Because of my original background
(mechanical engineering) and my first position at the University of
Bologna (research assistant in Experimental Mechanics), during the
first year I focused on the methods for experimental stress
analysis (strain gauges, photoelasticity, fracture mechanics), and
on their application to biomechanics. From the beginning, I adopted
the methods of the design of the Experiment in my
research.
Currently my focus is on
orthopaedic biomechanics. I main expertise remains on experimental
methods: my focus is on in
vitro tests of biomaterials, implantable devices, bone tissues
and bony structures. This includes some activity towards the
development of new tools to assist the surgeon. A significant part
of my recent activity features a very intense synergy between
experimental investigations and numerical simulations. This
provides a validation to numerical methods and at the same time
enables complementing the in
vitro tests using numerical sensitivity analysis (also
featuring a statistical approach).
Methodological studies: development and optimization
of test procedures
In my entire
research career, I dedicated great effort to the development and
validation of my experimental methods. This part of scientific
research is often underestimated in our field. In all my research
projects a methodological investigation preceded the applicative
part. This is particularly critical for those applications where
the methods are not yet consolidated. Some
instances:
• Improvement
of the accuracy of strain measurement in bone
biomechanics;
• Assessment of
the accuracy of photoelastic coatings in bone
biomechanics;
• Validation of
synthetic bone models for in
vitro biomechanical testing;
• Improvement
of the performance of strain gauges on bone tissue and bone
models;
• Identification of the most relevant
loading configuration for the proximal femur;
• Methods to
assess primary stability of cementless hip
prostheses;
• Methods to
assess cement damage and long-term stability of cemented hip
prostheses;
• Adaptation of
the Design of the Experiment to in vitro biomechanical
investigations;
• Critical
review of existing standards;
• Consensus
development in collaboration with other research centers and
international organizations.
Development of instrumentation and sensors dedicated
to in vitro testing
In some cases,
state-of-the-art instrumentation is not adequate to address certain
clinical or biomechanical questions. In such cases IO developed
(with the collaboration of other colleagues and research groups)
new methods and tools:
• New methods
to accurately measure strain within acrylic surgical
cement;
• Development
of miniaturized piezoelectric sensors to measure interface stress
between implantable orthopaedic devices and the host bone or the
acrylic cement;
• Development
of a miniaturized 6-component load cell to measure the loads
transmitted across a device to fix sternotomy;
• A method to
test to failure bone segments while monitoring fracture initiation
and propagation;
• A transducer
to accurately measure the actual point of load application when
testing long bones.
Development and pre-clinical validation of
orthopaedic devices
In the past 15
years I collaborated both with surgeons and with manufacturing
companies, working on the development of materials and implantable
devices, and on their pre-clinical validation. In this process I
contributed to the assessment and optimization of some 20 devices
currently on the market. My main areas of expertise
include:
• Total hip
prostheses:
- Strength of
the prosthetic components;
- Functional
assessment: primary stability of cementless
components;
- Functional
assessment: long-term stability of cemented
components;
- Functional
assessment: load transfer and stress shielding of the femoral
component;
- Optimization
of the cement mantle for cemented components;
- Assessment of
the biomechanical effects of bone remodeling;
- Assessment of
the biomechanical effects of the formation of a fibrous tissue
layer.
• Resurfacing
hip prostheses:
- Primary
stability of the femoral component;
- Risk of
notching and neck fractures;
- Load transfer
and stress shielding of the femoral component;
- Combined
numerical-experimental investigation of the failure modes and
effects.
• Minimally
invasive hip prostheses (currently unpublished):
- Primary
stability of cementless components;
- Design
optimization of the femoral component.
• Total knee
prostheses:
- Wear
assessment of bi-compartmental total knee
prostheses;
- Long-term
stability and cement damage of the cemented component of total
knee replacement;
- Assessment of the load transfer of
the tibial component;
• Tumor prostheses:
- Load transfer and stress
shielding;
• Spinal devices:
- I collaborated to the validation of
a new test method for spinal devices (disk prostheses);
- A recently started project involves
the investigation of the biomechanics of healthy and diseased
vertebrae, and of the efficacy of augmentation methods.
• Surgical bone cements:
- Assessment of radiopacity of
different cement formulations;
- Static and dynamic properties of
classic and modified bone cements;
- Fatigue strength of modified bone
cements;
- Investigation
of the fracture surface of different bone
cements;
Surgical instrumentation and tools for assisted
surgery
The surgical
instrumentation plays a crucial role in the success of prosthetic
surgery. In the framework of my collaborations with the clinical
environment and with the manufacturing companies, I developed some
innovative solutions, some of which affected current
instrumentation and practice:
• Development
and validation of a device to measure the stability of a cementless
hip stem intraoperatively;
• Development
of a device to assess the stability of a cementless hip stem using
vibrations;
• Development
of a procedure to assess intra-operatively if the stem selected can
achieve a satisfactory degree of primary
stability;
• Identification of possible causes
of damage of the prosthetic component in modular hip stems, and
modification of clinical practice to reduce risk of
damage;
• I am
participating in a project where minimally invasive prostheses and
the surgical instrumentation are being revised and
optimized.
Biomechanical characterization of bone
structures
• Femur:
- Analytical
model for interpreting the strain distribution in the femoral
diaphysis;
- Stress
distribution in the proximal femoral metaphysis;
- In vitro replication of
traumatic and spontaneous fractures of the proximal
femur;
- Combined
numerical-experimental investigation: validation of Finite Element
models featuring inhomogeneous material
properties.
• Tibia and
fibula:
- Identification of repeatable
reference frames;
- Strain
distribution, anisotropy and viscoelasticity in the physiological
range;
- Validation of
Finite Element models of the human tibia to predict the stress
distribution.
• Bone
tissue:
- Measurement
of anisotropy of bone tissue in specimens obtained from the human
femur;
- I contributed
to studies on the interaction between microstructure and mechanical
properties of bone tissue.
• Bone
remodeling:
- I marginally
got involved in studies concerning bone remodeling and the
formation of fibrotic tissue: experimental measurements and Finite
Element models.
• Multi-scale
approach:
- A very
promising approach, that has received a great momentum in the
recent years, incorporates investigation of bone structures at
different dimensional scales. Inclusion of multi-scale information
in a single integrative model is one of the great challenges of the
Physiome project.
Other activities
I am
coordinating a project aimed at inspecting and recycling
orthopaedic devices (mainly osteosyntheses) in developing
countries. This project involves volunteers from Rizzoli, an
association of engineering students (Ingegneri Senza Frontiere) and
some non-profit organizations that operate in developing
countries.