Biomechanics of Tendons and Ligaments

Tissue Reconstruction and Regeneration

Johanna Buschmann, Gabriella Meier Bürgisser

• Publisher: Woodhead Publishing
• Year: 2017
• Print ISBN: 9780081004890
• eBook ISBN: 9780081004920
• Topic: Technology & Engineering
• Subtopic: Biotechnology in Medicine
• Index: Technology & Engineering

Biomechanics of Tendons and Ligaments: Tissue Reconstruction looks at the structure and function of tendons and ligaments. Biological and synthetic biomaterials for their reconstruction and regeneration are reviewed, and their biomechanical performance is discussed.Regeneration tendons and ligaments are soft connective tissues which are essential for the biomechanical function of the skeletal system. These tissues are often prone to injuries which can range from repetition and overuse, to tears and ruptures. Understanding the biomechanical properties of ligaments and tendons is essential for their repair and regeneration.- Contains systematic coverage on how both healthy and injured tendons and ligaments work- Includes coverage of repair and regeneration strategies for tendons and ligaments- Presents an Interdisciplinary analysis on the topic

Part One

Fundamentals and biomechanics of tendons and ligaments

1

Structure and function of tendon and ligament tissues

Abstract

Tendons and ligaments are connective tissues that serve as the force transmitting entities and enable musculoskeletal motion. Typical features of normal tendon tissue are parallel-aligned collagen I fibers and tenocytes. Moreover, the extracellular matrix (ECM) is composed of proteoglycans, glycoproteins, and elastin. The tissue has almost no vessels and the nutrition as well as oxygen are supplied at the vascularized myotendinous and osteotendinous junctions. Growth factors such as transforming growth factor beta are important for tendon development, homeostasis, and regeneration. Structural changes upon aging and tendinopathy include the extent of vascularization (aging causes less tendinopathy and more vascularization), the ECM (age-related lower collagen content and in tendinopathy collagen disorganization), and the proteoglycan content (older tendons having less, tendinopathic tendons more proteoglycans), which will be addressed in detail in this chapter.

Keywords

Tendon cells; Collagen; Extracellular matrix; Elastin; Growth factors

Abbreviations

ACL anterior cruciate ligament (tendons and ligaments)

ADAM a disintegrin and metalloproteinase (enzyme in living cells)

ADAMTS a disintegrin and metalloproteinase with thromospondin motifs (enzyme in living cells)

AGEs advanced glycation end products (substances in degenerative diseases)

AT Achilles tendon (tendons and ligaments)

C calcaneus (elements of the foot ankle)

CD34 hematopoietic progenitor cell antigen (antigen protein)

CDET common digital extensor tendon (tendon and ligaments)

COMP collagen oligomeric matrix protein (protein in soft tissues)

COX2 cyclo-oxigenase2 (enzyme in living cells)

CT connective tissue (elements of the body)

CTGF connective tissue growth factor (protein in living cells)

ECM extra cellular matrix (matrix in living cells)

EH extensor hood (elements of the body)

ET extensor tendons (tendons and ligaments)

FACIT fibril-associated collagen with interrupted triple-helix (protein in soft tissues)

FDL flexor digitorum longus (tendon and ligaments)

FDP flexor digitorum profundus (tendons and ligaments)

FDS flexor digitorum superficialis (tendon and ligaments)

FHL flexor hallucis longus (tendons and ligaments)

FR flexor retinaculum (tendons and ligaments)

FT flexor tendons (tendons and ligaments)

FT (also FDP) flexor digitorum profundus tendon (tendons and ligaments)

GAGs glycosaminoglycans (called also mucopolysaccharide) (polysaccharides in living cells)

GDF (-n) growth/differentiation factor n (protein in living cells)

HGF hepatocyte growth factor (protein in living cells)

IFM interfascicular matrix (called also endotenon) (element in tendons and ligaments)

IGF (-n) insulin-like growth factor n (protein in living cells)

IPJ interphalangeal joints (elements of the foot)

JT juncturae tendinum (elements of the body)

KP Kager's fat pad (also known as the precalcaneal fat pad or pre-Achilles fat pad) (fat pad in the food ankle)

L lumbricals: intrinsic muscles of the hand (also present in the foot) (elements of the body)

MRI magnetic resonance imaging (imaging technique)

mRNA messenger ribonucleic acid (element of living cells)

MSC mesenchymal stem cell (element of the body)

MTJ metatarsophalangeal joint (elements of the foot)

nm nano meter (measure of length)

NMDAR1 N-methyl-d-aspartate receptor (receptor protein)

PDGF platelet-derived growth factor (protein in living cells)

PDGF-R platelet-derived growth factor receptors (receptor for growth factor)

PLCL poly(l-lactide-co-ɛ-caprolactone) (synthetic polymer for tissue engineering)

ROCK rho-associated protein kinase (enzyme in living cells)

Scx scleraxis (transcription factor protein)

SDFTs superficial digital flexor tendons (tendon and ligaments)

SLCs synovial lining cells (cell type of the body)

SLRP small leucine rich proteoglycans (glycosylated proteins in living cells)

ST superior tuberosity (part of the calcaneus)

TGF (-βn) transforming growth factor beta n (protein in living cells)

TIMPs tissue inhibitors of metalloproteinase (enzyme in living cells)

US ultrasound/ultrasonography (imaging technique)

VEGF vascular endothelial growth factor (protein in living cells)

1.1 Introduction

The main function of tendons and ligaments is to transfer force from muscle to bone (in tendons) or from bone to bone (in ligaments) in order to provoke motion. In the hand and foot, tendon networks occur associated by the links between each other; the concept of “supertendons” was proposed to describe the fact that such networks exhibit a functional range exceeding that of its individual members (Benjamin, 2010).

In this chapter, tendon and ligament structures and functions are presented for three states: the normal healthy state, the aging state, and the tendino-pathological state. Nourissat et al. (2013) have nicely put the main structural features of these three states together (Fig. 1.1). As such, the main differences are found in terms of collagen fiber organization and morphology, vascularization, and cell density as well as cell morphology. Moreover, also the proteins in the extracellular matrix (ECM) do change from normal to aging and degenerative state of tendon and ligament tissue.

Fig. 1.1 Structural changes of tendons from normal (A) through aging (B) and chronic tendinopathy (C). Normal tendon is a well-organized network of collagen fibrils. Collagen is arranged in hierarchical levels of increasing complexity, beginning with tropocollagen, a triple-helix polypeptide chain, which unites into fibrils, fibers (primary bundles), fascicles (secondary bundles), tertiary bundles, and the tendon itself. The extra cellular matrix (ECM) is dense, with a fibrillar network of predominantly parallel-aligned collagen fibers, principally consisting of 95% type I collagen. In addition, the ECM is composed of proteoglycans, glycosaminoglycans, and glycoproteins. The synthesis of the tendon ECM is under the control of two main growth factors: TGF-β (transforming growth factor beta) and FGF (fibroblast growth factor). Blood supply is necessary for nutrition and healing of the tendon and come from two places. The first source of blood supply is the extremity of the tendon; the second source is the periphera...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Part One: Fundamentals and biomechanics of tendons and ligaments
• Part Two: Repair and regeneration of tendons and ligaments
• Index