ma e ials
A icle
The E ec o Kinema ic Condi ions and Syno ial
Fluid Composi ion on he F ic ional Beha iou o
Ma e ials o A i icial Join s
Da id Neˇcas * ID , Ma in V bka, I an Kˇ upka and Ma in Ha l
Facul y o Mechanical Enginee ing, Ins i u e o Machine and Indus ial Design, B no Uni e si y o Technology,
Technická2896/2, 616 69 B no, Czech Republic; [email p o ec ed] (M.V.); [email p o ec ed].cz (I.K.);
[email p o ec ed] (M.H.)
*Co espondence: [email p o ec ed]; Tel.: +420-541-143-239
Recei ed: 23 Ap il 2018; Accep ed: 8 May 2018; Published: 10 May 2018


Abs ac :
The pape in oduces an expe imen al in es iga ion o ic ional beha iou o ma e ials used
o join eplacemen s. The measu emen s we e pe o med using a ball-on-disc ibome e , while ou
ma e ial combina ions we e es ed; me al-on-me al, ce amic-on-ce amic, me al-on-polye hylene, and
ce amic-on-polye hylene, espec i ely. The con ac was lub ica ed by pu e saline and a ious p o ein
solu ions. The expe imen s we e ealized a wo mean speeds equal o 5.7 mm/s and 22 mm/s and
wo slide- o- oll a ios,
−
150% and 150%. I was ound ha he implan ma e ial is he undamen al
pa ame e a ec ing ic ion. In gene al, he me al pai exhibi ed app oxima ely wo imes highe
ic ion compa ed o he ce amic. In pa icula , he ic ion in he case o he me al a ied be ween
0.3 and 0.6 while he ce amic pai exhibi ed ic ion wi hin he ange om 0.15 o 0.3 a he end o
he es . The lowes ic ion was obse ed o polye hylene while i dec eased o 0.05 unde some
condi ions. I can be also concluded ha adding p o eins o he lub ican has a posi i e impac on
ic ion in he case o ha d-on-ha d pai s. Fo ha d-on-so pai s, no subs an ial in luence o p o eins
was obse ed. The e ec o kinema ic condi ions was ound o be negligible in mos cases.
Keywo ds: join eplacemen ; ic ion; ma e ial; p o eins; kinema ic condi ions
1. In oduc ion
To al join a h oplas y is an e icien and well-es ablished su gical p ocedu e imp o ing he
li e o pa ien s su e ing om join diseases. Acco ding o he Heal h a a Glance 2015 epo [
1
],
161 ope a ions pe 100,000 inhabi an s we e pe o med in O ganisa ion o Economic Co-ope a ion and
De elopmen (OECD) coun ies in 2013. Howe e , despi e he apid imp o emen o he implan ed
ma e ials in he las ew decades [
2
], limi ed longe i y is s ill ecognized as he main d awback o
he eplacemen s. I should be highligh ed ha ailu e o he implan is accompanied by he need
o a e ising ope a ion, which is an economic bu den and subs an ially de e io a es he com o
o he pa ien . As he numbe o young ac i e people wi h a i icial join s s ill inc eases [
3
], i is
necessa y o ensu e a su icien se ice-li e o implan s o a oid any incon enience associa ed wi h i s
imp ope unc ion. Since he main cause o he ailu e is os eolysis [
4
] ollowed by asep ic loosening,
he ibological pe o mance o implan s has o be unde s ood in he con ex o he u he de elopmen
o eplacemen s.
Se e al aspec s ha e o be aken in o accoun conside ing ibological p ocesses wi hin a i icial
join con ac . Ma aki and Cann [
5
] employed a ball-on-disc con igu a ion when e alua ing he
coe icien o ic ion (CoF) as a unc ion o mean speed. Me al-on-me al con ac was in es iga ed,
while se e al es lub ican s we e es ed. In gene al, CoF was kep be ween 0.1 and 0.4 while he es
Ma e ials 2018,11, 767; doi:10.3390/ma11050767 www.mdpi.com/jou nal/ma e ials
Ma e ials 2018,11, 767 2 o 12
luid had a signi ican impac on esul s. I was ound ha bo ine se um (BS) and simple p o ein
solu ions lead o a educ ion o ic ion in a slow-speed egime. I was also highligh ed ha he choice
o bu e solu ion a ec s he lub ica ion condi ions. Finally, i was concluded ha ic ion as well as
lub ica ing ilm hickness a e ime and sliding-dis ance dependen , indica ing he impo ance o he
adso bed p o ein laye on he su aces.
One o he i s s udies which was ocused on he in luence o lub ican composi ion on ic ion
be ween polyme and me al su ac was unde aken by Yao e al. [
6
]. A pin-on-disk ibome e was
used o he e alua ion o CoF, while a ious es luids we e used as he lub ican s; pa icula ly
deionized wa e , dilu ed (25%, 50%, 75%) and undilu ed bo ine cal se um (BCS), bo ine syno ial
luid (SF) and human pe ip os he ic SF. A signi ican a iance o CoF esul s was obse ed, a ibu ed
mainly o he subs an ial changes o p o ein concen a ions and heological p ope ies o he luids.
The lowes ic ion (
≈
0.013) was exhibi ed by human SF ollowed by deionized wa e . Rema kably,
highe ic ion was de ec ed o bo ine SF and undilu ed BCS (
≈
0.024). The highes CoF was de ec ed
o 25% BCS, which was a ound 0.028. Scholes and Unswo h [
7
] demons a ed he impo ance o
lub ican composi ion in ela ion o he ma e ial combina ion o he implan s. The au ho s es ed
a ious model luids inding ha he highes ic ion can be de ec ed in he case o me al-me al implan s.
No signi ican di e ence be ween he ce amic-ce amic and me al-polye hylene pai was obse ed.
Al hough he e was a apid in luence o he model luid on he CoF, he e ec o p o eins could no
be gene alized, since bo h dec ease and inc ease o ic ion could be obse ed dependen on implan
ma e ial. The ole o indi idual cons i uen s con ained in SF was demons a ed by Sawae e al. [
8
].
The con ac be ween an ul a-high molecula weigh polye hylene (UHMWPE) pin sliding agains
me al/ce amic disc was s udied, while a clea posi i e e ec o hyalu onic acid added o saline solu ion
on ic ion was de ec ed.
Mo eo e , i was well epo ed ha he ic ional beha iou o he con ac pai is subs an ially
in luenced by he su ace condi ions. Widme e al. [
9
], in es iga ed he ce amic-polye hylene sliding
pai , inding ha he oxygen-plasma based ea men o polye hylene (PE) led o imp o ed abili ies o
p o ein adso p ion on o ubbing su aces, hus educing bo h s a ic and dynamic ic ion. Subsequen ly,
i was poin ed ou ha con o ma ional changes ha e o be aken in o accoun [
10
]. The au ho s
showed ha hyd ophilic na u e o he su aces suppo s adso p ion o he p o eins in a na i e s a e,
o ming hicke lub ica ing ilm leading o lowe ic ion be ween he componen s. An ex ensi e
in es iga ion o he e ec o model luid composi ion on CoF dependen on kinema ic condi ions was
p o ided in ou p e ious s udy [
11
]. Recip oca ing pin-on-pla e (me al-UHMWPE) es was conduc ed,
showing ha he kinema ic condi ions ha e a c ucial impac on he con o ma ional changes o p o eins,
hus in luencing ic ional beha iou o he con ac pai . A a slow speed egime (10 mm/s), a e y
sligh inc ease o ic ion wi h inc easing p o ein concen a ion was obse ed o bo h albumin and
γ
-globulin solu ion. The highes ic ion occu ed when a mix u e o he men ioned p o eins was
used as he es lub ican . An inc ease o sliding speed o 50 mm/s caused jus a negligible change o
ic ion. Independen o sliding speed, CoF was subs an ially highe when compa ing p o ein solu ions
(
≈
0.17–0.27) wi h phospha e-bu e ed saline (PBS) wi hou any cons i uen s. In ha case, ic ion was
lowe han 0.05. These esul s a e in good ag eemen wi h he obse a ion p o ided p e iously [
12
,
13
].
In he s udy men ioned, he e ec o albumin unde going con o ma ional changes on he ic ion
be ween he UHMWPE pin and s ainless s eel pla e was e alua ed. A subs an ial e ec o he applied
load on he esul s was obse ed; while a low loads, pos - ic ion deg aded albumin added o PBS led
o a dec ease o ic ion compa ed o esh p o ein. The opposi e beha iou occu ed a highe loads.
Based on he abo e e e ences [
11
,
12
], i can be concluded ha ic ion be ween he ubbing su aces is
a ec ed by bo h kinema ic and loading condi ions.
The e ec o eplacemen geome y has o be aken in o accoun as well. Dowson e al. [
14
]
conduc ed a p edic i e nume ical analysis o ic ion and wea o me al-me al implan , inding ha
he ic ional o que inc eases wi h inc easing nominal diame e ; howe e , i is a ec ed jus a li le by
he ini ial clea ance be ween he su aces. An expe imen al s udy o he e ec o diame ic clea ance
Ma e ials 2018,11, 767 3 o 12
oge he wi h he ole o model luid was unde aken by B ocke e al. [
15
]. Nominal diame e o he
implan was 54.6 mm, while h ee di e en clea ances we e conside ed; 53
µ
m, 94
µ
m, and 194
µ
m,
espec i ely. The lowes ic ion ac o was de ec ed o he medium size o he clea ance. Lowe ing
he clea ance led o a negligible inc ease o ic ion; howe e , in he case o he highes clea ance,
a subs an ial inc ease o ic ion o almos double was de ec ed. Rega ding he model luid, 25% and
100% BS we e es ed, wi h he inding ha lowe ic ion could be eached in he case o highe p o ein
concen a ion, in gene al, which is in a good ag eemen wi h one o he p e ious s udies [
6
]. Finally,
an expe imen al in es iga ion o he ic ion coe icien using a pendulum hip join simula o ocusing
on he e ec o implan ma e ial and diame e was conduc ed by V bka e al. [
16
]. This applied
25% BS o a o al p o ein concen a ion o 22.4 mg/mL, es ing 28 mm and 36 mm me al-UHMWPE,
ce amic-UHMWPE and ce amic-ce amic pai s. The highes CoF (
≈
0.16) was de ec ed in he case o he
me al-UHMWPE pai wi h no clea e ec o nominal diame e . Ce amic-UHMWPE exhibi ed lowe
ic ion (
≈
0.14), while a la ge diame e led o a u he dec ease (
≈
0.13). The lowes ic ion (0.12)
was de ec ed in he ce amic-ce amic pai wi h he same e ec o diame e as in he p e ious case.
Based on he abo e e e ences, i is appa en ha he ibological beha iou o a i icial join s
is in luenced by se e al aspec s, such as composi ion o he model SF, implan ma e ial, geome y,
kinema ic and loading condi ions. Howe e , mos o he au ho s ocused on one pa icula ma e ial
combina ion o speci ic composi ion o he es lub ican . The e o e, he aim o he p esen pape is o
p o ide a de ailed analysis o ic ional beha iou conside ing a ious implan ma e ials, kinema ic
condi ions, and he composi ion o model syno ial luid. Acco ding o he au ho s’ bes knowledge,
such an ex ensi e in es iga ion has no been pe o med be o e.
2. Ma e ials and Me hods
The measu emen s o he CoF we e conduc ed u ilizing a comme cial ball-on-disc es de ice
Mini T ac ion Machine (MTM, PCS Ins umen s, London, Uni ed Kingdom). Bo h he componen s, he
ball and he disc, could be d i en independen ly, hus enabling he applica ion o a ious kinema ic
condi ions. The mean dynamic (some imes also called kine ic o sliding) ic ion coe icien [
17
]
is e alua ed based on he a io o ic ion and no mal o ce measu ed by he load cell. CoF was
e alua ed wi h he acquisi ion equency o 0.1 Hz. A con ac pai consis ed o me al (cobal -ch omium-
molybdenum—CoC Mo) and alumina ce amic balls o diame e 19.05 mm sliding agains 46 mm-
diame e discs o me al, ce amic, and highly-c osslinked PE (HXPE), espec i ely. The hickness o he
discs was 6 mm. A schema ic illus a ion o he measu emen con igu a ion is displayed in Figu e 1.
Ini ial su ace opog aphy o he es specimens was checked using he phase-shi ing in e e ome y
me hod (Con ou GT-X8, B uke , Bille ica, MA, USA). Fi e poin s which we e expec ed o be in he
con ac d ag o each sample we e measu ed, while he su ace oughness esul s a e shown in Table 1.
To cla i y he e ec o kinema ic condi ions, he expe imen s we e ealized unde wo di e en
mean speeds, 5.7 mm/s and 22 mm/s. Mean speed ep esen s he a e age alue o he ball and he disc
speed unde a ious olling/sliding condi ions. In he ollowing ex , he e ms posi i e and nega i e
sliding a e used. In he case o nega i e sliding, he ball o a es as e han he disc. By con as , unde
posi i e sliding he disc is as e . The cou se o he speeds o he indi idual componen s conside ing
nega i e and posi i e sliding is demons a ed using he ed a ows in he bo om pa o Figu e 1.
Rega ding he human body, i can be assumed ha he hip join ope a es unde pu e nega i e sliding
condi ions, which means ha he cup is s a iona y, while he head o a es. Conside ing he ball-on-disc
con igu a ion, pu e sliding ep esen s bi se e e condi ions and so signi ican wea o he samples
appa en ly in luencing he esul s o CoF could be expec ed. The e o e, he expe imen s we e ealized
unde pa ial sliding o 150%. To a oid inaccu acies coming om he slippage o he componen s,
he es s we e ealized unde bo h posi i e (150%) and nega i e (
−
150%) sliding. The slide- o- oll
a io (SRR) which de e mines he le el o slip, can be easily de e mined ollowing he equa ion
SRR = 2(u
D−
u
B
)/(u
D
+ u
B
), whe e u
d
is he speed o he disc and u
b
is he speed o he ball. Combined
olling/sliding condi ions no mally occu in he knee join ; howe e , i should be highligh ed ha he
Ma e ials 2018,11, 767 4 o 12
p esen s udy is no ocused on one pa icula join ype, bu on he gene al assessmen o ic ional
beha iou o ma e ials used o join implan s. Applied load was 0.5 N in he case o he me al and 0.4
in he case o he ce amic balls, leading o he ollowing con ac p essu es: me al-on-me al (264.7 MPa),
me al-HXPE (9.9 MPa), ce amic-ce amic (280.5 MPa), ce amic-HXPE (9.5 MPa).
Ma e ials 2018, 11, x FOR PEER REVIEW 4 o 12
howe e , i should be highligh ed ha he p esen s udy is no ocused on one pa icula join ype,
bu on he gene al assessmen o ic ional beha iou o ma e ials used o join implan s. Applied
load was 0.5 N in he case o he me al and 0.4 in he case o he ce amic balls, leading o he
ollowing con ac p essu es: me al-on-me al (264.7 MPa), me al-HXPE (9.9 MPa), ce amic-ce amic
(280.5 MPa), ce amic-HXPE (9.5 MPa).
Figu e 1. Schema ic illus a ion o he measu emen con igu a ion.
Table 1. Su ace opog aphy pa ame e s o he es samples.
Pa ame e Ball Disc
- Me al Ce amic Me al Ce amic HXPE
A e age su ace oughness Ra (μm) 0.087 0.035 0.008 0.998 0.841
S anda d de ia ion SD (μm) ±0.00587 ±0.00414 ±0.00039 ±0.10707 ±0.13631
The main in e es o he cu en s udy was in he e ec o he composi ion o model luid.
The e o e, i e es lub ican s we e p epa ed while he esul s we e compa ed wi h hose o pu e
PBS. The model luids con ained he dominan p o eins o SF; albumin and γ-globulin, espec i ely.
Lub ican s we e p epa ed 24 h p io o he es s and we e s o ed in a e ige a o o enable a
comple e solu ion o he p o eins in PBS. Bo ine se um albumin (9048-46-8, Biomol GmbH,
Hambu g, Ge many) and γ-globulin om human blood (G4386, Sigma Ald ich, Da ms ad ,
Ge many) we e added o PBS in a ious concen a ions, while he simple p o ein solu ions we e
in es iga ed as well. A summa y o he es luids is p o ided in Table 2. Despi e he abili y o he
es de ice o con ol he empe a u e o he po , he expe imen s we e ealized unde ambien
labo a o y empe a u e o 22 °C, since i was p e iously e e enced in li e a u e ha he inc ease o
body empe a u e does no in luence he esul s subs an ially [18]. The expe imen s we e conduc ed
unde ully looded condi ions o a oid any e ec s coming om s a a ion o he con ac . Eigh y
expe imen s we e ealized in o al, while Table 3 p o ides he comple e o e iew o he pe o med
es s o be e o ien a ion. The de ailed in o ma ion abou he speeds o he ball and he disc du ing
a ious es s is gi en in Table 4. Random es s we e conduc ed h ee imes o check he epea abili y
o he esul s. Since he e was excellen da a ag eemen in e ms o bo h he ends and he absolu e
alues o CoF (s anda d de ia ion no la ge han 0.04), he es o he expe imen s we e pe o med
only once.
Figu e 1. Schema ic illus a ion o he measu emen con igu a ion.
Table 1. Su ace opog aphy pa ame e s o he es samples.
Pa ame e Ball Disc
- Me al Ce amic Me al Ce amic HXPE
A e age su ace oughness Ra (µm) 0.087 0.035 0.008 0.998 0.841
S anda d de ia ion SD (µm) ±0.00587 ±0.00414 ±0.00039 ±0.10707 ±0.13631
The main in e es o he cu en s udy was in he e ec o he composi ion o model luid.
The e o e, i e es lub ican s we e p epa ed while he esul s we e compa ed wi h hose o pu e
PBS. The model luids con ained he dominan p o eins o SF; albumin and
γ
-globulin, espec i ely.
Lub ican s we e p epa ed 24 h p io o he es s and we e s o ed in a e ige a o o enable a comple e
solu ion o he p o eins in PBS. Bo ine se um albumin (9048-46-8, Biomol GmbH, Hambu g, Ge many)
and
γ
-globulin om human blood (G4386, Sigma Ald ich, Da ms ad , Ge many) we e added o PBS
in a ious concen a ions, while he simple p o ein solu ions we e in es iga ed as well. A summa y o
he es luids is p o ided in Table 2. Despi e he abili y o he es de ice o con ol he empe a u e
o he po , he expe imen s we e ealized unde ambien labo a o y empe a u e o 22
◦
C, since i
was p e iously e e enced in li e a u e ha he inc ease o body empe a u e does no in luence he
esul s subs an ially [
18
]. The expe imen s we e conduc ed unde ully looded condi ions o a oid
any e ec s coming om s a a ion o he con ac . Eigh y expe imen s we e ealized in o al, while
Table 3p o ides he comple e o e iew o he pe o med es s o be e o ien a ion. The de ailed
in o ma ion abou he speeds o he ball and he disc du ing a ious es s is gi en in Table 4. Random
es s we e conduc ed h ee imes o check he epea abili y o he esul s. Since he e was excellen
da a ag eemen in e ms o bo h he ends and he absolu e alues o CoF (s anda d de ia ion no
la ge han 0.04), he es o he expe imen s we e pe o med only once.
Ma e ials 2018,11, 767 5 o 12
Table 2. Summa y o he applied model luids.
Model Syno ial
Fluid (MSF) Volume (mL) P o ein Con en (mg/mL) To al P o ein
Concen a ion (mg/mL)
- - Albumin γ-globulin -
Alb70+Glob35 10 7 3.5 10.5
Alb35+Glob70 10 3.5 7 10.5
Alb140+Glob70 10 14 7 21
Albumin70 10 7 - 7
γ-globulin35 10 - 3.5 3.5
PBS 10 - - -
Table 3. O e iew o he pe o med expe imen s.
Expe imen Se Ma e ial Combina ion Mean Speed
(mm/s)
Slide-To-Roll
Ra io (%) Model Syno ial Fluid
1Me al-on-Me al
(MoM) 5.7; 22 150; −150
Alb70+Glob35;
Alb35+Glob70;
Alb140+Glob70; PBS
2
Me al-on-highly c osslinked
polye hylene (HXPE)
(MoP)
5.7; 22 150; −150
Alb70+Glob35;
Alb35+Glob70;
Alb140+Glob70; PBS
3Ce amic-on-Ce amic
(CoC) 5.7; 22 150; −150
Alb70+Glob35;
Alb35+Glob70;
Alb140+Glob70; PBS
4Ce amic-on-HXPE
(CoP) 5.7; 22 150; −150
Alb70+Glob35;
Alb35+Glob70;
Alb140+Glob70; PBS
5 MoM 22 150; −150 Albumin70;
γ-globulin35
6 MoP 22 150; −150 Albumin70;
γ-globulin35
7 CoC 22 150; −150 Albumin70;
γ-globulin35
8 CoP 22 150; −150 Albumin70;
γ-globulin35
Table 4. A de ailed o e iew o he kinema ic condi ions.
Slide-To-Roll Ra io (%) Mean Speed (mm/s) Ball Speed (mm/s) Disc Speed (mm/s)
−150 5.7 9.975 1.425
−150 22 38.5 5.5
150 5.7 1.425 9.975
150 22 5.5 38.5
3. Resul s and Discussion
3.1. The E ec o Ma e ial and Kinema ic Condi ions
Ini ially, he expe imen s we e pe o med wi h pu e PBS o all he ma e ial combina ions,
conside ing bo h posi i e and nega i e sliding a lowe (5.7 mm/s) and highe (22 mm/s) speed.
The esul s showed ha independen o kinema ic condi ions, he MoM combina ion exhibi s he
highes ic ion; howe e , his e ec was signi ican mainly unde nega i e sliding, when he ic ion
a he end o he expe imen eached almos 0.6. By con as , he lowes ic ion was de ec ed o
MoP and CoP, while in he case o CoP, he ic ion le el was less han 0.1, pa icula ly a ound
0.05 o he dominan pe iod o he expe imen s, which is in a good co ela ion wi h p e ious
obse a ions [
11
,
19
,
20
]. CoC ic ional beha iou was ound o be somewhe e be ween, while he
ic ion eached abou 0.25. Ne e heless, i should be aken in o accoun ha he su ace oughness o

Ma e ials 2018,11, 767 6 o 12
he employed ce amic disc was an o de o magni ude highe han he su ace o he ball, which could
a ec he esul s. Based on he p e ious indings, i migh be expec ed ha i ealis ic oughness o he
disc could be achie ed, he ic ion coe icien would be lowe . Howe e , wi hou he expe imen al
esul s, he po en ial le el o CoF educ ion can be only es ima ed. Ne e heless, i should be
emphasized ha he p esen s udy is a he compa a i e, no p edic ing he ic ion wi hin eal
implan s. Wi h he excep ion o MoM unde posi i e sliding condi ions, he e was no a subs an ial
e ec o speed. Conside ing he e ec o ime, only in he case o MoM was he de elopmen o ic ion
wi h ime obse ed. Fo he es o he ma e ial combina ions, CoF was s able wi hou any luc ua ions
o e he en i e expe imen . All he esul s can be seen in Figu e 2. I should be no ed ha e en he
acquisi ion equency was 0.1 Hz; o be e cla i y o he esul s, he plo ed do s ep esen a e age
CoF in pa icula ime s eps (1 s, 15 s, 30 s
. . .
300 s). The inse igu es a e shown o illus a e he
kinema ic condi ions. The ed a ows ep esen he speed cou se.
Ma e ials 2018, 11, x FOR PEER REVIEW 6 o 12
could be achie ed, he ic ion coe icien would be lowe . Howe e , wi hou he expe imen al
esul s, he po en ial le el o CoF educ ion can be only es ima ed. Ne e heless, i should be
emphasized ha he p esen s udy is a he compa a i e, no p edic ing he ic ion wi hin eal
implan s. Wi h he excep ion o MoM unde posi i e sliding condi ions, he e was no a subs an ial
e ec o speed. Conside ing he e ec o ime, only in he case o MoM was he de elopmen o
ic ion wi h ime obse ed. Fo he es o he ma e ial combina ions, CoF was s able wi hou any
luc ua ions o e he en i e expe imen . All he esul s can be seen in Figu e 2. I should be no ed
ha e en he acquisi ion equency was 0.1 Hz; o be e cla i y o he esul s, he plo ed do s
ep esen a e age CoF in pa icula ime s eps (1 s, 15 s, 30 s … 300 s). The inse igu es a e shown o
illus a e he kinema ic condi ions. The ed a ows ep esen he speed cou se.
Figu e 2. De elopmen o coe icien o ic ion (CoF) as a unc ion o ime o ou ma e ial
combina ions a lowe and highe mean speed unde nega i e (a) and posi i e (b) sliding condi ions.
Con ac is lub ica ed by phospha e-bu e ed saline (PBS).
Adding he p o eins in o he saline solu ion in ela i ely low concen a ion (10.5 mg/mL in
o al) led o a sligh change o CoF e olu ion, see Figu es 3 and 4 Compa ed o he pu e PBS esul s,
ime-dependen beha iou was obse ed o MoM and also o CoC con ac pai s, while he
maximum a he end o he es was om 0.3 o 0.4 o me al. Fo ce amic, he ic ion le el was abou
0.2, while he e y same beha iou was obse ed in li e a u e, whe e he con ac o a ce amic ball
sliding agains a ce amic pla e lub ica ed by BS was analyzed [21]. To de e mine he in luence o
luid composi ion, i can be seen ha e en i he concen a ion o albumin and γ-globulin was
swi ched, see Figu e 3 s. Figu e 4, almos he same esul s could be ob ained o mos o he
ma e ials and kinema ic condi ions. Only in he case o MoP did highe con en o γ-globulin lead o
a dec ease o ic ion, as can be seen in Figu e 4a.
Figu e 3. De elopmen o CoF as a unc ion o ime o ou ma e ial combina ions a lowe and
highe mean speed unde nega i e (a) and posi i e (b) sliding condi ions. Con ac is lub ica ed by
model luid Alb70+Glob35.
Figu e 2.
De elopmen o coe icien o ic ion (CoF) as a unc ion o ime o ou ma e ial
combina ions a lowe and highe mean speed unde nega i e (
a
) and posi i e (
b
) sliding condi ions.
Con ac is lub ica ed by phospha e-bu e ed saline (PBS).
Adding he p o eins in o he saline solu ion in ela i ely low concen a ion (10.5 mg/mL in
o al) led o a sligh change o CoF e olu ion, see Figu es 3and 4Compa ed o he pu e PBS esul s,
ime-dependen beha iou was obse ed o MoM and also o CoC con ac pai s, while he maximum
a he end o he es was om 0.3 o 0.4 o me al. Fo ce amic, he ic ion le el was abou 0.2, while he
e y same beha iou was obse ed in li e a u e, whe e he con ac o a ce amic ball sliding agains a
ce amic pla e lub ica ed by BS was analyzed [
21
]. To de e mine he in luence o luid composi ion, i
can be seen ha e en i he concen a ion o albumin and
γ
-globulin was swi ched, see Figu e 3 s.
Figu e 4, almos he same esul s could be ob ained o mos o he ma e ials and kinema ic condi ions.
Only in he case o MoP did highe con en o
γ
-globulin lead o a dec ease o ic ion, as can be seen
in Figu e 4a.
Ma e ials 2018, 11, x FOR PEER REVIEW 6 o 12
could be achie ed, he ic ion coe icien would be lowe . Howe e , wi hou he expe imen al
esul s, he po en ial le el o CoF educ ion can be only es ima ed. Ne e heless, i should be
emphasized ha he p esen s udy is a he compa a i e, no p edic ing he ic ion wi hin eal
implan s. Wi h he excep ion o MoM unde posi i e sliding condi ions, he e was no a subs an ial
e ec o speed. Conside ing he e ec o ime, only in he case o MoM was he de elopmen o
ic ion wi h ime obse ed. Fo he es o he ma e ial combina ions, CoF was s able wi hou any
luc ua ions o e he en i e expe imen . All he esul s can be seen in Figu e 2. I should be no ed
ha e en he acquisi ion equency was 0.1 Hz; o be e cla i y o he esul s, he plo ed do s
ep esen a e age CoF in pa icula ime s eps (1 s, 15 s, 30 s … 300 s). The inse igu es a e shown o
illus a e he kinema ic condi ions. The ed a ows ep esen he speed cou se.
Figu e 2. De elopmen o coe icien o ic ion (CoF) as a unc ion o ime o ou ma e ial
combina ions a lowe and highe mean speed unde nega i e (a) and posi i e (b) sliding condi ions.
Con ac is lub ica ed by phospha e-bu e ed saline (PBS).
Adding he p o eins in o he saline solu ion in ela i ely low concen a ion (10.5 mg/mL in
o al) led o a sligh change o CoF e olu ion, see Figu es 3 and 4 Compa ed o he pu e PBS esul s,
ime-dependen beha iou was obse ed o MoM and also o CoC con ac pai s, while he
maximum a he end o he es was om 0.3 o 0.4 o me al. Fo ce amic, he ic ion le el was abou
0.2, while he e y same beha iou was obse ed in li e a u e, whe e he con ac o a ce amic ball
sliding agains a ce amic pla e lub ica ed by BS was analyzed [21]. To de e mine he in luence o
luid composi ion, i can be seen ha e en i he concen a ion o albumin and γ-globulin was
swi ched, see Figu e 3 s. Figu e 4, almos he same esul s could be ob ained o mos o he
ma e ials and kinema ic condi ions. Only in he case o MoP did highe con en o γ-globulin lead o
a dec ease o ic ion, as can be seen in Figu e 4a.
Figu e 3. De elopmen o CoF as a unc ion o ime o ou ma e ial combina ions a lowe and
highe mean speed unde nega i e (a) and posi i e (b) sliding condi ions. Con ac is lub ica ed by
model luid Alb70+Glob35.
Figu e 3.
De elopmen o CoF as a unc ion o ime o ou ma e ial combina ions a lowe and highe
mean speed unde nega i e (
a
) and posi i e (
b
) sliding condi ions. Con ac is lub ica ed by model luid
Alb70+Glob35.
Ma e ials 2018,11, 767 7 o 12
Ma e ials 2018, 11, x FOR PEER REVIEW 7 o 12
Figu e 4. De elopmen o CoF as a unc ion o ime o ou ma e ial combina ions a lowe and
highe mean speed unde nega i e (a) and posi i e (b) sliding condi ions. Con ac is lub ica ed by
model luid Alb35+Glob70.
An inc ease o p o ein concen a ion o 21 mg/mL led o a e y sligh inc ease o ic ion o
ce amic and me al pai s. In he case o MoP and CoP, he ic ion emained he same o dec eased a
li le bi . Howe e , since he change is negligible, see Figu es 3 and 4 s. Figu e 5, i can be concluded
ha he p o ein con en does no play an impo an ole ega ding hese so-called ha d-on-so
bea ing pai s. Finally, ocusing on he pa icula ma e ial combina ions, i can be seen ha he
beha iou co esponds well o he pu e PBS esul s, while he highes ic ion is exhibi ed by MoM,
ollowed by CoC, MoP and CoP (Figu es 2–5). The highes ic ion in he case o me al-me al con ac
was epo ed also by Scholes and Unswo h [7]. Ne e heless, i should be no ed ha he esul s do
no comple ely co espond o obse a ions p o ided by V bka e al. [16], who de e mined he
ic ion coe icien o a ious implan pai s. In he e e ence, he au ho s measu ed he lowes
ic ion when conside ing a ce amic head sliding agains a ce amic cup. Howe e , i mus be no ed
ha di e en expe imen al condi ions we e employed; in pa icula , BS was employed as he es
lub ican , and he expe imen s we e ealized in di e en geome ical con igu a ions. Mo eo e , as
men ioned abo e, he oughness o ce amic discs used in he p esen s udy was an o de o magni ude
highe han is he oughness o eal ace abula cups, which can also play a signi ican ole.
Figu e 5. De elopmen o CoF as a unc ion o ime o ou ma e ial combina ions a lowe and
highe mean speed unde nega i e (a) and posi i e (b) sliding condi ions. Con ac is lub ica ed by
model luid Alb140+Glob70.
3.2. The E ec o Model Syno ial Fluid Composi ion
To clea ly iden i y he e ec o model SF composi ion on ic ional beha iou , he addi ional
es s we e pe o med a highe speed conside ing he simple p o ein solu ions o albumin and
γ-globulin as well. The esul s o indi idual ma e ial combina ions a e displayed in Figu es 6–9,
espec i ely. Fo MoM con ac , i can be seen ha he esul s o pu e PBS a e in luenced by he
posi i i y/nega i i y o sliding. Unde nega i e sliding, he le el o ic ion is conside ably highe
(a ound 0.6 a maximum) o PBS compa ed o p o ein solu ion (a ound 0.4). In e ms o indi idual
luids, albumin-con aining lub ican exhibi ed he lowes ic ion, app oxima ely 0.37. Fo he es o
he lub ican s, he e is no clea impac on lub ica ion, while he ic ion is kep be ween 0.4 and 0.43
Figu e 4.
De elopmen o CoF as a unc ion o ime o ou ma e ial combina ions a lowe and highe
mean speed unde nega i e (
a
) and posi i e (
b
) sliding condi ions. Con ac is lub ica ed by model luid
Alb35+Glob70.
An inc ease o p o ein concen a ion o 21 mg/mL led o a e y sligh inc ease o ic ion o
ce amic and me al pai s. In he case o MoP and CoP, he ic ion emained he same o dec eased a
li le bi . Howe e , since he change is negligible, see Figu es 3and 4 s. Figu e 5, i can be concluded
ha he p o ein con en does no play an impo an ole ega ding hese so-called ha d-on-so bea ing
pai s. Finally, ocusing on he pa icula ma e ial combina ions, i can be seen ha he beha iou
co esponds well o he pu e PBS esul s, while he highes ic ion is exhibi ed by MoM, ollowed by
CoC, MoP and CoP (Figu es 2–5). The highes ic ion in he case o me al-me al con ac was epo ed
also by Scholes and Unswo h [
7
]. Ne e heless, i should be no ed ha he esul s do no comple ely
co espond o obse a ions p o ided by V bka e al. [
16
], who de e mined he ic ion coe icien o
a ious implan pai s. In he e e ence, he au ho s measu ed he lowes ic ion when conside ing a
ce amic head sliding agains a ce amic cup. Howe e , i mus be no ed ha di e en expe imen al
condi ions we e employed; in pa icula , BS was employed as he es lub ican , and he expe imen s
we e ealized in di e en geome ical con igu a ions. Mo eo e , as men ioned abo e, he oughness o
ce amic discs used in he p esen s udy was an o de o magni ude highe han is he oughness o eal
ace abula cups, which can also play a signi ican ole.
Ma e ials 2018, 11, x FOR PEER REVIEW 7 o 12
Figu e 4. De elopmen o CoF as a unc ion o ime o ou ma e ial combina ions a lowe and
highe mean speed unde nega i e (a) and posi i e (b) sliding condi ions. Con ac is lub ica ed by
model luid Alb35+Glob70.
An inc ease o p o ein concen a ion o 21 mg/mL led o a e y sligh inc ease o ic ion o
ce amic and me al pai s. In he case o MoP and CoP, he ic ion emained he same o dec eased a
li le bi . Howe e , since he change is negligible, see Figu es 3 and 4 s. Figu e 5, i can be concluded
ha he p o ein con en does no play an impo an ole ega ding hese so-called ha d-on-so
bea ing pai s. Finally, ocusing on he pa icula ma e ial combina ions, i can be seen ha he
beha iou co esponds well o he pu e PBS esul s, while he highes ic ion is exhibi ed by MoM,
ollowed by CoC, MoP and CoP (Figu es 2–5). The highes ic ion in he case o me al-me al con ac
was epo ed also by Scholes and Unswo h [7]. Ne e heless, i should be no ed ha he esul s do
no comple ely co espond o obse a ions p o ided by V bka e al. [16], who de e mined he
ic ion coe icien o a ious implan pai s. In he e e ence, he au ho s measu ed he lowes
ic ion when conside ing a ce amic head sliding agains a ce amic cup. Howe e , i mus be no ed
ha di e en expe imen al condi ions we e employed; in pa icula , BS was employed as he es
lub ican , and he expe imen s we e ealized in di e en geome ical con igu a ions. Mo eo e , as
men ioned abo e, he oughness o ce amic discs used in he p esen s udy was an o de o magni ude
highe han is he oughness o eal ace abula cups, which can also play a signi ican ole.
Figu e 5. De elopmen o CoF as a unc ion o ime o ou ma e ial combina ions a lowe and
highe mean speed unde nega i e (a) and posi i e (b) sliding condi ions. Con ac is lub ica ed by
model luid Alb140+Glob70.
3.2. The E ec o Model Syno ial Fluid Composi ion
To clea ly iden i y he e ec o model SF composi ion on ic ional beha iou , he addi ional
es s we e pe o med a highe speed conside ing he simple p o ein solu ions o albumin and
γ-globulin as well. The esul s o indi idual ma e ial combina ions a e displayed in Figu es 6–9,
espec i ely. Fo MoM con ac , i can be seen ha he esul s o pu e PBS a e in luenced by he
posi i i y/nega i i y o sliding. Unde nega i e sliding, he le el o ic ion is conside ably highe
(a ound 0.6 a maximum) o PBS compa ed o p o ein solu ion (a ound 0.4). In e ms o indi idual
luids, albumin-con aining lub ican exhibi ed he lowes ic ion, app oxima ely 0.37. Fo he es o
he lub ican s, he e is no clea impac on lub ica ion, while he ic ion is kep be ween 0.4 and 0.43
Figu e 5.
De elopmen o CoF as a unc ion o ime o ou ma e ial combina ions a lowe and highe
mean speed unde nega i e (
a
) and posi i e (
b
) sliding condi ions. Con ac is lub ica ed by model luid
Alb140+Glob70.
3.2. The E ec o Model Syno ial Fluid Composi ion
To clea ly iden i y he e ec o model SF composi ion on ic ional beha iou , he addi ional es s
we e pe o med a highe speed conside ing he simple p o ein solu ions o albumin and
γ
-globulin
as well. The esul s o indi idual ma e ial combina ions a e displayed in Figu es 6–9, espec i ely.
Fo MoM con ac , i can be seen ha he esul s o pu e PBS a e in luenced by he posi i i y/nega i i y
o sliding. Unde nega i e sliding, he le el o ic ion is conside ably highe (a ound 0.6 a maximum)
o PBS compa ed o p o ein solu ion (a ound 0.4). In e ms o indi idual luids, albumin-con aining
lub ican exhibi ed he lowes ic ion, app oxima ely 0.37. Fo he es o he lub ican s, he e is
Ma e ials 2018,11, 767 8 o 12
no clea impac on lub ica ion, while he ic ion is kep be ween 0.4 and 0.43 a he end o he es ,
see Figu e 6a. Conside ing he posi i e sliding condi ions, he CoF de elopmen is sligh ly di e en .
The highes ic ion o e he dominan pa o he expe imen was exhibi ed by he solu ion wi h
ela i ely high p o ein con en . Howe e , a e 75 s, he ic ion was s abilized a abou 0.4 wi hou any
u he ime-dependen change. The cou se o ic ion o saline solu ion is linea ly inc easing ( he
same beha iou as unde nega i e sliding), eaching 0.45 a he end. Fo he o he p o ein solu ions,
he beha iou is almos he same, wi h he excep ion o lub ican con aining 70 mg/mL o albumin
and 35 mg/mL o
γ
-globulin, which exhibi s he lowes ic ion. This can be a ibu ed o he ac ion o
he p o ein ilm. I was obse ed in li e a u e ha , conside ing he same model luid as in he case o
he p esen s udy, a me al head o med much hicke p o ein ilm unde posi i e sliding, which can
lead o a dec ease o ic ion be ween he su aces [22].
Ma e ials 2018, 11, x FOR PEER REVIEW 8 o 12
a he end o he es , see Figu e 6a. Conside ing he posi i e sliding condi ions, he CoF
de elopmen is sligh ly di e en . The highes ic ion o e he dominan pa o he expe imen was
exhibi ed by he solu ion wi h ela i ely high p o ein con en . Howe e , a e 75 s, he ic ion was
s abilized a abou 0.4 wi hou any u he ime-dependen change. The cou se o ic ion o saline
solu ion is linea ly inc easing ( he same beha iou as unde nega i e sliding), eaching 0.45 a he
end. Fo he o he p o ein solu ions, he beha iou is almos he same, wi h he excep ion o
lub ican con aining 70 mg/mL o albumin and 35 mg/mL o γ-globulin, which exhibi s he lowes
ic ion. This can be a ibu ed o he ac ion o he p o ein ilm. I was obse ed in li e a u e ha ,
conside ing he same model luid as in he case o he p esen s udy, a me al head o med much
hicke p o ein ilm unde posi i e sliding, which can lead o a dec ease o ic ion be ween he
su aces [22].
Figu e 6. De elopmen o CoF as a unc ion o ime o me al-on-me al pai a highe mean speed
unde nega i e (a) and posi i e (b) sliding condi ions o a ious model luids.
I is appa en ha he MoM combina ion exhibi s an inc easing endency o ic ion, in gene al.
By con as , when he disc is o polye hylene, ic ion is dec easing o cons an , as is shown in Figu e
7. In ha case, he ic ion le el is associa ed wi h he kinema ic condi ions. When he ball o a es
as e han he disc, he lowes ic ion was exhibi ed by PBS, and he lub ican wi h he highe
con en o γ-globulin. The highes ic ion was obse ed o lub ican wi h lowe p o ein
concen a ion (10.5 mg/mL) and he dominan p esence o albumin. The endency was also qui e
uns able in ha case. Ne e heless, i has o be aken in o accoun ha he di e ence be ween
minimum and maximum ic ion is jus 0.05; he e o e, i migh be assumed ha he e ec o he
lub ican is negligible. When he disc was as e , he lowes ic ion was eached, once he lub ican
wi h highe p o ein con en (21 mg/mL) was employed. In addi ion, bo h he simple solu ion
exhibi ed ela i ely low ic ion o a ound 0.11. Wha is in co ela ion wi h p e ious indings is he
ic ion le el o saline solu ion. In a ecen s udy [23], a polye hylene disc conduc ed ecip oca ing
mo ion agains a me al pin (pu e posi i e sliding), while he ic ion was om 0.12 o 0.16, which
co esponds o he p esen esul s, see Figu e 7b.
Figu e 7. De elopmen o CoF as a unc ion o ime o me al-on-polye hylene pai a highe mean
speed unde nega i e (a) and posi i e (b) sliding condi ions o a ious model luids.
Figu e 6.
De elopmen o CoF as a unc ion o ime o me al-on-me al pai a highe mean speed
unde nega i e (a) and posi i e (b) sliding condi ions o a ious model luids.
I is appa en ha he MoM combina ion exhibi s an inc easing endency o ic ion, in gene al.
By con as , when he disc is o polye hylene, ic ion is dec easing o cons an , as is shown in Figu e 7.
In ha case, he ic ion le el is associa ed wi h he kinema ic condi ions. When he ball o a es
as e han he disc, he lowes ic ion was exhibi ed by PBS, and he lub ican wi h he highe
con en o
γ
-globulin. The highes ic ion was obse ed o lub ican wi h lowe p o ein concen a ion
(10.5 mg/mL) and he dominan p esence o albumin. The endency was also qui e uns able in
ha case. Ne e heless, i has o be aken in o accoun ha he di e ence be ween minimum and
maximum ic ion is jus 0.05; he e o e, i migh be assumed ha he e ec o he lub ican is negligible.
When he disc was as e , he lowes ic ion was eached, once he lub ican wi h highe p o ein
con en (21 mg/mL) was employed. In addi ion, bo h he simple solu ion exhibi ed ela i ely low
ic ion o a ound 0.11. Wha is in co ela ion wi h p e ious indings is he ic ion le el o saline
solu ion. In a ecen s udy [
23
], a polye hylene disc conduc ed ecip oca ing mo ion agains a me al
pin (pu e posi i e sliding), while he ic ion was om 0.12 o 0.16, which co esponds o he p esen
esul s, see Figu e 7b.
Ma e ials 2018, 11, x FOR PEER REVIEW 8 o 12
a he end o he es , see Figu e 6a. Conside ing he posi i e sliding condi ions, he CoF
de elopmen is sligh ly di e en . The highes ic ion o e he dominan pa o he expe imen was
exhibi ed by he solu ion wi h ela i ely high p o ein con en . Howe e , a e 75 s, he ic ion was
s abilized a abou 0.4 wi hou any u he ime-dependen change. The cou se o ic ion o saline
solu ion is linea ly inc easing ( he same beha iou as unde nega i e sliding), eaching 0.45 a he
end. Fo he o he p o ein solu ions, he beha iou is almos he same, wi h he excep ion o
lub ican con aining 70 mg/mL o albumin and 35 mg/mL o γ-globulin, which exhibi s he lowes
ic ion. This can be a ibu ed o he ac ion o he p o ein ilm. I was obse ed in li e a u e ha ,
conside ing he same model luid as in he case o he p esen s udy, a me al head o med much
hicke p o ein ilm unde posi i e sliding, which can lead o a dec ease o ic ion be ween he
su aces [22].
Figu e 6. De elopmen o CoF as a unc ion o ime o me al-on-me al pai a highe mean speed
unde nega i e (a) and posi i e (b) sliding condi ions o a ious model luids.
I is appa en ha he MoM combina ion exhibi s an inc easing endency o ic ion, in gene al.
By con as , when he disc is o polye hylene, ic ion is dec easing o cons an , as is shown in Figu e
7. In ha case, he ic ion le el is associa ed wi h he kinema ic condi ions. When he ball o a es
as e han he disc, he lowes ic ion was exhibi ed by PBS, and he lub ican wi h he highe
con en o γ-globulin. The highes ic ion was obse ed o lub ican wi h lowe p o ein
concen a ion (10.5 mg/mL) and he dominan p esence o albumin. The endency was also qui e
uns able in ha case. Ne e heless, i has o be aken in o accoun ha he di e ence be ween
minimum and maximum ic ion is jus 0.05; he e o e, i migh be assumed ha he e ec o he
lub ican is negligible. When he disc was as e , he lowes ic ion was eached, once he lub ican
wi h highe p o ein con en (21 mg/mL) was employed. In addi ion, bo h he simple solu ion
exhibi ed ela i ely low ic ion o a ound 0.11. Wha is in co ela ion wi h p e ious indings is he
ic ion le el o saline solu ion. In a ecen s udy [23], a polye hylene disc conduc ed ecip oca ing
mo ion agains a me al pin (pu e posi i e sliding), while he ic ion was om 0.12 o 0.16, which
co esponds o he p esen esul s, see Figu e 7b.
Figu e 7. De elopmen o CoF as a unc ion o ime o me al-on-polye hylene pai a highe mean
speed unde nega i e (a) and posi i e (b) sliding condi ions o a ious model luids.
Figu e 7.
De elopmen o CoF as a unc ion o ime o me al-on-polye hylene pai a highe mean
speed unde nega i e (a) and posi i e (b) sliding condi ions o a ious model luids.
Ma e ials 2018,11, 767 9 o 12
Conside ing he ce amic-ce amic con ac , he ic ion is inc easing unde nega i e sliding as in he
case o he me al-me al pai . Mo eo e , he e is a good co ela ion o he e ec o p o eins, while adding
he p o eins o he saline solu ion led o a dec ease o ic ion, especially du ing he i s pa o he es ,
see Figu e 8a. The same beha iou can be obse ed e en o posi i e sliding, while he e ec o he
lub ican is mo e subs an ial; anyway, he a iance in ic ion is s ill limi ed. In his pa icula case, he
ic ion is ela i ely s able o all he es luids, as is displayed in Figu e 8b. Simila ic ion wi h ilm
hickness de elopmen can be ound, as men ioned o he me al sliding pai . Using he luo escen
mic oscopy echnique, we e alua ed he cen al ilm hickness in ce amic-on-glass con ac , while i was
ound ha he lub ican laye o alumina ce amic unde posi i e sliding was much hicke compa ed
o nega i e sliding [24].
Ma e ials 2018, 11, x FOR PEER REVIEW 9 o 12
Conside ing he ce amic-ce amic con ac , he ic ion is inc easing unde nega i e sliding as in
he case o he me al-me al pai . Mo eo e , he e is a good co ela ion o he e ec o p o eins, while
adding he p o eins o he saline solu ion led o a dec ease o ic ion, especially du ing he i s pa
o he es , see Figu e 8a. The same beha iou can be obse ed e en o posi i e sliding, while he
e ec o he lub ican is mo e subs an ial; anyway, he a iance in ic ion is s ill limi ed. In his
pa icula case, he ic ion is ela i ely s able o all he es luids, as is displayed in Figu e 8b.
Simila ic ion wi h ilm hickness de elopmen can be ound, as men ioned o he me al sliding
pai . Using he luo escen mic oscopy echnique, we e alua ed he cen al ilm hickness in
ce amic-on-glass con ac , while i was ound ha he lub ican laye o alumina ce amic unde
posi i e sliding was much hicke compa ed o nega i e sliding [24].
Figu e 8. De elopmen o CoF as a unc ion o ime o ce amic-on-ce amic pai a highe mean
speed unde nega i e (a) and posi i e (b) sliding condi ions o a ious model luids.
Finally, he expe imen s we e ealized wi h a ce amic ball and polye hylene disc. The e ec o
he lub ican was again e y limi ed, as o he MoP pai . In pa icula unde posi i e sliding, he
ole o luid is unimpo an , since he di e ence be ween minimum and maximum ic ion is jus
abou 0.04, see Figu e 9b. The e o e, i is no sui able o iden i y which lub ican leads o he lowes
and he highes ic ion, espec i ely. The only no iceable inding is ha in he case o nega i e
sliding, sligh ly highe ic ion (a ound 0.12) was exhibi ed by simple γ-globulin solu ion and by he
solu ion wi h a highe con en o p o ein.
Figu e 9. De elopmen o CoF as a unc ion o ime o ce amic-on-polye hylene pai a highe mean
speed unde nega i e (a) and posi i e (b) sliding condi ions o a ious model luids.
As could be expec ed based on he p e ious indings, he p esen esul s clea ly p o e ha he
mos impo an ac o in luencing he ic ional beha iou o implan s is he ma e ial o he
componen s. Wha is qui e su p ising is he limi ed in luence o model luid composi ion, mainly in
he case o MoP and CoP pai s. Ne e heless, i should be aken in o accoun ha in ha d-on-so
pai s signi ican ly lowe con ac p essu e occu s; he e o e, his may be an explana ion o ela i ely
low sensi i i y o ic ion o es luid. Anyway, since he p e ious obse a ions ocusing on he
assessmen o ilm hickness in hip eplacemen s explo ed whe he he e ec o luid composi ion
Figu e 8.
De elopmen o CoF as a unc ion o ime o ce amic-on-ce amic pai a highe mean speed
unde nega i e (a) and posi i e (b) sliding condi ions o a ious model luids.
Finally, he expe imen s we e ealized wi h a ce amic ball and polye hylene disc. The e ec o
he lub ican was again e y limi ed, as o he MoP pai . In pa icula unde posi i e sliding, he ole
o luid is unimpo an , since he di e ence be ween minimum and maximum ic ion is jus abou
0.04, see Figu e 9b. The e o e, i is no sui able o iden i y which lub ican leads o he lowes and he
highes ic ion, espec i ely. The only no iceable inding is ha in he case o nega i e sliding, sligh ly
highe ic ion (a ound 0.12) was exhibi ed by simple
γ
-globulin solu ion and by he solu ion wi h a
highe con en o p o ein.
Ma e ials 2018, 11, x FOR PEER REVIEW 9 o 12
Conside ing he ce amic-ce amic con ac , he ic ion is inc easing unde nega i e sliding as in
he case o he me al-me al pai . Mo eo e , he e is a good co ela ion o he e ec o p o eins, while
adding he p o eins o he saline solu ion led o a dec ease o ic ion, especially du ing he i s pa
o he es , see Figu e 8a. The same beha iou can be obse ed e en o posi i e sliding, while he
e ec o he lub ican is mo e subs an ial; anyway, he a iance in ic ion is s ill limi ed. In his
pa icula case, he ic ion is ela i ely s able o all he es luids, as is displayed in Figu e 8b.
Simila ic ion wi h ilm hickness de elopmen can be ound, as men ioned o he me al sliding
pai . Using he luo escen mic oscopy echnique, we e alua ed he cen al ilm hickness in
ce amic-on-glass con ac , while i was ound ha he lub ican laye o alumina ce amic unde
posi i e sliding was much hicke compa ed o nega i e sliding [24].
Figu e 8. De elopmen o CoF as a unc ion o ime o ce amic-on-ce amic pai a highe mean
speed unde nega i e (a) and posi i e (b) sliding condi ions o a ious model luids.
Finally, he expe imen s we e ealized wi h a ce amic ball and polye hylene disc. The e ec o
he lub ican was again e y limi ed, as o he MoP pai . In pa icula unde posi i e sliding, he
ole o luid is unimpo an , since he di e ence be ween minimum and maximum ic ion is jus
abou 0.04, see Figu e 9b. The e o e, i is no sui able o iden i y which lub ican leads o he lowes
and he highes ic ion, espec i ely. The only no iceable inding is ha in he case o nega i e
sliding, sligh ly highe ic ion (a ound 0.12) was exhibi ed by simple γ-globulin solu ion and by he
solu ion wi h a highe con en o p o ein.
Figu e 9. De elopmen o CoF as a unc ion o ime o ce amic-on-polye hylene pai a highe mean
speed unde nega i e (a) and posi i e (b) sliding condi ions o a ious model luids.
As could be expec ed based on he p e ious indings, he p esen esul s clea ly p o e ha he
mos impo an ac o in luencing he ic ional beha iou o implan s is he ma e ial o he
componen s. Wha is qui e su p ising is he limi ed in luence o model luid composi ion, mainly in
he case o MoP and CoP pai s. Ne e heless, i should be aken in o accoun ha in ha d-on-so
pai s signi ican ly lowe con ac p essu e occu s; he e o e, his may be an explana ion o ela i ely
low sensi i i y o ic ion o es luid. Anyway, since he p e ious obse a ions ocusing on he
assessmen o ilm hickness in hip eplacemen s explo ed whe he he e ec o luid composi ion
Figu e 9.
De elopmen o CoF as a unc ion o ime o ce amic-on-polye hylene pai a highe mean
speed unde nega i e (a) and posi i e (b) sliding condi ions o a ious model luids.
As could be expec ed based on he p e ious indings, he p esen esul s clea ly p o e ha
he mos impo an ac o in luencing he ic ional beha iou o implan s is he ma e ial o he
componen s. Wha is qui e su p ising is he limi ed in luence o model luid composi ion, mainly in
he case o MoP and CoP pai s. Ne e heless, i should be aken in o accoun ha in ha d-on-so
pai s signi ican ly lowe con ac p essu e occu s; he e o e, his may be an explana ion o ela i ely
low sensi i i y o ic ion o es luid. Anyway, since he p e ious obse a ions ocusing on he
assessmen o ilm hickness in hip eplacemen s explo ed whe he he e ec o luid composi ion