Polymers are widely used in orthopedic application

2.  An orthopedic implant is a medical device manufactured to
replace a missing joint or bone or to support a damaged bone.
 Internal fixation is an operation in orthopedics that involves the
surgical implementation of implants for the purpose of repairing
a bone.
 Among the most common types of medical implants are the
pins, rods, screws and plates used to anchor fractured bones
while they heal.

3. The material used in orthopedic implants must
be biocompatible to avoid rejection by the body.
Other risks associated with orthopedic implants
include implants coming loose or breaking in the
bone causing painful inflammation and infection to
surrounding tissue.

4. Bone is anisotropic - its modulus is dependent upon
the direction of loading.
Bone is weakest in shear, then tension, then
compression.
Bone is viscoelastic: its force-deformation
characteristics are dependent upon the rate of
loading.
BONE
PROPERTIES
Density – 2.3g/cm3
Tensile Strength – 3-20MPa
Compressive Strength –
15,000 psi
Shear Strength – 4,000 psi
Young’s Modulus – 10-40
MPa

5. ORTHOPEDIC TERMS
Osteoinductive – Characteristic in materials that promote
new bone growth.
Bioresorbable – The ability of a material to
be entirely adsorbed by the body.
Osteoconductive – The property of a
material that allows for the possible
integration of new bone with the host bone.
Trochanter
The second segment of the leg, after the coxa and
before the femur

6. MATERIAL USED
Composite Metal :rough& polished
Polymer
Ceramics

7. An orthopedic hip implant, exhibiting the use of all
three classes of biomaterials: metals, ceramics and
polymers.
 In this case, the stem, which is implanted in the
femur, is made with a metallic biomaterial.
 The implant may be coated with a ceramic to
improve attachment to the bone, or a polymeric
cement.
At the top of the hip stem is a ball (metal or
ceramic) that works in conjunction with the
corresponding socket to facilitate motion in the
joint.
 The corresponding inner socket is made of either
a polymer (for a metallic ball) or ceramic (for a
ceramic ball) and attached to the pelvis by a
metallic socket.

8. VARIOUS fIxATION METHODS
(a) direct interference or (passive)
noninterference fit;
(b) mechanical fixation using
screws, bolts, nuts, wires, etc.;
(c) bone cement;
(d) porous in growth (biological) fixation;
(e) direct chemical bonding
using adhesives or after coating
with direct bonding material layer;
(f) bone cement with resorbable particles;
(g) porous in growth controlled by using
electrical or electromagnetic stimulation

9. BONE CEMENT
Used to fill gaps between bone and implant
•PMMA homopolymer
•MMA/styrene copolymer
•MMA/methyl acrylate copolymer
Poly methylmethacrylate (PMMA) bone cement:
made from methylmethacrylate, poly methylmethacrylate, esters of
meth acrylic acid, or copolymers containing poly
methylmethacrylate and polystyrene
Stable interface between metal and bone

10. COMPOSITION Of A METHACRyLIC CEMENT

11. PROPERTIES OF BONE CEMENT
Bone cement is supplied as two separate components, a polymer powder
and a monomer, which is a colourless and inflammable liquid.
The powder consists of a spherical polymer, an initiator(dibenzoyl
peroxide), a radio pacifier (zirconium oxide or Barium sulphate) and often an
antibiotic.
As the powdered polymer and liquid monomer are mixed, a viscous dough
is formed. Free radicals initiate the polymerization
This process is exothermic, with a maximum in vivo temperature of 40° to
47°C and this thermal energy is dissipated into the circulating blood, the
prosthesis and the surrounding tissue 18 as the cement cures
The chemical composition, the powder to liquid ratio and the cement
temperature in turn determine the viscosity. There are high viscosity and low
viscosity cement types.
High viscosity bone cements have a short wetting phase and a longer
working phase.
Low viscosity cements have a longer wetting phase and a shorter
working phase.

12. LIMITATIONS
Inherently weak
Stronger in compression than tension
Weakest in shear
Exothermic reaction
May lead to bone necrosis
By handling improperly or less than
optimally
Weaker
Extra care should be taken to
Keep debris out of the cement mantle (e.g.,
blood, fat)
Make uniform cement mantle of several mm
Minimize voids in the cement : mixing
technique
Pressurize

13. KNEE AND ITS INjURIES

14. JOINT REPLACEMENTS
 The hip and shoulder joints have a ball and socket articulation,
while other joints such as the knee and elbow have a hinge-type
articulation
 They all possess to opposing smooth cartilaginous articular
surfaces that are lubricated by viscous synovial fluid.
 This fluid is made up of polysaccharides that adhere to the
cartilage and upon loading can be permeated out onto to the
surface to reduce friction.
 The cartilage is not vascularized , and nutrition of the tissues
appears to be a diffusional process.
 The articulation of the joints is stabilized by the body s
coordination of the ligaments, tendons, and muscles.

15. Most femoral head replacements are made with installation of an acetabular
cup. This is called total hip joint replacement (arthroplasty).
The diseased femoral part head is cut off, and the medullary canal of the femur is
drilled and reamed to prepare it for the stem of the prosthesis.
The cartilage of the acetabulam is also reamed. The PMMA bone cement is
prepared from polymer powder and monomer liquid.
It is packed into the medullary canal of the femur and the femoral stem is inserted.
The acetabular component is similarly cemented.
The alignment and articulation of the artificial ball- and-socket joint are then
verified.
UHMWPE and cross linked UHMWPE for the cup and stainless steel and Ti-based
alloys used for femoral head and stem.

16. KNEE JOINT REPLACEMENTS
 The development and acceptance of knee joint prosthesis have been
slower than that of the hip joint due to the knees more complicated
geometry and biomechanics of movement, and lesser stability in
comparison with the hip.
 It can be classified into hinged and non hinged type and it is further
divided into uni – and biocompartmental.
ANATOMy Of ThE KNEE
Made up of 3 bones
•Femur (thigh bone)
•Tibia (lower leg bone)
•Patella (kneecap)

17. CAuSES Of KNEE PAIN
•Osteoarthritis (wear and tear)
•Rheumatoid arthritis
•Post-traumatic arthritis caused by:
•Fractures
•Ligament injuries
•Meniscus tears
GOALS Of TOTAL JOINT REPLACEMENT
ARE TO hELP:
Relieve pain
Restore motion
Improve function
Improve fitness and health
Restore quality of life

18. TOTAL KNEE REPLACEMENT
•Partial knee replacement
(unicompartmental)
– Replacement of one or two parts of knee
instead of total.
– Retain more of patient natural knee.
• Total knee replacement
– Resurfaces the bones (tibia and femur)
with an implant made of metal and
plastic parts.
– Medical-grade plastic spacer providing
a smooth surface as cartilage
Femoral- replaces arthritic portion of thigh
bone
Tibial- replaces arthritic portion of shin
bone
Tibial insert- replaces cartilage and acts as
shock absorber
Patella- replaces knee cap

19. Two major types of total knee replacement systems:
Fixed Bearing- does not allow full range of motion
Rotating Platform Bearing- closely simulates the
action of the normal knee joint
BENEfITS Of fIxEd BEARING KNEE JOINT REPLACEMENTS
Provides pain relief.
Restores the motion of your knee.
Improves quality of life.
Good results in appropriate patients
ROTATING PLATfORM BEARING
Provides pain relief.
Restores the motion of your knee.
Rotation similar to a normal knee.
Reduces potential of early wear and
loosening.
Improves quality of life.

20. KNEE REPLACEMENT PROCEduRE

21. hIP JOINTS
The hip is one of the body's largest
joints. It is a ball-and-socket joint.
The socket is formed by the
acetabulum, which is part of the large
pelvis bone.
 The ball is the femoral head, which
is the upper end of the femur
(thighbone).
The bone surfaces of the ball and
socket are covered with articular
cartilage, a smooth tissue that cushions
the ends of the bones and enables
them to move easily.

22. hIP JOINTS
 A joint is formed by the
ends of 2 or more bones.
The hip must bear the full
force of your weight and
consists of two main
parts:
 A ball (femoral head)
at the top of your thigh
bone (femur)
 A rounded socket
(acetabulum) in your
pelvis

23. CAuSES Of hIP JOINTS
One of the most common causes of
joint pain is arthritis. The most
common types of arthritis are:
Osteoarthritis (OA)
Rheumatoid Arthritis (RA)
Post-traumatic Arthritis
Avascular Necrosis
Osteoarthritis. This is an age-related "wear and tear" type of arthritis. It usually
occurs in people more than50 year old . The cartilage cushioning the bones of the
hip wears away. The bones then rub against each other, causing hip pain and
stiffness. Osteoarthritis may also be caused or accelerated by subtle irregularities
in how the hip developed in childhood.

24. Rheumatoid arthritis. This is an autoimmune disease in which the synovial
membrane becomes inflamed and thickened. This chronic inflammation can
damage the cartilage, leading to pain and stiffness. Rheumatoid arthritis is the
most common type of a group of disorders termed "inflammatory arthritis
Avascular necrosis. An injury to the hip, such as a dislocation or
fracture, may limit the blood supply to the femoral head. This is called
avascular necrosis. The lack of blood may cause the surface of the
bone to collapse, and arthritis will result. Some diseases can also
cause avascular necrosis.
Post-traumatic arthritis. This can follow a serious hip injury or fracture. The
cartilage may become damaged and lead to hip pain and stiffness over
time.

25. TOTAL hIP REPLACEMENTS
Hip replacement is a surgical procedure in which the hip joint is replaced
by a prosthetic implant. Using metal alloys, high-grade plastics, and
polymeric materials, orthopaedic surgeons can replace a painful,
dysfunctional joint with a highly functional, long-lasting prosthesis.
PROCEduRE
The surgical procedure takes a few hours. Your orthopaedic surgeon will remove the
damaged cartilage and bone and then position new metal, plastic, or ceramic implants to
restore the alignment and function of your hip.

26. hIP IMPLANTS
Acetabular shell Acetabular shell
Plastic insert
Ceramic
insert
Metal
femoral
stem
Ceramic
femoral
stem
Femoral
stem

27. Benefits of hip implants
Reduced hip pain.
Increased mobility and movement.
Correction of deformity.
Equalization of leg length (not guaranteed).
Increased leg strength.
Improved quality of life, ability to return to normal
activities.
Enables you to sleep without pain.

28. SPINE
Each vertebra has two sets of facet joints. These spinal joints are called
facet, apophyseal, or zygapophyseal joints .
this joint are gliding joints and link vertebrae together. Facet joints are
synovial joints surrounded by a capsule of collagenous tissue .
the surface of synovial joints are coated with cartilage allowing joints for
smooth motion. These joints allow flexion (bend forward) , extension (bend
backward) and rotating or twisting motion. The spinal discs are located
between pairs of vertebrae and it act as a shock absorbers and allow
deformation of the spine.

29. normal function of the
spine
 Protect spinal cord and nerves
 Support the body weight and
external load
 Stability
 Allow motion of the body for various
activities
 Flexibility

Cervical (7)
Thoracic (12)
Lumbar (5)
Sacral
(5)-
fused

30. SPINAL INJURIES
The nucleus pulposus is made of a gel like material mostly composed of
collagen fibers, proteins and water makes up 90 % of the disc weight at birth
but decreases to 70 % by age 50. excess disc bulging or complete herniation
may takes place by injury or aging, allowing the disc materials to escape the
disc. This will may compress the nerves or spinal cord, causing pain and the
blood supply to the disc decreases ; some disc may degenerate. The disc
begins to lose water and shrinks . The range of motion and shock-absorbing
ability of the spine are decreased .this may result in damage to the nerve and
vertebrae.

31. fleXion inJuries
•Stable Injury
•Affects Cervical, dorsal and Lumbar
spine
•Wedge -Superior Anterior of vertebra
•Spinal cord injury unlikely
hYpereXtension
•Stable injury
•Affects mainly cervical spine
•Anterior Longitudinal Ligament damage ?
Whiplash injury
• possibly rupture of intervertebral disc may
cause cord compression

32. compression inJurY
•Stable injury
•Affects cervical or lumbar spine
•Retro pulsed bony fragment may
compress the cord
shearing inJurY
Shearing = Tearing
Usually with rotation
Unstable
Affects any segment of the spine
Leads to Dislocation or Dislocation
Spinal cord injury is common

33. spinal implant materials
 316L Stainless steel:
 Biocompatible
 Strong and stiff
 Poor imaging compatibility: artifact to CT and MRI
 Titanium Alloy (Ti6Al4V ELI):
 Biocompatible
 No artifacts during CT and MRI
 Excellent fatigue strength, high strength, high elasticity
 High resistance to fretting corrosion and wear (surface
treatments)

34. spinal instrumentation
 Goals of Spinal Instrumentation:
 Correction of deformities or misaligned segments;
 Enhancement of solid fusion;
 Maintain anatomic alignment until a solid fusion takes place; and
 Allow early mobilization of patients
 by providing an immediate stability
cervical spine instrumentation

35. thoracolumBar spine
instrumentation
Z-plate (Danek) Kaneda (AcroMed)

36. spinal fiXation device

37. factors in spinal instrumentation
 Materials:
 Bio-compatibility and Imaging compatibility
 Stiffness (or elasticity) and strength
 Corrosion
 Implant Strength:
 Component (screw, rod, plate, wire, etc.) strength
 Metal-metal interface strength
 Construct strength
 Bone-metal interface strength: Bone–wire, -hook, and -screws
 Construct Stability:
 Segmental stiffness or flexibility
 Profile:
 Ease of Use:

38. anKle Joint replacements
 The ankle joint is made up of three bones: the lower end of
the tibia(shinbone), the fibula (the small bone of the lower leg), and
the talus, the bone that fits into the socket formed by the tibia and
fibula. The talus sits on top of the calcaneus (the heelbone). The talus
moves mainly in one direction. It works like a hinge to allow your foot to
move up and down
The large Achilles tendon at the back of the ankle is
the most powerful tendon in the foot. It connects the
calf muscles to the heelbone and gives the foot the
power for walking, running, and jumping.

39. Certain movements may cause a grinding or catching
sensation as the arthritic bone surfaces move against one
another. The ankle joint may swell. This swelling cause
problems in the ankles
The benefit of an artificial joint is to ease the symptoms
of ankle osteoarthritis
surgical procedure
The Artificial Ankle
Each artificial ankle prosthesis is made of two parts:
The tibial component is the part of the artificial joint
that replaces the socket portion of the ankle (the top
section).
The talus component replaces the top of the talus.

40. Ankle Joint ReplAcement
The tibial component is usually made up of two parts: a
flat metal piece called a metal tray that is attached directly
to the tibia bone, and a plastic cup that fits onto the metal
piece, forming a socket for the artificial ankle joint. The
talus component is made of metal and fits into the socket
of the tibial component.
The main advantage of an ankle transplant replacement is
the potential for replacement of the entire ankle joint with
viable living cartilage cells.

41. ShouldeR Joint ReplAcementS
 The major shoulder joint motion originates from the ball-and-socket
articulation of the glenohumeral joint.
 The hemispherical , incongruent joint provides the largest motion in
the body

42. shoulder is made up of three bones: your upper arm bone
(humerus), your shoulder blade (scapula), and your collarbone
(clavicle). The shoulder is a ball-and-socket joint: The ball, or head,
of your upper arm bone fits into a shallow socket in your shoulder
blade. This socket is called the glenoid.
the surfaces of the bones where they touch are covered with articular cartilage, a
smooth substance that protects the bones and enables them to move easily. A
thin, smooth tissue called synovial membrane covers all remaining surfaces
inside the shoulder joint. In a healthy shoulder, this membrane makes a small
amount of fluid that lubricates the cartilage and eliminates almost any friction in
your shoulder.
The muscles and tendons that surround
the shoulder provide stability and support.

43. SuRgicAl pRoceduRe
The surgeon begins by separating the deltoid and pectoral muscles,
accessing the shoulder in a largely nerve-free area to minimize nerve
damage. The shoulder is covered by the rotator cuff, which must be
opened by cutting one of the anterior (front) rotator cuff muscles. This
“opens the door,” allowing the surgeon to view and manipulate the
arthritic parts of the shoulder ball and socket.
After the arthritic sections have been removed, the surgeon inserts the
implant socket, ball, and stem components, closes and stitches the
rotator cuff muscle, and stitches and cleans the incision, after which a
bandage is applied as a temporary covering.

44. FRActuRe plAteS
A bone fracture is a medical condition in which there is a break in
the continuity of the bone. A bone fracture can be the result of high
force impact or stress, or trivial injury as a result of certain medical
conditions that weaken the bones, such as osteoporosis, bone
cancer, or osteogenesis imperfecta, where the fracture is then
properly termed a pathologic fracture.

45. Bone plates are surgical tools, which are used to assist in the
healing of broken and fractured bones
Currently osteotemy equipment is made primarily of titanium
and stainless steel. The broken bones are first surgically reset into
their proper position. Then a plate is screwed onto the broken
bones to hold them in place, while the bone heals back together.
Bone plates can also be fabricated using shape
memory alloys, in particular nickel titanium
Traumatic fracture - This is a fracture due to
sustained trauma. e.g.- Fractures caused by a fall,
road traffic accident, fight etc.
Pathological fracture - A fracture through a bone
which has been made weak by some underlying
disease is called pathological fracture. e.g.- a
fracture through a bone weakened by metastasis.
Osteoporosis is the most common cause of
pathological fracture.

46. tYpeS oF FRActuReS
 Type I Fractures
These fractures break through the bone at the growth plate, separating
the bone end from the bone shaft and completely disrupting the growth
plate.
 Type II Fractures
These fractures break through part of the bone at the growth plate and
crack through the bone shaft as well.
 Type III Fractures
These fractures cross through a portion of the growth plate and break
off a piece of the bone end.
 Type IV Fractures
These fractures break through the bone shaft, the growth plate, and the
end of the bone.
 Type V Fractures
These fractures occur due to a crushing injury to the growth plate from
a compression force. They are rare fractures.

47. tYpe oF plAteS
Plates are some of the most common general purpose fixation devices.
They contain holes for screws and pins that are used to fix the plate to intact
bone and to fractures
For simple fractures of long bones, screws are often used to reduce the
fractures and apply compression to the fracture site (lag screws). These
screws, however, withstand external compressive and bending forces .
Plates that span the fracture site and reduced the fracture are called
neutralization plates .since they resist or neutralize external forces at the
fracture site protecting the lag screw fixation.

48. A compression plate is most commonly used with diaphyseal fractures of
the long bones. The geometry of its screw holes allows compression of a
fracture spanned by the plate as the screw head contacts the plate during
insertion
Reconstruction plates are flexible and can be cut to length to fit irregular
surfaces. They are used primarily for fractures of the pelvis
Blade plates are used for fractures of the condylar regions of the long bones. They
are simpler alternative devices that can be used in place of a plate with a separate
condylar screw.
The LISS (Less Invasive Stabilization System) plate is a recently introduced type
of plate that is a modification of the standard compression plate used for long bone
fracture

49. SCREWS

50. LAG SCREW FIXATION
Screw compresses both sides of fix together
•Best form of compression
•Poor shear, bending, and rotational force ,resistance
Partially-threaded screw (lag by design)
Fully-threaded screw (lag by technique)
• Step One: Gliding hole = drill outer thread diameter of screw &
perpendicular to fix
• Step Two: Pilot hole= Guide sleeve in gliding hole & drill far
cortex = to the core diameter of the screw

51. Step Three: counter sink near cortex so screw head will sit flush
Step Four: screw inserted and glides through the near cortex &
engages the far cortex which compresses the fix when the screw
head engages the near cortex

52. thAnk You