Ebook Principles of deformity correction: Part 1

DROR PALEY

PRINCIPLES OF DEFORMITY CORRECTION


Springer-Verlag Berlin Heidelberg GmbH


DROR PALEY

PRINCIPLES OF

0 EFOR M I TV
CORRECTION
With Editorial Assistance from J. E. Herzenberg
With More Than 1,800 Separate Illustrations,
Clinical Photographs, and Radiographs

i

Springer


DROR PALEY,MD,FRCSC

Director, Rubin Institute for Advanced Orthopedics
Sinai Hospital
Co-Director, The International Center
for Limb Lengthening, Sinai Hospital
Baltimore, MD

Present address:
Rubin Institute for Advanced Orthopedics
Sinai Hospital
2401 West Belvedere Avenue
Baltimore, Maryland 21215-5271, USA
E-mail:
www.limblengthening.org
www.deformitycourse.com

ISBN 978-3-642-63953-1
ISBN 978-3-642-59373-4 (eBook)
DOI 10.1007/978-3-642-59373-4

1st ed. 2002. Corr. 3rd printing 2005
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~----------------------------------------------------

This book is dedicated to the memory of my father,
Zvi Paley, who gave so much and asked for so little.

...


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Foreword

What is genius? Analyzing complex problems and finding simple ways to explain them in an understandable
manner. By this definition, this book is genius.

The most dramatic progress in orthopaedic surgery
during the last 2 decades has been in the field of deformity correction. The treatment of deformities has occupied and challenged orthopaedic surgeons since Nicholas Andry. So many brilliant people have worked in this
field. Among them, Friedrich Pauwel and Gavril Ilizarov
should be individually named. Dr. Ilizarov developed
new methods oflimb lengthening and deformity correction and sparked the newfound interest and developments in this field today. In Dror Paley, this spark became a raging fire.
Dr. Paley inaugurated many innovations in the field
of deformity correction. Among them, his nomenclature
deserves special mention. Before his classification based
on joint orientation, we had a plethora of confusing
terminology and definitions leading to a confusion of
language reminiscent of the Tower of Babel. Dr. Paley's
nomenclature standardizes the terminology in a manner that requires little memorization. This logically
based system has gained international recognition and
acceptance as the single language of deformity analysis
and correction. This book presents us with these concepts.
The principles and concepts outlined in this book
were not discovered or understood overnight. They represent an evolution of Dr. Paley's ideas from the past
14 years of clinical work in the field of deformity correction. Unlike other texts, which come and go because they

are technique-centric, this tome is principle-based and
will therefore stand the test of time.
The limb lengthening and deformity reconstruction
center created by Drs. Paley and Herzenberg in Baltimore is not only the clinical laboratory where this deformity correction work was developed and understood
but has also become the Mecca for students in this medical specialty, with visitors from allover the world traveling to learn firsthand from these masters of deformity
correction. It is in this manner that I first became exposed to the CORA method of mechanical and anatomic axis planning. This has resulted in a long-standing collaboration between our two facilities, centered on our
common interest in this subspecialty. We routinely apply
these principles to deformity correction at our center in
Germany. Many of the new deformity correction devices that I and others are designing are now based on the
CORA principles.
Dr. Paley'S deformity correction courses around the

world have popularized the planning methods and principles espoused in this book. The annual Baltimore Limb
Deformity Course is the foundation for this book, workbook, and CD. Each of its chapters has been presented as
lectures at this course, and the workbook and multimedia CD have been tested by live audiences at these courses for many years.
I am sure this book will become the bible for the understanding, diagnosis, and treatment of lower limb deformities.
Wiesbaden, Germany

JOACHIM PFEIL


Preface

My prediction: this book will become a classic. Brave
words, but I can safely make this statement because this
book is not about the latest surgical operation or about
our knowledge of certain pathologies, which is constant1y changing. Rather, this book presents a system of deformity analysis that is universal and applicable to any
past, current, or future surgical osteotomy techniques
and hardware. One needs only to think back to medical
school and realize that most of the textbooks that we so
carefully studied are now "of historic interest only:'
Grant's Atlas of Anatomy is perhaps the only book from
my medical school days that I still use. I predict that Paley's Principles of Deformity Correction will also have a
long shelflife. The treatment of skeletal deformity is the
heart of our specialty. Indeed, the very name of our specialty, orthopaedics, was coined by Nicholas Andry in
1741 as a word derived from two Greek words, orthos
(meaning straight) and paedis (meaning child) to indicate his goal "to teach the different methods of preventing and correcting deformities of children" (from Mercer Rang's Anthology of Orthopaedics, 1966).
Since Andry's writings 260 years ago, little progress
has been made in understanding, analyzing, and quantifying the types of limb deformities. Rarely do we come
across an orthopaedic surgeon who is truly an artist (or
sculptor). Such an individual does not require accurate
preoperative planning to execute a flawless corrective

osteotomy. However, for the rest of us journeymen orthopaedic surgeons, achieving such beautiful artistic
and aesthetic outcomes is elusive. We tend to take a
wedge here or there, by eyeball estimation, and then
rationalize the less than perfect appearance of the final
X-ray. "It's not bad" or "it should remodel:' True, there
have been attempts by notable surgeons, such as Friedrich Pauwels and Maurice Mueller, to be more precise in
our planning. Although we may have received training
in the precise repositioning of fracture fragments with
plates and screws and accurate preoperative planning
and templating for hip osteotomies, what has eluded us
until now is a universally applicable lower extremity deformity planning system that takes into account the entire limb, including associated joint compensation and
lever arm considerations: a unified or universal system
that is equally applicable to the diverse range of ages and

pathological abnormalities that come under the purview of the adult and pediatric orthopaedist.
It has been my privilege and honor to be associated
professionally with Dr. Dror Paley for the past 10 years,
and I probably know him better than anyone else does. I
have therefore been in a unique position to observe how
he developed the CORA method and to contribute as a
co-developer, editor, and author. Dr. Paley has an uncanny knack of clearly seeing and understanding orthopaedic deformities. More importantly, he has a unique
ability to then process and integrate this information to
make it accessible to the less clairvoyant. We have
striven to make this method practical and teachable. It
is not hard to learn, but it does take some effort and
practice. The method is mercifully low-tech: the only
tools required are a pencil, ruler, and goniometer. We
have honed our ability to teach this method during the
past 10 years at our annual Baltimore Limb Deformity
Course, and many of the figures and cases illustrated in

this book have been used in the course. The case studies
and the artists' diagrams are all derived from our own
practices and are representative of deformities that we
have treated. In this regard, we are greatly indebted to
our patients for providing us with both typical and atypical problems to study and illustrate.
Interestingly, the CORA method of deformity analysis began simply as an attempt to make some sense of the
Ilizarov apparatus. As the orthopaedic surgeon who introduced this method in Canada and the USA, Dr. Paley
struggled to understand the concept of the Ilizarov
hinge, which is what made the Ilizarov fixator so unique
in its ability to correct deformities in a controlled fashion. In his early experience, he observed some of the secondary deformities that arose from mismatching the location of the hinge and the CORA. In his effort to more
accurately identify the level for the Ilizarov hinge, he derived the CORA method of mechanical and anatomic
axis planning described in this text.
He quickly realized that the concept of the CORA and
the osteotomy rules were not unique to the Ilizarov device but much more universally applicable to deformity
correction by any method. Indeed, with the CORA method, one can understand and plan surgery for any lower
extremity deformity from the hip to the foot. The gener-


al principle of this book is to first analyze, understand,
and quantify the deformity. Only then should you begin
to plan your surgical method and approach. Regardless
of which type and brand of fixation is selected (plates,
rods, or external fixator), the basic principles of deformity analysis and planning are the same. Failure to observe these principles frequently results in less than perfect alignment and often in secondary deformities that
may be more difficult to correct than the original deformities. Ultimately, the surgeon must decide which device works best in his or her hands. The first step of preoperative planning, however, is universally required and
beneficial. Chap. 11 includes a discussion of some of the
vagaries of selected hardware devices, and it is this chapter that will most likely require updating and revision in
a future edition as new device innovations become available. The bulk of the book, however, encompasses principles and concepts that will not change because they are
based on simple geometry.

Will the CORA method be supplanted by future technology? We think not. Even computer-dependent mathematical modeling of six-axis deformity correction (see

Chap. 12) is first dependent on the surgeon to accurately understand, analyze, and quantify the radiographic
deformity. We therefore think that the CORA method
complements rather than competes with such sophisticated deformity correction methods.
Is this book the final word on the topic? Clearly not. The
CORA method is still a work in progress, and there is
room to extend its application to the upper extremity,
spine, pelvis, and perhaps even maxillofacial deformity
correction. It has recently been incorporated into computer planning software. This book has already been
lO years in the making, and these other expansions will
have to wait for the second edition. We welcome readers'
comments, criticisms, and feedback to help us improve
future editions.
Baltimore, Maryland

JOHN E. HERZENBERG


The Story Behind This Book and the CORA Method

My first exposure to orthopaedics was as a medical student learning physical examination. My patient had a severe limp, which I attributed to weakness of his gluteus
medius. What today I would recognize as an obvious
Trendelenburg's gait, in 1977 was the pivotal event that
sparked my interest in orthopaedic surgery. I began to
read the works of Rene Caillet (The Biomechanics of
Joints) and of LA. Kapandji (Physiology ofJoints). Their
books made human mechanics easy to comprehend,
even for a medical student. With Principles of Deformity
Correction, I attempt to do the same regarding deformity analysis and treatment.
I am grateful to the many great teachers from my ortho-

paedic residency at the University of Toronto. They laid
the foundation for my interest in orthopaedics. Professor Robert Salter set the tone, teaching in a Socratic
manner. Dr. Alan Gross of Mt. Sinai Hospital first taught
me the concept of the mechanical axis of the lower limb
as well as the importance of preoperative planning for
osteotomies of the hip and knee. He frequently quoted
Renato Bombelli's Osteoarthritis of the Hip: Classification and Pathogenesis - The Role of Osteotomy as a
Consequent Therapy (Springer-Verlag, 1983) and Paul
Maquet's Biomechanics of the Knee: With Application to
the Pathogenesis and the Surgical Treatment of Osteoarthritis (Springer-Verlag, 1984), which stimulated me to
read these books on the biomechanics of the hip and
knee, respectively. Drs. David MacIntosh and Ian Harrington taught me controversial concepts of high tibial
osteotomies and alignment. Dr. Harrington's book on
biomechanics (Biomechanics of Musculoskeletal Injury;
Williams & Wilkins, 1982) and his often misunderstood
article on high tibial osteotomy UBJS 65(2):247-259,
1983] greatly influenced my understanding of concepts
in this field. Drs. Marvin Tile, Joseph Schatzker, Robert
McMurtry, and James Kellam are responsible for teaching me to think in terms of universal principles rather
than specific surgical techniques. Principles to orthopaedics are like laws to physics: they remain constant,
whereas specific operations and techniques come and
go.
The widest spectrum and complexity of deformity
occur in pediatric orthopaedics in that many conditions

-

affect the growth and development of the skeleton. My
teachers at the Hospital for Sick Children, Drs. Norris
Carroll, Colin Moseley, Mercer Rang, Walter Bobechko,

Robert Gillespie, and Robert Salter, provided my initial
exposure and understanding of the growth plate and the
pediatric skeleton. The training I received from them
during my residency and fellowship prepared me to
challenge many well-established practices and beliefs in
pediatric orthopaedics. Of all these, I received the greatest support from Dr. Norris Caroll, who always had faith
in me and invested his time and patience to teach me
meticulous surgical technique and who encouraged me
at times of despair.
I acknowledge the support of two of pediatric orthopaedics' elder statesmen, Drs. Lynn Staheli and Mihran
Tachdjian. Dr. Staheli, as editor of the Journal of Pediatric Orthopedics, invited me to write about current techniques of limb lengthening in 1988 UPO 8:73-92, 1988)
and more recently to write an editorial on deformity
correction in the twenty-first century UPO 20:279-281,
2000). Both of these publications helped introduce and
heighten awareness to deformity correction principles.
The late Dr. Tachdjian involved me in his internationally renowned pediatric orthopaedic review course since
1988 and included my deformity planning method in his
textbooks (Pediatric Orthopedics, 1990; and Atlas of Pediatric Orthopedic Surgery, 1994). Dr. Charles Price, who
took over this pediatric course, has included deformity
planning by the CORA method as an important theme
of the new course.
In November 1983, when I was a third-year orthopaedic resident in Toronto, I met Renato Bombelli who
was a visiting professor. Dr. Bombelli was a disciple of
Friedrich Pauwels and a contemporary of Maquet, another of Dr. Pauwels' disciples. Through their writings, I
began to understand that complicated joint mechanics
could be reduced to simple principles. While in Toronto,
Dr. Bombelli briefly mentioned the Ilizarov method.
This offhand comment sparked my interest in a field totally unknown in North America. Upon completing my
residency in 1985, I visited Dr. Maurizio Catagni in Italy
to learn more about the Ilizarov method. The next year,

I took my family to Europe and spent 6 months in Italy
and the USSR studying limb reconstruction with exter-


nal fixation. I learned that deformities could occur in
multiple planes and that hinges could act as the axis of
correction. I learned to consider not only angulation but
also translation, rotation, and length when analyzing a
deformity. I also learned that deformities could be corrected gradually or acutely and that there were virtually
no limits to how much angulation could be corrected.
I visited Kurgan three times during the Soviet era, and
I am greatly indebted to Professor Gavril Abramovich
Ilizarov for the opportunity to study at his institute. Although I learned a great deal from Dr. Ilizarov's lectures,
articles, and books, he was personally at his best when
examining patients. Physical examination was a skill
emphasized in my training in Toronto during the annual physical examination courses by Mr. Alan Graham
Aply. Learning Russian facilitated the learning process
and allowed me to speak to the Soviet doctors directly
without going through interpreters. Many people in
Kurgan contributed to my education, and some deserve
special mention. Igor Kataev taught me the principle of
hinges and of oblique plane deformity. Mr. Kataev was
not a physician but was in charge of the patent office at
Ilizarov's institute. Vladimir Shevtsov, Ilizarov's successor, answered the questions that I would not dare ask Ilizarov. He was direct and not evasive. Victor Makushin's
ability to clinically evaluate nonunions was uncanny but
could be divined only by reversing the Socratic method
I learned from Dr. Tile and the others in Toronto. Arnold
Popkov is a master at limb lengthening. He took the middle-of-the-road approach, allowing me to learn by answering my own questions and acknowledging when I
hit upon the correct answers. Others helped in a clandestine fashion to overcome the cold war Soviet secrecy of
the institute. The best example is Dr. Yaakov Odesky, who

is now in Israel. He allowed me to see treatments and
concepts that no Westerners had seen before. Finally,
Galena Dyachkova's openness helped me to understand
the basic science of the field of distraction, especially
regarding soft tissues.
In contrast to the struggle to learn in the USSR, Italy
presented a refreshing sense of openness. The team,
comprised of Roberto Cattaneo, Maurizio Catagni, and
Angelo Villa in Lecco, Fabio Argnani in Bergamo, and
Antonio Bianchi-Maiocchi in Milan, welcomed me with
sincerity, kindness, and warmth and did everything to
help me learn. I will forever be indebted to them. Of
these outstanding teachers, Dr. Catagni is most responsible for my current understanding of deformities. He
possesses an intuitive understanding of deformities and
essentially computes a CORA analysis in his head as well
as I can on paper. My goal with this book was to codify
Dr. Catagni's intuitive approach into the objective CORA
method that can be performed in a step-by-step fashion
by all. One more important event occurred before all the
pieces were in place. When I returned home from Italy
and the USSR and began my pediatric orthopaedic fel-

lowship in Toronto in 1987, I came across an article by
Dr. Ken Krackow (Adv Orthop Surg 7:69,1983). This article introduced me to the concept of joint orientation
angles and was pivotal in my developing the malalignment test.
With this foundation upon which to build, the CORA
method was developed. Placing hinges on the Ilizarov
device involved putting the hinge just below the ring for
metaphyseal deformities and at the apex of diaphyseal
deformities. It did not make sense that the hinge should

always be the same distance from the ring for all metaphyseal deformities. For diaphyseal deformities, we always drew two mid-diaphyseal lines and placed the
hinge at the intersection of the two lines. In the metaphysis, it was not possible to draw a mid-diaphyseal line
for the metaphyseal bone segment. I struggled with this
problem until March 1988, when I had to place hinges for
a supramalleolar osteotomy for ankle varus where the
joint line was clearly tilted around the lateral cortex of
the joint yet the osteotomy was much more proximal. Instead of placing the hinges just proximal to the distal tibial ring, I placed the hinge distal to the ring in what is
now recognized as a juxta-articular hinge construct (see
Chap. 11). To my fascination, the osteotomy site corrected with angulation and translation. The osteotomy rules
were born together with the CORA method. The basic
concepts in this book were developed over the next
2 years, based to the greatest extent on the clinical cases
I had the privilege and the challenge to treat but also on
a potpourri of ideas stimulated by colleagues with similar interests. Most notably, Stuart Green from California
was my sounding board, especially when it came to posttraumatic deformities. Together, we solved the mystery
of the relationship between the planes of angulation and
translation. I was privileged to have Dr. Kevin Tetsworth,
who has a brilliant mathematical mind, work with me as
a fellow between 1989 and 1990. In 1990, we published
the malalignment test and the first version of the CORA
method, although it was not yet called that (Clin Orthop
280:48-64; 65-71). Dr. Natsuo Yasui from Osaka, Japan,
coined the term CORA method, and it stuck.
The initial concept of writing a book about deformity
correction originated in 1991 through discussions with
Darlene Cooke, who was then a book editor at Williams
& Wilkins. The syllabus for the first annual Baltimore
Limb Deformity Course served as an outline for the
book. This course began in 1989, with Ilizarov as a featured guest speaker, and has continued ever since. The
success of this annual course led me to add more material and to incorporate the concepts of some very innovative contributors who participated in our course. Ms.

Cooke thought that I would never finish the book because I was a perfectionist and continued to add new
material every year. In many respects, she was right. On
the other hand, the book was not ready to be finished.
There were several concepts that were on the verge of


being clarified and that needed to be included in the
book to make it complete. For example, the six-axis deformity correction concepts introduced by Dr. J. Charles
Taylor and the lever arm deformity concepts presented
by Dr. James Gage. In 1998, Williams & Wilkins and I
agreed to drop the book project. Without Ms. Cooke as
my editor, the external push to complete the book was
gone. I saw 10 years of work to produce this book going
to waste. I decided upon a new strategy: finish the book
on our own, and then look for a publisher. With the help
of our in-house publishing team, Senior Editor Dori
Kelly, Medical Illustrator Joy Marlowe, and Multimedia
Specialist Mark Chrisman, this became a reality. It was
now time to seek a new publisher. This was easier said
than done. I could not get an American publishing company to share my vision of the importance of this book.
The project was finally salvaged by Dr. Joachim Pfeil, my
friend and colleague from Wiesbaden, Germany. Dr.
Pfeil has promoted the CORA method in Europe for
years and has co-authored an article on this subject in
the German language. He introduced me to Gabriele
Schroeder, Senior Medical Editor for Springer-Verlag in
Heidelberg in April 2000. This book has finally come to
fruition with the enthusiastic support of Springer-Verlag.
This history and my acknowledgments would not be
complete without mentioning a few more people. First is

Dr. John E. Herzenberg, without whose editorial assistance this book would not have been possible. Dr. Herzenberg has been my colleague and friend since we were
fellows together in Toronto in 1985 and 1986. We continued to correspond and collaborate at a distance until
1991, when Dr. Herzenberg moved to Maryland to help
achieve our common dream of developing a limb
lengthening and deformity correction center. The Maryland Center for Limb Lengthening & Reconstruction
(MCLLR) was born. John has been a valuable sounding
board for my ideas for more than 10 years. He encour-

aged me to continually strive to simplify my concepts to
make them teachable and practical. He has been my CoChairman in the Deformity Course and my loyal partner
in practice. It is often impossible to separate who originated which ideas. Therefore, this book is as much a testament to his work as it is to mine. Second is Anil Bhave,
PT. Mr. Bhave has directed our gait laboratory and
served as clinical research coordinator since 1992. He
has contributed immeasurably to my understanding of
gait and dynamic deformities. The rest of the loyal staff
of the MCLLR have also contributed to this book in one
way or another. Kernan Hospital and the Department of
Orthopaedics have given me tremendous support and a
wonderful environment for my work during the past
14 years. lowe them all a great debt of gratitude.
Finally, I would like to acknowledge my family. My
wife, Wendy Schelew, and our children, Benjamin,
Jonathan, and Aviva, have stood beside me all these years
and tolerated my single-minded devotion to completing
this project. This book is a testimony to their patience,
love, and support. It is also a testimony to my parents.
From my mother, a school teacher, I inherited ambition,
love for the life sciences, and my skill of teaching. My
greatest sadness is that my father, who was my role
model, will never see this book. He was a holocaust survivor who at age 38 (when I was 10) completed his PhD.

He was a mechanical engineer who specialized in metallurgy, working as a research scientist in Ottawa, Canada,
until his untimely death from cancer at age 54. My father
was a Renaissance man who spoke nine languages and
who stimulated my interest in many fields. Most of all, he
taught me to think critically. He grew up approximately
100 miles from Kurgan in the Soviet Union. He never got
to see me complete my residency, raise a family, learn
Russian, or achieve the publication of this book. It is to
his memory that I dedicate this book.
Baltimore, Maryland

DROR PALEY


Contributing Authors

I am indebted to the chapter contributors, without
whose input this book would be deficient. These select
authors were invited because of their original ideas and
contributions to the field of deformity correction. The
numbers and titles of the chapters to which they contributed are listed below their names. For the consistency of this book, I have edited and added to each of
these chapters to better incorporate these authors' ideas.
I especially thank my partner, John E. Herzenberg, who
in addition to contributing as an author to two chapters
in the book helped me to develop and also originated
many of the deformity concepts presented herein. John
acted as this book's content editor for both the text and
the figures. This laborious task has refined and clarified
the theoretical and practical principles that this book
presents.

DROR PALEY, MD, FRCSC

ANIL BHAVE,PT
Director of Rehabilitation and Gait Laboratory
The International Center for Limb Lengthening,
Sinai Hospital
Baltimore, MD
CHAPTER 21: Gait Considerations
JIM GAGE,MD
Medical Director, Gillette Children's Hospital
St. Paul,MN
Professor of Orthopaedics, University of Minnesota
Minneapolis, MN
CHAPTER 22: Dynamic Deformities and Lever Arm
Considerations
JOHN E. HERZENBERG, MD, FRCSC
Co-Director, The International Center
for Limb Lengthening, Sinai Hospital
Chief of Pediatric Orthopedics, Sinai Hospital
Baltimore, MD
CHAPTER 9: Rotation and Angulation-Rotation
Deformities
CHAPTER 12: Six-Axis Deformity Analysis
and Correction
CHAPTER 20: Growth Plate Considerations

MICHAEL MONT,MD
Co-Director, Joint Preservation and Replacement
Center, Sinai Hospital
Baltimore, MD

CHAPTER 23: Total Knee Replacement and Total
Hip Replacement Associated with
Malalignment
MICHAEL SCHWARTZ, PHD
Director of Bioengineering Research
Gillette Children's Hospital, St. Paul, MN
Assistant Professor of Orthopaedics
University of Minnesota
Minneapolis, MN
CHAPTER 22: Dynamic Deformities and Lever Arm
Considerations
SHAWN C. STANDARD, MD
Pediatric Orthopedic Surgeon
The International Center for Limb Lengthening,
Sinai Hospital
Baltimore, MD
CHAPTER 12: Six-Axis Deformity Analysis
and Correction
J. CHARLES TAYLOR,MD
Orthopedic Surgeon, Specialty Orthopedics
Memphis, TN
CHAPTER 12: Six-Axis Deformity Analysis
and Correction
KEVIN TETSWORTH,MD
Director of Orthopaedics, Royal Brisbane Hospital
Brisbane, Queensland, Australia
CHAPTER 13: Consequences of Malalignment


Senior Editor

DORI KELLY,MA

Medical Illustrators
JOY MARLOWE, MA
MARY GOLDSBOROUGH,MA
STACY LUND, MA

Multimedia Specialist
MARK CHRISMAN,Bs


Contributing Authors _

Drs. Dror Paley, MD, FReSe, and John E. Herzenberg, MD, FRese

DR 0 R PAL E Y was born in Tel Aviv, Israel, in 1956 and
moved to North America in 1960. He grew up in Ottawa,
Canada, for most of his youth. He graduated from the
University of Toronto Medical School in 1979, completed his internship in surgery at the Johns Hopkins Hospital in Baltimore in 1980, and completed his orthopaedic surgery residency at the University of Toronto
Hospitals in 1985. After completing a hand and trauma
surgery fellowship at Sunnybrook Hospital in Toronto
and the AOA-COA North American Traveling Fellowship, he spent 6 months studying limb lengthening and
reconstruction techniques in Italy and the USSR and
then completed a pediatric orthopaedics fellowship at
the Hospital for Sick Children in Toronto. This is where
he began his limb lengthening and deformity correction
experience. In November 1987, he organized the first international meeting on the Ilizarov techniques with Dr.
Victor Frankel, at which Professor Gavril Abramovich
Ilizarov shared his knowledge in the United States for
the first time. The same month, Dr. Paley joined the orthopaedic faculty of the University of Maryland. Many

of the original concepts for this book were developed
during the next 3 years. In 1991, Drs. John E. Herzenberg
and Kevin Tetsworth joined Dr. Paley to form the Mary-

land Center for Limb Lengthening & Reconstruction in
Baltimore.
In 1989, Dr. Paley organized and inaugurated ASAMINorth America, the limb lengthening and reconstruction society, and served as the first president of this new
subspecialty society. The first AS AMI meeting also coincided with the first Baltimore Limb Deformity Course.
The publication of this book will debut at the 11th Annual Baltimore Limb Deformity Course and will be the
manual of this internationally recognized course. Dr.
Paley has been active in teaching limb reconstruction
worldwide (more than 50 countries to date). He lectures
and reads in six languages (English, Hebrew, French,
Italian, Spanish, and Russian).
In 1990, Dr. Paley was awarded a Gubernatorial Citation for Outstanding Contributions in Orthopaedic Surgery by the Governor of Maryland. He was also awarded
the Pauwels Medal in Clinical Biomechanics by the German-Speaking Countries Orthopaedic Association in
1997. His most cherished award, however, is the Orthopaedic Residents Teaching Award, which he has received
on more than one occasion. Dr. Paley was the Chief of
Pediatric Orthopaedics at the University of Maryland
until June 2001 and was Professor of Orthopaedic Sur-


gery at the University of Maryland Medical System until
October 2003. He is well published in the peer-reviewed
literature and has also authored and edited several
books and numerous book chapters. He considers Principles of Deformity Correction to be his thesis and his
most important academic achievement. On July 1,2001,
Dr. Paley, together with Drs. John Herzenberg, Michael
Mont, and Janet Conway, opened the Rubin Institute for
Advanced Orthopedics at Sinai Hospital, in Baltimore.

Dr. Paley is the Director of this new orthopaedic center
and Co-Director of The International Center for Limb
Lengthening.
Dr. Paley is married to Wendy Schelew, and they have
three children (Benjamin, Jonathan, and Aviva). For fun,
he enjoys personal fitness, skiing, scuba diving, biking,
and studying history.

JOHN E. HERZENBERG was born in 1955 in Springfield, Massachusetts. At the age of 15, he left to attend
high school at Kibbutz Kfar Blum in Israel. He studied
medicine at Boston University and completed his internship in surgery at Albert Einstein-Montefiore Hospitals in New York. In 1985, he completed his residency
in orthopaedic surgery at Duke University in Durham,
NC, where he was drawn toward pediatric orthopaedics
by his mentor and chief, Dr. J. Leonard Goldner.
Dr. Herzenberg completed a pediatric orthopaedic
fellowship at the Hospital for Sick Children in Toronto,
where he first met Dr. Dror Paley. He was on the faculty
at the University of Michigan in Ann Arbor for 5 years,
with Dr. Robert Hensinger. Dr. Herzenberg traveled to Italy' USSR, and Baltimore to study limb reconstruction
techniques. This began his active collaboration with Dr.
Paley, which resulted in a joint vision to set up a national center devoted to limb reconstructive surgery. In 1991,
Dr. Herzenberg joined Drs. Paley and Tetsworth on the
full-time faculty of the University of Maryland in Baltimore to establish the Maryland Center for Limb Lengthening & Reconstruction.
Dr. Herzenberg has traveled extensively, teaching the
Ilizarov techniques and the CORA method of deformity
planning. He has served as president of ASAMI-North
America and is active as a volunteer surgeon with Operation Rainbow and Operation Smile, participating in
yearly missions to Central and South Americas. He was
awarded both the AOA-COA North American and ABC
Traveling Fellowships. He is extensively published in

many areas of pediatric orthopaedics and limb reconstruction. Dr. Herzenberg was Professor of Orthopaedic
Surgery at the University of Maryland Medical System
until October 2003 and is currently Co-Director of the
International Center for Limb Lengthening and Chief of
Pediatric Orthopedics at Sinai Hospital.

Dr. Herzenberg is married to Merrill Chaus, and they
have three daughters (Alexandra, Danielle, and Brittany). For fun, he enjoys personal fitness and Bible study.


Contents

1 Normal lower limb Alignment
and Joint Orientation ... 1

4 Frontal Plane Mechanical
and Anatomic Axis Planning ... 61

Mechanical and Anatomic Bone Axes . . .
Joint Center Points ...
Joint Orientation lines
. ...........

5
5
5
5
8

Joint Orientation Angles and Nomenclature . . . . ..

Mechanical Axis and Mechanical Axis Deviation (MAD).
Hip Joint Orientation .
Knee Joint Orientation . . . . . . . . . . . . . . . . .
Ankle Joint Orientation . . . . . . . . . . . . . . . . .
References. . . . . . . . . . . . . . . . . . . . . . . .

8
10
12
13
16
17

Ankle.
. ..... .
Knee. . . . . . . . . . .
Hip. . . . . . . . . . ..

2 Malalignment and Malorientation
in the Frontal Plane ... 19

Mechanical Axis Planning . . . . . . . . . . . . . ..
Anatomic Axis Planning . . . . . . . . . . . . . ..
Determining the CORA by Frontal Plane Mechanical
and Anatomic Axis Planning: Step by Step.
Part I: CORA Method, Tibial Deformities. . . . .
Mechanical Axis Planning
ofTibial Deformities . .
Anatomic Axis Planning
of Tibial Deformities. .

Part II: CORA Method, Femoral Deformities .
Mechanical Axis Planning
of Femoral Deformities
Anatomic Axis Planning
of Femoral Deformities

Multiapical Deformities . . . .

Malalignment . . . . . . . . . . . .
·
MAT . . . . . . . . . . . . . . . . . .
·
Malorientation of the Ankle and Hip
.
Orientation of the Ankle and Hip in the Frontal Plane
MOT of the Ankle . . . . . . . . . . . . . . . . . . .
MOT of the Hip.
References. . . . . . . . . . . . . . . . . . . . . . .

. 19
. 23

.
.
.
.
.

28

28
28
30
30

3 Radiographic Assessment
ofLower Limb Deformities ... 31

64
64
64
74
76
76
81

97

5 Osteotomy Concepts
and Frontal Plane Realignment ... 99

Angulation Correction Axis (ACA) . . . . . . . . . ..
Bisector Lines . . . . . . . . . . . . . . . . . . . . . .
Relationship of Osteotomy Type to Bisector Lines.
Osteotomy Rules . . . . . . . . . . . .
Translation and length Displacement
atthe Osteotomy Line . . . . . .
Opening Wedge Osteotomy. .
Closing Wedge Osteotomy. . . . . . . .

Knee . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Ankle and Hip . . . . . . . . . . . . . . . . . . . . . . 40
Radiographic Examination in the Sagittal Plane .... 46
Knee . . . . . . . . . . . . . . . . . . . . . . . . . 46
Ankle. . . . . . . . . . . . . . . . . . .
51

61
63

99
101
101
102
105
106
106

Focal Dome Osteotomy. . . . . . . . . . . .
Clinical Choice of Osteotomy Level and Type
Multiapical Osteotomy Solutions . . .

112
114
140
Single Osteotomy Solutions. . . . . . .
140
Multiple Osteotomy Solutions.
142
References . . . . . . . . . . . . . . . . . . . . . . . 154

Hip . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Radiographic Examination in One Plane
When There Is a Deformity Component
in the Other Plane
References. . . . . . . . . . . . . . . . . .

6 Sagittal Plane Deformities ... 155

. . 57
· . 60

Sagittal Plane Alignment in the lower Limb .
Sagittal Plane MAT . . . . . . .
Knee Joint Malorientation . . . . . . . . . . .

155
157
157


. . Contents

Overall Sagittal Plane MOT . . . . . . .
Knee Level Sagittal Plane MOT .... .
Overall Sagittal Plane MOT of the Ankle.
Ankle Level Sagittal Plane MOT of the Ankle
Sagittal Plane Anatomic Axis Planning
ofTibial Deformity Correction . . .

Sagittal Plane Anatomic Axis Planning
of Femoral Deformity Correction. .
Osteotomies in the Sagittal Plane.
References . . . . . . . . . . . . . . . .

159
163
163
165
165
169
169
174

7 Oblique Plane Deformities ... 175

Plane of Angulation . .
Graphic Method. . . . .
Graphic Method Error..
Base ofTriangle Method . . . . . . . .
Axis of Correction of Angulatory Deformities .
Definition of Angulation. .
References . . . . . . . . . . . . . . . . . . .

175
179
183
183
186
193

193

8 Translation and Angulation-Translation
Deformities ... 195

Translation Deformity . . . . . . . . . . .
Two Angulations Equal One Translation . .
Translation Effects on MAD ...
Osteotomies for Correction
ofTranslation Deformity . .
Combining Angulation and Translation . .
a-t Deformities and MAD . . . . .
Graphic Analysis of a-t Deformities . .
Type 1: Angulation and Translation
in the Same Plane. . . . . . .

· .. 195
· .. 200
· .. 200
.
·
·
·

202
203
205
205

. . 205

· 205
.208

Anatomic Plane Deformity . . . .
Oblique Plane Deformity . . . . . . . .

Type 2: Angulation and Translation
in Different Planes . . . . . . . . . . . . . . . . · 209
Anatomic Plane Deformity with Angulation
and Translation 90° Apart . . . . . . . . . . .
Oblique Plane Deformity with Angulation
and Translation 90° Apart . . . . . . . . . . .
One Anatomic and One Oblique Plane
Deformity with Angulation and Translation
in Different Planes Less Than 90° Apart ...
Oblique Plane Deformity with Angulation
and Translation Less Than 90° Apart.
.

211
214

216
. 218

Osteotomy Correction of a-t Deformities .
Osteotomy Correction of Angulation
and Translation in the Same Plane
Correction of Angulation and Translation
in Different Planes . . . . . .

Multilevel Fracture Deformities. . .
References . . . . . . . . . . . . . .

209

.. 219

. . 222
. .. 231
. . . . . 234

9 Rotation and Angulation-Rotation Deformities
... 235

Clinical Assessment of Rotation Deformities .
.
Level of Osteotomy for Rotation Deformities .
.
Frontal Plane Preoperative Planning
for Rotation Deformities . . . . . . . . .
.
Factoring in Rotation for Mechanical Axis
Planning of the Femur . . . . . . . . .
.
Frontal Plane Anatomic Axis Planning
for Rotation Deformities . . . . . . . .
.
Combined Angulation and Rotation Deformities . . .
Locating the Inclined Axis . . . . . . . . . . . .

.
Locating the Inclined Osteotomy
....
Inclined Focal Dome Osteotomy .
. . . . . .
Clinical Examples. . . .
. . .
References . . . . . . . . . . . .
. . . . . .

235
243
249
250
252
252
259
261
266
266
268

10 Length Considerations: Gradual Versus
Acute Correction of Deformities ... 269

Length Considerations for Angular Corrections.
.
Neurovascular Structures
. . . . . . .
.

Nerves . . . . . . . . . . . . .
.
Vessels . . . . . . . . . . . . . . .
·
Muscles, Tendons, and Fascia
·
Ligaments .. .
·
Skin .... .
·
References . . .
........

276
278
282
287
287
287
288
289

11 Ha rdware and Osteotomy Considerations
... 291

Choice of Hardware. . . .
Patient Age . . . . . .
Osteotomy Types. . .
Closing Wedge Osteotomy.
Opening Wedge Osteotomy . . . . .

Angulation-Translation Osteotomy.
Dome Osteotomy.
Hardware . . . . . . . . . .
Plate Fixation . . . . . .
Intramedullary Nails ..
External Fixation . .

Order of Correction. . .
Lever Arm Principle ..
Method of Osteotomy
References . . . . . . .

·
·
·
·
·
·
·
·
·
. .
..
·
·
·

291
291
291

291
297
300
300
300
300
307
346
383
387
389

· 410


Contents
, 6 Realign ment for Mono-com partment
Osteoarthritis of the Knee ... 479

12 Six-Axis Deformity Analysis and Correction
... 411

The Taylor Spatial Frame Fixator. .
· 412
Introduction . . . . . . .
· 412
Modes of Correction. .
· 416
Planning Methods . . .
· 418

Fracture Method . .
· 418
CORAgin Method ..
.420
CORAsponding Point Method . . . . . . . . . 422
Virtual Hinge Method . . . . . . . .
.424
Line of Closest Approach (LOCA) .
· .426
Taylor Computer-assisted Design
(CAD) Software. . . . . . . . . . .
· . 429
Reference Concepts . . . . . . . . . .
. . 429
Rate of Correction and Structure at Risk (SAR). 430
Parallactic Homologues of Deformity:
Proximal versus Distal Reference Perspective . . . 433
References . . . . . . . . . . . . . . . . . . . . . . . 436
13 Consequences of Malalignment . .. 437

Static Considerations. . . .
Dynamic Considerations . .
Rotational Considerations .
Animal Laboratory Models
Cadaver Laboratory Models
Clinical Longitudinal Studies . .
Summary.
References . . . . . . . . . . . .

· 438

.440
· 443
.444
.444
.446
· 448
. . . . 448

14 Malalignment Due to Ligamentous Laxity
ofthe Knee ... 4S 1

LCL Laxity.
MCL Laxity
References

Deformities in Association with MCOA .
.
Bone Deformities . .
.
Joint Deformities. . . . . . . . . . .
.
Customized HTO . . . . . . . . . . . . . . . .
.
Malalignment Test form Mono-Compartment
Osteoarthritis. . . . . . . . . . . . . . .
.
Femoral versus Tibial Osteotomy. . . . . .
.
Level of Center of Rotation of Angulation.
.

Magnitude of Correction . . . . . . .
. . .
Type of Osteotomy and Fixation . . . . .
.
Considerations. . . . . . . . . . . . . .. ...
Medial Compartment Osteoarthritis
Varus plus Medial Collateral
Ligament Pseudo laxity . . . . . . . . . . .
Medial Compartment Osteoarthritis
Varus plus Lateral Collateral
Ligament Pseudo laxity . . . . . . .. ..
Medial Compartment Osteoarthritis
Varus plus Rotation Deformity. . .. ..
Medial Compartment Osteoarthritis
Varus plus Hyperextension. . . . . . . . .
Medial Compartment Osteoarthritis
Varus plus Fixed Flexion Deformity. ..
Medial Compartment Osteoarthritis
Varus plus Lateral Subluxation. . . . . . .
Medial Compartment Osteoarthritis
Varus plus Medial Plateau Depression. . .
Lateral Compartment Osteoarthritis (LCOA)
.
References . . . . . . . . . . . . . . . . . . . . . . .

479
479
479
485
485

485
492
492
494
495

495

497
497
499
502
503
503
504
507

17 Sagittal Plane Knee Considerations ... 509

· . 451
· . 462
· .464

1S Knee Joint Li ne Deformity
Sources of Malalignment ... 465

References . . . . . . . . . . . . . . . . . . . . . . . 478

Frontal Plane Knee Considerations . .
FFD ofthe Knee . . . . . . . . . . . .

HE and Recurvatum Knee Deformity. .
Knee Extension Contracture . . . .
Patella Baja and Alta .
References . . . . . . . . . . . . .

·
·
·
·
·
·

.
.
.
.
.
.

509
509
538
563
568
569

18 Ankle and Foot Considerations ... 571

Frontal Plane Ankle Deformities ...
. ... 574

Supramalleolar Osteotomy for Varus
and Valgus Deformities. . . . . . .
. . . 579
Sagittal Plane Ankle Deformities . . .
. .. 581
Supramalleolar Osteotomy for Recurvatum
and Procurvatum Deformities . . . . . . . . . . . 585
Compensatory Mechanisms and Deformities:
Mobile, Fixed, and Absent. . . . . . . . . . . . . . 596


DIll

Contents

Specific Ankle Malalignment Deformities. . . . . .
Ankle Fusion Malunion . . . . . .
. .
Flattop Talus Deformity. . . . . . . . .
.
Ball and Socket Ankle Joint . . . . . . . . .. .
Overcorrected Clubfoot and Other Lateral
Translation Deformities of the Heel. . .
·
Posterior Tibial Tendon Dysfunction . . . . . . .
Completely Stiff Foot Treatment
by Supramalleolar Osteotomy. . .
·
Partial Growth Arrest . . .
·

Malunion of Fibula . . . .
·
Ankle Contractu res .
. .
References . . . . . . . . . . .
. ..

611
611
611
619
623
627
627
630
630
630
645

19 Hip Joint Considerations ... 647

Limb in Neutral Alignment to Pelvis, No Intraor Periarticular Limitation of Range of Motion
.
.
Varus Deformity. . . . . . . . .
Valgus Deformity . . . . . . . . . . . . . . . . .
Limb in Neutral Alignment to Pelvis,
Intra-articular Limitation of Range of Motion . . .
Varus Deformity. . . . . . . . . . . . . ..
.

Valgus Deformity . . . . . . . . . . . . . .
.
Lesser Trochanter Considerations . . . . . .. ...
Greater Trochanter Considerations . . . . . ..
.
Sagittal Plane Considerations . . . . . . . . ..
.
Deformities of the Head and Neck of the Femur. . . .
Pseudo-subluxation of the Hip . . . . . . . . . . . .
Deformities Due to Hip Ankylosis and Arthrodesis
between the Femur and the Pelvis. . .
.
Pelvic Support Osteotomy .
.
References . . . . . . . . . . . . . . . . .
·

..
. .
. .
.

705
705
705
708
708

710

710
715

21 Gait Considerations ... 717

647
647
653
653
653
653
656
660
672
673
684
686
689
694

20 Growth Plate Considerations ... 695

.
LLD . . . . . . . . . . .
Predicting LLD . . . . .
.
Multiplier Method .
Additional Growth Databases. . . . .
Relationship of Multipliers for Boys
to Multipliers for Girls. . . . . . .

Development of the Multiplier . . . .
Limb Length Discrepancy Prediction
Formulae . . . . . . . . . . . . . . . .
Prediction of Limb Length Discrepancy
at Skeletal Maturity Using the Multiplier
Growth-Remaining Method for Cases
of Postnatal Developmental Discrepancy.
Percentage of Total Bone Growth from the
Distal Femur and Proximal Tibia . . . ..
Using the Multiplier Method to Calculate
Timing for Epiphysiodesis. . . .
Growth Prediction Controversies. . . . . .

Growth Plate Considerations Relative
to Deformity. . . . . . . . . . . . . . . . . . . . .
Cause of Deformities . . . . . . . . . . . . . . .
Developmental Angular Deformities. . . . . . .
Angular Deformities: Gradual Correction
by Hemi-epiphysiodesis . . . . . . . . . . . . . . .
Planning for Hemi-epiphyseal Stapling for
Angular Correction at the Knee in Children .
Multiplier Method for Timing
Hemi-epiphyseal Stapling for Correction
of Angular Deformity . . . . . . . . . .. .
Multiplier Method for Calculating
When to Remove Hemi-epiphyseal Staples
in Young Children. .
References . . . . . . . . . . . . . . . . . . . . . . .

695

695
697
701

. 701
. . 702
.. 702

. 702
. 703
703
704

Gait Considerations in Association
with Lower Limb Deformities .
· ... 717
Sacrifice ofJoint Motion . . . .
· . 717
Fixed Joint Position . . . . . . .
· 718
Abnormal Loading ofJoints ...
· 721
Compensatory Mechanisms . . . .
· 721
Frontal Plane Malalignment. . . .
· 722
Distal Tibia Varus or Valgus. . . . . . . .
· 722
Varus Deformity at the Knee .
· . 725

Valgus Deformity of the Knee. . . . . .
· 732
Varus or Valgus Deformity of the
Proximal Femur. . . . .
· 735
Sagittal Plane Deformity. . . . . .
· 738
Ankle Equinus Deformity. . .
· 739
Excessive Ankle Dorsiflexion
or Calcaneus Deformity . . .
· 743
Ankle Arthrodesis Deformities.
· 744
Anterior Translation of the Foot .
· . 746
Fixed Flexion Deformity of the Knee. . · ... 749
Recurvatum of the Knee. . . . . . . .
· .. 751
Hip Flexion Deformity. . . . . . . . . . . · .. 751
. .... .
Hip Fusion. . . . . . . ..
· . 752
Rotational Malalignment . . . . . . . . .
· .. 753
Leg Length Considerations. . . . . . . . .
· 755
References . . . . . . . . . . . . . . . . .
· . . . 758
22 Dynamic Deformities and Lever Arm

Considerations ... 761

Levers . . . . . . . . .
·
Mechanical Advantage.
·
Moments and Motions .
·
Redundancy . . . .
·
Normal Function . . . .
·
Introduction . . . . . .
.. . . . .
.
Mechanics of the Ankle: First Rocker. . . . . . .

761
763
763
765
766
766
766


Contents _

Mechanics of the Ankle: Second Rocker . . . . .
Mechanics of the Ankle: Third Rocker . . . . . .

Force Production and Compensation . . .
·
Pathological Function .
·
Short Lever Arm . . . . . . . .
·
Flexible Lever Arm. . .
·
Malrotated Lever Arm. . .
·
Unstable Fulcrum . . . . .
·
Positional Abnormalities
·
References . . . . . . . . . . .
·

766
767
768
768
768
771
772
773
773
775

23 TKR and Total Hip Replacement
Associated with Malalignment ... 777

Normal Alignment Versus Malalignment
in Association with Total Knee Arthroplasty.
· 777
Management of Fixed Soft Tissue Deformities .
· 780
Clinical Assessment . . . . . . . . . . . . .
· 780
Radiographic Assessment . . . . . . . . . . .
· 780
Intraoperative Placement of Components
and Consequences of Malalignment . . . .
· 782
Varus Deformities . . . . . . . . .
· 783
Valgus Deformities. . . . . . . . .
· 783
Flexion Deformity and Contracture
· . 783
Recurvatum Deformity. . . . . . .
· . 786
Peroneal Nerve Palsy and Operative Release .
· . 786
Trial Reduction after Ligamentous Balancing.
· . 786
Summary of Soft Tissue Balancing Principles . . . . . 787
Extra-articular Bone Deformities . . . . .
. .. 788
Total Knee Arthroplasty after Failed HTO . . . .
792
Preoperative Assessment . . . . . . . . . . .

792
Proximal Tibial Osteotomy-Related Problems
forTKR . . . . . . . . . . . . . .
793
Proximal Femoral Deformities
and Total Hip Arthroplasty . . .
· 794
Preoperative Planning . . . . . . .
· 796
Soft Tissue Balancing. . . . .
· 797
Bone Deformity Correction.
· 797
References . . . . . . . . . .
· 797
Subject Index .. . 799


Glossary

a
A

ACA
ACL
AOTA
aJCO
aJCR
aJEO
aJER

aLOFA
AMA
AP
aPPTA
ASIS
a-t
CORA
0
OAA
OMA
F

FAN
FFO
GRV
HE
HTO
IMN
JLCA
L

LAT
IBL
LCL
LCOA
LOTA
LLO

anatomic
anterior

angulation correction axis
anterior cruciate ligament
anterior distal tibial angle
anatomic axis to joint center distance
anatomic axis: joint center ratio
anatomic axis to joint edge distance
anatomic axis:joint edge ratio
anatomic lateral distal femoral angle
anatomic-mechanical angle
anteroposterior (for radiograph)
anatomic posterior proximal tibial angle
anterior superior iliac spine
angulation-translation
center of rotation of angulation
distal
distal anatomic axis
distal mechanical axis
femur
fixator-assisted nailing
fixed flexion deformity
ground reaction vector
hyperextension
high tibial osteotomy
intramedullary nail
joint line convergence angle
lateral
lateral (for radiographic view only)
longitudinal bisector line
lateral collateral ligament
lateral compartment osteoarthritis

lateral distal tibial angle
limb length discrepancy

LOCA
LON
LPFA

line of closest approach
lengthening over nail
lateral proximal femoral angle
m
mechanical
M
medial
MAD
mechanical axis deviation
MAT
malalignment test
MCL
medial collateral ligament
MCOA medial compartment osteoarthritis
MOA
mid-diaphyseal angle
mLOFA mechanical lateral distal femoral angle
MM
medial malleolus
mMOFA mechanical medial distal femoral angle
MNSA medial neck shaft angle
MOT
malorientation test

MPFA medial proximal femoral angle
MPTA medial proximal tibial angle
NSA
neck shaft angle
P
posterior (when used in conjunction with
A for anterior, M for medial, and L for lateral)
P
proximal
PAA
proximal anatomic axis
POFA
posterior distal femoral angle
PPFA
posterior proximal femoral angle
PMA
proximal mechanical axis
PPTA
posterior proximal tibial angle
SA
surface area
SAR
structure at risk
SCFE
slipped capital femoral epiphysis
SO
standard deviation
T
tibia
transverse bisector line

tBL
TKR
total knee replacement
WBF
weight-bearing force


CHAPTER 1

_____________________________________________ 111

Normal Lower Limb Alignment and Joint Orientation

To understand deformities of the lower extremity, it is
important to first understand and establish the parameters and limits of normal alignment. The exact anatomy
of the femur, tibia, hip, knee, and ankle is of great importance to the clinician when examining the lower limb
and to the surgeon when operating on the bones and
joints. To better understand alignment and joint orientation, the complex three-dimensional shapes of bones
and joints can be simplified to basic line drawings, similar to the stick figures a child uses to represent a person
(~ Fig. I-I).

Furthermore, for purposes of reference, these line
drawings should refer to either the frontal, sagittal, or
transverse anatomic planes. The two ways to generate a
line in space are to connect two points and to draw a line
through one point at a specific angle to another line. All
the lines that we use for planning and for drawing schematics of the bones and joints are generated using one
of these two methods (~Fig.I-2).

a. ~----------------------------------4t

•....................~

.

b.

Fig. 1-2a,b
Two methods of drawing a line in space.
a Connect two points.
b Draw a line through one point at a specific angle to another
line.

Mechanical and Anatomic Bone Axes

Fig.1-1
Axis lines. A stick figure can be used as a schematic of a complex three-dimensional image of a person. In the same fashion,
axis and joint lines can be used to describe alignment and joint
orientation of the bones and joints of the lower limb.

Each long bone has a mechanical and an anatomic axis
(~Fig. 1-3). The mechanical axis of a bone is defined as
the straight line connecting the joint center points of the
proximal and distal joints. The anatomic axis of a bone
is the mid-diaphyseal line. The mechanical axis is always
a straight line connecting two joint center points, whether in the frontal or sagittal plane. The anatomic axis line
may be straight in the frontal plane but curved in the
sagittal plane, as in the femur. Intramedullary nails
(IMN) designed for the femur have a sagittal plane arc
to reflect this. In the tibia, the anatomic axis is straight in

_

CHAPTER 1· NormallowerLimbAlignmentandJointOrientation

b.

a.

Mechanical axis

Anatomic axis

c.

Mechanical axis

Mechanical axis

Anatomic axis

Mechanical axis

Anatomic axis

d.

Anatomic axis

Fig. 1-3 a-d

Fig. 1-4 a, b

~

Mechanical and anatomic axes of bones. The mechanical axis
is the line from the center of the proximal joint to the center of
the distal joint. The mechanical axis is always a straight line
because it is always defined from joint center to joint center.
Therefore, the mechanical axis line is straight in both the frontal and sagittal planes of the femur and tibia. The anatomic
axis of a long bone is the mid-diaphyseal line of that bone. In
straight bones (a,c), the anatomic axis follows the straight middiaphyseal path. In curved bones (b,d),it follows a curved middiaphyseal path. The anatomic axis can be extended into the
metaphyseal and juxta-articular portions of a bone by extending its mid-diaphyseal line in either direction.

a The tibial mechanical and anatomic axes are parallel but not
the same. The anatomic axis is slightly medial to the mechanical axis. Therefore, the mechanical axis of the tibia is
actually slightly lateral to the midline of the tibial shaft. Converse
y, the anatomic axis does not pass through the center
of the knee joint. It intersects the knee joint line at the medial tibial spine.
b The femoral mechanical and anatomic axes are not parallel.
The femoral anatomic axis intersects the knee joint line generally 1 cm medial to the knee joint center, in the vicinity of
the medial tibial spine. When extended proximally, it usually passes through the piriformis fossa just medial to the
greater trochanter medial cortex. The angle between the
femoral mechanical and anatomic axes (AMA) is 7±2°.

both frontal and sagittal planes (~Fig. 1-3). Axis lines
are applicable to any longitudinal projection of a bone.
For practical purposes, we refer only to the two anatomic planes, frontal and sagittal. The corresponding radiographic projections are the anteroposterior (AP) and
lateral (LAT) views, respectively.

In the tibia, the frontal plane mechanical and anatomic axes are parallel and only a few millimeters apart.
Therefore, the tibial anatomic-mechanical angle (AMA)
is 0° (~Fig. 1-4a). In the femur, the mechanical and anatomic axes are different and converge distally (~ Fig.
1-4b). The normal femoral AMA is 7±2°.


(HA PT ER 1 . Normal Lower Limb Alignment and Joint Orientation _

a.

(

Mechanical axis

Anatomic axis

Mechanical axis

Anatomic axis

;V

Mechanical
axis

~natomi
c
axis

b.

Mechanical
axis

Anatomic
axis