In Re: Zimmer Nexgen Knee Implant Products Liability Litigation
MEMORANDUM Opinion and Order: Plaintiff's motion to exclude testimony by Dr. Stuart Goodman #1333 regarding the alignment of Ms. Batty's implant is granted. Plaintiff's motion to exclude the testimony of Dr. Timothy Wright #1405 is granted with respect to his "retrieval study" and denied with respect to his analysis of the clinical literature documenting patient outcomes with the NexGen Flex. Signed by the Honorable Rebecca R. Pallmeyer on 8/27/2015. Mailed notice. (etv, )
UNITED STATES DISTRICT COURT
FOR THE NORTHERN DISTRICT OF ILLINOIS
IN RE: ZIMMER NEXGEN KNEE
IMPLANT PRODUCTS LIABILITY
KATHY L. BATTY,
ZIMMER, INC., ZIMMER HOLDINGS,
INC., and ZIMMER ORTHOPAEDIC
SURGICAL PRODUCTS, INC.,
MDL No. 2272
Master Docket No. 11 C 5468
No. 12 C 6279
Judge Rebecca R. Pallmeyer
MEMORANDUM OPINION AND ORDER
Kathy Batty is one of hundreds of Plaintiffs who have sued Defendants, Zimmer, Inc. and
its affiliates (collectively, "Defendant" or "Zimmer"), manufacturers of the Zimmer NexGen Flex
Knee system. Plaintiffs, who have had the NexGen Flex system implanted, allege that the
femoral and tibial components of the system are prone to premature loosening, resulting in pain,
loss of movement, and in some cases requiring revision surgery. Ms. Batty's case has been
chosen for a "bellwether" trial. Both parties have identified several expert witnesses. In earlier
rulings , , and , the court considered challenges to Ms. Batty's experts Dr.
Brown, Dr. Fetto, and Dr. Klein, as well as Plaintiff's challenges to Zimmer's experts, Dr. Darryl
D'Lima and Michael Vitale. In this opinion, the court addresses Plaintiff's objections to expert
testimony from two more of Zimmer's proposed experts, Dr. Stuart Goodman  and Dr.
Timothy Wright . For the reasons set forth below, Plaintiff's objections to Dr. Goodman
are sustained, and her objections to Dr. Wright are sustained in part and overruled in part.
Plaintiff Kathy Batty suffers from degenerative joint disease in both knees. In April 2009,
her treating physician, Dr. Alan Klein, performed total knee replacements on both of Ms. Batty's
knees, implanting a NexGen LPS-Flex Gender Solutions femoral component (the “NexGen
Flex” or "Flex") and a NexGen Stemmed Tibial Component Option in each of Ms. Batty’s knees.
These components, the model at issue in these lawsuits, are designed to enhance the patient’s
flexion capacity to 155 degrees, significantly more than earlier implants, including Zimmer’s own
knee implant model (the “NexGen Standard”). The knee implant replaces the top part of the
shin bone (the tibia) and the bottom part of the thigh bone (the femur). The tibial component of
a knee implant consists of a metal tray that sits on top of the tibia and a stem that extends
downward into the tibia.
Seated on top of the flat metal tray of the tibial component is a
polyethylene surface that serves as the point of contact for the femoral component, also referred
to as the "poly," "articulating surface," or the "articular surface."
The femoral component
attaches to the bottom of the femur:
The court has described the facts of the case in detail in its earlier opinions, see
In re Zimmer NexGen Knee Implant Products Liab. Litig., No. 11-CV-5468, 2015 WL 3669933
(N.D. Ill. June 12, 2015); In re Zimmer NexGen Knee Implant Products Liab. Litig., No. 11-CV5468, 2015 WL 3799534 (N.D. Ill. June 17, 2015); In re Zimmer NexGen Knee Implant Products
Liab. Litig., No. 11-CV-5468, 2015 WL 4880953 (N.D. Ill. Aug. 13, 2015), and provides only a
brief overview here.
(Expert Report of Dr. Stuart Goodman, Ex. O to Pl.'s Goodman Mem. [1335-15], hereinafter
"Goodman Rep.," 3.)
Just over a year after her surgeries, in July 2010, Ms. Batty began to experience pain in
both knees. She had her implants replaced in April and May of 2011. In this litigation, Ms. Batty
alleges that the Flex design caused her implants to prematurely loosen from her bones by
increasing the forces and strain on the implant. One of Ms. Batty's specific theories of defect is
that the design puts excessive strain on the back ("posterior") edge of the tibial component, a
phenomenon called "posterior edge loading."
Plaintiff's expert Dr. Brown opined that the Flex
design decreases the contact area between the femoral and tibial component at certain angles
of flexion. (Expert Report of Thomas Brown, Ex. B to Zimmer's Mot. to Exclude Testimony of
Dr. Brown [1302-2], hereinafter "Brown Rep.," 45–46.)
A more limited contact area
concentrates the forces passing through the knee in a smaller spot on the tibial component,
increasing the pressure experienced by the component at that location.
contends that with the Flex design, those concentrated forces are also located toward the
posterior edge of the tibial tray, rather than in the center, resulting in posterior edge loading.
Posterior edge loading, Dr. Brown continues, causes a corresponding upward force on the front
("anterior") of the tibial component. (Id. at 47–48.) That upwards anterior force, according to
Plaintiff, causes the tibial component to pull away from the bone at microscopic levels. (Id. at
48.) Repeated posterior edge loading can, therefore, cause the tibial component to rock or
toggle, and eventually loosen from the tibial bone. (Id.)
Zimmer retained Dr. Timothy Wright, a biomechanical engineer, and Dr. Stuart
Goodman, an orthopedic surgeon and Ph.D. in medical science, to opine on the biomechanical
principles underlying the design of the NexGen Flex, to respond to Plaintiff's theories of defect,
and to opine on the specific reasons that Ms. Batty's implants failed.
Dr. Wright opines that the NexGen Flex design was not defective, but rather was an
"evolutionary change to the clinically successful" NexGen Standard design. The NexGen Flex
enabled flexion beyond 130 degrees and "actually mitigated the risks" of aseptic loosening
compared to the Standard, he asserts, because the Flex design increases the contact area
between the femoral and tibial components, distributing the forces more evenly. (Expert Report
of Timothy Wright, Ex. A to Pl.'s Wright Mem. [1407-1], hereinafter "Wright Rep.," 3.) According
to Dr. Wright, Plaintiff's theories of defect "lack a credible scientific basis." He specifically rebuts
Plaintiff's theory of posterior edge loading, concluding that such loading is "rare" and is unlikely
to contribute to implant failure. 2 (Id. at 3, 22, 25.) Finally, he offers an alternative cause for Ms.
Batty's implant failure, asserting that it was not the result of the design of the Flex implant, but
was due to the misalignment of her tibial component in relation to her tibia, uneven cementing of
the tibial components, Ms. Batty's active lifestyle, and a possible low grade infection. (Id. at
Dr. Goodman similarly analyzes the design rationale for the NexGen Flex and concludes
that it is supported by relevant scientific principles. He opines that the success of the Flex
design has been borne out in the clinical evidence. (Goodman Rep. at 6–11, 24.) He also
reviewed Ms. Batty's medical records and, like Dr. Wright, believes that Ms. Batty's implant
failure was caused by poor cementing technique, the misalignment of the components, Ms.
Batty's activity level, and a possible low-grade infection. (Goodman Rep. at 19–20.) Finally, in
Dr. Goodman's view, the written disclosures and instructions for surgeons adequately warn
about the risks of aspetic loosening and revision. (Goodman Rep. at 11–12.)
Plaintiff urges the court to exclude portions of Dr. Goodman's and Dr. Wright's testimony
as unreliable under Federal Rule of Evidence 702 and Daubert v. Merrell Dow Pharm., Inc., 509
Dr. Wright rebuts several of Plaintiff's other theories of defect, including: (1) the
additional two millimeter bone cut required with the Flex; (2) the limited axial rotation available in
the Flex; (3) the increased likelihood of condylar lift-off; and (4) the increased risk of
radiolucencies behind the flanges of the femoral component. (Wright Rep. at 21.) Plaintiff
does not challenge Dr. Wright's opinions on these topics, and the court, therefore, has not
summarized those sections of Dr. Wright's report.
U.S. 579 (1993). 3 Though Drs. Wright and Goodman cover a wide range of topics in their
reports, Plaintiff's challenges to their testimony are narrow. Plaintiff urges the court to exclude
two of Dr. Wright's conclusions as based on unreliable methodologies: (1) his opinion that the
NexGen Flex has had "excellent clinical success," as demonstrated by the relevant clinical data,
and (2) that posterior edge loading is "rare" with the NexGen Flex design. With respect to Dr.
Goodman, Plaintiff challenges only his opinions regarding the alignment of Ms. Batty's implant.
The court addresses each challenge in turn.
Dr. Timothy Wright is a biomechanical engineer who has 35 years of experience
designing, testing, and analyzing orthopedic implants. (Wright Rep. at 1.) He received his
Bachelor of Science degree from Lehigh University in 1971. (Id.) Between 1972 and 1976, he
completed a Masters degree and Ph.D. in Materials Science at Stanford University. (Id. at 1,
A.3.1.) During his graduate education, he worked in the Biomechanics Laboratory, Department
of Applied Mechanics at Stanford, focusing his research on orthopedic biomechanics. (Id. at 1.)
After completing his Ph.D., he joined the Hospital for Special Surgery ("HSS") in New York as a
Research Fellow in the Department of Biomechanics, and has been working at HSS
continuously since then, rising to the position of Director of the Department of Biomechanics,
which he has held since 1992. (Id. at 1.)
Dr. Wright opines that the NexGen Flex "design does not have a greater propensity for
aseptic femoral or tibial component loosening than the NexGen standard design, and both
designs have repeatedly demonstrated excellent clinical performance . . . as evidenced by
dozens of clinical studies and the outcomes reported by national joint registries." (Wright Rep.
The court assumes familiarity with the Daubert standards set forth in its earlier
opinion, see In re Zimmer NexGen Knee Implant Products Liab. Litig., No. 11–CV–5468, 2015
WL 3669933, at *6–7 (N.D. Ill. June 12, 2015), and declines to repeat them here.
at 3.) Dr. Wright acknowledged that two studies cited by Plaintiff's expert Dr. Brown— H.S Han
et al., High Incidence of Loosening of the Femoral Component in Legacy Posterior StabilizedFlex Total Knee Replacement, 89-B J. BONE JOINT SURG. 1457, 1461 (2007) and Cho et al.,
Three- to Six-Year Follow-up Results After High-Flexion Total Knee Arthroplasty: Can We Allow
Passive Deep Knee Bending?, 19 KNEE SURG. SPORTS TRAUMATOLOGY ARTHROSCOPY 899, 903
(2011)—suggest that the Flex designs have an increased risk of aseptic loosening. Dr. Wright
dismissed those studies, however, because they "are overwhelmed by the far larger group of
studies showing excellent results, including a lack of aseptic loosening, with the Flex design."
(Wright Rep. at 20.) Dr. Wright reviews six studies and data from the Australian Orthopaedic
Association's National Joint Registry, 4 and opines that, if the design were defective, consistent
failure of the device would manifest in the clinical evidence. But according to Dr. Wright, the
data from the studies and the Australian Registry shows that "the NexGen Flex design has
achieved excellent clinical results that reinforce my opinions that the components are welldesigned from a biomechanical and engineering standpoint."
(Wright Rep. at 21.)
Plaintiff contends that Dr. Wright's analysis of the clinical literature is unreliable because
he did not perform a comprehensive literature review and instead "cherry picked" relevant
studies to support his conclusion. (Pl.'s Mem. in Supp. of Mot. to Exclude Testimony of Timothy
Wright , hereinafter "Pl.'s Wright Mem.," 2, 23.)
Dr. Wright does not claim to have
performed a comprehensive literature review, however, and the fact that he did not follow the
standard methodology for such a review is not fatal to his testimony. Plaintiff has not argued
that Dr. Wright misinterpreted the studies he did cite, and the court believes that the data Dr.
Wright reviewed will provide important context for the jury in deciding whether the design is
The Australian Orthopaedic Association's National Joint Registry is a patient
registry that collects uniform data on all joint replacement surgeries from every hospital in
Australia performing such surgeries. The data is used to evaluate patient outcomes based on
"patient characteristics, prosthesis type and features, method of prosthesis fixation and surgical
technique." See About, AUSTRALIAN ORTHOPAEDIC ASSOCIATION NATIONAL JOINT REPLACEMENT
REGISTRY, https://aoanjrr.dmac.adelaide.edu.au/en/background (last visited Aug. 20, 2015).
defective. Each party has offered expert testimony to explain and interpret the various studies
and data applicable to this litigation. If Dr. Wright failed to consider relevant data, Plaintiff may
highlight that failure at trial. In short, Plaintiff has identified no reason that her criticisms of Dr.
Wright's analysis cannot be raised through vigorous cross-examination or with competing expert
evidence and his testimony is sufficiently reliable to survive Daubert scrutiny.
The court cautions, however, that though adequately reliable, Dr. Wright's testimony
pertaining to the clinical evidence and registry data runs the risk of "needlessly presenting
cumulative evidence." FED. R. OF EVID. 403. Zimmer has now proposed three different experts
to testify about the relevant clinical literature and evidence: Dr. Wright, Dr. Goodman, and Dr.
Each one of those experts discusses a similar set of studies as well as the data
contained in the Australian registry.
The court sees no additional probative value from
presenting this evidence through three different expert witnesses and will exclude redundant
and cumulative evidence at trial.
Posterior Edge Loading
Dr. Wright also responds to Dr. Brown's theory of defect based on posterior edge
loading. According to Dr. Wright, Zimmer's design actually mitigates the risk of posterior edge
loading by providing larger contact areas between the femoral and tibial components,
distributing forces more evenly across the tibial component. (Wright Rep. at 23.) Dr. Wright
cites three pieces of evidence in support of his conclusion:
(1) Zimmer's contact area
measurements taken during the design of the Flex system, (2) a computer model simulation
conducted by Dr. D'Lima, and (3) a "retrieval analysis of NexGen articular surfaces used with
the Flex femoral components." (Wright Rep. at 23–24.)
In this motion, Plaintiffs challenge the reliability of Dr. Wright's retrieval study. 5
Wright described his methodology as follows:
Plaintiff separately challenged Dr. D'Lima's computer model, an objection the
court has overruled, In re Zimmer NexGen Knee Implant Products Liab. Litig., No. 11-CV-5468,
As part of an ongoing examination of high flex designs, retrieved tibial inserts
used with Zimmer Flex femoral components have been gathered from revision
surgeries as part of our ongoing Implant Retrieval Program at Hospital for
Special Surgery. We have used laser scanning of the components along with
scans from the pristine, never implanted Zimmer components of the same design
and size. By aligning the scans, we compared how deformed the retrieved
components were in relation to the pristine components. In eight retrieved
specimens, we found little deformation on the bearing surfaces, consistent with
reasonable levels of contact stress, even at the posterior edges, the location
where the Plaintiffs contend high contact stresses would be consistent with
extreme deformation and wear of the polyethylene.
(Wright Rep. at 24.)
Immediately following this explanation, Dr. Wright included eight
"colormetric maps of deformation" in the polyethylene surface:
(Id. at 25.) The caption states that "[t]he colors denote deformational differences with pristine,
never implanted components." (Id.) But Dr. Wright included no scale to define what the various
colors mean (which color is neutral, which is raised, and which is depressed?) or how much
2015 WL 4880953, at *7 (N.D. Ill. Aug. 13, 2015), and assert that they will challenge Zimmer's
contact area measurements "on the facts." (Pl.'s Wright Mem. at 6–7.)
deviation from the un-implanted scans each color represents (what fraction of a millimeter?).
Dr. Wright's report continues, stating only that "these findings suggest that posterior edge
loading is a rare event and that the loads experienced by Zimmer Flex components are
insufficient in magnitude to cause significant polyethylene damage to contribute to implant
failure," without further explanation.
(Wright Rep. at 25.)
Dr. Wright has not sufficiently
presented his underlying data or explained how he reasoned from that data to his conclusions.
The court, acting as a gatekeeper, must exclude "opinion evidence that is connected to existing
data only by the ipse dixit of the expert.” Gen. Elec. v. Joiner, 522 U.S. 136, 146 (1997).
After his initial report, Dr. Wright supplemented his retrieval study with twelve additional
scans, conducted after he had submitted his report but before his deposition. (Retrieval Study
Supplement, Ex. C to Pl.'s Wright Mem. [1470-3], hereinafter "Retrieval Supp.") This time, the
scans included color scales defining the amount of deviation from a never-implanted
component. Even in this supplemental report, however, Dr. Wright did not provide the color
scales for the first eight scans. Moreover, one of the supplemental twelve scans is presented
with a different scale than the remaining eleven: While the scales accompanying the first eleven
scans range from -1.5 millimeters to 1.5 millimeters, the scan labeled "Study 19" 6 ranges from 2.9289 millimeters to 2.9289 millimeters.
Dr. Wright has not acknowledged or explained his
use of a different color scale for this particular scan. In light of Dr. Wright's apparent use of
different scales without explanation in the supplemental scans, the court has concerns that the
initial eight scans may also rely on different scales and are, thus, not directly comparable to one
another. Without more clarity regarding the color scales, Dr. Wright has simply not provided any
basis from which the court can conclude he employed a reliable methodology.
Dr. Wright has provided no explanation for the labels assigned to the various
scans. The scans submitted in the supplemental report are labeled with numbers 1–7, 9, 13,
15, 18, and 19. (See Retrieval Supp. at 5–16.)
Even if the confusion surrounding the color scale were resolved, there are additional
gaps in Dr. Wright's reasoning that support the court's decision to exclude testimony about his
Dr. Wright has not explained the basis for his conclusion that "the loads
experienced by Zimmer Flex components are insufficient in magnitude to cause significant
polyethylene damage to contribute to implant failure." (Wright Rep. at 25.)
Dr. Wright did not
define the threshold he used to distinguish between "significant polyethylene damage" that
contributes to implant failure, and insignificant polyethylene damage that does not. Nor did he
cite any studies that quantify the amount of deformation considered safe. Finally, he did not
compare the deformation observed on NexGen Flex implants to deformation observed on
Zimmer Standard implants.
Nor does the court follow how Dr. Wright determined that "posterior edge loading is a
rare event." (Wright Rep. at 25.) First, Dr. Wright examined only 20 scans, many of which were
used only at low flexion angles (0–90 degrees) or at flexion angles that were not reported at all.
One of the implants in the original report was only implanted for "0.1" years, and one in the
supplemental report was implanted for only "0.36" years, suggesting very little time for wear or
damage to the polyethylene to occur. (Wright Rep. at 25; Retrieval Supp. at 1.) Moreover,
several of the implants scanned were revised for reasons other than aseptic loosening,
undermining any comparison with Ms. Batty and the other plaintiffs in this litigation. (Wright
"malalignment/pain"); Retrieval Supp. at 1 (reasons for revision included "instability," "stiffness,"
"infection," and "arthrofibrosis").) Federal Rule of Evidence 702 requires the court to ensure
that an expert's opinions are based on "sufficient facts or data." FED. R. EVID. 702; Lapsley v.
Xtek, Inc., 689 F.3d 802, 810 (7th Cir. 2012). The court is not satisfied that these 20 scans are
sufficient to support a conclusion that posterior edge loading is "rare" in all NexGen Flex
Second, Dr. Wright has not explained why he believes that the absence of
polyethylene deformity necessarily implies the absence of posterior edge loading on the
underlying tibial tray. He cites no study to support that assertion and provides no data or testing
of his own. He has not addressed the possibility that the polyethylene could simply transfer
stresses to the tibial tray, without wearing down, resulting in posterior edge loading without any
deformation of the polyethylene surface. The court concludes that "there is simply too great an
analytical gap between the data and the opinion proffered."
Joiner, 522 U.S. at 146. Dr.
Wright's testimony relating to his retrieval study is, therefore, excluded.
Dr. Stuart Goodman is an orthopedic surgeon and a Professor of Orthopedic Surgery
and of Bio-engineering at Stanford University.
(Goodman Rep. at 39.)
He received his
Bachelor of Science, Masters of Science, and medical degrees from the University of Toronto.
(Goodman Rep. at 2.) He continued on at University of Toronto for his orthopedic residency,
which he completed in 1984. (Id.) In 1985, he completed fellowships in adult reconstruction
and orthopedic trauma at the Wellesley Hospital and Sunnybrook Medical Center in Toronto.
(Id.) He has been board certified in orthopedic surgery by the American Board of Orthopedic
Surgery since 1987.
In 1994, he obtained a Ph.D. in Medical Science from Lund
University in Sweden. (Id.)
Like Dr. Wright, Dr. Goodman's report is broad in scope. He begins by explaining how a
total knee replacement can be used to treat arthritis and then describes the various
complications that can arise after a total knee replacement.
He notes that surgeons may
improperly align the implant or may use an inadequate or uneven layer of cement to fasten the
implant to the bone. (Goodman Rep. at 3–4.) He also describes the rationale behind the
NexGen Flex femoral component design, concluding, as Dr. Wright did, that the design allows
for greater contact area between the femoral and tibial components, thus reducing the risk of
posterior edge loading. (Goodman Rep. at 6.) Dr. Goodman asserts that "the overwhelming
majority of reported studies have demonstrated the safety and efficacy of the Zimmer NexGen
[Flex] worldwide. This is consistent with the 2013 Australian Arthroplasty Registry data, an
important source for determination of clinical outcome for surgeons." (Goodman Rep. at 11.)
Finally, Dr. Goodman analyzes Ms. Batty's medical records (Goodman Rep. at 12–19), and
opines that the loosening she experienced was caused by her implanting surgeon's poor
cementing technique, the misalignment of the components, Ms. Batty's activity level, and a
possible low-grade infection. (Goodman Rep. at 19–20.)
Plaintiff challenges only one aspect of Dr. Goodman's report: his assertion that Ms.
Batty's knee was misaligned. There are two angles that determine whether a knee implant is
properly aligned: one is the overall alignment of the knee, that is, the relationship between the
femur and the tibia. The overall alignment can be in "varus," that is a bow-legged misalignment,
or in "valgus," which is a knock-kneed misalignment.
(Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System, Ex.
C to Pl.'s Goodman Mem. [1335-3], 7.) 7 The overall angle of the knee is the sum of the α and β
angles. If the sum is less than 180 degrees, the knee is in varus alignment. If the sum is
greater or equal to 180 degrees, the knee is in valgus. Dr. Wright testified that the target for the
overall knee alignment is two to five degrees valgus, or a sum of 182 to 185. (Dep. of Timothy
Wright, Ex. B. to Pl.'s Goodman Mem. [1335-2], hereinafter "Wright Dep.," 69:9–11.)
The diagram reflects a knee viewed "anterior-posterior," that is, from front to back
or from back to front. When a right knee is viewed from front to back, the lateral side appears
on the left; for a left knee viewed from front to back, the lateral side appears on the right.
Though the diagram does not specifically include such medial or lateral labels, the court
understands that, in this diagram, medial (towards the midline of the body), is on the right side
of the diagram and lateral (the outside of the knee) is on the left. In other words, the diagram
depicts a right knee viewed from front to back, or a left knee, viewed from back to front.
The second angle that is relevant to the long-term success of the knee is the alignment
of the tibial component in relation to the tibial bone, which is measured by the β angle. If β is
less than 90 degrees, the tibial component is in varus alignment. If it is greater than or equal to
90 degrees, the tibial component is in valgus.
Though Dr. Goodman's report explains why varus alignment of the overall knee or of the
tibial component can lead to implant failure, he does not adequately explain how he determined
that Ms. Batty's components were in fact in varus alignment. There are only three sentences in
Dr. Goodman's report that describe the alignment of Ms. Batty's implant.
reviewed Ms. Batty's x-rays taken prior to her surgery and observed "a patient with progressive
degenerative arthritis of both knees with varus alignment." (Goodman Rep. at 17.) After the
surgery, Dr. Goodman states, "[t]he tibial components were placed in varus alignment, as seen
on the postoperative radiographs." (Id.) By March of 2011, he noted, "the right tibial component
was in varus and loose." (Id.) Based on this review of the x-rays, Dr. Goodman concludes that
"[t]he alignment of the knees remained in 4-5 degrees of varus postoperatively." (Id. at 18, 20.)
There is no explanation in Dr. Goodman's report for how he measured the alignment of Ms.
Batty's knees. During his deposition, however, he explained that he "relied on the specific
measurements, the numbers that are outlined in this report via the measurements from the
Hospital for Special Surgery," referring to the measurements Dr. Wright made in preparing his
expert report on Ms. Batty. (Dep. of Stuart Goodman, Ex. L to Pl.'s Goodman Mem. [1335-12],
hereinafter "Goodman Dep.," 132:14–17.)
There is, of course, nothing improper about Dr. Goodman's reliance on Dr. Wright's
measurements, but on this record, it is not clear to what extent he did so. Dr. Wright and Dr.
Goodman agreed that the tibial component was in varus in relation to the tibial bone, but they
state different opinions about the overall alignment of the knee. Dr. Wright concluded that the
overall angle of the knee was two degrees valgus, which is within what he believes is target
range of knee alignment. (Wright Dep. at 64:11–20, 69:12–17.) Dr. Goodman testified, as he
stated in his report, however, that the overall angle of the knee was "varus." (Goodman Dep. at
Zimmer attempts to massage this disagreement by arguing that when Dr. Goodman said
that the overall knee alignment was "varus" he really meant that it was "less valgus than what a
surgeon wants to achieve." (Goodman Dep. Errata Sheet at 131:12–13; see Zimmer Resp. to
Pl.'s Mot. To Exclude Testimony of Stuart Goodman, , hereinafter "Zimmer Goodman
Resp.," 4; Aff. of Stuart Goodman, Ex. E to Zimmer Goodman Resp. [1450-5], hereinafter
"Goodman Aff." ¶ 6.) Dr. Goodman testified at his deposition that the ideal overall alignment of
the knee is three to ten degrees of valgus. (Goodman Dep. 179:25–180:13.) So, Ms. Batty's
knee, which is two degrees valgus, is less valgus than ideal. (Zimmer Goodman Resp. at 4.)
Zimmer cites an article that provides some support for this interpretation of Dr. Goodman's
testimony: In a study of overall knee alignment after total knee replacements, the authors
present their findings in a bar graph, which characterizes "Varus" as "alignment below 2.4
degrees of valgus," "Neutral" is defined as alignment between 2.4 and 7.2 degrees of valgus,
and "Valgus" is defined as alignment above 7.2 degrees of valgus. (See David Fang, Merrill
Ritter, and Kenneth Davis, Coronal Alignment in Total Knee Arthroplasty: Just How Important Is
It?, 24 J. OF ARTHROPLASTY 39, 41 (2009), Ex. J to Zimmer Goodman Resp. [1450-10],
But even this explanation does not eliminate the confusion: Accepting
Zimmer's explanation, Ms. Batty's alignment of two degrees valgus would be one to nine
degrees away from ideal as defined by Goodman, not the "4–5" degrees Dr. Goodman presents
in his report. Dr. Goodman's affidavit attached to Zimmer's Response brief makes a further
attempt to resolve the matter by suggesting that "the ideal overall anatomic alignment is 6–7
degrees valgus, with a margin of error rate of 2–3 degrees," and thus Ms. Batty's alignment is
four to five degrees away from the "6–7 degrees valgus" ideal. (Zimmer Goodman Resp. at 4)
(citing Goodman Aff. ¶ 6.)
Zimmer's complicated explanation is theoretically plausible, but the court remains
concerned that Dr. Goodman's opinions regarding alignment may have been based on a simple
error in measuring the angles. More importantly, Dr. Goodman's testimony on this issue has a
strong probability of confusing and misleading the jury. To the extent it has probative value, that
proof appears to be cumulative of Dr. Wright's testimony regarding the alignment of Ms. Batty's
implants. See FED. R. EVID. 403. Dr. Goodman is, therefore, precluded from testifying about
the alignment of Ms. Batty's components.
Plaintiff's motion to exclude testimony by Dr. Stuart Goodman  regarding the
alignment of Ms. Batty's implant is granted. Plaintiff's motion to exclude the testimony of Dr.
Timothy Wright  is granted with respect to his "retrieval study" and denied with respect to
his analysis of the clinical literature documenting patient outcomes with the NexGen Flex.
Dated: August 27, 2015
REBECCA R. PALLMEYER
United States District Judge
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