Biomedical Engineering: Applications, Basis and Communications

In this paper we demonstrate a new method to quantify direction and magnitude of sway in response to periodic inputs. The postural sway response was modeled as an ellipse, allowing the determination of angle of heading as well as the resultant magnitude. To demonstrate this methodology, center of pressure data obtained from a subject receiving sinusoidal (0.25 Hz, 1.2 mA peak-to-peak) galvanic vestibular stimulation in both the binaural-bipolar and binaural-monopolar configurations were analyzed. The binaural-bipolar and binaural-monopolar stimuli elicited sway patterns that were oriented at 4° and 97° to the medial-lateral axis, respectively. In addition, the binaural-monopolar stimulus generated twice as much sway as the binaural-bipolar stimulus. We propose that this method can be applied to sway obtained from sinusoidal inputs to the sensory systems controlling balance. Estimation of the direction and magnitude of postural sway will become an important tool for understanding postural control mechanisms for disturbances to balance that do not occur in a cardinal direction.

Microsurgical vascularized bone graft has been successfully used to treat large tibial defects. The shape, size and length of the fibula make it a popular donor site for most tibia defects. The goat of this study is to numerically analyze the stress distribution in the transferred fibula and to evaluate the nature of the placement of the fibular graft and its relations to failure. A finite element analysis was conducted to investigate the stress distribution and to predict the stress fracture positions in transferred bones. The calculated results matched well with clinical observations. The simulation suggests that those grafts having a lower site transfer exhibit a higher level of stress distribution. The finite element model also suggests that the stress level of an obliquely placed graft is higher than that of a vertically placed graft, especially at the distal tibia-fibula junction. A longer period of protection is therefore recommended for the treatment of a lower site transfer or an obliquely placed grafted bone to avoid bone stress fracture.

An Electrogastrography (EGG) recorder is proposed in this paper. This recorder consists of a microcontroller, an interfacing circuit for the RS-232, amplifiers and filters for signal conditioning, and a control program for EGG acquisition. An EGG signal, filtered between 0.015 and 0.5 Hz, was used to evaluate the performance of this system. The results suggest that this system is useful both in the hardware circuits and in the analyzing software. The complete system is versatile and cheap. Thus, it will be helpful for other laboratories with limited financial budget. Furthermore, circuits are described in detail for this purpose.

Tendons are frequently injured by direct trauma. Tendon adhesions were a common sequel of tendon repair and are one of the most challenging problems in hand surgery.

The concept of “controlled motion” gradually replaced “total immobilization” in the treatment of flexor tendon injuries and today represents a standard of care for all primary repaired flexor tendon injury. Use of controlled motion splints during the early stages of stages of tendon recovery in crease tendon gliding. However, how best to achieve passive motion and the effect of passive motion on tendon gliding have remained controversial subjects. Based on a series of recent experiments, the concept of “dynamic synergistic wrist motion splint” was established and evaluated. It was found that this synergistic wrist motion increases the tendon excursion due to eliminating the laxity and buckling of tendon in the regions between pulleys without introduce excessive amount of tension.

The purpose of this study is to design and fabricate a dynamic splint based on this concept and define the nature coordinated motion between the wrist and finger joints due to the passive tension of the muscles in vivo.

Parametric analysis will be conducted to achieve an optimum design with the consideration of anatomic constraints. Clinical trial of using such dynamic splint will be evaluated in the future.

Angiotensin II and its antagonists were used as permeant probes to investigate the mechanism of transdermal iontophoretic delivery of peptide/protein drugs and compare the effect of hydrophobic difference between the peptides drugs on the skin permeability. Transport of angiotensin II and its antagonists through excised rabbit pinna skin were enhanced with iontophoresis by monophase periodically pulsed current, amplituide=1mA, frequency=1000Hz and on/off ratio equals 50%. The delivery rate was proportional both to the current intensity and pulse duration of the stimulation. Results showed that the permeation rate of [Sar, Ile] Angiotensin II > [Sar,Ala]Angiotensin II > Angiotensin II. Iontophoretic mobility and hydrophobicity were the key factors dominating the transdermal iontophoretic delivery rate of angiotensin II and its antagonists.