Lecture 11a

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Osteoarthritis
Osteoarthritis (OA)
• OA is the most common form of
arthritis and the most common
joint disease
• Over 10 million Americans suffer
from OA of the knee alone
• Most of the people who have OA
are older than age 45, and women
are more commonly affected than
men.
• OA most often occurs at the ends
of the fingers, thumbs, neck,
lower back, knees, and hips.
OA
OA is a disease of
joints that affects all of
the weight-bearing
components of the
joint:
•Articular
cartilage
•Menisci
•Bone
OA
Nodal osteoarthritis
Note bony
enlargement of distal
and proximal
interphalangeal
joints (Heberden's
nodes and
Bouchard's nodes,
respectively).
OA – Risk Factors
Age
•
Age is the strongest risk factor for OA. Although OA can
start in young adulthood, if you are over 45 years old, you
are at higher risk.
Female gender
•
In general, arthritis occurs more frequently in women than
in men. Before age 45, OA occurs more frequently in men;
after age 45, OA is more common in women. OA of the
hand is particularly common among women.
Joint alignment
•
People with joints that move or fit together incorrectly, such
as bow legs, a dislocated hip, or double-jointedness, are
more likely to develop OA in those joints.
OA – Risk Factors
Hereditary gene defect
•
A defect in one of the genes responsible for the cartilage
component collagen can cause deterioration of cartilage.
Joint injury or overuse caused by physical labor or
sports
•
Traumatic injury (ex. Ligament or meniscal tears) to the
knee or hip increases your risk for developing OA in these
joints. Joints that are used repeatedly in certain jobs may be
more likely to develop OA because of injury or overuse.
Obesity
•
Being overweight during midlife or the later years is among
the strongest risk factors for OA of the knee.
OA – Symptoms
• OA usually occurs slowly It may be many years before
the damage to the joint
becomes noticeable
• Only a third of people
whose X-rays show OA
report pain or other
symptoms:
– Steady or intermittent pain in a joint
– Stiffness that tends to follow periods of inactivity, such as sleep
or sitting
– Swelling or tenderness in one or more joints [not necessarily
occurring on both sides of the body at the same time]
– Crunching feeling or sound of bone rubbing on bone (called
crepitus) when the joint is used
Osteoarthritis (OA) - Definition
Osteoarthritis may result from wear and tear
on the joint
•The normal
cartilage lining
is gradually
worn away and
the underlying
bone is
exposed.
Osteoarthritis (OA) - Definition
•The repair mechanisms of tissue absorption and
synthesis get out of balance and result in
osteophyte formation (bone spurs) and bone cysts
A case of the, “Which
came first? The
chicken or the egg?”
OA – Articular Cartilage
Articular cartilage is the main tissue affected
OA results in:
•Increased tissue swelling
•Change in color
•Cartilage fibrillation
•Cartilage erosion down to subchondral bone
OA – Articular Cartilage
OA – Articular Cartilage
A) Normal articular
cartilage from 21-year old
adult (3000X)
B) Osteoarthritic cartilage
(3000X)
The surface changes
alter the distribution
of biomechanical
forces further
triggering active
changes by the
tissue
OA – Articular Cartilage
The cartilage damage causes chondrocyte cloning in an
attempt to restore articular surface (Normal adult
chondrocytes are fully differentiated and do not proliferate)
(A) Normal articular cartilage (B) Osteoarthritic cartilage
OA – Articular Cartilage
Unfortunately, the newly dividing cells do not
differentiate fully and cannot effectively synthesize the
elements needed for matrix maintenance
This results in a net loss of matrix components
•Collagen content stays constant but fibrils are thinner
and more disorganized
- Decreased tensile strength
OA – Articular Cartilage
•Proteoglycan loss
results in an
inability to hold on
to water content:
- Decreased
resistance to
compression –
especially with
repeated stress
OA vs. Aging
Unlike aging, OA is progressive and a significantly
more active process
OA – Overall Changes
Osteoarthritis with lateral osteophyte, loss of articular cartilage and
some subchondral bony sclerosis- X-ray shows loss of joint space
OA – Radiographic Diagnosis
Asymmetrical joint space narrowing from loss of
articular cartilage
The medial (inside) part of the knee is most commonly affected by osteoarthritis.
OA – Radiographic Diagnosis
•Asymmetrical
joint space
narrowing
•Periarticular
sclerosis
•Osteophytes
•Sub-chrondral
bone cysts
OA – Arthroscopic Diagnosis
Arthroscopy allows earlier
diagnosis by demonstrating the
more subtle cartilage changes
that are not visible on x-ray
Normal Articular Cartilage
Ostearthritic degenerated cartilage
with exposed subchondral bone
OA – Arthroscopic Treatment
•In addition to being the most accurate way of determining how
advanced the osteoarthritis is:
•Arthroscopy also allows the surgeon to debride the knee joint
•Debridement essentially consists of cleaning out the joint of all debris and
loose fragments. During the debridment any loose fragments of cartilage
are removed and the knee is washed with a saline solution.
•The areas of the knee joint which are badly worn may be roughened with
a burr to promote the growth of new cartilage - a fibrocartilage material
that is similar scar tissue.
•Debridement of the knee using the arthroscope is not 100% successful. If
successful, it usually affords temporary relief of symptoms for somewhere
between 6 months - 2 years.
•Arthroscopy also allows access for surgical treatment of articular
cartilage: graft-transplantation, micro-fracture techniques, subchondral drilling
OA – Disease Management
•OA is a condition which progresses slowly over a
period of many years and cannot be cured
•Treatment is directed at decreasing the symptoms of
the condition, and slowing the progress of the
condition
•Functional treatment goals:
•Limit pain
•Increase range of motion
•Increase muscle strength
OA – Non-operative Treatments
•Pain medications
•Physical therapy
•Walking aids
•Shock absorption
•Re-alignment through
orthotics
•Limit strain to affected
areas
Proximal Tibial Osteotomy
•Osteoarthritis usually
affects the inside half
(medial compartment) of
the knee more often than
the outside (lateral
compartment).
•This can lead to the lower
extremity becoming
slightly bowlegged, or in
medical terms, a genu
varum deformity
Proximal Tibial Osteotomy
•The result is that the weight bearing line of the lower
extremity moves more medially (towards the medial
compartment of the knee).
•The end result is that there is more pressure on the medial
joint surfaces, which leads to more pain and faster
degeneration.
•In some cases, re-aligning the angles in the lower extremity
can result in shifting the weight-bearing line to the lateral
compartment of the knee. This, presumably, places the
majority of the weight-bearing force into a healthier
compartment. The result is to reduce the pain and delay the
progression of the degeneration of the medial compartment.
Proximal Tibial Osteotomy
•In the procedure to realign the
angles, a wedge of bone is
removed from the lateral side
of the upper tibia.
•A staple or plate and screws
are used to hold the bone in
place until it heals.
•This converts the extremity
from being bow-legged to
knock-kneed.
•The Proximal Tibial Osteotomy buys some time before ultimately
needing to perform a total knee replacement. The operation
probably lasts for 5-7 years if successful.
Total Knee Replacement
The ultimate solution for osteoarthritis of the knee is to
replace the joint surfaces with an artificial knee joint:
•Usually only considered in people over the age of 60
•Artificial knee joints last about 12 years in an elderly population
•Not recommended in younger patients because:
•The younger the patient, the more likely the artificial joint will fail
•Replacing the knee the second and third time is much harder and much less
likely to succeed.
•Younger patients are more active and place more stress on the artificial
joint, that can lead to loosening and failure earlier
•Younger patients are also more likely to outlive their artificial joint, and
will almost surely require a revision at some point down the road.
•Younger patients sometimes require the surgery (simply because
no other acceptable solution is available to treat their condition)
Total Knee Replacement
•The ends of the femur, tibia, and patella are shaped to accept
the artificial surfaces.
•The end result is that all moving surfaces of the knee are
metal against plastic
Total Knee Replacement
Total Knee Replacement
Total Knee Replacement
Total Knee Replacement
Total Knee Replacement
Total Knee Replacement
Total Knee Replacement
Total Knee Replacement
Total Knee Replacement
Photographs of total knee
components on model
bone
Total Knee Replacement
Unicompartmental Knee Replacement
•When only one part of the knee joint is arthritic, it may be
possible to replace just this part of the joint
•The procedure is similar to a total knee replacement, but only
one side of the joint is resurfaced
•A metal component is fit onto the femur and a plastic bearing
is inserted either directly onto the tibia or onto a metal tray
which has been fit onto the tibia
•Recovery time is generally slightly shorter following this
kind of surgery.
…The End
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