tkr by dr. saumya agarwal

TOTAL KNEE REPLACEMENT

Presenter : Dr. Saumya Agarwal

Junior resident Dept of Orthopaedics J.N .Medical College and Dr. Prabhakar

Kore Hospital and MRC, Belgaum

INDEX

• Anatomy of the knee joint

• Common conditions leading to TKR

• Evolution of TKR

• Total knee replacement

• Approaches

• Procedure

• Complications

• Computer assisted technology

• Questions

Anatomy Of The Knee Joint

• Three bones and three compartment

Knee Stabilizers

• Medial • Lateral • Anterior • Posterior • Rotatory

Osteokinematics Gross movements of bones at joints

Flexion / extension Abduction / adduction Internal rotation / external rotation

Arthrokinematics Small amplitude motions of bones at joint surface

Roll Glide (or slide) Spin

INTRODUCTION

Arthroplasty is the surgical reconstruction of a joint which aims to relieve pain , correct deformities and retain movements of a joint.

Total Knee Arthroplasty(TKA) is the surgical procedure to replace the weight-bearing surfaces of the knee joint.

Common Conditions That Lead To TKR

• OSTEOARTHRITIS Primary (idiopathic)Secondary

Post traumatic arthritis

• RHEUMATOID ARTHRITIS

Evolution of TKR

• Fergussen(1860) resection arthroplasty

• Verneuil performed first interposition arthroplasty

• 1940s- first artificial implants were tried when molds were fitted in the femoral condyle

• 1950s- combined femoral and tibial articular surface replacement appeared as simple hinges

Evolution ….

• Frank Gunston(1971), developed a metal on plastic knee replacement

• John Insall(1973), designed what has become the prototype for current total knee replacements. This was a prosthesis made of three components which would resurface all 3 surfaces of knee - the femur, tibia and patella

Classification of Implants Design

• Unconstrained – Cruciate retaining– Cruciate substituting– Mobile bearing knees

• Constrained (Hinged)

• Unicondylar Prosthesis

• Total Condylar Prosthesis

Prosthetic Design

Femoral rollback

– Posterior translation femur with flexion

– Controlled by PCL

– Improves Quad function and knee flexion

Unconstrained TKR

Cruciate retaining

Intact PCL Varus < 10 Valgus < 15

• Advantage1. Avoid post cam impingement/ dislocation2. More closely resembles knee kinematics3. Bone preserving4. Improved proprioception

• Disadvantage 1. Tight PCL – Increased poly wear2. Rupture PCL – flexion instability

Cruciate stabilized

• Cam and post mechanism• Insert more congruent / dished

AdvantagesEasier to balance kneeMore range of motion

DisadvantagesCam jumpPost wearPatellar clunk syndromeAdditional cut from distal femur

ABSOLUTE INDICATION•Previous patellectomy

•Inflammatory arthritis

•Deficient PCL

Cruciate sacrifice / retain - Evidence

PS increased ROM – No functional improvement

No difference in ROM between PS and CR

PCL does not work in CR knees

Increased wear Ps knee – cam & post

Cochrane review – No difference in function whether cruciate retained

or sacrificed

Mobile Bearing Design

• Poly Rotates over tibial base plate

• Reduced poly wear

• Bearing spin out

Fixed Bearing or mobile bearing - Evidence

• No advantage of mobile bearing over fixed bearing

• Increased wear in undersurface of mobile bearing

Constrained TKR

Constraint

– Ability of prosthesis to provide varus – valgus and flexion –extension stability in presence of ligamentous laxity / bone loss

Constrained Hinged design

• Linked femoral and tibial components

• Tibial bearing rotates around yoke

Aseptic looseningLarge amount bone

resection

INDICATIONGlobal ligamentous deficiencyHyperextension instability

Hi Flex Design

• Cultural / pt expectation

• Cut more posterior condyle

Preop flexion - most significant - Gatha etal 2008No difference in ROM - Mehin JBJS 2010

No difference in ROM Sumino Int Ortho 2010

Uni condylar TKR

Advantages of Unicondylar TKR

• Shorter rehabilitation time

• Greater average post-op range of movement

• Preservation of proprioception function of cruciate ligaments

CONTRA-INDICATIONS

a) Inflammatory conditions

b) Damage to articular cartilage

c) Flexion contracture of 5° or more

d) Preoperative arc of motion less than 90°

e) Angular deformity of more than 15°

f) ACL deficiency

Total Knee Replacement Today

• Large variety is available

• Majority of TKR today are condylar replacements which consist of the following– Cobalt-chrome alloy femoral component– Cobalt-chrome alloy or titanium tibial tray– UHMWPE tibial bearing component– UHMWPE patella component

Who Is A Candidate For TKR

• Quality of life severely affected

• Daily pain

• Restriction of ordinary activities

• Evidence of significant radiographic changes of the knee

INDICATIONS• Severe arthritis

• Young pts with systemic arthritis with multiple joint involvement

• Osteonecrosis with subchondral collapse of a femoral condyle

• Severe pain from chondrocalcinosis and pseudogout in elderly

• Severe patello femoral arthritis rarely

CONTRA-INDICATIONS

• Recent/current knee sepsis

• Remote source of ongoing infection

• Extensor mechanism discontinuity

• Recurvatum deformity secondary to muscle weakness

• Presence of painless, well functioning knee arthrodesis

What Is The Time For Replacement

• Old age with more sedentary life style

• Young patients who have limited function

• Progressive deformity

• Other treatment modalities have failed

TKR should be done before things get out of hand and the patient experiences a severe decrease in ROM, deformity, contracture, joint instability or muscle atrophy

Evaluation Of Patient Before Surgery

• A Complete Medical History

• Thorough Physical Examination

• Laboratory Work-up

• Anesthesia Assessment

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Recommended Preoperative Radiographs in Knee Replacement Surgery

1. Standing full-length anteroposterior radiographfrom hip to ankle

2. Lateral knee x ray

3. Merchant’s view

Radiographs

• Standing Ap & Lateral• Sunrise – Merchant view

• Hip to ankle x- rays – Bony deformity– Short stature ( < 150 cm)– Very tall ( > 190 cm)

Radiographs

• Femoral and tibial cut• Position of femoral canal entry• Bone defects• Joint subluxation• Ligament stretch out – Varus Thrust • Ligament release• Constraint needed

Goal of TKR

• Pain relief

• Restoration of normal limb alignment

• Restoration of a functional range of motion

Successful Results Depends upon:

• Precise surgical technique

• Sound implant design

• Appropriate material

• Patient compliance with rehabilitation

Technical Goals Of Knee Replacement Surgery

1. The restoration of mechanical alignment

2. Preservation (or restoration) of the joint line

3. Balanced Ligaments

4. Maintaining or restoring a normal Q angle

Mechanical Alignment

TKA aims at restoring the mechanical axis of the lower limb by:Sequential soft tissue

releases

Correction of bone defects by grafts or prosthetic augments

Ligament Balancing

a. Coronal Plane– For varus deformities– For valgus deformities

b. Sagittal Plane– Flexion contractures– Extension contractures

Surgical Procedure

Procedure

Procedure

Procedure

Procedure

Procedure

Procedure

Procedure

VIDEO

APPROACHES

Medial parapatellar approach

• Most common• Surgeon are familiar

Lateral parapatellar approach

• Valgus knee• Allows access to lateral

side

• Technically demanding• Medial patellar eversion

difficult

Midvastus approach

• Spares VMO insertion

AdvantagesAccelerated rehab.Improved patellar tracking

DisadvantagesLess extensileDifficult in obese & flex

contracture

Subvastus approach• Vastus medialis lifted off

Lateral intermuscular septum

AdvantagesIntact quadPreserved vascularity of patella

DisadvantageLeast extensileDenervation of VMO possible

Femoral Cut

• Valgus cut angle• AAF – MAF

• Between 5 – 7 deg

• Intramedullary guide

Tibial Cut

• Angle between AAT – MAT

• Tibial cut angle- Zero

• Tibial deformity – cut perpendicular to MAT

• Intra or extramedullary guide

Joint line preservation• Inserting prosthesis same size as removed bone and

cartilage

Elevate joint line - mid flexion instabilityAbnormal patellofemoral trackingEquivalent to Patella Baja

Lowering joint line - Lack of full extension

Knee Balancing

• Balance in Coronal and saggital plane

• Concave side – ligaments contracted – release

• Convex side – ligaments stretched – Fill gap

Varus Knees

HenriK Schroeder – Boesch – Ligament balancing in TKR

Grade 1 release

Grade 2a release

Grade 2A

Grade 2b release

• Grade 2b release

Posterior part tight in

extensionAnterior part

tight in flexion

Grade 3 release

• Grade 2a + 2b

Grade 4 release

Valgus deformity• Osteophytes

• Lateral capsule

• Iliotibial band - Tight in extension

• Popliteus – Tight in flexion

• LCL

Pie crusting

Flexion contracture

• Osteophytes

• Posterior capsule

• Gastrocnemius ( Medial and lateral head)

• Inreased distal femoral cut

Saggital plane balancing

• Mc Pherson’s rule

Symmetric gap – address tibia

Asymmetric gap – address femur

Tight in Extension Tight in flexion

Symmetric gap Cut more tibia

Loose in Extension Loose in Flexion Symmetric gap

•Thicker poly •Tibial Metal augmentation

Extension good

Loose in flexion

Asymmetric gap

1. Increase size femoral component

2. Translate femoral component posterior

3. Use thicker poly and readdress as tight extension gap

Extension Tight

Flexion Good

Asymmetric Gap 1. Cut more distal femur

2. Release posterior capsule

Extension Good

Flexion Tight

Asymmetric gap 1. Decrease femoral component size

2. Recess PCL

3. Check slope of tibia

Extension Loose

Flexion Good

Asymmetric gap 1. Distal femoral augmentation

2. Decrease femoral component size and thicker poly

Patellofemoral Alignment

• Most common complication

• Maintain Q angle

• Proper component rotation

• Maintain normal patellofemoral tension

• Maintain Q angle

Avoid 1. Int rotn fem

component2. Medial rotn fem

component3. Int rotn tibia4. Patella prosthesis

lateral rotn

Femoral component rotation

• Ap Axis ( whiteside line)• Transepicondylar axis• Post condylar axis• Tibial alignment axis• Gap balance

Tibial component

• Int rotn tibia – increased Q angle

Patellar component

• Centre or medialized

• Avoid lateralizing

• Increases Q angle and cause patella maltracking

Patella Baja

• Patellar component superior

• Lower joint line

• Transfer tibial tubercle cephalad

• Patellectomy

Patella resurfacing vs non resurfacing

• Resurfacing

– Component loosening– Clunk– Fracture– AVN

• Non resurfacing

– Anterior knee pain– May require second

resurfacing

Patellar resurfacing Vs non resurfacing - Evidence

• Metal backed patella higher complications

• Patellar replacement does not gurantee painless Patellofemoral joint

• No significant benefit of patellar replacement

Complication

• Femoral notch

Saw cuts into anterior femoral cortexIncreases chance of periprosthetic fracture

Femoral stem extension

Complication

Peroneal Nerve palsy ( .3 to 2 %)

Pre op Flexion and Valgus Tourniquete time > 120 min.Epidural anaesthesia post opAberrant retractor placement

EMG & NCV at 3 months

Nerve decompression at 3 months

Complication

• Vascular complication ( <.17% - .2%)

• Risk factor– Sharp dissection– Posterior retractor placement– Pre existing vascular disease

– Immediate vascular repair

Complication

• Extensor mechanism rupture ( .17% - 2.5% )

– Direct repair with suture - < 30 % avulsion

– Primary repair and augment with graft

– Allograft repair

Complication

• Stiffness– Flexion contracture 10 – 15 % deg– Flexion < 90 deg

• Treatment– Manipulation under Anaesthesia– Arthroscopic lysis of adhesion– Revision TKR

Complication

• Hypersensitivity Rare ( nickel)

• Patch testing • Lymphocyte transformation test

• Revise to non allergic metal prosthesis

Summary

• Choose correct pt

• Plan properly

• Adequate exposure

• Follow principles to align and balance knee

• Meticulous closure

Hope for the best because 20 % of pt. with well performed TKR are not happy !!

Post Operative Rehabilitation– Rapid post-operative mobilization

• Range of motion exercises started• CPM• Passive extension by placing pillow under foot• Flexion- by dangling the legs over the side of

bed• Muscle strengthening exercises• Weight bearing is allowed on first post op day

Prosthesis Survival

Different studies shows different results

• Ranawat et al (Clin Orthop Relat Res ) 95% at 15 years

91% at 21 years• Gill and Joshi (Am J Knee Surg) 96% at 15 years 82% at 23 years• Font-Rodriguez (Clin Orthop Relat Res )

98% at 14 years

• The technique involves the attachment of active or passive trackers on femur and tibia, which are then tracked by a computer-assisted camera.

• Computer gives real-time feedback about alignment of bony cuts in all three anatomic planes, which allows surgeon to make changes and to measure the accuracy of the bony cuts.

• Computer navigation systems also can aid in determin ing the proper implant size as well as alignment. Soft tissue balancing and measurement of flexion and extension gaps during the procedure are other significant advantages to computer-assisted TKA.

• Objective measurement of the gaps ensures proper soft tissue balancing and gaps that will provide a stable joint throughout a range of motion.

• Another advantage of computer navigation is avoidance of violation of the femoral intramedullary canal, which may reduce blood loss and cardiac-related complications because fewer emboli are placed into the venous system than with placement of an intramedullary alignment rod.

Questions in exams ??Long Question?1) Describe in detail about the kinematics of knee and

enumerate the indications, procedure and complications of TKR

Short Questions? 1) Approaches for TKR 2) Hi flexion type implant in TKR 3) Computer assisted technology for TKR 4) Complications post TKR