Week 12: TF prosthetic componentry & gait deviations

Transfemoral Socket Designs

Quadrilateral, Ischial Containment, Sub Ischial, Variations & Suspensions

Transfemoral Prosthesis Socket

A device designed to replace the function of a missing leg above the knee.

Rotator coponent

Allows for legs to cross over the other.

Mechanical knee/Knee joint

Makes hip extension very important.

General fitting Principles of TF prosthesis considerations

-Anatomical structures

-Alignment

-Socket Contour for functioning muscles within the socket itself

-Stabilize skeletal structures

-Distribute forces - over large surface area and over neurovascular bundles

WB area for TF socket

ischial tuberosity

Transfemoral socket designs limitations

-Limited ability for contouring/stabilization based on what structures are encompassed

-Decreased proprioceptive feedback

-Decreased stabilization and rotational control leading to high energy expenditure costs (70 -75% more energy cost)

-Requires medial/lateral stability to account for the need of control of abduction/adduction in the stance phase

TKA (trochanter, knee, ankle line)

Needs to be aligned for gait and activities.

Quadrilateral Socket

Developed in the 1950s; characterized by four walls.

Anterior wall of Quadrilateral Socket

Directed posteriorly to stabilize ischial tube.

Medial wall of Quadrilateral Socket

Provides relief for adductor tendons specifically adductor longus.

Lateral wall of Quadrilateral Socket

Contains the greater trochanter for M/L stability.

Quadrilateral Socket

quad shaped

-has horizontal POSTERIOR shelf for ischial tuberosity and gluetal muscles

-medial brim: continues at the same level as the posterior shelf

-anterior wall/brim: 6-8 cm higher than the post/med walls

-lateral wall: same height as the ANTERIOR wall to assist with med/lat stability.

quadrilateral socket characteristics

-provides relief for hamstring, glute max, and rectus femoris and adductor tendons

-Contains an ischial seat

-Distal pressure on end of femur because No bony lock to stop femur from movement

ischial containment characteristics

-More triangular in shape

-Relief for trochanter and adductors

-Contains ischium in socket

-GT and ischium are contained

-Posterolateral wall acts as counterforce against the femur to evenly distribute force and stop distal pressure on femur

-Bony lock

-Lower anterior wall to allow greater hip ROM

-Wider AP than M/L to resist lateral shifting of the socket

Most commonly used socket design for transfemoral amputees

Ischial containment socket

Ischial containment

More triangular in shape, developed in the 80s-90s.

Weight bearing in Ischial Containment Socket

Primarily on the ischium and ischial ramus.

Compared to quadrilateral socket, ischial containment better accommodates

fleshy limbs and high activity patients

Indications for Ischial containment

-Enhanced coronal stability needed

-Lower levels of voluntary control

-Shorter residual limbs

Advantages of Ischial containment

-Enhanced coronal stability from bony structure

-Proximal tissue contained in socket

-Amount of containment can be adjusted

-Potential for ischial WB

Limitations of Ischial containment

-Clinical experience required to create optimal fit

-High proximal trim line

-Hip ROM may be limited

Ramal containment idication

Enhanced coronal stability w/ minimal trim lines

Ramal containment advantages

-Enhanced coronal stability from bony structure

-Proximal tissue outside of socket

-Reduced trim lines

-Enhanced hip ROM

Ramal containment limitations

-Clinical experience required to create optimal fit

-Not comfortable unless optimal fit around ascending ischial ramus is achieved

-Lengthy fitting process

Subichial Quadrilateral indications

-Longer residual limbs

-Higher levels of control

Subichial Quadrilateral advantages

ischial WB

Subichial Quadrilateral Limitations

-Clinical experience required to create optimal fit

-Minimal coronal stability

-Narrow AP dimension

-Predetermined Rectangular shape

Suchichial vacuum assisted indications

-Longer limbs

-Higher voluntary control

-High gadget tolerance

-Uses hydrostatic WB

Suchichial vacuum assisted advantages

-Reduced trim lines

-Excellent suspension that may enhance coronal stability issues

-Amount of assisted vacuum suspension can be regulated

-Hip ROM not limited

Suchichial vacuum assisted limitations

-Clinical experience required to create optimal fit

-Tissue proximal to the brim may be stressed

-Multistage donning process

-May be bulky

Ischial Containment Socket Variations

-Cutouts in socket allow muscle freedom and movement

-Use of flexible inner sockets paired with rigid sockets

-Lowering posterior wall to allow hip ROM

-Addition of padding for relief

-Dials can be used to adjust for edema and ROM

Suspension Systems

Includes suction, lanyard, locking liner, and Auxillary suspension

Auxiliary suspension:

used for those who don't trust primary suspension

Auxiliary suspension: types

-Total Elastic Suspension Belt (TES)

-Silesian belt

-Hip joint and Pelvic band

-Suspenders

-Osseointegration

Liner suspension advantages

-Allows Full ROM

-Donned in sitting

-Good visual feedback

-Pin liner allows for good auditory feedback

Liner suspension Limitations

-Heat/perspiration

-Skin irritation

-Decreased liner suction

-Liner break down

Traditional Suction

Patient pulls residual limb in with "sock" or "donning aide"

Valve is screwed in, one-way valve, lets air out

Positive pressure socket

WB pushes air out of socket

negative pressure socket

Air pump removing air

Donning a traditional socket may be difficult if a person has

-Generalized weakness

-Poor balance

-UE involvement

-Cardiac issues may limit energy expenditure

Wet-Fit TF Donning

Application of "lubricant" to the skin and slide the residual limb into the socket→Gel or lotion that evaporates to create suction→used for Solid/slender limb for wet fit

Suction suspension advantages/indications

-Works better with Long residual limbs

-Stabilizes limb volume

-Must have Good skin

-Must have Good UE strength

-Best suspension/decreases pistoning

-Better proprioception

-No straps/belts required

Contraindications/disadvantages for suction suspension

-Volume fluctuation

-Short residuals

-Severe scarring

-UE weakness

-Difficult to don

-Hot=lose suspension due to perspiration

-Requires good SLS

Gel liner (non suction)

-Used with lanyard or pin locking

-Good adjustability

-May have rotational problems

-Easier to don vs. traditional suction

-Lanyard may provide rotational control more than pin locking system

Lanyard Suspension

Pulled through bottom of socket and tightened at lateral surface.

gel liners (non suction) advantages/indications

-Provides positive suspension

-Reduces shear forces

-Used with Active individuals

-Stabilizes limb volume

-Can be used with Fleshy limbs because the liner secures the suspension

-Doesn't limit ROM

gel liners (non suction) disadvantages/contraindications

-Relatively difficult to don with bad dexterity

-Skin reaction to gel liner/skin sensitivity

-Decreased Rotational control

-Hygiene problems in the adductor area

-Severe UE impairment

Auxiliary Suspension Types

Includes elastic belts, Silesian belts, hip joints, pelvic bands, and suspenders.

Total Elastic Band Suspension

-Flexible material/neoprene

-Prevents bulging in clothing because its attached to socket

-Wraps around proximal circumference of the socket

-Wraps around the person's waist, like a belt

-Chosen for someone who's had recent surgery who may have edema or those who cannot use suction suspension

Advantages of TES

-Inexpensive

-Easy to don

-Adjustable

-Adds coronal stability - auxiliary not sole provider of Suspension

Disadvantages of TES

-Does not add much rotational control

-Pistoning

-Skin irritation/difficult to fit with large abdomen

-Increased straps and buckles

-Increased bulk around waist

-Freq. replacement

-Limited durability

Silesian Belt

Made out of nonelastic material, provides rotational control, and gives patient some security with suspension.

Hip Joint

-Single axis at hip joint

-Allows flexion and extension

-Limits abduction

-Attached posterolaterally

-Positioned above and forward to the greater trochanter to allow singleaxis hip motion

-May be uncomfortable

-Laminated to socket interface

Pelvic Band

Leather belt with buckle, positioned between iliac crest and trochanter.

Advantages of Pelvic Band/ hip joint

-Maximum medial lateral control

-Used with Weak abductors or short residual

-Ease of donning like a belt

-Good swing phase control

Disadvantages of Pelvic Band/hip joint

-Bulky

-Inherent pistoning

-Increased weight

-Don't use if a person has good medial lateral stability

Suspenders

Suspension over shoulders that may assist knee stability, considered a last resort.

OsseoIntegration

An implant placed into the femur with components sticking out of the skin.

Cons of osseointegration

-Skin has to heal around component

-Long healing time

-Prone to infection from open wound

-Non WB originally

Pros of of osseointegration

-Components can attach directly to bone

-Improved proprioception and vibration through the bone

Donning a Socket Suspension

Using a sock, ensure it's pulled all the way up and the hip is not in extension.

donning a lanyard suspension

Slide the strap underneath the silver bar and out the front of the prosthesis-->Slide prosthesis up residual limb-->Tighten strap on the prosthesis

Seal in liner for TF prosthetic

Spray liner with alcohol to use as lubricant for ease of donning

Don prosthetic

Stand and allow Bodyweight to push air out of the socket so the leg and liner can get to the bottom of the socket

Sit down and use one way valve negative pressure to remove rest of the air

TF alignment is contingent on

-Stance phase control critical

-Knee alignment should be on or just anterior to TKA(trochanter knee ankle) line to provide stance control

-Socket set in 5 degrees flexion (more with hip flex contracture)

-Set in slight adduction for M-L stability

With weak residual limb may select to align

posterior to TKA line

why is a TF prosthetic set in slight adduction?

People have a natural adducted alignment of the femur

Transfemoral Knee Componentry Requirements

Durable, quiet, smooth, controlled swing, unrestricted flexion, Extension Stop to prevent recurvatum, Friction with the swing phase to prevent unrestricted swing phase, and stability in stance.

What influences choice of TF prosthetics

-Alignment

-Limb Length

-Functional Level

-Control of limb musculature

-Component features (knees, ankles, feet)

Prosthetic Knee Units Classification

Classified by axis, stance phase control, and swing phase control.

Classes of Knee Components

Monolithic

Single Axis

Stance Phase Control

Polycentric

Manual Lock

Fluid Controlled (hydraulic)

Microprocessor

Monolithic Axis knee

-No articulation

-Used for Very young patients who had good knee stability

-For patients who have No room for the knee

-Long residual limb

-Those who are Not ready for muscular control

-No knee is incorporated into the prosthesis

-Movements come from residual limb in the hip

Single Axis Knee characteristics

-Outside hinges used for for long residual limbs to provide femoral length equality

-Step length equalization

-Durable

-Easily repaired

-Inexpensive

-Free Swinging

-May require extension assist

-NO inherent friction or stability

-Poor Cosmesis

Single axis knee is used for those with

Proximal Femoral Focal Deficiency, Rotation-plasty, knee disarticulation

Single Axis (general) indications

-Longer residual limbs if using "constant friction"

-Require a person with good muscular control

-Cost containment

-Good with Children

-Durable

Single Axis Knee Pros

-Inexpensive

-Durable

-Easily repaired

-Requires Good muscular (hip ext.) control/long residual limb

-Good for most levels of transfemoral limbs

Single Axis Knee Cons

-Little inherent stability

-No stance control

-No variation in swing with gait speed changes because of constant friction

-Not suitable for patients with high functional levels

-Not appropriate for patients with short residual limb lacking mechanical advantage of long femoral lever/muscular control

Single axis friction knee - ext. Assist

As the knee bends the spring bends to assist with extension

Single Axis pneumatic knee

Air controlled joint to provide friction and control for swing

Single axis knee with friction lock

Friction locked into extension

Single Axis knee with cable lock

Cable attaches to socket to allow the pt to control locking an unlocking

Polycentric Axis characteristics

-More variation in knee flexion

-Stability (stance) due to linkages

-Decreased stability in pre swing

-Changing instantaneous center of rotation

-Can include pneumatic or hydraulic to allow for variation in speed

-Swing phase Clearance (shortening)

-Provides Femoral length equality (provides shortening in long limbs)

-Assist those with Weak hip ext./very short limbs

Polycentric Knee 4 Bar Advantages

-Provides some stance AND swing phase control

-easier initiation of knee flex

-Good for long residual limbs

-Moving knee axis which provides for higher toe clearance on swing

Polycentric Knee 4 Bar Disadvantages

-Increased wt.

-Requires good voluntary knee control (understanding the mechanics for making it function properly)

-Increased maintenance

Polycentric 4 bar indications

-Very short limbs

-Weak hip extensors

-Multiple axes 4-7 bar linkages

-Provides for increased stability

-Imitates normal knee

-Inherent stance phase stability

Polycentric 4 Bar

Has moving center of rotation through a 4 or more bar linkage system

Manual Lock Knee indications/characteristics

-For patients who must rely on mechanical stability in stance

-Single axis knee with locking pin mechanism

-Auto locks with extension

-Often fit shorter

-Manual unlocking with pulley or lever system

-Often used in initial training

advantages of manual lock knee

-External system locks knee in ext. until it is manually unlocked

-Gives Total knee stability

-Option for progression to swing knee, allowing pt. to concentrate on wt. Bearing without having to concentrate on knee Control

Manual lock knee disadvantages

-Stiff knee gait if locked, requires considerable energy

-Used very limited

-Deviations: Hip hike, circumduction, vaulting

Locking mechanism advantages

-Maximum Stability

-Indicated for: weak, blind, bilateral Tf prosthesis

Locking mechanism disadvantages

-Unnatural Gait

-Must be UNlocked to sit

-Increased energy expenditure to walk

-Gait deviations: Hip hike, circumduction, vaulting

General Principles of Friction Control

-Adjustable/Simple design/Durable

-Primarily for SWING PHASE control only

-Controls Rate of knee flexion (limits heel rise)

-Controls Rate of knee ext. (prevents terminal impact slamming into extension)

-Friction is adjustable but constant

-K1-K2 can use the same friction for flex./ext. - single cadence

-All lengths of Transfemoral limbs

-Hip disarticulation limbs

-Constant velocity

-Not for variable cadence

Stance control knee: advantages

-Provides Stance Phase Stability

-"Safety knee"

-Durable

-Indicated for those with slow walking speeds or with minimal gait speeds

-Prevents unwanted knee flexion during stance

-Short residual limb, weak hip extensors

Stance Control Knee Disadvantages

-Wt. has to be totally off prosthesis to initiate swing

-No adjustments to gait speed changes

-Limits gait speed

-Similar disadvantages as with single axis knee

Braking Mechanism knee

-Locks upon wt. bearing (10-15 degrees)

-Weight. activated stance control

-Indicated for: short TF, weak hip ext., poor balance

-Pt. must unload for swing phase

-Can delay knee flex. In pre swing

-Can lead to hip hiking, vaulting

-Difficult for BLE TF esp. For sitting

braking mechanism advantages

-Increased stability

-Friction Brake

braking mechanism disadvantages

-Maintenance

-Difficulty with stairs

-Pt. develop gait deviations because the leg must be totally unweighted to initiate swing phase

Extension Assist

-Provides for Stability at Initial Contact

-Controls rate of knee flexion in swing to limit heel rise

-Assists in terminal swing to make the knee more stable in stance phase

without an extension assist, a pt may demonstrate

-Instability at IC

-XS heel rise

-Uneven timing of steps

-"Hop-Skip" Running

Hydraulic vs pneumatic hydraulic advantages

-Swing and stance phase control

-Greater variability vs polycentric

-Assists with normal gait pattern

-Some are lightweight

-Hydraulic closest to normal knee function