||Effects of External Compressive Force at the Carpal Tunnel on the Bowstringing Effect of the Flexor Tendon
||Department of BioMedical Engineering
carpal tunnel syndrome
external compressive force
本研究以十五位健康成人以及十三位進行腕隧道解離手術之腕隧道症候群患者為研究對象。健康成人以慣用手之中指作為施測手指，患者則以患側手之中指來進行施測。在施測過程中會在受試者的腕隧道上施加不同的外部下壓力，健康成人分別施加輕觸力(just contact force)、2牛頓、4牛頓、6牛頓和8牛頓力，腕隧道症候群患者的外部下壓力則為輕觸力、4牛頓及8牛頓力。施加外部下壓力的同時也記錄在腕隧道以及掌指關節處屈指肌腱的超音波影像，並利用荷重元調整腕隧道上的外部下壓力及紀錄施測過程中的力值變化。
Patients with carpal tunnel syndrome (CTS) undergo carpal tunnel release (CTR) surgery to decompress the carpal tunnel pressure in the carpal tunnel by transecting the transverse carpal ligament (TCL). However, previous studies reported that the lack of the TCL causes the bowstringing phenomenon of the flexor tendon and increases the incidence of trigger finger. In the current study, it is considered that applying external compressive force on the carpal tunnel may be able to restrict the bowstringing phenomenon. The purpose of the study is to investigate the effect of different compressive force on the flexor tendon and find out the effective and appropriate force for eliminating the bowstringing effect after CTR surgery.
There were fifteen healthy subjects and ten CTS subjects who underwent ultrasonographically guided percutaneous CTR surgery in the study. Subjects were asked to flex the middle finger while applying different external compressive force on the top of the carpal tunnel. Compressive forces in healthy subjects were just contact, 2N, 4N, 6N, 8N force. CTS subjects were compressed just contact, 4N, and 8N force on the carpal tunnel. Images of the flexor tendon within the carpal tunnel and at the MCP joint were recorded by the ultrasound. Compressive force on the carpal tunnel was detected by the loadcell.
The flexor tendon positions and angles between the flexor tendon and metacarpal bone decrease as external compressive force increases. It may suggest that applying compressive force on the carpal tunnel can restrict excessive movement of the flexor tendon resulting from CTS patients cutting the TCL. Compressing just contact force on healthy and CTS subjects in the pre-surgery has significant differences compared with 4N and 8N in the post-surgery. It may represent that 4N and 8N force results in more normal force on the surface between the flexor tendon and the TCL and will cause greater frictional force and carpal tunnel pressure, which may result in the recurrence of CTS.
List of Figure VIII
Chapter 1 Introduction 1
1.1. Background 1
1.1.1. Anatomy of carpal tunnel 1
1.1.2. Anatomy of hand digit 2
1.1.3. Carpal tunnel syndrome 4
1.1.4. Trigger finger 4
1.1.5. Carpal tunnel release 5
1.1.6. Relation of trigger finger and carpal tunnel release 7
1.1.7. Effect of external force on the carpal tunnel 8
1.2. Motivation 8
1.3. Hypotheses and purposes 9
Chapter 2 Materials and Methods 10
2.1. Subjects 10
2.2. Experimental apparatuses 11
2.2.1. Ultrasound 11
2.2.2. Loadcell 11
2.2.3. Custom-designed dynamometer 12
2.3. Experimental procedure 13
2.4. Parameters 17
2.4.1. Part one: The effect on the flexor tendon migration 17
220.127.116.11. Tendon position 17
18.104.22.168. The height of the carpal tunnel 18
22.214.171.124. The normalized tendon position 18
126.96.36.199. Volar-dorsal migration 19
188.8.131.52. The normalized volar-dorsal migration 19
2.4.2. Part two: The effect on the entrance angle of the flexor tendon 19
184.108.40.206. Angle between the flexor tendon and metacarpal bone 19
220.127.116.11. Change in the entrance angle 21
2.4.3. Loadcell force on the carpal tunnel 21
2.5. Statistical analysis 22
Chapter 3 Results 23
3.1. Healthy subjects with different compressive force on the carpal tunnel 23
3.1.1. Tendon position 23
3.1.2. Angle between the FDS tendon and metacarpal bone 24
3.1.3. Angle between the FDP tendon and metacarpal bone 26
3.2. CTS subjects in the pre- and post-surgery with different compressive force on the carpal tunnel 28
3.2.1. Tendon position and volar-dorsal migration 28
3.2.2. The height of the carpal tunnel 30
3.2.3. The normalized tendon position and volar-dorsal migration 30
3.2.4. Angle between the FDS tendon and metacarpal bone and change in the entrance angle of FDS tendon 32
3.2.5. Angle between the FDP tendon and metacarpal bone and hange in the entrance angle of FDP tendon 34
3.2.6. Force measured on the carpal tunnel 36
3.3. Healthy subjects and CTS subjects in the post-surgery with different compressive force on the carpal tunnel 38
3.3.1. Tendon position and volar-dorsal migration 38
3.3.2. The height of the carpal tunnel 40
3.3.3. The normalized tendon position and volar-dorsal migration 40
3.3.4. Angle between the FDS tendon and metacarpal bone and change in the entrance angle of FDS tendon 42
3.3.5. Angle between the FDP tendon and metacarpal bone and change in the entrance angle of FDP tendon 44
3.3.6. Force measured on the carpal tunnel 46
Chapter 4 Discussions 48
4.1. Healthy subjects with different compressive force 48
4.1.1. The effect within the carpal tunnel 48
4.1.2. The effect at MCP joint 49
4.1.3. The force on the carpal tunnel 49
4.2. Comparison of the effect of different compressive force 50
4.2.1. Tendon position 51
4.2.2. Volar-dorsal migration 52
4.2.3. The height of the carpal tunnel 53
4.2.4. The normalized tendon position 53
4.2.5. The normalized volar-dorsal migration 54
4.2.6. Angle between the flexor tendon and metacarpal bone 55
4.2.7. Change in the entrance angle of the flexor tendon 56
4.2.8. The force on the carpal tunnel 57
4.3. Limitations 59
Chapter 5 Conclusion 60
Appendix I 64
6.1. CTS subjects in the pre-surgery with different compressive force on the carpal tunnel 64
6.1.1. Tendon position and volar-dorsal migration 64
6.1.2. The height of the carpal tunnel 65
6.1.3. The normalized tendon position and volar-dorsal migration 66
6.1.4. Angle between the FDS tendon and metacarpal bone and change in the entrance angle of FDS tendon 67
6.1.5. Angle between the FDP tendon and metacarpal bone and change in the entrance angle of FDP tendon 68
6.1.6. Force measured on the carpal tunnel 69
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