Malik Shahbaz S - Orthopaedic biomechanics made easy

To our parents Muhammad S. Malik and Shahnaz Akhtar for their prayers and blessings, and showing us the value of education whether being taught or teaching others, and to our brother, Shahzad S. Malik, for being there for us.

This type of surgery demands training in mechanical techniques, which, though elementary in practical engineering, are as yet unknown in the training of a surgeon.

Orthopaedic Biomechanics Made Easy introduces you to the fundamental biomechanical principles in orthopaedics, and shows you how these relate to the clinical practice. The book seeks to fulfil two objectives:

• To bring together important biomechanical concepts relevant to surgical practice.
• To make these ideas simple and easy to learn.

Our efforts have been about taking you back to the first principles, and making them more interesting and fun to learn. We have avoided point-by-point references for this reason, as we feel that this might affect the reading experience.

To help you explore the subject, the book is signposted into three parts: Orthopaedic biomaterials and their properties; Engineering theory applied to orthopaedics; and, Clinical biomechanics. Each concept is introduced and explained in a discrete double-page spread. Consecutive sections are usually related and follow a common theme. Naturally, some ideas are more difficult than others, and we expect you to skip over them initially and to come back to them after covering the simpler topics. You do not need to deal with advanced maths to understand the presented biomechanical principles. Mathematical explanations are provided in some sections only to demonstrate how a particular biomechanical fact is derived. You may skip over the mathematical workings without missing out on the learning points.

We hope this book helps to make your clinical practice easier and more rewarding.

We are grateful to Miss Caroline Hing at St Georges Healthcare NHS Trust for advice and help in setting up this project. We are in debt to two groups of teachers: the faculty at Cardiff School of Engineering, Cardiff University, where we read MSc in Orthopaedic Engineering, and our clinical trainers for sharing their experience and wisdom. Thanks also to our colleagues at the Engineering School and various hospitals for the group discussions that helped to clarify and develop ideas.

Part I Orthopaedic biomaterials and their properties

Just as there are three states of matter: solid, liquid and gas, there are three basic forms of solid materials: metals, ceramics and polymers. A composite is formed when any of the types of materials combine in an insoluble state. This radiograph shows all four types of solid material in function in a total hip replacement. The internal structure of the materials produces their unique physical properties, which are utilised in designing orthopaedic implants.