Total knee arthroplasty by dr..ammar m.sheet

Presented by:
Dr. Ammar Mohammed sheet

In the 1860s, Fergusson reported performing a resection
arthroplasty of the knee for arthritis
Verneuil --- performed the first interposition arthroplasty using joint
capsule.
Other tissues were subsequently tried, including skin, muscle, fascia,
fat, and even pig bladder.
The first artificial implants were tried in the 1940s as molds fitted to the
femoral condyles

Combined femoral and tibial articular surface replacements
appeared in the 1950s as simple hinges.
In 1971, Gunston recognized that the knee does not rotate on a single
axis like a hinge, but the femoral condyles roll and glide on the tibia
with multiple instant centres of rotation .
The total condylar prosthesis was designed by Insall at the
Hospital for Special Surgery in 1973.

Patients with painful, deformed, and unstable knees
secondary to degenerative or inflammatory conditions need
a prosthesis that provides reproducible pain relief and
improvement in function.
The morbidity and complications from the procedure should
be minimal.
The complexities of a normal knee joint, however, are not
reproducible with modern techniques, and patients should
understand that they will not have a normal knee.
The prosthesis should be durable, requiring patients to
undergo only one definitive procedure in their lifetime,
although this may simply be unrealistic in younger patients

Knee Anatomy
Ligaments, Cartilage,Tendons,
Bone
Largest joint in the body
Femur-Tibia-Fibula-Patella
Movement of the knee joint
having 6 degrees of freedom:
3 translations (anterior /posterior ,
medial/ lateral , inferior /superior)
3 rotations (flexion/extension , internal
/ external , abduction/ adduction)

Knee Anatomy (cont,)
Movements of the knee joint are determined by the shape
of the articulating surfaces of the tibia and femur and the
orientation of the 4 major ligaments ACL , PCL and the
medial and lateral collateral ligaments as a 4-bar linkage
system.

Knee flexion/extension involves a combination of rolling and
sliding called femoral rollback, which is an ingenious way of
allowing increased ranges of flexion
Femoral rollback To properly understand different knee prosthetic
designs one must understand the concept of femoral rollback.
Is the posterior transition of the femoral-tibial contact with
progressive flexion
 it reduces bony impingement and allows increase physiologic flexion.
it is controlled by ACL and PCL.
 rollback with a PCL alone exists but it is not as smooth as a rollback with
both an ACL and PCL
in the native knee can occur due to a relatively flat tibia with minimal
congruence with the femoral condyles .

Knee Anatomy (cont,)
. Because of asymmetry between the lateral and medial femoral
condyles , the lateral condyle rolls a greater distance than the
medial condyle during 20 degrees of knee flexion.This causes
coupled external rotation of the tibia, which has been described as
the screw-home mechanism of the knee that locks the knee into
extension.
Movement of the patellofemoral joint can be characterized as
gliding and sliding.

The primary function of the
MCL is to restrain valgus rotation of the knee joint, with
its secondary function being control of external rotation.
LCL restrains varus rotation and resists internal rotation.
The primary function of the
(ACL) is to resist anterior displacement of the tibia on the
femur when the knee is flexed and control the screw-
home mechanism of the tibia in terminal extension of the
knee. A secondary function of the ACL is to resist varus or
valgus rotation of the tibia, especially in the absence of
the collateral ligaments.The ACL also resists internal
rotation of the tibia.

The main function of the
(PCL) is to allow femoral rollback in flexion and resist
posterior translation of the tibia relative to the femur. The
PCL also controls external rotation of the tibia with
increasing knee flexion.
Retention of the PCL in total knee
replacement has been shown
biomechanically to provide
normal kinematic rollback of the
femur on the tibia.
This also is important for improving
the lever arm of the quadriceps
mechanism with flexion of the knee

Designs include
 Unconstrained
o1. posterior- cruciate retaining
o2. posterior- cruciate substituting
(posterior stabilized)
 Constrained
3. non hinged
4. constrained-hinged

1. Unconstrained Posterior Cruciate Retaining
(PCR)
•. Most common prosthesis used today
•Relies on native PCL to provide stability in flexion
 by keeping PCL some degree of femoral rollback is
allowed that allows improved flexion
however because ACL is sacrificed,
rollback is not anatomic, and has a
component of both roll and slide
which can accelerate wear

In addition, to allow rollback, you need a flat
and less congruent tibial component.
This leads to increased contact stress and
accelerated wear
 modern PCL retaining implants favor
a more congruent prosthesis that obtains
extra flexion by moving the center of
rotation further posterior than it is in
an anatomic knee.
Disadvantages
loss of native PCL will lead to flexion instability and failure
1. Unconstrained Posterior Cruciate Retaining
(PCR) - (cont.)

2. Unconstrained Posterior Cruciate Substituting
(PCS)
A posterior cruciate substituting implant
uses a tibial post and a femoral cam to substitute for the
function of the PCL and create a mechanical rollback
phenomenon.
at a designated flexion point, the tibial post engages on
the femoral cam and forces mechanical rollback, thus
improving flexion.

by using mechanical rollback, you can use a more
congruent articular surface, and thus decrease contact
stress
of note, the tibial post is not wide enough to provide any
varus and valgus stability
•Disadvantages
cam jump - if flexion gap is loose or knee hyperextends
the knee can jump over post and dislocate
oreduction requires sedation
oavoid in knee with
anticipated flexion > 130°
2. Unconstrained Posterior Cruciate Substituting
(PCS)

•Indications of (PCS)
previous patellectomy
oweak extensor mechanism leads to anterior
dislocation even with a cruciate retaining prosthesis
with an intact PCL
inflammatory arthritis
oinflammatory process leads to late PCL rupture.
Therefore, you can not rely on the PCL and it should
be sacrificed prophylacticly
deficient PCL
rupture or attenuation of the PCL
either during surgery or from
a previous injury is an indication
for a posterior cruciate substituting
prosthesis

3. Constrained Nonhinged
Design
prosthesis has a large central post that substitutes for
MCL and LCL
the tibial post is wider and taller than it is for a
posterior cruciate substituting design so it actually
provides varus / valgus stability
•Indications
LCL attenuation or deficiency
MCL attenuation or deficiency
(deficiency of MCL is controversial
because load may lead to breaking of
central post)
flexion gap laxity

4.Constrained Hinged with rotating platform
Hinged implants. One degree of freedom
Design
femur and tibia connected by bar and bearing
tibial component rotates within yoke allow internal
and external rotation during gait early designs did
not have a rotating platform and had a very high
loosening rate due to the rotational forces that
were placed on the implant
intramedullary stem needed to
address high rotational loads

•Indications
global ligament deficiency
hyperextension instability (seen with polio or
tumor resection)
knee resection for tumor
charcot arthropathy (relative)
complete MCL deficiency (relative
and controversial)

5. Mobile Bearing
•Design
mobile-bearing poly i.e.
: non fixed to tibia
creates a dual surface
interface of metal and poly
increases conformity of metal and poly
•Indications
theoretically reduces wear
oincreased contact area reduces
pressures placed on poly (pressure=force/area)

Surgical Approaches
A-Medial parapatellar
retinacular approach.
B-Subvastus approach.
C-Midvastus approach.

Surgical Approaches

Subvastus approach:

Intact extensor
mechanism.

Decreasing pain.

More limited.

Postoperative
hematoma.

Midvastus approach:

Preserve genicular a.
to the patella.

Contraindication in
limited preoperative
flexion.

Postoperative
hematoma.

TKA techniques
Approaches
•Antibiotic loaded bone cement
routine use in all TKA increases the risk of aseptic
loosening
reduces deep infection in revision TKA
indications for use in primary TKA are controversial

•Technical goals
Restore mechanical alignment (mechanical
alignment of 0°)
Restore joint line ( allows proper function of
preserved ligaments. e. g: PCL )
Balanced ligaments (correct flexion and
extension gaps)
Maintain normal Q angle (ensures proper
patellar femoral tacking)

•
Indications for TKA
Relieve pain caused by osteoarthritis of the knee (the most
common).
Deformity in patients with variable levels of pain:
Flexion contracture > 20 degrees.
Severe varus or valgus laxity.
Osteoarthritis
•
American College of Rheumatology classification criteria:
Knee pain and radiographic osteophytes and at least 1 of the
following 3 items:

Age >50 years.

Morning stiffness <=30 minutes in duration.

Crepitus on motion.

Relative contraindications
1-medical conditions that compromise the patients
ability to withstand anesthesia and wound healing
2- significant atherosclerotic disease of the operative
leg
3- skin condition such as psoriasis within the operative
field , venous stasis disease with recurrent cellulitis .
4-neuropathic arthropathy
5-morbid obesity
6-recurrent urinary tract infection
7-history of osteomyelitis in the proximity of the knee

Contraindications for TKA
•Recent or current knee sepsis.
•Remote source of ongoing infection.
•Extensor mechanism discontinuity or severe
dysfunction.
•Painless, well functioning knee arthrodesis.

•Unicondylar Knee Arthroplasty
•Indications:
►Younger patients with unicompartmental disease
►Elderly thin patient with unicompartmental disease
(shorter rehabilitation, greater ROM)
•Contraindications:
►Flexion contracture >= 5 degrees.
►ROM < 90 degrees.
►Angular deformity >= 15 degrees.
►Cartilaginous erosion in the weight-bearing area of the
opposite compartment.

Important consideration
 pre-op planning
 component insertion
 ligament balancing
 prosthetic design selection
The femoral component usually is implanted in 5 to 6
degrees of valgus, the amount necessary to reestablish
a neutral mechanical axis of the limb

Mechanical axis of lower limb
Extends from center of femoral
head to center of ankle joint and
passes near or through center of
knee.
The line drawn on a standing long
leg anteroposterior radiograph from
the center of the femoral head to
the center of the talar dome.

Mechanical axis of Limb
Axis from center of femoral head to center of ankle.
Femoral Alignment
•Anatomic axis femur (AAF)
a line that bisects the medullary canal of the femur
determines entry point of femoral medullary guide
rod
femoral guide goes down mechanical axis
Anatomical axis of femur is in 6 degrees of valgus
from mechanical axis of lower limb and 9 degrees of
valgus from true vertical axis of body.

•Mechanical axis femur(MAF)
Defined by line connecting center of femoral head to point
where anatomic axis meets intercondylar notch.
Obtaining a neutral mechanical axis allows even load
sharing between the medial and lateral condyles of a knee
prosthesis.
It is in 3 degrees of valgus from vertical axis of body.

•Valgus cut angle (~5-7° from AAF )
difference betweeen AAF and MAF
perpendicular to mechanical axis
jig measures 6 degrees from femoral guide
(anatomic axis)
will vary if people are very tall (VCA < 5°) or very
short (VCA > 7°)
can measure on a standing full length AP x-
ray

Tibial alignment
Anatomic axis of tibia (AAT)
•a line that bisects medullary canal
•Tibia medullary guide (internal or external)
runs parallel to it
•determines entry point for tibial medullary
guide rod

Mechanical axis of tibia
•Line from center of proximal tibia to center of ankle
•Proximal tibia is cut perpendicular to mechanical axis
of tibia
•Usually mechanical axis and anatomic axis of tibia are
coincident and therefore you can usually can cut the
proximal tibia perpendicular to anatomic axis (an axis
determined by an intramedullary jig)
•If there is a tibia deformity and the mechanical and
anatomic axis are not the same, then the proximal tibia
must be cut perpedicular to the mechanical axis
(therefore an extramedullary tibial guide must be used)

Longitudinal Alignment Of Knee:
Posterior tibial tilt is about 5 – 7
degrees.
•Usually depend on the articular
design.

Rotational
Alignment Of Knee:
•Create a rectangular
flexion space.
•External rotation of
the femoral component
3 degrees.

Two primary techniques are used to align the
tibial component rotationally.
The first technique aligns the center of the tibial
tray with the junction of the medial third of
the tibial tubercle with the lateral two thirds
The second technique places the knee through a
range of motion with trial components in
place, allowing the tibia to align with the
flexion axis of the femur.

Patellofemoral Alignment
 Q angle : angle between axis of
extensor mechanism (ASIS to center of patella)
and axis of patellar tendon(center of patella to tibial
tuberosity)
o Abnormal patellar tracking, although not the most
serious
is the most common complication of TKA.
o The most important variable in proper patellar tracking
is preservation of a normal Q angle (7°) .

Any increase in the Q angle will lead to increased lateral
subluxation forces on the patella relative to the trochlear
groove, which can lead to pain and mechanical
symptoms, accelerated wear, and even dislocation.
It is critical to avoid techniques that lead to
an increased Q angle. Common errors include
 internal rotation of the femoral prosthesis
 medialization of the femoral component
 internal rotation of the tibial prosthesis
 placing the patellar prosthesis lateral on the
patell

Patellar Resurfacing:
•Indication for leaving the patella
unresurfaced:
►Congruent patellofemoral tracking.
►Normal anatomical patellar shape.
►No evidence of crystalline or
inflammatory arthropathy.
►Lighter patient.

Preserving joint line and angle (includes rotation)
Goal is to restore the joint line by inserting a
prosthesis that is the same thickness as the bone
and cartilage that was removed
this preserves appropiate ligament tension
if there are bone defects they must be addressed
so the joint line is not jeopardized

elevating the joint line (> 8mm leads to motion
problems) and can lead to
omid-flexion instability
opatellofemoral tracking problems
oan "equivalent"
to patella baja
onever elevate joint line
in a valgus knee until after
balancing to obtain full
Extension
lowering joint line
can lead to
• lack of full extension
• Flexion instability

coronal balancing
Introduction
Both medial and lateral ligaments may be
stretched or contracted with time. It is essential to
balance these ligament in both the coronal and
sagittal plane to obtain an optimum outcome
Principles of ligament balancing for deformities is
to
release the tight ligaments
tighten the stretched ligaments

Varus Deformity
Goal is to release the tight medial ligaments and
tighten the lax lateral ligaments
Medial releases (usually osteophytes and deep
MCL is adequate)
osteophytes
deep MCL (meniscotibial ligament) and capsule
(usually osteophytes and deep MCL is sufficient
release)

semimembranosus
superfical MCL
•can find as it blends into pes anserine complex
•can not completely release or will have valgus
instability (requires constrained prosthesis).
Therefore perform subperiosteal elevation only
•Differential release: performed with two
component of superficial MCL
posterior oblique portion is tight in extension
(release if tight in extension)
anterior portion is tight in flexion (release if tight
in flexion)
PCL
Lateral tightening
use a prosthesis that is sized to "fill up" the gap and make
the stretched lateral ligaments taut

Valgus Deformity (medial is convex side of
deformity)
Goal is to release the tight lateral ligaments and tighten the
lax medial ligaments
Lateral release order
osteophytes
lateral capsule
iliotibial band if tight in extension (release if tight in
extension)
with Z-plasy or release off Gerdy's tubercle
popliteus if tight in flexion (release if tight in flexion
for severe deformities release both the iliotibial band
and the popliteus

LCL
Some authors prefer to release this structure first if tight
in both flexion and extension
Others prefer this should be the last structure to release,
if you need to release it consider of constrained prosthesis
Differential release: performed by differentially
release the IT band and popliteus

•Medial tightening
fill up medial side until medial ligament complex is taut
•Peroneal nerve palsy
correction of valgus and flexion contracture deformity has highest
risk of peroneal nerve palsy
if patient presents with a peroneal palsy in recovery room then:
then take of dressing and flex the knee
if it does not return test it to see if it is cut
if not cut, watch for three months
explore if no return after 3 or 4 months

Flexion / Contracture Deformity
Order of posterior release
osteophytes
posterior capsule
gastronemius muscles (medial and lateral)
You do not want to address by removing too much tibia
will change joint line and lead to patella alta

*sagittal(gap)balancing
Go
balancing is complex due
to two radii of curvatures
(patellofemoral
articulation and
tibiofemoral articulation)
often requires soft tissue
release and bony
resection to obtain
balance
•Goal is to obtain a gap that is equal in flexion
and extension. This will ensure that the tibial
insert is stable throughout the arc of motion.

•General Rules
adjust femur if asymmetric
odistal femur cut affects extension gap
oposterior femur cut affects flexion gap
adjust tibia if problem is symmetric (same in
both flexion and extension)
otibia cut affects both flexion and extension
gap
remember increasing/decreasing the size of the
femoral component only changes the AP
diameter and does not affect the height of the
prosthesis.

Evaluation &Treatment
The following chart shows different conditions found with the trials in place
and the treatment strategy for each condition
Solution
Proplem
Scenario
Solution:
Cut more proximal tibia
Symmetric gap:
Problem:
Did not cut
enough tibia
Tight in Extension
(cant fully extend)
Tight in Flexion
(can not fully flex)
Solution:
1) Increase size of femoral component (AP
only next size )
2) Posteriorize femoral component
(augment posterior femur by bone cement
or metal augmentation ).
Cut too much
posterior femur.
Extension good
Flexion loose (large
drawer test )

Solution:
1) Decrease size of femoral component
2) Recess & release PCL
3) Resect posterior slope in tibia
4) Resect more posterior femoral condyle
5) Release posterior capsule
Problem:
Did not cut enough posterior
femur, PCL scarred and too tight.
Extension good
Flexion Tight
Solution:
1) Release posterior capsule
2) Cut more distal femur
(1-2mm)
Tight in Extension, Balanced in
Flexion
Problem:
Did not cut enough distal femur
or did not release enough
posterior capsule
Tight in Extension,
Flexion good
Solution:
1) Augment distal femur
2) small size femur
3)use thicker polyethylene
Problem:
Cut too much distal femur or
anteroposterior diameter too big
Extension Loose ,
Flexion good
Solution:
1) Use thicker tibia PE
2) Use thicker tibial metal insert
Problem:
Cut too much tibia.
Loose in
Extension, Loose
in Flexion

A:The flexion gap in A is larger
than the extension gap seen in B.
As seen in A', this results in a
knee that is too tight in flexion,
producing a flexion contracture.
As seen in
B', if this problem is approached
by using a thinner tibial
component, the prosthesis will
be too loose in flexion. As seen in
C', the solution is to excise more
bone from the distal femur. B: In
Aâ€³ and Bâ€³, the extension gap
is excessive. As seen in Câ€³, this
is solved by a â€œbuild-upâ€ on
the femoral side

Precision is paramount because an asymmetry of only 5%
can lead to liftoff of the femoral component on the tibia,
with compressive forces all on one side and tensile forces
on the other. Subtle malalignment can magnify with time
as soft tissues attenuate under excessive forces.
Specifically, varus alignment of the tibial component has
been associated with a higher rate of radiolucency about
the prosthesis and a higher rate of loosening
Malalignment in a
TKA significantly
reduces
survivorship of the
implant

Preoperative Evaluation
Soft tissue defects around the knee.
Vascular status to the limb.
Extensor mechanism.
Preoperative range of motion.
Preoperative Radiographs

Preoperative Radiographs
Arthritis series
Standing full-length radiographs(AP and Lateral) are
indicated to determine an accurate valgus cut angle
when the patient has
femoral or tibial deformity
very tall or short stature
Standing AP and lateral of kneeto evaluate for
joint space narrowing
collateral ligament insufficiency (look for lateral
gapping)
subluxation of femur on tibia
bone defects
Extension and flexion laterals Sunrise view
A skyline view of the patella.

YOUR INVESTIGATIONS MAY
INCLUDE-

Blood tests

Urinalysis

X-rays
(chest, knees, other involved areas)

ECG

TO GET MOST BENEFIT FROM YOUR TKR
YOU NEED TO PREVENT POSSIBLE
COMPLICATIONS-

TO PREVENT TEETH & MOUTH
INFECTIONS:

Get a dental check up

Brush regularly

Eat a balanced diet

Visit dentist in case of any problem without
overlooking it

TO PREVENT SKIN INFECTIONS:

Have a Betadine bath & scrub 3 times Pre-
operative.

Have no injections on the side of your
operation.

Avoid cuts & scratches.

Cut toe nails straight across to prevent in
growing of nails.

TO PREVENT URINARY INFECTIONS:

Drink adequate amount of fluids.

Keep your genitals clean.

Visit the Dr. immediately in case of any
discomfort.

TO PREVENT RESPIRATORY
INFECTIONS:

Such as – Pneumonia, Atelectasis

You should :-

Turn & move around in bed frequently.

Practice Deep Breathing & Coughing.

Exercise your lungs with the help of your
Physiotherapist.

HOW A PHYSIOTHERAPIST CAN
HELP?

He will:-
Evaluate the amount of movement in your joints
called “Range of Motion”
Test your Muscle strength
Teach Gait training, with appropriate equipment
(walker, crutches, sticks, etc)
Teach transfers with appropriate equipment
(Bed,Toilet, Bathtub, Chair, Car, etc.)

contd…
He will instruct you in exercises that :-
Help you gain & maintain Muscle strength
Help you gain & maintain Range of Motion
Promote blood circulation
Help you get the most benefit from your
surgery

Exercises YOU NEED TO DO
PRE-OPERATIVELY
“Gluteal sets”

To maintain & strengthen Hip Muscles (Buttocks)

Lie flat on your back in bed

Tighten the hip muscles together

Hold tense for 10 sec.

Relax for 5 sec.

10 repetitions (3-4 times a day)

“CALF PUMPING”

Tones up & strengthens the lower leg & foot

Lie flat in bed

Point your toes towards the foot of bed

Point your toes towards your knee


“QUADS SETS”

Strengthen the muscle (Quadriceps) on the front
of your thigh.

Lie flat on bed

Press the back of your knee against the bed

Try to lift the heel off the bed


“STRAIGHT LEG RAISES (SLR)”

Benefits the Quadriceps muscle

Lie flat on your back

Keep the knee as straight as possible

Left your leg above the bed for 5 sec.

Lower your leg slowly


Surgical Technique for
Primary TKA

Surgical Preparation
Secure two separate bumps to the table on the
operated side as leg positioners
full extension
30 °of flexion
100 °of flexion when
the second bump is used

Surgical Preparation(cont.)

Administer a dose of a 1st
generation cephalosporin (or
vancomycin,
clindamycin)
Avoid pressure on peripheral
nerves. (prolonged
positioning in the recumbent
position)
Elevate the patient's buttock
on the operative side with a
soft roll to produce a stable
upright positioning of the
knee

Surgical Preparation(cont.)
The tourniquet should have been placed on the thigh as
high as possible and the skin protected with soft padding.
Shave the skin around the knee immediately before the
procedure to limit compromise of the skin surface. Extended
time between shaving and surgery promotes colonization of
small nicks with bacteria.
Surgically scrub the limb and do a final skin prep with an
antibacterial solution. Take meticulous care during draping.
Drape the skin sterilely as high as possible, and to at least 4
inches below the tibial tubercle. Apply an adherent sterile
vinyl dressing.
Avoid excessively bulky drapes on the lower extremity.
Precise alignment in total knee replacement depends on the
ability to palpate the tibial spine, the malleoli, or bones of the
foot. A bulky drape on the foot obscures landmarks and
makes surgery more difficult.

With the patient prepped and draped, flex the knee to a 30 °
position and mark the surgical incision. Flexion produces tension on
the anterior tissues, which allows a more precise surgical exposure.
A midline longitudinal incision is preferred unless otherwise dictated
by prior skin incisions.
The exposure extending approximately five fingerbreadths above
the superior patella and five fingerbreadths below the inferior
patella
arthrotomy longitudinally in a gentle
curve, which will start at the midpoint of
the quadriceps tendon proximally, curve
around the patella so that it intersects a
point just medial to the patella, and then
curve back to a point on the tibial tubercle
medially
TECHNIQUE

Transect the anterior horn of the medial meniscus.
Elevate the patella, with the knee in extension and pulled toward
the surgeon. Release tight bands in the patellar retinaculum or plica
with electrocautery and avoid the patella.
Place a retractor along the medial joint line and flex the knee to 90 °
or 100 °The potential for patella tendon avulsion exists in the tight
knee, As the knee is flexed, carefully watch the insertion of the
patella tendon to avoid any excessive flexion that may avulse the
patella tendon.
(extending the arthrotomy proximally, doing more distal soft-tissue
releases, or considering quadriceps release or tibial tubercle
osteotomy )
Once patella tendon avulsion occurs, it is very difficult to treat, so
this complication is best avoided
TECHNIQUE-cont.

The anterior cruciate ligament is generally resected .
remove medial and lateral osteophytes to expose the PCL
attachment to the femur. Most knees will have an intact
PCL.
PCL is sacrificed .(The PCL lies immediately in front of the
posterior capsule, which lies in front of the neurovascular
structures. The PCL should not be sacrificed in a
cavalier( (
‫ارس‬‫ف‬
‫او‬
‫متعجرف‬ fashion, but it should be done
precisely. Place a curved clamp behind the PCL to define its
substance and direction, then take electrocautery and remove
the PCL subperiosteally off the femoral attachment)
Release the anterior horn of the lateral meniscus and
resected.
TECHNIQUE-cont.

Bone Preparation
Bone surface preparation is based on the following principles:
appropriate sizing of the individual components,
alignment of the components to restore the mechanical axis,
recreation of equally balanced soft tissues in flexion and extension,
and optimal patellar tracking.
odistal femur cut
affects extension gap
oposterior femur cut
affects flexion gap

Bone Preparation – IM Femoral Guide
The goal of the femoral preparation is to resurface the abnormal
femur with a femoral implant articulating surface.The distal level
of the femoral implantation is critical to preserve the proper level
of the joint line
The flexion and extension gap
must be correct.The varus and
valgus alignment and proper
external rotation are critical.

Make the center drill hole into the medullary canal, approximately
3/8 inch (9 mm), just medial to the center of the notch to provide
the best line of axillary alignment
Bone Preparation – IM Femoral Guide(conti.)
Place the hole just above the insertion (point anterior to the origin of
the posterior cruciate ligament) of the PCL, but not so anterior that
bec. risk of perforating the anterior cortex. Drill the hole straight
and make it slightly larger than the intramedullary guide rod.
Once the hole is drilled, aspirate
marrow products to prevent
embolization.
Take care not to place the drill hole
in the midline of the femoral
condyles because an abnormal
valgus angulation will occur
because this is not aligned with the
medullary canal

Rotation of the Femoral Component
Rotation of the femoral component is key .
The patellofemoral mechanics are altered dramatically by femoral
component rotation.
An excessively internally rotated femoral component will have much
higher rates of patellar subluxation and altered patellofemoral
mechanics.
In general, some external rotation of
the femoral component is desirable.
Also, because tibial
resections are performed
perpendicular to the long axis, not
the normal 3 °medial inclination
of the tibial plateauâ an externally
rotated femoral component is
necessary to make the flexion gap
equal

Set the proper valgus angle and insert the IM Alignment Guide
Proximal/Distal Positioning
Varus/Valgus and
Flexion/Extension Alignment for the Femur

TECHNIQUE
Make the distal femoral cut at a valgus angle (usually 5 to 7 degrees)
perpendicular to the predetermined mechanical axis of the femur.
The amount of bone removed generally is the same as that to be
replaced by the femoral component. If a significant preoperative
flexion contracture is present, remove additional bone from the
distal femur at this time to widen the extension gap.
The anterior and posterior femoral cuts determine the rotation of
the femoral component and the shape of
the flexion gap. Excessive external rotation
widens the flexion gap medially and may
result in flexion instability.
.

Internal Rotation of Femoral Prosthesis will Increase Q angle
by internally rotating the femoral prosthesis, you are
effectively bringing the groove and the patella medially. This
will increase the Q angle to the tibial tubercle
will also make the medial compartment tigh
•Medialization of the Femoral Prosthesis will Increase Q
angle
a medialized femoral prosthesis will
bring the trochlear groove to a more
medial position, and thus bring the
patella medial with it, thus increasing
the Q angle
therefore, you want the femoral
component to be slighly lateral if
anything

TECHNIQUE-cont.
Femoral component rotation can be determined by one of several
methods.The anteroposterior axis .transepicondylar axis,, posterior
femoral condyles, and cut surface of the proximal tibia all can serve
as reference points.
anteroposterior axis
defined as a line running from the center of the trochlear groove to
the top of the intercondylar notcha line perpendicular to this defines
the neutral rotational axis

if the lateral femoral condyle is
hypoplastic, use of the posterior condylar
axis may lead to internal rotation of the
femoral component
transepicondylar axis
defined as a line running from the medial and lateral epicondyles the epicondylar
axis is parallel to the tibial surface .A posterior femoral cut parallel to the
epicondylar axis will create the appropriate rectangular flexion gap
posterior condylar axis
defined as a line running across the tips of the two posterior condyles
this line is in ~ 3 degrees of internal rotation from the transepicondylar axis, the
femoral prosthesis should be externally rotated 3 degrees from this axis to
produce a rectangular flexion gap
TECHNIQUE-cont.

Regardless of the method used, the thickness of bone removed from
the posterior aspect of the femoral condyles should equal the thickness
of the femoral component.This determined directly by measuring the
thickness of the posterior condylar resection with posterior resurfacing
instruments.
Posterior referencing instruments are theoretically more accurate in
recreating the original dimensions of the distal femur; however,
anterior referencing instruments have less risk of notching the
anterior femoral cortex and place the anterior flange of the femoral
component more reliably against the anterior surface of the distal
femur.

Fix the Distal Femoral Cutting Guide
Remove the IM Alignment Guide
Resect the distal femur

Apply the A/P Sizing Guide to the distal femur
Attach the Locking Boom and place it lateral on the anterior cortex
Read the femoral size

Attach the External Rotation Plate to the Sizing Guide
Place Headless Pins throught the holes that correspond to desired
external rotation
Pin placement should be parallel to epicondylar line

Place the Femoral Finishing Guide over Headless Pins
Check mediolateral position
Fix the Finishing Guide with screws or pins
Check anterior cut with Resection Guide

Cut the femoral profile in the shown sequence

Drill distal holes with Patella/Femoral Drill Bit
Cut trochlear recess with reciprocating saw

Complete the distal femoral preparation for a PCL-retaining
prosthesis by making anterior and posterior chamfer cuts for the
implant. If a PCL-substituting design is chosen, remove the
intercondylar box to accommodate the housing for the post and
cam mechanism

If the distal femoral resection has not been completed, balance the
flexion and extension gaps at this time by placing spacer blocks or a
tensioner within the gaps with the knee in flexion and extension.
Varus-valgus balance can be fine-tuned‫َّل‬‫د‬َ‫ع‬ُ‫م‬ with further medial or
lateral releases .
Remove any medial or lateral osteophytes that tent the collateral
ligaments.
Remove posterior condylar osteophytes with a curved osteotome
because they can tent the posterior capsule and narrow the extension
gap or impinge during knee flexion.
The flexion and extension gaps must be roughly equal. If the
extension gap is too small or tight, extension is limited. Similarly, if
the flexion gap is too tight, flexion is limited. Laxity of either gap can
lead to instability.

•The preferred rotation of the tibial component is neutral,
with no internal or external rotation.
the best way to obtain this is to have the tibial component
centered over the medial third of the tibial tubercle
this will leave a portion of the posteromedial tibia uncovered
and some overhang of the prosthesis over the tibia on the
posterolateral tibia
•Internal Rotation of Tibial Prosthesis
will increase Q angle .
Medialization of tibia will increase Q
angle
Tibial Prosthesis

Bone Preparation – Tibial Resection

The guide is aligned with
the anterior tibial tendon
and first web space of the
toes.

Intramedullary and Extramedullary Alignment Instrumentation
Intramedullary alignment instrumentation is crucial on the femoral
side of aTKA because femoral landmarks are not easily palpable.
The entry portal for the femoral alignment rod typically is placed a
few millimeters medial to the midline, at a point anterior to the
origin of the PCL. Preoperative radiographs should be scrutinized for
a wide canal or excessive femoral bowing because these conditions
may result in alignment errors.
Extramedullary femoral alignment is useful only in limbs with severe
lateral femoral bowing, femoral malunion, or stenosis from a
previous fracture, or when an ipsilateral total hip replacement or
other hardware fills the intramedullary canal. A palpable marker can
be placed over the center of the femoral head based on preoperative
hip radiographs.The anterior superior iliac spine has been shown to
be unreliable for determining the hip center and should not be used
as the primary landmark when extramedullary femoral alignment is
chosen

The use of tibial intramedullary alignment guides is more
controversial.
One concern about the use of these guides is the risk of fat
embolism. Greater elevation of pulmonary arterial pressures and
slightly diminished cardiac indices in patients undergoing bilateral
TKAs using intramedullary tibial alignment guides compared with
extramedullary tibial alignment guides and venting of the femoral
intramedullary canals.

They did not believe, however, that these slight changes
constituted any contraindication to the use of intramedullary
alignment devices.

a bout 12% prevalence of postoperative neurological changes
believed to be consistent with fat embolism after bilateralTKA and
recommended the use of pulmonary arterial pressure monitoring.
They showed that the negative cardiopulmonary effects of
intramedullary femoral alignment rods were eliminated by drilling
an oversized 12.7-mm hole in the distal femur and using an 8-mm
fluted rod.

Cut the tibia perpendicular to its mechanical axis with 0 to
5 degrees of posterior slope, and remove approximately 6
to 8 mm of the proximal tibia, as measured from the intact
compartment. Protect the patellar tendon and collateral
ligaments during this portion of the procedure.
Alternatively, the proximal tibia can be cut before
completion of the distal femoral cuts
TECHNIQUE
Position of tibial cutting jig: In A, the
guide is aligned with the anterior tibial
tendon and first web space of the toes,
producing an appropriate cut. In B, the
alignment jig is centralized on the ankle
joint, which is too lateral, resulting in
excessive varus in the cut of the tibial
plateaus

(GAPTECHNIQUE)
If the extension gap is smaller than the flexion gap, remove more
bone from the distal femoral cut surface, or release the posterior
capsule from the distal femur
If the flexion gap is smaller than the extension gap, remove more
bone from the posterior femoral condyles by making appropriate
cuts for the next smaller available femoral component.
If the flexion and extension gaps are equal, but there is not enough
space for the desired prosthesis, remove more bone from the
proximal tibia because bone removed from the tibia affects the
flexion and extension gaps equally.
When the flexion and extension gaps are equal but lax, a larger
spacer block and a thicker tibial polyethylene insert are required to
obtain stability.

EM IM
With Spike Arm
IM
Tibial Resection

Cut proximal tibia with 1,27 mm oscillating saw blade

Check alignment
Extension Gap
Check & Balance
Flexion/Extension Gap

Place and fix Guide
MIS PS Notch Guide
Cut out the intercondylar
notch

Determine size & rotation
Fix with pins
Drill with Stem Drill
through Drill Sleeve

AssembleTibial Broach to
Broach Impactor
Impact Broach to
proper depth

Insert Femoral Provisional,Tibial Sizing Plate and
Articular Surface Provisional
Perform final trial run

Total knee arthroplasty by dr..ammar m.sheet

Total knee arthroplasty by dr..ammar m.sheet

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