DANIEL T. GEARY, Employee, v. MCNEILUS TRUCK & MFG. and KEMPER INS. CO. n/k/a BROADSPIRE, Employer-Insurer/Appellants, and MCNEILUS TRUCK & MFG. and CNA COMMERCIAL INS., Employer-Insurer/Cross-Appellants, and MAYO FOUND. and HEALTHPARTNERS, Intervenors.

 

WORKERS' COMPENSATION COURT OF APPEALS

OCTOBER 27, 2005

 

No. WC05-185

 

HEADNOTES

 

PRACTICE AND PROCEDURE - DATE OF INJURY.  Under the particular circumstances of this case, where the employer and insurer had reason to know that the date of the employee's alleged work injury was uncertain, the compensation judge did not err by selecting a date of injury somewhat different than the date designated on the employee's claim petition.

 

CAUSATION - SUBSTANTIAL EVIDENCE.  Substantial evidence, including expert opinion, reasonably supported the compensation judge's decision that the employee sustained a permanent injury in an incident at work that caused or substantially contributed to the employee's L1-2 disc herniation and subsequent disability and need for medical treatment.

 

APPORTIONMENT - PERMANENT PARTIAL DISABILITY.  The compensation judge did not err in denying the employer and insurer's request for apportionment for preexisting permanent partial disability, where the record reasonably established that the preexisting condition was either not ratable or else that it constituted an impairment separate and distinct from the impairment caused by the work injury for which the employer and insurer were liable.

 

Affirmed as modified.

 

Determined by: Wilson, J., Rykken, J., and Stofferahn, J.

Compensation Judge: Kathleen Behounek

 

Attorneys:  Thomas R. Patterson, Patterson, Ostrem & Swisher, Rochester, MN, for the Respondent.  David J. Klaiman, Aafedt, Forde, Gray, Monson & Hager, Minneapolis, MN, for the Appellants.  Mark A. Kleinschmidt, Cousineau, McGuire & Anderson, Minneapolis, MN, for the Cross-Appellants.

 

 

OPINION

 

DEBRA A. WILSON, Judge

 

The employer and Kemper Insurance Company^[1] appeal from the compensation judge's finding that the employee sustained a permanent work-related injury "on or about" September 2, 2002, and from the judge's resulting apportionment of liability for wage loss and medical expense benefits.  The employer and CNA Commercial Insurance Company cross-appeal from the judge's denial of their credit claim for preexisting permanent partial disability and from the judge's finding as to the amount of HealthPartners' intervention interest.  We modify the judge's decision as to HealthPartners' intervention interest but affirm on all other issues.

 

BACKGROUND

 

The employee began working for McNeilus Truck & Manufacturing [the employer] in about 1975.  The employer builds cement and dump-box trucks, and the employee worked first as a saw operator and then as a press operator before moving to a welding job, welding mixing blades inside cement truck drums.  This welding job apparently required the employee to work in awkward or bent-over positions at times.  The records indicate that the employee received intermittent chiropractic treatment for low back symptoms in 1980, around the time he apparently transferred to the welding position.  Later, in 1983, he sought chiropractic care for low back symptoms following two apparently minor incidents at work.

 

On May 11, 1984, the employee sustained a work-related low back injury while lifting a 60-pound hydraulic tool used in his welding job.  He was subsequently off work for about a month and received additional chiropractic treatment for low back and left leg pain.  Sometime shortly after returning to his welding job, the employee asked for and was granted a transfer to a different position with the employer, later testifying that his pre-injury welding job had irritated his low back symptoms.  Chiropractic records indicate that Dr. Lon Meyer, the employee's chiropractor, had recommended that the employee be allowed to change jobs "where the constant bent over position does not have to be maintained."  The new job required some heavy lifting but apparently allowed the employee to avoid positions that aggravated his symptoms.

 

The employee continued to receive regular chiropractic care for low back and leg pain over the next several years.  However, he was not subject to any formal restrictions.  The employee testified that the ongoing chiropractic treatment allowed him to continue working but that his symptoms never completely resolved.  He was also seen for treatment at the Mayo Clinic.

 

In November of 1985, the employee underwent a lumbar CT scan, which disclosed the following findings relative to L5-S1:

 

L5-S1: Moderate, central, posterior and superior disc material  herniation encroaching on the dural sac and the origin of the traversing S1 nerve roots and causing moderate central stenosis with the AP diameter less than 10 mm.

 

Mildly, congenitally short pedicles with mild secondary lateral recesses stenosis, minimal thickening of the ligamenta flava and mild subarticular stenosis secondary to moderate facet joint degenerative disease are enhancing the pathological abnormality.

 

With regard to the L4-5 level, the radiologist's report reads as follows:

 

L4-L5:  No disc tissue herniation or direct neural element involvement at this level.

 

Congenitally short pedicles with secondary moderate lateral recesses stenosis, subarticular stenosis secondary to moderate facet joint degenerative disease and thickening of the ligamenta flava is more prominent at this level, but is not causing central stenosis.

 

Mild, symmetrical, posterior and lateral disc bulging is narrowing slightly the intervertebral foramina at this level, but no evidence of L4 nerve root involvement.

 

As for L3-4, the scan detected "[m]ild, symmetrical, posterior and lateral dis[c] bulging . . . not causing central stenosis, intervertebral foraminal narrowing or neural element involvement."  In conclusion, the radiologist reported as follows:

 

Herniation of L5-S1 disc material posteriorly and superiorly encroaching on the dural sac and origin of the S1 traversing nerve roots.

 

Congenitally short pedicles, moderate facet joint degenerative disease and mild thickening of the ligaments flava are causing mild lateral recesses stenosis, subarticular stenosis and mild narrowing of the intervertebral foramina at the levels of L4-L5 and L5-S1.

 

Normal neural element at the levels of L4-L5 and L3-L4.

 

In early 1988, the employee was paid benefits, for a 9% whole body impairment, by Home Insurance Company, the employer's workers' compensation insurer at the time of the employee's 1984 work injury.  According to the notice of permanent partial disability benefit payment filed with the Department of Labor and Industry, those permanent partial disability benefits were paid pursuant to Minn. R. 5223.0070, subp. 1B(1)(a)(1984), a rule then applicable to a herniated disc, not surgically treated, with scan results specifically positive for herniated disc, and excellent results, with resolution of objective neurologic findings.  The payment notice also indicated that payment had been made based on the November 1985 CT scan report and a November 13, 1987, report by Dr. L.F.A. Peterson, who was one of the employee's treating physicians at the Mayo Clinic.  In that report, Dr. Peterson had written that the employee had last been seen on April 13, 1987, and that,

 

[a]t that time the patient was noted to be working 12 hours a day.  There was no functional disability related to his low back.  A neurosurgical evaluation indicated no need to consider surgery.  I cannot comment on the severity of the disk herniation that was possibly showing in 1985 on outside CT scan.

 

The frequency of the employee's chiropractic treatment diminished in 1988.  The employee testified that he sought care less often because his symptoms had substantially improved by then.  However, the employee was seen again at Mayo for low back and leg pain in early 1989.^[2]

 

Also in 1989, the employee transferred to a shipping job, at the employer, for reasons unrelated to his low back condition.  This job involved loading trucks both with a forklift and manually.  The employee testified that the work was physically demanding but that he was able to perform this job with no increase in his back symptoms.

 

On December 11, 1989, the employee fractured his wrist and injured his low back again in a fall at work.  Less than two months later, on February 1, 1990, he underwent surgery, a partial hemilaminectomy, medial facetectomy, and foraminotomy, at L4-5 on the left.^[3]  He subsequently returned to work, with restrictions, in April of 1990, and eventually resumed his pre-injury shipping job.  CNA Commercial Insurance Company, the employer's workers' compensation insurer at the time of the employee's December 1989 fall, paid various benefits related to this injury.

 

The employee's low back symptoms worsened over time, after his February 1990 surgery, and an MRI scan performed on December 6, 1991, disclosed a disc protrusion and free disc fragment at L4, as well as "congenital central canal stenosis of the lumbar spine" and a "bulging annulus, particularly on the right side at the L3 level produc[ing] mild to moderate central canal stenosis."  On February 19, 1992, the employee underwent hemilaminectomies and facetectomies with fusion from L3 to L5.  The two conditions noted on the surgical report were "congenital lumbar stenosis" and "[r]ecurrent protruded intervertebral disk, left fourth lumbar."

 

After his fusion surgery, the employee was off work for about a year and then returned to employment with the employer in a job ordering parts.  This job was not physically strenuous, and the employee worked reduced hours for some time before returning to a full-time schedule.  He missed work intermittently because of continuing low back pain and continued to receive periodic treatment for his symptoms.  The employer and CNA ultimately paid the employee benefits for 22.5% whole body impairment under the permanent partial disability rule then applicable to two-level fusion surgery.

 

In January 2002, the employee underwent an MRI scan and an EMG because of continued low back pain and radiculopathy.  The MRI scan disclosed multilevel degenerative changes and

 

L1-2 broad based disk stable.  Mild broad based disk bulge flattening ventral thecal sac with mild central canal narrowing.  L2-3, broad based disk bulge with prominent facet arthropathy causes moderate to severe central canal narrowing minimally progressed from the previous exam.  L3-4, mild degenerative disk disease, no significant central canal narrowing.  L4-5, no significant central canal narrowing.  L5-S1, demonstrated a broad based disk bulge which is eccentric to the left and effaces the fat adjacent to the exiting left L5 nerve root.  Moderate spondylotic changes in the facets without significant central canal narrowing.

 

The EMG disclosed "L4-S1 radiculopathies bilaterally, with evidence of ongoing denervation and reinnervation at least in L5 muscles."  A few months later, in April of 2002, the employee underwent a lumbar CT with myelogram.  The radiologist read that test as revealing a "diffuse disc bulge at L1-2 with small focal disc extrusion into the left lateral recess," which "could compromise the transversing left L2 nerve root," spondylosis and a diffuse disc bulge at L2-3, and spondylosis and a diffuse bulge at L5-S1.  By this time, diagnoses applied to the employee's condition included failed back syndrome.

 

On September 9, 2002, the employee sought treatment at a local clinic for worsening back pain.  The treatment note from that consultation reads, in part, as follows:

 

S:  46-year old presents with one-week history of worsening lower back pain.  Pain is sharp, knife-stabbing in the lower back moving from right side to left side over the last week.  He thinks it may have started when riding around in his motorized cart at work, and he hit a pothole.  This was on 9/2/02.  Pain was at its worst this morning radiating down his left leg to just above the knee.  Denies changes in bowel or bladder.  Uses a Tens unit without relief.  Also uses Ultram, which also offers little relief.

 

The employee was diagnosed as having a lower back muscle strain, and it was noted that he planned to follow up with his doctor at Mayo as soon as possible.

 

A few days later, on September 13, 2002, the employee was seen at the emergency room of a Mayo Clinic hospital, complaining of severe back pain.  The admission record indicates that the employee had reported that his back pain had gradually worsened over the "last weeks" and that, "[t]his a.m., the patient was up and went back to bed; some minutes later he tried to stand up again, but according to the patient, he felt something popping with severe worsening of his back pain with radiation to his left leg."  Hospital records further indicate that an MRI performed on September 14, 2002,

 

showed [that] since his prior MRI, the patient developed a large left-sided disk extrusion at the L1-L2 level.  The extrusion extended inferiorly to the level of the left L2 lateral recess.  Disk material abutted and deformed the left side of the thecal sac at the L1-L2 levels.

 

The employee subsequently received an epidural steroid injection and reportedly experienced relief of his left-sided pain.  According to an MRI scan performed about a year later, in August of 2003, the L1-2 disc extrusion noted on the September 2002 scan had "nearly completely resolved."  The employee continued, however, to experience low back and leg symptoms.

 

When the matter came on for hearing on February 18, 2005, the employee alleged entitlement to various benefits as a result of the admitted work injury of December 11, 1989, for which CNA was liable, and a work injury allegedly occurring, according to the claim petition, on September 9, 2002, when Kemper was on the risk for workers' compensation liability.^[4]  During the course of the hearing, it became apparent that the employee was in actuality claiming an injury date, related to riding in the cart at work, sometime shortly prior to September 9, 2002, and that he did not recall the specific date of the incident.  Other issues included whether CNA was entitled to a credit for preexisting permanent partial disability, and apportionment of liability for wage loss and certain medical expenses.  Evidence included the employee's medical records and causation opinions from independent medical examiners Dr. Mark Friedland and Dr. Paul Wicklund.  Dr. Friedland testified, in part, that the employee had not sustained any injury in the September 2002 work incident and that  the employee's L1-2 disc condition was causally related to the employee's preexisting degenerative disc disease and the 1992 fusion surgery.  Dr. Wicklund, in contrast, reported that the September 2002 incident had caused the L1-2 herniation disclosed on the September 14, 2002, scan.  Dr. Wicklund also indicated that the employee's 1984 injury had contributed to the employee's need for the 1992 fusion procedure.

 

In a decision issued on April 25, 2005, the compensation judge concluded, in relevant part, that the employee had sustained a permanent work-related injury to his low back "on or about September 2, 2002," that the employee's 1989 work injury and his 2002 work injury were both substantial contributing causes of the employee's need for treatment from March 27, 2003, through the date of hearing; that liability for those treatment expenses should be apportioned 30% to Kemper for the 2002 injury and 70% to CNA for the 1989 injury; that Kemper was solely liable for a short period of temporary total disability in September of 2002; and that, because apportionment for preexisting permanent partial disability was not appropriate, CNA was not entitled to a credit based on their payment of benefits for a 22.5% impairment following the employee's 1992 fusion surgery.  CNA and Kemper appeal.

 

STANDARD OF REVIEW

 

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 (2004).  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 the 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).

 

DECISION

 

1.  September 2002 Work Injury

 

The employee testified that he experienced an increase in low back pain, as well as pain radiating into his right leg, when the three-wheeled cart he was driving at work hit a pothole in the yard.  On his claim petition, the employee designated the date of this injury as September 9, 2002.  However, the September 9, 2002, office note from the employee's family practice clinic indicates that this incident occurred on "9/2/02."  At hearing, Kemper's attorney pointed out to the compensation judge that September 2, 2002, was Labor Day, and the employee acknowledged that he did not work on that date.  During questioning about the timing of the alleged cart incident, the employee essentially conceded that he could not remember exactly when the incident occurred, but he was certain that it had occurred at work and that he had not injured himself in any way at home.  The employee also testified that he had reported the incident to three people at work, including his foreman, on the date that it happened.

 

In her decision, the compensation judge concluded that the employee had sustained an injury "on or about" September 2, 2002, and, relying on the opinion of Dr. Wicklund, the judge determined that the injury was permanent and had substantially contributed to the employee's disability and need for medical treatment for the periods at issue.  On appeal, Kemper argues primarily that the judge erred in finding an injury occurring "on or about September 2, 2002," when that date of injury was never alleged by the employee in a pleading, and that the judge erred as a matter of law by relying on the opinion of Dr. Wicklund and by "shifting the burden of proof from the employee onto the employer and this insurer."  We are unpersuaded.

 

When one specific date of injury is pled, it may not be reasonable to expect an employer and insurer to prepare defenses against claims involving alternative injury dates, and judges should as a rule refrain from choosing dates of injury not litigated by the parties.  Certainly, in this particular case, it would have been helpful had the employee alleged alternative dates or else indicated, on his claim petition, that the precise date of the claimed injury was uncertain.

 

At the same time, however, counsel for the employer and Kemper should have been aware that the September 9, 2002, date alleged in the claim petition was either erroneous or approximate, in that the employee's September 9, 2002, medical record referred to September 2, 2002, as the date of injury.  Similarly, counsel for Kemper was almost certainly aware, prior to hearing, that September 2, 2002, was in fact Labor Day, a day on which the employee did not work.  Moreover, Kemper did not raise notice of injury as a defense to the employee's claim, and Kemper's counsel neither called witnesses nor asked for additional time to refute the employee's testimony that he gave notice of injury, on the date the incident occurred, to three representatives of the employer, including the employee's foreman.  Under these particular circumstances, we cannot help but be skeptical of the employer and Kemper's claim that they would have prepared an entirely different defense had they known that a different injury date might be selected by the judge.

 

Basic fairness requires that parties be afforded reasonable notice and an opportunity to be heard before benefit decisions are made.  Kulenkamp v. Timesavers, Inc., 420 N.W.2d 891, 894, 40 W.C.D. 869, 872 (Minn. 1988).  In the present case, the employer and Kemper clearly had reason to suspect, prior to hearing, that the date of the employee's alleged work injury was uncertain, and discovery was available to clear up any question in this regard.  In fact, the employee's deposition was taken.  When it became even more apparent, at hearing, that the employee did not really know the precise date, the employer and Kemper did not ask the judge for the opportunity to submit additional evidence on the issue.  Rather, now, they simply assert, without any real explanation, that their defense would have been different had they known of the issue as to date.  We believe that, under the circumstances, the employer and Kemper had sufficient information to defend the claim, and we decline to vacate or otherwise modify the judge's decision on this basis.

 

We are also unconvinced by Kemper's contention that the judge erred in relying on the April 22, 2003, causation opinion of Dr. Wicklund, who concluded that the September 2002 incident, in which the employee hit the pothole while riding the cart at work, had caused an L1-2 disc herniation.  It is true that Dr. Wicklund issued his opinion to this effect prior to the August 2003 scan, which indicated that the L1-2 herniation had "nearly completely resolved."  However, the fact that one test showed that a herniation had nearly resolved does not necessarily establish that the 2002 work injury was not permanent.

 

Finally, the employer and Kemper contend that the following statement by the judge establishes that she "effectively shifted the burden of proof":

 

Dr. Friedland's opinion [was] that the employee's L1-2 disc herniation may have been the result of the employee getting up from bed, as noted in the September 9, 2002 [sic] Mayo Clinic records.  However, he does not explain how the employee's getting out of bed would have produced more stress on the spine, causing the disc to herniated [sic], as compared to the employee jarring and twisting his back when the cart he was riding in hit a pothole.

 

Again, we are not persuaded by Kemper's arguments.  It is clear to us that the judge was simply explaining why she found Dr. Friedland's opinion to be unconvincing.

 

This is obviously a complicated case, particularly because of the employee's extensive history of low back injuries, symptoms, and treatment, and the record might well have supported conclusions other than those drawn by the compensation judge.  However, given the employee's testimony, the judge was entitled to conclude that the employee did experience an exacerbation of symptoms after the cart he was driving hit a pothole in the yard at work "on or about September 2, 2002."  See Even v. Kraft, Inc., 445 N.W.2d 831, 42 W.C.D. 220 (Minn. 1989).  The judge was also entitled to conclude, based on the opinion of Dr. Wicklund, that the incident caused or permanently aggravated the employee's L1-2 disc condition and substantially contributed to the employee's disability and need for medical treatment thereafter.  See Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985).  For these reasons, and because, in this particular case, we find no error in the judge's selection of an injury date not specifically pled by the employee, we affirm the judge's decision as to the liability of the employer and Kemper for the benefits at issue.

 

2.  Apportionment of Permanent Partial Disability

 

CNA, the employer's insurer at the time of the employee's 1989 injury, paid the employee benefits for a 22.5% permanent partial disability following the employee's 1992 two-level lumbar fusion surgery, pursuant to Minn. R. 5223.0070, subp. 1D (1989), which provides for a 17.5% rating for a one-level fusion and directs the addition of 5% for each additional vertebral level.  At the hearing before the compensation judge, CNA alleged entitlement to a credit for a portion of those benefits, contending that the employee had either a 9% or a 14% permanent partial disability that preexisted the 1989 injury, making apportionment applicable.  See Minn. Stat. ' 176.101, subd. 4a.^[5]  In her decision, however, the compensation judge rejected CNA's apportionment claim, concluding that the employee had not been functionally disabled, within the meaning of Beck v. Dick & John's Price Rebel, 40 W.C.D. 252 (W.C.C.A. 1987), prior to his 1989 work injury.  On appeal, CNA contends that the judge's decision to this effect is clearly erroneous and supported by substantial evidence.

 

We have some concerns about the judge's conclusion that the employee had no functional impairment prior to his 1989 work injury.  The employee was, after all, paid for a 9% permanent partial disability following his 1984 injury, his treating chiropractor had advised that he should change jobs so that he could avoid working in a bent-over position, and the employee himself actually asked to change jobs because his welding work in cement drums "irritated" his low back.  Also relevant is the fact that the employee received continued low back treatment for years following the 1984 injury.  On the other hand, the job that the employee moved to after the 1984 injury required some heavy lifting, and the employee lost no time from this job, due to low back symptoms, from 1985 to 1989.  Moreover, as emphasized by the judge, Dr. Peterson indicated in his November 13, 1987, report that the employee had at that time been working "12 hours a day" with "no functional disability related to his low back."  As such, the evidence may be minimally adequate to support the judge's conclusion that the employee was not "functionally disabled," prior to 1989, under relevant case law.  However, regardless of the propriety of the judge's conclusion in this regard, we believe that apportionment for preexisting permanent partial disability is inappropriate on other grounds.

 

As previously indicated, Home paid the employee benefits for 9% whole body impairment, referable to a herniated disc with resolution of objective neurologic findings, following the employee's 1984 injury.  See Minn. R. 5223.0070, subp. 1B(1)(a).  While the physician's report cited by Home in its benefit payment notice does not specify which lumbar disc level the payment related to, it is most probable that it was the L5-S1 disc.  Our conclusion in this regard is supported by the radiologist's reference to the herniation at that level in the conclusion section of his report concerning the 1985 CT scan.  In contrast, the employee's 1992 fusion surgery followed a 1990 laminectomy at L4-5, and the fusion involved lumbar levels L3 through L5, levels above the employee's earlier-diagnosed L5-S1 herniation.  As such, the employee's preexisting L5-S1 herniation and his 1992 fusion surgery logically qualify as separately ratable impairments not subject to apportionment.  See Fleener v. CBM Indus., 564 N.W.2d 215, 56 W.C.D. 495 (Minn. 1997).  Therefore, the fact that the employee had actually received payment for his L5-S1 herniation, from Home, is essentially irrelevant.  To the extent that CNA claims the right to apportionment of a 9% rating relative to the employee's disc bulge at L3-4, no physician of record has indicated that that particular disc level was ratable prior to the 1989 injury.

 

As for CNA's contention, in the alternative, that the employee's stenosis, also noted on the 1985 CT scan, qualified for a 14% rating, pursuant to Minn. R. 5223.0070, subp. C(1), we are similarly unpersuaded.  It is true, as CNA notes, that the operative report from the employee's fusion surgery contains the diagnosis of "congenital stenosis."  However, contrary to CNA's argument, the record does not necessarily establish that the 1992 fusion surgery was performed because of that stenosis.  Rather, in a 1992 report, Dr. John Bayley, one of the employee's treating surgeons, indicated that the fusion surgery was performed "for recurrent [L4-5] disk herniation with spinal [in]stablility following the decompression."  Moreover, CNA has pointed to no opinion evidence indicating that the employee's low back and leg pain prior to the 1989 injury was the result of the stenosis disclosed on the 1985 scan, as opposed to the employee's herniated L5-S1 disc, and stenosis must be symptomatic to qualify for a 14% rating under the applicable permanent partial disability rules.  See Minn. R. 5223.0070, subp. 1C(1).  Also, Dr. Friedland testified that nothing with regard to the findings at L3-4 and L4-5, noted on the 1985 scan, would have qualified for a permanent partial disability rating under the applicable rules.  As such, the record reasonably fails to establish that the employee's preexisting stenosis condition was ratable under the rules.

 

Finally, CNA contends that the equitable apportionment theory set out in Stone v. Lakehead Constructors, 533 N.W.2d 36, 52 W.C.D. 637 (Minn. 1995), should apply to allow an overpayment credit relative to the L3-4 disc bulge disclosed on the 1985 CT scan.  However, this case is not analogous to Stone, in that we see no danger of a windfall or double recovery to the employee if apportionment is denied.  Again, the employee was in all likelihood compensated for an L5-S1 herniation following his 1984 injury and was then subsequently compensated for a two-level fusion, of different lumbar levels, following the 1989 injury and resulting operations.  There is no necessary overlap between the compensated conditions.  Also, we have noted that equitable apportionment under Stone is never mandatory, Rodas v. By Bread Alone, Inc., No. WC04-313 (W.C.C.A. May 23, 2005), and we question whether apportionment under Stone is ever applicable if the employee has no right to compensation for the preexisting disability - - if, for example, the preexisting condition is nonwork-related.

 

Because the compensation judge did not err in denying apportionment for preexisting disability, we affirm her denial of CNA's credit claim.

 

3.  HealthPartners' Intervention Interest

 

In her findings, the compensation judge determined that intervenor HealthPartners had an intervention interest of $4,598.03 for medical treatment provided to the employee.  On appeal, CNA contends that, in actuality, HealthPartners' interest was $6,172.67, and the employee agrees.  That is also the amount specified in opening statements at hearing.  We therefore modify the judge's decision accordingly.