Design Specs
 Senior Design Spring 2004

Stevens Institute of Technology

Mechanical and Biomedical Engineering Departments

 

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Development of Specifications

        Detailed specifications for the device were determined based on parameters of the distraction osteogenesis procedure, as well as patient and surgeon needs.  The importance of each need was developed using a needs vs. metrics matrix, which is shown as follows:

 

 

Needs Vs. Metric Matrix

 Metric

Device has simple design and easy surgical aspects

Device is compact

Device includes fixture for easy adjustments; easy operability

The device has ability to move the osteotomy in two dimensions

One complete turn on protruding knob is 1mm

Device is composed of biocompatible material

such as titanium or surgical grade stainless steel

Device has a favorable industrial design.

No.

 

Need

Imp

 

 

 

 

 

 

 

1

The device is easy for the surgeon to implant and remove

5

x

 

 

 

 

 

 

2

The device is comfortable for the patient in situ

5

 

x

 

 

 

 

 

3

The device is easy for the patient to make daily adjustments

5

 

 

x

 

 

 

 

4

The device can distract in the horizontal and vertical directions

5

 

 

 

x

 

 

 

5

The device is capable of distracting in the prescribed amount

5

 

 

 

 

x

 

 

6

The device is composed of biocompatible material

5

 

 

 

 

 

x

 

7

The device is aesthetically pleasing

3

 

 

 

 

 

 

x

Target Specifications           

        Certain specifications used for evaluation include material compatibility, device operability and size of device.  Using the needs and metrics from the chart above, target specifications were identified in order to set the best possible parameters for the design of the intra-oral distraction device.  The target specification table can be seen below:

Metric No.

Need Nos.

Metric

Imp.

Units

Marginal Value

Ideal Value

1

1

Simple design and easy surgical aspects

5

-

 

 

2a

2

Device is compact: minimal length

5

mm

<25

<20

2b

2

Device is compact: lightweight

5

g

<100

<50

2b

2

Device is compact: minimal thickness

5

mm

<4

<2

3a

3

Easy operability: Time for installation

4

min

<60

<45

3b

3

Easy operability: torque

4

Nm (ftlb)

1Nm (.7ftlb)

<.5Nm (.36 ftlb)

3b

3

Easy operability: Time for removal

4

Min

<45

<30

4

4

Device can move in two directions: Maximum angle

5

Deg.

5<x<90

5<x<90

5a

5

Pitch of threaded rod allows for distraction of 1mm for each turn or half turn

5

Pitch

1mm or .5mm

.5mm

5b

5

Distraction gap accounted for by device

5

mm

<2mm

<1mm

6

6

Uses biocompatible material

5

Material

SS or Ti

SS or Ti

7

7

Device has favorable industrial design

3

-

 

 

8

-

Multi-tooth/Single tooth capability: Transport Plate length

4

mm

2<x<6

1.5<x<7

9

8

Safety of Device

5

Safety Factor

1<3

2


 

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Last modified: 05/02/04