Table Of ContentA Primer of Biomechanics
Springer Science+Business Media, LLC
George L. Lucas, M.D.
Francis W. Cooke, Ph.D.
Elizabeth A. Friis, Ph.D.
A Primer
of 8iomechanics
Illustrations by Danielle Y. Chinn
With 146 Illustrations
Springer
George L. Lucas, M.D. Elizabeth A. Friis, Ph.D.
Professor and Chainnan, Department of Research Scientist, Orthopaedic Research
Surgery, Division of Orthopaedic Institute, Inc., Via Christi Regional
Surgery, University of Kansas School Medical Center-St. Francis Campus
of Medicine, Wichita, KS 67214, USA Research Instructor, Department of
Surgery, Division of Orthopaedic
Francis W. Cooke, Ph.D. Surgery, University of Kansas School
Research Director, Orthopaedic of Medicine, Wichita, KS 67214,
Research Institute, Inc., Via Christi USA
Regional Medical Center-St. Francis
Campus Daoielle Y. Chioo
Research Professor, Department of Graphic Designer/lllustrator, dc design
Surgery, Division of Orthopaedic
Surgery, University of Kansas School
of Medicine, Wichita, KS 67214, USA
Library of Coogress Cataloging-in-Publication Data
Lucas, George L.
A primer of biomechanics / George L. Lucas, Francis W. Cooke,
Elizabeth A. Friis.
p. cm.
Includes bibliographical references and index.
ISBN 978-0-387-98456-8 ISBN 978-1-4419-8487-6 (eBook)
DOI 10.1007/978-1-4419-8487-6
1. Human mechanics. 2. Orthopedics. 1. Cooke, Francis W.
II. Friis, Elizabeth. III. Title.
QP303.L83 1998
612.7'6-dc21 97-48865
Printed on acid-free paper.
© 1999 Springer Science+Business Media New York
Originally published by Springer-Verlag New York, Inc.in 1999
AlI rights reserved. This work may not be translated or copied in whole or in part with
out the written permission of the publisher (Springer Science+Business Media, LLC),
except for brief excerpts in connection with reviews or scholarly analysis. Use in connec
tion with any form of infonnation storage and retrieval, electronic adaptation, comput
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is forbidden.
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even if the former are not especially identified, is not to be taken as a sign that such
names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly
be used freely by anyone.
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date of going to press, neither the authors nor the editors nor the publisher can accept any
legal responsibility for any errors or omissions that may be made. The publisher makes
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Production coordinated by Impressions Book and Joumal Services, Inc., and managed
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Typeset by Impressions Book and Joumal Services, Inc., Madison, WI.
987 6 5 432 1
ISBN 978-0-387-98456-8 SPIN 10659576
This book is dedicated to the residents in orthopaedic
surgery-past,present, andfuture-who have studied our
syllabus on biomechanics, worked through the demonstra
tionproblems, and worked with us inthe laboratory.
Preface
Asubstantial knowledge ofbiomechanics andbiomaterials isessential
fortoday'sorthopaedicsurgeon.Unfortunately,mostofusdonotcome
from an engineering background, and much of the writing about bio
mechanics is difficult for us to understand. This is particularly true
whenamathematicalformula isutilized because,even ifonehastaken
calculus incollege, such skills are quickly forgotten if not used regu
larly.Afew simple formulas areessential forclarity,andremembering
afew basic ones can come in handy when taking the Orthopaedic In
Training Examination or perhaps Part Iof the American Board of Or
thopaedic Surgery Examination, but none of the formulas in this book
require anything beyond a rudimentary recolIection of basic algebra.
Inaneffort to understand how andwhy apatient'sbone broke,how
torepair such afracture,orwhy acertain repair technique did notsuc
ceed, orthopaedic surgeons constantly employ a knowledge of and
appreciation formechanics, forces, forcedimensions,velocity,andnu
merous other concepts related to biomechanics.Thus we need to un
derstand asclearly as possible, without resorting to complex analyses
ormathematicalcalculations,asmuchabout biomechanicsasispracti
cal.This book provides fundamental knowledge about the subject ina
highly readable andunderstandablefashion. Wehave attempted tode
mystify the subject of biomechanics while providing the student, or
thopaedic resident, oreven practicing orthopaedistwithbasicconcepts
thatwilIheighten their understandingofclinical situations.Oneofour
basic techniques of teaching orthopaedics is toencourageresidents to
relate what they have read intexts orjournals to specificpatients they
have seen.Reaching back into one's mind to recalI how a similar pa
tientwastreated ismuchmoreeffective thantryingtoremembersome-
vii
viii Preface
thing read out of context in a textbook on fractures, for example. By
providingbrief,clinical vignettestointroducevarious subtopicsofbio
mechanics, reader interest and focus is, in our view, significantly en
hanced.Wehope that readerswill findthis approach arefreshing way
to come to grips with what is sometimes considered a "dry" subject.
GEORGEL.LUCAS, M.D.
FRANCISW.COOKE, PH.D.
ELIZABETH A.FRIIS, PH.D.
Acknowledgments
Thisbook,likeallothers,hasbeenbothalaborofloveandatestofour
will.Also,likeallother books, thiswork isnotexclusivelytheproduct
oftheauthors, andweacknowledgetheassistance andsupportofmany
others.Weareespecially grateful tothefollowing persons:
Our families for their patient understanding and forbearance during
this period
Dustan Hahn,former research assistant intheOrthopaedic Research
Institute, withwhom theideawas firstdiscussed
Juanita RidgewayandRita Baker,our secretaries, forhelp with sec
retarial details
The hospital volunteers who helped with proofreading,typing, and
photocopying
Via Christi Regional Medical Center (St. Francis) for facility and
personnel support
Charles Graberfor assistance inthelaboratory
Christoph Roth and Gunther Becht for assistance with generating
figuresforand editing ofChapter 11
James Carr,MD, DanGurley,MD, Craig Hansen, MD,ToddSwen
ning, MD, and Lance Snyder, MD (orthopaedic residents) for their
careful review ofthedeveloping manuscript andtheir helpful sug
gestions
John Osland, MD, forhis work incritiquing Chapter 7
DavidA.McQueen,MD,forhis work incritiquing Chapter 11
ix
x Acknowledgments
Danielle Chinn,whose name appropriatelyappears onthetitlepage,
forhersuperb illustrations,whichweredone undersignificanttime
constraints
Esther Gumpert, Anna Fossella, and Josh Paul of Springer-Verlag,
New York,for their patience, understanding,assistance, and faith.
G.L.L.
EW.e.
E.A.E
Contents
Preface vii
Acknowledgments ix
Mechanics 1
QI: Clinical Question:DistractionForceinTraction 1
1.1 Mechanics 2
1.2 Newton'sLaws 4
1.3 Characteristics ofForces 5
1.3.1 Magnitude 5
1.3.2 Direction 5
1.3.3 Vectors 6
1.3.4 Point ofApplication 6
1.3.5 Effect 7
1.4 Coordinate Systems 7
1.5 ResolutionofaForce intoItsComponents 9
1.6 TrigonometricAnalysis ofForce Systems 11
1.7 Addition ofForceVectors 12
1.8 StaticEquilibrium 14
1.8.1 TwoForces 14
1.8.2 Multiple Forces 14
1.8.3 DeterminationofUnknown Forces 16
AI: ClinicalAnswer 22
2 Moments 23
Q2: ClinicalQuestion:ForcesattheElbowJoint 23
2.1 Moments 24
2.1.1 Moments asVectors 25
2.1.2 Couples 26
xi
