Ligaments And Tendons

Question 0

What do tendons connect?

Answer 0

Muscle to bone

Question 1

What do ligaments connect?

Answer 1

Bone to bone

Question 2

What are ligaments function?

Answer 2

*Augment STATIC MECHANICAL STABILITY OF JOINTS
*PREVENTS XS ABNORMAL MOTION
SENSORY SOURCE, PROVE PROPRIOCEPTION FEEDBACK

Question 3

What is the function of tendons?

Answer 3

TRANSMIT TENSILE LOAD TO BONE
ENABLE MUSCLE TO BE OPTIMAL DISTANCE FROM JOINT
STORE ENERGY

Question 4

What are ligaments and tendon made of?

Answer 4

PARATENON- loose areolar tissue, protects and facilitates gliding. Major site of remodelling and healing responses- abundant cells and blood vessels (vascular tendons ) some tendons a synovial sheath replaces the paratenon - AVASCULAR tendons
EPITENON- a SYNOVIUM like membrane beneath paratenon for tendons with high frictional forces in Palm - increase gliding, by producing SYNOVIUM form synovial cells
ENDOTENON- binds fascicles ( groups of collagen bundles )

MICRO=
Cells-FIBROBLASTS
Extracellular matrix-
     COLLAGEN 1( 70% tendons )
     GROUND GLASS
      ELASTINS ( > LIGAMENTS)

Question 5

How is collagen synthesised?

Answer 5

As a PRECURSOR, PRO-COLLAGEN by FIBROBLASTS

SECRETED and CLEAVED extracellularly-> COLLAGEN

Question 6

What type of collagen is within ligaments and tendons?

Answer 6

Type 1- 90%

Question 7

How does collagen exist?

Answer 7

As 3 POLYPEPTIDE CHAINS
2 alpha 1
1 alpha 2
COMBINED TO FORM A RIGHT HANDED TRIPLE HELIX-> collagen molecule a ROD like shape

Question 8

What are the x linkage between collagen molecules due to ?

Answer 8

Hydrogen bonds

Question 9

What do several collagen fibres aggregate to form?

Answer 9

MICROFIBRILS (0.02-2um) in a quarter staggered way

Question 10

What are further aggregation of MICROFIBRILS called?

Answer 10

Collagen fibres (1-20um) and bundles

Question 11

What are lined between these bundles?

Answer 11

Fibroblasts in the direction of the ligament/ tendon function

Question 12

What is the direction of collagen fibres in tendons? Why is this?

Answer 12

Parallel

To allow them to handle UNIDIRECTIONAL TENSILE LOADS

Question 13

What direction are the collagen fibres in ligaments? Why is this?

Answer 13

Less parallel in layered arrangement with a single layer of fibres lying parallel but in subsequent layers they lie at different directions.
Also crimped ( wavy pattern) to increase their capacity to absorb tension

To allow these structures to SUSTAIN PREDOMINANTLY TENSILE STRESSES IN 1 DIRECTION but also SMALLER STRESSES IN OTHER DIRECTION for any applied external force

Question 14

What does the ground substance consist of? Can you draw it?

Answer 14

PROTEOGLYCANS
GLYCOPOROTEINS
PLASMA PROTEINS

Question 15

What is the role of the PROTEOGLYCANS ?

Answer 15

That bind Extracellular water making the matrix a highly structured gel like material.
It also STABLISES the collagenous skeleton of the ligaments and tendons and contributes to overall strength

Question 16

What is ELASTIN?

Answer 16

A HYDROPHOBIC NON GLYCOSLATED PROTEIN secreted by FIBROBLASTS into the Extracellular matrix

Question 17

What does elastin do in ligaments and tendons ?

Answer 17

These hydrophobic nonglycosylated proteins form an extensive network with HIGHLY CROSS LINKED FILAMENTS and SHEETS which allow the network to STRETCH AND COIL
Up to 200%. Of the unloaded length at relatively low loads

Question 18

What is the importance of elastin in tendons and ligaments ?

Answer 18

In the RECOVERY OF tissue after loading

Their function diminished towards max loading levels because their max strength is about 5x lower than collagen

Question 19

Which does elastin have a greater content in tendons or ligaments ?

Answer 19

Ligaments

Question 20

What are tendons and ligaments highly resistant too?

Answer 20

LENGTHENING

tendons also relatively FLEXIBLE and can angulated around bone surfaces/ deflect beneath retinacula total the direction

Question 21

Are tendons stronger than ligaments? If so why?

Answer 21

Yes ligaments are weaker than tendons Due to the organization of fibres in layer not all fibres are stretched when loaded along the main fibre axis. Therefore weaker than tendons

Question 22

Describe the structure of the insertion points for ligaments and tendons?

Answer 22

Divided into 4 ZONES ;
Zone 1- Parallel collagen fibres at end of the tendon/ligament
Zone 2- Collagen fibres INTERMESH with UNMINERALISED FIBROCARTILAGE
Zone 3- FIBROCARTILAGE GRADUALLY becomes MINERALISED
Zone 4-MINERALISED FIBROCARTILAGE MERGES into CORTICAL BONE

Question 23

What crosses all 4 zones?

Answer 23

The perforating fibres of SHARPEY- connective tissue which strengthens the bony attachment

Question 24

What's the importance of the zones 1-4?

Answer 24

The change in structure properties -> INCREASED STIFFNESS | DECREASE STRESS CONCN-> reduces injuries at INSERTION SITE

Question 25

What additional structure do tendon have to aid strength?

Answer 25

APONEUROSIS - within the muscle fascia. | -> LARGER SURFACE AREA for LOAD TRANSFER from muscle to tendon! with the orientation increasing the strength.

Question 26

Describe blood supply to tendon / ligaments ?

Answer 26

Poor vascular supply cf bone/ skin They have a lower metabolic rate Mainly found at INSERTION SITES runs LONGITUDINALLY and is UNIFORM

Question 27

What is the blood supply in the paratenon?

Answer 27

Thru a SPARSE array of SMALL ARTERIOLES which run longitudinally fro adjacent muscles to arerolar connective tissue

Question 28

What is the blood supply in AVASCULAR tendons ? | Why is this CLINCALLY important?

Answer 28

A VINCULA - MESOTENON - carries a vessel to supply ONE TENDON SEGMENT - adjacent areas receive nutrition via diffusion So PARATENON covered TENDONS HEAL BETTER than other Tendons

Question 29

What is the nerve supply to tendons/ligaments ?

Answer 29

Mainly via AFERENT , with specialised afferent receptors. when these special receptors are activated during rapid increase in tension , myostatic reflexes are activated which inhibit development of excessive tension during muscular contraction. Hence importance in proprioception role in overal neuromuscular control of the limb

Question 30

What are the properties of ligament and tendons?

Answer 30

They are VISCOELASTIC - low loads viscous, high loads elastic= Demonstrate stress-strain behaviour which is time and rate dependent - CREEP STRESS RELAXATION HYSTERESIS STRESS/ strain rate

Question 31

What factors affect the biomechanical properties of ligaments / tendons?

Answer 31

AGEING EFFECT- up to 20 yrs the no and quality of x linking increases -> increase tensile strength tendons and ligaments >20 yrs- MEAN COLLAGEN DIAMETER/CONTENT DECREASE-> gradual DECLINE in MECHANICAL PROPERTIES < puberty - weakest link ligament bone complex cf adult = mid substance failure ENDOCRINE- INCREASE LAXITY /reduced stiffness in later stages of pregnancy. PHARMACOLOGY- short term use of INDOMETHCAIN- increase tensile strength of tendons ? ^ of collagen x linkage Corticosteriods - reduced biomechanical qualities MOBILISATION/immobilisation

Question 32

What are the 2 main types of injury?

Answer 32

REPETITIVE MICROTRAUMA | MACROTRAUMA

Question 33

Describe what happens in Repetitive microtrauma ?

Answer 33

FATIGUE FAILURE occurs due to Repetitive Loading well below the normal ULTIMATE TENSILE STRENGTH -> MICROTEARS followed by an INFLAMMATORY REACTION ( in an attempt to heal) + Sometime CALCIFICATION -which alters the biomechanical properties Often occurs in tendon since they carry higher loads invivo

Question 34

Described how macro-trauma causes injury in tendons/ ligaments ?

Answer 34

ACUTE FAILURE due to FORCES above the ULTIMATE TENSILE STRENGTH-> PARTIAL/ COMPLETE RUPTURE normally gd mechanism of injury

Question 35

At a low loading rate where is the weakest part of the tendon/ligament ?

Answer 35

BONY INSERTION

Question 36

What is the weakest points in a tendon/ligament when a high load is applied?

Answer 36

The tendon / ligament | Suggests at a higher strain rate the strongest part is the bone/ligament complex

Question 37

Where do the ligament avulsion occur?

Answer 37

Between zones 2/3- between UNMINERALISED and MINERALISED FIBROCARTILAGE LAYERS

Question 38

In tendons what other 2 factors contribute to injury?

Answer 38

1) CROSS SECTIONAL AREA OF THE TENDON cf ITS MUSCLE- strength of tendon/ muscle depends on x sa- the larger xsa of muscle the stronger the force produced by the contraction and greater the tensile loads transmitted thru the tendon. Same larger xsa of tendon the greater the load it can bear. If tendons greater xsa cfmuscke likely the muscle with rupture. 2) . AMOUNT of FORCE PRODUCED BY CONTRACTION of the MUSCLE to which the TENDON IS ATTACHED- when muscle max contracted, the tensile stress on tendon is highest. This stress can be increased if ECCENTRIC contraction of the muscle cf CONCENTRIC- > load imposed on the tendon may exceed the yield point -> tendon rupture

Question 39

How can you categorize the injury to tendons/ligaments ?

Answer 39

Grade 1- mild- some pain but no joint laxity clinically Grade 2- moderate- severe pain and some joint laxity clinically PROGESSIVE failure of collagen taken place->partial rupture Grade 3- severe - severe pain occurs at trauma, less pain post, clinically completely unstable- most collagen fibres have ruptured

Question 40

Can you describe the stages of healing of ligaments/ tendons?

Answer 40

1) HAEMORRHAGIC/ INFLAMMATORY - formation of a HEMATOMA within DAMAGED region and intimation of a RAPID INFLAMMATORY RESPONSE -> invasion of polymorphous nuclear cells and monocytes/ macrophages-> released of cytokines and growth factors. Monocytes remove debris and FIBROELASTIC CELLS begin to appear. Last few hours-days 2) PROLIFERATION - new blood vessels are formed and fibroblasts recruited from local environment/ circulation -> new collagen matrix- initially type 3. New matrix increases in mass and becomes less viscous and more elastic as inflammation decreases - weeks 3) REMODELLING- starts within weeks of injury , lasts years. Characterised by PROGRESSIVE MATURATION and CONVERSION OF COLLAGEN from TYPE 3 to TYPE 1, REORIENTATION IN RESPONSE TO LOADS and REORGANISATION OF MATRIX

Question 41

When are surgical tendon repairs weakest?

Answer 41

In the first week, regaining most of their strength by 3-4 weeks and MAX STRENGTH at 6 MONTHS

Question 42

What factors affect healing of ligaments/ tendons?

Answer 42

1)MOBILISATION- ligaments and tendons appear to remodel IN RESPONSE TO MECHANICAL DEMANDS placed upon them. Controlled movement- has benefit of healing , increasing TENSILE STRENGTH of tendons and lig- bone interface by stimulating SYNTHESIS of COLLAGEN and PROTEOGLYCAN weaker if immobilise- more immature collagen produced-> weaker 2) SURGERY- calibre of suture, suture strands suture technique and peripheral epitendinous or sheath repair effects the strength of the healing process. 3) BIOLOGICAL / BIOCHEMICAL MANIPULATION- using growth factors - epidermal growth factor and platelet derived growth factor increase FIBROBLAST proliferation invitro. Steriods and hyaluronate - decrease adhesions but decrease rate and strength of healing and increase infection. 4) Joint INSTABILTY -in an unstable joint the healing is inferior