The document discusses the design and development of customized ankle prostheses using 3D printing and modeling techniques. It summarizes the limitations of current ankle replacement implants and describes the development of a new design with anatomy-inspired geometry. Methods for imaging ankles with CT, MRI and other techniques are presented to create 3D models. Designs for the bone-implant interface are explored using trabecular metal and other materials meant to encourage bone ingrowth. Prototypes are manufactured using selective laser melting and tested for toxicity and osteogenesis with cell studies. The summaries provide an overview of the project to design and develop customized 3D printed ankle implants.

1. 19/07/2017
1
Design e stampa 3D di protesi
personalizzate per la cavigliapersonalizzate per la caviglia
Ing. Alberto LEARDINI e Ing. Paolo CARAVAGGI
Laboratorio Analisi del Movimento
Istituto Ortopedico Rizzoli
Total Ankle Replacement
Severe pain (*2M), end‐stage osteoarthritis with motion limitation (*50K)
Ankle Fusion Total Ankle Replacement (TAR)
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Both ankle fusion and current day TARs are inadequate in addressing the problem
* Numbers refer to USA market only, not worldwide

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Total Ankle ReplacementGeneration: Pioneers ‘70 Classics ‘80 Modern ‘90 Current 2000
Smith ICLH Newton TPR Mayo TNK Agility Bue‐Papp STAR ESKA AES Salto Alpha Hintegra Mobility Topez Eclipse SaltoTal Taric CCIevol
Cement fixation
Bone resection
Original CoR
changed
Osteolysis
Impingement
Loosening (90
Edge loading
Salvage/revision
Malleolar fracture
Polyethylene wear
and dislocation
Subsidence
Instability
Long pegs, cortical
window
Screw-based
fixation
Stress-shielding
Still Flat-Ti & Nat-
Ta?
Back to conforming
2-comp?!
Lateral access?!
Back to
constrained?!
Back to cement?!
Cumbersome
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Loosening (90-
95%)
Subsidence
Infection
Instability
Instability
Impingement
Infection
Vascularity
Bone removal
Syndesmosis fusion
Non- delay-union
Groove at articulat
Earlier
complications
Sizing
operative
technique!
Leardini et al. GIOT 2007; Giannini et al. Foot Ankle Surg 2000
Disegno anatomo-funzionale
Post Ant
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Plantarflexion DorsiflexionNeutral
Leardini Clin Biomech 2001; Med Bio Eng Comp 2001, 2002

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Disegno anatomo-funzionale
CaFi
ICMax Pl
TiCa
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Max Do
In 6 in‐vitro implantation (‘99–’02), and in about 1200 patients (Jul ‘03 – May ‘16)
Disegno funzionale
A1
A2
Tibia/Fibula Segment
A
B
F
CL CM
B1
B2
Lateral
Sphere
Medial
Sphere
Talus/Calcaneus Segment
Fixed
Sphere
CaFiL
TiCaL
C
CUSTOM IMPLANTS 6Parenti‐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

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Disegno funzionale
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Disegno anatomico
• A new TAR design with articulating surface geometry
representing a paradigm shift from the “Common knowledge”.
• Main features:
2. Lateral apex
1. Truncated non‐symmetric cone
Claims, close to normal:
• Joint Kinematics
• Load Transfer
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3. Saddle shaped
• Loading of ligaments
• Behavior under functional
and extreme loads
Expected benefits:
• Reduced wear
• Reduced rates of failure

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Disegno anatomico
Image‐ and experimental‐ based study of the morphology of the articular surfaces,
in natural and prosthetic ankle joint
CT Imaging
3D G t i l
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Segmentation &
3D Renderings
3D Geometrical
Analysis Design & Manufacturing
of Artificial Surfaces
Testing: 3D Kinematics and Kinetics Analyses
CAOS & EFAS Best Paper Awards!, June 2016ankles (vitro/vivo)
Progettazione personalizzata
Imaging
Biomech. MODELS:
anatomical
Bones
Li t D
D
E
S
I
D
E
S…modelling
Motion analysis
funct/anat
functional
Ligaments
Kinematics
D
E
S
I
G
N
G
N
d
i
m
e
s
n
Surgical/clinical
options:
• position
• shoulder/gutter
• fixation elements
• material
I
G
N
f
i
n
a
l
both ankles?!
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e
d
• cement / coating
• transverse plane
• chamfers
• insert
• cutting blocks?
both ankles?!
Liverani et al. Materials and Design 2016

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Scansioni ed immagini
 Best selection, including possible combinations, among imaging devices at IOR:
CT based tech:
‐ Standard CT (no soft tissue)‐ Standard CT (no soft tissue)
‐ Dual‐Energy CT (enhancement of soft tissues)
‐ ConeBeam CT (new technology, 3D and soft tissue, … loading!)
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MRI based tech:
‐ 1.5 T MRI
‐ 3.0 T MRI
Scansioni ed immagini
to create reference markers well detectable in CT & MRI via material combination
rigidly fixed on relevant anatomical structures via plaster
HARD MARKER
with centered cavity…. ….Filled with a
CRYSTAL JELLY BALL…. ….and hermetically closed
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to avoid possible drying.

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Scansioni ed immagini
Regular CT Tissue 1Regular CT Tissue 1
MRI 3T T2 FSMRI 1.5T cartilage new CBCT
Dual Energy CT Basal 1Dual Energy CT Basal 1
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Modellazione e registrazione
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Disegno e progettazione
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Disegno e progettazione
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Interfaccia impianto-osso
Polyethylene
component
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titolo
Topography
Bone‐implant 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)
‐ surface roughness (10‐50 micron)
‐ micron‐scale and nano‐scale (1 – 100nm)
Surface treatments
‐ sand‐blasting
‐ plasma sprying
‐ electropolishing
Chemistry & biocompatibility
‐ biotolerant (distance osteogenesis)
‐ bioinert (contact osteogenesis)
‐ bioreactive (stimulating bone ingrowth)
CUSTOM IMPLANTS 18Osseointegration
“A direct structural and functional connection between ordered, living
bone and the surface of a load‐carrying implant.”
Branemark (1985)
Stress‐shielding

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Interfaccia impianto-osso
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Metallo-trabecolare - Zimmer
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‘Trabecular bone model’
microCT – femoral bone
Acknowledgement : Laboratorio di Tecnologia Medica (IOR)
Top vieww
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Side view
Density = 17%
Trabecular thickness = 150um
Trabecular Separation = 670um

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Modelli interfaccia impianto-osso
ew
Acknowledgement: CIRI‐MAM (UniBO)
Top vieiew
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Side v
SPHERICAL
NEW geometries – density‐matched
ROUND DIAGONAL
Existing geometry ‐ Control
Dal .STL al modello CrCo
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Selective Laser Melting

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Test tossicità e osteogenesi
T0: 24 h T2: 2 weeks
und Acknolwedgement: laboratorio BITTA (IOR)roudiagonalecular
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trabespherical
top sidetop
Indagine SEM: campione
“round”
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Indagine SEM: campione “round” +
cellule
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Indagine SEM: campione “trabecolare”
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Indagine SEM: campione
“trabecolare” + cellule
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Prototipo di interfaccia
impianto-osso: protesi di caviglia
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Selective Laser Melting (CIRI‐MAM, UniBO)

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Sviluppi futuri …
Specialised Research /
Design Centre #iSpecialised Research /
Design Centre #1
Trad. Fabrication #N
Cloud
Services
Specialised Research /
Design Centre #N
Trad. Fabrication #1
Trad. Fabrication #j
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3DP Fabrication!
g
Grazie per l’attenzione
Ing. Alberto Leardini [leardini@ior.it]
Ing. Claudio Belvedere [claudio.belvedere@ior.it]
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Ing. Paolo Caravaggi [paolo.caravaggi@ior.it]
Laboratorio Analisi del Movimento, Istituto Ortopedico Rizzoli