Whiteside - Ligament Balancing

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Ligament Balancing

in Total Knee Arthroplasty

An Instructional Manual

Springer


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Ligament BalancingIn Total Knee Arthroplasty

An Instructional Manual

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LEO A. WHITESIDE

Ligament Balancing in

Total Knee ArthroplastyAn Instructional Manual

With 193 Figures

Springer

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LEO A. WHITESIDE,M.D. Missouri

Bone and Joint Center

Biomechanical Research

Laboratory 14825 Sugarwood Trail

St. Louis, MO 63014 USA

1st ed. 2004. 2nd printing 2005.

ISBN-10 3-540-20749-X Springer-Verlag Berlin Heidelberg New York

ISBN-13 978-3-540-20749-8 Springer-Verlag Berlin Heidelberg New

York

Cataloging-in-Publication Date applied for

Ligament Balancing in Total Knee Arthroplasty - An Instructional Manual, L.A. Whiteside

Berlin; Heidelberg; New York; Hong Kong; London; Milan; Paris; Tokyo; Springer, 2004

ISBN 3-540-20749-X

This work is subject to copyright. All rights are reserved, whether the whole or part of thematerial is concerned, specifically (he rights of translation, reprinting, reuse of illustrations,recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data

banks. Duplication of this publication or parts thereof is permitted only under the provisionsof the German Copyright Law of September 9, 1965, in its current version, and permission foruse must always be obtained from Springer-Verlag. Violations are liable for prosecution underthe German Copyright Law.

Springer-Verlag Berlin Heidelberg New York 2004Springer-Verlag is a part of Springer Science+BusinessMedia springeronlin. m Printed in Germany

Product liability: The publisher cannot guarantee the accuracy of any information aboutdosage and application contained in this book. In every individual case the user must checksuch information by consulting the relevant literature.

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Leo A. Whiteside, M.D.Missouri Bone and Joint

CenterBiomechanical ResearchLaboratory 14825 Sugarwood TrailSt Louis, MO 63014

USA

About the Author

Dr. Leo Whiteside, an internationally known orthopaedicsurgeon-inventor and educator from St. Louis, Missouri, isrecognized as one of the world's foremost authorities onosteointegration technology in total knee and hiparthroplasty. In the early 1980s he pioneered one of the firstsuccessful cementless total knee systems along with the firstintramedullary alignment instrumentation system for kneesurgery. He has designed three total hip systems, two total

knee systems, and a unicondylar knee system. In the pastdecade he has dedicated much of his research effort toligament balancing techniques in knee arthroplasty. Aftercollecting and comparing extensive cadaveric laboratory andsurgical-clinical data, he has developed protocols for

balancing ligaments in primary and revision knees. Asdirector of the Missouri Bone and Joint Center and itsaffiliated research foundation, Dr. Whiteside has publishedapproximately 200 peer-reviewed journal articles and bookchapters. He also serves on numerous orthopaediccommittees and journal review boards.


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Preface

Ligament balancing is an integral part of total knee arthroplasty, and remains thought -provoking and controversial years after alignment instrumentation and implants have beenstandardized. Although tensioning instruments have been used to guide the surgeon in bonesurface resection, the compromises in alignment created by these instruments can lead toconfounding problems with wear and patellar tracking.

The basic premise behind this book is that the knee must be both correctly aligned andbalanced throughout the arc of flexion. In order to achieve these results the procedures mustbe accurate but also simple and quick to perform.

The general principle of alignment and ligament function should be understood thoroughly

before the surgeon enters the operating room. This book was designed to impart a completepicture of how the alignment landmarks and ligament parameters work together, and toprovide methods to address the abnormalities that occur as a result of deformity and ligamentcontracture. To receive the most benefit from this book the surgeon should first read the entire

book to achieve a thorough understanding of the principles of alignment and ligamentbalancing. However, each chapter can be read and understood separately as a guide to -operation planning and as a technique manual in the operating room.

This book began as a surgical technique manual for use by fellows at the Missouri Boneand Joint Center in pre-operative planning and as a guide in the operating room. Because ofdemand for a manual for the orthopaedic surgeon who specializes in arthroplasty, a soft-coveredition was produced in English, and Springer-Verlag published a successful hard-bound

edition in Italian. Now also a German Edition will be printed.I would like to thank Scott Hartsell of Smith & Nephew for helping to start the processrepresented by this book, and for his continued support for surgical education, also toAndreas Hesse who helped to realize the German Edition. Also thanks should go to Springer-Verlag-Heidelberg, especially Thomas Guenther, for continuing to develop this surgicalacademic endeavor.

Leo A. WhitesideMissouri Bone and Joint Center - Biomechanical Research LaboratorySt. Louis in January 2004

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Table of Contents

About the Editor ................................................................................................................ 5

Preface ............................................................................................................................... 6

1. Introduction ....................................................................................................................9

2. Patella .............................................................................................................................23

3. Posterior Cruciate Ligament ..........................................................................................28

3.1. Tight Posterior Cruciate Ligament ......................................................................303.2. Release of the Posterior Cruciate Ligament ........................................................32

4. Varus Knee .....................................................................................................................36

4.1. Tight Medially in Flexion, Loose in Extension ...................................................47

4.2. Tight Medially in Extension, Balanced in Flexion ..............................................50

4.3. Tight Medially in Flexion and Extension ............................................................ 53

4.4. Tight Popliteus Tendon........................................................................................ 57

4.5. Compensatory Lateral Release - Extension Only ................................................ 594.6. Compensatory Lateral Release - Flexion and Extension ..................................... 61

4.7. Pitfalls of the Varus Knee .................................................................................... 63

5. Valgus Knee .................................................................................................................. 675.1. Tight Laterally Flexion and Extension ................................................................ 745.2. Tight Laterally in Extension, Normal Stability in Flexion .................................. 805.3. Tight Laterally in Flexion, Normal Stability in Extension .................................. 835.4. Deficient Posterior Cruciate Ligament ................................................................ 865.5. Pitfalls of the Valgus Knee .................................................................................. 88

5.5.1.Release of Extension-only Stabilizers - Tight in Flexion and Extension ............ 885.5.2.Release of Extension-only Structures - Tight in Flexion and Extension ............ 88

5.5.3.Retaining Lateral Collateral Ligament Cutting Flexion Space Guided byTensioners.915.5.4.Using the Deficient Lateral Condyle as Reference for Bone Resection ............. 94

6. Flexion Contracture and Femoral Sizing ...................................................................... 1006.1. Varus Knee with Flexion Contracture ................................................................. 1026.2. Pitfalls with Flexion Contracture ........................................................................ 108

7. Recurvatum ................................................................................................................... 112

8. Summary ....................................................................................................................... 116

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1. Introduction

Although the knee has been studied intensively for decades, itcontinues to confound investigators and to frustrate surgeons. Itsintricate ligaments and complex joint surfaces interact in ways thatdefy description. Nevertheless, the surgeon must repair andreconstruct the damaged and arthritic knee so that its performanceis near normal, and this requires decisions and adjustments madewith reasonable accuracy under the pressure and time constraintsof the operating room. This book simplifies the geometry and kin-ematics of the knee enough that the knee can be understood and

managed effectively. It establishes rules for resection andalignment that position the joint surfaces so that the ligaments can

be balanced through the normal flexion arc, it illustrates stabilitytests that can be performed with ease, and it teaches safeguidelines for ligament release so that the ligament balancing can

be performed quickly and effectively without destabilizing theknee.

The lowerextremity often isdepicted in twodimensions with the

hip, knee, and anklelying in a straightline, the -epi-condylaraxis perpendicular tothis line, and the jointline sloped downwardmedially.

Fig 1.-The centers of thehip, knee, and ankle lieapproximately in astraight line - themechanical axis of thelower extremity.-The mechanical axisof the femur iscollinear with themechanical axis of thelower extremity.-The long axis of thefemur (the anatomicaxis) aligns in approx-imately 5 valgus the mechanical axis ofthe lower extremity.-The long axis of thetibia is collinear withthe mechanical axis ofthe lower extremity.- The patellar grooveis collinear with themechanial axis of theextremity and

perpendicular to the

epicondylar axis.

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When depicted in three dimensions, the lower extremity functions in a plane

throughout the flexion-extension arc, and the femoral head, the mechani-

cal axis of the femur, the patellar groove, the inter-condylar notch, the pa-

tellar articular crest, the tibia, and the ankle remain within this plane. The

axis through which the tibia rotates as the knee flexes and extends is per-

pendicular to this Median Anterior-Posterior Plane, and is approximatedby the trans-epicondylar line, or epicondylar axis. The patella is drawn

through the patellar groove, which also lies in the anterior-posterior plane.

Fig.2. The mechanicalaxis of the lowerextremity becomes aplane when flexion andextension in threedimensions are

considered. The centersof the hip, knee, andankle remain within thisplane through theflexion-extension arc.The patellar groove(anterior-posterior axisof the femur) is co-planar with this plane sothat the patella is drawnsmoothly through. thegroove as a rope ispulled smoothly through

a well-aligned pulley.The epicondylar axis isperpendicular to theanterior-posterior plane,and the tibia swingsthrough this axis, stayingin the anterior-posteriorplane throughout theflexion-extension arc.

In the normal knee the epicondylar axis of the femur remains perpendicu-

lar to the anterior-posterior plane of the lower extremity throughout the

flexion-extension arc. This places the tibia nearly perpen-dicular to theground, and also places the hip in its most favorable position for function.

The joint surfaces between the femur and tibia are sloped downward to-

ward the medial side on all weightbearing surfaces, which places them slightly

in varus to the functional plane in all positions of flexion.

The long axis of the femur serves as the anatomical reference for align-

ment of the distal femoral cuts perpendicular to the mechanical axis and

anterior-posterior plane. Cutting the distal femoral surfaces at a 5 valgus

angle to the long axis of the femur places the joint surface perpendicular to

the anterior-posterior plane in the extended position. Likewise, cutting the

upper tibial surface perpendicular to the long axis of the tibia also places

the tibial joint surface perpendicular to the anterior-posterior plane in ex-

tension.

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Introduction

The anterior-posterior axis serves as the anatomic landmark for femoral

resection in flexion. The anterior-posterior axis can be constructed by

marking the lateral edge of the posterior cruciate ligament and the

deepest part of the patellar groove. A line drawn between these two

points lies in the anterior-posterior plane and passes through the center

of the femoral head and down the long axis of the tibia.

Fig.3. In the extendedposition the joint surface

slopes mediallyapproximately 3.-Tibial resection isperpendicular to the longaxis of the tibia andmechanical axis of thelower extremity. The re-section surface is 3 valgusto the articular surface.-Femoral resection isperpendicular to themechanical axis, and 5valgus to the long axis of

the femur. The resectionsurface is approximately3" varus to the articularsurface.-These 3" "errors" inthe femoral and tibialsurface resectionscompensate for oneanother, and result insurface resections thatare parallel to oneanother andperpendicular to the me-

chanical axis of thelower extremity.

Fig.4. With the kneeflexed 90, the jointsurface resections areparallel to the epi-condylar axis andperpendicular to theanterior-posterior axis ofthe femur. The femoralneck is antevertedapproximately 15 to theepi-condy-lar axis. Whenthe knee is in functionalposition in flexion(walking up stairs orstanding from a seatedposition), the positionsof the femoral neck andepi-condylar axis remainunchanged, and in thenormal knee the tibia isvertical.

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The lateral gastrocnemius tendon and capsule of the posterolateral

corner, lateral collateral ligament, and popliteus tendon complex attach

near the lateral femoral epicondyle and are stabilizers of the lateral side

throughout the flexion arc. The lateral posterior capsule and iliotibial

band attach far away from the epicondylar axis and are effective lateralstabilizers only in the extended position.

Fig.5. With the kneeflexed and viewed fromanteriorly, the deep and

superficial medialcollateral ligament fibersstabilize the medial side.The lateral collateralligament and popliteustendon stabilize thelateral side, and theposterior cruciateligament is a secondaryvarus and valgusstabilizing structure. Thepes- anserinus andiliotibial band are

parallel to the joint anddo not afford medial orlateral stability in theflexed position.

Fig.6. Lateral view ofthe knee showing themajor lateral staticstabilizing structureswith the knee extended.The lateralgastrocnemius tendon(and posterolateralcorner capsule), lateralcollateral ligament,lateral posterior capsule,popliteus tendon, andiliotibial band all cross

the joint perpendicular(or nearly so) to itssurface, and are capableof stabilizing the knee inthe extended position.

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Introduction

Fig.7. Lateral view ofthe knee showing themajor lateral staticstabilizing structureswith the knee flexed90. The lateralgastrocnemius tendon,posterolateral cornercapsule, lateral collateralligament, and poplkeustendon are the onlyeffective lateral

stabilizing structureswith the knee flexed tothis position. Theiliotibial band is parallelto the joint surface, andthe lateral posterior cap-sule is slack.

On the medial side, the medial collateral ligament (anterior and

posterior portions) is attached to the epicondyle, and is effective

throughout the flexion arc. The epicondylar attachment is broad enough

that there is a difference in function of the anterior and posterior

portions of this ligament in flexion and extension. The medial posteriorcapsule attaches far from the epicondylar axis, and is tight only in

extension. The posterior cruciate ligament is attached slightly distal and

posterior to the epicondylar axis, so it slackens in full extension and

tightens in flexion.

Fig. 8. On the medial view,

the medial collateral ligament

(deep and superficial) is the

primary medial stabilizer that

is tight in extension. The

anterior fibers are slackened

in full extension and the

posterior fibers (postero-

medial oblique ligament) are

differentially tightened in ex-

tension because of their po-

sition in the medial femoral

condyle. The lateral posterior-

capsule also is tight. Active

medial stability is added by

the medial hamstrings through

the pes anserinus and

semimembranosus.

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Fig.9. Viewed from themedial side with the kneeflexed. the medialstabilizing structures arethe deep and superficialmedial collateral liga-ment. The anterior fibersof the medial collateralligament are taut and theposterior fibers arerelatively lax because oftheir attach-ment more

posteriorly on the femur.The posterior capsule isslack and is not effectivein flexion. The semi-mem-branosus and pesanserina are parallel withthe joint and areincapable of supplyingactive stability in flexion.

Knowing this information, the surgeon can, after positioning the implants

properly with the axes of the knee, assess knee stability in flexion and

extension and release the structures that are tight. The surgeon also can

adjust the tightness of intact ligaments by changing the position and sizeof the femoral component, altering the slope of the tibial surfaces, and

adjusting the thickness of the tibial polyethylene spacers. Anterior-

posterior stability can be altered by changing me configuration of the

polyethylene component.

Fig.10. Ligaments thatattach to the femur near theepicon-dyles guide the tibiathrough its arc of flexionand maintain stabilitythroughout the full rangeof motion. Because theligaments attach across afinite surface of thecondyles, the anterior andposterior portions behavedifferently in flexion andextension. As illustrated inthis drawing, the anteriorportion of the medialcollateral ligament tightensin flexion, and theposterior portion tightensin extension.

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Introduction

The arthritic process often affects the articular surfaces and ligaments to

cause deformity, and this places the tibia outside the functional plane. To

achieve optimal function of the knee in flexion and extension, the joint

surfaces must be returned to their proper positions and the liga-ments ad-justed to their proper tensions through-out the functional arc of the knee.

A number of factors in the arthritic process affect the functions of liga-

ments. Osteophytes deform them, causing them to be excessively tight, or

restrict sliding, causing flexion contracture and restriction of flexion. As

the joint surfaces collapse, their attachment points come closer together

and the ligaments shorten irreversibly. When the joint surfaces separate on

the convex side of a deformity, the ligaments usually are elongated perma-

nently. All these abnormalities can be addressed by thorough debridement

of the joint, choice of size and position of the implants, and release of con-

tracted ligaments.

Fig. 11. Osteophytes are animportant factor in ligamentbalancing. They constrainthe deep and superficial me-dial collateral ligament andthe medial posterior capsule.

Fig. 12. Osteophytes sur-round the posterior cruciateligament and interfere withflexion and extension, andalso invade the popliteus re-cess, restricting flexibility onthe lateral side of the knee.

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Fig.13.14. When all medialand lateral stabilizers thatare attached to theepicondyles are deformed(either stretched orcontracted) the deformity

is effective throughout theflexion-extension arc. Inthese illustrations thelateral collateral ligamentand pop-liteus tendon arecontracted, causing theknee to be tight laterallyboth in flexion andextension. The anterior andposterior portions of themedial collateral ligamentare stretched so the knee isloose medially in flexion

and extension.

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Introduction

Fig.15,16. Release of thelateral collateral ligamentand popliteus tendon hassimilar effect in flexionand extension. Likewise,addition of thickness tothe tibia restores medialstability similarly inflexion and extension.

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When ligaments are released to correct deformity, other ligaments,

which are not so severely contracted, are brought into play to stabilize

the knee. The posterior cruciate ligament and posterior capsule are the

most important secondary static stabilizing structures in varus and valgusknees.

When ligaments must be released to correct deformity, as in this

varus knee, the secondary stabilizing structures are called into action.

Fig.17. Release of theanterior and posteriorportions of the medialcollateral ligamentleaves the knee

dependent on the medialposterior capsule formedial stability in exten-sion.

Fig.18. In flexion, themedial posterior capsuleis lax, so the knee isespecially dependent onthe posterior cruciateligament for media]

stability in flexion afterrelease of the medialcollateral ligament.

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Introduction

Contracture or elongation of these secondary stabilizing structures may

affect ligament balance as well, and sometimes these structures must be

adjusted. Because the posterior cruciate ligament is a medial structure,

it often is contracted in the varus knee and stretched in the valgus knee.

Fig.19. The posteriorcruciate ligament is amedial structure, andoften is contracted in thevarus knee along with themedial collateral liga-

ment. Thus it often mustbe released in the varusknee.

Fig.20. The medialposition of the posteriorcruciate ligament makesit vulnerable to stretchingin the valgus knee. Thus it

often must be substitutedfor in the valgus knee.

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In the knee that is free of deformity in which there is no ligament

contracture or stretching of ligaments, resection of the thickness of the

implant from all surfaces and replacement of this thickness of bone with

the implant results in restoration of ligament balance through the full

flexion arc. This statement is intuitively obvious and also has been

demonstrated to be true by experiment (see suggested readings list).When no deformity exists, the articular surfaces them-selves can be used

as landmarks for resection and restoration of joint surface position.

However, when deformity does exist, anatomical landmarks and axes of

reference that are not distorted by the arthritic process must be used to

resect the bone surfaces in correct alignment in flexion and extension.

Fig.21. As the tibialarticular surface slides on

the curved surface of thefemur, the ligaments thatattach to the epicondylesmaintain normal tensionthrough the flexion arcdue to the shape of thefemoral condyles andtibial surface. Resectionof the thickness of theimplattts from the distaland posterior surfaces ofthe femur and from theupper surface of the tibia

prepares the knee forreplacement so that theligaments will functioncorrectly through the fullarc of flexion.

Fig.22. Replacement ofthese resected surfaceswith the total kneereplacement componentsleaves the ligamentsperforming normally

through the full flexionarc.

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Introduction

Fig.23. In most cases theintact (convex) side of theknee should serve as thelandmark for resectionboth distally andposteriorly. Even whenthe collateral ligamentsare stretched, the distaland posterior surfaceswill be positionedcorrectly to accept athicker tibial componentto achieve stability inflexion and extension,and the ligaments on thecontracted (concave)side can be released toachieve correct balanceto accommodate thisposition.

Restoration of the joint surfaces to their proper alignment with the me-

chanical axes of the extremity is the cornerstone of successful ligamentbalance, stability, and kinematics of the knee in total knee arthroplasty.

This is accomplished by aligning the joint surfaces perpendicular to the

anterior-posterior plane, and the simplest means of establishing the

position of the anterior-posterior plane is to establish the mechanical

axis of the lower extremity in flexion and extension. The mechanical

axis of the femur in extension is estimated easily by placing a rod down

the femoral shaft. Then the bone is resected at a 5 valgus angle to this

rod. The mechanical axis of the femur in flexion is estimated easily by a

line drawn in the anterior-posterior axis of the femur, and the bone is

resected perpendicular to this line. The tibial shaft lies in the anterior-

posterior plane in flexion and extension, so the tibial joint surface is

resected perpendicular to the long axis of the tibia. This can beestablished with either an intramedullary rod or an extramedullary

guide. By using the three accessible anatomic axes, the femoral and

tibial components can be positioned so that the knee is in correct varus-

valgus alignment throughout the flexion arc. The ligaments then can be

balanced around the joint by determining which ligaments are

contracted based on their function in flexion and extension. Simply

stated, ligaments that attach to the femur on or near the epicondyles are

effective both in flexion and extension, and those that attach distant

from the epicondylar axis are effective either in flexion or extension, but

not in both positions. To extend this concept further, it can be stated that

the portions of the ligament complexes that attach anteriorly in the epi-condylar areas stabilize primarily in flexion, and those that attach

posteriorly in the epicondylar areas stabilize primarily in extension.

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Suggested Readings

1. nouchi YS, Whiteside LA, Kaiser AD, Milliano MT: The effectof axial rotational alignment of the femoral component on knee

stability and patellar tracking in total knee arthroplasty. Clin Orthop287:170-177, 1991.

2. Arima J, Whiteside LA: Femoral rotational alignment, based onthe anterior-posterior axis, in total knee arthroplasty in a valgus knee.J Bone Joint Surg 77A:1331-1334, 1995.3. Berger RA, Rubash HE, Seel MJ, Thompson WH, Crossett LS:Determining the rotational alignment of the femoral component intotal knee arthroplasty using the epicondylar axis. Clin Orthop286:40-49, 1993.4. Brantigan , Voshell AF: The mechanics of the ligaments andmenisci of the knee joint surfaces. Bone Joint Surg 23:44-66, 1941.5. Cooke TD, Pichora D, Siu D, Scudamore RA, Bryant JT: Surgicalimplications of varus deformity of the knee with obliquity of joint

surfaces. J Bone Joint Surg Br 71:560565, 1989.6. Hungerford DS, Krackow KA, Kenna RV: Alignment in totalknee arthroplasty. In Dorr LD (ed), The Knee- Papers of the FirstScientific Meeting of the Knee Society. Baltimore, University ParkPress 9-21, 1985.7. Markolf KL, Mensch JS, Amstutz HC: Stiffness and laxity of theknee - the contributions of the supporting structures. J Bone JointSurg Am 58:583-594, 1976.8. Trent PS, Walker PS, Wolf B: Ligament length patterns, strengthand rotational axes of the knee joint. Clin Orthop 117:263-270, 1976.9. Wang CJ, Walker PS: Rotatory laxity of the human knee joint, JBone Joint Surg Am: 56:161-170, 1974.10. Whiteside LA, Summers RG: Anatomical landmarks for anintramedullary alignment system for total knee replacement. Orthop

Trans 7:546-547, 1983.11. Whiteside LA, Summers RG: The effect of the level of distalfemoral resection on ligament balance in total knee replacement. InDorr LD (ed). The Knee: Papers of the First Scientific Meeting of theKnee Society. Baltimore, University Park Press 59-73, 1984.12. Whiteside LA, Kasselt MR, Haynes DW: Varus-valgus androtational stability in rotationally unconstrained total kneearthroplasty. Clin Orthop 219:147-157, 1987.13. Whiteside LA, McCarthy DS: Laboratory evaluation ofalignment and kinematics in a unicompartmental knee arthroplastyinserted with intramedullary instrumentation. Clin Orthop 274:238-247, 1992.14. Whiteside LA, Arima J: The anterior-posterior axis for femoralrotational alignment in valgus total knee arthroplasty. Clin Orthop

321:168-172, 1995.15. Yoshii I, Whiteside LA, White 5E, Milliano MT: Influence ofprosthetic joint line position on knee kinematics and patellarposition. J Arthroplasty 6:169-177, 1991.16. Yoshioka Y, Siu D, Cooke TDV: The anatomy and functionalaxes of the femur. J Bone Joint Surg Am 69:873-880, 1987.17. Yoshioka Y, Cooke TDV: Femoral anteversion: Assessmentbased on function axes. J Orthop Res 5:86-91, 1987.

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Patella

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2. Patella

Basic Principles

The patella maintains a delicate balance in total knee arthroplasty, and is

dependent on position and configuration of the patellar and femoral ar-

ticular surfaces, angle of the quadriceps and patellar tendons, and tension

of the medial and lateral retinacula. As the knee flexes, the patella engages

the patellar groove and then follows this groove through the flexion arc.

The apex of the patella stays within the median anterior-posterior plane in

the normal knee, and the patellar groove also must lie in this plane to ac-

commodate this patellar position.

Fig.24. In the normalknee the patellar crestlies about equidistantfrom the medial andlateral epicondyles. Thelateral facet is widerthan the medial facet, sothe patella and patellartendon lie slightly lateralto the midline. Themedial and lateralretinacular structures aresomewhat loose inextension.

Fig.25. As the kneeflexes the patella stays inthe patellar groove andthus follows the antedor-posterior plane of thefemur. The medial andlateral retinacula beginto tighten as the kneeflexes.

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Fig.26. As the kneecontinues to flex thepatella is drawn along inthe patellar groove as a

rope is drawn through apulley. The medial andlateral retinacula tighteneven more.

Fig.27. Correct resectionof the femoral surfacesis necessary to achievestable patellar functionthrough the entire arc offlexion. When thefemoral component isaligned correctly with

the anterior-posteriorplane, the joint surfacesare perpendicular to theanterior-posterior axis inflexion. The patella isheld in position by thecontour of the patellargroove, which also is co-planar with the anterior-posterior plane, and bythe tension in thequadriceps, patellartendon, and medial andlateral patellarretinacula.

Fig.28. In the extendedposition, the patellargroove is equidistantfrom the medial andlateral epicondyles andlies in the mediananterior-posterior plane.The joint surfaces are

perpendicular to themedian anterior-poste-rior plane. The tibialtubercle is lateral to themidline anterior-posterior plane in alldegrees of flexion, so thepressure is alwaysgreater on the lateralside of the patella, andthere is a tendency forthe patella to subluxlaterally. Thus it isnecessary to have a deeppatellar groove and anelevated lateral flangesurface.

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Patella

Displacement of the patellar groove from its normal position and align-

ment in the midline anterior-posterior plane causes abnormalities in all

the mechanisms that stabilize patellar tracking. Placing the femoral

component in internal rotation relative to the median anterior-posteriorplane malaligns the patellar groove with the line of pull of the

quadriceps mechanism, and has the same effect as malaligning a pulley

with the rope that is pulled through it. Therefore, when the femoral

component is internally rotated, the quadriceps mechanism becomes

unstable in the groove.

Fig.29. Internal rotational

malposition of the femoral

component medializes the

patellar groove and presents

the patella with a slanted

track in which to run. It also

aligns the knee in valgus in

flexed positions. As depicted

here, the knee is not bearingload, so the lateral joint gapes

open, and the tibia remains

aligned with the anterior-posterior plane of the lower

extremity.

Fig.30. When, on weightbearing, the tibia collapses

into the valgus position

dictated by the position of

the femoral component, thetibial tubercle shifts laterally,increasing the Q-angle, thus

increasing the lateralizing

force on the patella, and

worsening the tendency for

the patella to sublux laterally.

Now the tibia is aligned withthe patellar groove, but nei-

ther the tibia nor the patel-

lar groove is aligned with the

anterior-posterior plane of

the lower extremity.

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Fig.31. With the knee inthe extended position,the knee joint is incorrect varus-valgusalignment, but thefemoral component isinternally rotated. This

malposition of thefemoral componentmedializes the patellargroove while leaving theepicondyles, patellarretinae u la, and patellain their normalpositions. Therefore thepatella is subluxed later-ally in extension.

Suggested Readings

1. Anouchi YS, Whiteside LA, Kaiser AD, Milliano MT; The effectof axial rotational alignment of the femoral component on kneestability and patellar tracking in total knee arthroplasty. Clin Orthop287:170-177, 1991.2. Arima J, Whiteside LA: Femoral rotational alignment, based onthe anterior-posterior axis, in total knee arthroplasty in a valgusknee. I Bone Joint Surg 77A:1331-1334, 1995.7.3. Grace JN. Rand J.A. Patellar instability after total kneearthroplasty. Clin Orthop 237:184-189, 1988.4. Martin JW, Whiteside LA: The influence of joint line position onknee stability after condylar knee arthroplasty. Clin Orthop 259:146-156, 1990.5. Whiteside LA, Summers RG: Anatomical landmarks for an

intramedullary alignment system for total knee replacement. OrthopTrans 7:546-547, 1983.6. Whiteside LA, Summers RG: The effect of the level of distalfemoral resection on ligament balance in total knee replacement. InDorr LD (ed.) The Knee: Papers of the First Scientific Meeting ofthe Knee Society. Baltimore, University Park Press 59-73, 1984.7. Whiteside LA, Kasselt MR, Haynes DW: Varus-valgus androtational stability in rotationally unconstrained total kneearthroplasty. Clin Orthop 219:147-157, 1987.8. Whiteside LA, McCarthy PS: Laboratory evaluation of alignmentand kinematics in a unicompartmental knee arthroplasty insertedwith intramedullary instrumentation. Clin Orthop 274:238-247,1992.9. Whiteside LA, Arima J: The anterior-posterior axis for femoral

rotational alignment in valgus total knee arthroplasty. Clin Orthop321:168-172, 1995.10. Whiteside L.A. Distal realignment of the patellar tendon tocorrect patellar tracking abnormalities in total knee arthroplasty. ClinOrthop 344:284289, 1997.

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Posterior

Cruciate

Ligament

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3. Posterior Cruciate Ligament

Basic Principles

The posterior cruciate ligament serves a complex purposethroughout the entire flexion arc, acting primarily to prevent

posterior travel of the tibia, but also performing secondary varus,

valgus and rotational stabilizing roles when the collateral ligaments

are deficient. It also provides resistance to hyperextension when

the posterior capsule is deficient. Because the posterior cruciate

ligament is a medial structure attached to the medial femoral

condyle, it often contracts in the varus knee and stretches in the

valgus knee. When it is contracted it often can be released

partially, and much of its function can be preserved. Even when it

is insufficient to provide adequateposterior stability, it can provide

rotational and varus-valgus stabilization.

Fig.32. The posterior cruciate ligament,like the medial collateral ligament, isattached over a broad band, so its anteriorand posterior portions behave differentlyin flexion and extension. The anteriorportion of the posterior cruciate ligamentis attached to the femur distal to the

epicondylar axis so it tends to loosen infull extension. The posterior portion,being behind the center of rotation, tendsto tighten in hyper-extension. Both bandsare relatively loose at 0 knee flexion.

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Fig.33. In the flexedposition, the anterolateralfibers are brought totension and theposteromedial fibersloosen.

Fig.34. Because theposterior cruciate ligamentis attached to the medialfemoral condyle, it tendsto shorten in the varusknee and loosen in thevalgus knee. The poste-rior cruciate ligamenthas auxiliary attachmentsto the posterior portionsof the menisci and jointcapsule.

3.1. Tight Posterior Cruciate Ligament

Because the posterior cruciate ligament is a medial structure, it often is

contracted in the varus knee and stretched in the valgus knee. The tight

posterior cruciate ligament causes excessive rollback of the femur.When palpated with the knee in flexion, it feels extremely tight when it

is abnormally tight.

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Fig.35. The knee has

normal stability inextension.

Fig.36. But in flexionthe femur rollsexcessively posteriorly,and the posteriorcruciate ligament ispalpably tight. Neithercollateral ligament istight.

Fig.37. On the side view,the femoral componentis rolled excessivelyposteriorly, and isperched on the posterioredge of the tibial compo-nent. The anterior bandof the medial collateralligament also maybeaffected by this posteriorposition, and may seemto be excessively tight.The anterolateral portion

of the posterior cruciateligament is primarily re-sponsible for theexcessive posteriorrollback.

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3.2. Release of the Posterior Cruciate Ligament

A simple and effective means of releasing the posterior cruciate ligament is

to remove the polyethylene trial component, and elevate the bone attach-

ment of the posterior cruciate ligament directly from the tibia.

Fig.38. The posteriorcruciate ligament isreleased with a smallsegment of bone from itsposterior tibial attach-ment. A quarter-inchosteotome is used tomake several small cutsaround the posteriorcortical margin, and

then, the bone piece islevered loose.

Fig.39. The bone pieceslides proximally 0.5cm-lcm, slackening theposterior cruciateligament. The synovialmembrane remains in-tact, and the ligament re-

mains unfrayed by therelease.

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Fig.40. After posterior cruciateligament release the tibiaslides posteriorly, and thefemoral surfaces seat in thenormal position on the tibial

surfaces.

Fig41. The attachment of theposterior cruciate ligamenthas slid proximally, slacken-

ing the posterior cruciateligament, but tightening thesurrounding attachments ofthe posterior cruciate liga-ment so that they prevent ex-cessive laxity.

Fig.42. The posterior cruciateligament, in its new position,allows the tibia to slideposteriorly so that the femo-ral surfaces sit farther forward on the tibia.

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Fig.43. After recessionthe posterior cruciateligament, occasionally iselongated too much andthe secondary posteriorstabilizing structures areinsufficient to preventposterior sag. Thefemoral condyles seatfar forward on the tibialsurfaces and the tibiasags posteriorly. The

quadriceps complex isplaced at a disad-van-tage by this tibialposition.

Fig.44. When theconforming plus

polyethylene insert isapplied, posterior sag iscontrolled, and the tibiais held forward,improving the me-chanical advantages ofthe quadriceps. Thebarrier to anteriordislocation of the femuris large both verticallyand horizontally.

Fig.45. In full extension thevertical and horizontal dis-tance of travel required forsubluxation also is large,

and the tibia is heldanteriorly by the anteriorwall of the conforming plusprosthesis.

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Fig.46. When the patellais low, impingement

against the anterior lipof the constrainedpolyethylene componentis likely. In most casesthese on forming-pluscomponents are madewith a recessed area forthe patella.

Suggested Readings

1.Arima J, Whiteside LA, Martin JW, Miura H, White SE, McCarthy DS:

Effect of partial release of the posterior cruciate ligament in total kneearthroplasty. Clin Orthop 353:194-202, 1998.2.Hagena FW, Hofmaim GO, Mittelmeier T, Wasmer G, Bergmann M:

The cruciate ligament in knee replacement. Int Orthop 13:13-16,1989.

3.Hughston J: The posterior cruciate ligament in knee-joint stability. In:Proceedings of The American Academy of Orthopaedic Surgeons. JBone Joint Surg Am 51:1045, 1969.

4.Lew WD, Lewis JL: The effect of knee-prosthesis geometry on cruciateligament mechanics during flexion. J Bone Joint Surg Am 64:734-739, 1982.

5.Shoemaker SC, Daniel DM: The limits of knee motion. In Daniel DM,Akeson WH, O'Connor JJ (eds). Knee Ligaments. Structures, Function,Injury, and Repair. New York, Raven Press 153-161, 1990.

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Varus Knee

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4. Varus Knee

Basic Principles

Medial stability of the knee is a complex issue, and involves ligaments

that behave differently in flexion and extension. The contracture and

stretching that occur due to deformity and osteophytes affect these

ligament structures unequally, and often cause different degrees of

tightness or laxity in flexion and extension after the bone surfaces are

resected correctly for varus-valgus alignment The distortion of the joint

surface also can cause varus-valgus alignment to differ in the flexed

and extended positions, and the knee thus may require adjustment of

portions of the medial stabilizing complex that affect stability either in

flexion or extension.

The cornerstone of correct ligament balancing is correct varus-

valgus alignment in flexion and extension. For alignment in the

extended position, fixed anatomic landmarks such as the intramedullary

canal of the femur and long axis of the tibia are accepted. When thejoint surface is resected at an angle of 5 to 7valgus to the medullary

canal of the femur and perpendicular to the long axis of the tibia, the

joint surfaces are perpendicular to the mechanical axis of the lower

extremity, and roughly parallel to the epicondylar axis in the extended

position. In the flexed position, anatomic landmarks are equally

important for varus-valgus alignment. Incorrect varus-valgus alignment

in flexion not only malaligns the long axes of the femur and tibia, but

also incorrectly positions the patellar groove both in flexion and

extension. Finding suitable landmarks for varus-valgus alignment has

led to efforts to use the posterior femoral condyles, epicondylar axis,

and anterior-posterior axis of the femur. The posterior femoral condylesprovide excellent rotational alignment landmarks if the femoral joint

surface has not been worn or otherwise distorted by developmental

abnormalities or the arthritic process. However, as with the distal

surfaces, the posterior femoral condylar surfaces sometimes are

damaged or hypoplastic (more commonly in the valgus than in the varus

knee) and cannot serve as reliable anatomic guides for alignment. The

epicondylar axis is anatomically inconsistent and in all cases other than

revision total knee arthroplasty with severe bone loss, is unreliable for

varus-valgus alignment in flexion just as it is in extension. The anterior-

posterior axis, defined by the center of the intercondylar notch

posteriorly and the deepest part of the patellar groove anteriorly, is

highly consistent, and always lies within the median sagittal plane thatbisects the lower extremity, passing through the hip, knee, and ankle.

When the articular surfaces are resected perpendicular to the anterior-

posterior axis, they are perpendicular to the anterior-posterior plane, and

the extremity can function normally in this plane throughout the arc of

flexion.

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In the presence of articular surface deformity the anatomic references are

especially important for correct varus-valgus alignment. The usual

reliable landmarks for varus-valgus alignment of the femoral component

in flexion include the posterior femoral condyles, the long axis of the

tibia, and the tensed supporting ligaments. If the posterior femoral

condyle wears and the tibial plateau collapses on the medial side of theknee, these normally reliable landmarks cannot be used. Instead, the

anterior-posterior axis of the femur is used as a reference line for the

femoral cuts and the long axis of the tibia is used for a reference line for

the tibial cut so that the joint surfaces are cut perpendicular to these two

reference lines. Once the joint surfaces have been resected correctly to

establish normal varus-valgus alignment in flexion and extension, the

trial components are inserted and ligament function is assessed in flexion

and extension. The "liga-ments are released according to their function at

each position, The medial collateral ligament (deep and superficial

layers} attaches to the medial epicondylar area through a broad band. The

posterior oblique portion, which spreads posteriorly over the medial tibialflare and incorporates the sheath of the semimembranosus tendon,

tightens in extension. The anterior portion of the ligament complex,

which extends anteriorly along the medial tibial flare, tightens in flexion

and loosens in extension. The posterior capsule is loose in flexion, and

tightens only in full extension. With this information the medial ligament

structures of the knee can be released individually according to the

position in which excessive tightness is found.

Fig.47. In the varus kneethe femoral condyles areconfigured normally,and a line through thelong axis of the femoraldiaphysis crosses thejoint line in the center ofthe patellar groove. Thevarus malalignment ofthe extremity is causedby a defect in the medialtibial plateau. A linethrough the center of thetibial diaphysis crossesthe joint in the center ofthe notch between thetibial spines. Entrypoints into the joint forintramedullaryalignment rods are madein the center of thepatellar groove anddirectly between thetibial spines.

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Fig.48. The varus knee has agroup of bone and ligamentabnormalities that must beaddressed to correct the de-formity. The mechanical axisof the femur is tilted mediallyrelative to the long axis of thetibia. The distal femoralsurface usually remains invalgus alignment to the long

axis of the femur. Most of thevarus deformity is caused bydeficiency in the medial tibialplateau. The deep andsuperficial medial collateralligaments are contracted anddeformed by osteophytes.

Fig.49. In the flexed positionthe mechanical abnormalitiesare similar. The deficiency inthe medial tibial plateau causesthe tibia to tilt toward varus,and the anterior-posterior axisof the femur tilts mediallyrelative to the long axis of thetibia. Here the hip is in neutralposition with the anterior-posterior axis passing through

the center of the femoral head,and the femoral neckanteverted 15" to theepicondylar axis. The deep andsuperficial medial collat-eralligamenrs are contracted,and the posterior cruciateligament, being a medialstructure, often is contracted aswell.

Finding the anterior-posterior axis can be difficult if the intercondylar

notch is distorted by osteophytes. However, the lateral edge of the

posterior cruciate ligament is consistently in the center of the

intercondylar notch, and can usually be identified easily without

remaining the osteophytes.

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Fig.50. The osteophytesmay deform the medialcollateral ligament andposterior capsule

enough to cause flexioncontracture.

Fig.51. The tibia often issubluxed laterally in thevarus knee, shifting theorigin of the popliteusmuscle proximally andlaterally, and shorteningthe popliteus complex.

Fig.52. The distalsurfaces of the femur areresected perpendicular tothe mechanical axis,which is approximatelyparallel to the epi-condylar axis. This is

facilitated by aligningthe resection guide at 5"valgus to the long axis ofthe femur. Becausedeformity of the distalfemoral joint surface israre in the varus knee,approximately equalthickness of bone usuallyis resected from themedial and lateral sides.The upper surface of thetibia is resected

perpendicular to the longaxis of the tibia,resecting the thickness ofthe tibial component (10-12 mm) from the intactlateral side, and muchless from the deficientmedial tibial plateau. Inmany cases a defect isleft in the medial tibialplateau.

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The sequence in which the procedures are performed is important in

total knee replacement. Resection of the femoral surfaces makes the

tibial surfaces accessible. Resection of the tibial surface clears the wayto remove the osteophytes. Removal of the osteophytes frees the

ligaments so they may be assessed and released as needed. No ligament

should be released until all the osteophytes are removed otherwise

excessive laxity may occur. Extra bone should not be removed to

correct a flexion contracture until all ligament balancing has been

finished, otherwise inappropriate laxity in extension may occur once

ligament release has been done.

Fig.51. The anterior andposterior surfaces of thefemur are resectedperpendicular to the

anterior-posterior axisand parallel to theepicondylar axis. Similarto the long axis of thefemur, the anterior-posterior axis is used asa reliable reference axisto align these cuts. Thisaxis is identified bymarking the lateral edgeof the posterior cruciateligament and the deepestpart of the patellar

groove. The articularsurfaces are resectedperpendicular to theanterior-posterior axisand parallel to theepicondylar axis. In mostcases of varus knee theposterior femoralcondyles maintain theirnormal 3 medial down-slope, and can be usedfor alignment of thefemoral component in

flexion. In this case, a 3external rotational guidewould be used to engagethe posterior femoralcondyles in order toplace the anterior andposterior femoral sur-faces in neutralalignment. The long axisof the tibia is used as areference for the uppertibial resection. Thissurface is resected

perpendicular to thetibial long axis whenviewed from the front,and with a 4 to 7posterior slope whenviewed from the side.

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Fig.54. The femur is sizedfrom the anterior cortex

(just proximal to the jointsurface) to the posteriorfemoral joint surface.Resection guides are usedto measure and remove thethickness of the implantfrom all intact surfaces ofthe femur. An anteriorstylus is used to position theresection guide so that theanterior surface cut alignsflush with the anteriorcortex of the femur.Posterior paddles are usedto engage the posteriorfemora] condyles. Theseposterior paddles are usedto confirm the anterior-posterior size of the femurand also to serve as a guidefor rotational alignment(varus-valgus alignment inflexion) of the femoralcomponent.

Fig.55. Varus-valgus align-ment of the femoral compo-nent in flexion (rotationalalignment) is determined bythe anterior-posterior axis.Here the cutting guide isaligned with the anterior-posterior axis of the femur.The anterior-posterior planeof the femur is defined bythe lateral edge of theposterior cruciate ligament

and the deepest point in thepatellar groove. This alsoaligns the femoral surfacecuts parallel to theepicondylar axis. Threedegrees of externalrotational alignment relativeto the posterior femoralcondylar surface would alsoachieve neutral varus-valgus alignment in thiscase since there is noposterior condylar surface

deformity.

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Fig.56. After removal ofall resected segmentsfrom the distal femoralsurfaces, the tibialalignment instrument isapplied and the upper

surface of the tibia isresected. In most casesthe tibial surface isresected perpendicular tothe long axis of the tibiain the coronal plane, butit is sloped 4 to 7"posteriorly in the sagittalplane to match thenormal slope of the tibia.

Fig.57. After the tibialsurface is removed, theosteophytes are firstremoved from the medialfemoral edge anteriorly,distally and thenposteriorly, carefullyteasing them from thedeep medial collateralligament.

Fig.58. Next theosteophytes are clearedfrom the intercondylarnotch while care is takento avoid damage to theposterior cruciateligament. The medialtibial osteophyte isremoved next, all theway around the posterioredge.

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Fig.59. After the medialtibial osteophyte has beenremoved, the knee will befreed enough to allow

easy access to theposterior femoral osteo-phytes. They are cut freewith a curved half-inchosteotome and the sameosteotome is used to freethe osteophyte in thepopulous recess laterally.

Fig.60. Finally, the osteo-phytes are teased loose fromthe posterior capsule and the

osteophyte that surrounds

the popliteus tendon is re-

moved from the popliteus

recess.

The trial components are inserted before any ligament releases are done,

and the knee is tested for stability in flexion and extension. With the

trials in place, the knee is evaluated in flexion and extension to assess

varus, valgus, rotational, anterior and posterior stability.

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Fig.61. The medialcollateral ligament attachesto the medial femoralcondyle over a fairly broadarea, and this affects thefunction of the ligament inflexion and extension. Withthe knee fully extended, the

posterior capsule and theposteromedial obliqueportion of the medialcollateral ligament are tight.The anterior portion of themedial collateral ligamentloosens in full extension,but being close to the centerof rotation, it acts as astabilizing structurethrough-out the flexion-extension arc.

Fig.62. When the knee flexesthe posterior capsule and thepostero-medial oblique portionof the medial collateralligament loosen. The anteriorportion of the medial collateral

ligament tightens.

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Fig.63. To test the knee inflexion, the ankle isgrasped with one handwhile the other handsteadies the knee. Theextremity then is rotatedinternally through the hipuntil the medial ligamentsare stressed, then rotatedexternally until the lateralligaments are stressed.

Fig.64. The tibia is rotatedto assess rotationalstability, then the tibia isgrasped just below thetibial tubercle and pushedposteriorly and pulledanteriorly to assess

anterior-posterior stability.

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4.1. Tight Medially in Flexion, Loose in Extension

In some cases the medial structures are not contracted uniformly, and the

knee may be tight medially only in flexion, but not in extension.

Fig.65. The anteriorportion of the medialcollateral ligament isexcessively tight in

flexion. The medialfemoral condyle sitsfurther posteriorly thandoes the lateral femoralcondyle and the tibialends to pivot around themedial collateralligament. Otherwise theknee is well aligned, andthe anterior-posterioraxis and long axis of thetibia align well with oneanother. The posterior

cruciate ligament is softto palpation, and is not adeforming structure.

Fig.66. The posteriorportion of the medialcollateral ligament isloose in flexion, anddoes not contribute tothe ligament imbalance.

The anterior portion istight and definitelycontributes to theligament imbalance.

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Fig.67. In extension theanterior portion of themedial collateral ligamentslackens normally, so

ligament balance is normalin extension.

Fig.68. The posteriorportion of the medialcollateral ligamentbecomes taught inextension, and the anteriorportion slackens so that theknee has normal ligamentbalance in extension.

Fig.69. This imbalance iscorrected by releasing theanterior portion of themedial collateral ligament.The knee is flexed to 90and a curved 1/2-inchosteotome is used toelevate the anterior portionof the deep and superficialmedial collateral ligamentsubperiosteally while

leaving the attachment ofthe pes anserinus intact.

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Fig.70. The taught anteriorfibers are released sub-

periosteally. These fibersattach fairly far distally (8-10cm), and the osteotome ispassed far enough to com-pletely release the anteriorfibers. The attachment of thepes anserinus and posterioroblique fibers of the medialcollateral ligament are leftintact.

Fig.71. The anterior fibers ofthe medial collateral ligamenthave been released. Medialstability in extension is nearnormal because the posteriorportion of the medialcollateral ligament and theposterior medial capsulefunction normally.

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Fig.72. In flexion theanterior medial collateralligament is no longertight. The posteromedialoblique portion of themedial collateral ligamentnow acts as a secondarymedial stabilizer inflexion.

Fig.73. On the anteriorview, the medial femoral

condyle sits in the centerof the tibial surface, andthe tibia pivots normallyaround the posteriorcruciate ligament. Theposterior cruciateligament acts as asecondary varus-valgusstabilizer in flexion.

4.2. Tight Medially in Extension, Balanced in Flexion

In some cases the posterior medial structures are tight and the anteriormedial collateral ligament is normal after insertion of the trial components.

These knees are tight in extension, but balanced normally in flexion.

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Fig.74. In this case theknee does not extendquite fully. The posteriorportion of the medialcollateral ligament istight and the posteriorcapsule also may becontracted. The anterior

portion of the medialcollateral ligament isloose in extension.

Fig.73. In flexion theanterior medial collateralligament fibers are broughtto normal tension, and theposterior portion of themedial collateral ligamentis slackened along with themedial posterior capsule.The knee has normalstability in flexion.

Fig.76. in this case, only theposterior portion of the me-dial collateral ligamentshould be released first. Acurved 1/2-inch osteotomeis used to elevate all but theanterior portion of the me-dial collateral ligament. Theosteotome is directed ap-proximately 45" downwardand tapped gently to releasethe postero-medial obliquefibers from the tibia and

from the tendon of thesemimembranosus.

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Fig.77. If the knee still istoo tight medially inextension but is wellbalanced in flexion, then

the medial posteriorcapsule may be released.The curved t/2-inchosteotome is used to gentlyelevate the capsule fromthe femur. Furtherposterior capsular releasecan be achieved byreleasing the posteriorcapsule from the tibia aswell (see flexion con-tracture section).

Fig.78. The knee has hadrelease of the medialposterior capsule and theposteromedial obliquefibers of the deep andsuperficial medialcollateral ligament. Theanterior fibers of the deepand superficial medialcollateral ligament are stillintact and afford medialstability in flexion andextension. The anterioredge of the medialcollateral ligament, whichnormally is loose in exten-sion, now has beenbrought into play, and actsas a secondary medialstabilizing structure.

Fig.79. With the kneeflexed, the anterior portionof the medial collateralligament tightens

normally, providingnormal medial stability tothe knee.

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4.3. Tight Medially in Flexion and Extension

In many cases with a long-standing varus deformity and medial

ligament contracture, the knee is tight medially both in flexion andextension. This indicates that the entire medial collateral ligament is

contracted. The posterior capsule and posterior cruciate ligament also

may be contracted, but the primary contracture is the medial collateral

ligament in these cases. The posterior cruciate ligament and posterior

capsule cannot be evaluated until the medial collateral ligament

contracture has been corrected.

Fig.8O. In this illustrationthe knee is tight mediallyand gapes spontaneouslylaterally. It also has a 10flexion contracture. Theknee is still in varusmalalignment due toligament contracture despitecorrect alignment of thebone surface resection.

Fig.81. The knee is tightmedially in flexion as well.The knee is still in varus inflexion because of ligamentimbalance despite correctalignment of the bonesurface cuts. The lateral sidegapes spontaneously, andthe medial femoral condylerolls to the posterior edge of

the tibial spacer. The entiresuperficial medial collateralligament, when palpated,feels tight in the flexed andextended positions. At thisstage it is impossible toknow if all mediaJstructures including theposterior cruciate ligamentand medial posteriorcapsule are tight, but it isclear that at least the ante-rior and posterior portions

of the medial collateral liga-ment are tight.

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Fig.82. Because the knee istight medially both inflexion and extension, theentire medial collateralligament is likely to betight, but the posteriorcapsule and posteriorcruciate ligament cannot

yet be assessed. Becausethe anterior portion of themedial collateral ligamentis more nearly isometricthan the posterior, it isreleased first in hopes thatit will be the only releasenecessary. The curvedhalf-inch osteotome first isinserted at the upper,anterior edge of the medialcollateral ligament.

Fig.83. The curved oste-otome is placed beneaththe superficial medial

collateral ligament justbehind the insertion of thepes anserinus, and theanterior portion of thedeep and superficial me-dial collateral ligament isstripped subperiosteallyfrom the tibia first.Because the anterior fibershave some effect both inflexion and extension, thisoften is sufficient.However, in most cases it

is necessary to strip theposterior portion from itsattachments as well.

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Fig.84. If the knee remainstight medially in extensionafter release of the anteriormedial collateral ligament

fibers, then the posteriorfibers are released. Here thecurved half-inch osteotome ispassed under the releasedanterior fibers and angleddownward 45" to release theposterior oblique fibers of themedial collateral ligament.The medial collateralligament maintains looseattachment to the pesanserinus, and the distal pe-riosteal attachments to the

ligament remain intact aswell, so the knee does notbecome grossly lax as a re-sult of this procedure. Thesecondary medial stabilisers(the medial posterior capsulein extension and the posteriorcruciate ligament in flexion)also are called into play, andprevent destabilization of theknee.

Fig.85. A thicker tibial com-ponent has been added totension all ligaments. Thedeep and superficial medialcollateral ligaments are freeof their distal attachments tobone, but remain attached tothe periosteum and deep fas-cia. Now the knee extendsfully. The stretched lateralstructures arc brought tonormal tension by the addi-tional tibial thickness. Thevarus deformity has beencorrected, and the mechanicalaxis of the femur is alignedwith the long axis of the tibia.

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Fig.86. The flexion contrac-ture has been corrected byreleasing the medial collat-eral ligament. Now the pos-terior capsule is brought toappropriate tension as the

knee extends fully, and actsas a secondary medial stabi-lizer in extension. If theknee will not extend fully,the medial posterior capsuleis the only remaining tightstructure, and may bereleased using the techniqueillustrated in Figures 77,78,174 and 175.

Fig.87. The effect is similar

in flexion. Now the femoralsurface is seated correctlyon the medial tibial surface.The posterior cruciateligament functions as asecondary varus-valgusstabilizer in flexion. Theanterior-posterior axis of thefemur passes through thecenter of the femoral headand aligns correctly with thelong axis of the tibia.

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Fig.88. Rarely, after release ofthe medial collateral liga-ment, the knee is still un-acceptably tight mediallybecause of contracted semi-membranosus and pesanserinus. These structuresshould be released from thetibia in these rare circum-stances. The semimem-branosus attachment can beexposed by placing aHohman retractor behind

the posterior medial edge ofthe tibial flare. The pesanserinus attachment is ac-cessible by extending thesubperiosteal release of themedial collateral ligamentanteriorly to include the ten-donfibers.

4.4. Tight Popliteus Tendon

Occasionally the popliteus tendon and its surrounding structures are

tight in the varus knee after the medial side has been corrected. Thisoften is difficult to detect, but rotational stability testing of the tibia

demonstrates that the tibia is held anteriorly on the lateral side and

pivots around the lateral edge of the tibial component.

Fig.89. The tibia is heldinternally rotated by thetight popliteus tendon,and the femoral surfaceseats far posteriorly onthe tibial surface.

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Fig.90. In the flexedposition the internalrotational malposition of thetibia is more apparent. Thetibia pivots around the tightpopliteus tendon. When thetibia is rotated around itslong axis, very littlemovement occurs laterally,

and near normal movementoccurs medially.

Fig.91. The lateral tibial sur-face is held abnormally faranteriorly by the tight pop-liteus complex. The popli-teus tendon is released fromits bone attachment with the

knee flexed. It is found Justdistal and posterior to thelateral collateral ligament at-tachment, and care must betaken to avoid release of thelateral collateral ligamentduring this procedure.

Fig.92. The popliteustendon has been releasedfrom its at-tach-ment to thefemur and has slidposteriorly, allowing thetibia to move posteriorly aswell. Now the femur sitsnormally on the tibial sur-

face.

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4.5. Compensatory Lateral Release -Extension onl y

Occasionally, after full medial collateral ligament release, the knee is

excessively loose on the medial side in extension, and tight laterally.Compensatory lateral release corrects the imbalance, and a thicker tibial

component brings the knee to correct stability.

Fig.93. After medialcollateral ligamentrelease, the knee gapes

medially and is tightlaterally in extension.

Fig.94. To correct thisimbalance, the iliotibialband is released tocreate more space in

extension

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Fig.95. A thicker tibial

component is added,bringing the knee tocorrect medial-lateralligament balance inextension. The lateralcollateral ligament andpopliteus tendon aretensioned on the lateralside, and the periostealattachments of the me-dial collateral ligamentare placed under tension.

Fig.96. Also, the medialposterior capsule, animportant secondarymedial stabilizer, is

brought to tension to en-hance this secondaryrole.

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4.6. Compensatory Lateral Release -Flexion and Extension

In some cases after full release of the medial collateral ligament, the

secondary stabilizers are inadequate to provide medial stability inflexion and extension, and the knee is too loose medially after the tibial

component has been sized to bring the lateral ligaments to their normal

tension. In those cases the lateral collateral ligament and popliteus

tendon are released to create more laxity both in flexion and extension,

and a thicker tibial component is used to tension the medial structures.

:Fig.97. The knee is

loose medially inextension after medialcollateral ligamentrelease.

Fig.98. The medial sidealso is loose in flexion.

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Fig.99. Compensatory

release of the lateralcollateral ligament makesroom for a larger tibialspacer especially inextension, but has someeffect through the entireflexion arc. This release isdone with a knife, releasingthe lateral collateralligament directly from thebone, but leaving it attachedto the surrounding densefibrous capsule, and to the

popliteus tendon.Compensatory release of thepopliteus tendon is done ifmore laxity is neededprimarily in flexion. Thelateral posterior capsule andposterolateral comer act assecondary stabilizingstructures if releases of thelateral collateral ligamentand popliteus tendon arenecessary.

Fig.100. A thicker polyethy-lene spacer tensions theknee appro-priately,tensioning the iliotibial bandand posterior capsule inextension. In some cases theiliotibial band must bepartially released to create alittle more compensatorylateral relaxation in the

extended position.

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'.

Fig.101. In flexion theposterior cruciateligament acts as the

major secondary stabi-lizer. Also, the popliteustendon or lateral collateralligament, if not released,will act as a secondarylateral stabilizingstructure.

4.7. Pitfalls of the Varus Knee

One of the most common causes of instability and patellar tracking

problems in the varus knee is the practice of early release of the medial

collateral ligament in extension, and then using tensioners to balancethe flexion space.

Fig.102. The varus knee

has medial tibialcollapse and contractureof the medial collateralligament.

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Fig.103. Full release of themedial collateral ligamentallows correction of thedeformity in extension.The posterior capsule isthe secondary medialstabilizer, and maintainsnormal medial stability inextension.

Fig.104. In flexion, whenthe tensioners are applied,the medial joint isdistracted until theposterior cruciate ligamentor the medial posteriorcapsule, which normallyare not tight in flexion,actually are tightened. Thisexternally rotates the

femur and the hip joint,tilts the epicondylar axislaterally, and positions thepatellar groove laterally.The tibia is now angledtoward valgus relative tothe femur in flexion. Thebone surface cuts are madeparallel to the tibialsurface. The knee will bestable, but alignment willbe in excessive valgus inflexion, and the new

position of the patellargroove will be medialized.

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Fig.105. The componentshave been inserted. The femurand hip are still externallyrotated. The epicondylar axisis tilted laterally, and thepatella is still positionedlaterally. The new patellargroove is positioned mediallyrelative to the femoral head,epicondylar axis, and patella.

Fig.106. When the hip is al-lowed to return to its normalfunctional position, the epi-condylar axis is parallel withthe ground, and the tibia isaligned in valgus. The long

axis of the tibia passes throughthis new patellar groove, butnot through the center of thefemoral head. The patella ispositioned laterally.

Fig.107. When the knee isextended, it is stable, and va-

rus-valgus alignment is cor-rect. However, the femoralcomponent is internally ro-tated, and the patellar grooveis medialized. The patella stillsits lateral to the new patellargroove. When the patella isplaced in the patellar groove,the Q-angle is excessive,approximately 30 in thisillustration.

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Suggested Readings

1. Anouchi YS, Whiteside LA, Kaiser AD, Milliano MT: The effect of axial rotational align-

ment of the femoral component on knee stability and patellar tracking in total knee

arthroplasty. Clin Orthop 287:170-177, 1991.2. Arima J, Whiteside LA: Femoral rotational alignment, based on the anterior-posterior axis, in

total knee arthroplasty in a valgus knee. J Bone Joint Surg 77A:1331-1334, 1995,

3. Burks RT: Gross Anatomy. In Daniel D, Akeson W, O'Connor J (eds). Knee Ligaments:

Structure, Function, Injury, and Repair. New York, Raven Press 59-76, 1990.

4. Grood E5, Noyes FR, Butler DJ, Suntay WJ: Ligamentous and capsular restraints preventing

straight medial and lateral laxity in intact human cadaver knees. ] Bone Joint Surg 63A:1257-

1269, 1981.

5. Grood ES, Stowers SF, Noyes FR: Limits of movement in the human knee. J Bone Joint Surg

70A:88-97, 1988.

6. Hull ML, Berns GS, Varma H, Patterson HA: Strain in the medial collateral ligament of the

human knee under single and combined loads. J Biomech 29:199-206, 1996.

7. Insall JN, Ranawat CS, Scott WN, Walker PS: Total condylar knee replacement. Clin Orthop

120:149-154, 1976.

8. Martin JW, Whiteside LA: The influence of joint line position on knee stability after condylarknee arthroplasty. Clin Orthop 259:146-156, 1990.

9. Matsuda S, Matsuda H, Miyagi T, Sasaki K, Iwamoto Y, Miura H: Femoral condyle geometry

in the normal and varus knee. Clin Orthop 349:183-188, 1998.

10. Nielson S, Ovesen J, Rasmussen O: The posterior cruciate ligament and rotatory knee

instability. An experimental study. Arch Orthop Trauma Surg 104:53-56, 1985.

11. Warren LP, Marshall JL The supporting structures and layers on the medial side of the knee. J

Bone Joint Surg 61A:56-62, 1979.

12. Warren LF, Marshall JL, Girgis F: The prime static stabilizer of the medial side of the knee. J

Bone Joint Surg 56A:665-674, 1974.

13. Whiteside LA. Intramedullary alignment of total knee replacement. A clinical and laboratory

study. Orthop Review (suppl) 9-12, 1989.

14. Whiteside LA: Correction of ligament and bone defects in total arthroplasty of the severely

valgus knee. Clin Orthop 288:234-245, 1993.

15. Whiteside LA: Ligament release and bone grafting in total arthroplasty of the varus knee.Orthopedics 18:117-122, 1995.

16. Whiteside LA, Arirna): The anterior-posterior axis for femoral rotational alignment in valgus

total knee arthroplasty, Clin Orthop 321:168-172, 1995.

17. Whiteside LA, Kasselt MR, Haynes DW: Varus and valgus and rotational stability in

rotationally unconstrained total knee arthroplasty. Clin Orthop 219:147-157, 1987.

18. Whileside LA, McCarthy DS: Laboratory evaluation of alignment and kinematics in a

unicompartmental knee arthroplasty inserted with intramedullary instrumentation. Clin Orthop

274:238-247, 1992.

19. Whiteside LA, Saeki K, Mihalko MW: Functional medial ligament balancing in total knee

arthroplasty. Clin Orthop 380:45-57, 2000.

20. Whiteside LA, Summers RG: Anatomical landmarks for an intramedullary alignment system

for total knee replacement. Orthop Trans 7:546-547, 1983.

21. Whiteside LA, Summers RG: The Effect of the Level of Distal Femoral Resection on

Ligament Balance in Total Knee Replacement. In Dorr LD (ed). The Knee: Papers cf the FirstScientific Meeting of the Knee Society. Baltimore, University Park Press 59-73, 1984.

22. Yoshii I, Whiteside LA, White SE, Milliano MT: Influence of prosthetic joint line position on

knee kinematics and patellar position. J Arthroplasty 6:169-177, 1991.

23. YoshiokaY, Siu D, Cooke TDV: The anatomy and functional axes of the femur. J Bone Joint

Surg 69A.-873-880, 1987.

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Valgus Knee

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5. Valgus Knee

Basic Principles

Ligament balancing in the valgus knee continues to challenge

arthroplasty surgeons despite advances in instrumentation for bone

resection and alignment. However, the application of basic principle

alignment allows the surgeon to correct deformity and eliminate

articular surface deficiencies by using reliable anatomic landmarks and

axes of the femur and tibia to position the components. Using the

central axis of the femur and tibia as a reference line for valgus angle

ensures highly reproducible alignment in the frontal plane. Using thedistal surface of the medial femoral condyle as the point of reference for

distal femoral resection ensures that the distal surface of the femur will

be in correct position relative to the medial ligaments and the patella.

The anterior-posterior axis of the distal femur provides a reliable line of

reference for rotational alignment of the femoral component so the

patellar groove, intercondylar notch, and condylar surfaces are posi-

tioned correctly, and the epicondylar axis is aligned perpendicular to the

mechanical axis of the femur and the long axis of the tibia in flexion

and extension. Effective ligament balance relies entirely on this

principle of first aligning the components correctly around these axes

and positioning the femoral joint surfaces equidistant from the

epicondylar axis throughout the arc of flexion. Extensive laboratory

studies of kinematics and ligament function in the knee, and exhaustive

clinical studies of ligament balancing during surgery and stability after

surgery, consistently confirm that using the intact side of the deformed

joint as a positioning reference for the joint surfaces throughout the

flexion and extension arc provides surfaces around which the ligaments

can be stabilized.

After correct alignment and positioning of the articular surfaces, a

strategy is necessary to ensure correct ligament balance throughout the

arc of flexion. Consideration of the functional effects of the lateral

stabilizing structures in flexion and extension offers a basis from which

to formulate this approach. A knee with contracture in the flexed andextended positions requires different procedures than one that is tight

only in extension. A knee that is tight only in flexion also should be

treated with different ligament release procedures than would be used

for one with ligament contractures that appear only in the extended

knee.

Ligaments that attach to the femur near the epicondyles, that is, near

the axis through which the tibia rotates as the knee flexes and extends,

function through the entire flexion arc of the knee. Those that attach to a

point distant from the epicondylar axis function effectively only in full

extension or in positions of fairly deep flexion. On the lateral side of the

knee the

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structures attaching to the femur near the epicondyle are the lateral collateral

ligament, the popliteus tendon, and the posterolateral corner capsule. The

lateral collateral ligament is a stabilizing structure in flexion and extension, and

has rotational and varus stabilizing effects. The popliteus tendon complex alsohas passive varus stabilizing effects in flexion and extension, but has a more

prominent role in external rotational stabilization of the tibia on the femur. The

posterolateral corner has primary stabilizing effects in extension, but also is

effective in flexion. These three structures are appropriate to release for a knee

that is excessively tight laterally in flexion and extension. The iliotibial band is

attached at a point above the knee far from the epicondylar axis, so it is aligned

perpendicular to the joint surface when the knee is extended. It can contribute

to lateral knee stability in this position, but when the knee is flexed to 90, it is

parallel to the joint surface, and cannot stabilize the knee to varus stress. The

lateral posterior capsular structures are tight only in full extension, and are

slack when the knee is flexed. Release of either the lateral posterior capsule or

the iliotibial band is appropriate only for a knee that is tight laterally inextension, and would have little effect on lateral knee stability in the flexed

position.

In the valgus knee, deficiency of the lateral femoral condyle distorts the

normal relationships of the mechanical axes, and restoration of normal

alignment must precede ligament balancing. Awareness of these principles

provides a rational plan for ligament releases in the valgus knee after total knee

arthroplasty

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Fig.108. In the valgus kneethe lateral femoral condyle isdeficient, usually distally andposteriorly, so the knee is invalgus both in the extendedand flexed positions. A val-

gus curvature usually existsin the mid-shaft of the femurand tibia, so that the linedown the midshaft diaphy-seal medullary canal crossesthe joint medial to the center.Entry points into the joint forintramedullary alignmentrods should be medialized5mm-10mm to accommodateand correct this valguscurvature.

Fig.109. The intramedullaryalignment rod lies slightlymedial to the center of thepatellar groove, and the cut-ting guide is set at a 5 valgusangle. This will align the joint

surface perpendicular to themechanical axis of the femur(a], and parallel to theepicondylar axis (b). Thecutting guide seats against thehigh (medial side, which isthe reference for resection ofthe joint surfaces. Thethickness of the implant isresected distally from themedial side. In some casesresection of the thickness ofthe implant from the medialside results in minimal or noresection from the lateral sideof the distal femur. Re-gardless of the lateral bonedeficit, the medial should beused as the reference surface,and augmentation of the lat-eral surface should be done tomake up for the deficit.

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Fig.110. Viewed from thedistal end, the femurusually can be seen to havedeficiency of the posteriorlateral femoral condylarsurfaces. The anterior-

posterior axis is especiallyhelpful for orientation ofvarus-valgus alignment ofthe valgus knee in flexion.The anterior-posterior axis,constructed from thecenter of the intercondylarnotch posteriorly throughthe deepest part of thepatellar groove, is perpen-dicular to the epicondylaraxis, and passes throughthe center of the femoral

head. If osteophytesobscure the edges of theintercondylar notch, thelateral edge of theposterior cruciate ligamentserves as a reliablelandmark for the center ofthe notch. The long axis ofthe tibia is no longer collinear with the anterior-posterior axis of the femur,but is angled towardvalgus as it is in full

extension,

Fig.111. The cutting guidefor femoral resection isaligned so the surfaces areresected perpendicular tothe anterior-posterior axisof the femur (a) andparallel with the epi-condylar axis (b),resecting the thickness ofthe implant from the intactmedial femoral condyle

(arrow),and much lessfrom the deficient lateralside. This places the jointsurfaces in anatomicposition to correct thevalgus position in flexion,and places the patellargroove correctly with themechanical axis of thelower extremity. The tibialsurface is resected perpen-dicular to the long axis ofthe tibia. The lateral

ligaments are still tight,and t

Whiteside - Ligament Balancing

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