Transcript Document

Total Knee Arthroplasty
Dr. Rami Eid
06/06/2006
Introduction
► TKA
is one of the most successful and
commonly performed orthopedic surgery.
► The
best results for TKA at 10 – 15 yrs.
compare to or surpass the best result of
THA.
Indications for Knee Arthroplasty
Indications for TKA
► Relieve
pain caused by osteoarthritis
of the knee (the most common).
► Deformity
pain:
in patients with variable levels of
 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.
Contraindications for TKA
► Recent
or current knee sepsis.
► Remote source of ongoing infection.
► Extensor mechanism discontinuity or severe
dysfunction.
► Painless, well functioning knee arthrodesis.
► Poor
health or systemic diseases (relative
contraindications).
Unicondylar Knee Arthroplasty
► Indications:
 Younger patients with
unicompartmental
disease instead of HTO.
 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.
Patellar Resurfacing
► Indication
for leaving the patella
unresurfaced:
 Congruent patellofemoral tracking.
 Normal anatomical patellar shape.
 No evidence of crystalline or inflammatory
arthropathy.
 Lighter patient.
Classification
Classification
1
3
1- Cruciate retaining
2- Cruciate
substituting
3- Mobile bearing
4- Unicondylar
2
4
Biomechanics of Knee Arthroplasty
Kinematics
► The
TRIAXIAL
motion of the knee:
 Articular geometry
 Ligamentous
restraints
Degrees of Freedom
Degrees of Freedom
► Constrained
Prostheses
► Non-constrained
► Intermediated
Prostheses
Prostheses
Constrained Prostheses
► Hinged
implants.
► One degree of freedom.
Non-constrained Prostheses
► Ideal
implants.
►5
degrees of
freedom.
► Intact
ligamentous
system.
Intermediated Prostheses
► Anterior-posterior
► Two
stability.
types:
 FREEMAN (a cylinder in a non conforming
trough).
 INSALL (posterior stabilized knee).
Intermediated Prostheses
Freeman
Insall
Longitudinal
Alignment Of
Knee
► Tibial
components are
implanted
perpendicular to the
mechanical axis.
► Femoral
component is
implanted in 5 – 6
degrees of valgus.
Longitudinal Alignment Of Knee
► Posterior
tibial
tilt is about 5 –
7 degrees.
► Usually
depend
on the articular
design.
Anatomic tilt 5 degrees
Rotational Alignment Of Knee
► Create
a rectangular
flexion space.
► External
rotation of
the femoral
component 3 degrees.
Role of PCL – Femoral Roll-Back
Role of PCL – Femoral Roll-Back
PCL-retention or PCL-substitution ?
►
PCL retaining
prostheses:
 Better ROM (roll-back, flat
tibial surface).
 More symmetrical gait (stair
climbing).
 Less femoral bone resection
is required.
 PCL needs to be accuracy
balanced.
►
PCL substituting
prostheses:
 Easier surgical exposure.
 See-saw effect prevention.
 Lower tibial polyethylene
contact stress
 Posterior tibial component
displacement.
 Patella clunk syndrome.
PCL-retention or PCL-substitution ?
PCL-retention or PCL-substitution ?
Patella Clunk Syndrome
Patellofemoral Joint
► The
patella acts to
lengthen extensor
lever arm.
► This
arm is greatest at
20 degrees of flexion.
Patellofemoral Joint
► Changes
in the patellar area of contact can leads
to eccentric loading of the patellofemoral joint.
Patellofemoral Joint
►
Limb with larger Q angle
has a greater tendency
for lateral subluxation.
►
Preventing subluxation:
 Prosthetic component.
 Vastus medialis (in early
flexion).
Polyethylene Issues
1- Dished polyethylene avoids the edge loading. (as PCL substitution)
2- Minimal polyethylene thickness >= 8 mm to avoid higher contact
stress.
Surgical Technique for Primary TKA
Preoperative Evaluation
► Soft
tissue defects around the knee.
► Vascular
status to the limb.
► Extensor
mechanism.
► Preoperative
► Standing
range of motion.
(AP) view, a lateral view of the knee, and
a skyline view of the patella.
Surgical Preparation
► Administer
a dose of a
1st generation
cephalosporin (or
vancomycin,
clindamycin)
► Avoid pressure on
peripheral nerves.
Surgical Approaches
► Medial
parapatellar
retinacular
approach.
► Subvastus
approach.
► 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.
Surgical Approaches
► Lateral
parapatellar
retinacular approach:
 In valgus knees.
 Improve patellar
tracking and
ligamentous balancing.
Bone Preparation – IM Femoral
Guide
Bone Preparation – Gap Technique
Bone Preparation – Tibial Resection
► The
guide is aligned
with the anterior tibial
tendon and first web
space of the toes.
Balancing of The Knee
Varus Deformity
► 1st
Osteophytes must be removed.
► 2nd
Release the deep MCL.
► 3rd
Release semimembranosus and pes
anserinus insertion.
► 4th
release posterior capsule and PCL.
Varus Deformity
Valgus Deformity
► 1st
Remove all osteophytes.
► 2nd release lateral capsule.
► 3rd
 Lesser deformity: release Iliotibial band.
 Greater deformity: release LCL +/- PCL.
► Valgus
deformity + flexion contracture >>
release posterior capsule.
Valgus Deformity
Flexion Contracture
► Extension
gap < Flexion gap >> more distal
femoral bone cut, posterior capsule release.
► Flexion
insert.
gap < Extension gap >> larger tibial
Flexion – Extension
Balancing
Computer Assisted Surgery in
Total Knee Arthroplasty
Management of Bone Deficiency
Patellofemoral Tracking
► Internal
rotation of
tibial component
increases the tendency
to lateral patellar
subluxation.
► Prosthetic
patella
should be medially
positioned.
Postoperative Management
Roentgenographic Evaluation
Total knee replacement exercise protocol
► Postoperative
day 1
 Bedside exercises (e.g. ankle pumps, quadriceps
exercises…)
► Postoperative
day 2
 Exercises for active ROM and terminal knee extension
 Gait training with assistive device
► Postoperative
day 3-5
 Progression of ambulation on level surfaces and stairs
(if applicable)
► Postoperative
day 5 to 4 weeks
 Stretching of quadriceps and hamstring muscles
 Progression of ambulation distance
Specific Disorders
Previous HTO
► Difficult
surgical
exposure.
► Lateral ligamentous
laxity.
► Difficult stem
placement.
► Patella infera.
Previous Patellectomy
► PCL
retaining
arthroplasty for better
results.
Complications of Total Knee
Arthroplasty
► Thromboembolism.
► Infection.
► Neurovascular
complications.
► Patellofemoral
complications.
► Periprosthetic
fractures.
Patellofemoral Complications
► Patella
clunk syndrome.
► Patellar component
failure.
► Rupture of patellar
ligament.
Periprosthetic Fractures
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