Joint Disease in the Horse

C. Wayne McIlwraith, David D Frisbie, Chris Kawcak, René van Weeren

• Publisher: Saunders
• Year: 2015
• ISBN:
  9780323352895
• Edition: 2
• Topic: Medicine
• Subtopic: Equine Veterinary Science

Dr. McIlwraith's Joint Disease in the Horse, 2 nd Edition is the only book to give you a full account of equine joint disease, combining a thorough, up-to-date survey of scientific advances with a practical guide to both medical and surgical treatments. With contributions from nationally and internationally recognized pioneers in the field, this groundbreaking text offers an overview of joint structure and function and translates the latest information on basic joint pathobiology into practical application for the clinician. Step-by-step guidance on injection techniques and medications, along with a survey of practical arthroscopic surgery and developments, make it a truly indispensable reference for all equine veterinarians treating sports and racing horses.

• UNIQUE! Unprecedented, state-of-the-art coverage of the pathology, pathogenesis, and clinical diagnosis of traumatic and degenerative joint disease, so you stay in the know.
• Section on general principles of joint pathobiology provides the background to evaluate and interpret the diagnostic and surgical aspects of disease.
• Explores treatments for traumatic arthritis and osteoarthritis and other joint entities, offering a broad range of options and up-to-date recommendations for problematic decisions.
• Addresses recent advances and results in arthroscopic surgery for the acute injury and results including fragment removal, fragment fixation, and synovectomy.
• Discussion of current research provides insight for difficult cases and calls out the directions in which future arthritis research is headed.
• More than 325 photographs and line drawings help engage and guide you through procedures and treatments.

• NEW! Full color throughout with new artwork and a range of new images including radiographs showing both the normal and the disease progression.
• NEW! Practical step-by-step approach demonstrates the authors' preferred injections methods and shows underlying anatomic correlations.
• NEW and UPDATED! Restructured and substantially revised to emphasize treatment options, making it a practical, concise, and accessible reference and text.
• NEW! All-new chapters on drugs and new biological therapies, including stem cells, IRAP, and PRP and thoroughly updated coverage of HA and corticosteroids.
• NEW! Covers advanced imaging, giving you the latest information available.
• NEW! Expert advice from Dr. McIlwraith, three new co-editors, and new contributors — all distinguished specialists in the field of joint disease in the horse.
• • Lameness and surgical clinicians describe how to approach the various, specific disease conditions.
  • Equine specific radiologists provide their opinions on the best imaging techniques for defining the disease and making interpretations.

Section I

General Principles of Joint Pathobiology

Outline

1. General Anatomy and Physiology of Joints

2. Biomechanics in Joints

3. Traumatic Arthritis and Posttraumatic Osteoarthritis in the Horse

4. Pathologic Manifestations of Joint Disease

5. Osteochondritis Dissecans

6. Subchondral Cystic Lesions

7. Septic Arthritis

8. Effects of Loading/Exercise on Articular Tissues and Developmental Aspects of Joints

1

General Anatomy and Physiology of Joints

P. René van Weeren

The horse has always taken a special position among the species that have been domesticated by humankind. The horse was domesticated rather late, around 3500 BC,¹ millennia after such species as goat, sheep, and cattle. Unlike these other species, the main purpose of the horse’s domestication was not the provision of edible products or products that could be somehow transformed into clothing, such as meat, milk, fur, or skin, but for a less tangible commodity: the combination of physical power and athletic capacity.

Horses have been the major power source for all Eurasian and Northern African civilizations since their introduction from roughly 3500 to 500 BC until the invention of the steam engine that started the Industrial Revolution in the late 1700s. The ultimate personification of the role of the horse in society is perhaps Bucephalus, the legendary horse of Alexander the Great, who conquered the vastest land empire the world has ever known. Bucephalus served Alexander who, according to legend, was the only person able to mount the stallion, from a young age to its death at the age of 30 after the battle of Hydaspes in what is now Pakistan, 2900 miles from its native Macedonia. There, Alexander named the city of Bucephala (present-day Jhelum) after him. After the Industrial Revolution horses still remained essential for many sectors of human society until after World War II, when the combustion engine definitively took over all traditional roles of the horse in warfare, transport, and agriculture. Some have predicted that the loss of its classic duties would make the horse into a zoo species,² but they were proven entirely wrong by the rapidly increasing popularity of the horse as a sports and leisure animal from the mid-1960s onwards. Over the millennia, humans and horses appeared to have bonded in a way that goes far beyond economic value or utility and is more profound than with any other domesticated species, with the exception of the dog. Though admittedly the equine industry is susceptible to the fluctuations of economic prosperity, this fascination for the equine species is not likely to disappear soon, if ever. This obviously guarantees the horse its privileged place in the big family of animal species with which humankind has surrounded itself.

Where the role of the horse in society has changed profoundly in the past century, the underlying reasons of its use and popularity have not changed at all. It is still the stamina of the animal and athletic capacity of its locomotor system that form the basis for almost all present-day use. The most critical body systems for athletic performance are the cardiorespiratory system and the musculoskeletal system. Within the latter system, joints are literally pivotal elements. It may not be surprising that orthopedic malfunctioning or other musculoskeletal disorders account for the vast majority of reasons to consult an equine vet.³ Of the specific elements of the musculoskeletal system, joint disorders invariably rank first or second in importance (together with tendinopathies, depending on discipline). Most figures come from the racing industry,^4,5 but the relatively scarce data for sport horses also point in the same direction.^6,7 In a survey of U.S. horse owners in 1998 it was estimated that 60% of all lameness was related to osteoarthritis (OA) and approximately $145 million was spent on veterinary bills relating to the problem.⁸ In this respect, the clinical importance of joint disorders in the equine species is very comparable to the situation in humans where musculoskeletal disorders in general and articular pathologies in particular represent an enormous burden to society in terms of loss of quality of life and costs of healthcare with 151 million sufferers of OA worldwide.⁹ For this and a number of important biologic reasons the horse is increasingly recognized as a suitable, if not the best, model for human joint disease.¹⁰ This translational aspect of equine joint disease will be dealt with in more detail in Chapter 27, which discusses arthritis research and future directions in joint disease.

This first chapter gives a general introduction into the anatomy and physiology of the (equine) joint, as a basis for the understanding of the following chapters that address in detail specific disorders, diagnostic possibilities, and therapeutic interventions.

Joint Functions

Whereas the necessary stability of the equine musculoskeletal system is provided by the rigid bony components, joints permit motion of these bony components in relation to each other and, indirectly, the displacement of the entire individual with respect to the environment, that is, locomotion. To accomplish this, joints have to meet several requirements. They have to be as robust as the bony elements of the musculoskeletal system, as the forces generated by locomotion and other (athletic) activities are transmitted through joints as they are through bones. They also have to allow for smooth and as frictionless as possible motion of the bony ends that articulate with respect to each other. Lastly, they have a role, together with other structures, such as the digital cushion in the foot, to mitigate and dampen the accelerations and associated vibrations that are generated during the impact peak of the stride cycle at hoof landing. This latter aspect has been relatively well studied in the equine literature.^11,12

All the aforementioned requirements that are at least partially contradictory (strength comparable to bone, smooth surfaces for supple gliding, and resilience for shock absorption) have to be accommodated in a single structure, which is a challenging task. As will be explained, nature deals with these challenges in an ingenious way, however, at the cost of flexibility and repair capacity. For reasons of clarity the components that make up a joint will be dealt with separately, but it is important to stress that a joint is more than a collection of tissues with separate characteristics and functions. There is common agreement nowadays that the joint should be seen as a complex multicomposite organ not unlike structures such as the liver, kidney or heart.^13,14 Within this organ the constituting elements act together to ensure proper joint function. There is a strong interplay of all these components in health and disease and mutual influencing of physiologic functioning; malfunctioning of the components will also inevitably affect the other constituents and hence performance of the entire joint at a shorter or longer term.

Types of Joints

Joints can be classified in several ways. A gross division can be made between classification according to structural characteristics, that is, the type of tissue(s) that form the interface between the articulating bony parts of the skeleton, and classification according to function, or the degree and type of movement joints allow.

The currently used basic classification is three major categories, which are fibrous joints with the bone connected by dense connective tissue, cartilaginous joints where cartilage is the interface, and synovial joints in which there is a fluid-filled cavity.¹⁵ In the horse, the articulations between the bodies of the vertebrae that make up the axial skeleton are fibrous joints, with the exception of the articulation between the first and second cervical vertebrae (C1-C2), which is a synovial joint. A cartilaginous joint has an interface consisting of hyaline or fibrous cartilage; examples are the human intervertebral disk and the symphysis of the pubic bones in both humans and horses. In synovial joints there is no structural connection between the bony parts of the skeleton, but both ends are capped with hyaline cartilage and articulate by gliding over each other although contained in a joint capsule that is filled with synovial fluid, a viscous liquid. A sliding bearing in mechanical engineering basically functions according to the same principle.

In a functional sense, there are several other ways to classify joints. A common way is according to the degree of motion they permit. Although the following nomenclature is currently seen as obsolete,¹⁵ it is still widely used and will hence be mentioned here. A synarthrosis is a joint permitting little mobility. Most of these joints are of fibrous nature, such as the sutures that connect the bony components that make up the skull. Amphiarthroses are joints that permit more, but still very limited, mobility. They are generally of either fibrous or cartilaginous nature, with the intervertebral joints (again with the exception of C1-C2) as the best examples. Finally, diarthrodial joints permit maximal motion. These are always synovial joints and their motion is limited by periarticular or intraarticular structures such as capsules or ligaments, but not by the nature of the joint. Virtually all joints of the appendicular skeleton of the horse are diarthrodial joints.

Other functional classifications are based on the degrees of freedom a joint has. Any three-dimensional body in space has six potential degrees of freedom within the global coordinate sy...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Contributors
• Preface to the First Edition
• Preface to the Second Edition
• Section I. General Principles of Joint Pathobiology
• Section II. General Principles of Diagnosis and Treatment
• Section III. Principles of Therapy of Traumatic Arthritis and Osteoarthritis
• Section IV. Specifics of Anatomy, Clinical Diagnosis, Imaging Diagnosis, and Treatment by Region
• Section V. New Frontiers
• Index