Sagittal Plane (gap) Balancing

Author: Derek Moore

Topic updated on 02/17/13 8:50am

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 does not affect the height of the prosthesis.

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 size of femoral component 2) Recess & release PCL 3) Resect posterior slope in tibia 4) Resect more posterior femoral condyle 5) Release posterior capsule	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) Use thicker tibial metal insert

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Qbank (13 Questions)

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(SBQ07.2) 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 at risk of having? Topic

Review Topic

1. Spin out of the polyethylene
2. Periprosthetic fracture
3. Posterior knee dislocation
4. Osteolysis
5. Patellar instability

PREFERRED RESPONSE ▶

DISCUSSION: A posteriorly stabilized knee has a post built into the polyethylene bearing that articulates with the box of the femoral component in flexion to act as a cam mechanism. If the knee is too loose in flexion, it is possible for the femoral component to "jump the post", causing a posterior dislocation.

Clarke and Scuderi review flexion instability as a mode of failure in knee replacements. They describe how this is usually due to lack of adequate balance at the time of surgery. They also report that revision surgery is usually the only way to correct symptomatic flexion instability.

REFERENCES:

1. Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 339-365.

2. Lotke PA, Garino JP: Revision Total Knee Arthroplasty. New York, NY, Lippincott-Raven, 1999, pp 173-186, 227-249.

3. Clarke HD, Scuderi GR: Flexion instability in primary total knee replacement. J Knee Surg 2003;16:123-128. PMID:12741427 (Link to Abstract)

Question Authors:

Dave Marcu MD, John Badylak MD, Michael Hughes MD,

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(OBQ10.248) When performing a total knee arthroplasty, 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? Topic

Review Topic

1. Downsizing the tibial insert
2. Placing posterior femoral augments
3. Resecting more distal femur
4. Downsizing the femoral component
5. Performing a medial tibial reduction osteotomy

PREFERRED RESPONSE ▶

DISCUSSION: Balancing flexion and extension gaps in knee arthroplasty can be a challenge, especially in a revision setting. For a TKA to achieve greater flexion, options include downsizing the femoral component, recessing the PCL, and increasing the posterior tibial slope. More flexion can also be achieved by resecting more tibia or decreasing the height of the tibial insert; however, changes to the tibial side affect both the flexion and extension gaps. With regards to this question, downsizing the tibial insert would increase both the flexion and extension gaps; the knee would be unstable in extension. Placing augments on the posterior femur would make the flexion gap even tighter. Resection of more distal femur would loosen the extension gap without changing flexion. Tibial reduction osteotomy on the medial side would result in more laxity to valgus stress, but it would not symmetrically increase the flexion gap. The paper by Dennis et al. is a review of revision knee arthroplasty, in which there is complete discussion of gap balancing techniques. The technique paper by Ries et al. covers only balancing in revision total knee arthroplasty.

REFERENCES:

1. Dennis DA, Berry DJ, Engh G, Fehring T, MacDonald SJ, Rosenberg AG, Scuderi G. Revision total knee arthroplasty. J Am Acad Orthop Surg. 2008 Aug;16(8):442-54. PMID:18664633 (Link to Abstract)

2. Ries MD, Haas SB, Windsor RE. Soft-tissue balance in revision total knee arthroplasty. Surgical technique. J Bone Joint Surg Am. 2004 Mar;86-A Suppl 1:81-6. PMID:14996925 (Link to Abstract)

Question Authors:

Dave Marcu MD,

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(OBQ09.57) After insertion of 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 in flexion greater than 90 degrees. What intervention should be taken to acheive a knee that is balanced in flexion and extension? Topic

Review Topic

1. Augment the distal femur
2. Resect more distal femur
3. Resect more proximal tibia
4. Downsize the femoral component
5. Increase polyethylene liner thickness

PREFERRED RESPONSE ▶

DISCUSSION: This patient is tight in extension (flexion contracture, inability to fully extend the knee) and tight in flexion (lift-off in deep flexion). Resecting additional tibia helps for both flexion and extension tightness (answer 3). Likewise, another acceptable answer would be to decrease the polyethylene thickness (not increase the thickness as given in answer 5). Augmenting the distal femur (answer 1) will worsen the flexion contracture. Resecting distal femur alone (answer 2) will only help the extension tightness, but not address the flexion tightness. Downsizing the femoral component alone will only help the flexion tightness (answer 4), but not address the tightness in extension.

REFERENCES:

1. Fischgrund JS (ed): Orthopaedic Knowledge Update 9. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2008, pp 457-471

Question Authors:

Doug Nowak MD,

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(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? Topic

Review Topic

1. A knee that is balanced in extension and tight in flexion.
2. A knee that is balanced in extension and loose in flexion.
3. A knee that is tight in extension and tight in flexion.
4. A knee that is loose in extension and loose in flexion.
5. A knee that is loose in extension and balanced in flexion.

PREFERRED RESPONSE ▶

DISCUSSION: Increasing the size of the femoral component posteriorly will balance a flexion-extension mismatch where the knee is loose in flexion and stable/balanced in extension. The referenced article by Peters discusses multiple different soft tissue balancing techniques used for trialing scenarios as well as for varus or valgus instability, and knees with flexion contractures. A knee tight or loose on both flexion and extension can be corrected by decreasing or increasing the size of the polyethylene, respectively. A knee that is tight in flexion/balanced in extension can be corrected by decreasing the AP diameter of the femoral component.

REFERENCES:

1. Peters CL. Soft-tissue balancing in primary total knee arthroplasty. Instr Course Lect. 2006;55:413-7. Review. PMID:16958476 (Link to Abstract)

Question Authors:

John Badylak MD,

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

Review Topic

1. Loose extension and flexion gaps
2. Loose extension gap
3. Loose flexion gap
4. Tight flexion gap
5. Tight extension gap

PREFERRED RESPONSE ▶

DISCUSSION: Illustration A shows the flexion and extension gaps that occur during TKA. Cutting too much posterior femur will lead to a gap mismatch, with a larger flexion gap than extension gap. This creates laxity in knee flexion. If the distal femur is cut too aggressively, extension gap instability would occur. Over-resection of the proximal tibia leads to a balanced gap issue, with need for increased tibial polyethylene thickness to replace the resected bone.

The referenced study by Clarke and Scuderi is a review article of flexion instability in total knee arthroplasty; this article covers diagnosis and treatments of scenarios such as seen in this question.

Illustrations: A

REFERENCES:

1. Clarke HD, Scuderi GR. Flexion instability in primary total knee replacement. J Knee Surg. 2003 Apr;16(2):123-8. Review. PMID:12741427 (Link to Abstract)

Question Authors:

Ben Taylor MD, John Badylak MD, Michael Hughes MD,

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(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? Topic

Review Topic

1. Increase the polyethylene liner thickness
2. Resect additional tibia
3. Anteriorly translate the femoral component and decrease polyethylene thickness
4. Resect additional distal femur and tibia
5. Resect additional distal femur and upsize the femoral component

PREFERRED RESPONSE ▶

DISCUSSION: This patient has two problems: 1) loose in flexion (flexion laxity); 2) tight in extension (flexion contracture). Both of these should be addressed in surgery. In order to address the flexion instability, the surgeon can either upsize the femoral component or posteriorly translate the femoral component. Increasing the poly thickness will help the flexion instability, but worsen the tightness in extension. In order to address the extension tightness, the surgeon can downsize the poly insert, resect additional tibia, or resect additional distal femur. Downsizing the poly and resecting additional tibia, however, will both result in increased flexion instability. Resecting additional distal femur only affects the extension gap. Thus, the correct answer is upsizing the femoral component and resecting additional femur.

REFERENCES:

1. Vail TP, Lang JE: Surgical techniques and instrumentation in total knee arthroplasty, in Scott WN (ed): Surgery of the Knee, ed 4. Philadelphia, PA, Churchill Livingstone, 2006, pp 1553-1621

2. Callaghan JJ, Rosenberg AG, Rubash HE, et al: The Adult Knee. Philadelphia, PA, Lippincott Williams & Wilkins, 2003, pp 1217-1223

Question Authors:

Doug Nowak MD, Guillem Lomas MD, John Badylak MD,

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

Review Topic

1. Resect more proximal tibia
2. Downsize the femoral component
3. Addition of a distal femoral augment
4. Downsize the tibial polyethylene insert
5. Resect more distal femur

PREFERRED RESPONSE ▶

DISCUSSION: This question is stating that a total knee trial is balanced in extension, but tight in flexion. Downsizing the femoral component increases the flexion gap without changing the extension gap. This allows for more flexion without affecting extension. Additional distal femoral resection will create a larger extension gap without affecting the flexion gap. Reducing the thickness of the tibial insert or resecting more tibia would increase both the extension and flexion gaps.

Manson et al review sagittal plane balancing techniques specifically focusing on the differences between posterior condylar referencing guides and anterior femoral referencing guides.

Illustration A depicts the gap changes associated with increasing or decreasing the femoral component size (smaller AP size as seen in Drawing B of the illustration) leads to a larger flexion gap and unchanged extension gap.

Illustrations: A

REFERENCES:

1. Manson TT, Khanuja HS, Jacobs MA, Hungerford MW. Sagittal plane balancing in the total knee arthroplasty. J Surg Orthop Adv. 2009 Summer;18(2):83-92. PMID:19602336 (Link to Abstract)

Question Authors:

John Badylak MD, Derek Moore, Michael Hughes MD,

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(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? Topic

Review Topic

FIGURES: A

1. Resect more distal femur
2. Resect more distal femur and downsize the femoral component
3. Resect more proximal tibia
4. Convert to a mobile-bearing total knee design
5. Place posterior femoral augments

PREFERRED RESPONSE ▶

DISCUSSION: The radiograph demonstrates a varus osteoarthritic knee suitable for a standard total knee arthroplasty. In this scenario, the knee is balanced in flexion, but tight in extension. Resecting more distal femur opens up the extension gap without changing the flexion gap resolving the problem. Resecting more tibia alters both extension and flexion gaps and would cause laxity in flexion. Downsizing the femoral component opens up the flexion gap and would also cause laxity in flexion. Converting to a mobile bearing knee would have no effect on balancing the extension and flexion gaps. Placing posterior femoral augments would tighten the flexion gap and have no effect on the extension gap. Please see the excellent table in the review topic link for a full description of sagittal gap balancing for all combinations of flexion/extension mismatch.

REFERENCES:

1. Beaty, J. Orthopaedic Knowledge Update 6. American Academy of Orthopaedic Surgeons. Rosemont, IL. 1998. pp:513-536.

Question Authors:

John Badylak MD,

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(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? Topic

Review Topic

1. Move the femoral component posterior
2. Increase the size of the polyethylene component
3. Downsize the femoral component
4. Move the femoral component anterior and augment the distal femur
5. Externally rotate both the femoral component and tibial components

PREFERRED RESPONSE ▶

DISCUSSION: Flexion and extension gaps during TKA must be balanced to provide a knee that is stable throughout its range of motion. Changes to the tibia, such as modifying the size of the polyethylene insert, affect both the flexion gap and the extension gap. Conversely, changes to the femur typically affect either the flexion gap or the extension gap, but not both. Moving the femoral component anterior or posterior increases or decreases the flexion gap respectively. In a similar manner, moving the femoral component proximally or distally increases or decreases the extension gap respectively. In this question, the patient is loose in flexion and stable in extension. This can be addressed by either moving the femoral component posterior, or upsizing the femoral component which will only increase the AP diameter of the prosthesis. Therefore, answer 1 is correct.

Whiteside et al is a review article that discusses the proper techniques that results in a knee that is balanced to varus and valgus stresses in flexion and extension.

REFERENCES:

1. Whiteside LA., Soft tissue balancing: the knee. J Arthroplasty 2002 Jun;17(4 Suppl 1):23-7. PMID:12068398 (Link to Abstract)

Question Authors:

John Badylak MD, John Badylak MD, Ben Taylor MD,

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(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? Topic

Review Topic

1. Downsize the femoral component
2. Downsize the tibial component
3. Upsize the femoral component and add posterior augments
4. Upsize the tibial component
5. Move the femoral component more anteriorly

PREFERRED RESPONSE ▶

DISCUSSION: Understanding flexion/extension gaps in total knee arthroplasty is paramount to patient success. Treatment for flexion instability consists of either increasing the size of the femoral component, shifting the femoral component posteriorly, or increasing the size of the polyethylene and then dealing with the tight extension gap. As discussed by Ries et al, increasing the size of the femoral component will change the anterior/posterior size of the component without changing the proximal/distal size of the component, thus changing only the flexion gap. With upsizing the femoral component, you will likely have to add augments as the bone cut will not match a larger component. Moving the femoral component more posterior will accomplish the same goal of decreasing only the flexion gap. Increasing the tibial size will change both the flexion and extension gaps, and in this patient, the surgeon would then have to address the tight extension gap by resecting more distal femur and/or releasing the posterior capsule.

REFERENCES:

1. Ries MD, Haas SB, Windsor RE. Soft-tissue balance in revision total knee arthroplasty. Surgical technique. J Bone Joint Surg Am. 2004 Mar;86-A Suppl 1:81-6. PMID:14996925 (Link to Abstract)

Question Authors:

Patrick O'Donnell MD/PhD,

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(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? Topic

Review Topic

1. Recess the PCL
2. Increase the tibial slope
3. Decrease the size of the femoral component
4. Resect more distal femur
5. Resect more proximal tibia

PREFERRED RESPONSE ▶

DISCUSSION: Flexion/extension gap balancing is crucial to the success in total knee arthroplasty. The inability to achieve full extension suggests extension tightness. This can be improved by either resecting more distal femur or releasing the posterior capsule from the femoral insertion. While resecting more proximal tibia will improve the extension gap, it will loosen the flexion gap and require either upsizing of the femoral component with placement of posterior augments or translation of the femoral component posteriorly. Recessing the PCL and increasing the tibial slope would be appropriate for flexion not extension tightness. In their review, Ries et al discuss flexion/extension balancing, focusing on revision total knee arthroplasty.

REFERENCES:

1. Ries MD, Haas SB, Windsor RE. Soft-tissue balance in revision total knee arthroplasty. Surgical technique. J Bone Joint Surg Am. 2004 Mar;86-A Suppl 1:81-6. PMID:14996925 (Link to Abstract)

Question Authors:

Patrick O'Donnell MD/PhD,

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(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? Topic

Review Topic

1. Loss of full flexion
2. Flexion instability
3. Extension instability
4. Valgus instability
5. Varus instability

PREFERRED RESPONSE ▶

DISCUSSION: This patient presents with asymmetric gapping because she is tight in extension and balanced in flexion. Ries discusses that resection of the proximal tibia in this situation is a common pitfall in surgical technique as it “will resolve the flexion contracture but produce instability in flexion”. The preferred method of restoring the distal femoral joint line to achieve full extension and maintain flexion stability is to cut “more of the distal part of the femur, as this will not affect the flexion space”. Similarly, there is an asymmetric gap if full extension is achieved, but flexion is limited. The lack of full flexion can be treated with distal femoral augments and a thinner tibial insert.

REFERENCES:

1. Reis MD, Haas SB, Windsor RE: Soft-tissue balance in revision total knee arthroplasty: Surgical Technique. J Bone Joint Surg Am 2004;86:81-86 PMID:12540668 (Link to Abstract)

Question Authors:

Michael Hughes MD, John Badylak MD,

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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? Topic

Review Topic

1. Distal femur resection only
2. Distal femur augmentation and use of the same size polyethylene
3. Downsize femoral component and use a thinner polyethylene insert
4. Proximal tibia resection only
5. Distal femur augmentation and thicker polyethylene insert

PREFERRED RESPONSE ▶

DISCUSSION: The goal in sagittal balancing of TKA is to obtain a gap that is equal in flexion and extension. General principles to remember: 1. Changing the distal femur only affects extension, 2. Changing the femoral component size only affects flexion, and 3. Changing the proximal tibia/polyethylene insert affects both extension and flexion. In the above scenario, distal femoral augmentation will correct the "looseness in extension" without changing the "balanced flexion". The above principles are reviewed by Ries et al along with soft tissue balancing principles for stability in the coronal plane.

REFERENCES:

1. Ries MD, Haas SB, Windsor RE. Soft-tissue balance in revision total knee arthroplasty. J Bone Joint Surg Am. 2003;85-A Suppl 1:S38-42. PMID:12540668 (Link to Abstract)

Question Authors:

John Badylak MD, Derek Moore,

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Groups

ABOS II: Sagittal Plane (gap) Balancing

General - Oral Boards Review

7/29/2011

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Evidence & References Show References

Level of Evidence 5 and Other Journal Articles (includes Case Reports, Expert Opinions, Personal Observations, and Biomechanic Studies)

Clarke HD, Scuderi GR. Flexion instability in primary total knee replacement. J Knee Surg. 2003 Apr;16(2):123-8. Review. PMID:12741427 (Link to Abstract)
Clarke HD, Scuderi GR: Flexion instability in primary total knee replacement. J Knee Surg 2003;16:123-128. PMID:12741427 (Link to Abstract)
Manson TT, Khanuja HS, Jacobs MA, Hungerford MW. Sagittal plane balancing in the total knee arthroplasty. J Surg Orthop Adv. 2009 Summer;18(2):83-92. PMID:19602336 (Link to Abstract)
Peters CL. Soft-tissue balancing in primary total knee arthroplasty. Instr Course Lect. 2006;55:413-7. Review. PMID:16958476 (Link to Abstract)
Reis MD, Haas SB, Windsor RE: Soft-tissue balance in revision total knee arthroplasty: Surgical Technique. J Bone Joint Surg Am 2004;86:81-86 PMID:12540668 (Link to Abstract)
Ries MD, Haas SB, Windsor RE. Soft-tissue balance in revision total knee arthroplasty. Surgical technique. J Bone Joint Surg Am. 2004 Mar;86-A Suppl 1:81-6. PMID:14996925 (Link to Abstract)

Textbooks

Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009
Orthopaedic Knowledge Update 10, John M Flyn. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2011
Hoppenfeld SP. Surgical Exposures in Orthopaedics: The Anatomic Approach. Lipponcott, Williams, and Wilkins, Philadelphia, PA, Copyright 2009
Orthopaedic In-training Examination (OITE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Self-Assessment Examination (SAE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Beaty, J. Orthopaedic Knowledge Update 6. American Academy of Orthopaedic Surgeons. Rosemont, IL. 1998. pp:513-536.
Lotke PA, Garino JP: Revision Total Knee Arthroplasty. New York, NY, Lippincott-Raven, 1999, pp 173-186, 227-249.
Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 339-365.

Undefined

Bellemans J, Vandenneucker H, Victor J, Vanlauwe J. Flexion contracture in total knee arthroplasty.Clin Orthop Relat Res. 2006 Nov;452:78-82. PMID:16924174 (Link to Abstract)
Callaghan JJ, Rosenberg AG, Rubash HE, et al: The Adult Knee. Philadelphia, PA, Lippincott Williams & Wilkins, 2003, pp 1217-1223
Dennis DA, Berry DJ, Engh G, Fehring T, MacDonald SJ, Rosenberg AG, Scuderi G. Revision total knee arthroplasty. J Am Acad Orthop Surg. 2008 Aug;16(8):442-54. PMID:18664633 (Link to Abstract)
Fischgrund JS (ed): Orthopaedic Knowledge Update 9. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2008, pp 457-471
Ries MD, Haas SB, Windsor RE. Soft-tissue balance in revision total knee arthroplasty. J Bone Joint Surg Am. 2003;85-A Suppl 1:S38-42. PMID:12540668 (Link to Abstract)
Vail TP, Lang JE: Surgical techniques and instrumentation in total knee arthroplasty, in Scott WN (ed): Surgery of the Knee, ed 4. Philadelphia, PA, Churchill Livingstone, 2006, pp 1553-1621
Whiteside LA., Soft tissue balancing: the knee. J Arthroplasty 2002 Jun;17(4 Suppl 1):23-7. PMID:12068398 (Link to Abstract)

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Sagittal Plane (gap) Balancing

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