LL prosthetics common principles and trans-tibial prosthetics

how do you select level of amputation

tissue viability and wound healing

potential for function (trans-femoral vs trans-tibial)

cosmesis

why is a longer limb better for function

longer lever arm

can handle prosthesis better

disperses forces better because increased surface area

what surgical factors have the best prognosis for soft tissue

primary closure and closed without tension

incision not in the area of weightbearing

mobile scar without adhesions

what does secondary closure increase risk of

infection

are disarticulations weightbearing or non weightbearing?

weightbearing

are transections weightbearing or non weightbearing

non weightbearing

if the patient is a TT wbing, what socket is appropriate for them

patellar tendon bearing

if a patient is TT and non-weight bearing, what socket is appropriate for them

total surface bearing

brusing, pressure ulcers, or blisters are indicators of

incomplete contact in the socket. creates shearing and friction leading to skin breakdown

what level of amputation is best for function with trans-tibial patients

when 40-50% of residual limb is preserved

skin flaps are named by….

where the flap originates - leave excessive skin on one side and wrap it around to the other side

anterior incision = posterior skin flap and vice versa

what is the most commonly seen trans-tibial technique

burgess

what is the method of closure for trans-femoral amputees

equal skin flaps

the ideal residual limb is

muscular and has well-padded bones with rounded/contoured edges

what is a myodesis procedure

a procedure where the muscle is attached to the periosteum of the bone

a myodesis provides what benefits to function

good distal muscle stabilization and control of RL

what layer of muscle is a myodesis typically done with

deepest muscle layer

adductors then quads

what is a myoplasty procedure

a procedure in which the muscle is sewn to opposing muscles

what layer of muscle is a myoplasty typically done with

superficial muscles first but can be multi-level

what is a tenodesis procedure

a procedure in which a severed tendon is reattached distally

what is the best method for stabilizing muscle

tenodesis

what kind of transection is a tenodesis typically only able to be done for

disarticulation

what do transected nerves always form

a neuroma

are neuromas symptomatic?

typically they aren’t but if the nerve stays tensioned or has increased pressure on it, it may be symptomatic

what tissues are pressure tolerant

muscle and fat

what tissues are pressure intolerant

nerves and bone

where should the mechanical axis of a joint should be placed

so that it is congruent with the anatomical joint axis as much as possible

this will prevent undesirable forces being applied to the limb

how many K levels are there

K0 - K4

K0

very dependent patient

K1

household ambulator

K2

community ambulators

K3

higher level community ambulators

K4

exceeds beyond basic ambulatory skills

athletes, children

what are the components of any prosthesis

foot and ankle assembly

shank or pylon

socket

suspension

knee unit if TF

what is the difference between a shank and a pylon

a pylon is a type of shank - it is the exposed metal portion (endoskeletal)

exoskeletal

looks like a leg and has foam covering with hard shell

heavier than endoskeletal

endoskeletal

exposed pylon

lighter weight than exoskeletal

are knee disarticulations considered TT or TF

TF

what levels of amputation are considered for a trans-tibial prosthetic?

partial foot

ankle or syme

tib-fib

what are the two types of sockets for TT amputations

total surface bearing and patellar tendon bearing

what does the pumping action of the PTB socket help with

the loading and unloading during gait creates a pumping action that pushes blood flow and lymphatic drainage. This assists in venous return and decreases swelling with improved circulation

what is the mechanism of the PTB socket

pressure is built up over the patellar tendon (tendons are great at taking load) with some additional pressure into the shaft of the bone.

What areas are concerns for PTB sockets to have pressure at

fibular head

tibial crest

what are the two types of sockets for a PTB socket

hard socket

soft socket (soft liner + hard socket)

PTB hard socket

stump socks or liners used as interface between socket and limb

patient initially fitted with 3 ply sock/liner

PTB soft socket

soft liners are used as a filler to tape up space between sock and hard socket

increases the distribution of pressure to decrease shear force

goal is to have greatest # of ply with lease amount of liners/sockets to keep friction low

indications for a soft PTB socket

used with patients with tissue shrinkage, bony resideual limbs, areas of increased forces on tibia and children

anterior wall of PTB socket

primary Wbing wall - increased load on patellar tendon

anterior trim line bisects the patella

medial and lateral walls of PTB socket

control the knee mediolaterally during stance

rise above the proximal pole of the patella

is the medial or lateral wall higher in a PTB socket

lateral to mimic the natural varus that occurs during loading

posterior wall of PTB socket

pushes anteiror residual limb against anterior wall

equal or just distal to mid patellar tendon - prevents compression of neurovascular structures

medial aspect is lower the lateral aspect to allow for medial hamstring contraction

how do you adjust the posterior wall of the PTB socket based on the RL length?

longer limb = lower wall to allow for more knee flexion

shorter limb = higher to retain the soft tissue in the socket

how many degrees of flexion is a PTB socket built in at the knee

5 deg

how many degrees is the socket tilt relative to the prosthetic foot and what does this do

3-5 degrees anteriorly

equivalent to dorsiflexing the foot and placing knee in flexion to increase the WBing area on the RL

what is the typical alignment of a PTB socket in regards to the heel and socket

the midline of the heel of hte prosthetic foot is directly under the socket or inset up to ½ inch

where is the pressure on the RL if the socket is inset

proximal medial and distal lateral

insetting the socket contributes to what force at the knee

varus

where is the pressure on the RL if the socket is outset

proximal lateral and distal medial

outsetting the socket contributes to what force at the knee

valgus

why would you outset the socket?

if the RL is short

If you outset the socket, what else must you do to prevent pain and skin breakdown

extend the socket proximally to increase the area for pressure distribution

What is a TSB socket

Non-WBing as the forces are applied over the entire RL (magnitude of forces dependent on tissue type)

allows for as much force as comfortable

eliminates need for patellar tendon bar

what are the different types of interfaces used with a TSB socket

gel liner used alone

gel liner with pin/lanyard

gel liner with suction (seal-in)

elevated vacuum