Daves Ak Therapist Presentation 06

Scheck & Siress Advanced Orthotics and Prosthetics David Rotter CPO UIC Medical Center

Transfemoral Prosthetics

Basic criteria: What can patient bear weight on to support their body weight?

Patient bears weight on: 1.Ischial tuberosity 2.Soft tissue of residual limb 3.Gluteal tissue

Midstance

Heel strike

Heel off

History of transfemoral socket design • Plug socket • Quadrilateral socket • Ischial containment socket

Wooden plug socket • Relied on soft tissue bearing • Patients limb adapted to socket shape not visa versa

• Major problems with adductor rolls

Above knee socket design: • Quadrilateral:

Was the standard for forty years

• Ischial-

containment: Currently, most frequently used design

Quadrilateral design • Originated at UC

Berkley, designed by Charles Radcliff. Concepts originated in Germany • Characterized by a narrow AP and a wide ML- maintain ischium on shelf • Primary design used until 1980’s

Deficiencies in Quadrilateral design Quadrilateral socket *Nothing to prevent socket from sliding laterally

Ischium can slide off shelf

Ischial containment • Designed in the 1980’s to

address recurring problems in quad socket • Characterized by a narrow ML and wide AP • Ischium seated within the socket • A more natural shape • Currently most accepted socket design

Biomechanics of above knee sockets Rationale for Ischial containment socket

How do we all stay standing? • What muscles are firing at midstance to keep us upright?

• How is an amputee different?

Above Knee Gait • What is this gait pattern called?

• What is causing it?

The femur will abduct until it meets resistance: How can we control this?

Position of femur in socket: • During midstance,

femur abducts until it meets resistance.

• Compromises

effectiveness of abductors.

I.

We effect control by…. • Adducting

the socket as much as possible: To

provide a counter force to the femur, as the hip abductors fire.

II.

Block Ischium from sliding out of the socket Force coupling

A force coupling maintains adduction

Force coupling

Comparison of quad to ischial containment Quad

Ischium can slide off shelf

Ischial containment

Ischium is locked in socket

•Therapists… What can you do to help the above knee amputee with coronal plane stability? Strengthen patients hip abductors

Suspension Modalities: • Suction • Silesian belt • Hip joint & pelvic band

Suction suspension • Straight

suction socket with valve – Best form of suspension – Greatest proprioceptive feed back

Advantages Disadvantages • Eliminates pistoning • Most maintain stable volume

• Prostheses feels lighter

• Somewhat difficult to donn

• Improves

proprioception

Traditional suction suspension

Silicone suspension sleeves

Silesian belt: provides suspension and rotational control • Webbing material

• TES belt- prefabricated

Advantages Disadvantages • Easy to donn • Adjustable

• Some pistoning present

• Added bulk

Hip joint and pelvic band with belt: This was primary form of suspension before suction sockets • Maximum ML

control • Good control of rotation • Easy to donn • Very reliable

Indications • Short residual limb • Weak hip abductors • When ML stability and rotational control are needed • Swing phase control • Disadvantages:

– inherent pistoning – bulky, increased weight

Categories of knees • Manual locking • Weight activated stance control • Polycentric • Single axis constant friction • Hydraulic swing and stance units

Manual lock knee • Most stable alternative • Leg is locked through swing and stance

• Patient has to pull on

lever to disengage lock

• Highest energy

expenditure of any knee system

Weight activated stance control • Most used knee in prosthetics

• A braking mechanism is

applied as long as there is weight on the knee

• Used on new, geriatric patients

Weight activated knee

Polycentric knees • Instantaneous center of rotation

changes making knee very stable in extension and easy to bend in flexion • Shortens during swing phase • Stability is in the alignment of the linkages

Used on knee disartics.

Single axis constant friction • Usually found in

exoskeletal set ups. Used in children’s prostheses.

• For patients with

excellent voluntary control

Hydraulic swing and stance units • Hydraulic

simulates quadriceps with yield feature

• Allows variable cadence

Hydraulic swing and stance • Hydraulic

designed to match the speed of the contralateral limb.

• As speed

increases, resistance increases.

stable during stance?

• Voluntary control • Alignment stability • Mechanical stability

Voluntary control • Dictated by

patients strength in their residual limb

• Hip extensors

• Limb length

Alignment (inherent) stability Determined by how •

prosthesis is aligned

– the knee axis must be behind the weight line during heel strike - heel off phases of gait, done during alignment of prosthesis.

• As long as the weight line is anterior to the knee, there is an extension moment

Mechanical stability • Mechanical

components of the knee insure that knee stays extended during critical points of stance phase Examples: Locking knee Weight activated knee

• Mechanical stability:

Weight activated

Polycentric Hydraulic stance phase

• Alignment stability:

Polycentric

• Voluntary control: Single axis

Single axis

How is the knee controlled in swing phase? • 1. Mechanical constant friction knees

• 2. Cadence responsive hydraulic knees

Mechanical constant friction • Indicated for one speed ambulators

• Few mechanical parts • Light weight • Unable to have variable speed cadence

Slight brake applied all the time

Hydraulic and pneumatic cadence responsive knee units • Indicated for variable speed ambulators

• Most fluid natural gait • Patient has the ability to adjust setting for desired activity level.

Microprocessor knees

Hip Disarticulation • Stability dependent upon weight line:

Prescription criteria…. tying it all together

What is the optimum amputation length?

Knee disartic vs. Transfemoral • Longer lever arm • End bearing • Self suspending

• Very poor

cosmetic result • Not enough room

• Always leave as

long as possible to maximize lever arm • Able to achieve a normal knee center and fit components

Recap • How can the therapist influence good coronal plane stability?

Strengthen hip abductors: To oppose rotation of pelvis to contralateral side in single limb stance

• How can the therapist influence knee

Strengthen hip extensors: To afford good voluntary stability? control of knee

• How can the therapist influence better

balance and endurance even before patient patient up and walking on sound limb as soon getsGet the prosthesis? as possible

Case studies:

74 year old female with rheumatoid arthritis, has 15 degree flexion contracture, strength is 3+. She is able to stand on one leg for 45 seconds. Residuum is medium length. She is very motivated to walk again.

traumatic AK amputation. Strength is 5. Limb is medium length. He has had a training prostheses and is now ready for his permanent. He would like to go back to school to continue studying computers, playing basketball and break dancing.

Old vs. new components…. Does it make a difference?

49 year old male presents in clinic with knee disarticulation. Strength is 4, he is in general good health. He would like to go back to his factory job working on the delivery ramp off loading incoming materials.

Thank You!