Muzerall v. IBM CV-97-102-B 03/31/99 UNITED STATES DISTRICT COURT FOR THE DISTRICT OF NEW HAMPSHIRE
Kathleen Muzerall
v. Civil No. 97-C-102-B
International Business Machines Corp.; Memorex-Telex; and Honeywell, Inc.,
MEMORANDUM AND ORDER
Kathleen Muzerall claims that she suffered serious hand,
wrist, and arm injuries after using computer keyboards
manufactured by International Business Machines Corporation,
Memorex-Telex, and Honeywell, Inc. She has sued all three
companies claiming that they defectively designed their keyboards
and failed to adeguately warn of the hazards associated with
keyboard use.
Muzerall intends to rely on expert testimony provided by Dr.
Laura Punnett, an epidemiologist and ergonomist, to prove that
uninterrupted keyboard use for prolonged periods and improper
posture while keyboarding can cause the types of injuries from
which she suffers. Defendants have moved to exclude her
testimony on the ground that it is not sufficiently reliable to
satisfy the reguirements of Fed. R. Evid. 702. Anticipating
success on their motion in limine, defendants have also moved for
summary judgment, arguing that Muzerall cannot prove that her injuries were caused by keyboard use. Because I am unpersuaded
by defendants' arguments, I deny their motions.
I.
A. Muzerall's Work and Medical History
Muzerall worked as an accounts payable clerk/administrator
for Polymer Technology from March 1988 until August 1992. At
some point after she started the job at Polymer, the company
purchased an IBM AS/400 mainframe computer and IBM terminals.
Muzerall was responsible for entering data into the new system,
sometimes spending each day typing in batches of 20 invoices
every half-hour.
Muzerall began working at Fireye Technology in August 1993,
again as an accounts payable clerk/administrator. At Fireye,
Muzerall used a Memorex-Telex keyboard manufactured by Honeywell
to access an IBM AS/400 mainframe computer. She spent her entire
day, except for a one-hour lunch break, entering invoice data
into the computer through that keyboard.
In March 1994, Muzerall began experiencing pain, tingling,
and numbness in her hands and wrists. Her physician initially
diagnosed tendinitis.1 After conservative treatment failed to
1 Tendinitis is the inflammation of a tendon, which is a "fibrous cord or band that connects a muscle with its bony attachment or other structure." Stedman's Medical Dictionary alleviate her pain, Muzerall went to an orthopaedic surgeon. Dr.
Steven Brown, who diagnosed both tendinitis and early medial
epicondylitis.2
Dr. Brown performed surgery on Muzerall's left wrist in
August 1994. He performed a second operation on the same wrist
the following October, scraping the ulna bone to prevent its
impact with the lunate bone. Muzerall returned to work part-
time, but was eventually counseled by her doctors to leave her
job altogether.
In April 1995, Dr. Brown performed an arthroscopy and total
synovectomy3 to Muzerall's right wrist. A test of Muzerall's
blood at that time ruled out rheumatoid arthritis as a source of
her pain. Because pain and swelling continued after the
procedures, Muzerall sought the advice of another doctor in May
1995. Dr. Craig Stirrat recommended another ulna-shortening
procedure for the right wrist. Dr. Mark Belsky performed an
1769 (26th ed. 1995).
2 Epicondylitis is the inflamation of an epicondyle, which is a projection from a long bone near the extremity joint. See Stedman's Medical Dictionary 582.
3 A synovectomy is the excision of the synovial membrane of a joint. See Stedman's Medical Dictionary 1746. The synovial membrane is the connective tissue that lines the joint and produces synovial fluid, a lubricant in a joint or tendon sheath. See id. at 665, 1085-86.
-3- osteotomy4 of the left wrist in February 1996 and a fifth surgery
in August to remove hardware left from the previous operation.
Subseguently, Dr. Belsky recommended yet another surgery to
Muzerall's right wrist. At that point, Muzerall sought a second
opinion from Dr. Kenneth O'Neil, who concurred and performed a
tenosynovectomy5 and reconstruction of the tendon sheath in the
right wrist in July 1997.
Muzerall claims that her injuries6 were caused by the
defendants' failure to warn her about the importance of proper
posture while keyboarding, taking freguent breaks, and the
dangers of repetitive computer work.
B. Muzerall's Expert Witness
To succeed with her claim that her injuries were caused by
defendants' failure to warn her of the hazards associated with
keyboard use, Muzerall must first prove "general" causation.
4 An osteotomy is the cutting of bone. See Stedman's Medical Dictionary 1271.
5 A tenosynovectomy is the excision of a tendon sheath. See Stedman's Medical Dictionary 1771.
6 Muzerall suffers from synovitis, tenosynovitis and tendinitis, chondromalacia, ulnar impaction syndrome, and injury to the triangular fibrocartilage complex ("TFCC"). See Tr. at 1:5.13-16; 1:5.25; 1:7.8-10. Synovitis is the inflammation of a synovial membrane, especially of a joint. See Stedman's Medical Dictionary 1746. Tenosynovitis is the inflamation of a tendon and its enveloping sheath. See id. at 1771.
-4- That is, she must prove that defendants' allegedly wrongful
conduct is capable of causing the types of injuries she claims
she sustained.7 Muzerall relies on expert testimony provided by
Dr. Laura Punnett to satisfy her burden of proof on this issue.
Dr. Punnett is an epidemiologist and ergonomist who has
studied computer-related musculoskeletal disorders. She received
both a master's degree and a doctorate from the Harvard School of
Public Health. She conducted post-doctoral research at the
Center for Ergonomics at the University of Michigan and has
provided epidemiological consulting services to a number of
corporations and organizations. She has previously testified in
other trials dealing with claimed injuries similar to those
suffered by Muzerall. See Schneck v. IBM, 1996 WL 885789, *16
(D.N.J.) ("the studies relied upon by Dr. Punnett are of the type
reasonably relied on by experts in the field to render a
conclusion with respect to general causation"); Vice v. Northern
Telecom, Inc., 1996 WL 200281, *9 (E.D. La.) ("the proposed
testimony of Dr. Punnett is sufficiently reliable to be
admissible . . . the shortcomings complained of by NTT go to the
7 Muzerall also plans to rely on testimony from Dr. Punnett and several other experts to prove specific causation - that her injuries were, in fact, caused by defendants' wrongful conduct. This order addresses only Dr. Punnett's testimony on the issue of general causation.
-5- weight to which the testimony is entitled"). If she is permitted
to testify at trial. Dr. Punnett will claim that prolonged,
uninterrupted keyboard use is causally associated with several
conditions of the hand and wrist including tendinitis, synovitis,
tenosynovitis, chondromalacia, ulnar impaction syndrome, and
injury to the triangular fibrocartilage complex ("TFCC"). She
will also assert that the risk of injury is significantly
enhanced if proper posture is not maintained during keyboard use.
Dr. Punnett bases her general causation opinion primarily on
a 1997 peer-reviewed article which she co-authored with Dr. Ulf
Bergguist.8 In the article's executive summary, Punnett and
Bergguist conclude that
Some general conclusions regarding VDU work and musculoskeletal disorders emerge from this review. These conclusions are supported both by studies of guestionnaire-reported symptoms and studies utilizing objective findings from physical examinations or diagnoses. For disorders of the hand and wrist, we found evidence that the use of the VDU [video display unit] or the keyboard was a direct causative agent, mediated primarily through repetitive finger motion and sustained muscle loading across the forearm
8 Dr. Punnett initially formed her opinion that keyboard use can cause injuries of the types claimed by Muzerall after preparing a literature review of approximately 20 epidemiological studies in 1993 for an attorney representing another plaintiff with similar claims. The 1997 article is an outgrowth of the 1993 literature review.
-6- and wrist. The odds for such disorders among VDU users with at least 4 hours of keyboard work per day appear to be about twice that of those with little or no keyboard work.
Although not all specific factors have been adeguately studied, either singly or in combination with each other, there is convincing evidence regarding some. Strong evidence exists for elevated risks of upper extremity disorders with data entry, and similar intensive keying tasks, and for hand and wrist disorders, at least, with hours of keying per day. High work demand and postural stress resulting from poor work station design and layout also increase the risk of upper extremity disorders. Thus, there is - in our opinion - a scientific basis that justifies ergonomic and work organization interventions to improve work situations characterized by these conditions.
Laura Punnett & Ulf Bergguist, Visual Display Unit Work and Upper
Musculoskeletal Disorders, (National Institute for Working Life -
Ergonomic Expert Committee Document No. 1, 1997:16) (hereinafter
"Punnett & Bergguist").
Although Dr. Punnett relied on more than 50 epidemiological
studies in the 1997 article, she focused on three studies in
particular when testifying in this case. She first cited a 1989
National Institute for Occupational Health and Safety ("NIOSH")
study of employees who regularly used video display terminals
("VDTs") while working at the Los Angeles Times. The study's first phase was a cross-sectional9 analysis using the results of
self-administered questionnaires. A person was classified as
suffering from a musculoskeletal disorder of the hand or wrist
("hand/wrist MSD") in this phase of the study if she reported
that
symptoms (pain, numbness, tingling, itching, stiffness, or burning) in the affected period occurred within the preceding year and all of the following apply: 1) No previous accident or sudden injury that was not work-related (such as dislocation, sports injury, fracture, or tendon tear); 2) symptoms began after starting the current job; (3) symptoms lasted for more than one week or occurred at least once a month within the past year; 4) symptoms were reported as "moderate" (the midpoint) or worse on a five-point scale intensity scale [sic]. All those partici pants who were not excluded because of previous injury and not fulfilling the case definition were considered non-cases for the analysis of Phase I.
Defs.' Ex. S5, NIOSH Health Hazard Evaluation Report, Los Angeles
Times at 11 (hereinafter "Los Angeles Times Study"). In Phase
II, the investigators attempted to validate the case definition
of hand/wrist MSD used in Phase I by subjecting a randomly
9 A cross-sectional study is A study that examines the relationship between the diseases (or other health-related characteristics) and other variables of interest as they exist in a defined population at one particular time. A Dictionary of Epidemiology 40 (3rd ed. 1995).
-8- selected subset of the Phase I cases to physical examination and
nerve conduction testing. This group of cases was then compared
with a control group of uninjured workers in a case-control10
study.
The prevalence rate of hand/wrist MSD identified in the
Phase I study was 22 percent. Other potentially relevant Phase I
results to the present case include the fact that "the odds of
having hand/wrist [MSD] symptoms were increased for those
reporting: (1) more time spent typing on computer keyboards; (2)
a greater number of hours on deadline; and (3) less support from
their immediate supervisor." Los Angeles Times Study at 22.
Using the more restricted definition of hand/wrist MSD employed
in the Phase II study, the study's authors reported that "the
ratio of cases defined by positive physical exam finding to those
defined by symptoms alone (about 50%) is similar to that found in
other [MSD] studies conducted in a variety of industries, using
comparable methods." Id. at 2. They also concluded that
10 A case-control study is an observational epidemiologic study of persons with the disease (or other outcome variable) of interest and a suitable control (comparison, reference) group of persons without the disease. A Dictionary of Epidemiology 2 3.
-9- The risk factors associated with the more restrictive hand/wrist case definition were 1) female gender, and 2) percent of time spent typing on the computer keyboard, categorized by 20% increments. Similar variables were also important in the Phase I analysis (gender and number of hours spent typing on the computer keyboard). The other two important variables identified in Phase I (the number of hours spent on deadline and lack of support from an immediate supervisor) were not important risk factors using the more restrictive case definition . . . . This investigation (both Phases I and II) provides additional evidence that increasing time spent typing on computer keyboards is related to the occurrence of [MSDs], particularly for symptoms and physical findings in the hand/wrist area, which confirms findings of a previous NIOSH study at another large newspaper facility.
Id. at 2-3.
The second study cited by Dr. Punnett examined the effect of
VDT use on workers employed by U.S. West Communications (the
"U.S. West Study"). Like the first phase of the Los Angeles
Times Study, the U.S. West Study was cross-sectional in nature.
A person was classified as suffering from a hand/wrist MSD in
this study if she reported symptoms of injury on a self
administered guestionnaire and injury was confirmed through a
positive physical examination.
The prevalence rate for hand/wrist MSD identified in the
U.S. West Study was 12 percent. The only other pertinent
-10- variables tested in the study that yielded statistically
significant associations were a small negative association with
the number of hours spent at a VDT workstation per day,11 and a
positive association with high information processing demands.
In her 1997 article. Dr. Punnett compared the prevalence rate for
hand/wrist MSD identified in the U.S. West Study with other
prevalence data for hand/wrist MSD for individuals who did not
regularly use VDTs or engage in work that involved highly
repetitive manual tasks. According to Dr. Punnett, this
comparison demonstrated a strong positive association between
keyboard use and hand/wrist MSD.12
The third study discussed by Dr. Punnett during her
testimony examined associations between keyboard use and
musculoskeletal injuries among keyboard operators employed by a
large Australian company. See Pl.'s Ex. 3C, Maurice Oxenburgh,
Musculosketal Injuries Occurring in Word Processor Operators,
Readings in RSI (Michael Stevenson ed.. New South Wales Univ.
11 See discussion of this result in infra p.30.
12 Dr. Punnett obtained similar results when she used prevalence data for hand/wrist MSD drawn from the Los Angeles Times Study and other studies of VDT use. See Punnett & Bergguist at 49, Table 5. As defendants did not challenge the reliability of Dr. Punnett's analysis on this point, I need not further discuss this aspect of her analysis.
-11- Press 1987) (hereinafter "Oxenburgh Study"). The Oxenburgh Study
was a case-control study. The case group included 46 keyboard
operators who were identified as suffering from aching and
fatigue of various degrees in the fingers, hand, wrist, or elbow.
The control group consisted of keyboard users who did not report
the relevant symptoms. The study's central findings were that
[k]eyboard workload was the major causative factor of injury. There was a significant difference between the injured and the non injured groups of the total time spent per day at a keyboard. From these findings the majority of the injured group (51%) spent more than 6 hours/day at the keyboard, compared to the non-injured group where only 8 per cent [sic] spent this amount of time at the keyboard.
Sudden increases in workload can also precipitate injury. Forty-three per cent [sic] of the injured group had their workload on the average almost doubled to 5.6 hours keyboard work/day prior to the injury and, of these cases, 55 per cent [sic] had this workload increase within one week prior to the injury.
Oxenburgh Study at 95. Dr. Punnett testified that she subjected
the data obtained by the Oxenburgh Study to a "Mantel's Trend
Test."13 She claimed that this test demonstrated a highly
statistically significant association between the number of hours
13 A Mantel's Trend Test is "a regression test of the odds ratio against a numerical variable representing ordered categories of exposure." A Dictionary of Epidemiology 100.
-12- per day spent at the keyboard and the risk of being diagnosed
with the injuries under study. See Transcript of Motion Hearing
Before the Hon. Paul J. Barbadoro at 1.120 (hereinafter
"Transcript").
Dr. Punnett did not testify concerning the basis for her
opinion that improper posture during keyboard use is causally
associated with hand/wrist MSD. However, she cites several
studies in the 1997 article that she claims support her opinion
on this subject. See Punnett & Bergguist at 50-58.
Defendants challenge Dr. Punnett's proposed testimony
pursuant to Fed. R. Evid. 702, 14 arguing both that the underlying
studies and her method of analysis were faulty, rendering her
opinions unreliable. Anticipating that Dr. Punnett will be
barred from testifying, defendants also seek summary judgment,
alleging that the remaining evidence cannot satisfy Muzerall's
burden of proof on the issue of causation.
14 Fed. R. Evid. 702 states that "If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness gualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise."
-13- II.
Separate standards of review govern defendants' motions in
limine and their motion for summary judgment.
A. The Motion in Limine
When the admissibility of expert testimony is challenged
through a motion in limine. Fed. R. Evid. 104(a) reguires the
court to make a preliminary finding on admissibility. See Fed.
R. Evid. 104(a). The party offering the expert testimony bears
the burden of proving by a preponderance of the evidence that the
proposed testimony meets the reguirements of Rule 702. See Ruiz-
Trouche v. Pepsi Cola of Puerto Rico Bottling Co., 161 F.3d 77,
85 (1st Cir. 1998).
B. The Motion for Summary Judgment
Summary judgment is appropriate "if the pleadings,
depositions, answers to interrogatories, and admissions on file,
together with affidavits, if any, show that there is no genuine
issue as to any material fact and that the moving party is
entitled to judgment as a matter of law." Fed. R. Civ. P. 56(c).
A "genuine" issue is one "that properly can be resolved only by a
finder of fact because [it] may reasonably be resolved in favor
of either party." Anderson v. Liberty Lobby, Inc., 477 U.S. 242,
-14- 250 (1986); accord Garside v. Osco Drug, Inc., 895 F.2d 46, 48
(1st Cir. 1990). A "material issue" is one that "affects the
outcome of the suit . . . Anderson, 477 U.S. at 248. The
burden is upon the moving party to aver the lack of a genuine,
material factual issue, see Finn v. Consolidated Rail Corp., 782
F.2d 13, 15 (1st Cir. 1986), and the court must view the record
in the light most favorable to the non-movant, according the non
movant all beneficial inferences discernable from the evidence.
See Oliver v. Digital Equip. Corp., 846 F.2d 103, 105 (1st Cir.
1988). If a motion for summary judgment is properly supported,
the burden shifts to the non-movant to show that a genuine issue
exists. See Donovan v. Aqnew, 712 F.2d 1509, 1516 (1st Cir.
1983) .
When a motion for summary judgment is premised upon a claim
that the plaintiff's expert testimony is inadmissible, summary
judgment should be granted if the proffered testimony fails to
meet the threshold for admissibility and the remaining evidence
in the record is insufficient to prove plaintiff's claim for
relief. See Cortes-Irizarrv v. Corporacion Insular De Seauros,
111 F .3d 184, 188 (1st Cir. 1997).
-15- III.
A.________Rule 702 and Reliability Standards for __________ Epidemiological Evidence
To satisfy the admissibility threshold of Fed. R. Evid.
702, expert testimony must meet three requirements. See United
States v. Shav, 57 F.3d 126, 132 (1st Cir. 1995); Grimes v.
Hoffmann-LaRoche, Inc., 907 F. Supp. 33, 34 (D.N.H. 1995); see
also Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579,
589-91 (1993). The expert must be qualified, the expert's
testimony must be reliable, and the testimony must fit the facts
of the case. See Shav, 57 F.3d at 132; Grimes, 907 F. Supp. at
34. When scientific testimony is in dispute. Rule 702's
reliability requirement demands that the expert's opinions must
be qrounded on the "'methods and procedures of science' rather
than on subjective belief or 'unsupported speculation.'" In re
Paoli RR Yard PCB Litigation, 35 F.3d 717, 742 (3d Cir. 1994)
(quotinq Daubert, 509 U.S. at 591). The Supreme Court has
identified several criteria that may be relevant in evaluatinq
the reliability of scientific testimony. These include:
(1) whether the opinion can be or has been tested; (2) whether the theory or technique on which the opinion is based has been subjected to peer review and publication; (3) the technique's known or potential error rate; (4) the existence and maintenance of standards controllinq the technique's operations; and (5) qeneral acceptance.
-16- Grimes, 907 F. Supp. at 35 (citing Daubert, 509 U.S. at 591-95).
In its most recent opinion addressing the issue, the Court
emphasized that these criteria are to be applied flexibly and
that other factors may also be relevant depending upon the nature
of the witness's claimed expertise. See Kumho v. Carmichael,
1999 WL 152455 *9, ___ S. C t . ___ (1999).
Dr. Punnett's testimony in this case is based primarily on
her expertise in the field of epidemiology. An epidemiologist
develops opinions about the causes of disease through a two-step
process. First, she examines population groups to determine
whether an association exists between a suspected cause of the
disease and known patterns of disease distribution. See
generally B. McMahon & D. Trichopoulos, Epidemiology Principles
and Methods (2d ed. 1996); Reference Guide on Epidemiology,
(Federal Judicial Center 1994) at 125-26 (hereinafter "Reference
Guide"). Several guestions should be considered when evaluating
the trustworthiness of an epidemiologist's conclusion that an
association exists between disease and a suspected causal agent.
These guestions include:
(1) Was the research design appropriate for answering the research guestion?; (2) Were the study populations well defined and samples adeguately selected so as to allow for meaningful comparisons (between study groups or between time periods)?;
-17- (3) Was exposure to the putative agent measured using a standardized and reliable methodology?; and (4) Were the health effects (i.e., disease, disability) clearly defined and reliably measured?
Reference Guide at 131.
Once an association has been identified, an epidemiologist
will review the relevant evidence in light of certain generally
recognized criteria to determine whether an inference of
causation is warranted. See McMahon & Trichopoulos at 22-23. One
such set of criteria, known as "Koch's postulates," lists the
following factors as relevant to the analysis:
(1) strength of the association; (2) temporal relationship; (3) consistency of the association; (4) biologic plausibility; (5) consideration of alternative explanations; (6) specificity of the association; and (7) dose- response relationship.
Reference Guide at 161.15
I evaluate the reliability of Dr. Punnett's testimony on
general causation in light of the factors identified by the
Supreme Court in Daubert as well as the above-identified criteria
15 Although Koch's postulates were intended to be used in identifying causes of infectious diseases, see Reference Guide at 163 n.119, and the use of certain of the criteria in other contexts may not be appropriate, see McMahon & Trichopoulos at 23-24, most of the criteria are applicable in this case and are helpful in evaluating the trustworthiness of Dr. Punnett's testimony.
-18- that bear specifically on the reliability of epidemiological
evidence.
B. Application
Muzerall argues that Dr. Punnett's testimony satisfies the
reguirements of Fed. R. Evid. 702 because her opinion on general
causation has been vetted in a peer-reviewed article, it is based
on several reliable epidemiological studies, and, applying
accepted criteria used by epidemiologists, the evidence of an
association between keyboard use and injury demonstrated by these
studies is sufficiently compelling to warrant an inference of
causation. Defendants challenge this argument for several
reasons. Most significantly, they claim that: (1) the studies
that Dr. Punnett relies on to support her conclusion contain
serious methodological flaws; (2) any evidence of an association
between keyboard use and injury suggested by the studies she
cites is not sufficiently compelling to justify an inference that
keyboard use causes injury; and (3) the evidence she relies on
will not reasonably support a conclusion that the specific
conditions from which Muzerall suffers can be caused by
defendants' alleged failure to properly warn of the hazards
associated with keyboard use. I address each of these arguments
in turn.
-19- 1. Methodological Criticisms
Defendants have mounted a multifaceted challenge to the
three studies Dr. Punnett most prominently relies on in
concluding that an association exists between prolonged,
uninterrupted keyboard use and hand/wrist MSD. They argue that:
(1) the studies are subject to "selection bias"16 because they
focus on workplaces with a perceived problem of injuries among
keyboard users; (2) the studies are subject to "recall bias"17
because they depend upon historical information concerning
exposures obtained from participants; (3) the studies use an
overly broad and largely subjective definition of injury; (4)
injury is defined in some of the studies through self-report of
symptoms rather than objective evidence of injury; (5) the
studies measured the prevalence18 rather than the incidence19 of
16 Selection bias is "[e]rror due to systematic differences in characteristics between those who are selected for study and those who are not." A Dictionary of Epidemiology 153.
17 Recall bias is "[s]ystematic error due to differences in accuracy or completeness of recall to memory of past events or experiences." A Dictionary of Epidemiology 141.
18 Prevalence is "[t]he number of events, e.g., instances of a given disease or other condition in a given population at a designated time . . . ." A Dictionary of Epidemiology 12 9.
19 Incidence is "[t]he number of instances of illness commencing, or of persons falling ill, during a given period of time in a specified population." A Dictionary of Epidemiology
-20- injury and (6) because the studies examined so many variables,
there is a substantial risk that any positive associations
reported in the studies for a select few variables was due to
chance.
The short answer to defendants' methodological critique is
that while the concerns they raise are legitimate, they represent
the kinds of criticisms that affect the weight that should be
given to Dr. Punnett's testimony by the jury rather than its
admissibility. It is undisputed that the studies at issue were
carefully constructed and conducted by qualified experts. Many
of the studies note and attempt to account for the limitations
cited by the defendants. Moreover, Dr. Punnett has offered
reasonable, if not necessarily dispositive, answers to each of
defendants' contentions. Generally speaking, when the debate
involves a reasonable disagreement among qualified experts with
the way in which accepted methodologies were used in a particular
case, the choice among competing views is best left to the jury.
Such is the case here.
82. When studying causal factors of disease, epidemiologists generally agree that incidence measured as soon as practicable after onset is the most useful measure of disease frequency. See MacMahon & Trichopoulos at 62.
-21- 2. Causation
Defendants also argue that the evidence of an association
between keyboard use and injury identified in the studies Dr.
Punnett cites does not support her conclusion that hand/wrist MSD
can be caused by prolonged, uninterrupted keyboard use and
improper posture during keyboard use. Applying accepted criteria
used by epidemiologists when investigating the issue of
causation, defendants argue that an inference of causation cannot
be drawn here because: (1) the studies Dr. Punnett relies on
cannot be used to establish an appropriate temporal relationship
between exposure and injury; (2) Dr. Punnett has failed to
sufficiently establish that prolonged keyboard use is a
biologically plausible cause of the types of injuries from which
Muzerall suffers; and (3) any association between keyboard use
and injury demonstrated in the studies is not sufficiently strong
and consistently identified to support an inference of causation,
a. Temporal Relationship
An exposure to something such as keyboard use logically
cannot be a cause of a particular injury unless the exposure
precedes the injury. Accordingly, it is important to attempt to
demonstrate an appropriate temporal relationship between exposure
and injury when drawing an inference of causation. See Reference
-22- Guide at 162 n.113. If the correct temporal sequence cannot be
proved, it is vital that "there must be at least the possibility
that such a sequence exists." MacMahon & Trichopoulos at 23.
Phase I of both the Los Anqeles Times Study and the U.S.
West Study were cross-sectional studies. Because such studies
examine exposure and injury amonq study participants at the same
point in time, they are of limited value in inferrinq a temporal
relationship between the exposure and the injury. See id. at 81-
82. Further, because Phase II of the Los Anqeles Times Study and
the Oxenburqh Study were case-control studies, they necessarily
were dependant upon historical information concerninq the
relationship between exposure and injury, a limitation which also
restricts their usefulness in reliably identifyinq a temporal
relationship between keyboard use and injury. See id. at 79-80.
Defendants invoke these limitations in challenqinq Dr. Punnett's
testimony.
Dr. Punnett readily acknowledqes that the studies she relied
on cannot conclusively demonstrate the appropriate temporal
relationship between keyboard use and injury. Nevertheless, she
defends her conclusion with two arquments. First, she notes that
two of the three studies at issue - the Los Anqeles Times Study
and U.S. West Study - eliminated persons who reported the onset
-23- of symptoms before they became employed. She then stated that
this fact makes it unlikely that anyone in the groups being
studied developed hand/wrist MSD before they began to regularly
use keyboards. Second, she argues that it is unlikely that many
of the keyboard users who suffered from hand/wrist MSD had the
condition before they began to regularly use keyboards because it
is reasonable to presume that persons with hand/wrist MSD are
unlikely to move in large numbers to jobs that reguire extensive
keyboard use. While other experts reasonably could be left
unpersuaded by these arguments, they are not the type of
manifestly meritless assertions that must be rejected before they
can even be presented to the trier of fact.
b. Biological Plausibility
Defendants next argue that Dr. Punnett has failed to
demonstrate that it is biologically reasonable to infer that
prolonged, uninterrupted keyboard use or poor posture can cause
the types of injuries from which Muzerall suffers. To support
their assertion, defendants argue that the studies cited by Dr.
Punnett on this issue all involved much greater levels of force
than occurs during keyboard use. Defendants have also have
produced expert testimony suggesting various reasons why it is
biologically implausible to infer that such a causal relationship
-24- exists. Muzerall responds by citing testimony from Dr. Punnett,
who claims that there is "a large body of evidence" to support
the biologic plausibility of her opinion on general causation.
See Tr. at II.5.23-6.16. In particular, she testified:
Well, there's a paper by Armstrong and Chaffin, for example, which shows that the - I'm sorry, yes-- which shows that the speed with which the fingers move, the length of the work period before resting, and the length of the rest period relative to the work period all predict the loading on the tendons. That is, the actual mechanical stretching of the tendon tissues as a function of being pulled on by the contracting muscle. Other work by Armstrong with a Dr. Steven Goldstein has gone further into this examining the cumulative tendon strain, the cell damage and loss of normal function of the tendon. THE COURT: So prolonged loading of the tendon has been demonstrated to produce injury to the tendon, and the sheath consistent with tendinitis, tenosynovitis and synovitis. Is that what you're saying the study showed? THE WITNESS: Yes, your Honor. I would say repetitive motion and prolonged periods of repetitive motion, yes. THE COURT: So loading the tendon in the same way repeatedly over a significant period of time is what has biologically been show[n] to produce the kind of injury that we're talking about. THE WITNESS: Correct. There's at least one other paper that I can think of right now which shows further that if the fingers are moving with the wrist bent, either flexed or extended, because of the biomechanical disadvantage of this posture the load on the tendons is even greater and the probability
-25- of these kinds of tissue damages is even greater.20
Tr. at II.17.18-19.1. This testimony is sufficiently persuasive
to support Dr. Punnett's testimony that a biologically reasonable
explanation exists for the inference of a causal relationship
between prolonged, uninterrupted keyboard use or poor posture and
hand/wrist MSD.
c. Strength and Consistency of Association
Defendants also contend that any association between
exposure and keyboard use demonstrated by the studies Dr. Punnett
relies on is not sufficiently strong and consistently
demonstrated to support an inference of causation. In making
this argument, defendants they rely heavily on the negative
association between the number of hours spent at a VDT
workstation per day and hand/wrist MSD reported by the U.S. West
20 Dr. Punnett did not identify the specific works she was referring to in her testimony. However, in supporting similar assertions in the 1997 article she cites to a number of papers. See Punnett & Bergguist at 6-7 (citing Armstrong, Buckle & Fine, et al., A Conceptual Model for Work-Related Neck and Upper Limb Musculoskeletal Disorders, Scand. J. Work Environ. Health 1993, 19:73-84; Armstrong, Fine & Goldstein, et al.. Ergonomic Considerations in Hand and Wrist Tendinitis, J. Hand Surg. 1987, 12A:830-837; Chaffin & Andersson, Occupational Biomechanics (2d ed.) New York, NY: Wiley & Sons (1991); and Goldstein, Armstrong & Chaffin, et al.. Analysis of Cumulative Strain in Tendons and Tendon Sheaths, J. Biomech. 1987, 20:1-6).
-26- It is undisputed that the three studies Dr. Punnett most
prominently relies on have sufficient power21 to reliably
identify the existence of an association between prolonged,
uninterrupted keyboard use and hand/wrist MSD. Dr. Punnett has
also offered a plausible argument that the association between
keyboard use and injury demonstrated by these studies is likely
to be understated because of a phenomenon known as the "healthy
worker effect."22 Further, rather than relying on only one study
to support her opinion. Dr. Punnett identifies numerous other
studies that also report statistically significant associations
between keyboard use and injury. Finally, she plausibly explains
the negative association identified in the U.S. West Study by
stating that since the subjects included in the study all spent
at least six hours per day typing, the only conclusion that the
negative association supports is that typing more than six hours
21 Power is "the ability of a study to determine an association if one exists." A Dictionary of Epidemiology 128.
22 The "healthy worker effect" is a phenomenon in which workers may exhibit lower overall rates of injury than the general population "because the severely ill and chronically disabled are ordinarily excluded from employment." A Dictionary of Epidemiology 75. In the context of this case. Dr. Punnett theorizes that the healthy worker effect will cause the association between keyboard use and injury in studies of active workers to be understated because some of the injured workers will remove themselves from the work force and hence will not be identified.
-27- per day does not increase the risk of injury. Accordingly, she
argues that this finding is not necessarily inconsistent with the
positive associations reported in other studies. Her testimony
on this issue sufficiently supports her claim of a strong and
consistent association between keyboard use and injury to
overcome defendants' objections on this point.
In summary, while the existence of a causal relationship
between prolonged, uninterrupted keyboard use or poor posture and
hand/wrist MSD remains controversial. Dr. Punnett's opinion on
general causation is reasonably based on the methods and
procedures generally employed by practitioners in the field of
epidemiology. Accordingly, her disagreements with defendants'
expert represent the type of conflict that ordinarily should be
resolved by a jury.
3. Definition of Hand/Wrist MSD and its Relationship to Muzerall's Medical Conditions
Perhaps defendants' most troubling argument is their claim
that even if prolonged, uninterrupted keyboard use and poor
posture are causally associated with the cluster of medical
conditions that Dr. Punnett calls hand/wrist MSDs, the evidence
will not support her more specific conclusion that such keyboard
use is causally associated with the specific conditions from
-28- which Muzerall suffers. In essence, defendants' argument is that
because the studies relied on by Dr. Punnett defined the term
"hand/wrist MSD" broadly to include a large group of symptoms,
syndromes, and specific medical conditions from which Muzerall
does not suffer, it is impossible to tell whether any
demonstrated association between keyboard use and the entire
group of problems defined as hand/wrist MSD also reflects a
comparably strong association between keyboard use and the
specific medical conditions at issue in this case.
Dr. Punnett acknowledges this problem, but minimizes its
significance. She testified that tendinitis, the primary
condition from which Muzerall suffers, represents a large subset
of the medical conditions collectively comprising hand/wrist MSD.
She also claims that "the pattern of tendinitis tracks the
patterns for [the] other disorders" included within the
definition of hand/wrist MSD. See Tr. at 11.162-63.
Accordingly, she concludes that it is unlikely that the possible
association demonstrated between keyboard use and hand/wrist MSD
does not also accurately describe the association between
keyboard use and the kind of tendinitis from which Muzerall
suffers. Once again, I find this argument sufficiently
-29- persuasive to allow Muzerall to present Dr. Punnett's testimony
on this point to a jury.
IV. CONCLUSION
Dr. Punnett's opinions on the causal relationship between
keyboard use and the disorders from which Muzerall suffers remain
controversial. While reasonable experts could disagree with her
conclusions and challenge the rigor with which they have been
supported, I am satisfied that Dr. Punnett has based her opinions
on methods that are sufficiently reliable to permit her to
express those opinions to a jury. Her central conclusions that
prolonged, uninterrupted keyboard use and improper posture while
using a keyboard are causally associated with hand/wrist MSD have
been subjected to peer review and publication. The studies she
relies on to support her opinions are methodologically sound and
the criteria she used in forming those opinions are generally
accepted as appropriate by epidemiologists. Accordingly, I
conclude that Muzerall has satisfied Rule 702's reliability
reguirement.
Defendants have also argued that Dr. Punnett's opinion on
general causation is barred by Rule 702 because it does not "fit"
the facts of the case. "The concept of fit reguires that a valid
-30- connection exist between the expert's testimony and a disputed
issue." Shay, 57 F.3d at 133. Defendants argue that Dr.
Punnett's testimony does not fit the facts of the case because
Muzerall has not demonstrated that her history of keyboard use
involved the type of prolonged, uninterrupted use and poor
posture that Dr. Punnett claims is causally associated with
injury. They also contend that Dr. Punnett's general causation
opinion does not address certain specific conditions that
Muzerall suffers from such as the TFCC. The current record is
not sufficiently developed to permit me to rule on these
arguments now. Accordingly, I deny defendants' motion in limine
without prejudice as to these issues and will resolve them later
if they are raised again at trial.23
Defendants' motion in limine and for summary judgment
(document no. 36) is denied.
23 Defendants also invoked Fed. R. Evid. 403 but presented no specific argument based on this rule. Since they did not develop their argument, I have not attempted to address it in this order. Further, although defendants have challenged the admissibility of Muzerall's expert testimony on the issue of specific causation, the record is not sufficiently developed to permit me to rule on their contentions. Accordingly, I also deny their motion without prejudice as to these arguments.
-31- SO ORDERED.
Paul Barbadoro Chief Judge
March 31, 1999
cc: David P. Slawsky, Esq. James M. Campbell, Esq. Michael A. Cerussi, Jr., Esq. Ronald D. Ciotti, Esq. Peter S. Cowan, Esq. Thomas M. DeSimone, Esq. Bert L. Wolfe, Esq.
-32-