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al principle of this book is to first analyze, understand,and quantify the deformity. Only then should you beginto plan your surgical method and approach. Regardlessof 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 thatmay 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 andbeneficial. Chap. 11 includes a discussion of some of thevagaries of selected hardware devices, and it is this chapter that will most likely require updating and revision ina future edition as new device innovations become available. The bulk of the book, however, encompasses principles and concepts that will not change because they arebased 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 (seeChap. 12) is first dependent on the surgeon to accurately understand, analyze, and quantify the radiographicdeformity. We therefore think that the CORA methodcomplements rather than competes with such sophisticated deformity correction methods.Is this book the final word on the topic? Clearly not. TheCORA method is still a work in progress, and there isroom to extend its application to the upper extremity,spine, pelvis, and perhaps even maxillofacial deformitycorrection. It has recently been incorporated into computer planning software. This book has already beenlO years in the making, and these other expansions willhave to wait for the second edition. We welcome readers'comments, criticisms, and feedback to help us improvefuture editions.Baltimore, MarylandJOHN E. HERZENBERG

The Story Behind This Book and the CORA MethodMy 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 gluteusmedius. What today I would recognize as an obviousTrendelenburg's gait, in 1977 was the pivotal event thatsparked my interest in orthopaedic surgery. I began toread the works of Rene Caillet (The Biomechanics ofJoints) and of LA. Kapandji (Physiology ofJoints). Theirbooks made human mechanics easy to comprehend,even for a medical student. With Principles of DeformityCorrection, 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 laidthe foundation for my interest in orthopaedics. Professor Robert Salter set the tone, teaching in a Socraticmanner. Dr. Alan Gross of Mt. Sinai Hospital first taughtme the concept of the mechanical axis of the lower limbas well as the importance of preoperative planning forosteotomies of the hip and knee. He frequently quotedRenato Bombelli's Osteoarthritis of the Hip: Classification and Pathogenesis - The Role of Osteotomy as aConsequent Therapy (Springer-Verlag, 1983) and PaulMaquet's Biomechanics of the Knee: With Application tothe Pathogenesis and the Surgical Treatment of Osteoarthritis (Springer-Verlag, 1984), which stimulated me toread these books on the biomechanics of the hip andknee, respectively. Drs. David MacIntosh and Ian Harrington taught me controversial concepts of high tibialosteotomies and alignment. Dr. Harrington's book onbiomechanics (Biomechanics of Musculoskeletal Injury;Williams & Wilkins, 1982) and his often misunderstoodarticle on high tibial osteotomy UBJS 65(2):247-259,1983] greatly influenced my understanding of conceptsin this field. Drs. Marvin Tile, Joseph Schatzker, RobertMcMurtry, and James Kellam are responsible for teaching me to think in terms of universal principles ratherthan specific surgical techniques. Principles to orthopaedics are like laws to physics: they remain constant,whereas specific operations and techniques come andgo.The widest spectrum and complexity of deformityoccur in pediatric orthopaedics in that many conditions-affect the growth and development of the skeleton. Myteachers at the Hospital for Sick Children, Drs. NorrisCarroll, Colin Moseley, Mercer Rang, Walter Bobechko,Robert Gillespie, and Robert Salter, provided my initialexposure and understanding of the growth plate and thepediatric skeleton. The training I received from themduring my residency and fellowship prepared me tochallenge many well-established practices and beliefs inpediatric orthopaedics. Of all these, I received the greatest support from Dr. Norris Caroll, who always had faithin me and invested his time and patience to teach memeticulous surgical technique and who encouraged meat times of despair.I acknowledge the support of two of pediatric orthopaedics' elder statesmen, Drs. Lynn Staheli and MihranTachdjian. 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 deformitycorrection in the twenty-first century UPO 20:279-281,2000). Both of these publications helped introduce andheighten awareness to deformity correction principles.The late Dr. Tachdjian involved me in his internationally renowned pediatric orthopaedic review course since1988 and included my deformity planning method in histextbooks (Pediatric Orthopedics, 1990; and Atlas of Pediatric Orthopedic Surgery, 1994). Dr. Charles Price, whotook over this pediatric course, has included deformityplanning by the CORA method as an important themeof the new course.In November 1983, when I was a third-year orthopaedic resident in Toronto, I met Renato Bombelli whowas a visiting professor. Dr. Bombelli was a disciple ofFriedrich Pauwels and a contemporary of Maquet, another of Dr. Pauwels' disciples. Through their writings, Ibegan to understand that complicated joint mechanicscould 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 myresidency in 1985, I visited Dr. Maurizio Catagni in Italyto learn more about the Ilizarov method. The next year,I took my family to Europe and spent 6 months in Italyand the USSR studying limb reconstruction with exter-

nal fixation. I learned that deformities could occur inmultiple planes and that hinges could act as the axis ofcorrection. I learned to consider not only angulation butalso translation, rotation, and length when analyzing adeformity. I also learned that deformities could be corrected gradually or acutely and that there were virtuallyno limits to how much angulation could be corrected.I visited Kurgan three times during the Soviet era, andI am greatly indebted to Professor Gavril AbramovichIlizarov 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 whenexamining patients. Physical examination was a skillemphasized in my training in Toronto during the annual physical examination courses by Mr. Alan GrahamAply. Learning Russian facilitated the learning processand allowed me to speak to the Soviet doctors directlywithout going through interpreters. Many people inKurgan contributed to my education, and some deservespecial mention. Igor Kataev taught me the principle ofhinges and of oblique plane deformity. Mr. Kataev wasnot a physician but was in charge of the patent office atIlizarov'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'sability to clinically evaluate nonunions was uncanny butcould be divined only by reversing the Socratic methodI learned from Dr. Tile and the others in Toronto. ArnoldPopkov 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 Ihit upon the correct answers. Others helped in a clandestine fashion to overcome the cold war Soviet secrecy ofthe institute. The best example is Dr. Yaakov Odesky, whois now in Israel. He allowed me to see treatments andconcepts that no Westerners had seen before. Finally,Galena Dyachkova's openness helped me to understandthe basic science of the field of distraction, especiallyregarding soft tissues.In contrast to the struggle to learn in the USSR, Italypresented a refreshing sense of openness. The team,comprised of Roberto Cattaneo, Maurizio Catagni, andAngelo Villa in Lecco, Fabio Argnani in Bergamo, andAntonio Bianchi-Maiocchi in Milan, welcomed me withsincerity, kindness, and warmth and did everything tohelp me learn. I will forever be indebted to them. Ofthese outstanding teachers, Dr. Catagni is most responsible for my current understanding of deformities. Hepossesses an intuitive understanding of deformities andessentially computes a CORA analysis in his head as wellas I can on paper. My goal with this book was to codifyDr. Catagni's intuitive approach into the objective CORAmethod that can be performed in a step-by-step fashionby all. One more important event occurred before all thepieces were in place. When I returned home from Italyand the USSR and began my pediatric orthopaedic fel-lowship in Toronto in 1987, I came across an article byDr. Ken Krackow (Adv Orthop Surg 7:69,1983). This article introduced me to the concept of joint orientationangles and was pivotal in my developing the malalignment test.With this foundation upon which to build, the CORAmethod was developed. Placing hinges on the Ilizarovdevice involved putting the hinge just below the ring formetaphyseal deformities and at the apex of diaphysealdeformities. It did not make sense that the hinge shouldalways be the same distance from the ring for all metaphyseal deformities. For diaphyseal deformities, we always drew two mid-diaphyseal lines and placed thehinge at the intersection of the two lines. In the metaphysis, it was not possible to draw a mid-diaphyseal linefor the metaphyseal bone segment. I struggled with thisproblem until March 1988, when I had to place hinges fora supramalleolar osteotomy for ankle varus where thejoint line was clearly tilted around the lateral cortex ofthe 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 isnow recognized as a juxta-articular hinge construct (seeChap. 11). To my fascination, the osteotomy site corrected with angulation and translation. The osteotomy ruleswere born together with the CORA method. The basicconcepts in this book were developed over the next2 years, based to the greatest extent on the clinical casesI had the privilege and the challenge to treat but also ona potpourri of ideas stimulated by colleagues with similar interests. Most notably, Stuart Green from Californiawas my sounding board, especially when it came to posttraumatic deformities. Together, we solved the mysteryof the relationship between the planes of angulation andtranslation. I was privileged to have Dr. Kevin Tetsworth,who has a brilliant mathematical mind, work with me asa fellow between 1989 and 1990. In 1990, we publishedthe malalignment test and the first version of the CORAmethod, although it was not yet called that (Clin Orthop280:48-64; 65-71). Dr. Natsuo Yasui from Osaka, Japan,coined the term CORA method, and it stuck.The initial concept of writing a book about deformitycorrection originated in 1991 through discussions withDarlene Cooke, who was then a book editor at Williams& Wilkins. The syllabus for the first annual BaltimoreLimb Deformity Course served as an outline for thebook. This course began in 1989, with Ilizarov as a featured guest speaker, and has continued ever since. Thesuccess 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 newmaterial every year. In many respects, she was right. Onthe 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 thebook to make it complete. For example, the six-axis deformity correction concepts introduced by Dr. J. CharlesTaylor and the lever arm deformity concepts presentedby Dr. James Gage. In 1998, Williams & Wilkins and Iagreed to drop the book project. Without Ms. Cooke asmy editor, the external push to complete the book wasgone. I saw 10 years of work to produce this book goingto waste. I decided upon a new strategy: finish the bookon our own, and then look for a publisher. With the helpof our in-house publishing team, Senior Editor DoriKelly, Medical Illustrator Joy Marlowe, and MultimediaSpecialist Mark Chrisman, this became a reality. It wasnow time to seek a new publisher. This was easier saidthan 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, myfriend and colleague from Wiesbaden, Germany. Dr.Pfeil has promoted the CORA method in Europe foryears and has co-authored an article on this subject inthe German language. He introduced me to GabrieleSchroeder, Senior Medical Editor for Springer-Verlag inHeidelberg in April 2000. This book has finally come tofruition with the enthusiastic support of Springer-Verlag.This history and my acknowledgments would not becomplete without mentioning a few more people. First isDr. John E. Herzenberg, without whose editorial assistance this book would not have been possible. Dr. Herzenberg has been my colleague and friend since we werefellows together in Toronto in 1985 and 1986. We continued to correspond and collaborate at a distance until1991, when Dr. Herzenberg moved to Maryland to helpachieve our common dream of developing a limblengthening and deformity correction center. The Maryland Center for Limb Lengthening & Reconstruction(MCLLR) was born. John has been a valuable soundingboard for my ideas for more than 10 years. He encour-aged me to continually strive to simplify my concepts tomake them teachable and practical. He has been my CoChairman in the Deformity Course and my loyal partnerin 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 andserved as clinical research coordinator since 1992. Hehas contributed immeasurably to my understanding ofgait and dynamic deformities. The rest of the loyal staffof the MCLLR have also contributed to this book in oneway or another. Kernan Hospital and the Department ofOrthopaedics have given me tremendous support and awonderful environment for my work during the past14 years. lowe them all a great debt of gratitude.Finally, I would like to acknowledge my family. Mywife, Wendy Schelew, and our children, Benjamin,Jonathan, and Aviva, have stood beside me all these yearsand tolerated my single-minded devotion to completingthis 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. Mygreatest sadness is that my father, who was my rolemodel, 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 fatherwas a Renaissance man who spoke nine languages andwho stimulated my interest in many fields. Most of all, hetaught me to think critically. He grew up approximately100 miles from Kurgan in the Soviet Union. He never gotto see me complete my residency, raise a family, learnRussian, or achieve the publication of this book. It is tohis memory that I dedicate this book.Baltimore, MarylandDROR PALEY

Contributing AuthorsI am indebted to the chapter contributors, withoutwhose input this book would be deficient. These selectauthors were invited because of their original ideas andcontributions to the field of deformity correction. Thenumbers 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 ofthese chapters to better incorporate these authors' ideas.I especially thank my partner, John E. Herzenberg, whoin addition to contributing as an author to two chaptersin the book helped me to develop and also originatedmany of the deformity concepts presented herein. Johnacted as this book's content editor for both the text andthe figures. This laborious task has refined and clarifiedthe theoretical and practical principles that this bookpresents.DROR PALEY, MD, FRCSCANIL BHAVE,PTDirector of Rehabilitation and Gait LaboratoryThe International Center for Limb Lengthening,Sinai HospitalBaltimore, MDCHAPTER 21: Gait ConsiderationsJIM GAGE,MDMedical Director, Gillette Children's HospitalSt. Paul,MNProfessor of Orthopaedics, University of MinnesotaMinneapolis, MNCHAPTER 22: Dynamic Deformities and Lever ArmConsiderationsJOHN E. HERZENBERG, MD, FRCSCCo-Director, The International Centerfor Limb Lengthening, Sinai HospitalChief of Pediatric Orthopedics, Sinai HospitalBaltimore, MDCHAPTER 9: Rotation and Angulation-RotationDeformitiesCHAPTER 12: Six-Axis Deformity Analysisand CorrectionCHAPTER 20: Growth Plate ConsiderationsMICHAEL MONT,MDCo-Director, Joint Preservation and ReplacementCenter, Sinai HospitalBaltimore, MDCHAPTER 23: Total Knee Replacement and TotalHip Replacement Associated withMalalignmentMICHAEL SCHWARTZ, PHDDirector of Bioengineering ResearchGillette Children's Hospital, St. Paul, MNAssistant Professor of OrthopaedicsUniversity of MinnesotaMinneapolis, MNCHAPTER 22: Dynamic Deformities and Lever ArmConsiderationsSHAWN C. STANDARD, MDPediatric Orthopedic SurgeonThe International Center for Limb Lengthening,Sinai HospitalBaltimore, MDCHAPTER 12: Six-Axis Deformity Analysisand CorrectionJ. CHARLES TAYLOR,MDOrthopedic Surgeon, Specialty OrthopedicsMemphis, TNCHAPTER 12: Six-Axis Deformity Analysisand CorrectionKEVIN TETSWORTH,MDDirector of Orthopaedics, Royal Brisbane HospitalBrisbane, Queensland, AustraliaCHAPTER 13: Consequences of Malalignment

Senior EditorDORI KELLY,MAMedical IllustratorsJOY MARLOWE, MAMARY GOLDSBOROUGH,MASTACY LUND, MAMultimedia SpecialistMARK CHRISMAN,Bs

Contributing AuthorsDrs. Dror Paley, MD, FReSe, and John E. Herzenberg, MD, FReseDR 0 R PAL E Y was born in Tel Aviv, Israel, in 1956 andmoved to North America in 1960. He grew up in Ottawa,Canada, for most of his youth. He graduated from theUniversity 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 TorontoHospitals in 1985. After completing a hand and traumasurgery fellowship at Sunnybrook Hospital in Torontoand the AOA-COA North American Traveling Fellow

Rubin Institute for Advanced Orthopedics Sinai Hospital 2401 West Belvedere Avenue Baltimore, Maryland 21215-5271, USA E-mail: dpaley@lifebridgehealth.org 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