled, there was no determination by a compensation judge as to the employee’s then existing entire permanent partial disability.  We conclude Minn. Stat. § 176.101, subd. 4a.(b), requires the compensation judge to determine the extent of the employee’s entire permanent disability if that disability has not been rated in another proceeding.  Accordingly, the compensation judge properly made findings to determine the permanent partial disability caused by the employee’s personal injury.

   The compensation judge found, in calculating the award for the claimed 18% permanent disability for the employee’s stenosis at the L1-2 level, that the A+B (1-A) formula in Minn. Stat. § 176.105 applied.^[9]  The compensation judge then made the following calculation:

The employee contends the judge’s use of the Minn. Stat. § 176.105, subd. 4, formula was in error because the permanency ratings did not involve separate categories or body parts but rather different sections under the same body part, the low back.  The employee argues the judge’s conclusion that the statutory formula must be applied where all of the permanency is found under the same subpart of the rules is legally erroneous.  The employee asserts she is entitled to be compensated for the 18% permanent disability caused by the stenosis without reduction by the formula.  We disagree.

The employee cites Harrison v. Cleaning Concepts, Inc., 528 N.W.2d 46, 51 W.C.D. 345 (Minn. 1994) and contends it supports her position.  We disagree.  In Harrison, the employee underwent a lumbar decompression and two-level fusion as a result of an injury in Texas in 1984.  In 1990, the employee reinjured his low back at work following which he underwent another decompression and fusion surgery to alleviate a right foot drop and to repair a pseudoarthrosis which resulted from the 1985 fusion surgery which had failed.  A doctor assigned a 22.5% rating for the two-level fusion surgery caused by the 1984 injury.  The doctor further assigned a 13% rating relating to the foot drop that resulted from an L5 nerve root dysfunction resulting from the 1990 injury.  On appeal, the employee challenged the use of the statutory formula to reduce the 13% impairment rating relating to the foot drop from the 1990 injury.  The Supreme Court agreed and held the statutory formula applies only to those situations in which it is necessary to cumulate ratings for impairment resulting from a single occurence.  Because there was no cumulation of ratings for the 1990 injury, the court held Minn. Stat. § 176.105, subd. 4.(c), had no application.  In the present case, as distinguished from Harrison, it is necessary to cumulate ratings for impairment resulting from a single occurrence.

In Deschampe v. Arrowhead Tree Serv., 428 N.W.2d 795, 41 W.C.D. 200 (Minn. 1988), the court was faced with the issue of whether an award of permanent disability under two or more sections of the brain injury subpart of the central nervous system schedule^[11] constituted an impermissible cumulation of lesser included categories.  The court noted that Minn. Stat. § 176.105 focuses not on the body part which sustained direct injury but rather on the resultant permanent functional disability.  The court in Deschampe concluded that where brain dysfunction causes functional losses of use or impairment of different kinds, ratings under more than one category may be necessary to the proper evaluation of the total disability.  The court then held that where an assignment of permanent partial disability ratings under two or more categories was necessary to represent the employee’s disablement, the ratings for the two or more categories of impairment may be combined using the statutory formula of Minn. Stat. § 176.105.

The present case requires the application of ratings under more than one category of the lumbar spine section in order to fully compensate the employee for the disability caused by her personal injury.  In such a case, according to the Deschampe decision, the application of the formula is required.  The compensation judge’s use of the Minn. Stat. § 176.105 formula is, therefore, affirmed.

   While we affirm the compensation judge’s use of the statutory formula, we modify its application.  Following her personal injury, the compensation judge found the employee sustained a 5% permanent partial disability for fusion surgery at the L3-4 level, a 5% permanency for fusion surgery at the L2-3 level, and a 5% permanent partial disability attributable to the fusion surgery of the left sacroiliac joint.^[12]  The compensation judge then applied the statutory formula to reduce the 5% ratings.  This is incorrect.  Minn. Rule 5223.0070, subp. 1.D., provides for a 17.5% rating for fusion surgery and states to add 5% for each additional vertebral level.  When the schedules direct the addition of a particular rating, the statutory formula is not applicable.  O’Connor v. Data Card Corp., 44 W.C.D. 176 (W.C.C.A. 1990); Magariner v. General Cleaning Corp., slip op. (W.C.C.A. Feb. 20, 1998).  Accordingly, the formula does not apply to reduce the 15% permanency encompassing the three 5% ratings.  The formula does, however, apply to reduce the additional 18% permanent disability for the stenosis.  We compute the permanent disability for the stenosis by applying the A + B (1-A) formula to the work-related permanent disabilities of 15% for the fusion surgeries and 18% for the stenosis, as follows:

The employee is entitled to payment for a 15.3% permanent disability for the stenosis. In this case, statutory apportionment under Minn. Stat. § 176.101, subd. 4a, applies to the employee’s preexisting 22.5% permanent disability.  Minn. Stat. § 176.101, subd. 4a.(b), provides the “compensable portion of the permanent partial disability under this section shall be paid at the rate at which the entire disability would have been compensated, but for the apportionment.”  Thus, the employee’s preexisting non-work permanent disability is added to her total work-related permanent disability to determine the impairment rating level at which the permanent disability for the stenosis is payable.  We compute the benefits due as follows:

The compensation judge’s decision is modified as set forth above.  The employer and insurer are ordered to pay to the employee the sum of $18,360.00 for permanent partial disability benefits.