periprosthetic fracture fixation of the femur following...
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Clinical Biomechanics
journal homepage: www.elsevier.com/locate/clinbiomech
Review
Periprosthetic fracture fixation of the femur following total hip arthroplasty:A review of biomechanical testing – Part IIKatherine Wanga, Eustathios Kenanidisa,b, Mark Miodownika, Eleftherios Tsiridisb,Mehran Moazena,⁎
a Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, UKbAcademic Orthopaedics Department, Papageorgiou General Hospital & CORE Lab at CIRI AUTH, Aristotle University Medical School, University Campus 54 124,Thessaloniki, Greece
A R T I C L E I N F O
Keywords:Periprosthetic femoral fractureBiomechanicsComputational modelFixation method
A B S T R A C T
Background: Periprosthetic femoral fracture is a severe complication of total hip arthroplasty. A previous reviewpublished in 2011 summarised the biomechanical studies regarding periprosthetic femoral fracture and itsfixation techniques. Since then, there have been several commercially available fracture plates designed spe-cifically for the treatment of these fractures. However, several clinical studies still report failure of fixationtreatments used for these fractures.Methods: The current literature on biomechanical models of periprosthetic femoral fracture fixation since 2010to present is reviewed. The methodologies involved in the experimental and computational studies of peri-prosthetic femoral fracture fixation are described and compared with particular focus on the recent develop-ments.Findings: Several issues raised in the previous review paper have been addressed by current studies; such asvalidating computational results with experimental data. Current experimental studies are more sophisticated indesign. Computational studies have been useful in studying fixation methods or conditions (such as bonehealing) that are difficult to study in vivo or in vitro. However, a few issues still remain and are highlighted.Interpretation: The increased use of computational studies in investigating periprosthetic femoral fracture fixa-tion techniques has proven valuable. Existing protocols for testing periprosthetic femoral fracture fixation needto be standardised in order to make more direct and conclusive comparisons between studies. A consensus on the‘optimum’ treatment method for periprosthetic femoral fracture fixation needs to be achieved.
1. Introduction
Periprosthetic femoral fractures (PFF) is a severe complication fol-lowing total hip arthroplasty (THA); the rate of intraoperative PFFranged from 0.1–27.8% and of postoperative from 0.07–18%. PFF aremore frequent in uncemented than cemented both in primary and re-vision THA (e.g. Biggi et al., 2010; Dubov et al., 2011; Fleischman andChen, 2015; Kenanidis et al., 2018). PFF account for approximately 6%of revision cases and are the third most common reason for revisionsurgery after aseptic loosing and infection (e.g. Lewallen and Berry,1998; Lindahl et al., 2006; Marsland and Mears, 2012). This number isexpected to rise substantially by 2030, with the increase in life ex-pectancy of the general population also leading to a rising incidence oftotal hip arthroplasties (THAs), with PFF also expected to rise pro-portionally (Della Valle et al., 2010).
PFF can occur intra-operatively or post-operatively, creating avariety of different fracture configurations at different locations; manyresearchers classify PFF based on fracture type, position on the femur,and bone quality. The Vancouver classification system is the mostwidely used and accepted classification system for PFF (Duncan andMasri, 1995; Learmonth, 2004; Moazen et al., 2011). Fractures classi-fied as Type A are fractures involving the trochanteric area. The ma-jority (approximately 75%, − Lochab et al., 2017; Lever et al., 2010) ofPFF, however, are Type B; located around and just distal to the tip ofthe stem, and are subdivided as B1 with the stem stable and good bonestock, B2 with the stem unstable and good bone stock, and B3 with stemunstable and significant bone loss. Type C are fractures located distal tothe stem (Capone et al., 2017; Leonidou et al., 2013; Tsiridis et al.,2009).
These fractures can be challenging to manage and treat, and are
https://doi.org/10.1016/j.clinbiomech.2018.12.001Received 31 August 2018; Accepted 4 December 2018
⁎ Corresponding author at: Department of Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE, UKE-mail address: [email protected] (M. Moazen).
Clinical Biomechanics 61 (2019) 144–162
0268-0033/ © 2018 Elsevier Ltd. All rights reserved.
T
most commonly found in osteopenic elderly women, or in patients whohave experienced loosening of the femoral stem following low energytrauma (Kenanidis et al., 2018; Shah et al., 2011). Given the complexnature of PFF treatment, due to the combination of the fractured boneand existing prosthesis (Moazen et al., 2011), many factors are requiredto be taken into consideration in the treatment of PFF; e.g., sex, age,bone quality, fracture topography, previous hip revision procedures,implant stability, and types (e.g. cemented vs. uncemented stem - DellaValle et al., 2010). The Unified Classification System (UCS); a recentlyproposed treatment algorithm developed by Duncan and Haddad(Duncan and Haddad, 2014), outlines the principles of PFF treatment.Treatment for Type A fractures is dependent on two factors; fracturedisplacement and the importance of soft tissue attached. Non-displacedType A fractures are typically non-operative and treated conservatively.In cases of displacement of the greater trochanter, surgical treatmenttypically uses cerclage wires or hook cable plates for fixation. In cases ofthe lesser trochanter, if the fracture compromises the stability of theimplant, cerclage wiring and implant revision may be considered (Biggiet al., 2010; Schwarzkopf et al., 2013). Management of Type B fracturesis determined by subtype. B1 fractures can be treated by reduction andfixation using minimally invasive plate osteosynthesis (MIPO). In B2fractures, revision surgery with a longer stem is commonly used. B3fractures require more complex reconstruction or salvage procedures(megaprosthesis, allograft/stem composite). Type C fractures can betreated as a non-periprosthetic fracture. Specialized techniques can beused in some cases if hardware required for fixation will extend towardsthe implant, such as cerclages and unicortical screws (Capone et al.,2017; Duncan and Haddad, 2014).
While the Vancouver classification determine the treatment for PFF,many clinical cases still report failure of femoral fracture fixation due tomismanagement; the misclassification of B1 and B2 fractures is themain reason for the greater reported failure of B fractures (Kenanidiset al., 2018). For example, up to 20% of loose stems are missed onpreoperative radiologic evaluation; many surgeons also fail to ade-quately test stem stability in the operating room leading to in-appropriate selection of surgical methods for treatment (Fleischmanand Chen, 2015; Niikura et al., 2014). This suggests that protocol forclassifying PFF and subsequent fixation method is still insufficient. In-deed the reliability of any classification system depends on inter-ob-server and intra-observer consistency (Rayan et al., 2008). Optimalmanagement of PFF remains controversial and debated, given thatadequate fixation needs to be achieved without compromising thestability of the hip prosthesis. Although PFF is a rare complication,understanding risk factors and optimum treatment for fixation is still ofhigh importance, as one study documented a higher risk of death afterPFF compared with a similar population of patients undergoing un-complicated THA (Della Rocca et al., 2011; Lindahl et al., 2007).
Finite element (FE) analysis is a computational modelling techniquethat allows prediction of the mechanical behaviour of structures. Usedfor orthopaedic biomechanics since the early 1970's it has been in-creasingly utilized by a number of authors to study structural-me-chanical problems such as stress and strain analysis of bone, joints, andload-bearing implants (Huiskes and Chao, 1983; Kluess et al., 2010).Computer modelling allows a large number of scenarios to be testedwith little extra cost per test making it advantageous over traditionalexperimental studies. To optimise management of PFF fixation, therehave been a number of computational studies dedicated to simulatingtheir biomechanics.
In 2011, Moazen et al. summarised the biomechanical research in-vestigating PFF fixation following THA and its treatment methods.However, since then, there has been a large influx of biomechanical andcomputational studies carried out, and this is the basis of this paper.The aim of this paper was to provide an updated review of currentresearch relating to PFF following THA published since 2011; currently,available literature pertinent to the biomechanical analysis of PFFtreatment methods will be examined. Results of the experimental and
computational studies conducted from 2010 to present and their trendswere evaluated. Results from this review were critically compared toprevious studies, highlighting any evolutions in biomechanical analysisof treatment methods for PFF.
2. Methodology
Computerised scientific journal databases, i.e. Scopus, GoogleScholar, PubMed, and Web of Science were searched with the followingkeywords: Biomechanical testing, analysis, Finite element analysis,computational modelling, periprosthetic femoral fractures, and totalhip arthroplasty. All studies from the above-mentioned searches werethen reviewed; studies were included if they met the following criteria:(1) English Language; (2) Biomechanical or computational studies ofPFF after THA (3) femoral fractures. Additionally, all studies prior to2010 were excluded as they were reviewed previously (Moazen et al.,2011). In total 39 articles were retrieved, with 30 experimental studiesand 9 computational studies. In order to maintain linearity and con-tinuation, this paper will follow the same format as the previous review.
2.1. Experimental methods
A total of 30 experimental studies were reviewed. In many of thepresent experimental studies, the basic methodology described byMoazen et al. (2011) remained the same. The previous paper high-lighted three specific aspects in the experimental methodologies; typeof specimen, loading protocol, and methods of measurement. Meth-odologies in respect to those three aspects typically remained the same,and in-depth details of these can be referred back to the previous re-view. For most of the studies, mechanical performance is compared bystabilizing a periprosthetic fracture in both a cadaveric or syntheticfemur, and different loading protocols are applied to the construct (seeTable 1).
2.1.1. Specimen type and repeatabilityDespite basic methodology remaining the same, several noteworthy
factors have emerged from the reviewed studies; in particular, currentstudies using cadaveric femora use a higher number of specimenscompared to previous studies; where typical sample size ranged from 5to 16 cadaveric specimens, compared to a sample size range of 10 [5pairs – (Konstantinidis et al., 2010)] to 24 (Lehmann et al., 2010; Lenzet al., 2014) cadaveric specimens. One exception to this is Lenz et al.(2013) who used 45 cadaveric 70 mm segments of femora. In somestudies, authors used the same femur to test different fracture scenarios;Ebrahimi et al. (2012) utilized a single synthetic femur to test experi-mentally and computationally model and mimic the same femur whileintact, after injury, repair, and healing. While most studies used bonemineral density matched cadaveric femora, to ensure no lesions or pre-existing fracture, Lehmann et al. (2010) used an osteoporotic bonemodel, to represent the group with the highest incidence of PFF. Whilemost cadaveric bones used were fresh frozen, two studies used em-balmed femora (Demos et al., 2012; Konstantinidis et al., 2010).
2.1.2. Representation of loads and surrounding conditionsIn respect to loading modes and surrounding conditions, higher
loading modes have been used by several authors. In previous studies(Moazen et al., 2011), only 500 N could be seen used repeatedly fornon-destructive monotonic tests; in present studies, loads of 700 N(Choi et al., 2010; Graham et al., 2015) to 2500 N (Pletka et al., 2011)have been used. A loading mode not seen in previous papers is four-point bending (Lenz et al., 2016a, 2016b; Lever et al., 2010; Lochabet al., 2017) and in one case three-point bending (Choi et al., 2010);examples of these can be seen in Fig. 1. The basic experimental setupseen in most of the experimental studies can be referred back to theprevious review (Moazen et al., 2011). There is little consensus seen onloading protocols; loads to failure was also not consistent across the
K. Wang et al. Clinical Biomechanics 61 (2019) 144–162
145
Table1
Asu
mm
ary
ofth
esp
ecim
enpr
epar
atio
nan
dlo
adin
gpr
otoc
olin
labo
rato
ryst
udie
s.
Aut
hors
Spec
imen
num
ber
and
type
Pros
thes
isFr
actu
reLo
adin
gFe
mur
posi
tion
(Leh
man
net
al.,
2010
)24
Cada
veri
c(6
per
grou
p)b
Cem
ente
d,Ex
eter
,Str
yker
How
med
ica
Ost
eoni
csO
bliq
ue45
°ost
eoto
my,
leve
latt
ipof
hip
stem
(onl
yfo
rgr
oup
IV).
Four
-poi
ntbe
ndin
g–
load
appl
ied
at0.
1m
m/s
until
frac
ture
.H
oriz
onta
lpos
ition
.
(Lev
eret
al.,
2010
)12
mat
ched
pair
sCa
dave
ric
(5te
stm
odes
,15
test
case
s.)b
Cem
ente
d,(C
ompa
nyno
tm
entio
ned)
Obl
ique
45°o
steo
tom
yA
xial
com
pres
sion
–lo
adof
250
Nap
plie
d(t
wo
type
stes
ted
–ab
duct
ion,
and
forw
ard
flexi
on)
Tors
ion
–25
0N
appl
ied
toan
teri
oras
pect
offe
mor
alhe
adFo
ur-p
oint
bend
ing
(2ty
pes
test
ed-a
nter
o-po
ster
ior
and
med
io-la
tera
lfor
ces)
–25
0N
appl
ied
sym
met
rica
llyon
eith
ersi
deof
oste
otom
ysi
te.
Axi
al-2
0°of
abdu
ctio
n,an
d20
°for
war
dfle
xion
Tors
ion
and
4-po
intb
endi
ng–
Hor
izon
talo
rien
tatio
nto
sim
ulat
e90
°offl
exio
n(C
hoie
tal
.,20
10)
10Sy
nthe
ticCe
men
ted,
Zim
mer
,War
saw
,IN
Tran
sver
seos
teot
omy,
20m
mfr
actu
rega
pdi
stal
totip
ofst
em.
Sinu
soid
alax
iall
oadi
ngof
50–7
00N
for
100
cycl
esat
2H
z.
Thre
e-po
int
bend
ing
–Ve
rtic
alsi
nuso
idal
load
sof
50N
–50
0N
at2
Hz
for
300
cycl
es.
Tors
ion
–in
crea
sing
sinu
soid
alto
rsio
nalm
ovem
ents
3N
/m–
12N
/map
plie
dat
0.5
Hz
for
20cy
cles
.
All
test
sre
peat
edth
ree
times
for
each
cons
truc
tm
odel
.
25°o
fadd
uctio
n
(Kon
stan
tinid
iset
al.,
2010
)5
pair
sCa
dave
ricc
Cem
ente
d,Bi
cont
act,
Aes
cula
p,Tu
ttlin
gen,
Ger
man
yTr
ansv
erse
,10
mm
frac
ture
gap
dist
alto
stem
tip.
Axi
alan
dcy
clic
com
pres
sion
–10
00N
for
10,0
00cy
cles
,th
enpr
ogre
ssiv
ely
load
edto
failu
reat
100
N/2
000
cycl
es.
9°of
addu
ctio
n
(Ple
tka
etal
.,20
11)
9m
atch
edpa
irs
Cada
veri
cbCe
men
ted,
Ulti
ma,
DeP
uy,W
arsa
w,
INTr
ansv
erse
.10
mm
dist
alto
stem
tip.
Sinu
soid
alcy
clic
load
ing
–up
to10
,000
cycl
esfr
om0
to25
00N
axia
lfor
ce.
0-15
Nm
ofto
rsio
nat
rate
of1
Hz.
Vert
ical
orie
ntat
iona
(Sha
het
al.,
2011
)3
Synt
hetic
Cem
ente
d,Ki
ngPa
ckag
edM
ater
ials
Co.,
ON
,Can
ada
Tran
sver
seat
tipof
stem
–5
mm
frac
ture
gap
near
tipof
stem
Dis
plac
emen
tcon
trol
,max
imum
vert
ical
load
of10
00N
axia
lfor
ceat
rate
of5
mm
/min
appl
ied.
15°o
fadd
uctio
n
(Dem
oset
al.,
2012
)24
Cada
veri
c(6
per
grou
p)c
Cem
ente
d,10
0m
mst
raig
htm
etal
carr
iage
bolt
used
inst
ead
ofhi
pst
em.
Obl
ique
45°,
20m
mfr
actu
rega
pdi
stal
tohi
pst
emA
xial
com
pres
sion
tofa
ilure
at5
mm
/s.
Vert
ical
orie
ntat
ion,
fem
oral
shaf
tco
lline
arto
axis
oflo
adin
ga
(Len
zet
al.,
2012
a)12
Cada
veri
cbCe
men
ted,
Char
nley
hip
endo
pros
thes
is,D
ePuy
IN45
°-10
mm
dist
alto
tipof
pros
thes
is.
Cycl
icA
xial
bend
ing
at2
Hz
with
sync
hron
alsi
nuso
idal
axia
lloa
ding
at95
0N
for
10,0
00cy
cles
–A
xial
forc
esra
nged
from
50N
-100
0N
.Afte
r10
,000
cycl
es,i
ncre
ased
load
atra
teof
0.1
N/C
ycle
until
cata
stro
phic
failu
rest
artin
gfr
om10
00N
.
12°V
algu
s
(Len
zet
al.,
2012
b)8
Synt
hetic
(2gr
oups
)U
ncem
ente
d,M
athy
s,Be
ttla
ch,
Switz
erla
nd.
90°t
rans
vers
eos
teot
omy,
5m
mdi
stal
totip
ofst
em.
Cycl
icte
stin
gat
3H
zat
cons
tant
ampl
itude
of18
00N
for
first
5000
cycl
es.
Mon
oton
ical
lyin
crea
sing
sinu
soid
allo
adat
rate
of60
mN
/cy
cle
until
failu
rest
artin
gfr
om20
00N
20°V
algu
s
(Ebr
ahim
ieta
l.,20
12)
1Sy
nthe
ticCe
men
ted,
Exet
er,S
tryk
er,N
J,U
SATr
ansv
erse
5m
mga
p,23
3m
mfr
omto
pof
cem
ent
pott
ing
cube
.A
xial
load
,at
max
imum
of15
00N
,at
rate
of10
0N
/s15
°ofa
dduc
tion
(Len
zet
al.,
2013
)45
Cada
veri
c(s
egm
ents
-5pe
rgr
oup)
bN
opr
osth
esis
Non
e-70
mm
leng
thfr
agm
ents
cut
from
the
diap
hysi
sof
the
fem
urw
ere
used
Axi
allo
adto
failu
reat
rate
of50
N/s
Tors
iona
ltes
ting
atra
teif
2.5
Nm
/sun
tilco
nstr
uctf
ailu
re.
Axi
al–
Vert
ical
orie
ntat
ion
Tors
iona
l–H
oriz
onta
lor
ient
atio
n.(W
ähne
rtet
al.,
2014
)9
pair
s,m
atch
edCa
dave
ric.
(9pe
rgr
oup)
b
Unc
emen
ted,
Allo
clas
sic,
Zim
mer
,Sw
itzer
land
.Pr
oxim
alho
rizo
ntal
cut
and
45°d
ista
lcut
5m
mbe
low
stem
tip.
Cycl
icsi
nuso
idal
axia
lloa
ding
star
ting
at75
0N
,inc
reas
edat
0.1
N/c
ycle
at2
Hz
until
cons
truc
tfa
ilure
.Ve
rtic
alor
ient
atio
na
(Gie
sing
eret
al.,
2014
)17
Synt
hetic
(2gr
oups
,9
inN
CBgr
oup
and
8in
cont
rol)
Cem
ente
d,CP
T,Zi
mm
er,I
NO
steo
tom
y20
mm
dist
alto
tipof
stem
,6m
mga
pne
arst
emtip
.A
xial
load
of10
0-40
0N
and
tors
iona
lloa
dof
1-4
Nm
appl
ied
at1.
5H
zfo
r20
,000
cycl
es-o
steo
tom
yga
pth
enfil
led
with
cem
entt
osi
mul
ate
‘hea
led’
frac
ture
.The
nA
xial
load
of10
0-14
00N
and
1–10
.8N
mto
rsio
nall
oad
appl
ied
for
80,0
00cy
cles
7°Va
lgus
(Bra
ndet
al.,
2014
)8
Synt
hetic
Cem
ente
d,Ec
ofit,
Impl
antc
ast,
Buxt
ehud
e,G
erm
any.
15m
mbe
low
tipof
stem
Axi
allo
adto
failu
re–
cons
tant
incr
easi
nglo
adap
plie
dw
itha
star
ting
forc
eof
0N
6°Va
lgus
(Len
zet
al.,
2014
)24
mat
ched
,Cad
aver
icb
Cem
ente
d,Ch
arnl
ey,D
ePuy
,IN
Valg
us
(continuedon
nextpage
)
K. Wang et al. Clinical Biomechanics 61 (2019) 144–162
146
Table1
(continued)
Aut
hors
Spec
imen
num
ber
and
type
Pros
thes
isFr
actu
reLo
adin
gFe
mur
posi
tion
60°-
10m
mfr
omst
emtip
–D
ista
lpor
tion
offe
mur
and
plat
eem
bedd
edin
PMM
A.
Axi
albe
ndin
g–
50N
to20
0N
atra
teof
30N
/s.
Cycl
icte
stin
gat
rate
of2
Hz,
sync
hron
alax
iall
oadi
ngw
ithco
nsta
ntva
lley
load
of20
0N
.10
00N
peak
load
leve
linc
reas
edat
rate
of0.
1N
/cyc
leun
tilca
tast
roph
icfa
ilure
(Hoff
man
net
al.,
2014
)15
med
ium
Synt
hetic
(5fo
rea
chte
st)
Unc
emen
ted
VerS
ys,Z
imm
er,I
NO
bliq
ue45
°to
shaf
taxi
sat
the
leve
lofi
mpl
antt
ip.
Axi
alco
mpr
essi
on-l
oade
dto
500
Nat
20N
/s
Late
ralB
endi
ng–
load
edto
250
Nat
10N
/s
Tors
ion/
Sagi
ttal
bend
ing
–lo
aded
to20
0N
at10
N/s
Axi
alcy
clic
load
ing
–50
-500
Nlo
adap
plie
dat
3H
zfo
r10
,000
cycl
es.A
fter
cycl
iclo
adin
gfe
mur
ste
sted
agai
nfo
ral
lthr
eem
odal
ities
then
load
edto
failu
reor
100
mm
disp
lace
men
tin
tors
iona
l/sa
gitt
albe
ndin
g
10°a
dduc
tion
infr
onta
lpla
ne.
Vert
ical
lyin
sagi
ttal
plan
e.
(Sar
iyilm
azet
al.,
2014
)15
larg
e,le
ftSy
nthe
tic(5
for
each
test
)U
ncem
ente
d,Sy
nerg
y,Sm
ith&
Nep
hew
,TN
10m
mfr
actu
rega
pat
leve
lofp
rost
hesi
stip
–(t
rans
vers
e)Cy
clic
rota
tiona
lloa
ding
10re
peat
edcy
lindr
ical
twis
tsat
3H
zbe
twee
n0.
5an
d10
Nm
for
10,0
00cy
cles
Cycl
icax
iall
oadi
ng–
forc
eco
ntro
l-50
N-5
00N
for
1000
cycl
elo
adin
gs,w
ith10
repe
titio
nsat
a3-
Hz.
Axi
alFa
ilure
–di
spla
cem
ent
cont
rol–
forc
eap
plie
dw
ithsp
eed
of15
mm
/min
until
failu
re.
15°V
algu
sfo
rcy
clic
axia
llo
adin
g.
(Gri
ffith
set
al.,
2015
)12
larg
e,le
ft,sy
nthe
tic(6
for
each
test
)Ce
men
ted,
Exet
erfe
mor
alst
em45
°obl
ique
-25
mm
dist
alto
tipof
stem
,one
grou
pha
dm
idsh
aft
oste
otom
y(M
O)
(ana
tom
ical
lyre
duce
d)an
dth
eot
her
mid
shaf
tga
p(M
G)
(with
5m
mga
p)
Axi
alco
mpr
essi
on,d
ispl
acem
entc
ontr
ol–
prel
oade
d10
0N
to10
00N
,ver
tical
load
appl
ied
-500
Nfo
rM
O,2
50N
for
MG
.La
tera
lben
ding
–20
0N
vert
ical
load
at8
mm
/min
Tors
iona
lstiff
ness
–ve
rtic
allo
adof
200
Nat
8m
m/m
inA
xial
load
tofa
ilure
–pr
eloa
dof
100
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load
rate
of8
mm
/min
tillc
atas
trop
hic
failu
re
Axi
al-2
5°ad
duct
ion
toco
rona
lpl
ane,
alig
ned
vert
ical
lyin
sagi
ttal
plan
e.La
teri
al–
hori
zont
alTo
rsio
nal-
Hor
izon
tal
(Gra
ham
etal
.,20
15)
5sy
nthe
ticCe
men
ted,
Exet
er,S
tryk
erSA
,Sw
itzer
land
.4
fixed
asif
anat
omic
ally
redu
ced.
1w
ith10
mm
gap
Axi
allo
ad–
disp
lace
men
tcon
trol
5m
m/m
in,m
ax50
0N
0°,1
0°,a
nd20
°add
uctio
nfo
rno
gap
mod
el.
10°f
orga
pm
odel
(Gw
inne
ret
al.,
2015
)20
larg
e,le
ft,sy
nthe
ticU
ncem
ente
d,A
llocl
assi
c,Zi
mm
er,
Switz
erla
nd.
Tran
sver
secu
tand
45°d
ista
lcut
atle
velo
fim
plan
ttip
.With
10m
mga
p.Cy
clic
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soid
alax
iall
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ngst
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gat
30N
.Inc
reas
edby
300
Nev
ery
1000
cycl
es.
Vert
ical
orie
ntat
iona .
(Lew
iset
al.,
2015
)30
Synt
hetic
Cem
ente
d,Zi
mm
er,W
arsa
w,I
NTr
ansv
erse
,25
mm
dist
alto
pros
thes
istip
.Dis
tal
part
offe
mur
not
used
tosi
mul
ate
segm
enta
lbon
elo
ss.
Tors
iona
lint
erna
lrot
atio
n.20
prec
ondi
tioni
ngcy
cles
at10
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/1H
z.Th
enlo
adin
gra
teof
8m
m/m
inun
tilfa
ilure
.A
xial
load
ing
–Ph
ase
I:lo
adof
4m
m/m
inun
til12
00N
.Ph
ase
II:4
mm
/min
until
failu
re/7
500
N.
Tors
iona
l-11
°ofp
rost
hesi
san
teve
rsio
n.A
xial
-13°
addu
ctio
n
(Fri
sch
etal
.,20
15)
24sy
nthe
ticU
ncem
ente
d,Zi
mm
er,W
arsa
w,I
NFe
mor
alne
ckos
teot
omy
10m
mpr
oxim
alto
less
ertr
ocha
nter
.Lo
ngitu
dina
lfra
ctur
eex
tend
ing
127
mm
dist
ally
Axi
allo
adof
50N
pre-
load
follo
wed
bylo
adin
gra
teof
0.8
mm
/min
and
term
inat
edaf
ter
disp
lace
men
tof2
0m
m.
Tors
ion
–ro
tatio
nald
ispl
acem
ents
appl
ied
atra
teof
2.4°
/s,
rota
ted
thro
ugh
40°u
ntil
failu
re.
25°a
dduc
tion,
0°an
teve
rsio
n
(Len
zet
al.,
2016
a)12
cada
veri
c,pa
ired
,(6
for
each
test
)bCe
men
ted,
Char
nley
,DeP
uy,I
N10
mm
dist
alto
tipof
pros
thes
is.–
orth
ogon
alto
shaf
tax
isof
fem
ur.
Axi
allo
adin
gan
ddi
spla
cem
enta
t10
Hz
4-po
int
bend
ing
and
tors
ion
test
edw
ithdi
spla
cem
ent
cont
rola
t0.
5m
m/m
in.U
pto
250
Nap
plie
d.
Cycl
icte
stin
gto
failu
rew
ithax
ialc
ompr
essi
onfr
om50
Nto
load
plat
eau
of20
0N
at30
N/s
,inc
reas
edpe
aklo
adat
500
Nat
0.1
N/c
ycle
.
Cycl
icte
stin
g-1
2°va
lgus
and
12°a
ntev
ersi
on
(Moa
zen
etal
.,20
16)
12la
rge,
left
synt
hetic
Cem
ente
d,Zi
mm
er,S
ulze
r,Sw
itzer
land
20m
mbe
low
tipof
stem
.A
xial
load
ing
–up
to70
0N
10°a
dduc
tion
(Gor
don
etal
.,20
16)
20sy
nthe
tic(5
for
each
test
)1.
Unc
emen
ted,
shor
tst
em(1
0),
Ana
Nov
aSo
litär
,Im
plan
Tec,
Aus
tria
140
mm
spir
alfr
actu
re(1
00m
mpr
oxim
alto
40m
mdi
stal
ofst
em)
Sinu
soid
alcy
clic
load
ing
-50
N-5
00N
at2
Hz
Axi
alSt
iffne
ss–
stro
keco
ntro
lled
0.02
mm
/sup
to50
0N
6°ad
duct
ion
(continuedon
nextpage
)
K. Wang et al. Clinical Biomechanics 61 (2019) 144–162
147
Table1
(continued)
Aut
hors
Spec
imen
num
ber
and
type
Pros
thes
isFr
actu
reLo
adin
gFe
mur
posi
tion
2.U
ncem
ente
d,lo
ngre
visi
onst
em(1
0),M
odul
arPl
us,S
mith
and
Nep
hew
,Aus
tria
Cycl
icsi
nuso
idal
fatig
uelo
adin
g-20
00N
max
load
,in
crea
sing
by15
0N
/500
cycl
esun
tilfa
ilure
(Len
zet
al.,
2016
b)12
cada
veri
c,pa
ired
,(6
for
each
grou
p)b
Cem
ente
d,Ch
arnl
ey,D
ePuy
,IN
Tran
sver
se,
10m
mdi
stal
totip
ofst
em,o
rtho
gona
lto
fem
ursh
aft
axis
Axi
albe
ndin
gto
200
Nat
30N
/sCy
clic
mec
hani
calt
estin
gat
2H
zw
ithsy
nchr
onic
axia
llo
adin
gin
crea
sed
at0.
1N
/cyc
lest
artin
gfr
om50
0N
until
cata
stro
phic
failu
re.
4-po
int
bend
ing
–25
0N
max
12°v
algu
san
d12
°ant
ever
sion
(Wal
cher
etal
.,20
16)
38sy
nthe
ticCe
men
ted,
Web
erst
anda
rdst
raig
htst
em,Z
imm
er.
Non
eto
sim
ulat
ehe
aled
peri
pros
thet
icfr
actu
resi
tuat
ion.
Axi
alco
mpr
essi
onat
500
Nov
er5
s.Th
en30
cycl
esfr
om40
0N
–150
0N
at0.
25H
zap
plie
d.To
rsio
nalt
estin
gto
0.6
Nm
over
5s,
then
30cy
cles
ofex
tern
alro
tatio
nfr
om0.
6N
m–5
0N
mat
0.25
Hz.
Load
tofa
ilure
atco
nsta
ntdi
spla
cem
entr
ate
of10
0m
m/
min
inax
iall
oadi
ng.
7°va
lgus
(Wäh
nert
etal
.,20
17)
10Sy
nthe
tic(5
for
each
grou
p)U
ncem
ente
d,A
llocl
assi
c,Zi
mm
erG
mbH
,Sw
itzer
land
.45
°dis
talc
utan
dho
rizo
ntal
cut5
mm
dist
alto
stem
tip.
Cycl
iclo
adin
gin
axia
lcom
pres
sion
at2
Hz
until
failu
re–
star
ting
atpe
aklo
adof
750
Nw
ithin
crem
ento
f0.1
N/
cycl
e.
Vert
ical
orie
ntat
iona
(Kon
stan
tinid
iset
al.,
2017
)20
cada
veri
cCe
men
ted,
Bico
ntac
t,A
escu
lap
AG
,G
erm
any.
Tran
sver
sebe
low
tipof
stem
.Fl
uctu
atin
gax
iall
oad
(sin
usoi
dalp
rofil
e,0.
5H
z,21
00N
)ap
plie
dto
pros
thet
icco
ne,r
epea
ted
for
20,0
00lo
adcy
cles
.St
anda
rdad
duct
ion
posi
tion
(Loc
hab
etal
.,20
17)
9pa
irs
ofca
dave
ricb
Cem
ente
d,D
ePuy
Sum
mit,
DeP
uySy
nthe
s,W
arsa
w,I
N.
45°o
bliq
ueos
teot
omy
25m
mdi
stal
totip
ofst
em.
5m
mfr
actu
rega
p4-
poin
tben
ding
–ra
teof
8m
m/m
inw
ithlo
adup
to25
0N
Tors
ion
and
Axi
alco
mpr
essi
on–
vert
ical
forc
eof
250
NA
xial
com
pres
sion
tofa
ilure
orup
tom
axim
umve
rtic
aldi
spla
cem
ent
of10
mm
.
20°a
bduc
tion
and
20°fl
exio
n
aA
utho
rdi
dn't
spec
ifyfe
mor
alpo
sitio
n,bu
tfr
omth
eim
ages
prov
ided
,we
belie
vest
anda
rdad
duct
ion
vert
ical
posi
tioni
ngw
asus
ed.
bFr
esh
froz
enca
dave
ric.
cFo
rmal
infix
edca
dave
ric
fem
ora.
K. Wang et al. Clinical Biomechanics 61 (2019) 144–162
148
studies, an issue that was raised previously. Boundary conditions,magnitudes, and direction of loads applied varied between authors,seen in Table 1.
The majority of studies reviewed here studied the biomechanicalperformance of typical variations of an Ogden construct; specificallyexamining the performance of the plate fixation and its fixation methodto the femur via screws, cables, wires or in some cases struts. However,several new trends and parameters may affect the outcome of thefixation method examined across the studies published that was notinvestigated previously; including fracture gap, type of plate used, and
screws and cement mantle integrity. These will be described below withan overview of the materials and methods, and updated parametersused in the studies.
2.2. Overview of recent developments
2.2.1. Fracture configurationMost studies simulated a Vancouver B1 type fracture in their stu-
dies. Introduction of an osteotomy to simulate PFF was most commonlygenerated using a saw; although fracture position and configuration
Fig. 1. Schematic diagram of different examples of loading methods used in tests.A) 4-point bending (Medio-lateral) (Lever et al., 2010).B) 3-point bending (Choi et al., 2010).C-D) The embedded femoral shaft bone was connected to the actuator of the testing machine via a xy-table. Setup for axial loading (C) and lateral torsional loading(D) shown. (Lenz et al., 2013).E) Test set up of specimen positioned in 12° valgus for cyclic testing. Distal part of femur is potted in PMMA cement (Lenz et al., 2012a).
Fig. 2. Schematic diagram of different fracture gapvariations used in experimental methods.A) Fracture Gap (Choi et al., 2010; Giesinger et al.,2014; Graham et al., 2015; Griffiths et al., 2015;Gwinner et al., 2015; Konstantinidis et al., 2010;Lochab et al., 2017; Sariyilmaz et al., 2014; Shahet al., 2011).B) No gap (Brand et al., 2014; Frisch et al., 2015;Griffiths et al., 2015; Hoffmann et al., 2014;Konstantinidis et al., 2017; Lehmann et al., 2010;Lenz et al., 2012a, 2012b, 2016a; Lever et al., 2010;Pletka et al., 2011).C) Fracture gap filled with cement (Giesinger et al.,2014).D) Fracture gap with a wedge-like cut (Gwinneret al., 2015; Wähnert et al., 2014, 2017).
K. Wang et al. Clinical Biomechanics 61 (2019) 144–162
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varies between the studies (Table 1). In many studies, no fracture gapwas left after the osteotomy, in order to simulate a stable fracturepattern (Brand et al., 2014; Frisch et al., 2015; Griffiths et al., 2015;Hoffmann et al., 2014; Konstantinidis et al., 2017; Lehmann et al.,2010; Lenz et al., 2012a, 2012b, 2016a; Lever et al., 2010; Pletka et al.,2011). Other studies implemented a fracture gap (where the femur wasnot fixed as if anatomically reduced, and a gap was left between thefracture), typically below the tip of the hip stem prosthesis; fracture gapimplemented ranged from 5 mm to 20 mm (Choi et al., 2010; Giesingeret al., 2014; Graham et al., 2015; Griffiths et al., 2015; Gwinner et al.,2015; Konstantinidis et al., 2010; Lochab et al., 2017; Sariyilmaz et al.,2014; Shah et al., 2011). Fracture gaps were typically used to mimic afragmented fracture model (Sariyilmaz et al., 2014). Wähnert et al.(2014, 2017) and Gwinner et al. (2015) created a 45° and horizontal cutas the osteotomy gap, and a triangular wedge segment was removed.The fixed fracture with a gap between the proximal and distal frag-ments eliminates the compressive effect of the fragments, isolating theproximal fixation during testing and simulating a “worst-case” scenariowith a comminuted fracture with no cortical apposition (Demos et al.,2012). See Fig. 2 for examples of different fracture gap configurations.
A few studies investigated the effect of fracture gap and no fracturegap (Giesinger et al., 2014; Graham et al., 2015; Griffiths et al., 2015);Giesinger et al. (2014) filled the osteotomy gap with cement aftercreating a fracture to simulate ‘healed’ fracture situation. In two stu-dies, no fracture was created to simulate a healed periprosthetic frac-ture situation (Walcher et al., 2016) or a femur prior to fracture(Ebrahimi et al., 2012). Some studies did not use the distal part of thefemur distal to the osteotomy; the femur and plate construct was cutaccordingly (Brand et al., 2014; Lenz et al., 2012b, 2013, 2014; Lewiset al., 2015).
2.2.2. Plate typeWith the recent interest in advancing strategies for PFF treatment,
specialized plates have been developed for PFF, commercialized, andused in recent studies published; these include hook plates, lockingcompression plates (LCP), Variable Angle Locking plate (VA-LCP),locking attachment plates (LAP), Dall-Miles plates, cable-ready system,and non-contact bridging plate. Currently, the two main periprostheticsystems on the market and most notably studied are the LockingCompression Plate (LCP –Synthes, Solothurn, Switzerland) and Non-Contact Bridging Periprosthetic Proximal Femur Plate (NCB PP-Zimmer GmbH, Winterthur, Switzerland). Most researchers used thesesystems in their studies, and a few were interested in the direct com-parison of different construct systems (Konstantinidis et al., 2010; Leveret al., 2010; Lewis et al., 2015; Wähnert et al., 2014). Some authorsinvestigated the effect of strut allografts in place of a fracture plate or afracture plate used in conjunction with a strut (Choi et al., 2010; Lochabet al., 2017; Sariyilmaz et al., 2014). The biomechanical performance ofusing two fracture plates on a single fracture (Fig. 3) was also in-vestigated by several authors (Choi et al., 2010; Lenz et al., 2016a;Wähnert et al., 2017).
Several authors also studied use of bicortical screws for proximalplate fixation; Lochab et al., 2017; Griffiths et al., 2015; Gwinner et al.,2015; Hoffmann et al., 2014; Konstantinidis et al., 2010; Lenz et al.,2012b, 2014, 2016a, 2016b; Lewis et al., 2015; Wähnert et al., 2014,2017). One recent commercial development and a method used toachieve proximal bicortical fixation was the locking attachment plate(LAP); a clamp-on plate that is compatible and can be used in con-junction with a conventional locking compression plate (LCP) in thetreatment of PFF; the lateral arms allows for bicortical offset screwplacement laterally to the prosthesis stem (Synthes, Solothurn, Swit-zerland) (Lenz et al., 2016b). The design of the NCB PP plate (ZimmerGmbH, Winterthur, Switzerland) also allows for proximal bicorticalscrew fixation. Fig. 3 shows examples of typical variations of the PFFfixation construct used.
2.2.3. Screws and cement mantleA clinical concern regarding the way that a construct fixation is
applied is the potential breach of cement mantle integrity; in particular,cortical screw tips infringing the cement mantle and potentially leadingto substantial cement fracture and eventual hip implant loosening(Lever et al., 2010). Two authors (Kampshoff et al., 2010;Konstantinidis et al., 2017) studied the role of cement mantle integrityand screws in PFF. Konstantinidis et al. (2017) deliberately made amore brittle mantle by using hand-mixed rather than the advised va-cuum mixed cement, and Kampshoff et al. (2010) forgoed typical platefixation setup and investigated the effect of different screw implanta-tion techniques by directly drilling different screws in the cement.Brand et al. (2014) proposed and investigated a novel fixation method –intraprosthetic fixation; where screws that fixed the fracture plate tothe bone were also drilled and fixed to the cemented hip implant. An-other important factor to note is that the risk of fractures is higheraround the uncemented compared to the cemented implants(Fleischman and Chen, 2015). This is perhaps due to the higher inter-aoperative risk of fracture for uncemented implants (Wyatt, 2014). Tobest of our knowledge eight studies so far have investigated bio-mechanics of PFF fixation in uncemented hip implants (Frisch et al.,2015; Gordon et al., 2016; Gwinner et al., 2015; Hoffmann et al., 2014;Lenz et al., 2012b; Sariyilmaz et al., 2014; Wähnert et al., 2014, 2017).
2.3. Computational methods
A total of nine computational studies were reviewed in this paper,and the following section will examine the computational method used.Prior to 2010, there were only two computational studies investigatingthe biomechanics of PFF fixation. The previous review paper (Moazenet al., 2011) highlighted three main aspects in the computationalmethodologies; 1) representation of the femoral bone and fracture, 2)representation of the loads and surrounding conditions in silico, and 3)simulation predictions and accuracy. In-depth detail of these meth-odologies can be referred back to the previous paper. Here, develop-ments to these three aspects described above are discussed, with therepresentation of the femoral construct instead of the femoral bonebeing highlighted, as well as current trends.
2.3.1. Representation of the femoral construct and accuracyThe increase in present computational capabilities allow for more
geometrically accurate modelling of individual parts of the construct.Computational representation ranged from a simplified parametric FEmodel of a typical construct (Leonidou et al., 2015; Moazen et al., 2012)to more geometrically accurate 3D models. (Avval et al., 2016; Chenet al., 2012; Ebrahimi et al., 2012; Moazen et al., 2013, 2014; Shahet al., 2011; Wang et al., 2016). A clinical case was modelled using asimplified parametric FE model of the PFF fixation construct (Moazenet al., 2012). The bone, hip stem, and cement mantle were modelled asconcentric cylinders. A simplified representation of a fracture fixationplate was used, and screws were modelled as cylinders with no screwthread or head. The model was validated against a clinical case study,suggesting that simplified models are sufficient when modelling dif-ferent construct configurations. Older computational studies generatedlow resolution meshes [928–2184 elements (Mann et al., 1997; Mihalkoet al., 1992)] in comparison to current computational capabilities[61000–400,000 elements (Chen et al., 2012; Ebrahimi et al., 2012;Leonidou et al., 2015; Moazen et al., 2012; Wang et al., 2016)]. Allstudies used tetrahedral elements to mesh components.
2.3.2. Representation of the loads and surrounding conditionsIn almost all studies, FE models assumed the femur had linear,
isotropic, and elastic properties. Studies performed by several currentauthors showed that linear behaviour was a good approximation forfemurs when comparisons of FEA, synthetic femurs, and human cada-veric femurs were made (Dubov et al., 2011). However, in many
K. Wang et al. Clinical Biomechanics 61 (2019) 144–162
150
studies, the bone quality that was simulated experimentally and com-putationally were considered normal healthy bone stock, and not os-teoporotic bone seen in PFF patients. Although Dubov et al. (2011)noted that relative performance of constructs would likely remain thesame.
2.4. Overview of recent developments
2.4.1. Fixation methodsClassical computational studies of PFF fixation (Mann et al., 1997;
Mihalko et al., 1992) investigated the effects of different stem lengths astreatment methods, although Mihalko et al. (1992) also studied theeffect of plate fixation. Recent studies investigated a wider range ofdifferent fixation methods, and also the effect of fracture stability, bonequality, and fracture type. Fixation methods in present studies can bedivided into two categories. The first category considers the effect ofdifferent plate fixations (Avval et al., 2016; Moazen et al., 2012, 2014;Moazen et al., 2013; Wang et al., 2016), typically direct comparisonsbetween two plate types are made; such as rigid vs. flexible plating(Moazen et al., 2012), comparisons between the performance of stain-less steel (SS) vs. titanium (Ti) plate fixations and plate thickness(Moazen et al., 2012, 2013), double cable fixation vs. locking plate vs.multi-directional plate (Wang et al., 2016), double plating (Moazenet al., 2014), and lateral vs. anterior plating (Avval et al., 2016). Platefixation and long stem revision options under partial and full weightbearing conditions were also carried out by one group (Moazen et al.,2014). The second category considers the biomechanical performanceof different variations of a typical Ogden construct; typically this in-volves different configurations of cable, wires, or screws positions(Chen et al., 2012; Dubov et al., 2011). Four studies modelled un-cemented hip implants in their studies (Avval et al., 2016; Chen et al.,2012; Moazen et al., 2012; Wang et al., 2016)
2.4.2. Effect of fracture stability, bone quality, and fracture typeWhile the majority of computational studies focused on Vancouver
B1 type fractures; there were several authors did investigate treatmentmethods for different fracture types (Leonidou et al., 2015; Moazenet al., 2012, 2014), in one instance a Vancouver type C clinical case
comparing initially failed fixation vs a successful revision fixation wascarried out (Moazen et al., 2012). Femoral fracture stability and bonequality was also computationally modelled by several authors (Avvalet al., 2016; Ebrahimi et al., 2012; Leonidou et al., 2015; Moazen et al.,2013); Ebrahimi et al. (2012) investigated the stiffness and peak bonestress of the same femur after injury, repair, and healing with respect toits intact condition. Stable vs unstable fracture on plate fixation per-formance was also investigated (Moazen et al., 2013).
Avval et al. (2016) studied femoral density changes and bone re-modelling in the femur in response to a bone fracture plate and un-cemented hip stem implant using a validated mechano-biochemicalmodel. Bone was hypothesized as a thermodynamic system that ex-changes energy, matter, and entropy with its surroundings. The modelthey used assumed that the mechanisms of bone remodelling are exe-cuted by bone resorption and bone formation phases through fivebiochemical reactions (i.e. formation of multinucleated osteoclasts, oldbone decomposition, production of osteoblast activator, osteoid pro-duction, and calcification.)
One study, by Leonidou et al. (2015) modelled an osteoporotic bonesituation by developing three models with different canal thicknessratios (CTR) to represent poor, average, and best bone quality. Furtherthree models were developed with angle fractures varying from un-stable transverse (0°), and short oblique (146 °) to the stable long ob-lique configuration (76 °). Additional three models were developed withfracture at the tip of the stem, 4 mm, and 14 mm below the tip of thestem.
3. Results
Key results of the experimental and computational cases studied aresummarised in Table 2. Several studies using computational methodswere validated with experimental results (Dubov et al., 2011; Ebrahimiet al., 2012; Lenz et al., 2013; Moazen et al., 2013; Shah et al., 2011).The issue of lack of standardization between tests seen in past studiesstill exists, making it difficult to make direct comparisons. Most tests,like those seen in previous studies, show that increasing the overallrigidity of the construct increases the stability of the fracture. Rigiditywas measured by the overall stiffness of the instrumented femur or by
Fig. 3. Schematic diagram of different plate fixation methods onto a femoral construct with a hip stem.A-C: Schematic diagram of a typical Ogden construct (A) and a construct with an additional plate fixed with wires (B) or with screws (C). (Choi et al., 2010).D-E: Schematic diagram showing a construct with an additional LAP plate attached proximally to the plate (D), and with an additional LCP plate placed anteriorly(E). (Lenz et al., 2016a).
K. Wang et al. Clinical Biomechanics 61 (2019) 144–162
151
Table2
Asu
mm
ary
offix
atio
nm
etho
dan
dre
sults
ofth
ecu
rren
tla
bora
tory
and
com
puta
tiona
lstu
dies
inve
stig
atin
gbi
omec
hani
csof
the
peri
pros
thet
icfe
mor
alfr
actu
refix
atio
n.
Aut
hors
Test
case
Resu
lts
Expe
rim
enta
lstu
dies
Plat
ean
dst
rutfi
xatio
n
Late
ralp
late
fixat
ion
Stru
tfixa
tion
Prox
imal
Dis
tal
Posi
tion
Stru
tlen
gth
(mm
)Pr
oxim
alD
ista
l
Uni
cort
ical
Scre
wCa
ble/
wir
eBi
cort
ical
scre
wCa
ble/
wir
eCa
ble/
wir
e
(Leh
man
net
al.,
2010
)(a
)- 3 3
- - - -
- (b)
3(a
)(b
)3(
a)(b
)
- - - -
- - - -
- - - -
- - - -
Two
intr
amed
ulla
ryim
plan
tsin
fem
urw
ere
asso
ciat
edw
ithde
crea
sed
frac
ture
stre
ngth
betw
een
thes
eim
plan
ts.F
ract
ure
plat
ebe
twee
ntip
ofth
est
ems
lead
sto
good
stab
ility
rega
rdle
ssof
pres
ence
ofos
teot
omy
orre
trog
rade
naili
ng.
(Lev
eret
al.,
2010
)- - - 3 3 3
4C 4W
4C - - -
4 4 4 4 4 4
- - - - - -
- - - - - -
- - - - - -
- - - - - -
Scre
w-p
late
syst
emsp
rovi
ded
eith
ergr
eate
rore
qual
stiff
ness
com
pare
dto
cabl
e-pl
ates
inal
mos
tal
lcas
es.N
ost
atis
tical
diffe
renc
esbe
twee
nth
eth
ree
diffe
rent
plat
ing
syst
ems
used
toco
mpa
reca
ble
vssc
rew
fixat
ion
-Zi
mm
erCa
ble
read
ysy
stem
(Zim
mer
,IN,U
SA),
AO
cabl
e-pl
ate
syst
em(S
ynth
es,P
A,U
SA),
and
Dal
l-Mile
sca
ble
grip
syst
em(H
owm
edic
a,N
J,U
SA).
(Cho
iet
al.,
2010
)2 2 2/
2(c
)
2 - 2
4 4 4/4c
- Ant
-
- 188
-
- 2C -
- 2C -
Fixa
tion
usin
gdo
uble
plat
essh
owhi
ghes
tst
iffne
ss,h
owev
erre
sults
dem
onst
rate
dth
atus
eof
addi
tiona
lallo
graf
tst
rut
inco
njun
ctio
nw
itha
LCP
also
prov
ided
supe
rior
stiff
ness
com
pare
dto
sing
lelo
cked
plat
e(L
CP–S
ynth
es)
for
Vanc
ouve
rty
peB1
fem
oral
frac
ture
s.(K
onst
antin
idis
etal
.,20
10)
4(d
-5)
4BC
(e-B
C)- -
3 3- -
- -- -
- -Bi
cort
ical
scre
wpl
acem
ent
(NCB
plat
e;Zi
mm
er,I
N,U
SA)
show
edsu
peri
oran
dm
ore
stab
lean
chor
ing
com
pare
dto
unic
ortic
alsc
rew
fixat
ion
(LIS
Spl
ate;
Synt
hes,
Switz
erla
nd).
Mea
nfo
rce
resu
lting
insu
bseq
uent
mod
elfa
ilure
sim
ilar
inbo
thm
odel
s.Su
gges
ting
NCB
plat
ew
asno
tsup
erio
rto
the
LISS
plat
e;m
oreo
verN
CBsy
stem
show
edm
ater
ial
fatig
ueun
der
cycl
iclo
adin
g,su
gges
ting
incr
ease
dim
plan
tfa
ilure
rate
spa
rtic
ular
lyin
case
sof
dela
yed
bony
unio
n.(P
letk
aet
al.,
2011
)3 3
2 24 4
- -- -
- -- -
Type
ofpl
ate
and
wor
king
leng
thdi
dno
tsig
nific
antly
affec
tfai
lure
rate
,no
sign
ifica
ntdi
ffere
nces
was
foun
dbe
twee
nlo
ngan
dsh
ort
plat
esfo
rdi
spla
cem
ento
rro
tatio
nat
frac
ture
site
.Low
erbo
nem
iner
alde
nsity
sign
ifica
ntly
asso
ciat
edw
ithfa
ilure
.(S
hah
etal
.,20
11)
- 4 4
4C - 4C
4 4 4
- - -
- - -
- - -
- - -
Cabl
esab
sorb
edm
ajor
ityof
load
,fol
low
edby
plat
esan
dth
ensc
rew
s.O
ptim
alm
echa
nica
lsta
bilit
yca
nbe
achi
eved
usin
gca
bles
and
scre
ws,
then
scre
ws
–as
both
had
the
high
est
stiff
ness
es.I
fonl
yca
bles
are
used
clin
ical
ly,a
plat
ew
ithou
tpr
oxim
alho
les
reco
mm
ende
d.(D
emos
etal
.,20
12)
3(L
S)3
(LS)
3 -
- 3 3 3
4 4 4 4
- - - -
- - - -
- - - -
- - - -
Prox
imal
cabl
efix
atio
npr
ovid
essi
gnifi
cant
lyle
ssax
ials
tabi
lity
com
pare
dto
whe
nca
bles
and
scre
ws
wer
eus
ed.L
ocki
ngan
dno
n-lo
ckin
gsc
rew
cons
truc
tssh
owed
equi
vale
ntlo
ads
atfa
ilure
,and
supe
rior
inlo
adat
failu
reco
mpa
red
toca
bles
.(L
enz
etal
.,20
12a)
5 2+
3(e
-BC)
- -3 3
- -- -
- -- -
A-L
CP(p
roto
type
lock
ing
plat
e)w
ithpr
oxim
albi
cort
ical
and
unic
ortic
alsc
rew
fixat
ion
had
high
ernu
mbe
rof
cycl
esto
failu
reco
mpa
red
toco
nven
tiona
lLCP
usin
gpr
oxim
alun
icor
tical
scre
wfix
atio
n,an
dsh
owed
high
erco
nstr
ucts
tabi
lity
and
stre
ngth
.Bic
ortic
alsc
rew
posi
tioni
ngsh
owed
less
inte
rfra
gmen
tary
oste
otom
ym
ovem
ent,
sugg
estin
gim
prov
edos
teos
ynth
esis
inpe
ripr
osth
etic
frac
ture
s.(L
enz
etal
.,20
12b)
3 3(f
-2BC
)1
Ce-
- -- -
- -- -
- -LA
P-LC
Pco
nstr
uct
grou
pus
ing
addi
tiona
lpro
xim
albi
cort
ical
scre
wfix
atio
nha
dsi
gnifi
cant
lyhi
gher
stiff
ness
and
num
ber
ofcy
cles
tofa
ilure
com
pare
dto
cerc
lage
-LCP
cons
truc
t.U
seof
LAP
and
plac
ing
bico
rtic
allo
ckin
gsc
rew
sla
tera
llyat
pros
thes
isst
emca
nim
prov
est
abili
tyin
PFF
fixat
ion.
(continuedon
nextpage
)
K. Wang et al. Clinical Biomechanics 61 (2019) 144–162
152
Table2
(continued)
Aut
hors
Test
case
Resu
lts
Expe
rim
enta
lstu
dies
Plat
ean
dst
rutfi
xatio
n
Late
ralp
late
fixat
ion
Stru
tfixa
tion
Prox
imal
Dis
tal
Posi
tion
Stru
tlen
gth
(mm
)Pr
oxim
alD
ista
l
Uni
cort
ical
Scre
wCa
ble/
wir
eBi
cort
ical
scre
wCa
ble/
wir
eCa
ble/
wir
e
(Len
zet
al.,
2013
)(k
)- 1 -
1Ce
- -
- - 1
- - -
- - -
- - -
- - -
Both
scre
wfix
atio
nty
pes(
Uni
cort
ical
and
bico
rtic
al)s
how
edsi
gnifi
cant
lyhi
gher
ultim
ate
stre
ngth
and
stiff
ness
inax
ialc
ompr
essi
onan
dto
rsio
nco
mpa
red
toce
rcla
gefix
atio
n.Re
sults
ofm
echa
nica
ltes
tw
ere
visu
ally
confi
rmed
byFE
Afo
run
icor
tical
and
bico
rtic
alsc
rew
s.(W
ähne
rtet
al.,
2014
)2
(f–
2BC
)4
(g)
- -3 3
- -- -
- -- -
Both
fixat
ion
syst
ems
achi
eved
prox
imal
bico
rtic
alsc
rew
fixat
ion
arou
ndth
ehi
pst
em.L
AP-
LCP
cons
truc
tfo
und
less
stab
ledu
eto
less
rigi
dm
ain
plat
e.N
CBpl
ate
show
edsi
gnifi
cant
lyhi
gher
stiff
ness
and
cycl
esto
failu
re.
(Gie
sing
eret
al.,
2014
)4
–3
––
––
No
stat
istic
ally
sign
ifica
ntdi
ffere
nces
inax
ialn
orin
med
ial(
Varu
s)st
emm
igra
tion
com
pare
dto
aco
ntro
lgro
up.L
ocki
ngpl
ate
fixat
ion
ofa
PFF
with
stab
lece
men
ted
pros
thes
isdi
dno
tlea
dto
cem
ent
man
tlefa
ilure
.(B
rand
etal
.,20
14)
3 2(h
)- -
1 1- -
- -- -
- -In
trap
rost
hetic
fixat
ion
prov
ided
sign
ifica
ntly
high
erfa
ilure
load
sco
mpa
red
toun
icor
tical
lock
ed-s
crew
plat
ing.
Sign
ifica
ntin
crea
sein
prim
ary
stab
ility
with
out
wea
keni
ngth
eim
plan
t-cem
ent-f
emur
-mod
elth
atco
uld
lead
toea
rly
wei
ght-b
eari
ngpa
tient
mob
iliza
tion.
(Len
zet
al.,
2014
)3 - 4 3(
f-2
BC)
1Ce
4Ce
- -
2 2 2 2
- - - -
- - - -
- - - -
- - - -
Prox
imal
bico
rtic
alfix
atio
nus
ing
LAP-
LCP
cons
truc
tim
prov
esst
abili
tyof
prox
imal
plat
efix
atio
nin
Peri
pros
thet
icfr
actu
res.
Cerc
lage
cabl
e-s
crew
com
bina
tion
isva
luab
leal
tern
ativ
e,es
peci
ally
inos
teop
orot
icbo
ne.
Cerc
lage
ssh
ould
beus
edin
com
bina
tion
with
atle
ast
one
addi
tiona
lsc
rew
toac
hiev
est
able
fixat
ion.
(Hoff
man
net
al.,
2014
)6
(e-B
C)4 -
- 1W
3C
3 3 3
- - -
- - -
- - -
- - -
Prox
imal
bico
rtic
alsc
rew
plac
emen
tach
ieve
dm
axim
allo
adto
failu
rean
dm
axim
alto
rsio
nal/
sagi
ttal
bend
ing
stiff
ness
.Add
ition
ofun
icor
tical
scre
ws
incr
ease
dax
ials
tiffne
ssw
hen
cabl
efix
atio
nus
ed.L
ater
albe
ndin
gno
taff
ecte
dby
diffe
renc
esin
prox
imal
fixat
ion.
(Sar
iyilm
azet
al.,
2014
)2 2 2
2C - -
4 2 2
- Med
Ant
- 150
150
- 2C 2C
- 2C 2C
Med
ials
trut
allo
graf
tw
ithpl
ate
fixat
ion
show
edhi
ghes
tst
iffne
ssan
dfa
ilure
load
valu
esan
dle
astd
ispl
acem
enta
tfra
ctur
esi
te.S
ugge
stin
git
ism
echa
nica
llysu
peri
orm
etho
din
B1ty
pePF
Ffix
atio
ntr
eatm
entn
ear
tipof
THA
(Gri
ffith
set
al.,
2015
)5 2
(f–
4BC
)2C -
5 5- -
- -- -
- -LA
P-LC
Pco
nstr
uct
sign
ifica
ntly
stiff
erth
anca
ble
cons
truc
tund
erax
ial
load
with
bone
gap.
Offe
rsbe
tter
axia
lstiff
ness
com
pare
dto
cabl
eco
nstr
uct.
(Gra
ham
etal
.,20
15)
3 3 -
- 3C 3C
3 3 3
- - -
- - -
- - -
- - -
Uni
cort
ical
scre
ws
show
edst
iffes
tfo
rmof
fixat
ion
atal
lloa
ding
angl
es.
Sugg
ests
that
cabl
esre
sult
inth
epr
oxim
alsc
rew
sbe
ing
push
edin
toth
ebo
neas
itis
appl
ied,
caus
ing
scre
ws
tolo
osen
thei
rfix
atio
nto
bone
.Fr
actu
rega
pan
dno
gap
mod
elbe
have
diffe
rent
ly–
degr
eeof
frac
ture
redu
ctio
naff
ects
who
leco
nstr
ucts
tabi
lity
and
bend
ing
beha
viou
rof
fixat
ion.
(Gw
inne
ret
al.,
2015
)4 3
(e-B
C)- -
5 5- -
- -- -
- -Fa
ilure
mod
ein
unic
ortic
algr
oup
char
acte
rise
dby
scre
wpu
ll-ou
twith
noad
ditio
nalb
one
frac
ture
orfis
sure
.Pro
xim
albi
cort
ical
scre
wfix
atio
nsh
owed
nosc
rew
pull-
out,
and
had
high
ercy
cles
tofa
ilure
.Bic
ortic
algr
oup
also
show
edsi
gnifi
cant
supe
rior
ityof
scre
wpu
rcha
seco
mpa
red
toun
icor
tical
scre
ws.
How
ever
,mod
eof
failu
rere
sulte
din
seve
reco
mm
uted
frac
ture
patt
erns
com
pare
dto
the
unic
ortic
alsc
rew
s,w
hich
only
resu
lted
insc
rew
pull-
out.
(Lew
iset
al.,
2015
)- 4
LS4
LS
3Ce
- 2C
- - -
- - -
- - -
- - -
- - -
Prox
imal
bico
rtic
alsc
rew
fixat
ion
cons
truc
ts(L
AP
+SS
LCP,
Synt
hes,
PA,
USA
,and
TiN
CB,Z
imm
er,I
N,U
SA)
show
edhi
gher
max
imum
forc
esin
tors
iona
lloa
ding
com
pare
dto
cabl
e,un
icor
tical
lock
ing
scre
ws
(LS)
,and
(continuedon
nextpage
)
K. Wang et al. Clinical Biomechanics 61 (2019) 144–162
153
Table2
(continued)
Aut
hors
Test
case
Resu
lts
Expe
rim
enta
lstu
dies
Plat
ean
dst
rutfi
xatio
n
Late
ralp
late
fixat
ion
Stru
tfixa
tion
Prox
imal
Dis
tal
Posi
tion
Stru
tlen
gth
(mm
)Pr
oxim
alD
ista
l
Uni
cort
ical
Scre
wCa
ble/
wir
eBi
cort
ical
scre
wCa
ble/
wir
eCa
ble/
wir
e
4(2
f-4
BCea
ch)
(j)6
(e)
- -- -
- -- -
- -- -
cabl
e+
unic
ortic
alLS
cons
truc
ts.C
able
cons
truc
tssh
owed
the
low
est
max
imum
forc
es,i
nbo
thax
iala
ndto
rsio
nall
oadi
ng.
Bico
rtic
alTi
NCB
cons
truc
tsho
wed
high
erst
iffne
ssth
anth
ebi
cort
ical
SSLA
P-LC
Pco
nstr
uct
inax
iall
oadi
ng.
(Len
zet
al.,
2016
a)3
(f−
2BC
)/4(
i)3
(2f−
2BC
each
)(j)
- -
2/
2
2
- -
- -
- -
- -
LAP
-Dou
ble
LCP
plat
e(O
rtho
gona
l)co
nstr
uct
fixat
ion
show
edsi
gnifi
cant
lyhi
gher
stiff
ness
,cyc
les,
and
load
tofa
ilure
com
pare
dto
LAP
(x2)
-sin
gle
LCP
plat
eco
nstr
uct.
Add
ition
allo
ckin
gpl
ate
enha
nces
cons
truc
tsta
bilit
yan
din
crea
ses
cons
truc
tst
iffne
ssco
mpa
red
tosi
ngle
plat
efix
edw
ithtw
oLA
P.(L
enz
etal
.,20
16b)
2(G
T),3
3(f
–2
BC)
- -2 2
- -
- -
- -
- -
Hoo
kco
nstr
ucts
how
edsi
gnifi
cant
lylo
wer
cycl
esan
dlo
adto
failu
rean
dfix
atio
nst
reng
thco
mpa
red
toLA
P-LC
Pco
nstr
uct.
Plat
est
iffne
ssbe
twee
nth
etw
ogr
oups
wer
eco
mpa
rabl
ein
rang
e.U
seof
subt
roch
ante
rica
lbi
cort
ical
scre
wfix
atio
nis
aneff
ectiv
efix
atio
nm
etho
din
PPF
than
hook
plat
e,an
dis
less
influ
ence
dby
bone
stoc
kqu
ality
.Sug
gest
sth
atho
okpl
ate
isre
serv
edfo
rPPF
that
requ
ires
stab
iliza
tion
ofgr
eate
rtro
chan
tera
sit
ishi
ghly
BMD
depe
nden
t.(M
oaze
net
al.,
2016
)6
(e)
6(e
)- -
4 4- -
- -- -
- -Pr
oxim
albi
cort
ical
scre
wfix
atio
nus
ing
far
cort
ical
lock
ing
scre
ws
can
redu
ceov
eral
leffe
ctiv
est
iffne
ssof
lock
ing
plat
esan
din
crea
sefr
actu
rem
ovem
ent
whi
lem
aint
aini
ngov
eral
lstr
engt
hof
PFF
fixat
ion
cons
truc
tco
mpa
red
tobi
cort
ical
scre
wfix
atio
nus
ing
lock
ing
scre
ws.
Inun
stab
lefr
actu
res
alte
rnat
ive
fixat
ion
met
hods
such
aslo
ngst
emre
visi
onm
aybe
bett
er.
(Wäh
nert
etal
.,20
17)
2(f
-2BC
)2/
2(o)
- -3 3/
2(o)
- -- -
- -- -
Cons
truc
tstiff
ness
and
cycl
esto
failu
resi
gnifi
cant
lyhi
gher
indo
uble
-pl
ate
cons
truc
tco
mpa
red
toLC
P-LA
Pco
nstr
uct.
(Loc
hab
etal
.,20
17)
3 4(2
f)(l
)2C -
4,2C
(m)
4A
nt-
200
-2
Ce(n
)-
2C -LC
P-A
llogr
aft
cons
truc
tdem
onst
rate
dhi
gher
stiff
ness
valu
esin
com
pres
sive
abdu
ctio
n,to
rsio
n,an
dm
edia
l-lat
eral
four
-poi
ntbe
ndin
gco
mpa
red
toth
eLA
P-LC
Pco
nstr
uct.
No
diffe
renc
esid
entifi
edbe
twee
nth
etw
oco
nstr
ucts
inco
mpr
essi
vefle
xion
,ant
erio
r-po
ster
ior
bend
ing
orlo
adto
failu
rete
sts.
Long
stem
vssh
ort
stem
(Gor
don
etal
.,20
16)
Com
pari
son
of4
grou
ps,s
hort
stem
sve
rsus
long
stem
sfo
rth
eir
effec
tiven
ess,
and
lock
ing
plat
efix
atio
nve
rsus
cerc
lage
syst
em:
1–
Long
stem
/Cer
clag
e–(4
titan
ium
cerc
lage
band
san
d2
stab
ilize
rs)
2–
Long
stem
/Pla
te–(
NCB
,5pr
oxim
alun
icor
tical
scre
ws
and
4di
stal
bico
rtic
alsc
rew
s)3
–Sh
ort
stem
/Cer
clag
e–
(4tit
aniu
mce
rcla
geba
nds
and
2st
abili
zers
)4
–Sh
ort
stem
/Pla
te–(
NCB
,5pr
oxim
alun
icor
tical
scre
ws
and
4di
stal
bico
rtic
alsc
rew
s)
Resu
ltsin
dica
teth
atfo
rVan
couv
erB1
frac
ture
s,os
teos
ynth
esis
with
plat
efix
atio
nha
sno
biom
echa
nica
ladv
anta
ges
over
use
ofsi
mpl
ece
rcla
gesy
stem
–ce
rcla
geco
nstr
ucts
dem
onst
rate
dla
rger
stiff
ness
,lar
gers
tren
gth,
and
mor
ecy
cles
tofa
ilure
com
pare
dto
plat
eco
nstr
uct.
Revi
sion
with
alo
ngst
empr
ovid
essu
peri
orm
echa
nica
lsta
bilit
yre
gard
less
ofty
peof
oste
osyn
thes
isfix
atio
n,th
ussu
itabl
efo
rVa
ncou
ver
B1fr
actu
retr
eatm
ent.
Insh
orts
tem
incr
ease
dsu
bsid
ence
isse
enin
cerc
lage
syst
emco
mpa
red
topl
atin
g.
Plat
ean
dst
emdi
stan
ce(W
alch
eret
al.,
2016
)Bi
omec
hani
calp
erfo
rman
ceto
esta
blis
hsa
fedi
stan
ceof
plat
efr
omtip
offe
mor
alpr
osth
esis
.–A
mou
ntof
plat
eto
stem
over
lap
orw
heth
erth
ere
isa
safe
gap
betw
een
the
stem
and
the
plat
een
dto
redu
ceri
skof
futu
refr
actu
res.
All
NCB
dist
alpl
ates
wer
eat
tach
edto
the
fem
urat
ade
fined
dist
ance
from
the
stem
toth
epl
ate
atva
ryin
gga
psfr
om80
mm
gap
to60
mm
over
lap,
in20
mm
incr
emen
ts.
40m
mga
p–
40m
mov
erla
pco
nsid
ered
clos
egr
oup,
and
grea
ter
that
40m
mov
erla
por
dist
ance
cons
ider
edfa
rgr
oup.
Stra
inin
crea
sed
with
the
decr
ease
dov
erla
por
gap.
All
earl
yfa
ilure
soc
curr
edbe
twee
n20
mm
over
lap
and
gap.
Sign
ifica
ntly
less
stra
inin
the
far
grou
pin
both
axia
land
tors
iona
lloa
ding
.Su
gges
tsth
atre
sults
can
aid
orth
opae
dic
surg
eons
inpl
ate
posi
tioni
ngin
Vanc
ouve
rtyp
e-C
PFF
fixat
ion.
Redu
ctio
nin
post
-ope
rativ
eco
mpl
icat
ions
(continuedon
nextpage
)
K. Wang et al. Clinical Biomechanics 61 (2019) 144–162
154
Table2
(continued)
Aut
hors
Test
case
Resu
lts
Expe
rim
enta
lstu
dies
Plat
ean
dst
rutfi
xatio
n
Late
ralp
late
fixat
ion
Stru
tfixa
tion
Prox
imal
Dis
tal
Posi
tion
Stru
tlen
gth
(mm
)Pr
oxim
alD
ista
l
Uni
cort
ical
Scre
wCa
ble/
wir
eBi
cort
ical
scre
wCa
ble/
wir
eCa
ble/
wir
e
Dis
talp
late
swer
efix
edus
ing
2bi
cort
ical
scre
wsa
tthe
mos
tpro
xim
alsc
rew
hole
sand
2bi
cort
ical
scre
wsi
nth
efo
urth
and
fifth
hole
s.N
ofe
mor
alfr
actu
rew
asap
plie
dto
sim
ulat
esi
tuat
ion
ofhe
aled
peri
pros
thet
icfr
actu
rew
ithim
plan
tsst
illin
situ
.by
posi
tioni
ngth
epl
ate
ina
man
ner
that
may
redu
cest
ress
rise
rsth
atco
uld
lead
tofu
ture
frac
ture
s.
Cabl
es(F
risc
het
al.,
2015
)Bi
omec
hani
calr
espo
nse
ofce
rcla
gesy
stem
sin
fixat
ion
ofin
trao
pera
tive
PFF
ince
men
tless
THA
.Fou
rco
nstr
ucts
com
pare
d,1)
CoCr
(Cob
alt-C
hrom
e)ca
ble
2)H
ose
clam
p3)
Mon
ofila
men
tw
ire
4)Sy
nthe
ticca
ble.
No
plat
efix
atio
nus
ed.
Met
allic
cons
truc
tsw
ithpo
sitiv
elo
ckin
gsy
stem
perf
orm
edbe
st,
supp
ortin
ghi
ghes
tloa
dsw
ithm
inim
alim
plan
tsub
side
nce
(bot
hax
iala
ndan
gula
r)af
ter
load
ing.
CoCr
cabl
ean
dho
secl
amp
had
high
est
cons
truc
tst
iffne
ssan
dle
ast
redu
ctio
nin
stiff
ness
with
incr
ease
dlo
adin
g.
Scre
ws
(Kam
psho
ffet
al.,
2010
)Eff
ecto
fdiff
eren
tscr
ewim
plan
tatio
nte
chni
ques
onth
ein
tegr
ityof
loca
lcem
entm
antle
and
fixat
ion
stre
ngth
ofth
esc
rew
.Usi
ngdi
ffere
ntki
nds
oflo
ckin
gsc
rew
s.LC
S(S
ynth
es,O
berd
orf,
Switz
erla
nd)a
ndN
CB(Z
imm
er,W
arsa
w,I
N,U
SA),
with
orw
ithou
tafla
tten
edtip
,im
plan
ted
inun
icor
tical
and
bico
rtic
alco
nfigu
ratio
nsus
ing
diffe
rent
core
drill
size
s
No
unic
ortic
alsc
rew
indu
ced
crac
ks–
unic
ortic
alsc
rew
scan
beim
plan
ted
with
out
dam
agin
gce
men
tman
tle.S
crew
sw
ithsh
orte
ned
tip,s
mal
ler
flute
san
ddo
uble
thre
ads
wer
esi
gnifi
cant
lybe
tter
for
pull-
outr
esis
tanc
e.Bi
cort
ical
scre
ws
have
sign
ifica
ntly
high
erpu
ll-ou
tre
sist
ance
,but
incr
ease
risk
oflo
calc
emen
tman
tleda
mag
e.By
incr
easi
ngdr
illdi
amet
er,
onse
tof
crac
ksde
crea
sed,
but
sodo
espu
llou
tre
sist
ance
.(K
onst
antin
idis
etal
.,20
17)
Dam
age
anal
ysis
ofce
men
tm
antle
afte
rre
visi
onsc
rew
inse
rtio
n;In
fluen
ceof
thre
eva
riab
les
onth
ein
cide
nce
ofcr
ack
form
atio
nin
cem
entl
ayer
was
stud
ied;
scre
wty
pe.C
emen
tm
antle
thic
knes
s,an
dpo
sitio
nof
scre
wre
lativ
eto
cem
ent
man
tlean
dpr
osth
etic
stem
.
LCP
plat
esh
orte
ned
toha
vefo
urho
les
only
,and
appl
ied
late
rally
toth
efe
mur
atth
ele
velo
fthe
pros
thet
icst
em(p
roxi
mal
).Th
ree
type
sof
scre
wfix
atio
nm
etho
dsin
vest
igat
ed1)
four
bico
rtic
alno
n-lo
ckin
gsc
rew
s.2)
Four
unic
ortic
allo
ckin
gsc
rew
s.3)
Four
bico
rtic
allo
ckin
gsc
rew
s.
Crac
kfo
rmat
ion
foun
dto
beho
mog
eneo
usfo
rall
thre
esc
rew
type
s.Sc
rew
posi
tions
rela
tive
toce
men
tan
dpr
osth
etic
stem
was
divi
ded
into
four
cate
gori
es:1
)N
oco
ntac
tbe
twee
nsc
rew
and
cem
ent
man
tle.2
)Sc
rew
touc
hes
cem
entm
antle
and
ispa
rtia
llyw
ithin
it.3)
Scre
wis
entir
ely
with
inth
ece
men
tman
tle.4
)Scr
ewis
indi
rect
cont
actw
ithpe
ripr
osth
etic
stem
.
Sign
ifica
ntas
soci
atio
nbe
twee
nsc
rew
posi
tion
and
inci
denc
eof
crac
ksin
the
man
tle.P
roba
bilit
yof
dam
age
toth
ece
men
tman
tlein
crea
ses
sign
ifica
ntly
asth
edi
stan
ceto
the
impl
ante
dpr
osth
esis
decr
ease
s.Sc
rew
sin
dire
ctco
ntac
tw
ithth
epe
ripr
osth
etic
stem
show
edhi
ghin
cide
nce
ofcr
ack
dam
age
toth
ece
men
tman
tle.S
ugge
stst
hato
nly
the
posi
tion
ofth
esc
rew
sre
lativ
eto
the
cem
ent
man
tlean
d/or
peri
pros
thet
icst
emex
erts
sign
ifica
ntin
fluen
ceon
the
crac
kda
mag
eto
the
cem
ent
man
tle.
Com
puta
tiona
lstu
dies
(Dub
ovet
al.,
2011
)Bi
omec
hani
calp
erfo
rman
ceof
cabl
e-sc
rew
posi
tion
inre
pair
ing
peri
pros
thet
icfe
mur
frac
ture
sne
artip
ofa
tota
lhip
impl
ant
(Com
puta
tiona
lstu
dyof
the
expe
rim
enta
lstu
dyca
rrie
dou
tby
the
sam
egr
oup
Shah
etal
.,20
11).
Thre
edi
ffere
ntfix
atio
nm
etho
dsde
scri
bed
1)Co
nstr
uctA
-Cab
le-s
crew
pair
sin
posi
tions
1an
d2
prox
imal
tofr
actu
re2)
Cons
truc
tB-C
able
-scr
ewpa
irsi
npo
sitio
ns1
and
3.3)
Cons
truc
tC–
Cabl
e-sc
rew
pair
sin
posi
tions
1an
d4.
All
thre
eco
nstr
ucts
had
four
bico
rtic
alsc
rew
sdi
stal
ly.
Num
eric
alco
mpu
tatio
nat
1000
Nax
iall
oad
and
15°a
dduc
tion
ofth
efe
mur
show
edhi
gher
axia
lstiff
ness
and
high
ersu
rfac
est
ress
tran
sfer
toth
efe
mor
albo
nefo
rCon
stru
ctC
(cab
le-s
crew
pair
sin
extr
eme
posi
tions
).Su
gges
ting
inth
eca
seof
good
bone
stoc
k,op
timal
fixat
ion
can
beac
hiev
edby
Cons
truc
tC,
and
coul
dpo
tent
ially
redu
cebo
nere
-frac
ture
com
pare
dw
ithA
and
B–
asit
isex
pect
edth
atth
ehi
ghes
tst
iffne
ssm
ayac
hiev
eop
timal
mec
hani
cals
tabi
lity.
FEA
show
edex
celle
ntco
rrel
atio
nw
ithex
peri
men
talr
esul
ts.
(Moa
zen
etal
.,20
12)
Dev
elop
men
tand
anal
ysis
ofan
FEm
odel
ofa
Vanc
ouve
rty
peC
clin
ical
case
com
pari
ngm
echa
nica
leffe
cts
betw
een
two
impl
emen
ted
fixat
ion
met
hods
;whe
rein
the
initi
alfix
atio
nfa
iled
and
repl
aced
bya
seco
ndfix
atio
nth
atle
dto
heal
ing.
Initi
alpl
ate
fixat
ion
follo
win
gTH
Aus
eda
fem
oral
poly
axia
lpla
te(r
igid
fixat
ion
-PO
LYA
X,D
ePuy
,IN
,USA
),Re
frac
ture
revi
sion
used
aco
ndyl
arbl
ade
plat
e(fl
exib
lefix
atio
n-A
ngle
dBl
ade
Plat
e,Sy
nthe
s,PA
)
Rigi
dfr
actu
refix
atio
n(p
olya
xial
plat
e)w
ithsh
ortb
ridg
ing
leng
thin
the
case
ofPF
Fca
nsu
ppre
ssfr
actu
rem
ovem
entt
hatc
anpr
even
thea
ling
and
may
ultim
atel
yfa
il.In
cont
rast
use
ofa
flexi
ble
fixat
ion
non-
lock
ing
plat
ew
ithla
rger
brid
ging
leng
thpr
omot
edhe
alin
g.Ch
angi
ngbr
idgi
ngle
ngth
mad
ea
mor
esu
bsta
ntia
ldiff
eren
ceto
stiff
ness
and
frac
ture
mov
emen
tth
anot
her
para
met
ers.
Resu
ltssu
gges
ttha
taco
mpu
tatio
nala
ppro
ach
toco
mpa
rest
iffne
ssan
dfr
actu
rem
ovem
ent
ofdi
ffere
ntfix
atio
nco
nstr
ucts
can
help
dete
rmin
eop
timum
fixat
ion
met
hod
for
PFF.
(continuedon
nextpage
)
K. Wang et al. Clinical Biomechanics 61 (2019) 144–162
155
Table2
(continued)
Aut
hors
Test
case
Resu
lts
Expe
rim
enta
lstu
dies
Plat
ean
dst
rutfi
xatio
n
Late
ralp
late
fixat
ion
Stru
tfixa
tion
Prox
imal
Dis
tal
Posi
tion
Stru
tlen
gth
(mm
)Pr
oxim
alD
ista
l
Uni
cort
ical
Scre
wCa
ble/
wir
eBi
cort
ical
scre
wCa
ble/
wir
eCa
ble/
wir
e
(Che
net
al.,
2012
)Fi
nite
elem
ent
anal
ysis
perf
orm
edto
stud
yin
tern
albi
omec
hani
calf
orce
sdu
ring
fixat
ion
ofVa
ncou
ver
type
B1pe
ripr
osth
etic
frac
ture
with
anO
gden
cons
truc
tand
four
vari
atio
nsof
this
cons
truc
t.1)
A-P
roxi
mal
ly3
wir
es,d
ista
lly2
bico
rtic
alsc
rew
s.2)
B-Pr
oxim
ally
3w
ires
plus
2un
icor
tical
scre
ws,
dist
ally
2bi
cort
ical
scre
ws
3)C-
Prox
imal
ly3
wir
es,d
ista
lly2
bico
rtic
alsc
rew
spl
us3
wir
es4)
D-
Prox
imal
ly3
wir
espl
us2
unic
ortic
alsc
rew
s,di
stal
ly2
bico
rtic
alsc
rew
spl
us3
wir
es.
Resu
ltssh
owth
ator
igin
alba
sic
Ogd
enco
nstr
uct(
A)
fixat
ion
has
infe
rior
outc
ome
com
pare
dto
othe
rfix
atio
nm
etho
ds.A
dditi
onof
two
scre
ws
abov
eth
efr
actu
resi
te(C
onst
ruct
B)vi
sibl
yde
crea
sed
disp
lace
men
tan
dst
ress
.Add
ition
alw
ires
fixed
belo
wfr
actu
resi
tedo
notn
otic
eabl
yde
crea
seei
ther
von
Mis
esst
ress
orfr
actu
redi
spla
cem
ent(
Cons
truc
tC)
.Be
tter
fixat
ion
pow
eris
achi
eved
byus
ing
both
prox
imal
and
dist
alsc
rew
sin
trea
ting
Vanc
ouve
rB1
peri
pros
thet
icfr
actu
res
afte
rTH
A.
(Ebr
ahim
iet
al.,
2012
)Ex
peri
men
tala
ndco
mpu
tatio
nals
tudy
topr
edic
tove
rall
stiff
ness
and
peak
bone
stre
ssin
the
sam
efe
mur
afte
rinj
ury,
repa
ir,a
ndhe
alin
g,w
ithre
spec
tto
itsin
tact
cond
ition
.Fou
rsta
ges
wer
ede
scri
bed.
1)St
age
1–
inta
ctfe
mur
2)St
age
2–
mim
icke
dfe
mur
with
ahi
pst
em3)
Stag
e3
–m
imic
ked
5m
mfr
actu
rega
pre
pair
edw
ithpl
ate
and
scre
ws
4)St
age
4–
repr
esen
ted
com
plet
efr
actu
reun
ion.
FEm
odel
valid
ated
agai
nst
expe
rim
ents
and
re-a
naly
sed
usin
gcl
inic
al-le
velf
orce
of30
00N
Stag
e3
(im
med
iate
post
-sur
gica
lsce
nari
oof
peri
pros
thet
icfe
mor
alfr
actu
refix
atio
n)sh
owed
leas
tsta
ble
situ
atio
nco
mpa
red
tost
age
1,be
ing
the
mos
tvul
nera
ble
tore
-inju
ry;y
ield
ing
the
low
ests
tiffne
ssan
dhi
ghes
tbo
nest
ress
com
pare
dto
stag
e1
(Int
act
fem
ur).
Stag
e4
(hea
led
fem
ur)
show
edri
sein
stiff
ness
surp
assi
ngst
age
1an
dre
-dis
trib
utio
nof
stre
sses
back
tofe
mur
itsel
fcom
pare
dto
stag
e3.
Stud
yhi
ghlig
hts
the
pote
ntia
ladv
erse
effec
tsof
stre
ss-s
hiel
ding
and
high
stre
sses
thro
ugho
utth
esu
rgic
alpr
oces
san
dev
enaf
ter
frac
ture
heal
ing.
Sugg
ests
ast
iffne
ss-m
atch
ing
stra
tegy
infu
ture
desi
gnof
impl
ants
rela
tive
toth
ein
tact
fem
ur.
At1
500
N,F
Evs
Expe
rim
enta
lstr
ains
had
exce
llent
linea
rag
reem
ent.
(Moa
zen
etal
.,20
13)
FEm
odel
ofVa
ncou
vert
ype
B1PF
Ffix
atio
nw
ithin
ast
able
stem
with
good
bone
qual
ityde
velo
ped.
Effec
toff
ract
ure
stab
ility
onlo
ckin
gpl
ate
fixat
ion
perf
orm
ance
quan
tified
,and
com
pari
son
ofst
ainl
ess
stee
l(SS
)and
titan
ium
(Ti)
plat
ein
stab
lean
dun
stab
lefr
actu
reun
der
two
wei
ght-b
arin
gco
nditi
ons
-500
Nan
d23
00N
,ana
lysi
sca
rrie
dou
t.
Stre
ssan
dst
rain
onth
epl
ate
was
high
erin
the
unst
able
com
pare
dto
the
stab
lefix
atio
n.In
the
case
ofun
stab
lefr
actu
res,
itis
poss
ible
for
asi
ngle
lock
ing
plat
efix
atio
nto
prov
ide
the
requ
ired
mec
hani
cale
nvir
onm
entf
orca
llusf
orm
atio
nw
ithou
tsig
nific
antr
isk
ofpl
ate
frac
ture
,pro
vide
dpa
rtia
lw
eigh
tbe
arin
gis
follo
wed
.In
case
sw
here
part
ialw
eigh
tbea
ring
isun
likel
y,ad
ditio
nalb
iolo
gica
lfixa
tion
coul
dbe
cons
ider
ed.
(Moa
zen
etal
.,20
14)
Biom
echa
nica
lper
form
ance
ofsi
xdi
ffere
ntfix
atio
nm
etho
dsfo
rVan
couv
erB1
and
B2ty
pefr
actu
ress
tudi
ed.1
)Use
ofei
ght-h
ole
lock
ing
plat
e:fix
edla
tera
llyus
ing
3un
icor
tical
scre
wsp
roxi
mal
lyan
d4
bico
rtic
alsc
rew
sdi
stal
ly.2
)Ten
-hol
elo
ckin
gpl
ate:
4un
icor
tical
scre
ws
prox
imal
lyan
d4
bico
rtic
alsc
rew
sdis
tally
.3)D
oubl
elo
ckin
gpl
ates
:asw
ithm
etho
d1
plus
anad
ditio
nala
nter
iore
ight
-hol
elo
ckin
gpl
ate
fixed
usin
gth
ree
unic
ortic
alsc
rew
spro
xim
ally
and
thre
ebi
cort
ical
scre
wsd
ista
lly.4
)Rev
isio
nst
em(2
01m
m):
shor
tste
mus
edin
met
hod
1–3
repl
aced
bya
201
mm
long
stem
;the
cem
entm
ante
lwas
expa
nded
med
io-la
tera
llyto
fit.5
)Re
visi
onst
em(2
01m
m)a
ndei
ght-h
ole
plat
e:as
with
met
hod
4pl
usan
addi
tiona
leig
htho
lelo
ckin
gpl
ate
fixed
prox
imal
lyw
ithth
ree
unic
ortic
alsc
rew
san
ddi
stal
lyw
ithon
eun
icor
tical
and
two
bi-c
ortic
alsc
rew
s.6)
Revi
sion
stem
(241
mm
):as
with
met
hod
4ex
cept
stem
exte
nded
by40
mm
.1–3
repr
esen
tPFF
fixat
ion
met
hods
for
Vanc
ouve
rB1
frac
ture
s,an
d4–
6fo
rVa
ncou
ver
B2.
Indi
cate
that
intr
eatm
ent
ofB1
frac
ture
s,a
sing
lelo
ckin
gpl
ate
issu
ffici
entp
rovi
ded
part
ialw
eigh
tba
ring
isfo
llow
ed.
InB2
frac
ture
s,lo
ngst
emre
visi
onan
dby
pass
ing
frac
ture
gap
bytw
ofe
mor
aldi
amet
ers
are
reco
mm
ende
d.Lo
ngst
emre
visi
onco
uld
beco
nsid
ered
inal
lcom
min
uted
B1an
dB2
frac
ture
sw
hen
cons
ider
ing
risk
ofsi
ngle
plat
efr
actu
re.
(Leo
nido
uet
al.,
2015
)Co
mpa
ring
trea
tmen
tm
etho
dsfo
rdi
ffere
ntbo
nequ
ality
–th
ree
mod
els
with
diffe
rent
cana
lthi
ckne
ssra
tio(C
TR),
repr
esen
ting
poor
,av
erag
e,an
dgo
odbo
nequ
ality
.Fu
rthe
rth
ree
mod
els
wer
ede
velo
ped
with
angl
efr
actu
res
vary
ing
from
unst
able
tran
sver
se(0
°),s
hort
obliq
ue(1
46°)
,and
stab
lelo
ngob
lique
confi
gura
tion
(76°
).Co
mpa
riso
nsw
ere
also
mad
eon
thre
edi
ffere
ntm
odel
swith
the
frac
ture
atth
etip
ofth
est
em,4
mm
,and
14m
mbe
low
the
tipof
the
stem
.
Resu
ltssu
gges
ttha
tin
good
bone
qual
ityan
dac
ute
frac
ture
angl
es,s
ingl
elo
ckin
gpl
ate
fixat
ion
can
beco
nsid
ered
asan
appr
opri
ate
man
agem
ent
met
hod.
Conv
erse
lypo
orbo
nequ
ality
and
obtu
sefr
actu
rean
gles
alte
rnat
ive
met
hods
may
bere
quir
edas
fixat
ion
mig
htbe
unde
rhi
gher
risk
offa
ilure
.Sug
gest
sth
ator
thop
aedi
csu
rgeo
nsh
ould
take
into
cons
ider
atio
nth
ePF
Fto
pogr
aphy
and
bone
qual
ityan
dno
tent
irel
yre
lyon
Vanc
ouve
rcl
assi
ficat
ion
tofo
rmul
ate
atr
eatm
ent
plan
.(A
vval
etal
.,20
16)
Inve
stig
atio
nin
tofe
mor
alde
nsity
chan
gesi
nre
spon
seto
bone
frac
ture
plat
ean
dhi
pim
plan
t;lo
ng-te
rmbe
havi
ouro
fafe
mur
inre
spon
seto
thes
eim
plan
tsan
dfix
atio
nsw
ere
sim
ulat
ed.B
one
min
eral
dens
itych
ange
sev
alua
ted
for
late
ralp
latin
gan
dan
teri
orpl
atin
g(3
unic
ortic
alsc
rew
san
d5
bico
rtic
alsc
rew
sus
ed).
Resu
ltssh
owed
that
area
sdi
rect
lyun
der
the
plat
eex
peri
ence
dse
vere
bone
loss
(Up
to~
−70
%).
Som
ele
velo
fbon
efo
rmat
ion
(~+
110%
)w
asob
serv
edin
the
vici
nity
ofth
em
ostp
roxi
mal
and
dist
alsc
rew
hole
sin
both
late
rala
ndan
teri
orpl
ated
fem
urs.
Inre
spec
tto
bone
rem
odel
ling
resp
onse
,ant
erio
rpl
atin
gis
not
supe
rior
tola
tera
lpla
ting.
(continuedon
nextpage
)
K. Wang et al. Clinical Biomechanics 61 (2019) 144–162
156
Table2
(continued)
Aut
hors
Test
case
Resu
lts
Expe
rim
enta
lstu
dies
Plat
ean
dst
rutfi
xatio
n
Late
ralp
late
fixat
ion
Stru
tfixa
tion
Prox
imal
Dis
tal
Posi
tion
Stru
tlen
gth
(mm
)Pr
oxim
alD
ista
l
Uni
cort
ical
Scre
wCa
ble/
wir
eBi
cort
ical
scre
wCa
ble/
wir
eCa
ble/
wir
e
(Wan
get
al.,
2016
)(p
)Bi
omec
hani
calp
erfo
rman
ceof
thre
edi
ffere
ntPF
Ffix
atio
nm
etho
dsfo
rVan
couv
erty
peB1
frac
ture
sin
norm
alan
dos
teop
orot
icbo
new
asex
amin
edvi
aFE
mod
el.1
)D
oubl
eci
rcle
cabl
e2)
Trad
ition
allo
ckin
gtit
aniu
mpl
ate
(LCP
)3)
Mul
tidir
ectio
nall
ocki
ngpl
ate.
Stre
ssdi
stri
butio
n,st
iffne
ss,m
axim
umst
ress
and
rela
tive
disp
lace
men
twer
eco
mpa
red
unde
rsa
me
axia
land
tors
iona
lloa
ding
usin
gFE
A.
Mul
tidir
ectio
nall
ocki
ngpl
ate
syst
emsh
owed
high
erst
abili
tyan
dst
iffne
ss,m
ore
even
stre
ssdi
stri
butio
nun
der
the
sam
eax
iala
ndto
rsio
nal
load
ing
inbo
thno
rmal
and
oste
opor
otic
bone
than
doub
leci
rcle
-cab
lean
dtr
aditi
onal
lock
ing
titan
ium
plat
efo
rVa
ncou
ver
B1pe
ripr
osth
etic
frac
ture
s.
Key
toco
nten
t:C,
cabl
e;Ce
,cer
clag
e;W
,wir
e;BC
,Bic
ortic
alsc
rew
s;LS
,Loc
king
scre
ws;
GT,
grea
ter
troc
hant
er;A
nt,a
nter
ior;
Lat,
late
ral;
Med
,med
ial.
(a)
Onl
yhi
pst
emin
sert
ed.
(b)
Dis
talr
etro
grad
efe
mor
alna
ilus
ed,t
wo
lock
ing
scre
ws
used
prox
imal
ly,a
ndon
edi
stal
.(c
)A
dditi
onal
188
mm
ante
rior
lock
ing
plat
ew
asus
ed.
(d)
Inth
isin
stan
ce5
fixed
angl
ese
lf-cu
ttin
glo
ckin
gsc
rew
sus
edto
affix
plat
eto
late
ralf
emor
alco
ndoy
le.
(e)
Inth
isin
stan
ce,b
icor
tical
scre
ws
wer
eus
edfo
rpr
oxim
alfix
atio
nin
stea
dof
unic
ortic
alsc
rew
s.(f
)Lo
ckin
gat
tach
men
tpl
ate
(LA
P)w
asus
ed,a
dditi
onal
bico
rtic
alsc
rew
sus
edfo
rpr
oxim
alfix
atio
n.(g
)In
this
inst
ance
,pro
xim
alfix
atio
nin
volv
edtw
o4
mm
vari
able
angl
esc
rew
s(V
AS)
pass
ing
the
pros
thes
isan
dtw
o5
mm
VAS
pass
ing
the
stem
,to
achi
eve
bico
rtic
alfix
atio
n.(h
)In
this
inst
ance
,tw
oin
trap
rost
hetic
scre
ws
wer
eim
plan
ted
inpl
ace
ofth
ree
unic
ortic
alsc
rew
s.(i
)In
this
inst
ance
,ort
hogo
nalp
latin
gw
asim
plem
ente
d–
two
plat
esw
ere
used
,one
plac
edla
tera
lly(w
ithLA
P)an
don
ean
teri
or.
(j)In
this
inst
ance
two
LAP
was
used
.(k
)In
this
inst
ance
,LCP
leng
thw
asm
ade
shor
t,an
d70
mm
long
segm
ents
ofca
dave
ric
fem
oral
diap
hysi
sw
asus
ed.
(l)
Inth
isin
stan
ce,t
wo
LAP
wer
eap
plie
dus
ing
2tr
ansc
ortic
allo
ckin
gsc
rew
sin
the
oute
rm
ost
hole
s.(m
)In
this
inst
ance
,dis
talfi
xatio
nal
soin
clud
ed2
cabl
esin
conj
unct
ion
with
the
bico
rtic
allo
ckin
gsc
rew
s.(n
)Aut
hord
idn'
tspe
cify
num
bero
fcer
clag
eca
bles
with
crim
pssy
stem
was
used
,but
base
don
data
avai
labl
ean
dfr
omim
ages
we
thin
k2
cabl
esfo
rpro
xim
alan
d2
ford
ista
lfixa
tion
wer
eus
edin
allo
graf
tstr
utfix
atio
n.(o
)In
this
inst
ance
,an
addi
tiona
l5ho
le-L
CPpl
ate
was
fixed
ante
rior
lyto
the
fem
urin
conj
unct
ion
with
ala
tera
lLCP
plat
e.(p
)St
udy
didn
'tsp
ecify
spec
ific
bran
dof
plat
e,bu
twe
hypo
thes
ize
that
the
trad
ition
allo
ckin
gtit
aniu
mpl
ate
isth
eLC
Ppl
ate
byD
ePuy
Synt
hes
and
Mul
tidir
ectio
nall
ocki
ngpl
ate
isth
eN
CBpl
ate
byZi
mm
er.
K. Wang et al. Clinical Biomechanics 61 (2019) 144–162
157
motion across the fracture. However, the recent literature has indicatedthat biomechanically, better plate fixation is not dependent on the ri-gidity of a structure alone (Lujan et al., 2010; Moazen et al., 2012).
Results indicate that better plate fixation can be achieved by:
1) Fixation with screws, or screws with cables, in preference to cablesand wires. (Chen et al., 2012; Graham et al., 2015; Lenz et al., 2013;Lever et al., 2010; Shah et al., 2011; Wang et al., 2016)
2) Proximal fixation using bicortical screws instead of unicortical(Gwinner et al., 2015; Hoffmann et al., 2014; Konstantinidis et al.,2010; Lenz et al., 2014; Lewis et al., 2015); or addition of a LAP orLAP-like construct (Griffiths et al., 2015; Lenz et al., 2012b, 2016a)
3) Double plating (Use of additional plate in fixation) (Choi et al.,2010; Lenz et al., 2016a; Wähnert et al., 2017); or strut (Lochabet al., 2017; Sariyilmaz et al., 2014)
4) Intraprosthetic fixation (Brand et al., 2014)5) Use of long stem revision. (Gordon et al., 2016; Moazen et al., 2014)6) Larger bridging length (Moazen et al., 2012; Walcher et al., 2016)7) Application of far cortical locking technology (Moazen et al., 2016)8) Positioning of Screws or Cable-screws (Dubov et al., 2011;
Konstantinidis et al., 2017)
Many authors reported that in cases of good bone stock (typicallyVancouver B1 type fractures), fixation with plate and screws providedmost stability. Shah et al. (2011) showed that plate-screws with addi-tional proximal cable fixation were the best choice for healthy bone; incases of osteoporotic bone, a plate without proximal holes and proximalfixation with only cables was supported. A similar result to Shah et al.(2011) was reported by Demos et al. (2012). However, Graham et al.(2015); found that when unicortical screws are used in conjunctionwith cables, results in proximal screws being pushed into the bone as itis applied, causing screw loosening fixation to the bone. Furthermore,Gordon et al. (2016) showed that osteosynthesis using plate fixationoffered no biomechanical advantages over the use of a simple cerclagesystem. They suggested that revision with a longer stem would providesuperior mechanical stability regardless of the type of osteosynthesisfixation. A similar result could be seen in the computational study byMoazen et al. (2014) who also suggested long stem revision in both B1and B2 fractures when considering the risk of single plate fracture.However, Lewis et al. (2015) found that cable constructs failed in tor-sion by the femur rotating and loosening within the cables. The con-structs also had significantly less maximum force compared to all otherconstructs in both torsional and axial loading. They found that uni-cortical, and unicortical with cable specimens tended to fail by cata-strophic fracture of the femur due to cracks typically stemming frominsertion sites of the screws. Clinically, many studies have reported thatcerclage wiring alone has a high failure rate, and proximal unicorticalscrews in dynamic compression plates, while more stable than cerclagewiring along, are also inadequate (Schwarzkopf et al., 2013).
In regards to the likehood of cement mantle failure when usingscrews; Giesinger et al. (2014) found that plate fixation of PFF usingproximal screws with a stable cemented prosthesis didn't lead to cementmantle failure. In contradiction, Kampshoff et al. (2010) found that useof screws with shortened tip, smaller flutes and double threads, showedbetter pull out resistance, but increase the risk of cement mantle failure.Bicortical screws had significantly superior construct stability and pull-out resistance when compared to unicortical screws; however bicorticalscrews also increased the risk of local cement mantle failure. Ad-ditionally, Gwinner et al. (2015) also showed that the mode of failurewas more catastrophic in proximal bicortical screw fixation; with severecomminuted fracture patterns occurring, compared to screw pull-outwith less bone damage seen in the unicortical screws group.Konstantinidis et al. (2017) showed that the probability of cementmantle damage increases significantly the closer it is to the implantedprosthesis. Direct contact of screws with cement mantle resulted inhigher incidence of cement mantle crack damage. Lever et al. (2010)
also noted that in a clinical situation; cortical screw tips could nick thelateral surface of the femoral stem, resulting in metallic wear debrisforming during daily activities. Furthermore, some of the mechanicalstiffness measured may be due to screw impingement into cement; thusslightly overestimating stiffness levels that could be achieved in vivo.
Demos et al. (2012) found that there was no difference betweenlocking screws and non-locking screws. Many studies using bicorticalscrews or a LAP construct for proximal fixation showed higher rigiditycompared to unicortical screws. However, there were contradictions;Wähnert et al. (2014) found that use of LAP did not provide the moststability as it caused a less rigid plate. Moazen et al. (2016) found thatdistal far cortical locking screws can reduce the overall effective stiff-ness of locking plates and increase fracture movement. They also foundthat the overall strength of the PFF fixation construct was maintainedwhen compared to bicortical fixation with distal locking screws. How-ever, in unstable fractures, alternative fixation methods may be a bettertreatment option.
Fracture gap and bridging length were also found to influence thestability of a fixation construct; Graham et al. (2015) found that frac-ture gap model behaves differently to the no gap model and that thedegree of fracture reduction affects whole construct stability andbending behaviour of bone. Walcher et al. (2016) showed increasedstrain with decreased over-lap or gap of the plate to stem. An FE ana-lysis of a clinical case carried out by Moazen et al. (2012) suggested thatimplementing a fracture plate with a larger bridging length may pro-mote healing compared to a plate with shorter bridging length, dis-playing the importance of plate positioning in Vancouver type C PFFfixation.
4. Discussion
A total of 30 experimental and 9 computational studies publishedsince 2010 relating to PFF were reviewed in this paper. Several ad-vancements and differences were summarised compared to past studies;however, some issues still remain. Four main issues that were high-lighted in the previous review (Moazen et al., 2011), remain important;briefly, they are as follows;
1) Lack of standardization in methods used.2) Variation in the level of sophistication in both experimental and
computational models; in experimental studies, there is typically atrade-off between accuracy and consistency. In computational stu-dies, the balance is between realism and time for development andprocessing.
3) Biomechanical studies are primarily concentrated on Vancouvertype B1 fractures. With less focus on type A and C.
4) The relationship between results presented and the clinical situationneeds to be better defined. Two main issues that are clinically im-portant are, firstly the fracture heals, and secondly, the constructdoesn't fail.
Table 1 shows that there is still a lack of standardization for testingPFF. Current experimental studies still show a lack of consistency inboth testing procedures and measurements. This makes it difficult tomake direct and conclusive comparisons between findings. Biomecha-nical testing comparing the two main plates for PFF fixation (The LCPby DePuy Synthes, and NCP by Zimmer) typically use the same NCBplates but different DePuy Synthes plates, or plates of different lengths,making it difficult to make direct comparisons between the differentstudies and plates used (Konstantinidis et al., 2010; Lever et al., 2010;Lewis et al., 2015; Wähnert et al., 2014).
Modelling of the clinical problem is not easily done because eachPFFs case is different. The best approximation to the clinical challengein either experimental or computational studies is made by taking intoaccount all different parameters that affect the clinical result. Thusmodelling appropriate anatomic region and the stability of the fracture,
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bone stock and the stability of the implant, and patients' characteristicsas demographics are the important basic requirements that we have toconsider when making the best experimental or computational study.Most of the biomechanical studies still concentrate on Vancouver typeB1 fractures, with no studies conducted on Vancouver type A; and onlyone experimental and one computational study (Walcher et al., 2016;Moazen et al., 2012;) on Vancouver type C fractures. This may be due tothe fact they are clinically less prevalent, and more easily treated(Brand et al., 2015; Capone et al., 2017; Fleischman and Chen, 2015;Lever et al., 2010). Vancouver type B2 and B3 fractures are morechallenging to conduct experimentally, with some studies using afracture gap to mimic an unstable fracture (Choi et al., 2010; Giesingeret al., 2014; Graham et al., 2015; Griffiths et al., 2015; Konstantinidiset al., 2010; Lochab et al., 2017; Sariyilmaz et al., 2014; Shah et al.,2011; Wähnert et al., 2014, 2017). However, it is important to note thatclinically, type B2 and B3 fractures are not only unstable fractures, butthe stem itself is unstable, meaning the stem has lost the connectionwith the surrounding bone and requires additional revision or treat-ment, typically with a longer stem (Schwarzkopf et al., 2013). In ad-dition, there are still several contradictions to which treatment methodis the ‘optimum’. The lack of standardization may be attributed to in-adequate understanding of treatment and differentiation betweenstable and unstable prosthesis; as failure to identify an unstable implantmay lead to treatment failure if osteosynthesis rather than revisionsurgery is performed (Schwarzkopf et al., 2013). Thus it is important toalso have biomechanical models that differentiate between stable andunstable prosthesis.
A distinct difference seen in present studies compared to older onesis the reduced use of struts and increased use of the LAP and doubleplating in the experimental studies. Of the 30 experimental studies,only three cases used struts in their biomechanical experiments. This isa stark contrast in comparison to the previous review, where of the 14experimental cases reviewed, eight studies used struts. This is in placeof the introduction and increase in testing the biomechanical perfor-mance of double plating and the use of a LAP or similar construct.Clinically, there is not much data regarding the use of the LAP, how-ever, there have been some reports of acceptable outcomes from usingan LAP to manage PFF with a well-fixed stem (Kim et al., 2017a, 2017b)or when stability of plate is insufficient (Kammerlander et al., 2013).Despite the significant decrease in the use of struts in biomechanicaltesting; clinically struts in conjunction with plate fixation are stillwidely used for PFF fixation treatment, with some studies showingpositive clinical outcomes (Barden et al., 2003; Khashan et al., 2013;Kim et al., 2017a, 2017b).
Another interesting and perhaps important development is the in-creased use of computational modelling in simulating PFF and itsfixation methods; possibly because researchers have realised the addedvalue of using this approach. The review of Moazen et al. (2011) re-ported only two computational studies; here nine cases were reviewed,ranging from simple models to more complex situations such as in-vestigating femoral density changes in response to bone fracture plateand hip implant (Avval et al., 2016), or modelling clinical cases(Moazen et al., 2012). While experimental studies remain the keycomponent of these biomechanical studies, there is no doubt in thevalue that computational studies bring to testing and evaluating effec-tive fixation methods in a greater range of fracture scenarios and morecomplex situations. Several computational studies were corroboratedagainst experimental results (Dubov et al., 2011; Ebrahimi et al., 2012;Lenz et al., 2013; Shah et al., 2011) demonstrating their validity.However, whether clinicians or researchers on the whole have con-fidence in the outcome of computational results over experimental isstill a matter of debate.
From a clinical point of view, the crucial outcome is that the frac-ture heals, return to pre-injury function, and the construct itself doesn'tfail. Much of the research has hence focused on construct stiffness; andthis is still the case in many of the present studies which highlight the
higher construct overall stiffness as the “better” fixation; this is despitestudies shown by several groups that locking plates (depending on howthey are applied) lead to overly rigid fixations that can supress callusformation (Lujan et al., 2010; Moazen et al., 2012). This can be partialsince we still do not know the overall stiffness of PFF fixations in situ,and that can be widely different to the way that they have been testedbiomechanically. An interesting development in response to this hasbeen the introduction of far cortical locking technology (Bottlang et al.,2009; Bottlang and Feist, 2011); commercially named MotionLoc, andcan be used in Zimmer NCB plates. The screws lock into the plate andbypasses the near cortex, reducing the effective stiffness of lockingplates compared to standard locking screws that are secured in bothnear and far cortices, limiting the rigidity of the fixation and supportingcallus formation. While there are some clinical data available that showsome positive results in the use of far cortical locking screws, particu-larly in distal periprosthetic femoral fractures (Bottlang et al., 2010;Ries et al., 2013; Wang et al., 2018); none, to the best of our knowledgehave reported any clinical data regarding PFF after THA specifically.
Thus more clinical data regarding the use of these new platingmethods or technologies needs to be reported to better translate andvalidate experimental and computational data. In this review, only onestudy (Moazen et al., 2016) focused on far cortical locking screws; againdemonstrating the importance of computational studies in testing morecomplex scenarios. There has been evidence of experimental andcomputational studies being translated into clinical practise; studies byGordon et al. (2016) and Moazen et al. (2014) advocated long stemrevision in cases of B1 and B2 fracture treatment; this aligns withclinical data of patients with failed B1 fracture osteosynthesis showedthat revision to a long stem provided good results (Cassidy et al., 2018;Randelli et al., 2018). Cassidy et al. (2018) suggested that revisionrather than repeat fixation, regardless of how well fixed the stem ap-pears would be optimum.
Present biomechanical studies used either cemented or uncementedhip stems; however, no studies made a no direct comparison betweenthe two and its effects on the biomechanical performance of the fixationconstruct. Thus it is difficult to say whether or not the literature for oneprosthesis implantation method can be applied to the other; conse-quently whether subsequent treatment methods derived from bio-mechanical studies where most studies used cemented prosthesis (22out of 30 experimental, and 4 out of 9 computational), can be used foruncemented and vice versa. Thus the relationship between cementedversus uncemented hip prostheses and its fixation methods needs fur-ther research in order to provide more clinically relevant data, this isparticularly paramount as the use of uncemented stems is increasing forTHA (Kim et al., 2015; Philippe et al., 2015).
It is also important to consider that clinically, there is differentbehaviour between cemented and uncemented THA. Failure is morelikely to occur in patients who underwent uncemented THA (Wyatt,2014). However, Wyatt (2014) noted that a 13-year long follow up ofTHA cases showed that there was no significant difference in revisionbetween implantation methods; suggesting the higher early revisionrate may be due to intraoperative events from an inexperienced surgicalteam. However, this contradicted the Swedish registry results, whichshow that uncemented stems are revised twice as frequently as ce-mented stems during the first five years, and that cemented stems wereten times less likely to require revision for periprosthetic fracture.
The Vancouver classification system for treating PFF was originallydeveloped for THAs with cemented femoral components (Duncan andMasri, 1995), and does not differentiate treatment between cementedand uncemented hip stems; thus raising the question of can directcomparisons for treatment of PFF to be made between cemented anduncemented prostheses. While the Vancouver classification system isreported to be reliable and valid, it is difficult to strictly apply rules fortreatment in some cases as there is no objective standard to assess thebone quality or prosthetic stability, and is an arguable drawback of theVancouver classification system (Park et al., 2011). Another caveat of
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this system is that it cannot differentiate between stable and unstableprosthesis easily, which is one of the most crucial parts of treatment.Thus it would be useful if different types of PFF models that are noteasily recognised in the clinical setting could be simulated experimen-tally and computationally.
Another critical issue that needs to be discussed is the lack of os-teoporotic bone models; in most studies, the bone quality that was si-mulated experimentally and computationally could be considerednormal healthy bone stock, and not osteoporotic bone seen in patientswith high risk of PFF; with only 3 studies using osteoporotic bonemodels, two of which did compare bone quality (Lehmann et al., 2010;Leonidou et al., 2015; Wang et al., 2016). The same issues can be raisedas to whether or not results from current biomechanical studies can betranslated into clinical cases, and thus further studies using osteoporoticbone models is required.
While these issues still exist, it is important to recognize the im-proved strides made towards understanding the underlying issues ofPFF and its treatment methods. With the increased interest in PFF,many of the current studies show a higher level of sophistication intheir methods used. This is reflected in many of the studies showingmore consideration and highlighting parameters that may affect PFFthat were not previously tested in earlier studies (Moazen et al., 2011);such as fracture gap (simulating unstable fracture), cement mantle in-tegrity, bridging length, and plate type used. Comparison of bio-mechanical performance between constructs in different situations wasalso studied (e.g. before fracture, fracture with a plate, healed fracturegap - Giesinger et al., 2014; Graham et al., 2015; Griffiths et al., 2015).The interest in improving PFF fixation has also seen the development ofnew commercially available plates specifically designed for PFF. Sev-eral studies have made comparisons on the two major plates used forPFF; the LCP and NCL plate, as well the LAP (Griffiths et al., 2015; Lenzet al., 2012b, 2016b).
5. Conclusion
This review follows our earlier review of experimental and com-putational modelling of PFF fixation (Moazen et al., 2011). While therehave been improvements in the way biomechanical testing of PFFfixation is carried out, the lack of literature to address the situationsdescribed above hinders its translation into clinical practise. In parti-cular, the optimal treatment for Vancouver type B fractures remainscontroversial with experimental data not always reflecting actions oc-curring in situ. This is primarily due to available literature; whichmainly consists of small to medium-sized heterogeneous case studiesthat offer little comparative evidence (Fleischman and Chen, 2015).With the incidence of PFF expected to rise, a consensus on biomecha-nical testing methods, and subsequent optimum treatment methodsneed to be achieved. The effect of cemented versus uncemented pros-thesis on fixation methods needs further research, as well as the de-velopment of more osteoporotic bone models. An effective method canbe seen in using experimental methods in conjunction with computa-tional methods to help bridge this gap and develop more clinically re-levant models.
Conflict of interest
The authors confirm that there is no conflict of interest in thismanuscript.
Acknowledgements
This was supported by EPSRC Doctoral Training Partnership (DTP)Case Studentship (539270/173067). The authors declare that no com-peting interests exist.
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