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Analysis of Wrist Brace Design for the Prevention of Carpal Tunnel Syndrome

 

Abstract:

            The objective of this project is to test three different wrist braces and quantify their ability to prevent extreme motion in wrist flexion, wrist extension, radial deviation and ulnar deviation.  Seven subjects were chosen: 4 women and 3 men.  Joint angles were measured without the brace and with each brace on.  The subjects were then asked to perform a timed task (typing a specific passage) to quantify the impedance of the wrist braces.  These values were compared to the time that it took to type without a brace.  After the tests were completed, the subjects were asked to fill out a survey comparing the braces.  The data was plotted and the performance impedance and angle measurements were compared to determine which brace was best in the prevention of extreme angles while not excessively impeding the performance of tasks.  From the data collected and the analysis performed, it seems that the metal brace performed best.  It did not, however, perform well in preventing wrist extension.  Therefore, a possible alteration to the design was suggested.  The new design will help prevent extension of the wrist.

Literature Review

We could not find literature sources on research dealing with braces for carpal tunnel syndrome.  However, there were many literature sources about other aspects of carpal tunnel syndrome.

Brahme, S., J. Hodler, R. M. Braun, C. Sebrechis, W. Jacksn, and D. Resnick. 1997. Dynamic MR imaging of carpal tunnel syndrome, Skeletal Radiology 26:482-487.

Carter, R., T. Hall, C. B. Aspy, and J. Mold. 2002. The effectiveness of magnet therapy for treatment of wrist pain attributed to carpal tunnel syndrome, The Journal of Family Practice 51: 38-40.

Gross, C.M., J.D. Lloyd, A. Nelson, and R.A. Haslam. Carpal Tunnel Syndrome: A review of Literature with Recommendations for Further Research

Gerritsen, Annette, Marc de Krom, Margaretha Struijis, Rob Scholten, Henrica de Vet, and Lex Bouter. Conservative Treatment Options for Carpal Tunnel Syndrome: A systematic review of randomized controlled trials. 

Brahme, Sevil, Juerg Hodler,  Richard Braun, Christopher Sebrechts, William Jackson and Donald Resnick.  Dynamic MR Imaging of Carpal Tunnel Syndrome.

Objectives:

            The objectives of this project are to evaluate different designs for wrist braces, analyze which brace performs best under typing tests, and determine what possible alterations could be made to correct any problems that the brace experiences.

Background Information:

            Carpal Tunnel Syndrome (CTS) is a compression neuropathy of the median nerve at the wrist.  Any condition that reduces the size of the carpal tunnel or increases the volume of the carpal tunnel will cause compression of the median nerve.

 

 

The median nerve affects a large portion of the hand.  The Thumb and the first two or three fingers are affected as well as the palm of the hand. 

            There are many schools of thought about the causes of Carpal Tunnel Syndrome.  However, most researchers agree that the compression and irritation of the median nerve is caused by cumulative microtrauma to the soft tissue structures that pass through the carpal tunnel.  This is unlike many sport or job related injuries, where the injury is caused by an instantaneous break or tear of the tissues or bones.  This makes the factors that cause carpal tunnel syndrome less noticeable to the patient, however, the damage caused is no less debilitating.  It has been found that repetitive exertion of the wrist in unsafe positions can be a major contributor to such damage.

 

Common causes of Carpal Tunnel Syndrome are:

-         injuries from sports such as racquetball and handball

-         typing

-         painting

-         driving

-         sewing

-         assembly-line work

-         writing

-         use of tools

-         other similar activities.

Some common symptoms of Carpal Tunnel Syndrome are:

-         weakness in the hand

-         numbness or tingling in the thumb and next 2 or 3 fingers

-         hand numbness or tingling of the palm of the hand

-         wrist or hand pain can occur

-         impaired fine finger movements (coordination) in hand

-         weak grip or difficulty carrying bags is common

Treatment for carpal tunnel syndrome is a big area of concern because so many people suffer from it.  There are many forms of treatment with a large range of advantages and disadvantages.  When detected early, patients can undergo “conservative” treatment.  This generally includes methods and devices that are non-invasive and the treatment is much less expensive.  Recovery time, if any at all, is minimal.  

There are four main types of conservative treatment:

-         restricting motion and splinting to immobilize the area

-         applying heat or cold to the area in order to facilitate the repair process

-         medications and injections in order to reduce inflammation and pain   (example: anti-inflammatory analgesics (NSAIDs) and corticosteroids)

-         special exercises to promote circulation

If the carpal tunnel syndrome is not detected until it is severe, non-conservative methods are generally required to correct the problem.  This usually involves a surgical procedure to cut part of the ligaments in the carpal tunnel in order to relieve pressure on the median nerve.

            The purpose of our project was to evaluate the effectiveness of three different wrist braces compared to wearing no brace at all.  After analysis is complete, recommendations and possible alteration suggestions will be made. 

 

Methods and Materials

Seven subjects were chosen to test the wrist braces.  Wrist angle data was collected using an electric goniometer.

 

A goniometer is a device used to

 measure angles.  It is normally used

 to find the range of motion for joints.

 In clinical studies, it has proven useful

 in comparing the effects of treatments

 on human movements.

                                                                                                    

In order to determine the performance impedance of the various wrist braces, the subjects were asked to type from a predetermined, passage that was chosen randomly from the Internet.  The subjects were informed to correct blatant errors that might be caused by the brace itself, but to ignore small errors in typing so as not to skew the data.  The writing sample can be seen in Appendix A.

After the anthropometric data was recorded and the typing tests completed, the subjects were asked to fill out a survey that asked their opinions on various aspects of the different braces.  The survey can be seen in Appendix B.  A summary of the responses to the survey is given in Appendix C.

Results:

 Maximum angles were recorded for each brace and for normal range of motion without the brace.  Data collected from the subjects regarding wrist angles can be seen in Appendix D.

Averaging the data, the general trends for angle deviation can be observed.

Measurements in degrees

 

Avg. Flexion

Avg. Extension

Avg. Radial Dev.

Avg. Ulna Dev.

No Brace

77.2857143

65.85714286

26.57142857

49.14285714

Splint

26

43.57142857

10.85714286

28

Generic

58.4285714

55.85714286

21.57142857

33.42857143

Metal

24.4285714

37.42857143

16.71428571

25.14285714

Average % of Normal

Splint

33.6414048

66.16052061

40.86021505

56.97674419

Generic

75.6007394

84.81561822

81.1827957

68.02325581

Metal

31.6081331

56.8329718

62.90322581

51.1627907

 

From the graphs above, it can be seen that the generic brace offers the least support for the four joint motions.  This is not surprising, considering that the brace was made from neoprene.  It was also very low cost, and its poor performance in wrist support was expected.  For the majority of the joint motions (excluding radial deviation), the splint brace was the second most supportive.  These results were surprising because the splint appeared to be the most bulky and restrictive.  It was, however, the most supportive in the radial deviation motion.  The most supportive wrist brace tested was the metal brace.  It provided the least range of motion in all but one direction.  An interesting note to make is that none of the wrist braces were very effective in preventing motion in extension.  Even the most restrictive, the metal brace, allowed 57 percent of the normal range of motion. 

Wrist Flexion –

From the graph, it can be seen that the generic is the worst brace for the flexion motion.  The majority of the subjects were able to perform around 90 percent of their normal motion with the brace on.  Both the splint and the metal brace do excellent jobs in the prevention of motion in the flexion direction.  Most subjects were only able to perform approximately 30 percent of the normal motion. 

Wrist Extension –

It is unclear from the graph which brace performs best in the prevention in wrist extension.  It appears that the generic brace is slightly less preventative, however, no brace excels in the prevention of this motion. 

 Radial Deviation –

Again, the generic wrist brace provides the least amount of prevention of radial deviation.  The metal brace is slightly better, with the splint brace providing the most preventive brace in the prevention of radial deviation.  The exact amount changes from person to person, however, the average for the splint is approximately 40 percent of the normal range of motion. 

Ulnar Deviation –

From the chart above and the chart for average percent angles, it is clear that the metal brace is the best brace for the prevention of motion in ulnar deviation.  On average, the subjects were only able to perform 51 percent of their normal range of motion.  The splint was also very effective, only allowing approximately 57 percent of the normal range of motion. 

Each subject’s data was also individually graphed to get a better view of his or her individual ranges of motion.  These graphs can be seen in Appendix D.  Data was also plotted in order to compare the various motions for each brace.  These charts can be seen in Appendix E.

Time Test:

The subjects were then asked to type a passage in order to test how much their typing performance was hindered by the braces.  A base time was obtained by recording the time it took to type the passage with no brace on.  The subjects were then asked to type the passage with each brace and their times were recorded.  The data below shows the data that was recorded.

 

Subject 1

Subject 2

Subject 3

Subject 4

Subject 5

Subject 6

Subject 7

Time (seconds)

No Brace

250

245

355

270

285

190

173

Splint

371

322

345

375

342

345

265

Generic

273

271

337

292

297

216

175

Metal

311

247

385

303

311

207

175

% of No Brace Time

 

Subject 1

Subject 2

Subject 3

Subject 4

Subject 5

Subject 6

Subject 7

Splint

148.4

131.4286

97.1831

138.8889

120

181.5789

153.1792

Generic

109.2

110.6122

94.92958

108.1481

104.2105

113.6842

101.1561

Metal

124.4

100.8163

108.4507

112.2222

109.1228

108.9474

101.1561

This graph shows the average percent times for the different braces.  The splint brace hindered performance the most.  The average performance time for this brace was 140 percent of the normal time.  The generic and metal brace were much better.  Their performance times were 106 and 109 respectively.  Times for the individual subjects are given in Appendix F.

Along with poor performance times, there is another problem with the splint brace.  In order to put the wrist in a position that was conducive to typing, the upper arm had to be abducted.  This caused unnecessary moments in the shoulder and many of the subjects complained that the splint brace caused there shoulder to hurt.  Appendix G is a 3DSSPP analysis of the neutral position and the abducted position.  In the abducted position, there is a 2.5 Nm moment exerted on the shoulder (this is using a .8 N force as the reaction force on the hands while typing).  

Conclusions and Recommendations:

            From the data collected and the tests performed, it appears that the metal brace is the best choice for the patient who is interested in a brace that offers good support and that does not impede the performance of certain tasks, like typing.  The brace offers excellent support in all motions except extension, however, no brace performed well in the extension motion.  The brace is sturdy and well designed.  For someone who does not need to perform intricate hand tasks and for people who wish to wear a brace during the night, the splint brace may be a wise choice.  It offers very good support, however, limits your ability to perform tasks.  The generic brace performed very poorly in all support categories, though it was better than wearing no brace at all.  It provided almost no impedance in the performance tests that were done.  It was also very cheap.  This brace might be a good choice for someone at risk for carpal tunnel syndrome and who wishes to take precautions against it. 

Due to the poor performance of all in the braces in the prevention of motion in extension, a possible alteration can be suggested.  None of the braces feature a restraint on the top of the wrist, so our suggestion would be the addition of a support into the brace at the top of the wrist.  Drawings of the current metal bar design and the alternative design can be seen in Appendix H and Appendix I, respectively.

References:

Brahme, S., J. Hodler, R. M. Braun, C. Sebrechis, W. Jacksn, and D. Resnick. 1997.

Dynamic MR imaging of carpal tunnel syndrome, Skeletal Radiology 26:482-487.

Brahme, Sevil, Juerg Hodler,  Richard Braun, Christopher Sebrechts, William Jackson

and Donald Resnick.  Dynamic MR Imaging of Carpal Tunnel Syndrome.

Carter, R., T. Hall, C. B. Aspy, and J. Mold. 2002. The effectiveness of magnet therapy

for treatment of wrist pain attributed to carpal tunnel syndrome, The Journal of Family Practice 51: 38-40.

Erselcan, Topalkara, Nacitarhan, Akyuz, and Dogan.  2001.  Carpal tunnel syndrome

Leads to significant bone loss in metacarpal bones.  Journal of Bone and Mineral Metabolism.  19:317-320.

Gerritsen, Annette, Marc de Krom, Margaretha Struijis, Rob Scholten, Henrica de Vet,

and Lex Bouter. Conservative Treatment Options for Carpal Tunnel Syndrome: A  systematic review of randomized controlled trials. 

Gross, C.M., J.D. Lloyd, A. Nelson, and R.A. Haslam. Carpal Tunnel Syndrome: A

review of Literature with Recommendations for Further Research.

http://handlibrary.org/membersonly/featureca ses/feature1197.html

http://www.ergodmx.com/articles/article_7.html

http://www.medicalmultimediagroup.com/pated/ctd/cts/cts.html

http://www.mailtriseorthop.com/corpusmaitri/othopaedic/dumontier_synth/dumontier_us.shtml

http://www.worldortho.com/database/exam-orth/eo057.html

Putz-Anderson V.  Cumulative Trauma Disorders – A manual for musculoskeletal

            diseases of the upper limbs; 1988 Taylor and Francis, New York.

Phalen G. Carpal tunnel syndrome – Seventeen years experience in diagnosis and

treatment of 654 hands.  Journal of Bone and Joint Surgery 48A (s); 1966

Robbins, H.  Anatomical study of the median nerve in the carpal tunnel and the etiologies

of the carpal tunnel syndrome.  Journal of Bone and Joint Surgery 45A; 1963.

 

Appendix A:

The flexor tendons are important because they allow us to move the fingers and the hand, such as when we grasp objects.  The tendons are covered by a material called tenosynovium.  The tenosynovium is very slippery, and allows the tendons to glide against each other as the hand is used to grasp objects.  Any condition which causes irritation or inflammation of the tendons can result in swelling and thickening of the tenosynovium.  As the tenosynovium covering all of the tendons begin to swell and thicken, the pressure begins to increase in the carpal tunnel – because the bones and ligaments that make up the tunnel are not able to stretch in response to the swelling.  Increased pressure in the carpal tunnel begins to squeeze the median nerve against the transverse carpal ligament – because the nerve is the softest structure in the carpal tunnel.  Eventually, the pressure reaches a point when the nerve can no longer function normally.  Pain and numbness in the hand begins. 

 

Appendix B:

Wrist Brace Survey

-         On a scale of 1-10 (1 being the least restrictive and 10 being the most restrictive), how would you rate the range of motion of the wrist while using this brace?                                 

_________________

-         On a scale of 1-10 (1 being the least comfortable and 10 being the most comfortable), how would you rate the comfort of this brace?

_________________

-         On a scale of 1-10 (1 being the least comfortable and 10 being the most comfortable), how would you rate the temperature of this brace while in use?

_________________  

-         On a scale of 1-10 (1 being no support and 10 being a totally sufficient amount of support), how would you rate the amount of support this brace offers?

_________________  

-         On a scale of 1-10 (1 being the least restrictive and 10 being the most restrictive), how would you rate the range of motion of the fingers while using this brace?

_________________

-         Do you feel that using this brace improves the angles of your wrist while typing?

_________________

-         Do the positive effects of this brace outweigh the negative aspects?

_________________

-         Which brace do you feel does the best job of holding your wrist in the proper position while typing?

_________________

-         If given the choice, what brace would you use and why?

 

 

 

-    Does the brace cause pain in any other areas and if so where?

 

 

-         What improvements do you feel could be made to the wrist braces?

 

 

 

 

 

 

 

Appendix C:

Survey Responses

Splint / Generic / Metal

-         On a scale of 1-10 (1 being the least restrictive and 10 being the most restrictive), how would you rate the range of motion of the wrist while using this brace?

Average Response:   7.4 / 3.8 / 4.8

-         On a scale of 1-10 (1 being the least comfortable and 10 being the most comfortable), how would you rate the comfort of this brace?

Average Response:  2.8 / 6.4 / 5.2

-     On a scale of 1-10 (1 being the least comfortable and 10 being the most comfortable), how would you rate the temperature of this brace while in use?

Average Response:  3.8 / 4.4 / 5.2 

-         On a scale of 1-10 (1 being no support and 10 being a totally sufficient amount of support), how would you rate the amount of support this brace offers?

Average Response:  6.8 / 3.8 / 5.4

-         On a scale of 1-10 (1 being the least restrictive and 10 being the most restrictive), how would you rate the range of motion of the fingers while using this brace?

Average Response:  7.6 / 4.8 / 5.0

-         Do you feel that using this brace improves the angles of your wrist while typing?

Average Response:  No / No / No

-         Do the positive effects of this brace outweigh the negative aspects?

Average Response: No / No / Yes

-         Which brace do you feel does the best job of holding your wrist in the proper position while typing?

   Metal Brace

-         If given the choice, what brace would you use and why?

1)      Did not restrict typing, but held wrist at proper angle without limiting movement.

2)      The generic brace offers minimal support, but just enough to be comfortable.

3)      Generic, the most comfortable and least restrictive.

4)      Metal, because it isn’t as hot, uncomfortable and limiting as the splint, yet offers more support than generic.

5)      Metal, because it is easier to type with.

-         Does the brace cause pain in any other areas and if so where?

1)      Splint, no movement in of the wrist, shoulder had to compensate, causing fatique.

2)      No pain.

3)      Splint, put hand and arm in unnatural position.

4)      Spint, straps are uncomfortable, material is very hot.

5)      No pain.

-         What improvements do you feel could be made to the wrist braces?

1)      Generic- too flimsy with no real support, stiffer material would help.

2)      Generic- Additional support, could be added, and material that could breath.

3)      Splint- Allow more supportive movement, instead of totally restricting movement.

4)      Generic- some support

Splint- make it cooler, better straps, and allow for thumb movement.

Metal- Have softer material.

5)      Generic- no support and not restriction

Splint- Better thumb movement

Metal- More comfortable insert between thumb and index finger.

 

Appendix D: 

Subject 1:   Angle measurement (degrees) and the % of normal motion

 

Flexion

Extension

Radial Dev.

Ulna Dev.

% of Normal

No Brace

64

55

22

46

 

Flexion

Extension

Radial Dev.

Ulna Dev.

Splint

20

48

12

34

Splint

31.25

87.272727

54.55

73.91

Generic

50

51

15

38

Generic

78.125

92.727273

68.18

82.61

Metal

17

40

19

32

Metal

26.563

72.727273

86.36

69.57

Subject 2:    Angle measurement (degrees) and the % of normal motion

 

Flexion

Extension

Radial Dev.

Ulna Dev.

% of Normal

No Brace

78

67

42

53

 

Flexion

Extension

Radial Dev.

Ulna Dev.

Splint

29

55

9

47

Splint

37.179

82.089552

21.43

88.68

Generic

68

59

37

41

Generic

87.179

88.059701

88.1

77.36

Metal

37

57

28

42

Metal

47.436

85.074627

66.67

79.25

Subject 3:   Angle measurement (degrees) and the % of normal motion

 

Flexion

Extension

Radial Dev.

Ulna Dev.

% of Normal

No Brace

73

62

15

40

 

Flexion

Extension

Radial Dev.

Ulna Dev.

Splint

26

57

9

20

Splint

35.616

91.935484

60

50

Generic

53

56

12

20

Generic

72.603

90.322581

80

50

Metal

32

47

17

13

Metal

43.836

75.806452

113.3

32.5

Subject 4:   Angle measurement (degrees) and the % of normal motion

 

Flexion

Extension

Radial Dev.

Ulna Dev.

% of Normal

No Brace

87

73

33

44

 

Flexion

Extension

Radial Dev.

Ulna Dev.

Splint

27

37

12

22

Splint

31.034

50.684932

36.36

50

Generic

76

71

28

44

Generic

87.356

97.260274

84.85

100

Metal

33

39

16

27

Metal

37.931

53.424658

48.48

61.36

Subject 5:    Angle measurement (degrees) and the % of normal motion

 

Flexion

Extension

Radial Dev.

Ulna Dev.

% of Normal

No Brace

70

67

20

42

 

Flexion

Extension

Radial Dev.

Ulna Dev.

Splint

21

41

19

9

Splint

30

61.19403

95

21.43

Generic

51

46

20

26

Generic

72.857

68.656716

100

61.9

Metal

7

12

3

9

Metal

10

17.910448

15

21.43

Subject 6:    Angle measurement (degrees) and the % of normal motion

 

Flexion

Extension

Radial Dev.

Ulna Dev.

% of Normal

No Brace

81

71

27

50

 

Flexion

Extension

Radial Dev.

Ulna Dev.

Splint

44

39

9

38

Splint

54.321

54.929577

33.33

76

Generic

74

63

26

32

Generic

91.358

88.732394

96.3

64

Metal

26

34

15

31

Metal

32.099

47.887324

55.56

62

Subject 7:    Angle measurement (degrees) and the % of normal motion

 

Flexion

Extension

Radial Dev.

Ulna Dev.

% of Normal

No Brace

88

66

27

69

 

Flexion

Extension

Radial Dev.

Ulna Dev.

Splint

15

28

6

26

Splint

17.045

42.424242

22.22

37.68

Generic

37

45

13

33

Generic

42.045

68.181818

48.15

47.83

Metal

19

33

19

22

Metal

21.591

50

70.37

31.88

 

 

Appendix E:

 

Appendix F:

 

Appendix G:

 

Appendix H:                                                                           3DSSPP Analysis

 

Appendix I:                                                                             Current Design

 

Appendix J:                                                                              Proposed Alteration