Function:



The Product Design Specification (PDS)

ALS Neck Brace

Team Members:

Margaret Bennewitz

Laura Hansen

David McGurl

Kristin Wescoe

Revision Date: April 1, 2007

Function: Patients with amyotrophic lateral sclerosis (ALS) suffer from weak neck flexor and extensor muscles that cause their head to drop. Even though ALS patients cannot hold up their head, they often retain the ability to move it from side to side. This device will serve as a lightweight neck brace that both supports the neck and allows lateral rotation of the head, so that ALS patients can regain some use of their head during everyday activities. It will replace the currently used, traditional neck brace, which was designed to completely immobilize and stabilize the head during recovery from neck injuries to the vertebrae and spinal cord. This brace will also include a redesigned, lower friction track that will require a minimal force to move the chin cup.

Client Requirements:

• The brace must be biocompatible for all users; its materials need to be hypoallergenic and breathable in order to prevent skin rashes, irritation, or chafing.

• Must be able to be worn comfortably for up to 18 hours, have a total weight of less than 1 lb, and not hinder the patient from performing his/her daily activities.

• The weight of the patient’s head must be evenly distributed on a pad resting on the patient’s chest and shoulders, and must be small enough in magnitude to avoid pain and discomfort.

• The brace must allow total lateral rotation of 67 degrees, and it must maintain its ability to rotate when the full weight of the patient’s head (5.23 kg for the average male) is placed on the chin rest.

• The brace must be adjustable to fit the middle 95% of the male and female population.

• The brace should facilitate seeing, speaking, and walking by holding the head in an upright position and allowing lateral movement.

• To further enhance comfort while wearing the brace, the new design should be cooler and less bulky than traditional neck braces.

• Since only one brace unit will be purchased, the components should be washable or easily replaceable.

• To ensure that the patient will not have to buy the brace, the design should be in agreement with insurance requirements.

Design Requirements

1. Physical and Operational Characteristics

a. Performance Requirements

The device should be able to be worn for up to 18 hours a day, during most activities besides sleep. It must fully support the mass of the 95th percentile male’s head of 5.23 kg and allow for a minimum of 50 percent of the normal range of head rotation, which is 67 degrees in total rotation. It is important that the track have a low frictional coefficient, so that the forces required to move the chin rest do not exceed the strength of the neck muscles controlling lateral rotation. The performance of the brace must remain constant for all applications; its material strength cannot weaken with use or deform under stress.

b. Safety

The daily use of this neck brace should not cause any pain or discomfort to the person wearing the brace. This means that the chin rest must be easy to move along the track when the head is resting on it, and that the weight of the patient’s head must be evenly distributed along a pad on the patient’s chest and shoulders, at a low enough magnitude. In addition, the components of the brace should not be sharp, as to prevent injury to the patient. The device is not intended for use while sleeping, as it may move or break, which could cause injury to the patient such as skin puncture or suffocation. Furthermore, patients should not wear the brace when bathing, as excessive exposure to water or other chemicals could damage the brace and affect its performance. If the brace is worn while eating, the patient should be cautious, as the chin rest may inhibit jaw movements affecting chewing and swallowing. This device should comfortably fit a variety of patient sizes and not rub against the patient’s skin while in use. To prevent unnecessary injury, the patient must comply with these general safety guidelines.

c. Accuracy and Reliability

The neck brace should allow a total lateral rotation of 67 degrees and be accurate to + 1 degree. It must maintain this degree of motion for each use, with the same force required to cause motion along the track each time. The neck brace must also comfortably support the mass of the 95th percentile male’s head, 5.23 kg, if it is to be used by 95 percent of the population. Therefore, the brace must continue to fully support this mass without failure over the duration of use.

d. Life in Service

The neck brace should be fully functional and able to be worn comfortably for up to 18 hours per day, every day, for use during most daily activities other than sleeping and bathing. The mean survival time for persons with ALS in the US is about 3 to 5 years. Since muscle weakness is the most common initial symptom in about 60 percent of patients, the frame of the brace should last about 5 years, with the soft components replaced every 6 months. Ideally, one brace unit will be enough for a single patient, with the ability to easily clean or replace any part.

e. Shelf Life

The shelf life of the brace will depend on the individual shelf life of each component, which is determined by the material composition. Ideally, the parts should be able to be stored for 5 years. The components should be stored at room temperature in a dry environment.

f. Operating Environment

This device will be used at home everyday by a single patient and therefore must be easy to put on and take off individually. It must tolerate room temperature, pressure, humidity, and any dust deposited from inactivity. The materials of the brace should withstand minimal exposure to moisture by not dissolving or corroding upon water contact. The track on the brace should be well lubricated to prevent unnecessary, noisy creaking when the neck is rotated.

I. Temperature Range: Room temperature (20-25oC) for parts not in direct contact with the body; 37oC for parts resting against the body.

II. Dust or Dirt: Frame will be easily cleaned with a damp cloth; padding will be washable or replaceable.

III. User: Should be easy to use for average person and be non-collapsible.

g. Ergonomics

Ideally, the neck brace should weigh less than 1 lb, to minimize the force pushing down on the patient and therefore increase patient comfort. Putting on, removing, and transporting the brace should be simple, easy, and not require assistance. The device should not worsen the health of the patient; therefore, it should not cause further neck pain, rashes, irritation, or sufficient pressure on the chest or chin. To prevent rubbing, it should fit snugly around the patient’s girth. The brace should be stable and able to stand alone, for times when it is not in use, to prevent damage.

h. Size

The brace should fit the middle 95 percent of the adult population and must therefore be adjustable to fit the anthropometrical data of this target population. Since it will be used by a variety of male and female patients, the brace should have some degree of fine adjustment. For example, the Dacron straps can provide some girth adjustments, while the malleable shoulder rests ensure a snug fit to the patient. It must also be a manageable size and shape for the patient to maintain mobility and be able to perform most daily tasks.

i. Weight

The neck brace should weigh less than 1 lb so it can be worn for long periods and not impede normal activity. The brace needs to be light enough to rest on a patient’s shoulders without causing pain or injury.

j. Materials

The components of the neck brace should be made of biocompatible, hypoallergenic materials that allow the skin to breathe and wick moisture away from the skin, keeping it cool and dry. This is important in preventing skin rashes and irritation. The type of material will differ for the function of the component. For load bearing parts, the materials should be durable and strong, but for the areas in direct contact with the patient’s skin, such as the chin rest, the materials should be softer, form fitting, and breathable to enhance comfort. None of the materials should react with water.

Frame – aluminum round bar 1/8”

Track – WaterShed 11120

Chin cup – 3/16 copolymer and 3/16 4-E Volara foam

Sternum pad – aluminum coated with smoked elk and heavy-duty Dacron poly-felt

Straps - 1" Dacron strap webbing

k. Aesthetics, Appearance, and Finish

The neck brace should be free of any sharp edges, rough surfaces, or obtrusive corners, to prevent injury to the patient or damage to the neck brace. Color should be neutral so that the brace looks more natural and does not draw unnecessary and unwanted attention to the patient. To minimize bulkiness, the brace should have an open frame design. The finish on the frame should be biocompatible and easily cleaned.

2. Production Characteristics

a. Quantity

According to the National Institute for Neurological Disease, about 30,000 people are said to be affected with ALS at any given time. Although it is geared towards ALS patients, any patients with weak neck extensor muscles, who still possess neck rotational mobility, can use the device. Therefore, the ultimate number of units should satisfy this target population.

b. Target Production Cost

The cost must be within the acceptable, standard, covered range for most insurance companies. If an insurance company for any reason does not cover the device, it must be relatively inexpensive, so that ALS patients can easily afford to purchase the brace without further subsidization. A projected cost of the brace is approximately $300 including both material and labor.

3. Miscellaneous

a. Standards and Specifications

The brace will meet the terms of both the US and European government safety standards. Human subjects testing approval may be required, as well as a safety evaluation and prototype approval by a qualified clinician and orthotist.

b. Patient-Related Concerns

The brace will be made for one person only, so it will not be necessary to sterilize it; however, it might be desirable to clean the brace occasionally. Therefore, all components should be washable or at least replaceable and inexpensive. The brace must permit lateral neck rotation, with a minimum applied force. It must be lightweight and have a maximum distribution area of force and pressure on the neck and chest, to avoid pain and injury. In testing our prototype, all of the surveys will be anonymous, to eliminate the concerns with patient confidentiality. 

c. Competition

No known neck brace exists that properly supports the neck and head, while still allowing sufficient lateral rotation. Current neck braces in production are all based around immobilizing the head and neck, to facilitate recovery from trauma to the neck and spinal cord. Since many ALS patients retain the ability to laterally move their head, these immobilizing braces do not satisfy their customer needs.

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download