Digital Theses Archive


Tesi etd-03172021-115629

Type of thesis
Innovative technologies for quantitative diagnosis in orthopaedics
Scientific disciplinary sector
Istituto di Biorobotica - BIOROBOTICS
relatore Prof. DARIO, PAOLO
  • bone fracture
  • capacitive-based device
  • diagnosis
  • external fixator
  • orthopaedics
  • osteoarthritis
  • quantitative ultrasound
  • standardization
Exam session start date
Bone fracture and osteoarthritis (OA) are among the most common orthopaedic diseases, which threats to people especially in old age. In both cases, a misdiagnosis or even a delayed diagnosis can lead to complications and prolonged times of healing, further increasing the costs related to the treatments. <br>The currently available methods of diagnosis are completely subjective and dependent on the clinician experience. In most of the cases, a clinical examination is performed, based on a visual evaluation, palpation of the joint and patient’s description of symptoms. X-rays are also widely used, due to the good availability and the relative associated low costs. However, they involve the exposure to ionizing radiation and hence are considered unsafe especially for repetitive tests. Other imaging techniques that allow a good resolution of the analysed tissues (such as the Magnetic Resonance Imaging) are occasionally used as expensive and time-consuming. Hence, a reliable, objective, low-cost and safe method for the healing assessment is essential for both the patient&#39;s well-being and to reduce the costs associated to prolonged treatments or re-interventions.<br>The work of this thesis was based on, and driven by, the above considerations, focusing on two major open problems in diagnostic orthopedics:<br><br>1. the lack of a non-invasive and objective method to monitor both bone stiffness and implant stabilization. <br>Although the attempts during the years, there is not a well-established and objective method to assess bone growth, also guaranteeing a control on the stabilization of the bone implant. <br><br>2. the lack of a non-invasive and objective method to assess structural and material properties of bone and cartilage tissues. <br>Quantitative Ultrasound (QUS) proved to be a reliable and completely safe technique to obtain quantitative information on the microstructure and properties of the investigated tissues. While interesting results based on QUS have been obtained for the diagnosis of osteoporosis and rheumatoid arthritis, many efforts have to be faced to extend such techniques for the assessment of bone healing and for the diagnosis of OA, paving the way for a future application in-vivo. Moreover, in this context, the development of tools aiming at reducing the dependence from the operator during the US acquisition is also of great interest. Indeed, such tool would enable the acquisition also for not skilled operators, speeding up the diagnosis procedure. <br><br>To face the mentioned open challenges, different approaches have been explored. To address the point 1, an external orthopaedic implant has been equipped with capacitive-based sensors, to monitor both implant stability and bone callus stiffness by measuring the displacements on the external pins. The experiments have been conducted in-vitro using a tibia fracture model stabilized with an external frame (i.e., Hoffmann external fixator) in a standard bi-lateral configuration used in case of tibia fracture. The measurement system proved to be easy to integrate on the external fixator pins and to discriminate all the possible movements of the pins thanks to a smart configuration of the single capacitive sensor unit.<br>To address point 2, QUS was exploited to investigate quantitative acoustic changes in case of bone fracture and OA. On this regard, in-vitro experiments have been conducted to monitor changes in bone mineral content during fracture healing process. The proposed metric was effective in identifying different hydroxyapatite (from 10 to 50% w/v) and calcium carbonate (from 2 to 6% w/v) concentrations in bone-mimicking phantoms. Furthermore, ex-vivo experiments have been performed to investigate healthy and enzymatically degraded bovine articular cartilage. Our preliminary results demonstrated the possibility to derive acoustic parameters able to discriminate healthy from degenerated cartilage, using a transmission frequency typically employed in the clinical practice (15 MHz). In this framework, the development of a wearable knee brace has been implemented to standardize the acquisition of US images for the diagnosis of OA. Indeed, the operator-dependency is currently the major weakness that limits the use of US in the clinical practice. Our first prototype demonstrated the possibility to standardize the US-images acquisition and make it achievable also from untrained subjects, representing a fundamental step toward the use of tele-ultrasonography for OA diagnosis.<br>The aim of this work is to propose a novel methodological approach of diagnosis that may overcome the limitations of the currently available methods and that can be introduced in the clinical routine without revolutionizing the current system. The proposed tools are meant to be used independently or even in combination with the common purpose to support the evaluation of the clinician along the whole healing time, providing quantitative metrics on which the final assessment can be based.<br>