6° Presentazione del workshop finale del progetto Custom Implants Custom-Endoprotesi Le superfici articolari affette da gravi degenerazioni sono sostituite da endoprotesi artificiali. L’attuale limitatissimo numero di taglie disponibili ingenera importanti problemi tra la protesi e l’osso ospitante, che porta spesso al fallimento della sostituzione. Con i nuovi strumenti a disposizione (immagini biomedicali, software di ricostruzione, modelli biomeccanici, ecc.) e la recente tecnologia di stampa-3D si sono progettate nuove protesi articolari personalizzate per la caviglia. Principali settori indirizzati: Farmaceutico, biomedico, chimico, biologico, ingegneria tissutale, clinico Sito web del progetto: www.custom-implants.it

1. Progettazione, validazione e stampa 3D in leghe
metalliche di endoprotesi per piccole articolazioni
Laboratorio Analisi del Movimento
Istituto Ortopedico Rizzoli

2. CUSTOM IMPLANTS 2
Total Ankle Replacement (TAR)
Severe pain (*2M), end-stage osteoarthritis with motion limitation (*50K)
Ankle Fusion
(Arthrodesis)
Total Ankle Replacement
(TAR)
Ankle fusion and current TARs are inadequate to solve the problem
* Numbers refer to USA market only

3. CUSTOM IMPLANTS 3
Cement fixation
Bone resection
Original CoR changed
Osteolysis
Impingement
Loosening (90-95%)
Subsidence
Infection
Instability
Edge loading
Salvage/revision
Malleolar fracture
Polyethylene wear and
dislocation
Subsidence
Instability
Impingement
Infection
Vascularity
Bone removal
Syndesmosis fusion
Non- delay-union
Groove at articulation
Long pegs, cortical window
Screw-based fixation
Stress-shielding
Flat-Ti & Nat-Ta
Earlier complications
Sizing
Back to conforming 2-comp..
Lateral access
Back to constrained..
Back to cement..
Cumbersome operative
technique..
Leardini et al. GIOT 2007; Giannini et al. Foot Ankle Surg 2000
Pioneers ‘70 Classics ‘80 Modern ‘90 Current 2000
Total Ankle Replacement (TAR)

4. CUSTOM IMPLANTS 4
TAR: the articular surfaces
Polyethylene
Metal
components

5. CUSTOM IMPLANTS 5
Design of TAR components from a novel experimental investigation of the
morphology of the ankle articular surfaces
Imaging
Segmentation &
3D Rendering
3D Geometrical
Analysis Design & Manufacturing
of Artificial Surfaces
Testing: 3D kinematic and kinetic analysis
CAOS & EFAS Best Paper Awards (2016)ankles (vitro/vivo)
TAR design: anatomical approach

6. CUSTOM IMPLANTS 6
F
C L CM
B1
B2
A1
A2
Lateral
Sphere
Medial
Sphere
Tibia/Fibula Segment
Talus/Calcaneus Segment
Fixed
Sphere
CaFiL
TiCaL
C
Parenti-Castelli, Leardini et al., Med Bio Eng Comp 2007; J Biomech 2009
 Two ligament fibres
 Three rigid contacts:
A. 2 sph-pla at Ti-Ta, 1 sph-pla at Ta-Fi
B. 3 sph-sph
 3D mathematical description of passive kinematics
TAR design: functional approach

7. CUSTOM IMPLANTS 7
TAR design: functional approach

8. CUSTOM IMPLANTS 86 in-vitro implantation (‘99–’02), and about 1200 patients (Jul ‘03 – May ‘16)
TAR design: anatomical-functional
approach

9. CUSTOM IMPLANTS 9
Custom design
Imaging
Biomech. MODELS:
anatomical
Motion analysis
funct/anat
functional
Bones
Ligaments
Kinematics
D
E
S
I
G
N
D
E
S
I
G
N
d
i
m
e
n
s
i
o
n
Surgical/clinical
options:
• position
• shoulder/gutter
• fixation elements
• material
• cement / coating
• transverse plane
• chamfers
• insert
• cutting blocks?
D
E
S
I
G
N
f
i
n
a
l
…modelling
both ankles?!
Liverani et al. Materials and Design 2016

10. CUSTOM IMPLANTS 10
Imaging
 Selection of best imaging technique:
 CT based imaging:
- Standard CT (no soft tissue)
- Dual-Energy CT (enhancement of soft tissues)
- ConeBeam CT (3D and soft tissue, real joint loading)
 MRI based imaging:
- 1.5 T MRI
- 3.0 T MRI

11. CUSTOM IMPLANTS 11
Design of reference markers detectable by CT & MRI rigidly fixed on relevant
anatomical structures via plaster
HARD MARKER
with centered cavity filled with a
CRYSTAL JELLY BALL hermetically closed
to prevent from drying out
Imaging

12. CUSTOM IMPLANTS 12
MRI 3T T2 FS
CBCT
Imaging
Regular CT Tissue 1
Standard CT
Dual Energy CT Basal 1
Dual Energy CT

13. CUSTOM IMPLANTS 13
3D modelling and registration

14. CUSTOM IMPLANTS 14
SURFACE-TO-SURFACE ANALYSIS
Bone-cartilage registration via best fitting method
CBCT+3T
Standard
CT+1.5T
Standard CT+3T CBCT+1.5T
ConeBeam CT + 3T MRI
• LESS OVERLAPPING
• GREATER HOMOGENEITY
tibiatalus
3D modelling and registration

15. CUSTOM IMPLANTS 15
DIFFERENCES IN ANATOMICAL
PARAMETERS
BETWEEN IMAGING TECHNIQUES
3D modelling and registration
Siegler S et al, Clin Biomech, 29(1):1-6, 2014.
Talus MED D(mm) LAT D(mm) ANT D(mm) ANT CENTR D(mm) CENTR D(mm)
POST CENTR D
(mm)
POST
D(mm)
CT STANDARD 39.5 33.8 85.3 70.7 59.4 76.2 85.2(-)
CBCT 40.0 36.1 62.0 121.7 86.3 75.9 50.1(-)
DUAL ENERGY CT 42.5 36.9 45.3 92.1 62.3 74.2 80.8 (-)
CT STANDARD +COR 1.5T 45.5 36.0 146.8 76.6 91.9 60.3 68.8(-)
CT STANDARD +SAG 1.5T 41.3 35.1 87.0 95.9 120.5 69.7 114.6 (-)
CT STANDARD + CUBE 3T 39.2 31.9 128.0 106.2 91.2 83.7 63.9
DUAL ENERGY CT +COR 1.5T 48.5 39.1 68.2 75.2 94.9 67.3 64.9
DUAL ENERGY CT +SAG 1.5T 51.5 41.3 77.4 95.8 127.0 65.5 51.6(-)
DUAL ENERGY CT + CUBE 3T 41.3 35.6 106.2 103.9 102.4 70.3 48.7
CBCT+COR 1.5T 57.9 41.6 89.4 81.6 90.8 99.0 61.9
CBCT+SAG 1.5T 53.6 45.0 136.0 95.0 139.4 73.6 (-) 39.1 (-)
CBCT + CUBE 3T 48.7 39.3 118.9 100.5 99.7 85.9 86.8

16. CUSTOM IMPLANTS 16
TAR design: virtual planning

17. CUSTOM IMPLANTS 17
TAR design: virtual planning

18. CUSTOM IMPLANTS 18
BOX (size M) Custom-sized
BOX components
+ 10%
SCALING of TAR components
TAR design: virtual planning

19. CUSTOM IMPLANTS 19
TAR: implant-bone interface
Polyethylene
Metal

20. CUSTOM IMPLANTS 20Osseointegration
Chemistry & biocompatibility
Implant-bone interface material
Core material
- metals (e.g. CoCr, Ti alloys, Mg alloys)
- ceramics (Zr and Al based)
- metals (CoCr, Ti alloy, Tantalum)
- Calcium-phosphate based
(biomimetic coating, e.g. hydroxyapatite)
- biotolerant (distance osteogenesis)
- bioinert (contact osteogenesis)
- bioreactive (stimulating bone ingrowth)
“A direct structural and functional connection between ordered, living
bone and the surface of a load-carrying implant.”
Branemark (1985)
Stress-shielding
Topography
- surface roughness (10-50 micron)
- micron-scale and nano-scale (1 – 100nm)
Surface treatments
- sand-blasting
- plasma sprying
- electropolishing

21. CUSTOM IMPLANTS 21
Novel implant-bone interface

22. CUSTOM IMPLANTS 22
Trabecular bone model
microCT – femoral bone
TopviewSideview
Density = 17%
Trabecular thickness = 150um
Trabecular Separation = 670um
Acknowledgement : Laboratorio di Tecnologia Medica (IOR)

23. CUSTOM IMPLANTS 23
Regular unit cells
CIRCULAR
CROSSING-ROD
Acknowledgement: CIRI-MAM (UniBO)

24. CUSTOM IMPLANTS 24
Regular unit cells porous scaffoldsTopviewSideview
SPHERICAL
Density-matched regular geometries
CIRCULAR CROSSING-ROD
Implant-to-bone control interface

25. CUSTOM IMPLANTS 25
From STL to CrCo samples
Selective Laser Melting (CIRI-MAM, UniBO)
9 x 9mm CoCr samples

26. CUSTOM IMPLANTS 26
Mechanical characterization
(ISO 13314, ASTM E9-09)

27. CUSTOM IMPLANTS 27
Geometrical validation
Circular lattice
hole diameter
Crossing-rod
strut dimension
Mean (SD) [µm] 761 ± 26 225 ± 27
STL nominal [µm] 800 200
Error [%] - 4.9 % + 12.7 %
Optical microscope

28. CUSTOM IMPLANTS 28
SEM: round samples
Geometrical validation
Acknowledgement: Università Politecnica delle Marche

29. CUSTOM IMPLANTS 29
SEM: trabecular samples
Geometrical validation

30. CUSTOM IMPLANTS 30
T0: 24 h T2: 2 weeks
Biocompatibilitycircularcrossing-rodtrabecularcontrol
top sidetop
Acknolwedgement: laboratorio BITTA (IOR)

31. CUSTOM IMPLANTS 31
Biocompatibility

32. CUSTOM IMPLANTS 32
SEM: round samples + cells
Biocompatibility

33. CUSTOM IMPLANTS 33
SEM: trabecular samples + cells
Biocompatibility

34. CUSTOM IMPLANTS 34
Final remarks
• Manufacturing: CoCr 3D porous structures are feasible via SLM
• Mechanical properties: similar to those of human bone 
(stress-shielding reduction)
• Biocompatibility: osteoblast-like cells proliferation and viability
is good on all geometries
• Results need to be confirmed in-vivo

35. CUSTOM IMPLANTS 35
Prototype of custom ankle prosthesis
via selective laser melting
(CIRI-MAM, UniBO)

36. CUSTOM IMPLANTS 36
Grazie per l’attenzione
Ing. Alberto Leardini [leardini@ior.it]
Ing. Claudio Belvedere [claudio.belvedere@ior.it]
Ing. Paolo Caravaggi [paolo.caravaggi@ior.it]
Laboratorio Analisi del Movimento, Istituto Ortopedico Rizzoli