Download Design Problem and Design Brief

DUALEVE
Chief Executive Officer: Peter Wallerson
Chief Marketing Officer: Han You
Chief Technical Officer: Sun Murray Han
Chief Regulatory Officer: Zwoisaint Mears-Clarke
Chief Financial Officer: Angel Castro
1
Table of Contents
I.
II.
III.
IV.
V.
VI.
VII.
Design Problem and Design Brief
Research
Design Fundamental Requirements and Constraints
Preliminary Designs
Decision Matrix
Proof of Concept Plan
Proof of Concept Outcome
Page 1
Page 3
Page 40
Page 43
Page 48
Page 50
Page 53
1
I
Design Problem and Design Brief
2
i.
Design Problem
Long term wheel chair users have a high incidence of upper body pain, fatigue, and
injury due to increased upper limb usage. Current solutions have been found to be inadequate in
solving the problem: wrist braces are restrictive and can cause muscle atrophy in wrist flexors
and extensors, electric wheelchairs can cost upwards of $1000 and usually require a prescription
(and also cause muscular atrophy), surgery is both invasive and carries a high risk of nerve
damage. Additionally, other forms of alternative propulsion wheelchairs simply transfer the
unhealthy loading form one body part to another, and attract a lot of unwanted attention to their
users.
ii. Design Brief
We propose to develop a new device that reduces the incidence of upper body injury in
long term manual wheel chair users. The device will be (most importantly) discrete, nonrestrictive, affordable for average consumers, and non-invasive.
iii. Solution Neutral Needs Statement
A way to reduce the incidence of upper body injury in long term manual wheel chair
users.
3
II
Research
4
A. Basic Summary of the Problem – Upper body injuries due to
Manual Wheelchair use
A1. W HEEL C HAIR USE
i) T YPES OF WHEELCHAIRS
There are a number of ways to classify wheelchairs, but generally, they can be separated
into two inclusive categories. There is a category of wheelchairs which are designed for
daily mobility and a category of wheelchairs which are designed with a specific sport in
mind. This separation can be made since the types of biomechanical stressors each
category experiences are likely to be different. While there is overlap between the injuries
suffered between users of chairs in both categories, the focus will be placed on
wheelchairs used for daily mobility.
For everyday use, persons with mobility limitations may use:
 manual wheelchairs
 push-rim activated power-assisted wheelchairs (PAPAWs)
 battery-powered wheelchairs
 scooters
ii) D EMOGRAPHICS
In December of 2008, the United States Census Bureau released the Americans with
Disabilities: 2005 report. In this report, the population with lower body limitations was of
our concern. Of people aged 15 and older:




~ 27.4 million (11.9%) had difficulty with ambulatory activities of the lower body
~ 22.6 million people (9.8%) had difficulty walking a quarter of a mile and ~12.7
million were not able to perform this activity
~3.3 million people (1.4%) used a wheelchair or similar device
~10.2 million (4.4%) used a cane, crutches, or walker to assist with mobility.
This report, using data collected from June through 2005, provided estimates
representative of the civilian non-institutionalized population living in the US, meaning
that the disability statuses of people living in places such as nursing homes were not
included. Inclusion of this population would, on average, increase the estimate of
disability prevalence by about 0.6%. The American Community Survey provides detailed
and up-to-date estimates that can shed light on the current population and disability
prevalence as soon as 2009. According to ACS, in 2009, an estimated 19,425,100 out of
281,613,500 (6.9%) of the non-institutionalized population in the United States reported
an ambulatory disability.
5
Table 1. Wheelchair use, by age and gender
Any wheelchair
Manual wheelchair
Electric wheelchair
Number
(1000s)
% of
population
Number
(1000s)
% of
population
Number
(1000s)
% of
population
1,599
0.61
1,503
0.58
155
0.06
Under
18
88
0.12
79
0.11
18
0.02
18-64
614
0.39
560
0.35
90
0.06
65+
897
2.87
864
2.76
47
0.15
Male
658
0.52
606
0.48
84
0.07
Female
941
0.70
897
0.67
71
0.05
Total
Age
Gender
iii) B IOMECHANICS
Biomechanical studies have been done in order to produce an analysis of wheelchair
propulsion. Chow et al, summarize a number of these studies into three areas: kinematics,
kinetics, and muscle timing and activation. Kinematics provides a description of the
bilateral cycle motion that occurs in the turning of the wheels of a wheelchair. This cycle
starts at the instant the hand contacts the push-rim, and ends at the instant immediately
before the next hand contact on the same wheel. The instant the hand loses contact with
the rim (hand release) divides a stroke cycle into two phases – push and recovery phases.
Kinetics provides an analysis of the resulting
upper limb joint loads. The locations,
magnitudes, and directions of the force and
moment acting on the hand during the push
phase are used to determine the resultant joint
forces and moments using the inverse dynamic
approach. Contact forces and moments between
the hand and push-rim are usually measured
using either a wheelchair
ergometer/dynamometer or an instrumented
wheel. It has been shown that low intensity
wheelchair propulsion does not appear to lead
to high glenohumeral contact forces. However,
shoulder resultant joint forces and moments
increase considerably when pushing at faster
speeds up an incline or while fatigued.
6
Several studies have documented the muscle activation patterns during wheelchair
propulsion using surface and indwelling electromyographic (EMG) techniques. In
general, anterior deltoid, biceps brachii, triceps brachii, flexor carpi radialis, extensor
carpi radialis, and pectoralis major have been found to be active during the push phase,
while the middle and posterior deltoid muscles are identified as the prime movers during
the recovery phase. Cerquiglini et al. [89] found the latissimus dorsi to be most active
during the final phase of pushing, and the activity increased drastically when the
resistance of the wheelchair ergometer was increased to simulate a 2–3% incline. Using
indwelling EMG techniques to monitor different shoulder muscles, Mulroy et al. [47]
found the anterior deltoid, sternal portion of pectoralis major, supraspinatus,
infraspinatus, serratus anterior, and long head of biceps brachii to be active during the
push phase. The recovery phase muscles were middle and posterior deltoid,
subscapularis, supraspinatus, and middle trapezius. They did not observe any consistent
pattern of activity in the latissimus dorsi. They concluded that the pectoralis major,
supraspinatus, and all recovery muscles were most vulnerable for fatigue.
A2. I NJURIES
Wheelchair propulsion is very stressful to the musculoskeletal structures of the upper limb; however
the incidence of musculoskeletal problems in wheelchair users is poorly documented. Physicians who
frequently care for these patients recognize that pain in the arms is considerably more frequent than in
the general population. Nichols et al. observed that 51.4% of respondents to a questionnaire, sent to
members of the Spinal Injuries Association in Great Britain, suffered shoulder pain. The actual
lesions causing pain were not identified. It appears that patients at greatest risk are those with
weakness of arm muscles (e.g., patients with neuromuscular disorders and rheumatoid arthritis).
Painful conditions of the arms are predictable; for the wheelchair bound person the arms are the limbs
of mobility and weight bearing. For the very active, the arms are subjected to unusual stresses many
times a day, in supporting the person's weight when transferring from chair to bed, toilet, car and
other seats. Intercurrent causes of arm pain include musculotendinous rotator cuff disorders, cervical
disorders with referred pain to the arm, acromioclavicular strain, tendinitis and bursitis of the elbow,
strains and sprains of tendon and ligament structures of wrists and hands. The mechanical stresses
sustained by the arm and hand joints would predispose them to early degenerative changes. Another
complaint, not commonly recognized, is carpal tunnel syndrome. This neuropathy has a predilection
for people who perform repetitive movements with their wrists.
iv) S HOULDER
A. E TIOLOGY /P HYSIOLOGY
Shoulder overuse is believed as major factor in causing shoulder pain [1–3]. Additionally,
using inappropriate manual technique in performing wheelchair propulsion may be another
reason in causing shoulder pain. Although the underlying etiology of shoulder pain in this
population is not understood completely, ‘impingement’ of the subacromial structures during
transfer or wheelchair activities has been suggested as one of the major causes of this
problem. The impingement refers to the mechanical phenomenon in which contact between
the anterior aspect of the humerus and the acromial arch creates compressive force on the
subacromial structures when the glenohumeral joint (GHJ) is moved. When the compressive
7
force is sufficiently large or if the impingement is repeated over a long period of time,
pathological conditions such as bursitis, tendonitis or rupture of rotator cuff tendons may
develop. Shoulder impingement pain usually occurs when wheelchair user places his or her
arm in position of flexion abduction and internal rotation. Pain often locates between the top
of the humerus (arm bone) and the acromion (tip of the shoulder).
According to Cooper, Boninger et al in a paper published in 1998, “the most common
disparity in strength associated with rotator cuff tear or tendinitis is an imbalance between the
internal and external rotators of the shoulder.”1 Furthermore, “shoulder muscle
imbalance, with comparative weakness of the humeral head depressors (rotators and
adductors), may be a factor in the development and perpetuation of rotator cuff
impingement syndrome in wheelchair athletes”2 and wheelchair users in general. “As
a result of years of wheelchair propulsion, shoulder muscles active during the push
phase are believed to become stronger, whereas the muscles that are involved during
the recovery phase remain at the same strength”3.
B. D EMOGRAPHICS
Manual wheelchair users frequently complain about shoulder pain [1–3]. It has been
estimated that between 30% and 70% of wheelchair users complained of past or current
shoulder symptoms [1].
v) CTS
A. A NATOMY /P HYSIOLOGY
The carpal tunnel is bordered dorsally by the concave arch of the carpus and volarly
by the transverse carpal ligament (TCL), with a variable depth of 10 to 13 mm.6 Ten
structures from the volar forearm pass through the carpal tunnel—nine flexor tendons
and the median nerve (Figure 1). The median nerve is the most superficial structure
within the canal, entering the space in the midline or just radial to the midline. The
median nerve may divide in the forearm or split within the carpal tunnel. Both
conditions are associated with a persistent median artery. The thenar motor branch of
the median nerve usually originates in an extraligamentous position distal to the TCL.
Less commonly, the motor branch projects from beneath the TCL (subligamentous)
or perforates through the TCL (transligamentous).7 The median nerve is susceptible
to compression within the carpal canal because of the unyielding fibroosseous
borders. Normal pressure within the carpal tunnel measures 2.5mmHg. A decrease in
epineural blood flow and edematous changes occur when the pressure reaches 20 to
30 mm Hg. At pressures >30 mm Hg, nerve conduction diminishes. A continued rise
or a prolonged elevation in pressure may lead to a complete median nerve block.
1. Ambrosio, F. B., & al, e. (2005). Biomechanics and Strength of Manual Wheelchair Users. Journal of
Spinal Cord Medicine , 407-414.
2. Burnham, R. S. (1993). Shoulder pain in wheelchair athletes. The American Journal of Sports Medicine
, 238-242.
3. Cooper, R. A., Boninger, M. L., & Robertson, R. N. (1998). Heavy Handed: Repetitive Strain Injury
Among Manual Wheelchair Users. TEAMR EHA Report 35 , 35-38.
8
B. E TIOLOGY
Acute CTS is caused by a rapid and sustained increase in pressure within the carpal
tunnel. The onset of symptoms is sudden and may prompt a decision for urgent
surgical decompression. Precipitating factors producing acute CTS include wrist
trauma, infection, high-pressure injection, and hemorrhage.11 Chronic CTS is a much
more frequent condition, with the pathogenesis divided into four categories:
idiopathic, anatomic, systemic, and exertional.
C. E XERTIONAL
In the workplace, CTS has been attributed to repetitive use of the wrist and digits, to
repeated impact on the palm, and to the operation of vibratory tools.17-19 Extremes
of wrist flexion and extension have been shown experimentally to elevate pressure
within the carpal tunnel.9 Finger flexion also increases the interstitial canal pressure
as the lumbrical muscles are drawn proximally.20 Task-related factors are variable
and inconsistent, however, and the mechanisms by which they may contribute to CTS
are poorly defined.19 A direct relationship between repetitive work activity (eg,
keyboarding) and CTS has never been objectively demonstrated.
D. K INETICS
Average peak wrist joint angles during the push phase were: ulnar deviation, -24 ±
11° radial deviation, 13 ± 12° flexion, -14 ± 18° extension, 34 ± 16°. The values for
ulnar and radial deviation were close to normal values for maximal range of motion
(ROM) found in the literature. Peak extension was approximately 50% of ROM. The
peak angles which occurred with concurrent activity of the wrist flexors were: ulnar
deviation, -22 ± 11° radial deviation, 13 ± 10° flexion, -16 ± 15° extension, 32 ± 16°
(Veeger et al, 1998). The large deviation and extension angles, especially those
recorded simultaneously with wrist flexor activity, are serious risk factors for CTS.
This finding may help explain the high rates of CTS in the wheelchair user
population.
Gellman et al (4) found a serious elevation of pressure in the carpal tunnel when the
wrist was in full active flexion or full active extension. They suggest that the etiology
of CTS in the WU population may be a combination of the repetitive trauma from the
propulsion of a handrim wheelchair and of ischemia resulting from increases in
pressure in the carpal tunnel during extreme extension. Combination of the above
indicates that wrist movement and muscular activity pattern during handrim
wheelchair propulsion may be important factors in the development of CTS in the
WU population.
E. D EMOGRAPHICS
In a study by Aljure et al (1985), the incidence of carpal tunnel syndrome at 1-10
years from injury onset was; 54% at 11 - 20 years from injury onset; around 54% at
21 - 30 years from injury onset; and then a significant increase to 90% at 31+ years
from injury onset. This study suggests median and ulnar nerve functional testing
within 5 years of injury even if the person is asymptomatic, with periodic reevaluations after that. With this in mind, the best treatment for carpal tunnel becomes
prevention.
9
A3. WHO IS THE CUSTOMER?
We expect our device to be purchased by insurance companies and long-term manual
wheelchair users. How do insurance companies decide what can be reimbursed?
1) In most cases, a committee is charged with the responsibility for coverage policy. The
committee is chaired by one of the corporate medical directors. The request for coverage
can be initiated by a provider, by a patient, or by a manufacturer.
2) At a minimum, payers (e.g. medical insurance companies) require that the device have
Food and Drug Administration (FDA) approval before even considering a review.
3) Payers will look for unbiased clinical literature that documents the safety and the efficacy
of the product. Most payers use an external assessment company (e.g. Hayes, ECRI, or
the Blue Cross Blue Shield Technology Evaluation Center) to review the literature and
provide a recommendation. The payer may supplement the information with its own
literature review, or it may use outside clinical consultants to review the data.
4) Physician advocacy is an extremely important component of the coverage decision
making process. The more physicians who indicate an interest and belief in the product,
the stronger the case will be. If the manufacturer initiates a coverage review, it is
important to identify a group of supporting physicians who are willing to champion the
product to a payer. The physicians should be participants in the payer’s network and
ideally should be viewed as leaders within the community.
5) After reviewing all of the documentation, the committee makes a final determination.
Although the time frame varies, most decisions are made within six months.
6) If the payer decides to deny coverage, there is generally an appeals process within each
state. Therefore, if our product is to be reimbursed, it needs to be FDA approved, safe and
effective, and strongly endorsed by clinicians. There could be a delay between starting to
sell and have patients use the product, and the cost of the product being reimbursed by
the patient’s insurance company.
A4. WHO IS THE USER?
Our product will be directed towards those who are long term manual wheelchair users. We
expect that most users will be 15-60 years old. This is a broad age group, but there are
common uniting factors. Users will be unwilling to use a device that is indiscrete and calls
more attention that a standard wheelchair. Users will want a device that is simple to learn,
and does not require much more effort to use than a standard wheelchair.
A5. S UMMARY
10
What we propose is a low-cost device that provides users with at least the same mobility that
a wheelchair does, while reducing and/or eliminating stress felt on the upper body. This can
be achieved by engaging major muscle groups that can handle repetitive strenuous motion
and avoiding placement of the wrist and shoulders in an unnatural, deteriorative state. The
prospective customer of this interface would be insurance companies and the end-user. A
cost-effective product will allow the end-user to purchase the device without the need of an
insurance company. But those with insurance will potentially have theirs covered by
insurance companies, since this would prevent future medical issues that cost insurance
companies more money later on.
B . E XISTING P RODUCTS
Current products to treat carpal tunnel include wrist splint to restrict wrist movement,
nonsteroidal anti-inflammatory drugs to relieve swelling, corticosteroid injection, surgery,
and a variety of carpal tunnel prevention products. Long-term wheelchair users often
experience symptoms of carpal tunnel because of repetitive strain on the wrist, and the use of
electric wheelchairs is also opted for treatment. The commonly used wrist splint restricts
movement and help ease symptoms; however, patients experiencing symptoms of carpal
tunnel usually are subject to frequent use of their wrists demanded by their jobs or lifestyle
and thus often find wrist splints uncomfortable and restricting of daily activities. Other
nonsurgical prevention products have not been proven to work and in many cases have
shown to increase pain and numbness. Medication and drugs are ill-favored, expensive,
temporary and cumbersome to obtain and use to treat constant pain. Surgical treatment at
many times is also a very nonattractive solution as it is time-consuming, painful, and
expensive. Carpal tunnel patients in use of wheelchairs often find electric wheelchairs
expensive and unnecessary to treat their wrist problems.
There is a very wide variety of wrist braces of varying material and function. Most braces
today aim to make their product comfortable, washable, durable, and easy to remove while
holding the wrist firm and stable. Wrist braces are the most sought solution to carpal tunnel
and a large variety with prices ranging from $10 - $200+ are available in pharmacies, grocery
stores, hospitals, and online. A doctor would provide an inexpensive wrist splint upon
diagnosis.
Nonsteroidal anti-inflammatory drugs (NSAIDs) are used to relieve pain and inflammation.
Studies have not shown NSAIDs to be effective for carpal tunnel treatment but may reduce
symptoms. Some common medicines include aspirin, ibuprofen, and naproxen. These
11
products can be readily found in grocery stores or pharmacies with respective labels. Some
commercially popular drugs are listed:


Aspirin:
Ibuprofen:

Naproxen:
Tylenol Extra Strength 100 tablets - $15.99
Motrin IB (200mg) 100 caplets – $9.75
Advil (200mg) 150 caplets - $14.99
Aleve (220mg ) 100 caplets - $10.99
These drugs are commercially available and inexpensive, but are recommended to be used
with a doctor’s diagnosis and may cause side effects.
Surgery is sometimes recommended when other treatment has not helped, if a carpal tunnel
condition has continued for a long time, or if there is nerve damage or the risk of nerve
damage. This is determined by an electromyography or nerve conduction test. Surgery
involves cutting the ligament that forms the roof of the carpal tunnel to relieve the pressure
on the median nerve, which eases the symptoms of carpal tunnel syndrome.Surgery is usually
successful. In some cases it does not completely relieve the numbness and pain in the fingers
or hand. This may be the case if there has been permanent nerve damage caused by longstanding carpal tunnel syndrome or by other health problems such as diabetes. Surgery is
recommended for only severe cases of carpal tunnel because of recovery and expense
implicated difficulties. Cost of surgery and rehabilitation is in the range of $5,000 to $10,000
with some improvement achieved in over 70% of cases. Full restoration is achieved in less
than 60% of surgeries. Downtime and rehabilitation generally range from six weeks to three
months, but can take over a year, depending on how many lingering symptoms result and the
degree of scar tissue formation as this primary ligament in the hand heals back together. Scar
tissue formation during recovery from surgery is unpredictable and sometimes results in less
space in this narrow anatomical passage of the wrist after the carpal tunnel surgical
procedure, causing even more discomfort and numbness after surgery. This complication is
only reported in less than 15% of surgical procedures. It is common for people recovering
from the carpal tunnel surgical procedure to experience some permanent loss of grip strength,
a perduring loss of lifting strength in the wrist/forearm, a nagging loss of full range of motion
of the hand and wrist after surgery and lingering tenderness at the incision.
B1. CARPAL T UNNEL S YNDROME - T REATMENT O VERVIEW
The goal of treatment for carpal tunnel syndrome is to allow you to return to your normal
function and activities and to:




Address other health conditions if they are making your symptoms of carpal tunnel
syndrome worse.
Reduce any inflammation of tissues in the wrist that puts pressure on the median nerve.
Determine the causes of your carpal tunnel symptoms. You can then identify whether there are
activities for you to avoid or do differently and ways you can help prevent the condition.
Prevent nerve damage and loss of muscle strength in your fingers and hand.
12
Treatment for carpal tunnel syndrome is based on the seriousness of the condition, whether there
is any nerve damage, and whether other treatment has helped. Treatment options include
treatment without surgery (nonsurgical treatment) or with surgery.



If treated early, carpal tunnel symptoms usually go away with nonsurgical treatment.
If your symptoms are mild, with occasional tingling, numbness, weakness, or pain, 1 to 2 weeks
of home treatment are likely to relieve your symptoms.
If home treatment does not help, or if your symptoms are more severe (including the loss of
feeling in your fingers or hand, or the inability to perform simple hand movements such as
holding objects or pinching), have your doctor examine you and recommend treatment.
i) N ONSURGICAL T REATMENT
If your symptoms are not severe, expect your doctor to recommend nonsurgical treatment to
see whether symptoms improve. Nonsurgical treatment includes:





Evaluating any other medical problems that might contribute to carpal tunnel syndrome, and
changing your treatment for those problems if needed.
Changing or avoiding activities that may be causing symptoms, and taking frequent breaks
from repetitive tasks.
Wearing a wrist splint to keep your wrist straight, usually just at night. See a picture of
a wrist splint.
Using nonsteroidal anti-inflammatory drugs (NSAIDs) to relieve pain and reduce
inflammation. Although studies have not shown NSAIDs to be effective for carpal tunnel
syndrome, they may help relieve your symptoms.
Learning ways to protect your joints as you go through your daily activities.
In some cases, oral corticosteroids or corticosteroid injections into the carpal tunnel may
be considered if other methods to reduce inflammation do not work.
ii) S URGICAL TREATMENT
Surgery is sometimes recommended when other treatment has not helped, if a carpal
tunnel condition has continued for a long time, or if there is nerve damage or the risk of
nerve damage. Surgery involves cutting the ligament that forms the roof of the carpal
tunnel. This relieves the pressure on the median nerve, which eases or ends the symptoms
of carpal tunnel syndrome.
Surgery is usually successful. In some cases it does not completely relieve the numbness
and pain in the fingers or hand. This may be the case if there has been permanent nerve
damage caused by long-standing carpal tunnel syndrome or by other health problems
such as diabetes.
13
B2. S UMMARY
Nonsurgical treatment
 Changing or avoiding activities that may be causing symptoms, and taking frequent breaks from
repetitive tasks.
 Wearing a wrist splint to keep your wrist straight, usually just at night.
 Using nonsteroidal anti-inflammatory drugs (NSAIDs) to relieve pain and reduce inflammation.
Although studies have not shown NSAIDs to be effective for carpal tunnel syndrome, they may
help relieve your symptoms.
A wrist splint is a brace that looks like a fingerless glove and that stabilizes your wrist in a straight
and sometimes slightly bent-back position. Wearing a wrist splint minimizes pressure on the median
nerve and allows you a period of "relative rest" from movements that make carpal tunnel
syndrome worse.
** nonsurgical treatments usually treat only symptoms and not the source; also for non-severe cases
Surgical treatment
Surgery is sometimes recommended when other treatment has not helped, if a carpal tunnel
condition has continued for a long time, or if there is nerve damage or the risk of nerve
damage. Surgery involves cutting the ligament that forms the roof of the carpal tunnel. This
relieves the pressure on the median nerve, which eases or ends the symptoms of carpal tunnel
syndrome.
**Surgery is usually successful. In some cases it does not completely relieve the numbness and pain
in the fingers or hand. This may be the case if there has been permanent nerve damage caused by
long-standing carpal tunnel syndrome
A.
WRIST SPLINTS
Wrist splints can keep the wrist from bending. They are not as beneficial as surgery for
patients with moderate-to-severe CTS, but they appear to be helpful in specific patients,
such as those with mild-to-moderate nighttime symptoms of less than a year's duration. In
selected patients, up to 80% reported fewer symptoms, usually within days of wearing the
splint.
14
Typically the splint is worn at night or during sports. The splint is used for several weeks
or months, depending on the severity of the problem, and may be combined with hand
and finger exercises. Benefits may last even after the patient stops wearing the splint.
B. CORTICOSTEROIDS
Corticosteroid Injections
Corticosteroids (also called steroids) reduce inflammation. If restriction of activities and
the use of painkillers are unsuccessful, the doctor may inject a corticosteroid into the
carpal tunnel. Some experts recommend them for patients with CTS whose symptoms are
intermittent, and there is no evidence of a permanent injury. In CTS, steroid injections
(such as cortisone or prednisolone) shrink the swollen tissues and relieve pressure on the
nerve. Evidence strongly suggests that they offer short-term relief in a majority of CTS
patients. It should be noted that the pain may increase for a day or two after the injection,
and skin color may change.
Unfortunately, in many cases, steroid injections provide only temporary relief (from 1 - 6
months), particularly in patients with more severe symptoms. Generally a second
injection does not provide any added benefit. Another concern with use of these
injections in moderate or severe disease is that nerve damage may occur even while
symptoms are improving.
Corticosteroid injections are particularly useful for pregnant patients, as their symptoms
often go away within 6 - 12 months after pregnancy.
Most doctors limit steroid injections to about three per year, since they can cause
complications, such as weakened or ruptured tendons, nerve irritation, or more
widespread side effects.
Low-Dose Oral Corticosteroid
Oral corticosteroids are medicines taken by mouth. Short-term (1 - 2 weeks), low-dose
use of corticosteroids may provide long-term relief, but long-term use can cause serious
side effects, including high blood pressure and high blood sugar levels. People with
diabetes should be very cautious about oral corticosteroids.
C. ULTRASOUND
Ultrasound employs high-frequency sound waves directed toward the inflamed area. The
sound waves are converted into heat in the deep tissues of the hand, opening the blood
vessels and allowing oxygen to be delivered to the injured tissue. It is often performed
along with nerve and tendon exercises. It is not yet known how effective ultrasound
treatment is.
D. NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS)
15
Nonsteroidal anti-inflammatory drugs (NSAIDs), which include aspirin and ibuprofen
(Advil), are the most common pain relievers used for CTS. They block prostaglandins,
the substances that dilate blood vessels and cause inflammation and pain. Unfortunately,
as with most other medications used for carpal tunnel syndrome, there are few wellconducted studies to determine their role in CTS. To date, there is no evidence that they
offer any significant relief, and regular use can have serious side effects. Therefore, they
are generally not used for long-term treatment of carpal tunnel symptoms.
E. OTHER CONSERVATIVE APPROACHES
Ice and Warmth
Ice may provide benefit for acute pain. Some patients have reported that alternating warm
and cold soaks have been beneficial. (If hot applications relieve pain, most likely the
problem is not caused by CTS but by another condition producing similar symptoms.)
Low-Level Laser Therapy.
Some investigators are working with low-level laser therapy (LLLT), which generates
extremely pure light in a single wavelength. The procedure is painless. Two trials
comparing laser therapy to conservative treatment or a placebo laser treatment from no
real benefit for this therapy.
F. ALTERNATIVE THERAPIES
Many alternative therapies are offered to sufferers of carpal tunnel syndrome and other
repetitive stress disorders. Few, however, have any proven benefit. People should
carefully educate themselves about how alternative therapies may interact with other
medications or impact other medical conditions, and should check with their doctor
before trying any of them.
Vitamin B6
Vitamin B6 (pyridoxine) is often used for carpal tunnel syndrome. Studies have not
supported its benefits, however, either in oral or cream form. It should also be noted that
excessively high doses of vitamin B6 can be toxic and cause nerve damage.
Acupuncture
A very limited amount of evidence shows that acupuncture may be useful as a
supplement to standard treatment.
Chiropractic Therapies
16
Chiropractic techniques have been useful for some people whose condition is produced
by pinched nerves. There is little evidence, however, to support its use for carpal tunnel
syndrome.
Magnets
Magnets are a popular but unproven therapy for pain relief.
Botulinum toxin type A
Intracarpal injections of botulinum toxin type A (Botox) has not been well studied.
G. ELECTRIC WHEELCHAIRS
Electric wheelchairs are easy to use and would restrict the necessary wrist movement
needed to move on a normal wheelchair and prevent/treat carpal tunnel.There are a wide
variety of electric wheelchairs available, however even the most inexpensive wheelchairs
are in the price range of $1000+. For our specific consumer target, long-term wheelchair
users with high risk of developing carpal tunnel, the electric wheelchair is a solution
closest to our goals, but we are also trying to make our product inexpensive and readily
available.
The wrist splint and electric wheelchair tackle similar goals to restrict wrist movement to
prevent carpal tunnel. More specifically relevant products include the Slayer Wheel and
the Smart Wheel.
H. OTHER INNOVATIONS
SmartWheel
Wheelchair prescription is complex with thousands of choices and options. Theoretically, a
higher quality or innovative wheelchair that is appropriately matched to the user and their unique
needs will increase participation. It is well accepted that there is an alarmingly high incidence of
carpal tunnel syndrome, and rotator cuff injuries among manual wheelchair users.
Since the initial conceptualization, the SMARTWheel was intended to better understand the
physiological and physical effects of wheelchair propulsion on the body. Initially, little was
known about wheelchair propulsion and the SMARTWheel transformed the nascent field of
wheelchair propulsion biomechanics.
17
Although still an important area of clinical research, the SMARTWheel has been critical to the
study of the relationship between the type of wheelchair, set-up, activity, technique, anatomy, and
physiology and repetitive strain injury. There has been growing evidence that the wheelchair-user
interaction explains a substantial portion of the risk of developing a degenerative injury and on
community participation. A noteworthy contribution of this work was the release of the clinical
practice guideline, entitled, Preservation of Upper Limb Function Following Spinal Cord Injury
in 2005.
The SMARTWheel has been used by other scientists in areas that were not originally envisioned to
be applications. It has been used to support the design of tools for developing a trail mapping
rating and description system. It has also supported the design of accessible pedestrian walkways
standards, accessible playground surfaces, and to evaluate carpets for wheelchair accessibility. It
is likely that there are more new areas of exploration to emerge. This article describes the
evolution of the SMARTWheel as new technologies became available and its applications in the
field of wheelchair biomechanics and clinical service delivery.
SmartWheel Homepage
18
RODEM
19
A new competition in the fast-moving field of slow-moving mobility -- at least if this
new RODEM prototype developed by a group of research partners at Japan's Veda Center
(including Tmsuk) actually hits the market.
Apparently designed to be used as both a replacement for a wheelchair and as a general
purpose "universal vehicle," the four-wheeled RODEM allows folks to simply lean
forward slightly without the need for any back support, which the group says will let
people get in and out of the vehicle more easily, and with less assistance from caregivers. Of course, no sci-fi inspired vehicle would be complete without a few bells and
whistles, and it looks like the RODEM is more than capable in that department, with it
packing some built-in GPS, automatic obstacle evasion control, automatic slope
correction, an "autonomous navigation function," voice recognition, and some sort of
vital monitoring system (all of which may or may not actually be included in the
prototype).
SlayerWheel
Over 70% of manual wheelchair users will suffer from shoulder pain or carpal tunnel syndrome
in their lifetime.
Choosing a lightweight wheelchair wheel and ergonomic handrim can significantly reduce this
risk and lead to a better quality of life for the user and their carers.
Over the last 30 years there have been significant advances in wheelchair wheel and wheelchair
hand rim design research that indicates that there are significant pain relieving advantages that
can be enjoyed by choosing lightweight wheelchair wheels and ergonomic wheelchair hand rims.
In addition incorporating rear wheel and castor suspension not only makes the wheelchair easier
to propel, but makes the ride smoother and reduces the probability of secondary neck pain, lowback pain and abdominal discomfort.
20
C. Patents
Wheelchair Drive Mechanism
Patent number: 6,893,035
Title: Wheelchair drive mechanism
21
22
23
Manually Propelled Wheelchair Device
Patent number: 5,941,547
Title: Manually propelled wheelchair device
24
25
Wheelchair Drive System with Level Propulsuion
Patent number: 7,837,210
Title: Wheelchair drive system with lever propulsion and a hub-contained transmission
26
27
Wheelchair Drive Mechanism 2
Patent number: 7,261,309
Title: Wheelchair drive mechanism
28
29
30
Conversion Kit for Manual Wheelchairs
Patent number: 6,371,502
Title: Universal conversion kit for human powered wheelchairs
31
32
Propulsion Aid
Patent Number: 6,048,292
Title: Combination arm exercise apparatus and propulsion aid for a wheelchair
33
Wheelchair-Attachable Power Unit
Patent number: 5,135,063
Title: Power unit for driving manually-operated wheelchair
34
35
Pedal Propulsion Wheelchair
Patent Number: 4,560,181
Title: Wheelchair operated by hand pedalled reciprocating motion
36
37
38
D. Interviews
Interview with Daliya
Female student, 11-year manual wheelchair user







Maneuvering is a 4 in comfort, 3 uphill
Wrist pain while maneuvering
Uphills are very strenuating and difficult to go up
During downhill, hands stay on the pushrim for better control, but much strain
Can go for like 30/40 minutes before wrist pain
Uses football receiver gloves
Problems?
o front wheel dirt collecting, snow wheels, slippery wheels, wet wheelchair,
umbrella, snow, weight, balance
 Why not use an electrical wheelchair?
o Mechanical wheelchairs are foldable, smaller, and you can go faster
Electrical wheelchairs are better for uphill, one hand is free to hold beverages, and battery life is
iffy though
Ace bandage wrap helps, bubble wrap thing helps, heating pad when not in use helps
Willing to pay 500-1000 more
Interview with Chris Baswell
Contact: [email protected]
Gender: Male
Age: in 50s
-manual wheelchair user
-says he experiences no pain in the wrist; range of wrist movement during maneuvering is very
minimal
-says the problem is more with fingers than wrist; problem with gripping the wheel
-says he has developed arthritis in his finger joints due to maneuvering wheelchair; red arrows in
the following diagram show locations of his arthritis:
39
-says fatigue in his muscles(biceps and triceps) is the main reason he has to stop occasionally
-reasons for not using power wheelchair:
*lack of exercise; muscle atrophy -> says that most doctors won’t prescribe the patient to a
power wheelchair unless it is absolutely necessary
*mobility: his mechanical wheelchair is very light and the wheels come off so that it can easily
fit in the trunk of a car when he needs to travel by car. However, power wheel chairs are a lot
heavier and harder to transport.
My idea after conducting the interview (Han) : Combination of mechanical and electrical input
-model that still needs mechanical input but assists with electrical power
-model that can switch between mechanical propulsion and electrical propulsion
*model that harnesses energy from the mechanical input of the user into electrical, and allows
the user to propel the wheelchair with the built up or created electrical energy when the user gets
tired or is going up a slope.
Interview with Brendan
Email: [email protected]
Gender: Male
Age: N/A
-has been using a manual wheelchair for 15 years
-lives around Columbia; 106th and Broadway
-wants to be active in our project
-gave an 8 out of 10 on the comfort level for maneuvering the wheelchair; his reason for the
score was that he has actually never thought of another way of maneuvering the wheelchair since
he has been using the wheelchair for 15 years.
-when asked what he thinks could be improved about the manual wheelchair, he said it was a
difficult question for him to answer because it would be like asking myself what could be
improved about my shoes.
-said upper body muscle fatigue is what usually requires him to stop occasionally
-said he preferred the manual wheelchair over the electric wheelchair due to better mobility
-said he has never seen anyone use a lever type mechanism for propelling the wheelchair, nor
any other interface that differs from the standard.
40
III
Design Functional Requirements and Constraints
41
i.
Functional Requirements

Allow user to effectively steer the wheelchair

Allow user to effectively operate the wheelchair with the device

Reduce the incidence of upper body wheelchair related injuries

Must reduce fatigue experienced by the user

Must retain the original motion
Wheelchair users are comfortable with the original motion and should have the option to fall back
on it when desired

Reduce the likelihood/effects of carpal tunnel syndrome
In the study done by Sie et al., 66% of wheelchair users examined had CTS symptoms (Archives
of Physical Medicine and Rehabilitation, 1992).

Reduce strain on the user’s wrist
Fingertip loading, the way users ambulate the wheelchair, increasespressure in the carpal tunnel
(Pinkham, Occupational Health and Safety, 1988).

Coast
The wheelchair must be able to go forward without continuous propulsion to prevent fatigue,
much like standard wheelchairs or bikes operate
ii. Specifications

Less than 15° of flexion and extension, less than 5° radial deviation, less than 10° ulnar deviation
iii. Constraints
1

Discrete
A chief concern among surveyed wheelchair users is that any wheelchair that deviates from the
standard motion will attract a lot of attention. They feel like they get enough attention as it is with
wheelchairs, so discretion is key to avoid feelings of self-consciousness and discomfort.

Portable

Light-weight

Not biomechanically taxing
Young male paraplegics have been observed to expend 9.9 calories per minute when pushing a
hard pace of four to five miles per hour (Trotter, 1985).1
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2327379/pdf/canfamphys00210-0053.pdf
42
2
3

Affordable
Low levels of educational attainment and low employment rates combine to create a bleak
economic picture for many wheelchair users, one-fifth (19.1 percent) of whom live in poverty.
Wheelchair use decreases by nearly a factor of 5 between persons with family income less than
$10,000 (1.3 percent of whom are wheelchair users) and those with family income greater than
$35,000 (0.3 percent) (Kaye et. Al, 2002).2

Easy to use
For patients with quadriplegia who have reduced hand dexterity,the wheelchair must allow the
user to use only one hand to operate it. Also, wheelchair users tend to get injured from
transferring from the wheelchair to another surface, propelling a wheelchair, and unweighting the
sacrum with improper form.3

Adjustable
Wheelchair users come in a variety of body types, and our design must be able to accommodate
them

Bidirectional
The device should provide propulsion in both forward and backward directions, to make use of all
of the muscle groups in the upper body to reduce overall fatigue
http://dsc.ucsf.edu/publication.php
http://www.ncpad.org/
43
IV
Preliminary Designs
44
i.
Upper Body Pull
ii. 45 Degree Slide
45
iii. Elliptical
iv. Rim Slide
v.
Tank
46
vi. Hand Bike
vii. Ski Bike
viii. Grip
47
ix. Backward Wheel
x.
Wrist Brace
xi. Skateboard
48
VI
Design Matrix
49
Concept Selection Matrix
CRITERIA
minimize wrist
strain
sustainable motion
Max Power
stable arm position
flat land balance
slope balance
0
Pushrim
(standard)
WEIGHT Value
100
500
85
30
85
70
45
totals:
0
Crew
0
Ski
0
Elliptical
U. Arm
Push
Value
5
700
Value
7 800
Value
8 1000 10 1000
425
150
425
350
225
5
5
5
5
5
5
9
8
5
3
4
6
7
6
3
2075
30
425
270
680
350
135
340
180
595
420
135
595 7
120 4
850 10
560 8
180 4
595
90
510
630
90
2560 37 2470 34 3305 43 2915
45 degree
Vert Push
10
800
8
700
7
7
3
6
9
2
510
150
765
560
450
6
5
9
8
10
425
270
510
630
225
5
9
6
9
5
37 3235
46 2760 41
Note: This decision matrix was designed to select the best motion for the manual wheelchair
user to use to propel the wheelchair. Once the type of motion was selected, the mechanism for
the motion could then be specified.
50
VI
Proof of Concept Plan
51
i.
Measuring the Range of Wrist Movement
Carpal tunnel syndrome(CTS) is one of the notablediseases that manual wheelchair users
develop; 54% of users at 1-10 years of chair use develop this disease and 90% at 20-30 years.4
With our design we intend to reduce this high incidence of CTS within the manual wheelchair
population.
Carpel tunnel syndrome has been proven to be correlated to an elevation in pressure in
the carpal tunnel, specifically an impingement of the median nerve that runs through the carpal
tunnel in the wrist. Gellman et al. have shown that an elevation of pressure is directly
proportional to joint angle. Using exercise machines that closely mimic arm motions used in our
preliminary designs, the range of radial and ulnar deviation and of flexion and extension of the
wrist will be measured then compared among the different arm motions as well as compared to
the motion of operating a manual wheelchair. In this way, the magnitude of the wrist angle
ranges will be used as a proxy for intensity of median nerve impingement and consequentlyrisk
of carpal tunnel syndrome.
ii. Measuring EMG Signals from Various Upper
Body Muscle Groups at Different Angles of
Motion
The next steps of our proof of concept will involve going to the fitness center with our EMG detector,
electrodes, and oscilloscope, and measuring EMG signals from various upper body muscle groups at different
angles of motion. The motion used for propulsion will be simulated by the use of a cable machine(Figure
1), and the experimenter will be seated on a chair to mimic the conditions of a wheelchair user. Refer to
Figure 2 for a picture of the setup used for the experiment. Through the following procedures, we hope to
determine the most ideal angle at which the user of our device would have to input the necessary force for
propulsion(refer to Figure 3), and the most ideal angle at which the normal vector to the plane of the palm
of the hand(refer to Figure 4) would be positioned when applying the necessary force for propulsion; the
most ideal angle will be determined by the most even muscle activation between the various muscle
groups with consideration of relatively how much stress each muscle can handle. The procedure is laid
out below:
1) By adjusting the height of the handle on the cable machine, the angle of the cable with respect to
the vertical can be varied(Figure 3). Start with this angle set at 90°.
2) When grabbing the handle of the cable machine, make sure that the normal vector to the plane of
the palm(Figure 4) is facing up at 0° with respect to the vertical.
3) Place two electrodes on the biceps and one electrode on the elbow to set as ground. Connect the
output of the EMG detector to an oscilloscope, and set the scope at the appropriate settings to
measure the EMG voltage waves.
4) Carry out the push/pull motion on the cable machine at least 10 times and record the amplitudes
of the voltage wave for each cycle.
4
http://www.ncpad.org/exercise/fact_sheet.php?sheet=109&view=all
52
5) Repeat steps 3-4 for the two electrodes placed on the triceps, front deltoids, back deltoids,
pectoralis major, and trapezius.
6) By adjusting the height of the handle on the cable machine, set the angle of the cable with respect
to the vertical at 65° and repeat steps 2-5. Repeat steps 2-5 for angles of 45°, and 25°
7) When grabbing the handle of the cable machine, make sure that the normal vector to the plane of
the palm is directed at 20° with respect to the vertical, and repeat steps 1, 3-6. Vary the angles of
this normal vector in intervals of 20°, until the palm of the hand is facing down at 180° with
respect to the vertical.
8) Make tables and graphs from the data and analyze the muscle activation of the various muscles
groups for the different variables considered.
Figure 1. Cable Machine
Figure 3. Angle of the cable
with respect to the vertical
Figure 2. Picture of set-up used for experiment
Figure 4. Angle of normal vector to the
plane of the palm with respect to the
vertical
53
VII
Proof of Concept Outcome
54
i.
Measuring the Range of Wrist Movement
Wrist joint angles are directly proportional to the elevation of pressure in the carpal tunnel.
Repeated and prolonged exposure to large pressures (>30 mm Hg) within the tunnel and thereby
large joint angles of the wrist induces carpal tunnel syndrome. In order to determine what arm
motions will reduce the severity of carpal tunnel syndrome within the wheelchair population, an
experiment was carried out to determine the range of wrist angles a person experiences while
operating various exercise machines that mimic the arm motions proposed in preliminary designs
of our product.
On the left arm of a 21 year-old able-bodied woman, black dots were drawnon the right
side andthe middle of the top of the wrist, the right side and the middle of the top of the forearm,
just below the third knuckle of the middle finger, and finally on the right side of the handby the
third knuckle of the pointer finger (6 dots total), see Figure 1.The exercise machines used in this
experiment were a Precor Chest Press, a PrecorLongpull Modular Station, and a Concept2
Indoor Rower, see Figure 2. A manual wheelchair was used as the control.Prior to using each
machine, pictures of the front and side views of the left arm in a neutral position were taken.
While the subject operated each machine, pictures of the front and side views of the left arm
were taken intermittently. The pictures were then analyzed usingImageJ;using the three dots seen
in each view, the angle tool was used to determine the angle ofradial deviation(RD), ulnar
deviation (UD), flexion(Flex) and extension(Ext), see Figure 3. For each measurement, three
different individuals measured the angle. These three trials were then averaged. With reference
to the neutral position of the wrist, the range of the angles experienced by the wristwascalculated
for each machine as well as the maximum range of the wrist itself, see Table 1.
Employing almost the full range of motion of the wrist, the machine with the largest
range was the manual wheelchair, underscoring a user’s high risk of developing carpal tunnel.
For the Longpull Modular Station, the maximum radial deviation and ulnar deviation is smaller
than that for the wheelchair; however, the amount of flexion and extension is significantly higher
compared to the ChestPress and the Longpull Modular Station. The main difference between the
motion when using the Indoor Rower and the Longpull Modular Station is that when usingthe
Indoor Rower, a user’s elbows stay away from the torso; this results in decreased wrist flexion.
The Chest Press has the lowest range of wrist joint angles. The main difference between the
motion when using the Indoor Rower and the Chest Press is that when using the Chest Press, a
user’s palms are facing each other rather than be parallel to the ground and that a user’s elbows
remain close to the torso. These results support our design, to have the motion of the arm include
keeping a user’s elbows close to their torso and having their palms face each other.
Figure 1. Sample Images of Marker Placement on Subject’s Hand
55
Figure 2. Exercise Machines Used In This Experiment5678
Figure 3.Image Representation of Radial Deviation, Ulnar Deviation, Wrist Flexion and
Extension9
5
http://www.precor.com/products/en/commercial/strength/experience-strength-s-line/upper-body/chest-press-c001es
http://www.precor.com/products/en/commercial/strength/icarian-strength/multi-station-and-modulars/longpullmodular-station
7
http://www.concept2.com/us/default.asp
8
http://www.lighthousedme.com/products/wheelchairs.html
9
http://tt.tennis-warehouse.com/showthread.php?t=337194&page=3
6
56
Neutral
RD
UD
(degrees) (degrees) (degrees)
Maximum Range
of Wrist
Wheelchair
avg.
Chest Press
avg.
Indoor Rower
avg.
Longpull
Modular Station
avg.
Neutral
Ext
(degrees) (degrees)
Flex
(degrees)
75.42
60.35
30.25
-20.77
177.95
178.86
177.95
178.25
150.03
149.12
149.4
149.52
185.94
184.36
185.22
185.17
182.34
181.22
181.93
181.83
153.35
154.73
153.32
153.80
191.51
191.43
192.48
191.81
0
28.74
6.92
0
28.03
9.98
178.22
177.98
178.13
178.11
174.32
173.5
174.06
173.96
184.31
183.6
183.94
183.95
181.37
182.16
181.56
181.70
172.65
174.59
173.66
173.63
180.36
179.83
180.77
180.32
0
4.15
5.84
0
8.06
1.38
176.39
177.21
177.93
177.18
173.55
173.2
173.34
173.36
183.43
182.7
182.95
183.03
180.95
181.4
181.35
181.23
168.54
167.49
168.7922
168.27
181.48
182.58
182.4
182.15
0
3.81
5.85
0
12.96
0.92
178.57
172.58
182.75
181.82
170.67
198.49
177.95
177.11
177.88
171.74
172.61
172.31
183.49
183.03
183.09
181.49
180.02
181.11
169.65
171.33
170.55
199.4
198.15
198.68
0
5.57
5.21
0
10.56
17.57
Table 1. Summary of Data and Calculations
57
ii. Measuring EMG Signals from Various Upper
Body Muscle Groups at Different Angles of
Motion
The graphs below display the results of the experiment. By measuring the degree of
muscle activation of each muscle at the different angles of motion, relative stress distributions to
the various muscles at each angle can be inferred. Generally, it can be seen that the degree of
activation of the biceps stays fairly constant throughout the different angles, and that the stress
from the back and front deltoids and trapezius are gradually transferred to the triceps and
pectoralis major as the angle is increased starting from 0 degrees. 65 degrees was eliminated as
the most ideal angle from the start because it distributed most of the stress to only the triceps and
pectoralis major. Upon further observation, it can be seen that the motions at 0 and 25 degrees
have the most even muscle activations of the different muscles used. It can be concluded that 25
degrees below the horizontal is the most ideal angle of motion because the pectoralis can handle
greater stress than the front deltoids. The next steps will involve testing more angles between 0
and 25 degrees, using a pull motion instead of a push motion, and testing angle at which the
normal vector to the plane of the palm of the hand would be positioned when applying the
necessary force for propulsion.
Figure 4. Results of the 2nd proof of concept experiment