Week 9 Flashcards
What are the aspects of the fair-lead cable?
Split at the elbow
Allows it to control multiple functions
Where is the proximal portion of the split housing attached?
Posterior humeral section
How is the proximal portion of the split housing attached?
Baseplate and retainer
What is the proximal distal and medial lateral position of the proximal portion of the split housing determined by?
A straight line from cross-point TD with the elbow extended.
Where is the distal housing portion attached?
Forearm
How is the distal housing attached?
Via “Elbow Flexion Attachement”
Where does the cable route originate?
At the control attachment strap of harness.
Where does the cable route pass through proximally?
proximal housing
Where is the cable exposed on the cable route?
Anterior to mechanical elbow joint axis
Where does the cable route pass through distally?
Distal portion of split housing of the forearm and through the elbow flexion attachement
Where does the cable route terminate?
At the TD
What occurs because the housing is split?
Tension on control cable
What happens when the elbow is unlocked?
Flexes elbow
What happens when the elbow is locked?
Opens terminal device
What is determined by the Elbow Flexion Attachment point?
Ease of elbow flexion operation
What occurs when the Elbow Flexion Attachment is close to the mechanical elbow axis?
Less cable excursion required
More force required
What occurs when the Elbow Flexion Attachment is far from the mechanical elbow axis?
More cable excursion required
Less force required
What is the general starting position of the Elbow Flexion Attachment?
1 1/4 in distal to elbow axis
1 in anterior to elbow axis
Determined for each patient
For harnessing, what is the excursion required for transradials?
5cm (2in)
For harnessing, what is the excursion required for transhumerals?
11.3 cm (4 1/2 in)
What are the six different parts of the Figure 8 harness?
Axilla loop Anterior support strap Lateral support strap Control strap Elbow lock control strap Cross point
What is the position of the cross point?
just to non-amputated side
Distal to C7
Where does the Axilla loop attach?
to the cross point
What is the main objective of the Axilla loop?
Anchor for other harness components
Why do some straps attach to the Axilla Loop?
For control
Suspension
What is not used for transhumerals at the cross point?
A northwestern ring because it provides too much freedom.
What is the anterior support strap also known as?
Elastic suspension strap
Where does the anterior support strap originate?
At the cross point
Where does the anterior support strap cross through?
The delto-pectoral groove
Where does the anterior support strap attach?
The distal anterior humeral section
Where is the anterior support strap elastic?
Distal 2/3
What is the purpose of the anterior support strap?
Helps suspend prosthesis
Helps prevent external rotation
Helps “cock” the elbow lock
Where does the elbow lock strap originate?
On the upper non-elastic portion of the anterior support strap
Where does the distal end of the elbow lock strap attache?
To the elbow lock control cable
How much excursion is required of the elbow lock strap?
1.3 cm
Where does the lateral support strap originate?
Just posterior to the highest point of the axilla strap
Where is the lateral support strap stitched to?
The anterior support strap
Where does the lateral support strap attach?
Close to proximal socket trim line
What does the lateral support strap do?
Suspends
Helps limit external rotation when control cable engaged
Where does the control cable originate?
The cross point
Where does the control cable run?
Obliquely downward across the back, mid-scapula
What occurs when the control cable is too high?
Not enough cable excusion to operate elbow and TD
What occurs when the control cable is too low?
Requires too much force to operate
Where does the cross-back strap originate?
Axilla loop close to posterior axillary fold
Where does the cross-back strap pass?
Horizontally across the back
Where does the cross-back strap terminate?
at the distal end of the control strap just proximal to hanger adjustable buckle
What is the purpose of the cross-back strap?
Helps reduce the vertically directed force of the Axillary loop
Helps prevent superior migration of cross point
Helps keep the control cable in the mid-scapula position
What is the challenge of the shoulder saddle harness?
Requires need for excursion in transhumeral
When can the shoulder saddle harness be used?
When needing to distribute the forces caused by unusually heavy use.
What are the differences for bilateral transhumeral harnessing?
Figure 8 harness has no axillary loop
has over the shoulder strap
What is essential for bilateral transhumeral harnessing?
cross back strap
Where is the shoulder strap stitched for bilateral tranhumeral harnessing?
To control strap, lateral strap and Anterior support strap
What are the transhumeral control motions?
Gleno-humeral flexion
Bi-scapular abduction
What are the elbow lock control motions of tranhumerals?
Slight glenohumeral extension
Slight gleno-humeral abduction
Slight shoulder depression
What are the control motions for a shoulder disarticulation?
Bi-scapular abduction
How is shoulder disarticulation best harnessed?
By chest strap
Where does the chest strap originate for shoulder disarticulations?
Buckle anterior surface of shoulder cap
Where does the chest strap run?
Horizontally across chest and inferior to the axilla of non-amputated side
Where does the chest strap terminate?
posteriorly on the proximal end of the elbow flexion/terminal device control cable
Where does the elastic suspension strap attach posteriorly?
To the horizontal strap about midline
Where does the elastic suspension strap attach anteriorly?
To the proximal surface of the socket shoulder cap
Where does the elastic suspension strap pass over?
The shoulder along a diagonal path
What does bi-scapular abduction produce and what is it lacking?
Produces good power, but little excursion
What can provide increased excursion?
Excursion amplifier
Where does the control cable originate for the excursion amplifier?
posterior surface of the socket
Where does the excursion amplifier control cable pass through?
A small pulley that is attached to the posterior horizontal harness strap via a hanger
Where does the excursion amplifier control cable enter?
The proximal opening of the split housing
What changes with the base-plate and retainer for a excursion amplifier?
They are Mounted more proximal than with transhumeral prostheses.
How much excurion is produced with 2.5cm of bi-scapular abduction?
5cm excursion
For the elbow lock, what makes up the anterior harness?
Anterior strap: Superior leg is non-elastic Inferior leg is elastic Control strap: non-elastic elastic
Where does the control strap originate on the anterior harness of the elbow lock?
On chest strap
Where does the non-elastic portion attach of the anterior harness control strap of the elbow lock attach?
The lock control cable
Where does the elastic portion of the anterior harness control strap of the elbow lock attach?
The socket midway between the two legs of the bifurcated straps
What control motion is used for the elbow lock?
Bi-scapular adduction
What is an option for waste belt lock control strap?
Anchor strap
Where does the anchor strap wrap?
Around the waist
Where does the control strap attach for the anchor strap?
Obliquely to anchor strap
Where does the anchor strap attach?
To the lock control cable on medial socket brim
What is the control motion of the anchor strap?
Amputated side shoulder elevation
Where is the nudge elbow unlock placed?
With in reach of the patient’s chin
What is the control motion of the nudge elbow unlock?
Chin nudges the lever to lock and un-lock
When are nudge elbow unlocks used?
For most severe involved patients
