The Human Foot Leslie Klenerman and Bernard Wood The Human Foot A Companion to Clinical Studies With 85 Figures With contribution by:Nicole L. Griffin, MS Hominid Paleobiology Doctoral Program George Washington University Washington DC, USA Leslie Klenerman, MBBCh, ChM, FRCS Bernard Wood, MBBS, PhD, DSc Emeritus Professor of Orthopaedic Henry R. Luce Professor of Human Origins, Center and Accident Surgery, The University of Liverpool, for the Advanced Study of Hominid Paleobiology, Liverpool, UK Department of Anthropology, George Washington University, Washington DC, USA A catalogue record for this book is available from the British Library Library of Congress Control Number: 2005925191 ISBN-10: 1-85233-925-X Printed on acid-free paper ISBN-13: 978-1-85233-925-8 © Springer-Verlag London Limited 2006 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms of licences issued by the Copyright Licensing Agency. Enquiries concerning reproduction outside those terms should be sent to the publishers. The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore free for general use. Product liability: The publisher can give no guarantee for information about drug dosage and application thereof contained in this book. In every individual case the respective user must check its accuracy by consulting other pharmaceutical literature. Printed in the United States of America. (SPI/EB) 9 8 7 6 5 4 3 2 1 Springer Science+Business Media springeronline.com Preface The appendages at the end of our forelimbs tend to attract the evolutionary and clinical limelight, but our feet are as important as our hands for our survival and success as a species. We tend to take them for granted, yet the many millions of modern humans who run either competitively or for recreation, or who play sports such as soccer, tennis, and badminton, or who ride, or dance, or swim, or climb, or who stand and walk as part of their work, all depend on their feet. We submit them to unreasonable loads, and expect them to survive our pounding them on hard pavements. We also add insult to injury by squeezing them into fashionable but uncomfortable footwear which does not conform to the shape of the foot. All this means that many professionals make their living caring for our feet. Worldwide many hundreds of thousands of professional people spend most of their working life looking after the foot. They include orthopaedic surgeons, rheumatologists, diabetologists, orthotists and prosthetists, physical therapists, and podiatrists of whom there are at least 15,000 in the United States of America alone. In the English language there are two classic books about the foot, both by anatomists. In 1935 the American anatomist Dudley Morton wrote the first edi- tion of The Human Foot, and in Great Britain Frederick Wood Jones’ seminal book, Structure and Function as Seen in the Foot, was published in 1944. But since these pioneering efforts great strides have been made in our understand- ing of the evolution and function of the foot. This book is not intended as a replacement for the Morton and Wood Jones monographs, but instead it is designed to provide contemporary users and healers of the foot with some con- text about feet. Neither is it intended to be a clinical textbook. Instead, we hope it will appeal to a wide constituency, including the professionals who care for feet, and to the many categories of `users’, such as long distance runners and soc- cer and tennis players who depend on their feet to take them where they want to be, whether it is the finishing line of a marathon, or a place on a field or a court from where they can kick the winning goal, or play the decisive shot. This book, the combined effort of an orthopaedic surgeon and an anatomist/ palaeoanthropologist, is not intended to be comprehensive but to stimulate readers to go off on their own voyages of discovery. We have subtitled it ACompanion to Clinical Studiesbecause we hope that clinicians will find within its covers information that will deepen their understanding of the function and evolutionary history of this intriguing structure. Writing any book always requires help from others. LK thanks the many friends and former colleagues who provided assistance. These include David Bowsher, Director of Research at the Pain Relief Foundation, Liverpool; Professor Robin Crompton of The University of Liverpool; Professor Adrian Lees of Liverpool John vi Preface Moore’s University; Professor Phillip Tobias at his alma mater, The University of the Witwatersrand, Johannesburg; Susan Barnett, senior research fellow of The University of the West of England and member of the Foot Pressure Interest Group; Peter Seitz of Novel Gmbh, Munich; and Roger Mann, Oakland, California. All were invaluable sources of information and advice. In addition, John Kirkup, a retired orthopaedic surgeon in Bath, was LK’s advisor on history, and Drs. Harish Nirula and Harry Brown of the Artificial Limb Fitting Centre at the Wrexham Maelor Hospital gave generously of their time and expertise to provide informa- tion about amputations and prostheses. Alun Jones and Andrew Biggs of the Photographic Department at the Robert Jones and Agnes Hunt Orthopaedic Hospital, Oswestry were a bastion of support and dealt efficiently with all the illustrations. My secretary Anne Leatham cheerfully coped with the long hours involved in typing draft chapters and references. Last, but not least, I am grateful for the support and constructive criticism which were always available from my wife, Naomi, and from my younger son, Paul. BW is particularly grateful to four of his teachers. Eldred Walls taught him the anatomy of the foot, Michael Day introduced him to palaeoanthropology, Owen Lewis emphasised the importance of rigorous comparative anatomy, and Leslie Klenerman taught him orthopaedics. BW and NG are also especially grateful to Brian Richmond and Elizabeth Strasser who reviewed drafts of Chapter 1; any errors that remain are due to our intransigence. We appreciate help from Phillip Williams and Matt Skinner for generating figures and tables for Chapters 1 and 2. We thank Pilou Bazin for providing translations of articles in French. We are also grateful to the many experts, especially Osbjorn Pearson, Jennifer Clack, Will Harcourt-Smith, and Susan C. Antón, who patiently answered our questions and enquiries, as well as to the authors and publishers who allowed us to include their illustrations in this volume. BW thanks the Henry Luce Foundation for support and NG wishes to acknowledge the support of an NSF IGERT Graduate Studentship Award. Leslie Klenerman, Bernard Wood Contents 1. Early Evolution of the Foot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 From Fins to Feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Foot Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Primate Feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Vertical Clinging and Leaping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Suspension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Quadrupedalism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Bipedalism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Pads, Claws and Nails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Ancient Primates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Miocene Primates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2. Recent Evolution of the Human Foot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Hominin Evolution: An Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Defining Hominins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Organising the Hominin Fossil Record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Evolution of Bipedalism within the Hominin Clade . . . . . . . . . . . . . . . . . . . . . . 34 Scenarios Favouring Selection for Bipedalism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Review of Individual Hominin Fossil Taxa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Primitive Hominins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Archaic Hominins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Megadont Archaic Hominins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Archaic Homo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Anatomically Modern Homo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 3. How the Foot Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 The Subtalar Joint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 The Midtarsal or Transverse Tarsal Joint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 How the Longitudinal Arch Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Flat Feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 Vibrations in the Human Skeleton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 Shock Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 The Importance of the Toes in Walking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 The Sole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 viii Contents Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 4. The Development of Gait . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Prenatal Movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 The Infant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Newborn Stepping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Gait . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Running . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Centre of Gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Changes in the Limbs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 The Foot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Common Variations Which Disappear with Growth . . . . . . . . . . . . . . . . . . . . . 113 Mechanical Work in Walking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Bound Feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 5. The Measurement of Footprints (Pedobarography) . . . . . . . . . . . . . . . . . 117 Force Plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 Pressure Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 Modified Force Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 Laboratory Practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 Loading of the Normal Foot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 Assessment of Foot-pressure Patterns from a Pedobarograph Using Techniques of Imaging Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 The Effect of High and Low Heels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 The Effect of Obesity on Patterns of Foot Pressure . . . . . . . . . . . . . . . . . . . . . . 130 Shear Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 Plantar Pressures in the Great Apes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 6. The Foot in Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 The Armless or the Foot as a Hand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 Footedness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 Running . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 Ballet Dancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 The Foot in Microgravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 Tightrope Walking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 Firewalking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 Kicking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 Swimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 Contents ix 7. Amputations and Prostheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Degree of Loss: Simple to Radical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Amputation of the Great Toe (Hallux) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Amputation of All Toes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 Partial Amputations of the Foot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 Disarticulation at the Ankle (Syme’s Amputation) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 Biomechanics of Midfoot and (Syme’s Amputation) . . . . . . . . . . . . . . . . . . . . . . . . . . 160 Calcanectomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 Prosthetic Feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 Energy Return Feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 Phantom Limb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 1 Early Evolution of the Foot The history of life can be best understood using the analogy of a tree. All living things, be they animals, plants, fungi, bacteria, or viruses are on the outside of the tree, but they are all descended from a common ancestor at its base. The evolu- tionary history of all these living forms is represented by the branches within the tree. Modern humans are at the end of a relatively short twig. There is reliable genetic evidence to suggest that our nearest neighbor on the Tree of Life is the chimpanzee, with another African ape, the gorilla, being the next closest neigh- bour. The combined chimp/human twig is part of a small higher primate branch, which is part of a larger primate branch, which is just a small component of the bough of the Tree of Life that includes all animals (Figure 1.1). This chapter looks into the branches of the Tree of Life to reconstruct the ‘deep’ evolutionary history of modern human feet. Our feet are unique. No other living animal has feet like ours, but as we show in the next chapter some of our extinct ancestors and cousins had feet that were like those of modern humans. What type of animals showed the first signs of appendages that eventually gave rise to primate feet? What can we tell about these distant ancestors and cousins that will help us make sense of the more recent evolutionary history of modern human feet? We trace the emergence of simple, primitive, paired limbs and then examine how selective forces have resulted in the various types of foot structures we see in some of the major groups of living mammals. Our focus then narrows to the early evolutionary history of the Primate order so that in the next chapter we can concentrate on the more recent evolutionary history of the human foot. From Fins to Feet The first animals to develop appendages, the precursors of primitive limbs of land vertebrates, lived in seas, lakes, and rivers. The pioneers of land were called tetrapods and they may have ventured out of water as early as the Upper Devonian period, approximately 370 million years ago (Mya). However, due to the paucity of fossils, palaeontologists have difficulty piecing together why tetrapods developed limbs in the first place and what caused this terrestrial radiation. There is evidence that seeking a home on land did not initially drive the growth of limbs and feet. Acanthostega, an early member of the lineage that includes terrestrial vertebrates, possessed fore- and hindlimbs effective for propulsion in water, but Chapter co-written by Nicole L.Griffin.