Updated: 5/14/2018

TKA Sagittal Plane Balancing

Topic
Review Topic
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0
Questions
19
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0
Evidence
18
0
0
Videos
1
Cases
2
Techniques
3
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Introduction
  • 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.  
    • 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
  • General Rules    
    • adjust femur if asymmetric  
      • distal femur cut affects extension gap
      • posterior femur cut affects flexion gap
    • adjust tibia if problem is symmetric (same in both flexion and extension)
      • tibia cut affects both flexion and extension gap
    • remember increasing/decreasing the size of the femoral component only changes the AP diameter and therefore affects the flexion gap only.  
 Evaluation & Treatment
  •  The following chart shows different conditions found with the trials in place and the treatment strategy for each condition.
  Tight in Flexion
(can not fully flex)  
Balanced in
Flexion
 
Loose in Flexion
(large drawer test) 
Tight in Extension (can not fully extend)
 
Tight in Extension, Tight in Flexion

Problem:
Did not cut enough tibia
Solution:
Cut more proximal tibia 
Tight in Extension, Balanced in Flexion
 Problem:
Did not cut enough distal femur or did not release enough posterior capsule 
Solution:
1) Release posterior capsule 
2) Cut more distal femur
  
Tight in Extension, Loose in Flexion

 Problem:
Distal femur too long.
Solution:
1) Resect more distal femur or use thinner distal femoral augmentation wedge (revision scenario)
2) Upsize femoral component 
Balanced  in Extension
 
Balanced in Extension, Tight in Flexion
 
Problem: 
Did not cut enough posterior femur, PCL scarred and too tight.
Solution: 
1) Decrease femoral component size which required an increase in resection of the posterior femoral condyle Recess vs. release of PCL Release posterior capsule Decrease femoral component size which required an increase in resection of the posterior femoral condyle
2) Recess vs. release of PCL
3) Release posterior capsule
Solution: 
1) Decrease femoral component size which required an increase in resection of the posterior femoral condyle
2) Recess vs release of PCL
3) Release posterior capsule
4) Recut proximal tibia with increased slope

Balanced in extension, Balanced in Flexion (Perfect)
Balanced in Extension, Loose in Flexion
  
 Problem: 
Cut too much posterior femur.
Solution:
1) Increase size of femoral component (AP only)
2) Posteriorize femoral component (augment posterior femur). 
Loose in Extension
 (recurvatum)
 
Loose in Extension, Tight in Flexion

 Solution:
1) Downsize femur and use thicker tibial insert until balanced. 

Loose in Extension, Balanced in Flexion
 Problem:
 Cut too much distal femur.
Solution:
 1) Augment distal femur 
Loose in Extension, Loose in Flexion
 Problem:
Cut too much tibia.
Solution:
1) Use thicker tibia PE
2) Add medial & lateral metal augments to tibial tray


 

 

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Technique Guides (3)
Questions (19)
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(SBQ07HK.2) A 66-year-old male is undergoing a total knee arthroplasty using a fixed bearing posterior stabilized component. During intraoperative trialing of the components it is noted that the flexion gap is loose, and extension gap is appropriate. If this is not corrected, what post-operative complication is this patient most at risk of having? Review Topic

QID: 1587
1

Spin out of the polyethylene

14%

(244/1746)

2

Periprosthetic fracture

1%

(9/1746)

3

Posterior knee dislocation

77%

(1342/1746)

4

Osteolysis

6%

(102/1746)

5

Patellar instability

3%

(44/1746)

ML 2

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PREFERRED RESPONSE 3

(OBQ06.165) During trialing for a cruciate-sacrificing total knee arthroplasty, the surgeon notes an imbalance between the flexion and extension gaps with significant flexion instability. The extension gap is well balanced. Which of the following options is the best intra-operative solution? Review Topic

QID: 351
1

Downsize the femoral component

2%

(48/1990)

2

Downsize the tibial component

0%

(6/1990)

3

Upsize the femoral component and add posterior augments

94%

(1878/1990)

4

Upsize the tibial component

2%

(30/1990)

5

Move the femoral component more anteriorly

1%

(20/1990)

ML 1

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PREFERRED RESPONSE 3
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(OBQ04.182) During a primary total knee arthroplasty, trial of components demonstrates a knee that is balanced in flexion and loose in extension. Which of the following will balance the flexion and extension gap? Review Topic

QID: 1287
1

Distal femur resection only

1%

(28/2025)

2

Distal femur augmentation and use of the same size polyethylene

91%

(1833/2025)

3

Downsize femoral component and use a thinner polyethylene insert

1%

(21/2025)

4

Proximal tibia resection only

1%

(16/2025)

5

Distal femur augmentation and thicker polyethylene insert

6%

(115/2025)

ML 1

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PREFERRED RESPONSE 2

(OBQ10.248) When performing a total knee arthroplasty using intramedullary referencing, the knee is stable at full extension, but it will not flex past 90 degrees. Which of the following adjustments can achieve satisfactory range of motion and stability in flexion and extension? Review Topic

QID: 3347
1

Downsizing the tibial insert

4%

(122/3300)

2

Placing posterior femoral augments

1%

(33/3300)

3

Resecting more distal femur

7%

(237/3300)

4

Downsizing the femoral component

87%

(2886/3300)

5

Performing a medial tibial reduction osteotomy

0%

(13/3300)

ML 1

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PREFERRED RESPONSE 4

(OBQ06.171) During trialing for a cruciate-retaining total knee arthroplasty, the surgeon is unable to fully extend the knee and is left with a 15 degree flexion contracture. The flexion gap is well balanced. Which of the following options will create a knee that is balanced in both flexion and extension? Review Topic

QID: 357
1

Recess the PCL

5%

(102/1968)

2

Increase the tibial slope

2%

(35/1968)

3

Decrease the size of the femoral component

4%

(74/1968)

4

Resect more distal femur

86%

(1688/1968)

5

Resect more proximal tibia

3%

(65/1968)

ML 1

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PREFERRED RESPONSE 4

(OBQ09.153) While performing a revision total knee arthroplasty, the surgeon decides to upsize the femoral component with use of posterior femoral augments. Which of the following intraoperative exam findings would have led to this decision? Review Topic

QID: 2966
1

A knee that is balanced in extension and tight in flexion.

1%

(24/1925)

2

A knee that is balanced in extension and loose in flexion.

92%

(1773/1925)

3

A knee that is tight in extension and tight in flexion.

1%

(12/1925)

4

A knee that is loose in extension and loose in flexion.

3%

(59/1925)

5

A knee that is loose in extension and balanced in flexion.

3%

(52/1925)

ML 1

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PREFERRED RESPONSE 2

(OBQ09.57) After insertion of the trial components in a total knee replacement, the surgeon finds that he is unable to fully extend the knee and that the tibial tray lifts-off when the knee is flexed past 90 degrees. What intervention should be taken to achieve a knee that is balanced in flexion and extension? Review Topic

QID: 2870
1

Augment the distal femur

1%

(17/3005)

2

Resect more distal femur

9%

(280/3005)

3

Resect more proximal tibia

84%

(2529/3005)

4

Downsize the femoral component

5%

(161/3005)

5

Increase polyethylene liner thickness

0%

(13/3005)

ML 2

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PREFERRED RESPONSE 3

(OBQ08.208) A patient comes to the office with a flexion contracture following a total knee arthroplasty that has resulted in an unsatisfactory outcome. Intraoperative examination also reveals the knee is loose in flexion. What steps should be included in the revision surgery? Review Topic

QID: 594
1

Increase the polyethylene liner thickness

3%

(109/3234)

2

Resect additional tibia

2%

(51/3234)

3

Anteriorly translate the femoral component and decrease polyethylene thickness

3%

(93/3234)

4

Resect additional distal femur and tibia

1%

(17/3234)

5

Resect additional distal femur and upsize the femoral component

91%

(2943/3234)

ML 1

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PREFERRED RESPONSE 5

(OBQ07.247) While trialing components during a routine total knee arthroplasty, the flexion gap is felt to be loose and the extension gap is stable. Which of the following are possible ways to treat this intraoperative instability? Review Topic

QID: 908
1

Move the femoral component posterior

85%

(835/984)

2

Increase the size of the polyethylene component

4%

(43/984)

3

Downsize the femoral component

2%

(22/984)

4

Move the femoral component anterior and augment the distal femur

7%

(73/984)

5

Externally rotate both the femoral component and tibial components

0%

(4/984)

ML 2

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PREFERRED RESPONSE 1

(OBQ05.223) A 62-year-old woman is undergoing a revision total knee arthroplasty for aseptic component loosening. The surgeon has all the trial components in place and recognizes that the soft tissues are balanced in the coronal plane, but the knee is 10 degrees from reaching full extension. He proceeds to correct the contracture by making an additional 2mm cut off of the tibia and is successful in achieving full extension. What is the most likely effect of this additional resection? Review Topic

QID: 1109
1

Loss of full flexion

1%

(10/845)

2

Flexion instability

92%

(781/845)

3

Extension instability

5%

(40/845)

4

Valgus instability

1%

(5/845)

5

Varus instability

0%

(2/845)

ML 1

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PREFERRED RESPONSE 2

(OBQ07.195) A 62-year-old man undergoes total knee arthroplasty. Preoperative radiographs are shown in Figure A. Following bone resections and placement of trial implants, the knee is stable in flexion, but cannot achieve full extension. Which of the following interventions will most likely result in a knee that is balanced in flexion and extension? Review Topic

QID: 856
FIGURES:
1

Resect more distal femur

91%

(1388/1518)

2

Resect more distal femur and downsize the femoral component

3%

(50/1518)

3

Resect more proximal tibia

3%

(40/1518)

4

Decrease polyethelene liner thickness

2%

(31/1518)

5

Place posterior femoral augments

0%

(6/1518)

ML 1

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PREFERRED RESPONSE 1

(OBQ07.190) During total knee replacement with the trial components in place, the knee achieves full extension but experiences tightness in flexion with a range to only 90 degrees. What is the most appropriate action? Review Topic

QID: 851
1

Resect more proximal tibia

2%

(25/1021)

2

Downsize the femoral component

87%

(887/1021)

3

Addition of a distal femoral augment

1%

(14/1021)

4

Downsize the tibial polyethylene insert

5%

(46/1021)

5

Resect more distal femur

5%

(46/1021)

ML 1

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PREFERRED RESPONSE 2

(OBQ08.202) During total knee arthroplasty, an excessive posterior femoral resection will lead to which of the following scenarios? Review Topic

QID: 588
1

Loose extension and flexion gaps

1%

(24/2988)

2

Loose extension gap

2%

(70/2988)

3

Loose flexion gap

96%

(2856/2988)

4

Tight flexion gap

1%

(17/2988)

5

Tight extension gap

0%

(8/2988)

ML 1

Select Answer to see Preferred Response

PREFERRED RESPONSE 3
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