Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Biomedical Engineering | en_US |
| dc.contributor.advisor | Zheng, Yongping (BME) | en_US |
| dc.creator | Palanisamy, Poornima | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/13954 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Accelerating hip fracture healing with low-intensity pulsed ultrasound | en_US |
| dcterms.abstract | Hip bone fracture rehabilitation is one of the most painful burdens for the elderly people globally. It is estimated that the incidence of hip fractures will be found increasing in Hong Kong, China and other regions due to the increase of elderly people. The major reasons for fractures include trauma, osteoporosis and certain metabolic conditions. However, most of the fractures heal by themselves, certain fractures results in non-unions or delayed union even after surgical interventions. There are many interventions available, such as electrical, electromagnetic and capacitive coupling stimulation, for the treatment of bone fractures. Low-intensity pulsed ultrasound stimulation (LIPUS), being a non-invasive treatment has been used for the past three decades for many different applications. Among that, LIPUS has been primarily used for healing of nonunion fractures but not for fresh fractures. Although, LIPUS has shown promising results on certain fracture cases, its application on clinical practice on fresh fractures is limited due to no strong clinical evidence. Many researchers conducted human and animal studies to investigate the effectiveness of LIPUS in bone fracture healing. It was found that the mechanical stimulation of ultrasound using LIPUS can induce biomechanical, biochemical, bioelectrical, and biological responses in bone cells to enhance fracture repair. The majority of the LIPUS studies have applied the same stimulating strategy, which delivered a spatial average temporal average (ISATA) intensity of 30 mW/cm² with an ultrasound frequency of 1.5 MHz pulsed at 1 kHz. Up to now, the regular stimulating strategy was mainly used on superficial bones by utilizing an FDA-approved commercially available LIPUS device, and relatively low effectiveness was found on deeper fracture sites. | en_US |
| dcterms.abstract | In the present study, we hypothesized that the effectiveness of LIPUS on deeper fracture sites was affected by the thickness of the soft tissue and the effective intensity of LIPUS reaching the fracture site, as the absorption coefficients of the soft tissue are proportional to the depth and frequency. We have developed a parameter adjustable LIPUS stimulator to deliver the effective intensity of 30 mW/cm² on the surface of bone at the fracture site carried by using different ultrasound frequencies (0.5 MHz and 1.5 MHz) and adjusting the transmission power for compensating the attenuations caused by the actual tissue thicknesses. To compare our customized device with the commercial device, we conducted both in vitro and in vivo experiments. In the in vitro study, different thicknesses of human cadaver and porcine tissues were tested to find the change of attenuation and the actual acoustic intensity after propagating through the tissue layer. In the in vivo study, a novel hip fracture model was established using adult New Zealand white rabbits, and then different LIPUS treatment strategies were used in four animal groups, including control, positive control (PC, using commercial 1.5 MHz device), 0.5 MHz, and 1.5 MHz. A compensation method was used in 0.5 MHz and 1.5 MHz groups to adjust the intensity based on the thickness of the soft tissue in order to deliver a constant intensity (ISATA=30 mW/cm²) at the fracture site. It was noticed that understanding the soft tissue thickness range plays an important role in effectively delivering the ultrasound energy at the fracture site consistently. Therefore, we also conducted a study to measure the trochanteric soft tissue thickness of elderly people in Hong Kong using portable ultrasonography device followed by osteoporosis assessment to understand their bone health status using a quantitative ultrasound device. | en_US |
| dcterms.abstract | The results of our in vitro studies showed that, for the ultrasound frequency of 1.5 MHz, the attenuation was 6.0 dB (acoustic intensity decreased by 75%) after propagating the tissue with a thickness of 5.0 cm in both the cadaver and porcine tissues. In contrast, attenuation of around 2.0 dB was detected under 0.5 MHz after passing the same tissue layer. In the in vivo study using a newly established hip fracture rabbit model, the best results in bone histomorphometry, mechanical properties, and histological evaluation were consistently found in the 0.5 MHz group; and the 1.5 MHz group showed relatively better bone healing than the positive control group. Our in vivo animal study results suggested an ultrasound frequency of 0.5 MHz and a consistent intensity of 30 mW/cm² at the fracture region for healing of deep bone fractures. The results of human study revealed that the average trochanteric soft tissue thickness was 3.0±0.7 cm in male and 3.8±0.9 cm in female and the thickness at major fracture sites such as trochanter, femoral head and femoral neck regions showed the female participants have thicker soft tissue layers than male participants. Also, the prevalence of osteoporosis was 18.4 % in males and 61.5 % in females, according to our results. This thesis offers a direct reference for future investigation of LIPUS for deep bone fracture healing in both research and clinical translations. | en_US |
| dcterms.extent | xx, 134 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2025 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.accessRights | open access | en_US |
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