Lower Limbs Prosthesis
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Transcript of Lower Limbs Prosthesis
Lower limb ProsthesisAdib Mursyidi Iskandar MirzaOrthopedics
Outline
• Definition• Aim of prosthesis• Level of amputations of lower limbs• Components of prosthesis• General issues
Definition
• Prosthesis• Device to replace part of the limb or missing limb
“substitute”• Orthosis• Externally applied mechanical devices • Support weakened injured, paralyzed, diseased part
as supplementation• Prosthetist• Person skilled in prosthetics and its application
Aim of prosthesis
• To substitute for a lost part• To restore lost function• Comfortable ambulation • Minimal/reduce of expenditure of energy• Minimizing the shift of the center of gravity of the body during gait
Level of amputation• There are several
levels of lower limb amputation
• Most common are transtibial and transfemoral
Component of prosthesis of Lower Limbs
Parts of prosthesis1. Socket
2. Suspension system
3. Knee Joint
4. Shank/pylon
5. Foot/Terminal device
Suction& Mechl close fitting
Socket
• Most important part• Is the connection between the stump
and the prosthesis• Protects the stump and transmits
forces• Uncomfortable rejected• Contoured sockets fit closer to bone,
muscle, soft tissue• Provide support and relief
Suspension systems• For attaching socket
to body• Types of suspension• Sleeve, belt, straps,
or cuff • Suction prosthesis • Mechanical close
fitting or silicon sock helps to maintain airtight seal
Suspension systems materials• Sleeve – made from
latex• Cuff – used to hold
prosthesis in residual limb• Belt/straps – use a
waist belt with elastic strap to suspend prosthesis
• Suction method – consist of silicon sleeve with short pin at the end will fit into residual limb and locks into socket
Knee joint1. Axis system2. Friction 3. Stabilizer
Axis system
• Single axis• Axis of prosthetic knee is same as that of weighty
bearing axis• Flexion easier, but stance phase control difficult
• Polycentric• Permits momentary axis of knee flexion to change
through the arc of motion increase knee stability
Medium friction
(hydraulic) friction
Constant friction
Friction mechanism• Changes knee swing by modifying the speed of knee motion• Adjust knee swing accordingly
• Constant friction• Applies uniform resistance throughout swing phase
• Variable friction-cadence control• Greater friction is applied at early and late swing
• Medium friction• Oil (hydraulic) friction• Air (pneumatic)friction• Allows best gait pattern best for active patients, but expensive
StabilizersManual locking
Stabilizer
Most unit do not have special device to increase stabilityPatient control knee actions through hip motions by• Manual locking : prevent knee
flexion• Friction brake : resist knee flexion
during early stance
Shank/pylon
• Use to connect the socket to the ankle-foot assembly• Allow axial rotation and absorb, store, and release
energyConsist of two types• Exoskeleton• soft foam contoured to match other limb with hard
outer shell• Endoskeleton• internal metal frame with cosmetic soft covering
Ankle-Foot Assembly
Ankle Foot Assembly
• Designed to provide support during standing/walking and shock absorption as well• Consist of 3 categories• Single axis foot• Solid ankle cushioned heel (SACH) foot• Dynamic response• Articulating• Non articulating
• Ankle hinge allow dorsiflexion and plantar flexion• Disadvantages• Poor durability• Poor cosmesis
Single Axis Foot
Solid ankle cushion heel (SACH)
• Most widely prescribed foot• Due to simple, low
cost and durability• Uses in patient with
low activity• Disadvantages – may
overload the non amputated foot
Dynamic response energy storing foot
• General use for most normal activities• Consist of • Articulating• Non articulating
Articulating
• Allow motion at the level of human ankle• Indications• Patients walking on uneven surfaces
• Advantages• Absorbs loads and decreases shear forces• Flexible keels• acts as a spring to decrease contralateral loading, allow
dorsiflexion, and provide a spring-like push-off
Non articulating
• Have short or long keels• shorter keels are not as responsive and are indicated
for moderate-activity patients• longer keels are indicated for high-demand patients
• Different feet for running and lower-demand activities available
Prescription of prosthesis• Type of prosthesis required• Level of amputation• Material of socket• Suspension mechanism• Type of cosmesis required
General Issues
• Choke syndrome• caused by obstructed venous outflow due to a socket
that is too snug• acute phase• red, indurated skin with orange-peel appearance
• chronic phase• hemosiderin deposits and venous stasis ulcers
• Skin problems• Contact dermatitis• most commonly caused by liner, socks, and suspension
mechanism• treatment• remove the offending item with symptomatic treatment
• Cysts and excess sweating• signs of excess shear forces and improperly fitted components
• Scar• Post operative scar
• Painful residual limb• possible causes include bony prominences, poorly
fitting prostheses, neuroma formation, and insufficient soft tissue coverage
• Ineffective suspension system• Poor socket fit• Stump volume changes• Foot alignment abnormalities