                    FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

LISA STILWELL,                           
              Plaintiff-Appellant,              No. 05-15000
              v.
                                                 D.C. No.
                                              CV-03-01322-SRB
SMITH & NEPHEW, INC., a
corporation,                                     OPINION
             Defendant-Appellee.
                                         
        Appeal from the United States District Court
                 for the District of Arizona
         Susan R. Bolton, District Judge, Presiding

                  Argued and Submitted
        December 5, 2006—San Francisco, California

                      Filed April 11, 2007

     Before: Myron H. Bright,* Dorothy W. Nelson, and
             Marsha S. Berzon, Circuit Judges.

                    Opinion by Judge Bright




   *The Honorable Myron H. Bright, Senior United States Circuit Judge
for the Eighth Circuit, sitting by designation.

                               4069
4072             STILWELL v. SMITH & NEPHEW, INC.


                             COUNSEL

Joseph W. Charles, Glendale, Arizona, briefed and argued for
the appellant.

Raymond R. Cusack and Stephen T. Portell, Tucson, Arizona,
briefed for the appellee. Mr. Portell argued for the appellee.


                             OPINION

BRIGHT, Circuit Judge:

   Plaintiff and appellant Lisa Stilwell (“Stilwell”) sustained
two broken legs in a 1995 automobile accident. During her
surgical treatment and recovery, doctors twice implanted a
Russell-Taylor metal reconstruction nail (“RT nail”) to stabi-
lize a compound subtrochanteric fracture of her right femur.1
These two nails failed during the healing process, causing
Stilwell pain, suffering, and disability. She brought this action
against the defendant and appellee Smith & Nephew, Inc.,
manufacturer of the devices. Stilwell asserted claims based on
strict liability, negligence, and breach of warranty. The dis-
trict court rejected her claims for lack of proof of causation
and ordered summary judgment in favor of Smith & Nephew.




  1
    The RT nail takes its name from it co-designers, Doctors Thomas Rus-
sell and John Taylor.
                  STILWELL v. SMITH & NEPHEW, INC.                     4073
   Stilwell asserts a single issue on appeal. She argues that the
district court erred by barring the expert testimony of a metal-
lurgist, Arun Kumar, Ph.D., under Federal Rule of Evidence
702 and Daubert v. Merrell Dow Pharmaceuticals, Inc., 509
U.S. 579 (1993), and its progeny. Stilwell relied on the expert
opinion to prove causation and, after the court’s Rule 702
order, conceded that she could not prevail. We conclude that
the court wrongly excluded the testimony but, after reviewing
the record, affirm the grant of summary judgment for Smith
& Nephew because evidence of record, including Kumar’s
deposition testimony and reports, does not demonstrate that
any alleged defects were a cause of the delayed healing of
Stilwell’s fractured leg.

                                     I.

   In 1995, when Stilwell suffered a compound subtro-
chanteric fracture resulting in distal displacement and shorten-
ing of her right leg, doctors first attempted to repair her
fractured femur with an Omega screw and side plate.2 But—
after twice replacing loose screws in the side plate in March
1995 and May 1996—they determined that the bone had not
fused and the hardware had failed. Stilwell’s doctors replaced
the screw and plate in March 1998 with an RT nail, which
failed and was replaced with a similar device three years later,
in April 2001.3 In November 2002 doctors determined the sec-
ond nail had failed and replaced it with a different device.
   2
     A compound subtrochanteric fracture occurs when the shaft of the
femur fractures below the hip joint, causing the bone to protrude through
the skin. See STEDMAN’S MEDICAL DICTIONARY 712, 1720, 1878 (27th ed.
2000); see also Subtrochanteric fractures, WHEELESS’ TEXTBOOK OF ORTHO-
PAEDICS,      available       at     http://www.wheelessonline.com/ortho/
subtrochanteric_fractures (last visited Feb. 12, 2007).
   3
     An intermedullary nail, also called a rod, aligns and stabilizes a frac-
tured bone. It is inserted in the bone marrow canal of the femur and held
in place by screws. See Intramedullary Nailing of Femoral Shaft Frx,
WHEELESS’ TEXTBOOK OF ORTHOPAEDICS, available at http://www.wheeless
online.com/ortho/intramedullary_nailing_of_femoral_shaft_frx (last vis-
ited Feb. 12, 2007).
4074           STILWELL v. SMITH & NEPHEW, INC.
   Stilwell, asserting that the RT nails failed in April 2001 and
November 2002 because they were defectively designed or
manufactured, sought compensation from Smith & Nephew.
She hired Kumar to examine the two devices removed from
her leg and determine why they had failed. Kumar’s curricu-
lum vitae indicates that he specializes in the “[f]ailure analysis
of metallic and non-metallic . . . materials and electronic com-
ponents” and has “[e]xtensive experience in metallurgical
failure analysis of . . . medical implants.” He received a bach-
elors of science in physics, chemistry, and math; a bachelors
of engineering in metallurgical engineering; a masters of sci-
ence in engineering, with an emphasis in metallurgy and
metal processing; and finally a doctorate in engineering.
Kumar’s c.v. also lists numerous memberships in professional
societies, relevant work and teaching experience, and publica-
tions.

   Kumar issued his first report in August 2003. He conducted
three non-destructive tests on the RT nails and concluded that
they “fractured due to fatigue.” He noted that fatigue was “of
a low stress, high cycle type,” and that “sharp corners of the
rod at the intersection of the slant screw hole and the outer
diameter surface of the implant create[d] a high stress concen-
tration area, enabling fatigue cracks to initiate at low stress
levels.” He concluded that “[t]his constitutes a design/
manufacturing defect, since the sharp corners could be ground
and polished for a smoother transition between the two inter-
secting surfaces.”

   Smith & Nephew first deposed Kumar in February 2004.
Kumar responded repeatedly that his expertise was in metal-
lurgy, as opposed to medicine or biomechanical engineering.
He did, however, express his opinion regarding the potential
life of intermedullary nails:

    Q.    Are you saying that the intermedullary nails,
          which are the subject matter of this lawsuit,
               STILWELL v. SMITH & NEPHEW, INC.               4075
         would never fail if there was never any union
         [of the bones]?

    A.   I really don’t know the answer to that because
         I haven’t done any testing to prove that, but in
         the absence of the defect that I will point out to
         you, that will be the case.

Kumar also repeated the conclusion of his first report, that
further grinding and polishing could have extended the endur-
ance limit of the RT nails he examined.

   Kumar’s second report, delivered in April 2004, included
the findings of a series of destructive tests that he conducted
on the RT nails, in the presence of an expert hired by Smith
& Nephew. He compared his findings to the manufacturer’s
specifications and found that “[a] large variation in edge
radius can be seen from one side to the other; the fatigue
cracks had emanated at the sharper radius surface for both
rods.” Kumar explained:

    The sharper radii measurements were 0.0003 inch
    and 0.00125 inch, way below the minimum require-
    ment of the part drawing of 0.010 inch. This is a
    manufacturing defect and the sharper radius at the
    edge created a higher stress concentration factor,
    resulting in premature fatigue fracture of the rods.
    The variation in the radius around the slant hole is
    also a manufacturing defect and shows poor quality
    control during manufacturing.

As he did in his first report, Kumar concluded that the RT
nails suffered from correctable defects that shortened their
life.

   Smith & Nephew again deposed Kumar in May 2004. He
responded “out of [his] area of expertise” to a number of
questions designed to explore his knowledge of internal fixa-
4076          STILWELL v. SMITH & NEPHEW, INC.
tion devices like the RT nail, such as, “Would you agree that
as long as bone healing progresses normally an implant such
as the type of nails we have in question will not undergo
fatigue failure?” One exchange in particular characterizes the
tension between Smith & Nephew and Kumar:

      Q. With respect to these nails, though, would
    you agree that it’s race in time; you either get union
    of the bone or you get fatigue failure of the nail?

      A. Again, I’m not an expert in that area where
    one designs this for the union or nonunion [of
    bones]. I am looking at the failure from a metallurgi-
    cal standpoint only.

       Q. So in other words, we have deposed two of
    Lisa Stilwell’s orthopedic surgeons, Dr. Kramer and
    Dr. Reinhert [sic]. Both of them have testified under
    oath that based upon their experience as orthopedic
    surgeons there is a race in time that takes place. You
    either get union or healing of the fracture or you’re
    going to have fatigue failure of the rod.

      I take it you would not disagree with that or is that
    outside your area of expertise?

      A. That’s their expertise and I cannot comment
    on that.

       Q. So with respect to the measurements that you
    took, Doctor, where you have the .0003 you can’t
    tell me if that caused the rod to fail a week before it
    would have failed, two weeks before it would have
    failed or three weeks before it failed? You can’t put
    a quantitative distinction on that?

       A.   That’s correct.
               STILWELL v. SMITH & NEPHEW, INC.             4077
Kumar could not comment beyond his abstract knowledge of
metals:

       Q. So you can’t tell me whether or not the nail
    as designed met the criteria for which it was
    designed in being used as an implant to treat a sub-
    trochanteric fracture?

       A.   Correct.

According to his own testimony, he could examine the RT
nail only as an object composed of metal; he did not attempt
to testify regarding its design as a medical device.

   Armed with Kumar’s reports and deposition testimony,
Smith & Nephew moved to bar his testimony. The company
argued that he was unqualified to testify regarding the design,
manufacture, or use of the RT nail. His expertise as a metal-
lurgist, the company continued, should not qualify him to tes-
tify regarding whether a medical device made of metal failed
due to a design or manufacturing defect. Finally, the company
argued that his opinion that further grinding and polishing
could have extended the life of the RT nail was without scien-
tific basis.

   The district court, applying Daubert, concluded that Kumar
“acknowledged that he lacked the expertise to determine
whether the nails served the biomechanical purpose for which
they were designed.” His “concern[ ] only with metallurgical
issues,” the court continued, rendered “his opinions about the
defectiveness of the RT nails for use in bone healing . . . spec-
ulative, albeit speculation spawned from his testing relating to
the metallurgical integrity of the nails.” Because the dispute,
as the court described it, was not whether the RT nail would
suffer fatigue failure but rather whether the device was
designed to fail only after it succeeded in supporting a union
of the fractured bone, the court excluded Kumar’s testimony.
4078            STILWELL v. SMITH & NEPHEW, INC.
   The court also granted summary judgment for Smith &
Nephew. In addition to Kumar, Stilwell would have relied on
the deposition testimony of three treating physicians, Quentin
Kramer, M.D., Charles Reinert, M.D., and Mark Spangehl,
M.D. Doctor Reinert expressed concern that Stilwell’s “ciga-
rette smoking is very deleterious to fracture healing,” but that
he “didn’t see anything at surgery that would have made us
think that she would be unable to heal.” Doctor Spangehl
agreed with the statement that “failure rates of these types of
nails is relatively rare,” but qualified it by testifying that “rare
is sort of a relative thing . . . . because in most situations we
get on with treatment . . . . but a year, two years, three years,
that would sort of be within the time frame that . . . I wouldn’t
be surprised that it would fail.” Without Kumar’s testimony,
however, Stilwell conceded that her remaining evidence could
not propel her claim past summary judgment.

                                II.

  We review a district court’s decision to exclude testimony
pursuant to Federal Rule of Evidence 702, as the rule of evi-
dence is explained in Daubert v. Merrell Dow and its prog-
eny, for abuse of discretion. See United States v. Prime, 431
F.3d 1147, 1152 (9th Cir. 2005). The district court’s ruling is
entitled to deference, even when the exclusion of expert testi-
mony determines the outcome of a case. See Cabrera v.
Cordis Corp., 134 F.3d 1418, 1420 (9th Cir. 1998).

   [1] Federal Rule of Evidence 702 permits testimony by
experts qualified by “knowledge, skill, expertise, training, or
education” to testify “in the form of an opinion or otherwise”
based on “scientific, technical, or other specialized knowl-
edge” if that knowledge will “assist the trier of fact to under-
stand the evidence or to determine a fact in issue.” FED. R.
EVID. 702. The expert’s testimony must be “based upon suffi-
cient facts or data,” “the product of reliable principles and
methods,” and the expert must “appl[y] the principles and
methods reliably to the facts of the case.” Id. In Daubert and
                 STILWELL v. SMITH & NEPHEW, INC.                  4079
Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999), the
Supreme Court described the district court’s “gatekeeping
role,” and required that “all forms of expert testimony, not
just scientific testimony” survive scrutiny under Rule 702.
White v. Ford Motor Co., 312 F.3d 998, 1007 (9th Cir. 2002).

   [2] Rule 702 embodies “the twin concerns of ‘reliability’
. . . and ‘helpfulness.’ ” United States v. Mitchell, 365 F.3d
215, 234 (3d Cir. 2004); see Hemmings v. Tidyman’s Inc., 285
F.3d 1174, 1184 (9th Cir. 2002) (“Whether testimony is help-
ful within the meaning of Rule 702 is in essence a relevancy
inquiry.”). The test for reliability, however, “is not the cor-
rectness of the expert’s conclusions but the soundness of his
methodology.”4 Daubert v. Merrell Dow Pharms., Inc., 43
F.3d 1311, 1318 (9th Cir. 1995) (“Daubert II”). And, reliable
testimony must nevertheless be helpful. See Daubert, 509
U.S. at 591 (“ ‘Expert testimony which does not relate to any
issue in the case is not relevant, and ergo, non-helpful.’ ”
(quoting 3 Weinstein & Berger ¶ 702[02], p. 702-18.)). A
court may exclude testimony that falls short of achieving
either end.

                                  III.

   [3] The district court’s analysis in this case focused on the
helpfulness, rather than reliability, of Kumar’s testimony. The
court, however, mingled the analysis required by Federal Rule
of Evidence 702 for the admissibility of expert testimony and
Federal Rule of Civil Procedure 56 for summary judgment.
Though summary judgment enquires whether there is a “gen-
uine issue of material fact,” Rivera v. Philip Morris, Inc., 395
F.3d 1142, 1146 (9th Cir. 2005), Rule 702’s analysis is ordi-
  4
    Here Smith & Nephew suggests that Kumar misread the RT nail manu-
facturing drawing, and that the product did not deviate from the design
specification. That argument does not, however, undermine the admissibil-
ity of the testimony under Rule 702 and thus we will not address it here.
See Daubert II, 43 F.3d at 1318.
4080           STILWELL v. SMITH & NEPHEW, INC.
narily prospective. Expert testimony is helpful if it “will assist
the trier of fact.” FED. R. EVID. 702 (emphasis added). Thus
a district court may not exclude expert testimony simply
because the court can, at the time of summary judgment,
determine that the testimony does not result in a triable issue
of fact. Rather the court must determine whether there is “a
link between the expert’s testimony and the matter to be
proved.” United States v. Bighead, 128 F.3d 1329, 1335 (9th
Cir. 1997). The chain necessary to prevail on a claim may be
weakened by the absence of other evidence or testimony, but
that does not undermine the admissibility of Rule 702 evi-
dence.

  [4] The court, by concentrating its analysis on the eventual
merit of Stilwell’s claim, seemingly required Kumar’s testi-
mony to establish not only the presence of an alleged defect
but also causation.

    Were it established that the nails were designed so
    that they would not fatigue prior to bone union as
    Dr. Kumar initially assumed, Dr. Kumar’s testimony
    might be relevant to the determination of whether an
    unreasonably dangerous defect caused Plaintiff’s
    injury. However, given that there is no dispute that
    the nails failed due to fatigue and Dr. Kumar’s lack
    of expertise about both the intended fatigue life of
    intermedullary nails used to treat fractures and about
    the biological factors that impact the effectiveness of
    intermedullary nails in the bone healing process, Dr.
    Kumar’s opinion does little to advance this Court’s
    inquiry.

The court, though explaining in great detail why Kumar’s tes-
timony fell short of guaranteeing Stilwell would prevail,
failed to demonstrate that a metallurgist’s testimony that the
metal device was both poorly manufactured and could have
been designed to last longer than it did is not relevant to this
                 STILWELL v. SMITH & NEPHEW, INC.                   4081
products liability case. We thus reject the court’s Rule 702
order.

                                   IV.

   [5] We turn next to the order granting summary judgment.
Stilwell, faced with the exclusion of her lone expert, conceded
defeat in the district court, resulting in a single page order
granting Smith & Nephew’s summary judgment motion. Nev-
ertheless, the district court’s Rule 702 order and the parties
here have consistently focused on the merits of Stilwell’s
claim, and the ability of Kumar to support that claim.5 Though
we determine that the district court’s decision regarding the
admissibility of Kumar’s testimony cannot be sustained, we
construe the court’s order and the parties’ appellate responses
as an analysis of summary judgment. Accordingly, this is the
rare case in which it is proper for us to exercise our discretion
to consider a legal issue for the first time on appeal. See
Delange v. Dutra Const. Co., 183 F.3d 916, 919 n.3 (9th Cir.
1999); Self-Realization Fellowship Church v. Ananda Church
of Self-Realization, 59 F.3d 902, 912 (9th Cir. 1995).

   Our review of the grant of summary judgment is plenary,
and we view the facts in the light most favorable to Stilwell,
the non-moving party. See Ward v. Circus Circus Casinos,
Inc., 473 F.3d 994, 997 (9th Cir. 2007). Because we deter-
mine that the court erred by rejecting Kumar’s testimony, we
will consider his reports and deposition testimony in addition
to the other record evidence.

  Viewing the entire record we are convinced that the district
  5
    In addition we note that at oral argument Stilwell provided this court
with her argument against summary judgment. Counsel conceded that Stil-
well relied only on Kumar and her treating physicians and discussed the
testimony and evidence provided by each of those individuals. Stilwell’s
argument and the entire record at summary judgment are therefore before
us.
4082             STILWELL v. SMITH & NEPHEW, INC.
court properly granted summary judgment for Smith &
Nephew. Stilwell’s argument is nebulous, but at oral argu-
ment her counsel contended that Kumar was the only appro-
priate expert because he could testify that the RT nails did not
conform to some design specifications (ostensibly a manufac-
turing defect) and that alterations to their design could have
extended their life by an unspecified period of time.6 Stil-
well’s counsel agreed that the RT nail was not designed to
perform indefinitely, but also stated that it is “common sense,
[that] you wouldn’t put a piece of metal in there and expect
it to break in a little over a year.” Indeed, her counsel claimed
that no expert could testify regarding the expected length of
the healing process, and consequently the period of time the
RT nail should perform, because only a treating physician
could determine when an individual patient’s injury had
healed by examining x-ray films. Stilwell’s argument thus
asks us to blindly accept the RT nails’ failure before her frac-
ture healed as prima facie evidence that they were defective.

   [6] Stilwell’s argument against summary judgment cannot
sustain her claims. Her complaint included counts sounding in
negligence and strict liability. We apply state law to a prod-
ucts liability claim brought in federal district court pursuant
to diversity jurisdiction. See Adams v. Synthes Spine Co., 298
F.3d 1114, 1117 (9th Cir. 2002); Kay v. Cessna Aircraft Co.,
548 F.2d 1370, 1372 (9th Cir. 1977). Arizona permits tort
claims against medical device manufacturers, see Fiore v.
Collagen Corp., 930 P.2d 477, 485 (Ariz. Ct. App. 1996), and
adopts the Restatement (Second) of Tort’s strict liability stan-
dard, see State Farm Ins. Cos. v. Premier Manufactured Sys.,
Inc., 142 P.3d 1232, 1234 n.2 (Ariz. Ct. App. 2006); Golonka
v. General Motors Corp., 65 P.3d 956, 962 (Ariz. Ct. App.
2003). Absent a statute to the contrary, the state also adopts
the Restatement’s negligence standard. See Calnimptewa v.
  6
    We are mindful that Smith & Nephew’s expert, Dr. Wilson Hayes,
contradicted Kumar’s conclusion, but we interpret the factual dispute in
Stilwell’s favor, as we must at summary judgment.
               STILWELL v. SMITH & NEPHEW, INC.             4083
Flagstaff Police Dep’t, 30 P.3d 634, 639 (Ariz. Ct. App.
2001).

   [7] Claims such as Stilwell’s must rely on the allegation
that a product is defective. See Dart v. Wiebe Mfg., Inc., 709
P.2d 876, 878 n.1 (Ariz. 1985); Wilson v. United States Eleva-
tor Corp., 972 P.2d 235, 256 (Ariz. Ct. App. 1998). The Ari-
zona courts have described the myriad standards applied to
determine whether a product is defective as a result of its
design or manufacture. See, e.g., Byrns v. Riddell, Inc., 550
P.2d 1065, 1068 (Ariz. 1976); Gomulka v. Yavapai Mach. &
Auto Parts, Inc., 745 P.2d 986, 988-89 (Ariz. Ct. App. 1987).
Nevertheless, three classic premises predominate. A negli-
gence claim begins with the assertion that a manufacturer pro-
duced a product that fails to meet “the purpose for which it
is designed.” Campo v. Scofield, 95 N.E.2d 802, 804 (N.Y.
Ct. App. 1950) (quoted in Morrow v. Trailmobile, Inc., 473
P.2d 780, 784 (Ariz. Ct. App. 1970)). Likewise, a strict liabil-
ity claim arises when a product is in a “defective condition
unreasonably dangerous,” Lunt v. Brady Mfg. Corp., 475 P.2d
964, 966 (Ariz. Ct. App. 1970), and the product “ ‘fail[s] to
perform as safely as an ordinary consumer would expect
when used in an intended or reasonable manner’ ” (the con-
sumer expectation test), or “ ‘the benefits of a challenged
design . . . outweigh the risk of danger inherent in the
design’ ” (risk/benefit analysis). Golonka, 65 P.3d at 961-62
(quoting Dart, 709 P.2d at 879); see Dart, 709 P.2d at 878
(observing that the consumer expectation test encompasses
manufacturing defect); Restatement (Second) of Torts: Strict
Liability § 402A cmt. g (1965). (“The rule stated in this Sec-
tion applies only where the product is, at the time it leaves the
seller’s hands, in a condition not contemplated by the ultimate
consumer, which will be unreasonably dangerous to him.”).

  [8] Underlying all three potential standards for a defect is
some understanding of the product’s purpose. See also
Mather v. Caterpillar Tractor Corp., 533 P.2d 717, 719 (Ariz.
Ct. App. 1975) (“The difference between the two theories of
4084           STILWELL v. SMITH & NEPHEW, INC.
liability in a defective design case is that under strict liability
the manufacturer can be held liable despite its best efforts to
make or design a safe product.”). But that is the evidence that
Stilwell failed to provide in the district court. Her doctors tes-
tified that the RT nails implanted to stabilize her fractured
femur failed, and Kumar testified regarding some design and
manufacture improvements that could have, in his opinion,
extended the life of the RT nail. Stilwell, though, has not
pointed to any evidence, beyond her doctors’ impressions
regarding the failure rate of the RT nail, to explain to a jury
the intended duration of its use, which she conceded was not
indefinite. To the contrary, Doctor Reinert expressed concern
that Stilwell’s cigarette use would impede her healing and
Doctor Spangehl stated that he would not be surprised if an
intermedullary rod, like Stilwell’s, failed after one year,
which is longer than the time expected for the healing pro-
cess. (Stilwell’s first RT nail failed after three years and the
second after twenty months.)

   [9] Given the opportunity at oral argument, Stilwell again
failed to explain the defect that formed the basis for her claim.
She seemed to suggest that, at a minimum, the second RT nail
should have performed for longer than it did, but she did not
rely on any record evidence to support that contention. She
has repeatedly reminded us that her treating physicians testi-
fied that a RT nail failure is rare, yet rarity does not indicate
infallibility. Stilwell’s vague arguments regarding the
expected life of the RT nail thus do not refute Smith & Neph-
ew’s evidence that the RT nails performed as intended in this
case. In sum, the addition of the rejected testimony of Kumar,
if added to other evidence and considered in the light most
favorable to Stilwell, does not establish that the RT nails in
question caused any actionable harm to Stilwell.

                                V.

   Accordingly we reject the district court’s order excluding
the Kumar testimony but AFFIRM the court’s order granting
summary judgment for Smith & Nephew.
