  United States Court of Appeals
      for the Federal Circuit
                ______________________

                  ARTHREX, INC.,
                     Appellant

                          v.

 SMITH & NEPHEW, INC., ARTHROCARE CORP.,
                 Appellees

                  UNITED STATES,
                      Intervenor
                ______________________

                      2018-1584
                ______________________

    Appeal from the United States Patent and Trademark
Office, Patent Trial and Appeal Board in No. IPR2016-
00918.
                 ______________________

               Decided: August 21, 2019
                ______________________

   ANTHONY P. CHO, Carlson, Gaskey & Olds, PC, Bir-
mingham, MI, argued for appellant. Also represented by
DAVID J. GASKEY, JESSICA E. ZILBERBERG.

    NATHAN R. SPEED, Wolf, Greenfield & Sacks, PC, Bos-
ton, MA, argued for appellees. Also represented by
RICHARD GIUNTA; MICHAEL N. RADER, New York, NY.

   DENNIS FAN, Appellate Staff, Civil Division, United
2                       ARTHREX, INC. v. SMITH & NEPHEW, INC.




States Department of Justice, Washington, DC, argued for
intervenor. Also represented by SCOTT R. MCINTOSH,
JOSEPH H. HUNT, KATHERINE TWOMEY ALLEN; THOMAS W.
KRAUSE, JOSEPH MATAL, FARHEENA YASMEEN RASHEED, Of-
fice of the Solicitor, United States Patent and Trademark
Office, Alexandria, VA.
                   ______________________

      Before DYK, CHEN, and STOLL, Circuit Judges.
STOLL, Circuit Judge.
    In an inter partes review, the Patent Trial and Appeal
Board ruled claims 10 and 11 of Arthrex, Inc.’s U.S. Patent
No. 8,821,541 invalid. In doing so, the Board employed dif-
ferent language than Smith & Nephew, Inc.’s petition to
explain why a person of ordinary skill in the art would have
been motivated to combine the teachings of the prior art.
Arthrex asserts that this warrants reversal, but the
Board’s minor variation in wording does not violate the
safeguards of the Administrative Procedure Act (APA) and
did not deprive Arthrex of an opportunity to be heard. Ac-
cordingly, we hold that the Board did not violate Arthrex’s
procedural rights. And because the Board’s findings have
substantial evidence support, its claim constructions are
correct, and Arthrex has not articulated a cognizable con-
stitutional challenge to IPR for its patent, we affirm the
Board.
                        BACKGROUND
                              I
     The ’541 patent describes a surgical suture anchor used
to reattach soft tissue to bone. ’541 patent col. 1 ll. 25–35.
The disclosed “fully threaded suture anchor” includes “an
eyelet shield that is molded into the distal part of the bio-
degradable suture anchor.” Id. at col. 2 ll. 31–35. The eye-
let shield acts as a rigid support for the sutures needed to
hold the soft tissue, “provid[ing] the strength necessary to
ARTHREX, INC. v. SMITH & NEPHEW, INC.                      3



secure the sutures.” Id. at col. 5 ll. 41–42, 51–57. The pa-
tent explains that because the support is molded into the
anchor structure (as opposed to being a separate compo-
nent), it “provides greater security to prevent pull-out of
the suture.” Id. at col. 5 ll. 52–56.
    Figure 5 of the ’541 patent illustrates the helical
threading on body 3 and the integral rigid support (eyelet
shield 9) of the suture anchor 1:




    Independent claims 10 and 11 are at issue here. They
recite:
   10. A suture anchor assembly comprising:
   an anchor body including a longitudinal axis, a
   proximal end, a distal end, and a central passage
   extending along the longitudinal axis from an
   opening at the proximal end of the anchor body
   through a portion of a length of the anchor body,
   wherein the opening is a first suture opening, the
   anchor body including a second suture opening dis-
   posed distal of the first suture opening, and a third
   suture opening disposed distal of the second suture
   opening, wherein a helical thread defines a perim-
   eter at least around the proximal end of the anchor
   body;
4                      ARTHREX, INC. v. SMITH & NEPHEW, INC.




    a rigid support extending across the central pas-
    sage, the rigid support having a first portion and a
    second portion spaced from the first portion, the
    first portion branching from a first wall portion of
    the anchor body and the second portion branching
    from a second wall portion of the anchor body,
    wherein the third suture opening is disposed distal
    of the rigid support;
    at least one suture strand having a suture length
    threaded into the central passage, supported by the
    rigid support, and threaded past the proximal end
    of the anchor body, wherein at least a portion of the
    at least one suture strand is disposed in the central
    passage between the rigid support and the opening
    at the proximal end, and the at least one suture
    strand is disposed in the first suture opening, the
    second suture opening, and the third suture open-
    ing; and
    a driver including a shaft having a shaft length,
    wherein the shaft engages the anchor body, and the
    suture length of the at least one suture strand is
    greater than the shaft length of the shaft.
    11. A suture anchor assembly comprising:
    an anchor body including a distal end, a proximal
    end having an opening, a central longitudinal axis,
    a first wall portion, a second wall portion spaced
    opposite to the first wall portion, and a suture pas-
    sage beginning at the proximal end of the anchor
    body, wherein the suture passage extends about
    the central longitudinal axis, and the suture pas-
    sage extends from the opening located at the prox-
    imal end of the anchor body and at least partially
    along a length of the anchor body, wherein the
    opening is a first suture opening that is encircled
    by a perimeter of the anchor body, a second suture
    opening extends through a portion of the anchor
ARTHREX, INC. v. SMITH & NEPHEW, INC.                       5



    body, and a third suture opening extends through
    the anchor body, wherein the third suture opening
    is disposed distal of the second suture opening;
    a rigid support integral with the anchor body to de-
    fine a single-piece component, wherein the rigid
    support extends across the suture passage and has
    a first portion and a second portion spaced from the
    first portion, the first portion branching from the
    first wall portion of the anchor body and the second
    portion branching from the second wall portion of
    the anchor body, and the rigid support is spaced ax-
    ially away from the opening at the proximal end
    along the central longitudinal axis; and
    at least one suture strand threaded into the suture
    passage, supported by the rigid support, and hav-
    ing ends that extend past the proximal end of the
    anchor body, and the at least one suture strand is
    disposed in the first suture opening, the second su-
    ture opening, and the third suture opening.
Id. at col. 7 l. 58–col. 8 l. 59 (as amended by Certificate of
Correction) (emphases added to disputed claim terms).
                              II
    Smith & Nephew sought IPR of claims 10 and 11 of the
’541 patent. It challenged both claims as obvious over U.S.
Pub. No. 2006/0271060 (“Gordon”) and U.S. Patent
No. 7,322,978 (“West”).
   Gordon discloses a bone anchor in which a suture loops
about a pulley 182 positioned within the anchor body.
6                      ARTHREX, INC. v. SMITH & NEPHEW, INC.




J.A. 1758, ¶¶ [0084]–[0086]. Figure 23 illustrates the pul-
ley 182 held in place in holes 184a, b.




J.A. 1747. Smith & Nephew asserted that Gordon dis-
closed nearly all of the claimed features, including the rigid
support, which Smith & Nephew identified as pulley 182.
As relevant here, however, Smith & Nephew acknowledged
that Gordon did not expressly disclose that the pulley was
“integral with the anchor body to define a single-piece com-
ponent,” as required by claim 11. J.A. 228. For that fea-
ture, Smith & Nephew relied on West.
    West also describes a bone anchor 10, as shown in Fig-
ure 1, reproduced below.
ARTHREX, INC. v. SMITH & NEPHEW, INC.                     7




J.A. 1762. In West’s anchor, “[o]ne or more pins [23a and
23b] are fixed within the bore of the anchor body [12]. One
or more sutures can be looped on the pins [23a and 23b].”
J.A. 1760, Abstract. West explains that to manufacture
the bone anchor, “anchor body 12 and posts 23 can be cast
and formed in a die. Alternatively anchor body 12 can be
cast or formed and posts 23a and 23b inserted later.”
J.A. 1768 at col. 7 ll. 41–44; see also J.A. 1767 at col. 5
ll. 58–60. Smith & Nephew argued that this disclosure
would have motivated one of ordinary skill to manufacture
the Gordon anchor using a casting process, creating a “rigid
support integral with the anchor body to define a single-
piece component,” as recited in claim 11. J.A. 217–19. Re-
lying on its expert’s testimony, Smith & Nephew asserted
that using the West casting process would minimize the
materials used in the anchor, thus facilitating regulatory
approval, and would reduce the likelihood of the pulley sep-
arating from the anchor body. J.A. 218–19. It also as-
serted that the casting process was “a well-known and
accepted technique for creating medical implants” and
“would have been a simple design choice.” J.A. 218.
8                      ARTHREX, INC. v. SMITH & NEPHEW, INC.




     Smith & Nephew further argued that claim 11 was an-
ticipated by U.S. Patent No. 5,464,427 (“Curtis”), which de-
scribes another bone anchor, and that claim 10 would have
been obvious over a combination of Curtis and other refer-
ences. Curtis discloses a threaded anchor that expands to
lodge into the bone rather than being rotated into the bone.
J.A. 1776–77 at col. 2 ll. 29–33, col. 3 ll. 12–16.
    Among other things, Arthrex disputed whether a per-
son of ordinary skill would have been motivated to modify
Gordon in view of West to achieve the invention of claim 11,
and it asserted that the Curtis ground did not include the
“helical thread” of claim 10 under the correct construction
of that term. In its final written decision, the Board disa-
greed and ruled that Smith & Nephew had shown both
claims unpatentable on both the Gordon and West and the
Curtis grounds. Arthrex appeals.
                        DISCUSSION
     On review of the Board’s final written decisions, we
evaluate whether the Board’s factual findings are sup-
ported by substantial evidence. See Belden Inc. v. Berk-Tek
LLC, 805 F.3d 1064, 1073 (Fed. Cir. 2015). We review the
Board’s legal determinations de novo. Id. And we ensure
the Board complies with statutory and constitutional re-
quirements. Wi-Fi One, LLC v. Broadcom Corp., 878 F.3d
1364, 1374 (Fed. Cir. 2018) (en banc) (“Enforcing statutory
limits on an agency’s authority to act is precisely the type
of issue that courts have historically reviewed.”); Belden,
805 F.3d at 1080 (reviewing alleged denial of procedural
due process rights).
    Arthrex challenges the Board’s determination that
Smith & Nephew proved claims 11 and 10 unpatentable,
and it attacks the constitutionality of IPRs as applied to its
patent. We address each argument in turn.
ARTHREX, INC. v. SMITH & NEPHEW, INC.                     9



                             I
    We begin with claim 11. The Board determined that
one of ordinary skill would have found the claimed inven-
tion obvious over Gordon and West, a conclusion Arthrex
attacks both procedurally and substantively. Because the
Board did not violate Arthrex’s procedural rights, and be-
cause substantial evidence supports the Board’s conclusion
that a person of ordinary skill would have been motivated
to combine the teachings of Gordon and West to achieve the
claimed invention, we affirm. Because we affirm the
Board’s finding of unpatentability based on Gordon in view
of West, we do not reach Arthrex’s challenges to the Board’s
finding that claim 11 is anticipated by Curtis.
                             A
    Arthrex first contends that the Board impermissibly
relied on a new theory of motivation to combine in its final
written decision. As we have often explained, IPR proceed-
ings are formal administrative adjudications subject to the
procedural requirements of the APA. See, e.g., Dell Inc. v.
Acceleron, LLC, 818 F.3d 1293, 1298 (Fed. Cir.
2016); Belden, 805 F.3d at 1080. One of these require-
ments is that “‘an agency may not change theories in mid-
stream without giving respondents reasonable notice of the
change’ and ‘the opportunity to present argument under
the new theory.’” Belden, 805 F.3d at 1080 (quoting Rodale
Press, Inc. v. FTC, 407 F.2d 1252, 1256–57 (D.C. Cir.
1968)); see also 5 U.S.C. § 554(b)(3). Nor may the Board
craft new grounds of unpatentability not advanced by the
petitioner. See In re NuVasive, Inc., 841 F.3d 966, 971–72
(Fed. Cir. 2016); In re Magnum Oil Tools Int’l, Ltd.,
829 F.3d 1364, 1381 (Fed. Cir. 2016).
     Arthrex argues that by describing West’s casting
method as “preferred,” a characterization not found in
Smith & Nephew’s petition, the Board crafted a new reason
for combining Gordon and West and violated its procedural
rights. We disagree. Though the Board used different
10                     ARTHREX, INC. v. SMITH & NEPHEW, INC.




language than the petition in its discussion of whether one
of ordinary skill would have been motivated to combine
Gordon and West, it did not introduce new issues or theo-
ries into the proceeding. Rather, the Board properly re-
solved the parties’ dispute about the scope and content of
West’s disclosure in order to evaluate the theory of obvious-
ness raised in Smith & Nephew’s petition.
    West describes that an “anchor body 12 and posts 23
can be cast and formed in a die. Alternatively anchor
body 12 can be cast or formed and posts 23a and 23b in-
serted later.” J.A. 1768 at col. 7 ll. 41–47 (emphasis
added). Pointing to this statement, the petition proposed
that a person of ordinary skill would have had “several rea-
sons” to combine West and Gordon, including that the cast-
ing process disclosed by West was a “well-known technique
[whose use] would have been a simple design choice.”
J.A. 218. Smith & Nephew’s expert relied on the same pas-
sage as support for his opinion that a person of ordinary
skill would have found it obvious to implement Gordon’s
anchor using West’s casting method. See J.A. 1648–50.
Throughout the proceeding, the parties disputed how a per-
son of ordinary skill would have understood that specific
portion of West’s disclosure and whether that disclosure
would have motivated a person of ordinary skill to combine
West and Gordon as Smith & Nephew proposed. Arthrex
had—and took—the opportunity to argue these issues, as-
serting that West’s casting method would be inherently
problematic. J.A. 402–05, 421–30.
     In the final written decision, the Board examined the
parties’ arguments and the portion of West’s disclosure
cited in the petition. In considering that disclosure, the
Board noted that West’s presentation of two manufactur-
ing options suggests that the first option, casting, is “pri-
mary” and “preferred.” See Smith & Nephew, Inc. v.
Arthrex, Inc., No. IPR2016-00918, 2017 WL 4677229,
at *22, *27 (P.T.A.B. Oct. 16, 2017). It concluded that, as
the petition had argued, one of ordinary skill, reviewing
ARTHREX, INC. v. SMITH & NEPHEW, INC.                     11



West, would have applied West’s casting method to Gordon
because choosing the “preferred option” presented by West
“would have been an obvious choice of the designer.” Id.
at *27.
    Arthrex is correct that the Board’s use of “preferred”
differs from the petition’s characterization of West’s cast-
ing as “well-known,” “accepted,” and “simple.” J.A. 218.
But in finding motivation to combine, the Board relied on
the same few lines of West as the petition. It considered
the same proposed combination of West’s casting technique
and Gordon’s anchor. And it ruled on the same theory of
obviousness presented in the petition—that one of ordinary
skill would have recognized that using West’s casting with
Gordon’s anchor was a “simple design choice.” See id.;
Smith & Nephew, 2017 WL 4677229, at *27 (determining
that use of casting “would have been an obvious choice of
the designer”).
    In these circumstances, the mere fact that the Board
did not use the exact language of the petition in the final
written decision does not mean it changed theories in a
manner inconsistent with the APA and our case law. In
Sirona Dental Systems GmbH v. Institut Straumann AG,
for example, we affirmed the Board even though it charac-
terized a reference as providing “geometry data” rather
than as providing 3-D plaster model data, as the petition
had. 892 F.3d 1349, 1356 (Fed. Cir. 2018). We explained
that, as in this case, the Board had cited the same disclo-
sure as the petition and the parties had disputed the mean-
ing of that disclosure throughout the trial. Id. As a result,
the petition provided the patent owner with notice and an
opportunity to address the portions of the reference relied
on by the Board, and we found no APA violation. Id.; see
also Genzyme Therapeutic Prod. Ltd. P’ship v. Biomarin
Pharm. Inc., 825 F.3d 1360, 1366 (Fed. Cir. 2016) (finding
no violation where “[t]he Board’s final written decisions
were based on the same combinations of references that
12                     ARTHREX, INC. v. SMITH & NEPHEW, INC.




were set forth in its institution decisions”). The same out-
come follows here.
    Though Arthrex argues otherwise, this case is unlike
those in which we have found an APA issue. In Magnum
Oil Tools, we found an APA violation where the Board
mixed arguments raised in two different grounds of obvi-
ousness in the petition to craft its own new theory of un-
patentability. 829 F.3d at 1372–73, 1377. Similarly, in
SAS Institute v. ComplementSoft, LLC, we faulted the
Board for announcing a claim construction that “varie[d]
significantly” from the uncontested construction an-
nounced in the institution decision. 825 F.3d 1341, 1351
(Fed. Cir. 2016) (emphasis added), rev’d and remanded on
other grounds sub nom. SAS Inst., Inc. v. Iancu, 138 S. Ct.
1348 (2018). And in NuVasive, we found error where the
Board relied on portions of the prior art different than
those presented in the petition as an “essential part of its
obviousness findings.” 841 F.3d at 971. In all three cases,
the Board departed markedly from the evidence and theo-
ries presented by the petition or institution decision, creat-
ing unfair surprise. Here, however, the Board properly
relied on the same references, the same disclosures, and
the same obviousness theories advanced by the petition
and debated by the parties to conclude claim 11 would have
been obvious.
    Nor is this, as Arthrex elsewhere suggests, a case in
which the Board’s decision is so divorced from the argu-
ments presented by the petitioner as to impair appellate
review. See Rovalma, S.A. v. Bohler-Edelstahl GmbH &
Co. KG, 856 F.3d 1019, 1029 (Fed. Cir. 2017) (vacating and
remanding where the Board’s decision did not allow “deter-
min[ation of] how the Board reached the conclusion that
the challenged claims would have been obvious . . . [or]
whether the Board’s actions complied with the APA’s pro-
cedural requirements”). Rather, the Board clearly identi-
fied the portion of West it relied on, explained the evidence
and arguments, and agreed with Smith & Nephew that the
ARTHREX, INC. v. SMITH & NEPHEW, INC.                       13



claims would have been obvious over Gordon in view of
West. See Outdry Techs. Corp. v. Geox S.p.A., 859 F.3d
1364, 1369–70 (Fed. Cir. 2017) (finding the Board’s deci-
sion sufficient where it “clearly articulated [party’s] argu-
ments,” “engaged in reasoned decisionmaking,” and
“sufficiently articulated its analysis in its opinion to permit
our review”). We therefore reject Arthrex’s assertion that
the Board violated its procedural rights.
                              B
    Arthrex also contends that even if the Board’s decision
was procedurally proper, the Board erred in finding
Smith & Nephew had shown a motivation to combine Gor-
don and West by a preponderance of the evidence. We re-
view this question of fact for substantial evidence. In re
Kahn, 441 F.3d 977, 985 (Fed. Cir. 2006). When consider-
ing whether the teachings of multiple references render a
claim obvious, courts “determine whether there was an ap-
parent reason to combine the known elements in the fash-
ion claimed by the patent at issue.” KSR Int’l Co. v. Teleflex
Inc., 550 U.S. 398, 418 (2007). The analysis is a flexible
one, accounting for “the inferences and creative steps that
a person of ordinary skill in the art would employ.” Id.
     Substantial evidence supports the Board’s determina-
tion that a person of ordinary skill would have been moti-
vated to apply West’s casting method to Gordon’s anchor.
The Board correctly found that West expressly identifies
two possible methods for making a rigid support. See
Smith & Nephew, 2017 WL 4677229, at *26. West states
that “anchor body 12 and posts 23 can be cast and formed
in a die. Alternatively anchor body 12 can be cast or formed
and posts 23a and 23b inserted later.” J.A. 1768 at col. 7
ll. 41–47 (emphasis added). As the Board found, this word-
ing suggests that the default or preferred option disclosed
by West is die casting. See Smith & Nephew, 2017 WL
4677229, at *27; see also id. at *22 (noting that West de-
scribes casting as the “primary” option). Given these two
14                     ARTHREX, INC. v. SMITH & NEPHEW, INC.




options, the Board reasonably determined that forming the
entire anchor integrally, as a single piece, “would have
been an obvious choice of the designer.” Id. at *27.
    Additional record evidence supports this result.
Smith & Nephew’s expert, Mr. Mark Ritchart, offered de-
tailed testimony explaining that using a casting process
would result in a stronger anchor more likely to receive reg-
ulatory approval. J.A. 1649–50. Professor Alexander Slo-
cum testified similarly, stating that the design would also
“decrease . . . manufacturing costs,” “prevent the suture
anchor from appearing in and obscuring the bone in x-
rays,” and “reduce[] . . . stress concentrations” on the an-
chor. J.A. 2869–70.
    Arthrex correctly notes that some evidence arguably
cuts against the Board’s conclusion. Mr. Ritchart acknowl-
edged potential complexities of casting, J.A. 3839, and Ar-
threx’s expert, Dr. Kenneth Gall, argued at length that a
person of ordinary skill would not have applied West to
Gordon as Smith & Nephew argued, see, e.g., J.A. 3747–49.
But the presence of evidence supporting the opposite out-
come does not preclude substantial evidence from support-
ing the Board’s fact finding. See, e.g., Falkner v. Inglis,
448 F.3d 1357, 1364 (Fed. Cir. 2006) (“An agency decision
can be supported by substantial evidence, even where the
record will support several reasonable but contradictory
conclusions.”). And our task on appeal is simply to evalu-
ate whether substantial evidence supports the Board’s fact
finding; “[w]e may not reweigh . . . evidence.” In re Warsaw
Orthopedic, Inc., 832 F.3d 1327, 1333 (Fed. Cir. 2016). Be-
cause the Board’s finding of motivation to combine is sup-
ported by such evidence as “a reasonable mind might
accept as adequate,” and, as noted above, the Board did not
err procedurally, we affirm the Board’s conclusion that
claim 11 would have been obvious over Gordon in view of
West. Kahn, 441 F.3d at 985.
ARTHREX, INC. v. SMITH & NEPHEW, INC.                      15



                              II
    We next address claim 10. Arthrex challenges the
Board’s construction of “helical thread,” asserting that this
term should have been construed to require that the helical
thread “facilitates rotary insertion of the anchor into bone.”
Appellant’s Br. 55. Because the Board correctly construed
the term and Arthrex does not otherwise challenge the
Board’s finding that the Curtis ground renders claim 10
unpatentable, we affirm without considering whether
claim 10 is also unpatentable based on Gordon and West.
    We review the Board’s ultimate claim constructions de
novo, In re Man Mach. Interface Techs. LLC, 822 F.3d 1282,
1285 (Fed. Cir. 2016), and we review any subsidiary factual
findings involving extrinsic evidence for substantial evi-
dence, Teva Pharm. USA, Inc. v. Sandoz, Inc., 135 S. Ct.
831, 841 (2015). The broadest reasonable interpretation
standard applies to this IPR. 1 Thus, the Board’s construc-
tion must be reasonable in light of the record evidence and
the understanding of one skilled in the art. See Microsoft
Corp. v. Proxyconn, Inc., 789 F.3d 1292, 1298 (Fed. Cir.
2015), overruled on other grounds by Aqua Prods., Inc. v.
Matal, 872 F.3d 1290 (Fed. Cir. 2017) (en banc).
    Here, the Board correctly construed “helical thread” as
“a helical ridge or raised surface that serves to retain the
anchor in bone” without limiting the term to threads used



    1    Per recent regulation, the Board applies the Phil-
lips claim construction standard to petitions filed on or af-
ter November 13, 2018. See Changes to the Claim
Construction Standard for Interpreting Claims in Trial
Proceedings Before the Patent Trial and Appeal Board,
83 Fed. Reg. 51,340 (Oct. 11, 2018) (to be codified at
37 C.F.R. pt. 42). Because Smith & Nephew filed its peti-
tion before November 13, 2018, we apply the broadest rea-
sonable interpretation standard.
16                     ARTHREX, INC. v. SMITH & NEPHEW, INC.




to facilitate rotary insertion. Smith & Nephew, 2017 WL
4677229, at *19. Claim 10 recites “a helical thread defines
a perimeter at least around the proximal end of the anchor
body.” This plain claim language suggests that the “helical
thread” is a structural feature that “defines a perimeter.”
’541 patent col. 8 ll. 7–8. Consistent with the Board’s con-
struction, the claim does not include any functional limita-
tions. A single sentence in the “detailed description of the
preferred embodiments” in the specification describes ro-
tating threaded anchors into bone using a driver. Id.
at col. 6 ll. 4–8. But our case law counsels against incorpo-
rating a feature of a preferred embodiment into the claims,
particularly where, as here, the feature at issue is men-
tioned only tangentially. See, e.g., In re Van Geuns,
988 F.2d 1181, 1184 (Fed. Cir. 1993) (“[L]imitations are not
to be read into the claims from the specification.”). No-
where does the specification mandate that threaded an-
chors must be rotated into bone. Rather, the specification
acknowledges that only “[s]ome threaded suture anchors
are designed to be inserted into a pre-drilled hole.” ’541 pa-
tent col. 1 ll. 36–39 (emphasis added).
    The prosecution history further supports the Board’s
decision not to limit the claimed “helical thread[s]” to those
used for rotational insertion. As Arthrex concedes, Appel-
lant’s Br. 60–61 & n.10, three references cited during pros-
ecution describe threaded anchors that are not rotated into
the bone. As we have explained, art “cited in the prosecu-
tion history of the patent constitutes intrinsic evidence.” V-
Formation, Inc. v. Benetton Grp. SpA, 401 F.3d 1307, 1311
(Fed. Cir. 2005) (quoting Kumar v. Ovonic Battery Co.,
351 F.3d 1364, 1368 (Fed. Cir. 2003)) (explaining that a
claim term may be construed based on its “usage in the
prior art that was cited in the patent”). These references
confirm that the broadest reasonable construction of the
term “helical thread” is not limited to threads used for ro-
tatory insertion. Though Arthrex cites dictionaries that
may support a narrower interpretation, see Appellant’s
ARTHREX, INC. v. SMITH & NEPHEW, INC.                      17



Br. 57, that extrinsic evidence does not outweigh the in-
trinsic record. See Finisar Corp. v. DirecTV Grp., Inc.,
523 F.3d 1323, 1328 (Fed. Cir. 2008) (“When construing
claims, the claims and the rest of the patent, along with the
patent’s prosecution history . . . are the primary resources;
while helpful, extrinsic sources like dictionaries and expert
testimony cannot overcome more persuasive intrinsic evi-
dence.”). We thus affirm the Board’s construction.
                             III
    Finally, we address Arthrex’s challenge to the consti-
tutionality of certain IPRs. Arthrex notes that the Su-
preme Court has not addressed the constitutionality of IPR
as applied to patents issued prior to the America Invents
Act (AIA), which created IPRs. See Oil States Energy
Servs., LLC v. Greene’s Energy Grp., LLC, 138 S. Ct. 1365,
1379 (2018) (“Oil States does not challenge the retroactive
application of inter partes review, even though that proce-
dure was not in place when its patent issued.”). It asks us
to hold that IPR is unconstitutional when applied retroac-
tively to pre-AIA patents. 2 See Appellant’s Br. 62.
     We exercise our discretion and reach Arthrex’s argu-
ment rather than finding that Arthrex waived this issue by
failing to present it to the Board. See e.g., In re DBC,
545 F.3d 1373, 1378–79 (Fed. Cir. 2008) (noting “discretion
to reach issues raised for the first time on appeal” but hold-
ing party waived constitutional challenge based on Ap-
pointments Clause by failing to raise it before the Board);
Harris Corp. v. Ericsson Inc., 417 F.3d 1241, 1251



    2   To the extent Arthrex intends to raise a general
due process challenge unrelated to retroactivity, the single
paragraph of conclusory assertions presented in its open-
ing brief is “insufficient to preserve the issue for appeal.”
See Trading Techs. Int’l, Inc. v. IBG LLC, 921 F.3d 1378,
1385 (Fed. Cir. 2019).
18                     ARTHREX, INC. v. SMITH & NEPHEW, INC.




(Fed. Cir. 2005) (“An appellate court retains case-by-case
discretion over whether to apply waiver.”). We need not
reach the merits of the issue, however, because the ’541 pa-
tent issued on September 2, 2014, almost three years after
passage of the AIA and almost two years after the first IPR
proceedings began. See Leahy-Smith America Invents Act,
Pub. L. No. 112-29, § 6(c)(2)(A), 125 Stat. 284, 304 (2011)
(providing that IPR “shall take effect upon the expiration
of the 1-year period beginning on the date of the enactment
of this Act [Sept. 16, 2011]”). That Arthrex filed its patent
applications prior to passage of the AIA is immaterial. As
the Supreme Court has explained, “the legal regime gov-
erning a particular patent ‘depend[s] on the law as it stood
at the emanation of the patent, together with such changes
as have since been made.’” Eldred v. Ashcroft, 537 U.S.
186, 203 (2003) (quoting McClurg v. Kingsland, 42 U.S.
202, 206 (1843)). Accordingly, application of IPR to Ar-
threx’s patent cannot be characterized as retroactive.
     In any event, even if Arthrex’s patent had issued prior
to the passage of the AIA, our court recently rejected argu-
ments similar to Arthrex’s in Celgene Corp. v. Peter.
No. 18-1167, 2019 WL 3418549, at *12–16 (Fed. Cir.
July 30, 2019). As we explained, pre-AIA patents issued
subject to both district court and Patent Office validity pro-
ceedings. Though IPR differs from these existing proceed-
ings, we held that the differences between IPRs and the
district court and Patent Office proceedings that existed
prior to the AIA are not so significant as to “create a con-
stitutional issue” when IPR is applied to pre-AIA patents.
Id. at *15; see also id. at *12 & n.13 (affirming that our
prior decisions ruling that retroactive application of reex-
amination does not violate the Fifth Amendment, the Sev-
enth Amendment, or Article III “control the outcome” of
similar challenges to IPR). When Arthrex’s patent issued,
it is beyond dispute that patent owners expected that “the
[Patent Office] could reconsider the validity of issued pa-
tents on particular grounds, applying a preponderance of
ARTHREX, INC. v. SMITH & NEPHEW, INC.                    19



the evidence standard.” Id. at *16. Consequently, even if
Arthrex’s patent pre-dated the AIA, application of IPR to
the ’541 patent would not create a constitutional challenge.
                       CONCLUSION
   We have reviewed the parties’ remaining arguments
and find them unpersuasive. We therefore affirm the
Board.
                       AFFIRMED
