||Development and Biomechanical Evaluation of Wheelchair Seating System
||Department of BioMedical Engineering
Elderly adults with lower limb disorders sitting on a wheelchair for an extended period of time may experience numerous complications. Critical complications in clinical practice include back pain, pressure ulcers, and decreased pulmonary function. Wheelchair seating system is a key factor that influences spinal angle, back muscle activation, interface pressure, pulmonary function, and subjective discomfort. Although numerous studies on wheelchair seating systems have been conducted, it seems that the aspect of aforementioned problems can still be further improved. For reduce the risks of back pain, pressure ulcers, and decreased pulmonary function in wheelchair sitting posture. This study proposed a novel wheelchair seating system concept: the backward thoracic with upward femur support seating system. The purpose of this study was to evaluate the spinal angle, back muscle activation, interface pressure, pulmonary function, and subjective discomfort when using the backward thoracic with upward femur support seating system in the elderly population.
Twenty elderly people were recruited for this study. the backward thoracic with upward femur support sitting (TF) was compared with the relaxed slouching sitting (RS), flat back support sitting (FB), prominent lumbar support sitting (PL), and backward thoracic support sitting (BT). Spinal angle (thoracic, lumbar, and pelvic angles), back muscle activation (maximal voluntary isometric contraction of the thoracic erector spinae at T9, iliocostalis lumborum pars thoracis, lumbar erector spinae, and lumbar multifidus on both sides), interface pressure (total contact area, average pressure, and peak pressure on backrest and seat), pulmonary function (forced vital capacity, forced expiratory volume in 1 second, and peak expiratory flow), and subjective discomfort (neck, shoulder, upper-back, mid-back, lower-back, upper-arm, lower-arm, buttock, thigh, and leg) were measured and compared.
The results of spinal angle measurement: the TF showed relatively higher thoracic kyphosis and lumbar lordosis when compared with the RS, FB and PL, no significant difference when compared with the BT; and it also showed a relatively neutral pelvic tilt when compared with the RS and LP, no significant difference was observed when compared with the FB and BT. The results of back muscle activation measurement: the TF showed relatively higher back muscle activity when compared with RS and lower back muscle activity when compared with the FB and PL in all tested muscles, no significant differences when compared with the BT. The results of interface pressure measurement: the TF showed relatively higher total contact area, average pressure and peak pressure on backrest when compared with the other sitting postures; and the BT showed relatively lower average pressure and peak pressure on seat when compared with the other sitting postures; nevertheless, the TF showed relatively lower total contact area, average pressure, and peak pressure on the back part of seat and higher total contact area, average pressure, and peak pressure on the front part of seat when compared with the BT. The results of pulmonary function test: the TF showed relatively higher pulmonary function values when compared with the RS, FB, and PL in all tested parameters, no significant differences were observed when compared with the BT. The results of subjective discomfort evaluation: the TF showed relatively lower subjective discomfort in upper-back, mid-back, and lower-back when compared with the RS, FB, and PL, no significant difference when compared with the BT; and it also showed relatively lower subjective discomfort in buttock and higher subjective discomfort in thigh when compared with other sitting postures.
The backward thoracic with upward femur support seating system concept was suggested because it maintains an increased lumbar lordosis with rather neutral pelvic tilt, decreased back muscle activation, diminished pressure on the ischial tuberosities, improved pulmonary function, and lessened subjective discomfort in back and buttock which may help maintains a better wheelchair sitting posture for reduce the risks of back pain, pressure ulcers, and pulmonary function decline. The achievements of this study contribute to the decision-making processes of wheelchair seating systems for consumers, clinicians, and manufacturers.
LIST OF TABLES IX
LIST OF FIGURES X
CHAPTER 1 INTRODUCTION 1
1.1 Population ageing and wheelchair sitting complications 1
1.2 Sitting related to back pain 2
1.3 Sitting related to pressure ulcers 7
1.4 Sitting related to pulmonary function decline 11
1.5 Existing wheelchair seating system 13
1.6 Motivation and purposes 16
CHAPTER 2 MATERIALS AND METHODS 17
2.1 Participants 17
2.2 Wheelchair seating system design 17
2.3 Experimental protocol 20
2.4 Spinal angle measurement 22
2.5 Back muscle activation measurement 25
2.6 Interface pressure measurement 27
2.7 Pulmonary function test 28
2.8 Subjective discomfort evaluation 30
2.9 Statistical analysis 31
CHAPTER 3 RESULTS 32
3.1 Recruited participants 32
3.2 Outcome of spinal angle measurement 32
3.3 Outcome of back muscle activation measurement 35
3.4 Outcome of interface pressure measurement 37
3.5 Outcome of pulmonary function test 41
3.6 Outcome of subjective discomfort evaluation 43
CHAPTER 4 DISCUSSION 46
4.1 Investigation of spinal angle with each sitting posture 46
4.2 Investigation of back muscle activation with each sitting posture 47
4.3 Investigation of interface pressure with each sitting posture 48
4.4 Investigation of pulmonary function with each sitting posture 49
4.5 Investigation of subjective discomfort with each sitting posture 51
4.6 Limitations 52
CHAPTER 5 CONCLUSION 53
5.1 Achievements 53
5.3 Future works 53
APPENDIX: HUMAN STUDY APPROVAL 65
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