transfemoral amputations - part 2

flexible sockets

- inc comfort, esp in sitting

- allow for 'window' to relieve areas of discomfort/pressure

- can reduce weight of socket

- inc pressure on limb, inc proprioception

- inc muscle activity

- can be used with quadrilateral sockets, great success with ischial containment sockets

straight suction suspension

total contact with skin

- no interface

- use pull sleeve to don

- rare

suction with seal-in liner suspension

same as TTA; more successful

pin (shuttle lock) suspension

same as TTA

- less successful

lanyard suspension

use of a strap attached to distal end of the liner

- pulled through channel in socket and secured to outside of socket

TES belt suspension

elastic belt that wraps around waist

- usually 2º suspension

Silesian best suspension

belt that wraps around waist

- usually 2º suspension

ratchet system

belt with ratchet to tighten suspension

- usually 2º suspension

straight suction

- hard socket in contact with skin

- expulsive valve used to create negative pressure vacuum

- good proprioceptive feedback

- suction can be lost with perspiration with potential for skin irritation and difficult to don

seal-in liner

- same as TTA

- requires alcohol

- can start donning in sitting and then move into standing

- expulsion valve for vacuum seal

lanyard suspension

strap around bottom of liner, where pin would be found

- very successful for TFA

- good choice in most cases for people with poor dexterity

- attaches to lateral wall of socket

- lateral attachment can sometimes cause external rotation of socket

TES belt

attaches to proximal part of socket

- wraps around waist

problems of TES belt

- cumbersome

- causes IR

- elastic tends to loosen during activity

Silesian belt

attaches to proximal socket

- not elastic

- uses belt buckle vs TES velcro

- smaller and tends to be more difficult to don

ratchet system

thicker belt than Silesian best

- attaches using a ratchet like buckle

- ratchet system allows adaptability with the patient, as they fluctuate in size

- can change the tension of the system

- waist vs lateral strap but can still be difficult to don

prosthetic knees

support body weight during stance phase at any gait speed and surface

- allow for smooth and controlled movement of shank and foot during swing phase

- allow for stair climb, descent, sitting, kneeling

goal of prosthetic knees

get as close to duplicating normal knee function as possible

- difficult to duplicate normal knee function as they are responsive NOT proactive

prosthetic knees - swing phase control

degree of variation of the speed of swing in response to cadence

prosthetic knees - stance phase control

stability of knee from heel strike to terminal stance

- depends on alignment, knee mechanism, pt voluntary control

ideally the knee axis falls where?

on or slightly anterior to TKA line to bring body weight anterior to knee at hamstring

- creates extension moment

knee axis more posterior =

knee flexion moment

- more mobile

knee axis more anterior =

knee extension moment

- more stable

secret to transfemoral gait

have knee axis posterior but on big toe

- have to get over big toe to bend the knee and move forward

types of prosthetic knees

- single axis (hinge)

- manual lock

- weight activated

- polycentric

- hydraulic (fluid control)

- microprocessor

- power

single axis knee

mostly used with children (first time up)

- no stance control when unlocked (free swinging)

- single speed swing phase control only

- slow and energy demanding

ultimate single axis =

manual lock knee

- prosthetic for transfers

single axis stance phase control =

weight activated

- need to push over big toe to unlock it

single axis - manual locking knee

knee is locked in extension

- release on socket to allow knee to bend in sitting

- indicated for pts that are unable to control a prosthetic knee

- inc stability in standing

- inc energy consumption in gait

- 2º gait abnormalities caused by locked knee

single axis - weight activated knee

- single axis knee joint

- stays locked in extension from 0-20º

- after 20º knee is free swinging with no support

single axis - weight activated knee; how it is activated

- weight activated friction brake system

- weight prosthesis in <20 degrees knee flexion = brake

single axis - weight activated knee --> gait

- at toe off, knee if free swinging

- upon WB, in 0-20º knee becomes locked and can accept weight

'safety knee'

single axis - weight activated

- false sense of security and responsible for many falls

- can place an extension assist on the knee to aid in swing phase for inc safety

- lack of swing stability inc pressure on contralateral limb

polycentric knees - multi-axis knee

as knee bends the joints move thus maintains the center of the knee posterior to weight line

- common types = 4 bar vs 6 bar "total knee"

- can add extension assists to aide in swing phase and inc safety

- knee is locked in midstance

polycentric knees - gait

'all or nothing'

- very stable in stance

- swing = toe load (allows push off)

- when knee breaks, joint is free swinging while pt moves BW over toe

hydraulic knees

single axis, uses hydraulic fluid or air (pneumatic)

- some only provide stability requiring inc muscular control in swing

- can be more difficult to control in gait but is highly indicated for activity people/community ambulators

hydraulic knees - Mauch knee by Ossur provides what?

- stance and swing stability

- inc safety by providing stability in miss steps

hydraulic component

cadence responsiveness

- allows greater variance of gait speed

- hydraulic resistance provides smoother gait with declines

hydraulic knees offer resistance in

- stand --> sit

- reciprocal pattern with stair/curb descend and ascend

hydraulic knees - gait

pt must shift weight over toe

- achieving full hip extension followed by forward pelvic rotation to achieve swing phase

microprocessor knees

computer learns your gait and can accommodate for it

- improved cadence response, greater variance in gait

- inc stability

- stumble control

- optimum knees for varied terrain

- very expensive

- need to be charged

- C-leg and Rheo knee

Rheo knee

uses 3 force plates (2 read force, 1 reads angle of knee)

- waterproof

- actuator controls stance and swing phase

- reads steps 1,000x per second

- default to SWING

Rheo knee - controls in stance and swing

- force plates read inc WB through foot

- actuator uses electricity through metal rings making a magnet

- Magnetorheologic (Rheo) fluid = solid when in contact with magnets for stability

- force plates read weight shift over toe which allows actuator to turn magnet off and allow knee to swing through

pros of a Rheo knee

- effortless swing initiation enables smoother gait

- adv actuator and resistance control ensures best possible resistance

- more support in stair descent and min effort needed in level ground gait

- constant power spring provides natural progression in swing

- five-sensor gait detection ensures stability and dynamic response

- magnetorheologic tech enables instant response

C-leg

uses 3 force plates (2 read force, 1 reads angle of knee)

- microprocessor control hydraulic knee

- fall back mode of STANCE control

motor in power knee allows active movement

motor in knee allows active movement

- reciprocal stair descent

- STS

- stumble recovery

- cadence variance

power knee

may dec energy consumption (no support in lit.)

- very expensive, noisy, and heavy

- pt must be very athletic and confident

- early training vs longtime user

- potential to allow pt to accomplish a lot but may be difficult to learn

advanced microprocessors - Ottobock specifications

- patient weigh max 330 lbs

- weight of knee joint 2.9 lbs

- data collection every 0.01 seconds

- adjustable activity modes = 5

- operating time with fully charged battery = 5 days

- max knee flexion angle is 135º

Ottobock has multi-modal proprioceptive input to provide what?

auto-adaptive hydraulic swing and stance phase control

Genium Ottobock

- first to allow reciprocal stair ascension

- removes weight component to gait and relies solely on angles

- can lock in a squat to help dec pressure on contralateral limb

K-3 Ottobock specifications

- 3.12 lbs

- BW up to 275 lbs

- waterproof

- 5 activity modes

- battery life = 5 days

- max knee flexion angle = 135º

K3 advanced microprocessors

- waterproof (completely submergible for showering, swimming, boating, fishing, etc)

- run, walk, run via remote

- walk2run mode for short stances (changes swing angle)

- real-world mobility (running, walking, bwds, crossing obstacles, climbing stairs)

- 6 activity modes, plus a silencer (for biking, golfing, driving, etc)

optimized physiological gait (OPG) function

- componentry seen on Genium and X3 prosthetic knees (4º of pre flexion at IC)

- adaptive yielding control for control stance flexion and extension movement without resistance (dependent of forces affecting the knee)

- dynamic stability control (ensures knee will not release stance resistance during unstable conditions)

OPG has stance release on ramps to provide

- inc knee flexion and foot clearance

- less hip flexion force needed to bring shank into extension

OPG adaptive swing phase control

- instantaneous adaptation to varied walking cadences and changes in pendular mass

- achieves 60º knee flexion during swing, not dependent on speed

hip disarticulation socket

- heavy, uncomfortable, inc energy demands

- full weight taken throughout soft tissue and residuum

- encloses ischial tuberosity for WB

- cover iliac crest for stability and suspension

- medial aspect cut for contralateral limb/genitalia

- relief over A/P iliac spine

hip disarticulation socket - Marin Bionics "Bikini Hip Socket"

- low profile, light weight design

- iliac crest stabilizers instead of bucket design

hip joint - helix hip joint

hydraulic hip joint

- assists in swing and stance phase

- assists in STS

- inc stability of prosthesis

- hydraulics improve overall gait for patient's with hip disarticulations and hemipelvectomy

other components

- torsion adaptors

- rotators

- shock absorbers

PT considerations - gait

- same as TTA + knee and maybe hip joint to control too

- balance is key

- weight shifting/prosthetic trust

PT considerations - ther-ex

- trunk strength

- hip strength (hip mvmt controls all prosthetic knees)

gait with prosthetic knees

- weight shifting

- prosthetic control of different movements that cause knees to react in different ways

how to obtain swing phase with a prosthetic knee?

- weight shift over toe

- obtain full hip extension and forward pelvic rotation

- posture is very important

what type of prosthetic knees can STS and stair descent

hydraulic and microprocessor knees