Fascial Anatomy of the Equine Forelimb

Carla M. Lusi, Helen M.S. Davies

• Publisher: CRC Press
• Year: 2018
• eBook ISBN: 9781351172905
• Edition: 1
• Topic: Medicine
• Subtopic: Equine Veterinary Science

Lusi and Davies have provided an excellent reference resource for students and graduates alike. The number of well-defined, relevant and clear images allow quick understanding for anyone interested in the fascial anatomy of the horse. This small book is perfect to have in your bag, allowing the student or clinician to find all the information they need on-site. - Sophie Neasham, final year veterinary student, University of Veterinary Medicine in Kosice, Slovakia

Key features:

• The first book in equine anatomy to illustrate the fascial (soft connective tissue) connections of the equine forelimb.
  
  

• Clear, high-quality images (with reference images included on each page) help readers identify aspects of the limb photographed.
  
  

• A brief introduction to the forelimb musculoskeletal anatomy (with images) helps readers familiarize themselves with muscles and bones portrayed in photographs.
  
  

• Focused discussions highlight the practical applicability of the fascial connections illustrated.
  
  

• Accompanying video clips demonstrate connectivity of the fascial system particular lines of tension.
  
  

The first of its kind in equine anatomy, this clear, concise anatomical guide illustrates the fascial (soft connective tissue) connections of the equine forelimb. Based on dissections of fresh equine cadaver limbs, it provides a visual map for equine physical therapists, veterinarians and horse riders, helping them to understand how pathologies, injuries, or movement abnormalities of the equine forelimb arise and/or progress from one area of the limb to another.

The fascial system is one of the primary systems acted upon by equine physiotherapists and is of increasing interest to horse riders looking to achieve structural integration and balanced movement in their horse. With this in mind, key points in each chapter highlight everyday situations in which knowledge of the fascial system may assist in understanding horse movement and injury.

This practically applicable anatomical atlas is the ideal reference for horse owners, body workers and veterinarians alike.

CHAPTER 1

UNDERSTANDING THE FASCIAL SYSTEM

INTRODUCTION

In trying to determine ways in which load distribution and postural stability of the fetlock joint is managed, the recent interest around the function and importance of fascia is of particular relevance. Although it is considered to have several mechanical and physiological roles, the clinical importance of the fascia as a system comes down to how it integrates all systems of the body and how this understanding can be used to direct treatment, rehabilitation, and exercise in order to prevent injury or catastrophic breakdown of an individual musculoskeletal element.

The identification of fascial lines in humans has not provided solutions to all musculoskeletal injuries; however, it has provided a visual map which has helped practitioners to see the relatedness of structures and the development of compensatory postural adjustments or pain that result from dysfunction in otherwise unsuspected areas of the body. Hence, it brings attention to the fact that improper loading of the joint, or an inability of the joint to effectively manage loads, may be related to a restriction or locomotor abnormality somewhere else in the body.

In horses, investigation of the body-wide fascial connections and meridians is a large undertaking as there is a very limited amount of literature available that is directed at the equine fascial system (described further in the following). However, identifying paths of fascial continuity in individual body segments (such as the forelimb) may provide a foundation upon which further studies looking at fascial continuity can be based.

WHAT IS FASCIA?

Composition and structure

The fascial system refers to a body-wide connective tissue matrix, which provides structural support to all bodily tissues and organs, as well as communicating pathways within and between these structures. In investigating the structure and composition of fascia, there are three components to be considered. These include its cellular anatomy, the fibres it comprises, and its extracellular matrix.

The cellular component of fascia consists of fibroblasts, adipocytes, macrophages, mast cells, undifferentiated mesenchymal cells, plasma cells and leukocytes. The most abundant of these cells are the fibroblasts, which are under endocrine control and are responsible for the synthesis of complex carbohydrates, collagen and elastic fibres, as well as other proteins of the extracellular matrix.

It has been shown that strain and pressure applied to fascia stimulates the proliferation of fibroblasts and causes them to orientate along the same stress lines as the direction of applied force (Gehlsen, Ganion, & Helfst, 1991). This process is mediated by changes in the internal cytoskeletal structure, which similarly respond to the tensional forces applied to them. Hence, it is implied that mechanical stresses placed on the body influence the overall composition and structure of the fascia, causing it to adapt via an increased production of fibroblasts and rearrangement of the internal cytoskeletal structure.

The fibrillar component of fascia includes two main fibre types: collagen and elastin. Generally, collagen fibres are flexible in an unloaded state but become stiff and strong when subject to tension. This tension and resulting strength is provided by covalent cross links between collagen molecules, which develop and arrange according to the direction and magnitude of mechanical loads applied to them (Hukins & Aspden, 1985; Stecco, 2015). The alignment of the collagen fibre itself is usually along lines of tensile stress and hence can be indicative of loading patterns and function.

In contrast, elastic fibres are comprised of two different structural components including elastin and microfibrils. Elastic fibres differ in function to collagen fibres in that they provide tissues with the required resilience to transient stretch. They have the ability to be stretched up to 150% of their original length in response to applied force and recoil to their original length when force is removed. Long collagen fibres, which can only stretch <10% of their resting length prior to tearing, are usually interwoven with elastic fibres to prevent overstretching and rupture.

The last component of the fascial system is the extracellular matrix. This functions to distribute mechanical stresses and provide a structural framework for the adherence and movement of cells and comprises both elastic and collagen fibres, as well as ground substance. The ground substance refers to an amorphous gel-like substance surrounding the cellular and fibrillar components of fascia and which functions to provide support and nutrition to all cells. Its water content, and thus viscosity, determines the overall mobility and connectivity of the connective tissue matrix and allows for movement of adjacent fibres with limited friction. Proteoglycans, hyaluronic acid and link proteins are the primary constituents of the ground substance.

Identifying fascia

The organisation of fascia, its expansive connectivity and its varying physical characteristics (thickness, composition etc.) introduces a lot of area for debate and confusion when it comes to distinguishing and describing its anatomy and function. Generally, it is accepted that the fascia of the human body can be categorised into the fascia superficialis (superficial fascia) and the fascia profunda (deep fascia). This nomenclature remains consistent in regards to the equine fascial system.

Both types of fascia are made up of the same constituents described earlier; however, their relative proportions differ greatly. The superficial fascia exists as a layer of loose areolar connective tissue situated beneath the dermis of the skin, which varies in thickness and composition along different locations depending on its functional role. Fibrous septa, which connect the superficial fascia to both the overlying skin and the underlying deep fascia, allows the superficial fascia a role in maintaining the integrity of the skin and in supporting subcutaneous structures.

The superficial fascia is comprised of interwoven collagen fibres, loosely packed and mixed with an abundance of elastic fibres. These elastic fibres allow for displacement between the superficial fascia layer and neighbouring tissue layers, thereby allowing sliding between tissue planes with movement and muscular activity. In some regions, the superficial fascia further acts as a subdividing tissue plane, which forms compartments around major subcutaneous vessels.

In contrast the deep fascia refers to fibrous fascial sheets, which not only envelop and separate muscles, but also forms sheaths around vessels and nerves and provides a means of strengthening ligaments around joints. Essentially, the deep fascia binds all structures together.

Two types of deep fascia have been described including the aponeurotic deep fascia and the epimysial deep fascia. The aponeurotic fascia refers to all the ‘well-defined fibrous sheaths that cover and keep in place a group of muscles or serve for the insertion of a broad muscle.’ It remains separated from underlying muscles and is capable of transmitting forces over a long distance due to its thickness (590–1453 μm) and well-defined fibre orientation. According to its position and function, it may adhere to, or become continuous with, the periosteum of bones, the paratenon of tendons and ligaments, or the connective tissue comprising joint capsules. Such examples in humans include the thoracolumbar fascia and the investing fascia compartmentalising the muscles of the limbs.

The epimysial fascia refers to the thinner, yet still well organised, deep fascia, which is strongly connected to muscles and allows them to slide against overlying tissue planes. In contrast to the aponeurotic fascia, it is specific to each muscle, providing a medium for insertion of muscle fibres and giving off fibrous septa that penetrate the muscle. Hence, it transmits forces generated by single muscle fibres and has a more localised range of action.

PAST INVESTIGATIONS OF THE EQUINE FASCIAL SYSTEM

There has been very little research published concerning the functional anatomy of the equine fascial system and how it may be targeted to improve and optimise movement and performance. In fact most veterinary anatomy textbooks present the musculoskeletal system as one that is comprised of anatomically and functionally distinct units (either skeletal or muscular), often completely ignoring the integrative role of fascia. As a result, information on the equine fascial system is inconsistent, incomplete or difficult to access (see reference list at end of chapter).

The benefits of recognising the fascial system in human movement and performance suggests that the equine fascial system provides an area for research with lots of potential for improving equine performance and managing and preventing injury. The main aim of this book is to encourage thinking about related movements (which are enabled via the fascial system) and how movement restrictions or abnormalities in one area of the body may result in load redistribution and the consequent potential for pathological change in another area of the body.

Investigating the entire equine fascial system is a large undertaking, and hence this book focuses solely on an area of the body that has a significant role in load bearing and is particularly vulnerable to overuse injuries and catastrophic breakdowns- that is, the forelimb. Although the primary focus of this book is the fascial connectivity in the forelimb, the significance of this cannot be grasped without a solid understanding of the already-described musculoskeletal elements of the forelimb. Hence, before diving into the fascial anatomy, a brief summary of the forelimb skeleton and muscles is presented. It is hoped that, together with this existing knowledge, the fascial anatomy presented in this book will help to further the current understanding of overall forelimb biomechanics and the development of compensatory postures and movement patterns which may occur with limb lameness and injury.

REFERENCES

Gehlsen, G., Ganion, L., & Helfst, R. (1991). Fibroblast responses to variation in soft tissue mobilization pressure. Medicine and Science in Sports and Exercise, 31, 531–535.

Hukins, D., & Aspden, R. (1985). Composition and properties of connective tissues. Trends in Biochemical Sciences, 10(7), 260–264.

Stecco, C. (2015). Functional Atlas of the Human Fascial System. Edinburgh: Elsevier.

BIBLIOGRAPHY

Alberts, B., Johnson, A., & Lewis, J. (2002). Molecular Biology of the Cell (4th ed.). New York, NY: Garland Science.

Barone, R. (2010). Arthrologie et Myologie (4th ed., Vol. 2). Paris: Éditions Vigot.

Baxter, G. (2011). Adams and Stashak’s Lameness in Horses ( G. Baxter, Ed., 6th ed., Revised ed.). Chichester: John Wiley & Sons.

Blasi, M., Blasi, J., Miguel-Pérez, M., Domingo, T., Dorca, E., García, M., & Pérez, A. (2012). Anatomical and histological study of fetus fascias. Journal of Bodywork and Movement Therapies, 16(4), 523.

Bradley, O. (1920). The Topographical Anatomy of the Limbs of the Horse. Edinburgh: W. Green & Son.

Caggiati, A. (2000). Fascial relations and structure of the tributaries of the saphenous veins. Surgical and Radiologic Anatomy, 22, 191–196.

Chauveau, A. (1873). The Comparative Anatomy of the Domesticated Animals ( G. Fleming, Ed., 2nd ed.). New York, NY: D. Appleton and Company.

Chila, A. (2010). Foundations of Osteopathic Medicine (Revised ed.). Philadelphia, PA: Lippincott Williams & Wilkins.

DiGiovanna, E., Schiowitz, S., & Dowling, D. (2004). An Osteopathic Approach to Diagnosis and Treatment (Revised ed.). Philadelphia, PA: Lippincott Williams & Wilkins.

Egerbacher, M., Forstenpointer, G., Weissengruber, G., Licka, T., & Peham, C. (2012). Passive load-relevant structures of the musculoskeletal system in the forelimb of the horse. Journal of Bodywork and Movement Therapies, 16(3), 404–405.

Eichbaum, F. (1883). Fascien des Pferdes. Archiv für die wissenschaftliche und praktische Tierheilkunde 14, 280–308.

Gersh, I., & Catchpole, H. (1960). The nature of ground substance of connective tissue. Perspectives in Biology and Medicine, 3(2), 282–319.

International Committee on Veterinary Gross Anatomical Nomenclature. (2012). Nomina Anatomica Veterinaria. Hannover: Editorial Committee.

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Lindsay, M., & Robertson, C. (2008). Fascia: Clinical Applications for Health and Human Performance. New York, NY: Delmar Cengage Learning.

Myers, T. (2009). Anatomy Trains: Myofascial Meridians for Manual and Movement Therapists (2nd ed.). New York, NY: Elsevier.

Nickel, R., Schummer, A., Seiferle, E., Wilkens, H., Wille, K.-H., & Frewein, J. (1986). The Anatomy of the Domestic Mammals (Vol. 1). Berlin: Verlag Paul Parey.

Paulli, S., & Sörensen, E. (1930). Die Fascien des Pferdes. Kopenhagen, Dänemark: Königl Tierärytliche und Landwirtschaftliche Hochschule.

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Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Authors
• CHAPTER 1 UNDERSTANDING THE FASCIAL SYSTEM
• CHAPTER 2 ANATOMY OF THE EQUINE FORELIMB
• CHAPTER 3 FASCIA OF THE EQUINE METACARPUS AND PROXIMAL PORTION OF THE DIGIT
• CHAPTER 4 FASCIA OF THE EQUINE ANTEBRACHIUM
• CHAPTER 5 FASCIA OF THE EQUINE SHOULDER GIRDLE AND BRACHIUM
• CHAPTER 6 FASCIAL LINES EXTENDING INTO THE HOOF
• CHAPTER 7 FASCIAL LINES OF TENSION IN THE EQUINE FORELIMB
• Index