Total Knee Arthroplasty

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Total Knee Arthroplasty
Dr. Rami Eid

• 06/06/2006

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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.

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Indications for Knee Arthroplasty
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Indications for TKA

• Relieve pain caused by osteoarthritis of the knee
  (the most common).
• Deformity in patients with variable levels of
  pain
• Flexion contracture gt 20 degrees.
• Severe varus or valgus laxity.

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Osteoarthritis

• American College of Rheumatology classification
  criteria
• Knee pain and radiographic osteophytes and at
  least 1 of the following 3 items
• Age gt50 years.
• Morning stiffness lt30 minutes in duration.
• Crepitus on motion.

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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).

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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 gt 5 degrees.
• ROM lt 90 degrees.
• Angular deformity gt 15 degrees.
• Cartilaginous erosion in the weight-bearing area
  of the opposite compartment.

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Patellar Resurfacing

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

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Classification
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Classification
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3
1- Cruciate retaining 2- Cruciate substituting 3-
Mobile bearing 4- Unicondylar
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2
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Biomechanics of Knee Arthroplasty
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Kinematics

• The TRIAXIAL motion of the knee
• Articular geometry
• Ligamentous restraints

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Degrees of Freedom
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Degrees of Freedom

• Constrained Prostheses
• Non-constrained Prostheses
• Intermediated Prostheses

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Constrained Prostheses

• Hinged implants.
• One degree of freedom.

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Non-constrained Prostheses

• Ideal implants.
• 5 degrees of freedom.
• Intact ligamentous system.

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Intermediated Prostheses

• Anterior-posterior stability.
• Two types
• FREEMAN (a cylinder in a non conforming trough).
• INSALL (posterior stabilized knee).

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Intermediated Prostheses
Freeman
Insall
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Longitudinal Alignment Of Knee

• Tibial components are implanted perpendicular to
  the mechanical axis.
• Femoral component is implanted in 5 6 degrees
  of valgus.

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Longitudinal Alignment Of Knee

• Posterior tibial tilt is about 5 7 degrees.
• Usually depend on the articular design.

Anatomic tilt 5 degrees
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Rotational Alignment Of Knee

• Create a rectangular flexion space.
• External rotation of the femoral component 3
  degrees.

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Role of PCL Femoral Roll-Back
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Role of PCL Femoral Roll-Back
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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.

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PCL-retention or PCL-substitution ?
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PCL-retention or PCL-substitution ?
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Patella Clunk Syndrome
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Patellofemoral Joint

• The patella acts to lengthen extensor lever arm.
• This arm is greatest at 20 degrees of flexion.

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Patellofemoral Joint

• Changes in the patellar area of contact can leads
  to eccentric loading of the patellofemoral joint.

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Patellofemoral Joint

• Limb with larger Q angle has a greater tendency
  for lateral subluxation.
• Preventing subluxation
• Prosthetic component.
• Vastus medialis (in early flexion).

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Polyethylene Issues
1- Dished polyethylene avoids the edge loading.
(as PCL substitution) 2- Minimal polyethylene
thickness gt 8 mm to avoid higher contact stress.
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Surgical Technique for Primary TKA
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Preoperative Evaluation

• Soft tissue defects around the knee.
• Vascular status to the limb.
• Extensor mechanism.
• Preoperative range of motion.
• Standing (AP) view, a lateral view of the knee,
  and a skyline view of the patella.

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Surgical Preparation

• Administer a dose of a 1st generation
  cephalosporin (or vancomycin, clindamycin)
• Avoid pressure on peripheral nerves.

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Surgical Approaches

• Medial parapatellar retinacular approach.
• Subvastus approach.
• Midvastus approach.

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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.

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Surgical Approaches

• Lateral parapatellar retinacular approach
• In valgus knees.
• Improve patellar tracking and ligamentous
  balancing.

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Bone Preparation IM Femoral Guide
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Bone Preparation Gap Technique
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Bone Preparation Tibial Resection

• The guide is aligned with the anterior tibial
  tendon and first web space of the toes.

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Balancing of The Knee
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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.

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Varus Deformity
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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 gtgt release
  posterior capsule.

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Valgus Deformity
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Flexion Contracture

• Extension gap lt Flexion gap gtgt more distal
  femoral bone cut, posterior capsule release.
• Flexion gap lt Extension gap gtgt larger tibial
  insert.

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Flexion Extension Balancing
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Computer Assisted Surgery in Total Knee
Arthroplasty
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Management of Bone Deficiency
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Patellofemoral Tracking

• Internal rotation of tibial component increases
  the tendency to lateral patellar subluxation.
• Prosthetic patella should be medially positioned.

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Postoperative Management
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Roentgenographic Evaluation
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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

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Specific Disorders
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Previous HTO

• Difficult surgical exposure.
• Lateral ligamentous laxity.
• Difficult stem placement.
• Patella infera.

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Previous Patellectomy

• PCL retaining arthroplasty for better results.

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Complications of Total Knee Arthroplasty

• Thromboembolism.
• Infection.
• Neurovascular complications.
• Patellofemoral complications.
• Periprosthetic fractures.

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Patellofemoral Complications

• Patella clunk syndrome.
• Patellar component failure.
• Rupture of patellar ligament.

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Periprosthetic Fractures
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THANK YOU
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• This lecture is one of a series of lectures were
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  department of orthopedics in Damascus hospital,
  under the supervision of Dr. Bashar Mirali.
• This site is not responsible of any mistake may
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