hard tissue replacement-orthopedics

8/3/2019 Hard Tissue Replacement-Orthopedics

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Hard Tissues ReplacementImplants

1.Orthopedic implants

2.Dental implants

Orthopedic Implants

Hip prosthesis & THR

Hip implants

Shoulder prosthesis

Knee replacement

Vertebral discs

Joint prostheses & Joint repair

Joint replacement Supporting plates, screws,

intramedullary nails for bone fracture

Orthopedics

Orthopedics is the study of the musculoskeletal system

The musculoskeletal system includes

bones, joints, ligaments,tendons, muscles, and nerves.

The Skeletal System

The skeletal system consists of bonesand other structures that make up the joints of the skeleton.

The types of tissue present are bonetissue, cartilage, and fibrous connectivetissue, which forms the ligaments thatconnect bone to bone.

RECALL FUNCTIONS OF THE SKELETON

Provides a framework that supports the body; themuscles that are attached to bones move theskeleton.

Protects some internal organs from mechanicalinjury(For example the rib cage protects the heart and lungs)

Contains and protects the red bone marrow, theprimary hemopoietic (blood-forming) tissue.

RECALL FUNCTIONS OF THE SKELETON

Provides a storage site for excess calcium.

Calcium may be removed from bone tomaintain a normal blood calcium level,which is essential for blood clotting andproper functioning of muscles and nerves.

RECALL TYPES OF BONE TISSUE

The bone cells are called osteocytes,and the matrix of bone is made of calcium salts and collagen.

The calcium salts are calcium carbonate(CaCO3) and calcium phosphate(Ca3(PO4)2), which give bone thestrength required to perform itssupportive and protective functions.

TYPES OF BONE TISSUE

Bone matrix is non-living, but itchanges constantly, with calcium thatis taken from bone into the bloodreplaced by calcium from the diet.

In normal circumstances, the amount of calcium that is removed is replaced by an equal amount of calcium

deposited.

In bone as an organ, two types of

bone tissue are present1. Compact bone - Compact bone is

made of osteons or haversiansystems, microscopic cylinders of bone matrix with osteocytes in

concentric rings around centralhaversian canals.

In the haversian canals are bloodvessels; the osteocytes are in contact

with these blood vessels and withone another through microscopicchannels (canaliculi) in the matrix.

1. Spongy bone - looks like asponge with its visible holesor cavities.

Osteocytes, matrix, and blood

vessels are present but arenot arranged in haversiansystems.

The cavities in spongy boneoften contain red bone

marrow, which produces redblood cells, platelets, and thefive kinds of white blood cells.

CLASSIFICATION OF BONES

1. Long bones —the bones of the arms, legs, hands andfeet. (Radius, Ulna, Femur,Tibia, Fibula)

2. Short bones—the bones of the wrists and ankles.(Carpus, Tarsal, metatorsal,…)

3. Flat bones—the ribs,

shoulder blades, hip bones,and cranial bones. (Scapula,clavicle)

4. Irregular bones—thevertebrae and facial bones.

BONES STRUCTURE

The shaft of a long bone is thediaphysis, and the ends are calledepiphyses.

The diaphysis is made of compactbone and is hollow, forming a canalwithin the shaft. This marrow canal

(or medullary cavity) containsyellow bone marrow, which ismostly adipose tissue.

The epiphyses are made of spongybone covered with a thin layer of

compact bone. Although red bonemarrow is present in the epiphysesof children’s bones, it is largelyreplaced by yellow bone marrow inadult bones.

Regions of bone

1. Compact or Corticalbone

2. Cancellous or trabecularbone

BONES STRUCTURE

Short, flat, and irregular bones are all made of spongybone covered with a thin layer of compact bone.

Red bone marrow is found within the spongy bone. The joint surfaces of bones are covered with articularcartilage, which provides a smooth surface.

Covering the rest of the bone is the periosteum, afibrous connective tissue membrane whose collagenfibers merge with those of the tendons and ligamentsthat are attached to the bone.

The periosteum anchors these structures and containsboth the blood vessels that enter the bone itself andosteoblasts that will become active if the bone isdamaged.

JOINTS

SYNOVIAL JOINT

Synovial joints—alldiarthroses have similarstructure

Articular cartilage—smoothon joint surfaces.

Joint capsule—strong fibrousconnective tissue sheaththat encloses the joint.

Synovial membrane—linesthe joint capsule; secretes

synovial fluid that preventsfriction.

Bursae—sacs of synovialfluid that permit tendons toslide easily across joints.

ARTHRITIS

The term arthritis means ―inflammation of a joint.‖ Of the many types of arthritis, we willconsider

1. Osteoarthritis

2. Rheumatoid arthritis.

OSTEOARTHRITIS

Osteoarthritis is a natural consequence of gettingolder.

In joints that have borne weight for many years,

the articular cartilage is gradually worn away. The once smooth joint surface becomes rough,

the bones then rub against each other and theaffected joint is stiff and painful.

The large, weight-bearing joints (knees, hips,ankles) are most often subjected to this form of arthritis.

Rheumatoid arthritis (RA)

Rheumatoid arthritis (RA) can be a trulycrippling disease that may begin in earlymiddle age or, less commonly, during

adolescence.

It is an autoimmune disease, which meansthat the immune system mistakenly directs its

destructive capability against part of the body.

Exactly what triggers this abnormal response bythe immune system is not known with certainty,but certain bacterial and viral infections havebeen suggested as possibilities.

Rheumatoid arthritis often begins in joints of theextremities, such as those of the fingers.

The autoimmune activity seems to affect thesynovial membrane, and joints become painfuland stiff.

Sometimes the disease progresses to totaldestruction of the synovial membrane andcalcification of the joint. Such a joint is thenfused and has no mobility at all.

Autoimmune damage may also occur in theheart and blood vessels, and those with RAare more prone to heart attacks and strokes

(RA is a systemic, not a localized, disease).

ORTHOPEDIC IMPLANTS

Hard Tissue Replacement

Hip replacement

It replaces the painful arthritic joint

The modular prosthetic hipreplacement system used today hasthree components – the femoralstem, the femoral head, and theacetabulum.

Each component has multiple sizeswhich allow for a custom fit.

Hip replacement…

The components are made of cobalt chrome, stainless steel,Titanium alloys, ceramics andultra high molecular weight

polyethylene.

Cementless and cemented prosthesis systems are

available.

Common Causes of Hip Painand Loss of Hip Mobility

Osteoarthritis

Usually occurs after age 50and often in an individualwith a family history of arthritis.

In this form of the disease,the articular cartilagecushioning the bones of thehip wears away.

The bones then rub againsteach other, causing hip painand stiffness.

Removing the Femoral Head

Once the hip joint isentered, the femoralhead is dislocated fromthe acetabulum.

Then the femoral head isremoved by cuttingthrough the femoral

neck with a power saw.

Reaming the Acetabulum

After the femoral head isremoved, the cartilage isremoved from theacetabulum using a power

drill and a special reamer.

The reamer forms the bonein a hemispherical shape toexactly fit the metal shell of

the acetabular component.

I ti th A t b l

Inserting the AcetabularComponent

A trial component, which isan exact duplicate of thehip prosthesis, is used toensure that the joint will bethe right size and fit for theclient.

Once the right size andshape is determined for the

acetabulum, the acetabularcomponent is inserted intoplace.

Preparing the Femoral Canal

To begin replacing thefemoral head, special raspsare used to shape and scrapeout femur to the exact shapeof the metal stem of thefemoral component.

Once again, a trialcomponent is used to ensurethe correct size and shape.

The surgeon will also test themovement of the hip joint.

Inserting Femoral Stem

Once the size and shapeof the canal exactly fitthe femoral component,the stem is inserted into

the femoral canal.

Attaching the Femoral Head

The metal ball that replacesthe femoral head is

attached to the femoralstem.

The Completed Hip Replacement

• Client now has a newweight bearing surfaceto replace the affectedhip.

• Before the incision isclosed, an x-ray is madeto ensure newprosthesis is in the

correct position.

Treatment by Kinesiologist (Postoperative Exercises)

Regular exercises to restore the normal hipmotion and strength and a gradual return toeveryday activties.

Exercise 20 to 30 minutes a day divided into 3sections.

Increase circulation to the legs and feet toprevent blood clots

Strengthen muscles

Improve hip movement

Video 1

Video 2

Shoulder replacement

The shoulder is made up

of three bones1. clavicle (collarbone)

2. scapula (shoulder blade)

3. humerus (upper arm bone)

As well as associatedmuscles, ligaments andtendons.

The articulations between

the bones of the shouldermake up the shoulder joints.

It is a ball and socket joint

Steps in total shoulder joint replacement1. Made incision in the shoulder and upper arm

2. The head of the humerus is removed with a bone saw

3. The shaft of the humerus is reamed with a bone rasp toready it for the prosthesis

4. After the shoulder joint, or glenoid cavity, is similarlyprepared, bone cement is applied to areas to receiveprostheses.

5. The ball and socket prostheses are put in place, andthe incision is closed.

Types of Shoulder Arthroplasty

There are two major types of artificialshoulder replacements

1. Cemented prosthesis

2. Uncemented prosthesis

A cemented prosthesis is held in placeby a type of epoxy cement (epoxide+ polyamine) that attaches the metalto the bone

An uncemented prosthesis has a finemesh of holes on the surface

Bone grows into the mesh. Over time,this anchors the prosthesis to thebone.

Types of Shoulder Arthroplasty…

And also other two categories of shoulder arthroplasties arethere.

1. Hemiarthroplasty2. Total Shoulder Replacement

Bipolar hemiarthroplasty

The humeral component isinterlocked with a larger metalbacked polyethylene shell thatarticulates with the native glenoid

Hemiarthroplasty

A hemiarthroplasty replaces thehead of the humerus with anintramedullary stemmedimplant.

It consists only the humeralcomponent

This is used when the nativeglenoid surface is in good

condition.

Indications Hemiarthroplasty

Osteonecrosis of the humeralhead without associatedsecondary degenerative arthritis

Head-splitting fractures of theproximal humerus

Certain neoplasms of theproximal humerus

Insufficient glenoid bone stock tosupport a glenoid component

Glenohumeral osteoarthritis withmassive rotator cuff tear.

Total shoulder replacements (TSR)

Total shoulderreplacements (TSR)employ both humeral andglenoid components

They are used in patientswith arthritis where thehumeral head and glenoid

surfaces are damaged.

Design classification of TSR

Non-constrained

Constrained

Semi Constrained

Non-constrained TSR

These prostheses have no physical link betweenthe humeral and glenoid components and rely onthe surrounding musculotendinous cuff forstability.

The components attempt to recreate normalanatomy and relationships.

This minimizes stresses at interfaces and allowsfor early rehabilitation.

The Precise surgical technique is critical forsuccess

The proper tension of capsular, muscular, andtendinous structures needed for stability.

Constrained TSR This is the first generation designs for total

shoulder replacements The humeral and glenoid components are

mechanically coupled around a fixed center of rotation.

These were used in patients with rotator cuff deficiencies and helped prevent superior migrationof the humeral component.

This design causes most forces to be borne by the

prosthesis and interfaces instead of thesurrounding soft tissues, leading to higher ratesfracturing of components and loosening.

Today, this design type is rarely employed.

Semi-constrained

These prostheses are similar to non-constraineddesigns except that the superior glenoidcomponent has a superior extension thatprevents superior migration of the humeralcomponent.

The selection is based on age, lifestyle, and alsothe surgeon's experience.

Knee Replacement

Shaping the Distal Femoral Bone

A special cutting jig is placed onthe end of the femur

This jig is used to make sure thatthe bone is cut in the proper

alignment to the leg's originalangles, even if the arthritis hasmade you bowlegged or knock-kneed.

The jig is used to cut severalpieces of bone from the distalfemur so that the artificial kneecan replace the worn surfaces

with a metal surface.

Knee Replacement

Preparing the Tibial Bone Then the top of the tibia is cut

using another jig that ensuresthe alignment is satisfactory.

Knee Replacement

Preparing the Patella

The undersurface of the

patella is removed.

Knee Replacement

Placing the Femoral Component

The metal femoral component is thenplaced on the femur.

When using an uncemented femoralcomponent, the prosthesis is held onthe end of the bone through a taper onthe end of the bone.

The metal prosthesis is cut so that it

matches the taper almost exactly.

Contd…

Driving the metal component onto the end of the bone holds the component in place byfriction

The stable implant will allow bone tissue togrow into the porous surface, providing long-term stability.

In a cemented femoral component, an epoxycement is used to attach the metal prosthesisto the bone.

Knee Replacement

Knee Replacement…

Placing the Tibial Components

The metal tray that will hold thepolyethylene spacer is attached to thetop of the tibia.

The metal tray is either cemented intoplace, or may be held with screws if the

component is uncemented. The screws are primarily used to hold

the tibial tray in place until the bonegrows into the porous coating. (Thescrews remain in place and are not

removed.) The plastic spacer is then attached to

the metal tray of the tibial component.

If this component wears out while therest of the artificial knee is good, it can

be replaced.

Vertebral discs

Spinal repair

The degeneration of disc leads to a conditioncalled Degenerative Disc Disease.

Majority of patients can be treated withpainkillers, braces, physical therapy, smallpercentage of such patients do not respond tonon-operative treatment and need surgery.

There are two types of surgical option in suchcases

1. Spinal Fusion

2. Disc Replacement

S i l F i

Spinal Fusion

In spinal fusion surgery, the disc(which is a soft material betweentwo vertebrae) is removed and thespace is packed with bone graft.

In due course of time, the bonecreates a solid bony bridge acrossthe two vertebrae.

These grafts will regenerate, growinto the bone, and fuse thevertebrae together.

The bones are held in place with oneor two metal rods held down withhooks and screws, which also helpsto support the fusion of thevertebrae.

Spinal Fusion…

Bone can be taken from elsewhere inyour body or obtained from a bone

bank (a bone graft). The bone is used to make a bridge

between vertebrae that are next toeach other (adjacent).

This bone graft stimulates the growth

of new bone. Man-made (artificial)fusion materials may also be used.

Metal implants can be used to holdthe vertebrae together until new bonegrows between them.

Metal plates can be screwed into thebone, joining adjacent vertebrae.

An entire vertebra can be removed,and the spine then fused.

A spinal disc can be removed and the

adjacent vertebrae fused.

Disc Replacement

Disc replacement surgery

is the most innovativeand modern treatmentthat is now available.

Artificial Disc Replacement (ADR) or Totall ( )

Disc Replacement (TDR)

It is a surgical procedure in whichdegenerated intervertebral discs in thespinal column are replaced with artificialdevices in the lumbar (lower) or cervical(upper) spine.

The procedure is used to treat chronic,severe low back pain and cervical painresulting from degenerative disc disease.

Artificial disc replacement has beendeveloped as an alternative to spinalfusion, with the goal of pain reduction orelimination, while still allowing motion

throughout the spine.

Another possible benefit is theprevention of premature breakdown inadjacent levels of the spine, a potentialrisk in fusion surgeries.

Joint repair, Orthopedic supporting aids,fracture fixation

Bone necrosis

Interfacial failure: Simple motion between implant andcement or cement and bone was initially thought to

contribute to interfacial failure. Particle-induced osteolysis is known as particle disease

Osseointegration: a direct contact between living boneand implant (A structural and functional connectionbetween ordered, living bone and the surface of a load-

carrying implant)

Bone Cements: bone cements are substances used torepair the damaged or diseased areas of bones or to fixa prosthesis in the bones. e.g

polymers of methylmethacrylate (PMMA) (1940)

Acrylate-based plastics

Tetrahydrofurfuryl methacrylate (THFMA)

Tricalcium phosphateurethane dimethacrylate monomer (UDMA)

Tetrahydrofurfuryl methacrylate monomer (THFMA), etc.

hard tissue replacement-orthopedics

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