4) Pacto Internacional de Derechos Económicos, Sociales y Culturales
2.4. Derecho humano al agua en el Marco jurídico internacional
208
Prosthesis And Amputation
PR A Y F O R US
Ali H Buzaid
Ahmed Al-Khalifah.
2 Orthopedic Note Implants
Known problem of implantation:
Stress riser: a focus point of stress on an implanted orthosis is very likely to be its point of failure [Fracture]
o Upper and lower limits of internal Fixation device.
o Lower limit of hip prosthesis.
o Tumor
o Above or below a united fracture.
The problem was due the difference between the material and the bone elasticity . so they develop ‘isoelastic’ implant.
Holes: drilling the hole produce Stress riser . but with screw it weakens it much less . Materials:
The ideal material would be : Insoluble,Strong, toxic, carcinogenic , non-irritant.
1. Metals
2. Plastic: High density plyethylene [HPD]
3. ceramics
Fixation:
Bone turn over regularly [ so after a year the implant is attached to a different bone]
leading to :
1. Loosening 2. Wear particles.
3. Foerign body reaction
The implants are Fixed to the skeleton in 4 ways:
1. Tight fit.
2. Mechanically with screws.
3. Bone cement.
4. Bone ingrowth.
3 Orthopedic Note Introduction:
Orthotic:
A device applied directly and externally to the patient’s body [normal or diseased] for support.
Like brace or splint while prosthesis is a device to replace an amputated part of the body.
• used to control motion & function of body segments : CAN reconstruction , Fixation of the spine to support the fixation or prevent stiffness to preserve the functionality by placing a functional brace providing movement and stability [ex: knee in cemen]
• Compensate for a disorder & reduce handicap for biomechanical (& psychological) reasons. (ACL):
• Preserve good range of motion.
• Prevent later deformity while the nerve regenerate.
• Orthoses rely on 3 point fixation .
• Named according to the joints over which they pass (eg. Knee Ankle Foot Orthotses) depend upon the joint it crossover.
Materials used:
Cloth material
Fiproplast material.
Types:
Thermoplastic : if you want made a custom brace [modeling]
Thermoforming plastics - soften when reheated & rigid when cooled
Thermosetting:
Thermosetting plastics - mix liquid + catalysts to form model . it going to be hard all the time no matter heat or cold.
TREATMENT OBJECTIVES:
FUNCTIONAL + BIOMECHANICAL
• To rest a joint or fracture in a chosen position.
• To correct, prevent or support a fixed deformity. [In case of wrist drop .. use splint]
• Control ROM of joints and direction during activity. Mostly knee or elbow to Lock the joint
4 Orthopedic Note ORTHOTIC PRESCRIPTION:
a). Extent : Knee-ankle-foot orthoses etc b). Control : Free knee, Lock knee etc.
COMMON ORTHOTICS:
1. INSOLES:
Panter fasciitis or flat foot 2. ORTHOPEDIC SHOES.
3. THORACO-LUMBAR-SACRAL-HIP-KNEE-ANKLE-FOOT ORTHOSES.
4. UNILATERAL HIP ABDUCTION ORTHOSES.
5. LUMBOSACRAL SUPPORT WITH THORACIC EXTENSION.
6. LUMBAR ORTHOSES (BOSTON BRACE).
7. THE HALO-SPINAL IMMOBILIZATION SYSTEM.
8. MCP ORTHOSES.
9. RADIAL PALSY SPLINT.DYNAMIC ELBOW BRACE
5 Orthopedic Note Orthopaedic Implants:
Screws:
cortical screws
cancellous screws
locking screws Plates
Concave plates
placing a concave bend on a plate is useful in transverse fractures to ensure compressive forces occur on both the far and near cortices of the fracture
Compression plates:
compression plates work by placing a cortical screw eccentrically into an oval hole in the plate.
Locking plates
o advantages of locking plates
locked plate/screw constructs compared to non-locked plate/screw constructs result in less angulation in comminuted metaphyseal fractures
o indications for locking plate technology
indirect fracture reduction
diaphyseal/metaphyseal fractures in osteoporotic bone
bridging severely comminuted fractures
plating of fractures where anatomical constraints prevent plating on the tension side of the bone (e.g. short segment fixation).
o locking plate screw biomechanics
bicortical locking screws have significantly more resistance to all applied forces, with resistance to torsion increased the most (versus unicortical)
unicortical locking screws have less torsion fixation strength than non-locking bicortical constructs
o percutaneous locking plates: application has less soft-tissue stripping but higher chance malunion
o hybrid locked plates: utilize locking and nonlocking screws in order to assist with fracture reduction (nonlocking screws) as well as provide a fixed angle construct (locking screws).
o locking plate construct stability increases with:
bicortical locking screws
increased number of screws
screw divergence from screw hole < 5 degrees
longer plate
o Bridging plates
distal-femoral-plate
6 Orthopedic Note
provides relative stability, relative length and alignment
preserves the blood supply to the fracture fragments as the fracture site is undisturbed during the operative procedure
this theoretically improves secondary bone healing
allows some motion at fracture site; relative stability leads to callus formation
Intramedullary nails
Overview
o a load-sharing device
Material Properties o stiffness
torsional rigidity
defined as amount of torque needed to produce torsional (rotational) defomation
depends on
shear modulus
polar moment of inertia
increased by reaming
decreased by slotting of nail
bending rigidity
depends on
material properties
Young modulus of elasticity of material
structural properties
area moment of inertia
length
Radius of curvature
o intramedullary nail radius of curvature is greater (straighter) than the radius of curvature of the femur
Interlocking
o dynamic locking-->axially and rotationally stable fractures o static locking-->axially and rotationally unstable fractures o secondary dynamization for nonunion
remove proximal interlocking screw or move proximal interlocking screw from the static to dynamic slot
7 Orthopedic Note External fixators
Factors that increase stability of conventional external fixators o contact of ends of fracture (most important)
o larger diameter pins (second most important) o additional pins
o decreased bone to rod distance o pins in different planes
o increasing size or stacking rods o rods in different planes
o increased spacing between pins
Factors that increase stability of circular (Ilizarov) external fixators o larger diameter wires
o decreased ring diameter o olive wires
o extra wires
o wires cross perpendicular to each other o increased wire tension
o placement of two central rings close to fracture o increased number of rings
Total Hip Implants
Material Properties
o rigidity depends on length and radius of femoral stem
Biomechanics
o place femoral component in neutral or slight valgus to reduce moment arm and stress on cement
o increasing femoral offset does the following
advantages
moves abductor moment away from center of rotation
increase abductor moment arm
reduces abductor force required for normal gait
disadvantages
increased strain on implant
increases strain on medial cement mantle
8 Orthopedic Note
PROSTHESIS :
Are functional , cosmetic orboth replacements of the missing parts of the limbs.
ELEMENTS OF A PROSTHESIS:
1. Socket
• transmits forces between the stump[is the part remnant of the amputated part-> and most be computable with it] & the prosthesis in all planes
• may be proximal, distal or total bearing 2. Means of Suspension
• suction socket : it has to be a regular smooth stamp.
• suspension belts
• elastic stocking : if there is an irregularity of the stamp.
9 Orthopedic Note
AMPUTATION
DEFINITION:
Amputation is a removal of a whole or part of a limb.