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Total Knee Arthroplasty. 06/06/2006. Dr. Rami Eid. 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.

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Total knee arthroplasty l.jpg

Total Knee Arthroplasty

06/06/2006

Dr. Rami Eid


Introduction l.jpg
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 tka l.jpg
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 l.jpg
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.


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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).


Unicondylar knee arthroplasty l.jpg

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.

Unicondylar Knee Arthroplasty


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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

1

3

1- Cruciate retaining

2- Cruciate substituting

3- Mobile bearing

4- Unicondylar

4

2



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Kinematics

  • The TRIAXIAL motion of the knee:

    • Articular geometry

    • Ligamentous restraints



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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.




Pcl retention or pcl substitution l.jpg

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 ?





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Patellofemoral Joint

  • The patella acts to lengthen extensor lever arm.

  • This arm is greatest at 20 degrees of flexion.


Patellofemoral joint29 l.jpg
Patellofemoral Joint

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


Patellofemoral joint30 l.jpg
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 >= 8 mm to avoid higher contact stress.



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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.


Surgical approaches36 l.jpg

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


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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 – Tibial Resection

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



Varus deformity l.jpg
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.



Valgus deformity l.jpg
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.



Flexion contracture l.jpg
Flexion Contracture

  • Extension gap < Flexion gap >> more distal femoral bone cut, posterior capsule release.

  • Flexion gap < Extension gap >> larger tibial insert.





Patellofemoral tracking l.jpg
Patellofemoral Tracking

  • Internal rotation of tibial component increases the tendency to lateral patellar subluxation.

  • Prosthetic patella should be medially positioned.




Total knee replacement exercise protocol l.jpg
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



Previous hto l.jpg
Previous HTO

  • Difficult surgical exposure.

  • Lateral ligamentous laxity.

  • Difficult stem placement.

  • Patella infera.


Previous patellectomy l.jpg
Previous Patellectomy

  • PCL retaining arthroplasty for better results.


Complications of total knee arthroplasty l.jpg
Complications of Total Knee Arthroplasty

  • Thromboembolism.

  • Infection.

  • Neurovascular complications.

  • Patellofemoral complications.

  • Periprosthetic fractures.


Patellofemoral complications l.jpg
Patellofemoral Complications

  • Patella clunk syndrome.

  • Patellar component failure.

  • Rupture of patellar ligament.




Mokazem com l.jpg
MoKazem.com

  • هذه المحاضرة هي من سلسلة محاضرات تم إعدادها و تقديمها من قبل الأطباء المقيمين في شعبة الجراحة العظمية في مشفى دمشق, تحت إشراف د. بشار ميرعلي.

  • الموقع غير مسؤول عن الأخطاء الواردة في هذه المحاضرة.

  • This lecture is one of a series of lectures were prepared and presented by residents in the department of orthopedics in Damascus hospital, under the supervision of Dr. Bashar Mirali.

  • This site is not responsible of any mistake may exist in this lecture.

Dr. Muayad Kadhim

د. مؤيد كاظم


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