B. POMPE et al.: THE USE OF AN INTRA-ORAL SCANNER FOR PATELLAR SURFACE ANALYSIS ...
39–43
THE USE OF AN INTRA-ORAL SCANNER FOR PATELLAR
SURFACE ANALYSIS IN TOTAL KNEE ARTHROPLASTY
UPORABA INTRAORALNEGA SKENERJA ZA ANALIZO POVR[IN
POGA^ICE PRI TOTALNI ARTROPLASTIKI KOLENA
Klemen Bo{njak
1,2*
, Bo{tjan Kocjan~i~
1,2
, Drago Dolinar
1,2
, Borut Pompe
1,2
1
University Medical Centre Ljubljana, Department of Orthopaedic Surgery, Zalo{ka cesta 9, 1000 Ljubljana, Slovenia
2
University of Ljubljana, Faculty of Medicine, Chair of Orthopaedics, Zalo{ka cesta 9, 1000 Ljubljana, Slovenia
Prejem rokopisa – received: 2020-06-09; sprejem za objavo – accepted for publication: 2020-07-27
doi:10.17222/mit.2020.115
Using an intra-oral scanner for surface and contact evaluation is a novelty in orthopaedics. We introduced this method to com-
pare the congruence between patellar and femoral component surfaces. The compared patellar surfaces were created either with
resurfacing, retention of an un-resurfaced patella or patelloplasty, a reshaping method where both facets are resected to match
the trochlear surface. In our prospective clinical study, two patients had their patellar surfaces scanned during knee
endoprosthesis (Genesis II, Smith & Nephew) implantation, using TRIOS® (3Shape) intraoral laser scanner. Each patient’s pa-
tella was scanned three times. First, the original joint surface was scanned after arthrotomy, then scanned again after reshaping
the patellar surface and finally scanned after resurfacing with the appropriate standard implant was performed. The acquired sur-
face data were evaluated using CloudCompare software. A mathematical algorithm was used to achieve the best proximity be-
tween these surfaces. Distances between the surfaces were measured throughout 0–120° of knee flexion. We defined the mea-
sure of proximity as "contact area magnitude". On average, the contact area magnitude was 2.91±0.82 mm using the
un-resurfacing method, 3.19±0.95 mm using the resurfaced method and 3.84±0.91 mm using patelloplasty. Leaving the patella
un-resurfaced resulted in an improved contact area magnitude. The proximity of the surfaces increased with knee flexion until
75°. With this study, the use of an intra-oral scanner for the surface analysis and intraoperative congruence evaluation was dem-
onstrated. This method could contribute to a better understanding of patellofemoral congruence during total knee arthroplasty.
Keywords: total knee arthroplasty, patellofemoral congruency, laser surface scanning
Uporaba intraoralnega skenerja za oceno povr{in in kontakta med njimi je novost v ortopediji. To metodo smo uvedli za
primerjavo kongruence med povr{ino poga~ice in stegneni~ne komponente. Povr{ine poga~ice, ki smo jih primerjali so bile
pridobljene z artroplasti~no preplastitvijo poga~ice, ohranitvijo poga~ice ali pateloplastiko, metodo preoblikovanja, pri katerem
obe ploskvi reseciramo tako, da se ujemata s povr{ino trohlee. V na{i prospektivni klini~ni {tudiji sta bila dva bolnika tekom
implantacije kolenske endoproteze (Genesis II, Smith in Nephew), skenirana z intraoralnim laserskim skenerjem TRIOS®
(3Shape). Vsako bolnikovo povr{ino poga~ice smo skenirali trikrat. Najprej smo skenirali prvotno povr{ino sklepa, nato
ponovno po preoblikovanju povr{ine s pateloplastiko in nazadnje {e po endoproteti~ni preplastitvi poga~ice. Pridobljeni podatki
so bili obdelani s programsko opremo CloudCompare. Za doseganje maksimalnega prileganja teh povr{in, smo uporabili
matemati~ni algoritem. Razdalje med prou~evanimi povr{inami so bile izmerjene skozi celoten obseg 0–120° fleksije kolena.
Ujemanje povr{in smo opredelili s pomo~jo razdalje med njimi, dobljeno mero kongruence pa opredelili kot "stopnjo
kontaktnega obmo~ja". V povpre~ju je bila stopnja kontaktnega obmo~ja 2,91±0,82 mm pri ohranjeni povr{ini poga~ice,
3,19±0,95 mm pri preplastitvi poga~ice in 3,84±0,91 mm pri pateloplastiki. Ohranitev povr{ine poga~ice, je izbolj{ala njeno
ujemanje s stegneni~no komponento. Ujemanje se je z upogibanjem kolena pove~alo do 75°. S to {tudijo smo prikazali
uporabnost intraoralnega skenerja za povr{insko analizo in intraoperativno oceno ujemanja povr{in. Prikazana metoda bi lahko
prispevala k bolj{emu razumevanju patelofemoralne kongruence pri totalni artroplastiki kolena.
Klju~ne besede: totalna artroplastika kolena, patelofemoralna kongruenca, skeniranje povr{in z laserjem
1 INTRODUCTION
The correct method of patellar surface management
during a total knee arthroplasty (TKA) is still unclear
and this topic is regarded as controversial. Patellofemoral
complications represent the most common cause leading
to a TKA revision surgery, as bearing surface forces and
contact patterns generated at the patellofemoral joint al-
ter after TKA compared to the normal knee.
1–3
To avoid
these complications and improve the outcome, reports
highlighting the importance of patellofemoral congruity
have emerged.
4–6
These authors put the emphasis on the
correct shaping of the patellar surface and the choice of
an adequately fitting femoral component design.
1,5
It has
been reported that sharper facet-angled patellae produce
larger postoperative patellar tilt angles, and lead to pro-
gressive patellar osteosclerosis, which is suggestive of
higher patellofemoral joint pressures, malalignment and
osteoarthritis progression.
4,6
However, the relationship
between patellofemoral joint congruence and the clinical
outcome after a TKA procedure is not well established in
the literature and clinical studies are needed to address
this issue.
7–9
As the shape of the chosen femoral implant
remains identical, emphasis has been given to the opti-
mal method of patellar management.
6,7
In this article we
will demonstrate the use of a new tool in the postopera-
tive patellar surface congruity evaluation of the two most
Materiali in tehnologije / Materials and technology 55 (2021) 1, 39–43 39
UDK 620.1:67.017:616 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 55(1)39(2021)
*Corresponding author's e-mail:
klemen.bosnjak@gmail.com (Klemen Bo{njak)

widespread methods, i.e., patellar resurfacing and un-re-
surfacing, together with the method of patelloplasty.
The established methods of patellar management are
presented in more detail. The most frequently performed
one is resurfacing, as many surgeons prefer to practice
this method routinely, with the purpose of lowering the
anterior knee pain.
3,10
Although revision rates with resur-
facing are low, the causes leading to them are severe:
patellar fracture, osteonecrosis, polyethylene wear, insta-
bility, aseptic loosening, dislocation, rupture of the
extensor mechanism
2,10
In contrast, some authors report
similar long-term results regarding patient satisfaction,
functional and knee pain outcomes in resurfacing and
un-resurfacing.
2,11
Therefore, to avoid severe complica-
tions, some prefer retaining the patella over resurfac-
ing.
2,11
The management with patelloplasty, proposed by
some surgeons, includes osteophyte removal and the re-
section of patellar facets with tangential cuts, trimming
and shaping the patella to match the trochlea of the fem-
oral component.
7,12
A. @upan et al.
12
found higher patient
satisfaction and lower knee pain outcomes with
patelloplasty, compared to un-resurfacing. Some sur-
geons, however, found no differences between patellar
resurfacing and patelloplasty in terms of patient satisfac-
tion and knee pain outcomes, but prefer patelloplasty to
preserve the bone stock.
7
We have chosen a new tool to determine which
method of patellar management during TKA results in
the best patellofemoral congruence. Our aim was to dem-
onstrate the use of an intraoral scanner for surface analy-
sis and congruence evaluation. As a measure of congru-
ence, the proximity between the surfaces was used. We
have defined this distance as the "contact area magni-
tude". The use of this scanner in orthopaedics has not yet
been presented in the literature. We hypothesized that
different congruence can be achieved with resurfacing,
un-resurfacing or patelloplasty.
2 MATERIALS AND METHODS
2.1 Study participants
We selected two patients with degenerative
osteoarthritis of the knee joint who underwent a TKA
(Genesis II, Smith & Nephew, Memphis Tennessee,
USA) in January 2016 at our institution. The following
exclusion criteria were applied: previous surgical proce-
dures on the knee joint involving the extensor mecha-
nism, rheumatoid diseases, osteoporosis, history of
patellar fracture or instability, non-degenerative related
preoperative surface pathologies of the knee joint and
valgus or varus deformity greater than 15°. Informed
consent was obtained from both participants.
2.2 Surgical procedure
The operations were performed by the same ortho-
paedic surgeon (B.P.), using the same method of patellar
management and implanting the same size of femoral
component. At the beginning of the procedure a tourni-
quet was applied and switched on for the entire duration.
Using the medial parapatellar approach, the patella was
everted and denervated. The surface of the un-resurfaced
patella was scanned using the TRIOS® intraoral laser
scanner (3Shape, Copenhagen, Denmark). Next, the sur-
face was removed with two tangential cuts, thus creating
two facets that intersected at an angle of approximately
130°. The surface managed with patelloplasty was then
scanned using the same intraoral laser. After that, the
managed patellar surface was cut off and a dome poly-
ethylene button was positioned medially, creating a re-
surfaced surface and the patellar surface was scanned
again.
2.3 Surface analysis
We used an intraoral scanner, which produces accu-
rate depictions of the scanned surface with an in-vivo
precision of 37.9–99.1 μm.
13
The scanner uses laser and
surface pattern video recognition technology to evaluate
different types of surfaces.
14,15
The scanned data were
then converted and imported into a computer program,
where it represented a precise three-dimensional recon-
struction of the surface.
13–15
The data of the femoral com-
ponent and the polyethylene button were provided by
Smith & Nephew. For the computer analysis, Cloud
Compare software version 2.6.2. (EDF, Paris, France)
was used. We compared congruence between the femoral
component surface and the patellar surface: un-resur-
faced, resurfaced and following patelloplasty. As a mea-
sure of congruence, the mean distance with standard de-
viation (SD) between the surfaces was used. Using
surface proximity as a measure of congruence has been
proposed by many authors.
16,17
In our study we have de-
fined this measure as "contact area magnitude". To
achieve better contact area magnitude, we minimized the
distances between the two surfaces using a mathematical
algorithm.
18
With reference to G.Windisch et al.,
16
we
disabled the intersections and overlapping of surfaces.
All the structures were assumed to be rigid with
frictionless contact between them. Using a computer
simulation, congruence was compared for each 15° of
knee flexion throughout the range of 0–120°. The kine-
matics of patellar movement was defined through a fem-
B. POMPE et al.: THE USE OF AN INTRA-ORAL SCANNER FOR PATELLAR SURFACE ANALYSIS ...
40 Materiali in tehnologije / Materials and technology 55 (2021) 1, 39–43
Figure 1: An example of distance distribution between the un-resur-
faced patellar and femoral surfaces at 60° of knee flexion. The distri-
bution is given as normal distribution. (Count) – quantity of distances,
(C2M signed distances) – length of distances given in millimetres

oral coordinate system, based on Grood and Suntay’s
definition.
19
The patellar starting position and kinematics
were supervised under the guidance of an orthopaedic
surgeon, as proposed in the literature.
20
The gathered
data were numerical and normally distributed (Figure 1).
For a visual evaluation the software was used to pro-
duce a colour-coded map superimposed on the patellar
surface. The distances were divided into 2-mm intervals,
each represented by different colour coding (Figure 2a
and 2b).
2.4 Statistical analysis
A statistical analysis was made using SPSS software
version 20.0 (SPSS Inc., Chicago, IL, USA). For the in-
tergroup comparison between the types of surfaces a
one-way analysis of variance (ANOVA) was used for
each dependent variable: congruence magnitude in
un-resurfaced, resurfaced and patelloplasty groups. Inter-
group comparisons were made in 15° intervals, through-
out the range of 0–120° of knee flexion. Results were
considered significant at p < 0,05.
2.5 Compliance with ethical standards
All procedures performed in the study involving hu-
man participants were in accordance with the 1964 Hel-
sinki declaration and its later amendments and were re-
viewed by National Medical Ethics Committee.
Informed consent was obtained from both participants
included in the study.
3 RESULTS
The lowest contact area magnitude and therefore the
highest congruence in intergroup comparison was
achieved with the method of un-resurfacing during
15–120° and with the method of resurfacing at 0°
(Table 1, Figure 3). The highest contact area magnitude
B. POMPE et al.: THE USE OF AN INTRA-ORAL SCANNER FOR PATELLAR SURFACE ANALYSIS ...
Materiali in tehnologije / Materials and technology 55 (2021) 1, 39–43 41
Figure 2: a) An example of graphical distance evaluation between the un-resurfaced patellar and femoral surfaces at 60° of knee flexion,
b) superposition of the un-resurfaced patella on femoral surfaces of the knee endoprothesis
Figure 3: Contact area magnitude between the patellar surface type
and the femoral component at different flexion angles. (mm) – numer-
ical data in millimetres, (°) – numerical data in angle degrees
Table 1: Mean contact area magnitude between the patellar surface
type and the femoral component at different flexion angles. The values
are given in millimetres as mean and standard deviation (#±SD)
Degree of
flexion
Type of patellar surface
Un-resurfaced Resurfaced Patelloplasty
0° 3.19±2.43
a
2.62±1.90
a
3.48±2.41
a
15° 2.74±1.94
a
3.05±2.47
a
4.20±2.32
a
30° 2.33±1.66
a
2.65±2.30
a
3.55±2.02
a
45° 2.32±1.29
a
2.36±2.09
a
3.17±1.79
a
60° 1.94±1.14
a
2.39±2.11
a
2.87±1.54
a
75° 2.09±1.45
a
2.35±2.31
a
2.94±1.89
a
90° 3.08±2.24
a
3.66±2.70
a
3.55±2.66
a
105° 4.15±2.55
a
4.77±3.43
a
5.27±3.28
a
120° 4.35±2.67
a
4.86±3.42
a
5.50±3.37
a
a
Values are statistically significant, with p < 0.001

and therefore the lowest congruence overall was
achieved with patelloplasty, except at 90°, where it was
achieved with resurfacing (Table 1, Figure 3).
4 DISCUSSION
Congruence between joint surfaces is important. In
biomechanical and cadaveric studies it strongly corre-
lated with knee joint force distribution and stress genera-
tion.
20–23
It is suggested that highly congruent surfaces of
the patella and femur contribute to lower wear and knee
pain.
4,5,20
However, there is no clear evidence that im-
proved patellofemoral congruence correlates with the re-
duction of knee pain after TKA.
7–9
The origin of knee
pain is considered to be multifactorial.
3,8,23
A.Takahashi
et al.
4
demonstrated that morphologically incongruent
patellae produce higher stress concentrations at the point
of femoral contact and cause significantly more degener-
ative changes in the underlying subchondral bone tissue.
A. Inoue et al.
6
additionally demonstrated the importance
of pre-operative patellar shape evaluation by reporting on
increased patellar tilting and poor alignment of surfaces
where the femoral component and patella were incongru-
ent. Surgical technique and prosthesis design are there-
fore considered the most important factors affecting the
extent of this problem.
4,5,8
The relatively novel method of patellar reshaping,
where the bone is cut tangentially to match the surface of
the femoral component, produced the least congruent
surfaces in our study. Steeper facets and an inclination to
tilting were observed on the new patelloplasty-formed
surfaces. In contrast, the un-resurfaced patella achieved
the highest congruence at every degree of flexion, except
0°. S. Matsuda et al.
21
reported that a patellar component
with steeper facets can seat correctly only over a small
portion of the trochlea. Furthermore, A. Inoue et al.
6
re-
ported poor patellofemoral alignment and in steeper
facet-angled patellae postoperatively. Our results can
therefore be supported by these reviews.
Only a few studies in the literature reported the use of
optic or laser technology to analyse the joint surface ge-
ometry.
5,16
In the study conducted by H. M. Ma et al.,
5
patellar and femoral component surfaces were scanned
using a topometric sensor and congruence was measured
on a 3-dimensional model with tangential line intersec-
tions.
5
De Santis et al.
23
reported on the use of a laser
scanner in conjunction with video texturing technology
and computer software simulation for a surface contact
comparison of the tibiofemoral area in a porcine model.
23
G. Windisch et al.
16
used a laser scanner to scan the
tibiotalar articular surfaces and computer software to
measure congruence with distance calculations similar to
the one presented in our study. No study to date has re-
ported the use of an intraoral scanner to analyse
patellofemoral surface congruence. Mostly, intraoral
scanners are used in dentistry as an alternative to conven-
tional physical impression taking in implant reconstruc-
tions.
24
In the literature the accuracy of intraoral scanners
is reported by comparing differences between a plaster
model and surfaces generated with an in vivo scan.
13,25
The accuracy for this scanner, ranging from 38 μm to 99
μm, has therefore been mostly validated for teeth.
13–15
Additional factors, such as the operator’s experience and
the environment are reported to affect accuracy.
24,25
P. Muller et al.
24
reported on the differences in accuracy
ranging from 8 μm to 35 μm between three separate
scanning techniques using the TRIOS intraoral scanner.
24
However, the viability and accuracy of scans made on
cartilaginous tissue have yet to be evaluated.
26
The present study has several limitations. As its re-
sults are based on representations from a mathematical
model, it is impossible to predict its value in an in-vivo
system. For our representative surfaces of the patellae,
the analysis was conducted with only two patients. Our
model represents ideal contact mechanics and our mea-
sure of congruence, the contact area magnitude, must be
considered as a measure achieved under these given cir-
cumstances. We did not consider the effect of muscle and
ligament-based forces during flexion and did not account
for compression or different elastic modules of the mate-
rials. The effects of rotational positioning of the femoral
component could not be simulated with our model. We
were also unable to account for changes of the biological
in-vivo stress adaptation, which remodels surfaces and
can improve the congruence.
2
5 CONCLUSION
With this study we have demonstrated the use of an
intraoral scanner in obtaining joint surface information.
Knowledge of intraoperative patellofemoral congruence
and contact areas can contribute to new decisions in sur-
gical planning regarding patellar management, and there-
fore, influence TKA success. Patellofemoral surface con-
gruence could have an effect on patellar alignment,
pressure distribution and osteoarthrosis progression, but
other factors such as correct implant positioning and sur-
gical technique, precise soft-tissue balance, choice of
femoral component design, grade of diseased cartilage
and patient weight and height are also associated with
it.
3–6
Therefore, further studies will be needed to evaluate
the value of our results.
Acknowledgements
We thank our colleagues Iztok Kri`nar, D.D.S.,
Minko Kri`nar, dental technologist and Ale{ Kri`nar,
dental technologist from Iztok Kri`nar dental practice
who provided the TRIOS® intra-oral laser scanner
(3Shape) and helped with the image acquisition process,
thus making this study possible. We are grateful to Bla`
Vidmar, geodetic engineer for assistance with the Cloud
Compare software computer analysis. We thank Luka
Botolin, product manager digiCEN from TECOS, Slo-
B. POMPE et al.: THE USE OF AN INTRA-ORAL SCANNER FOR PATELLAR SURFACE ANALYSIS ...
42 Materiali in tehnologije / Materials and technology 55 (2021) 1, 39–43

venian Tool and Die Development Center for consul-
tancy regarding three-dimensional surface analysis. We
also thank Ale{ Troha, D.M.D. who contributed the idea
of the study.
Conflicts of interest
Authors declare that they have no conflict of interest.
6 REFERENCES
1
C. Becher, T. J. Heyse, N. Kron, S. Ostermeier, C. Hurschler, M. D.
Schofer, S. Fuchs-Winkelmann, C.O. Tibesku, Posterior stabilized
TKA reduce patellofemoral contact pressure compared with cruciate
retaining TKA in vitro, Knee Surg Sports Traumatol Arthrosc., 17
(2009) 1159-65, doi:10.1007/s00167-009-0768-2
2
P. A. Keblish, A. K. Varma, A. S. Greenwald, Patellar resurfacing or
retention in total knee arthroplasty. A prospective study of patients
with bilateral replacements, J Bone Joint Surg Br., 76 (1994) 930-7
3
A. D. Boyd Jr, F. C. Ewald, W. H. Thomas, R. Poss, C. B. Sledge,
Long-term complications after total knee arthroplasty with or with-
out resurfacing of the patella, J Bone Joint Surg Am., 75 (1993)
674-81, doi:10.2106/00004623-199305000-00006
4
A. Takahashi, H. Sano, M. Ohnuma, M. Kashiwaba, D. Chiba, M.
Kamimura, T. Sugita, E. Itoi, Patellar morphology and femoral com-
ponent geometry influence patellofemoral contact stress in total knee
arthroplasty without patellar resurfacing, Knee Surg Sports
Traumatol Arthrosc., 20 (2012) 1787-95, doi:10.1007/s00167-
011-1768-6
5
H. M. Ma, Y. C. Lu, T. G. Kwok, F. Y. Ho, C. Y. Huang, C. H.
Huang, The effect of the design of the femoral component on the
conformity of the patellofemoral joint in total knee replacement, J
Bone Joint Surg Br., 89 (2007) 408-12, doi:10.1302/0301-620X.
89B3.18276
6
A. Inoue, Y. Arai, S. Nakagawa, H. Inoue, Y. Yoshihara, S. Yamazoe,
T. Kubo, Differences in patellofemoral alignment as a result of
patellar shape in cruciate-retaining total knee arthroplasty without
patellar resurfacing at a minimum three-year follow-up, Knee., 24
(2017) 1448-53, doi:10.1016/j.knee.2017.08.050
7
Z. T. Liu, P. L. Fu, H. S. Wu, Y. Zhu, Patellar reshaping versus resur-
facing in total knee arthroplasty – Results of a randomized prospec-
tive trial at a minimum of 7 years’ follow-up, Knee., 19 (2012)
198–202, doi:10.1016/j.knee.2011.03.004
8
D. Shervin, K. Pratt, T. Healey, S. Nguyen, W. M. Mihalko, M. M.
El-Othmani, K. J. Saleh, Anterior knee pain following primary total
knee arthroplasty, World J Orthop., 6 (2015) 795–803, doi:10.5312/
wjo.v6.i10.795
9
A. Senioris, M. Saffarini, S. Rahali, L. Malekpour, F. Dujardin, O.
Courage, Does patellofemoral congruence following total knee
arthroplasty correlate with pain or function? Intraoperative arthro-
scopic assessment of 30 cases, Ann Transl Med., 4 (2016) 279,
doi:10.21037/atm.2016.07.21
10
D. J. Wood, A. J. Smith, D. Collopy, B. White, B. Brankov, M. K.
Bulsara, Patellar resurfacing in total knee arthroplasty: a prospective,
randomized trial, J Bone Joint Surg Am., 84 (2002) 187–93,
doi:10.2106/00004623-200202000-00004
11
J. A. Feller, R. J. Bartlett, D. M. Lang, Patellar resurfacing versus re-
tention in total knee arthroplasty, J Bone Joint Surg Br., 78 (1996)
226–8
12
A. @upan, @. Snoj, V. Antoli~, B. Pompe, Better results with
patelloplasty compared to traditional total knee arthroplasty, Int
Orthop., 38 (2014) 1621–5, doi:10.1007/s00264-014-2366-2
13
S. B. Patzelt, A. Emmanouilidi, S. Stampf, J. R. Strub, W. Att, Accu-
racy of full-arch scans using intraoral scanners, Clin Oral Investig.,
18 (2014) 1687–94, doi:10.1007/s00784-013-1132-y
14
S. Akyalcin, B. E. Cozad, J. D. English, C. D. Colville, S. Laman,
Diagnostic accuracy of impression-free digital models, Am J Orthod
Dentofacial Orthop., 144 (2013) 916–22, doi:10.1016/j.ajodo.2013.
04.024
15
R. G. Nedelcu, A. S. Persson, Scanning accuracy and precision in 4
intraoral scanners: an in vitro comparison based on 3-dimensional
analysis, J Prosthet Dent., 112 (2014) 1461–71, doi:10.1016/
j.prosdent.2014.05.027
16
G. Windisch, B. Odehnal, R. Reimann, F. Anderhuber, H. Stachel,
Contact areas of the tibiotalar joint, J Orthop Res., 25 (2017) 1481–7,
doi:10.1002/jor.20429
17
H. C. Hsu, Z. P. Luo, J. A. Rand, K. N. An, Influence of lateral re-
lease on patellar tracking and patellofemoral contact characteristics
after total knee arthroplasty, J Arthroplasty., 12 (1997) 74–83,
doi:10.1016/s0883-5403(97)90051-6
18
C. R. Maurer, G. B. Aboutanos, B. M. Dawant, R. J. Maciunas, J. M.
Fitzpatrick, Registration of 3-D images using weighted geometrical
features, IEEE Trans Med Imaging., 15 (1996) 836–49, doi:10.1109/
42.544501
19
E. S. Grood, W. J. Suntay, A joint coordinate system for the clinical
description of three-dimensional motions: application to the knee, J
Biomech Eng., 105 (1982) 136–44, doi:10.1115/1.3138397
20
C. K. Fitzpatrick, P. J. Rullkoetter, Influence of patellofemoral artic-
ular geometry and material on mechanics of the unresurfaced patella,
J Biomech., 45 (2012) 1909–15, doi:10.1016/j.jbiomech.2012.05.028
21
S. Matsuda, T. Ishinishi, S. E. White, L.A. Whiteside, Patellofemoral
joint after total knee arthroplasty. Effect on contact area and contact
stress, J Arthroplasty., 12 (1997) 790–7, doi:10.1016/s0883-5403(97)
90010-3
22
B. Mav~i~, V. Antoli~, R. Brand, A. Igli~, V. Kralj-Igli~, D. R. Peder-
sen, Peak contact stress in human hip during gait, Pflugers Arch.,
440 (2000) R177–8, doi:10.1007/s004240000054
23
R. De Santis, A. Gloria, S. Viglione, S. Maietta, F. Nappi, L.
Ambrosio, D. Ronca, 3D laser scanning in conjunction with surface
texturing to evaluate shift and reduction of the tibiofemoral contact
area after meniscectomy, J Mech Behav Biomed Mater., 88 (2018)
41–7, doi:10.1016/j.jmbbm.2018.08.007
24
P. Müller, A. Ender, T. Joda, J. Katsoulis, Impact of digital intraoral
scan strategies on the impression accuracy using the TRIOS Pod
scanner, Quintessence Int., 47 (2016) 343–9, doi:10.3290/j.qi.a35524
25
R. Richert, A. Goujat, L. Venet, G. Viguie, S. Viennot, P. Robinson,
J. C. Farges, M. Fages, M. Ducret, Intraoral Scanner Technologies: A
Review to Make a Successful Impression, J Healthc Eng., 2017
(2017) 8427595, doi:10.1155/2017/8427595
26
B. Mav~i~, B. Babnik, A. Igli~, M. Kandu{er, T. Slivnik, V. Kralj-
Igli~, Shape transformation of giant phospholipid vesicles at high
concentrations of C12E8, Bioelectrochemistry., 63 (2004), 183–7,
doi:10.1016/j.bioelechem.2003.09.022
B. POMPE et al.: THE USE OF AN INTRA-ORAL SCANNER FOR PATELLAR SURFACE ANALYSIS ...
Materiali in tehnologije / Materials and technology 55 (2021) 1, 39–43 43