Abstract
Deep heating procedures are helpful in treating joint contractures that frequently occur with fractures and joint diseases involving surgical implants and artificial joint prostheses. This study uses a one-dimensional composite medium model consisting of parallel slabs as a simplified approach to shed light on the influences of implants during ultrasound diathermy. Analytical solutions for the one-dimensional transient heat generation and conduction problem were derived using the orthogonal expansion technique and a Green’s function approach. The analytical solutions provided deep insight into the temperature profile by therapeutic ultrasound heating in the composite system. The effects of the implant material type, tissue thickness, and ultrasound operation frequency on temperature distribution were studied for clinical application. In addition, sensitivity analyses were carried out to investigate the influences of material properties on the temperature distribution during ultrasound diathermy. Based on the derived analytical solutions, the numerical simulations indicate that materials with high density, high specific heat, and low thermal conductivity may be optimal implant materials. Among available implant materials, a tantalum implant, which can achieve a lower temperature rise within the tissue (hydrogel) and bone layers during ultrasound diathermy, is a better choice thanks to its thermodynamics.
Highlights
Surgical implants and artificial joint prostheses are commonly used in the treatment of fractures and joint diseases
To investigate the influences of thetissue-implant-bone implant on the temperature field in the tissues during ultrasound thermal therapy, the complex system was simplified as a composite ultrasound thermal therapy, the complex tissue-implant-bone system was simplified as a composite system consisting of three parallel slabs
A tissue-implant-bone specimen was modeled as a composite system with three
Summary
Surgical implants and artificial joint prostheses are commonly used in the treatment of fractures and joint diseases. Patients receiving such therapies frequently develop joint contractures. Ultrasound diathermy has become an alternative for deep heating. Ultrasound produces heat through molecular vibrations at high frequency, which conduct or propagate energy throughout a medium. Such energy transmission in ultrasound treatments is minimally hindered by adipose tissue and has many benefits [3,4]. Therapeutic ultrasound can be utilized as either a superficial or a deep heating modality depending on its operation frequency and power. 3 MHz ultrasound is often adopted in superficial heating within 3 cm while 1 MHz ultrasound can be used to heat tissues at depths of 3–5 cm and is considered a deep heating agent [4]
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