Advanced Anatomy Flashcards
Blood supple to skeletal muscle
Rich blood supply and vessels interact with muscle cells and satellite cells
Microcirculation in muscle supports muscle contraction with arcades of arterioles in the perimysium giving rise to transverse terminal arterioles which penetrate the endomysium forming a capillary network
Blood from one terminal arteriole is collected into a venule and is known as a micro vascular unit MVU representing functional unit of blood flow regulation in skeletal muscle
Structure of skeletal muscle
Muscle fibres is composed of many myofibrils with sarcoplasm linking them encased in the sarcolemma with satellite cells in the periphery
Many muscle fibres together bound by the endomysium form a fascicle
Many fascicles with artery’s nerves and veins separated by perimysium internally and epimysium externally make the whole muscle which is covered in deep fascia
Describe sarcomeres
Two Z lines, myomesin in the centre two c proteins either side and distance between is the M line
Actin extends from z lines inwards overlapping with myosin thick fibres
Length of myosin is the A band
Length between ends of actin molecules is the H band
Length between myosin of different sarcomeres is the I band
Tropomyosin and troponin bound to actin
Nebulin extends from z band along length of the actin filament. Acts as a template for regulation of filament length
Titin extends from z disc to the M line closely associated segment with myosin and maintains central positioning in sarcomere. During relaxation also generates passive tension through elastic extension when sarcomere is stretched
Contraction cycle cross bridge
Attachment- myosin head tightly bound to actin molecule of thin filament (rigor state)
Release- ATP binds to myosin head indices release of actin and muscle relaxes - without ATP can stay in state of rigor
Bending- ATP causes myosin head to bend and initiates breakdown of ATP to ADP and inorganic phosphate which remain there
Myosin head binds to new actin site and iP is released
Release increases binding affinity
Myosin generates force to straighten and in doing so performs power stroke moving 5nm shortening the sarcomere
ADP lost during this stage
Release of ADP results in reattachment of myosin head to actin filament and rigor state reestablished
Contraction overview
Ach released from axon terminal of motor neurone binds to Na ligand gated channels on motor end plate
Elicits end plate potential from increased intracellular Na triggering action potential
Propagates along sarcolemma down t tubules
Triggers release of Ca from SR
Ca binds to troponin exposing myosin bonding sites by conformational change
Cross bridge cycle begins
Ca actively pumped back into SR
Tropomyosin blocks myosin bonding site again and muscle relaxes
Muscle origin
Muscle fibres are of mesodermal origin with muscles of trunk and limbs also tongue and larynx derived from paraxial mesoderm which forms somites
Muscle of orbit and face, pharynx and mastication arise directly from mesoderm
Myogenesis
Proliferating stage and migration stage from the dermomyotome to form myotome
Initial cells are founder cells and these determine mature muscles destinations
Joined by fusion competent myoblasts to muscle cells
Once aligned the pores form in FCM allowing invasion of FC
Expansion of pores allows cytoplasmic exchange and finally membrane fusion.
From this point myogenic differentiation begins as cells exit cell cycle and express specific markers
Post natal growth of muscle
Accomplished by satellite cells mostly which are also activated in muscle damage where they proliferate and fuse to make myofibrils to regenerate tissue
Some cells undergo asymmetric cells division to renew satellite population
In foetal muscle 30% of nuclei are from satellite cells whereas in adult only 3.8% of nuclei are from satellite cells
During development and regeneration the nuclei are found centrally migrating to the periphery as sarcomeres mature
Satellite cells
Located outside the sarcolemma but within basal lamina
Large nucleus to cytoplasmic ratio
Proliferate and differentiate to form terminally differentiated multinucleated myofibers
Two types - true stem cells divide asymmetrically to give one stem cell and one daughter fated to become muscle cells
Other satellites already fated to become muscle cells
Development and migration of fibres
6 processes occur
Direction of muscle fibres may change from original cranial-caudal orientation with only few muscles retaining original orientation eg rectus abdominis and erector spinae
Portions of successive myotomes commonly fuse to form single composite muscle eg rectus abdominis
Myotomes may split longitudinally into two or more layers eg intercostal
Muscle may split into two or more parts eg trapezius and sternocleidomastoid
Portion of muscle or whole muscle may degenerate leaving sheet of connective tissue ie an apponeurosis
Myotome may migrate eg diaphragm, latissimus dorsi, serratus anterior
Nerve supply maintained giving us clues to the origin
Muscle maturation
Occurs in childhood
Initially muscle is slow to relax but this increases to reach adult values by ten years old
Strength gains follow typical growth curve for height and weight and mass is gained before strength
Makes up 25% body bulk at birth but this increases 3.5 times in females and 5 in males by full growth.
Muscle fibre types
Type I cells characterised by endurance and little force
Type IIA fast fibres recruited second
Type IIB/X recruited last fast fibres lots of force no duration
Muscle training
Increasing strength increases the number of sarcomeres and therefore cross sectional area
Endurance increases delivery of oxygen to muscle and ability of cell of utilise it increasing VO2 max, CO and neuromuscular excitability
Training decreases resting HR due to overload from working harder
No overlap between strength and endurance
Strength - high force low repetition activating type II fibres
Endurance - low force high repetition activated type I fibres
Muscle fatigue
Under constant contraction will eventually fatigue due to exercise induced reduction in ability of muscle to produce force or power.
May be due to many things no one consensus
K leaving cell at each activation so repeated activity can increase extra cellular K altering excitability of cell
Decreased Ca sensitivity so doesn’t bind to troponin exposing binding sites
PCr+ADP+H gives Cr+ATP. Inorganic phosphate released may cause Decrease in Ca sensitivity and release so is considered major cause of fatigue
Accumulation of lactic acid but recent studies show has little impact on force production but is easy to measure and gives good indication of anaerobic metabolism in exercise
Intense exercise reduces ATP and Ca release decreasing rate of ATP usage reducing power output
Energy available in glycogen directly correlates to fatigue and may cause decrease of Ca release so store of energy runs out
Neural crest cells fate
Melanocytes Schwann cells Adrenal medullary cells Dorsal root ganglion cells Cranial nerve sensory cells Autonomic ganglion cells
Dermatome overlap and discrepancy
Can overlap except on axial lines - non adjacent spinal segments (debatable)
Peripheral nerves can overlap eg median and ulnar nerve supplying the first and middle phalanges- median 3 1/2 ulnar 1 1/2 but this not always the case
Sometimes they do not overlap eg the thenar eminence and in limbs they remain in the specified dermatome pattern.
However dermatome maps are very inconclusive there are 14 official versions very inconsistent
Foresters tactile map
Tactile dermatomal areas are larger than those determined by pain and temperature
No clinical loss if only one spinal nerve is severed aside from c2
Few subjects were studied cervical dermatomes based on 2-5 patients per nerve
No documentation regarding delay between section and testing - unsure of how long between severing and test for sensation was performed possibly different every time. Other nerves may have had enough time to compensate
Head and Campbell’s map
Herpes linked to specific spinal nerves
Single spinal nerve involved in infection in only 16 cases of 450 patients therefore only 16 true samples
Small sample size 1-3 cases per nerve
Not all cutaneous nerves in a single spinal nerve will be affected and hence not all will show eruptive lesions.
Not every nerve studied
Keegan and garretts map
Prolapse of vertebral discs in different regions of spinal cord will vary in severity eg cervical vs lumbar
Also mixed with vertebral fractures making results different
Prolapse may affect part of posterior root the whole of a posterior root or more than one root
Can also affect roots higher or lower than affected segment
Never studied c2 and thoracic dermatomes
Subsequent study by Davis et al 1952 tried to replicate this study showed contradicting results
Myotomes of upper limb
Shoulder - abduction, lateral rotation - c5 Adduction and medial rotation - c6-8 Elbow - flexion - c5,6 Extension - c7,8 Forearm - pronation - c7,8 Supination - c6 Wrist - flexion and extension - c6,7 Fingers - flexion, extension long muscles - c7,8 Hand - intrinsic muscles - c8,t1
Root and origin of brachial plexus terminal nerves
Musculocutaneous - c5-7 branch of lateral cord innervates flexors at elbow: coracobrachialis, biceps and brachialis. Sensory cutaneous: skin over radial boarder of forearm
Axillary - c5,6 branch of posterior cord. Motor nerves to deltoid, teres minor muscles. Sensory to shoulder joint and cutaneous to skin over shoulder and lateral arm
Radial nerve- c5-t1 continuation of posterior cord. Motor innervation to extensors of elbow, wrist and hand. Sensory to elbow wrist and hand joints and cutaneous to skin over dorsum of hand.
Ulnar nerve - c7-t1 continuation of medial cord. Motor innervation to wrist and hand flexors and intrinsic hand muscles. Sensory to hand joints and cutaneous to skin of ulnar aspect of hand.
Median nerve- c5-t1 arises from medial and lateral cords. Motor innervation to most long flexors of forearm and thenar muscles. Sensory cutaneous to skin of elbow, wrist and radial aspect of palm of hand.
Brachial plexus roots, trunk, divisions, cords and terminal branches
C5 and C6 roots join and branch dorsal scapula nerve and contribute to long thoracic - superior trunk branches subclavian and suprascapula nerves- anterior superior division branch posterior superior nerve to join posterior middle division - lateral cord branches lateral pectoral nerve - musculocutaneous nerve terminates branch contributes to median nerve with C8 and T1
C7 root contributes to long thoracic nerve - middle trunk no branches - posterior middle division sends anterior middle branch to join anterior superior division and joined by posterior superior and inferior from superior and inferior divisions respectively - posterior cord branches upper subscapular, thoracodorsal and lower subscapular nerves - radial nerve branches auxiliary
C8 and T1 join - inferior trunk - anterior inferior division branches posterior inferior branch to posterior middle division- medial cord branches medial brachial cutaneous, medial pectoral and medial anterior brachial cutaneous - branch contribute to median nerve with C5 and 6 and terminates in ulnar nerve
Musculocutaneous nerve
Roots c5-7 supplies three muscles; coracobrachialis, biceps brachii and brachialis
Terminates in lateral cutaneous nerve to forearm
Upper plexus lesion results in low of elbow flexion and lateral forearm numbness can be caused by shoulder dislocations or anterior shoulder surgery
Radial nerve
Roots c5-t1 is the posterior cord from posterior divisions of all three trunks
Lies posterior to auxiliary artery in Axilla
Passes posteriorly via triangular interval with profunda brachi artery
Supplies triceps brachi, anconeus and brachioradialis above elbow is a forearm extensor below elbow supplying extensor carpi radialis, and EXR brevis, extensor carpi ulnaris, extensor digiti minimus, extensor digitorum, extensor indicis, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus
Sensory effects in wrist capsule through first webspace
Median nerve
Roots c6-t1 branches from medial and lateral cords
No branches in upper arm
Crosses brachial artery lateral to medial to medial boarder or biceps
Enters antecubital fossa medial to brachial artery and biceps tendon
Supplies palmaris longus, flexor carpi radialis, pronator teres, flexor digitorum superficialis and profundus I and II, flexor pollicis longus, pronator quadratus, abductor pollicis brevis, flexor pollicis brevis, opponens pollicis
Passes between two heads of pronator teres and travels through carpal tunnel giving recurrent motor branches to thenar eminence supplying LOAF muscles
Gives off palmar cutaneous branch 4 Cm before wrist
Ulnar nerve
Roots c8 and t1 from medial cord terminal branch
Stays medial in upper arm passes posterior to medial epicondyle within cubical tunnel
Enters medial forearm supplying flexor carpi ulnaris and ulnar half of flexor digitorum profundus
Pierces two heads of FCU travels deep to Flexor digitorum superficialis next to ulnar giving off palmar cutaneous branch
Enters hand via guyons canal and divides into deep motor and superficial sensory branches palmar cutaneous supplying medial palm.
Deep motor branch supplies intrinsic of hand except LOAF muscles (supplies by median)
Dorsal cutaneous branch 5cm proximal to wrist supplies dorsal hand provides digital sensation to the ulnar side for half the digits
Variations in the brachial plexus
C4-8 prefixed plexus 22% variance
C6-T2 postfixed plexus 1% variance
5% variation in trunks
34% in divisions
18% in cords also common
Occasionally nerves may vary in position relative to the axillary artery
There are often inter-nerve communications in the terminal branches (20% or more)
C4 prefixed route
C4 goes to dorsal scapula nerve (95% go directly rather than via plexus) 98% suprascapular nerve 79% musculocutaneous nerve 49% axillary nerve 16% subclavian nerve
Inter-nerve communications
Martin-gruber anastomoses in forearm - a communicating branch median and ulnar nerve in 10-25% people and is bilateral in 40% cases.
Berrettinis ramus communications seen in 40-45% people - superficial palmar communication between the median and ulnar nerve
Riche-cannieu anastomoses present in 77% of people - communication between recurrent branch of median nerve and deep branch of ulnar nerve in hand.
Muscle strength training
Slight dip in muscle mass first 24/48 hours post exercise due to muscle damage sustained
Results in
Motor learning - performance improves but no strength increase during 6-8weeks
Increase strength but not size of muscle maybe due to synchronisation of motor unit firing and increased ability to recruit all available motor units or change the fibre architecture eg packing density or contractile material increases
10-12 weeks slow but steady increase in muscle size and strength by hypertrophy. Significant and prolonged activity needed to cause change in muscle structure
Muscle performance
Influenced by turnover of contractile cells promoting loss of gain of mass
Muscle protein synthesis enhanced for 24-48 hours post single bout of resistance training
Training also increases satellite cells needed to fuse with muscle fibre to increase size of cells
Greater satellite activation means greater muscle mass increase seemingly associated mostly with eccentric contraction rather than concentric.
Role of satellite cells in hypertrophy
Increase in muscle protein during hypertrophy can be achieved by either increased RNA and protein synthesis from existing nuclei or increase number of nuclei and keep same level of synthesis
Nuclei come from satellite cells
Resistance training very effective in producing new satellite cells
Satellite production exceeds muscle hypertrophy
Endurance and muscle composition
Exercises increase oxygen demands of working muscle therefore the endurance of muscle depends on rate of o2 delivery and utilisation
Age related changes to o2 uptake may explain decrease of endurance with age
Increases satellite cells and CV and respiratory systems improve o2 delivery and cells increase o2 utilisation.
Capillary density increases for greater diffusion distance of o2 improving delivery to mitochondria
Mitochondria change and increase in size and number to improve o2 metabolism.
Glucose uptake also enhanced as is insulin sensitivity which counteracts insulin resistance in type II diabetes
Increases fatty acid metabolism leads to better preserved glucose store and increased endurance
Cardiac muscle hypertrophies increasing CO and resting heart rate decreases overall results prolonging time exercise can be done for
Enhanced mitochondria and exercise
After training is associated with less breakdown of high energy phosphates during submaximal exercise so less AMP and Pi accumulate lowering rate of fatigue and glycogenolysis
Higher glycogen levels can also delay fatigue by preventing decrease in SR Ca release which occurs when glycogen localised in myofibrils reaches lower levels
Overtraining.
May lead to chronic fatigue and loss of muscle strength
Early indication may be decrease in neuromuscular excitability usually result of endurance training
Estimated occurs in 30% non elite and 60% elite athletes during sporting lifetime
Due to successive alterations in metabolism where main energetic stores shift from carbohydrates and lipid proteins
Need to cut back in exercise
Muscle regeneration
Satellite cells activated in response to physiological stimuli of exercise or pathology eg injury/disease
Satellite cells are heterogenous mix of stem cells and committed myogenic progenitors
Some activated cells divide asymmetrically suggesting one remains a stem cell while other differentiates
May be different populations of stem cells not all of which unite with muscle fibre
Cells must then make transition from proliferation to differentiation
The fusion of cells produce new myofibers or fusion of cells to damaged myofibers
Has central nuclei which as ages move to periphery
Age, gender and muscle
Peak muscle and bone strength between 25-30 years, skeletal muscle mass decreases at 6% per decade after 30 impacting basal energy needs and max aerobic capacity.
Age related effects severely reduce strength of extensor muscles of lower limb especially knee and ankle
Part of this due to reduction in physical activity
Loss of lower limb strength leads to increase in falls in elderly 28-35% over 65 have at least one fall per year
By 90 about 30% muscle mass lost
Decrease in strength equal for all groups despite continued training
Life long endurance training gives high aerobic power but muscle strength is still the same
Endurance limiting factor is VO2 max and after mid 20’s this slowly declines so by 70 is half of peak value
Weakness and fatigue can be slowed but not stopped
Muscle fibre atrophy result of individual fibre atrophy and decrease in number of fibres with preferential loss of type II
Loss of muscle force suggesting dysfunctional proteins - myosin heavy chain synthesis declines with age
Decreased ability to remodel muscle after injury reducing strength and endurance
Decrease in use of myosin head decreasing force with age
Loss of satellite cells may result in failure to maintain muscle cell fibre size may explain higher prevalence of muscle injuries and longer recovery times
Increase in proportion of connective tissue increases stiffness
Endurance and elderly
Enhanced muscle insulin sensitivity in everyone so useful for elderly especially preventing decline in mitochondrial respiratory capacity with age
Resistance exercise gains strength and power for this too
Gender and muscle composition
In adolescent girls and women relationship between muscle strength, height and weight is similar to children’s but adolescent boys there is hypertrophy of muscle probably due to increased testosterone
Women show greater loss of muscle size and strength but may be reduced by use of HRT.
All factors affecting muscle composition
Atrophy Motor units number Changes in nervous system Diet Physical activity Endocrine changes Altered enzyme activity levels Altered muscle contractility
Shoulder joints
Acromioclavicular - gliding Joint less movement than others
Scapulothoracic
Sternoclavicular - physically a saddle joint but functionally a ball and socket joint
Glenohumeral - ball and socket
The glenohumeral joint
Ball and socket synovial joint
Lax capsule to allow movement - very weak capsule hangs dependent underneath joint therefore making it very unstable
Most common dislocation in body however only affects 1-2% of population
Head of humerus is 3-4x larger than the glenoid fossa therefore it doesn’t sit in the joint entirely also making it unstable
Stability of the joint comes from the rotator cuff muscles and ligaments
Glenoid labrum helps deepen glenoid cavity by 2.5mm however is prone to damage from dislocations or from age etc. Causing tears or detachment. Also acts as anchoring point for ligaments
Subscapular bursa - can also get bursa infraspinatus but not common.
Blood supply from suprascapular, subscapular, anterior and posterior circumflex humeral arteries
Innervated by axillary, suprascapular, lateral pectoral nerves
Factors for glenohumeral stability
Glenoid fossa and humeral head mismatch size
Glenoid labrum helps deepen cavity 2.5mm. Acts as chock block and attachment site for ligaments and long head of biceps. 20% of joint compression effect.
Glenohumeral, coracoacromial and corcacohueral ligaments help stabilise
Intra articular pressure - negative pressure creates suction between bones holding joint together. If pressure is dissipated dislocation very likely
Muscles - rotator cuff (supraspinatus for abduction, teres minor, infraspinatus and subscapularis), long head of biceps and deltoid very important
Position and shape of glenoid fossa
Slight angulation as scapula runs lateral and forward to meet head of humerus meaning plane of flexion and extension is offset slightly which may be beneficial for resisting anterior pressures eg pushing something
A glenoid notch shape in glenoid fossa is present in 55% of patients which often gives rise to potential problems from bending the glenoid labrum making tearing or anterior detachment of the labrum more likely.
Ligaments of glenohumeral joint
Superior, middle and inferior glenohumeral ligaments extend from the scapula to the head of the humerus
Superior - supraglenoid tubercle to lesser tuberosity blends with coracohumeral ligament to close the rotator interval
Middle - labrum or bony glenoid neck to medial to lesser tuberosity inferior to subscapularis tendon, often stretched by heavy lifting
Inferior - hammock shaped important for arm abduction to cup head.
Between the superior and middle protrudes the supscapular bursa
Long head of biceps femoris is continuous with the glenoid labrum
Coracohumeral ligament goes from the coracoid process to the humerus
Transverse ligament runs above the glenohumeral ligaments over the long head of biceps attachment
Stability of shoulder from muscles
Primary - rotator cuff muscles (supraspinatus, infraspinatus, subscapular and teres minor), Deltoid and long head of biceps
Secondary - teres major, latissimus dorsi, pectoralis major
The cuff muscles actively resist deltoid shear forces - the glenohumeral joint compression centres the humeral head making more stable
Rotator cuff tendons blend into the capsule - cuff tension actively tightens glenohumeral ligaments
Proprioceotion - joint position awareness and repositioning through continuous afferent input and efferent output
Sternoclavicular joint
Synovial articular disc
60 degree superior inferior movement
20 degree anterior posterior movement
Anterior and posterior sternoclavicular ligaments stabilise
Interclavicular and costoclavicular ligaments
Blood supply from clavicular branch of thoacoacromial artery and internal thoracic
Nerve supply from nerve to subclavius and medial supraclavicular nerve
Acromioclavicular joint
Small area of contact
Synovial possible with disc
Lax capsule for movement
Acromioclavicular ligament
Blood supply from suprascapular artery and posterior circumflex humeral and acromial branch of the thoracoacromial artery
Innervation axillary, suprascapular and lateral pectoral nerve
Coracoclavicular ligament formed from the trapezoid and conoid ligaments
Purpose of the spine
Protect the spinal cord
Provide structural support and balance upright posture
Enable movement - flexion, rotation etc.
Bony compartments of the spine
7 cervical 12 thoracic 5 lumbar 5 sacral 4 Coccyx
33 total
Vertebrate anatomy
Body -75% of longitudinal load Foramen for nerves to travel Transverse and spinous processes Pedicle connects body to processes Lamina connects transverse to spinous processes Posterior parts support 25% load.
Differences between vertebrae -
Cervical - three main distinguishing features:
Bifid spinous process – the spinous process bifurcates at its distal end.
Exceptions to this are C1 (no spinous process) and C7 (spinous process is longer than that of C2-C6 and may not bifurcate).
Transverse foramina – an opening in each transverse process, through which the vertebral arteries travel to the brain.
Triangular vertebral foramen
Two cervical vertebrae that are unique. C1 and C2 (called the atlas and axis respectively), are specialised to allow for the movement of the head.
Thoracic - medium-sized, and increase in size from superior to inferior. Their specialised function is to articulate with ribs, producing the bony thorax.
Each thoracic vertebra has two -demi facets,- superiorly and inferiorly placed on either side of its vertebral body. The demi facets articulate with the heads of two different ribs.
On the transverse processes of the thoracic vertebrae, there is a costal facet for articulation with the shaft of a single rib. For example, the head of Rib 2 articulates with the inferior demi facet of thoracic vertebra 1 (T1) and the superior demi facet of T2, while the shaft of Rib 2 articulates with the costal facets of T2.
The spinous processes of thoracic vertebrae are oriented obliquely inferiorly and posteriorly. In contrast to the cervical vertebrae, the vertebral foramen of thoracic vertebrae is circular.
Lumbar - large vertebral bodies, which are kidney-shaped. They lack the characteristic features of other vertebrae, with no transverse foramina, costal facets, or bifid spinous processes.
However, like the cervical vertebrae, they have a triangular-shaped vertebral foramen. Their spinous processes are shorter than those of thoracic vertebrae and do not extend inferiorly below the level of the vertebral body.
Their size and orientation allows for clinical access to the spinal canal and spinal cord between lumbar vertebrae (which would not be possible between thoracic vertebrae). Examples include epidural anaesthesia administration and lumbar puncture.
Intervertebral disc anatomy
Annulus fibrosus outer section
Nucleus pulposus inner section
Ligaments of the spine
Ligamentum flavum - runs between one vertebrate to another in the foramen
Interspinous ligament - runs over the superior and inferior articulating processes
Intertransverse ligaments - between transverse processes of superior and inferior vertebrae
Posterior longitudinal ligament - runs whole length of spine inside foramen anterior to ligamentum flavum
Anterior longitudinal ligament - runs whole length of spine on anterior body of vertebrae
Supraspinous ligament - runs length of whole spine on spiney processes
Kinematic variables
Type of motion occuring
Location of movement
Direction of movement
Magnitude of motion
Types of motion
Rotation
Translatory - each section of limb involved moves the same distance at the same time in the same plane
Curvilinear (rotators and translating)
General plane motion - could be special case of curvilinear motion where object rotates about the axis while the axis is translated by motion of adjacent segment eg the forearm and hand moves in parabolic path as it rotates around elbow joint and elbow is moved by shoulder
Location of movement
Frontal plane divides body into front and back
Sagittal plane divides into right and left
Transverse plane divides into upper and lower segments
Movement takes place along three axis which are perpendicular to Plane of movement
Frontal - abduction, addiction and lateral flexion
Sagittal - flexion and extension
Horizontal - rotation
Uniaxial, biaxial and triaxial joint movements and gliding
Uniaxial joint has movement into one plane with one degree of freedom eg flexion and extension
Biaxial joint has two planes of movement eg abduction and adduction as well as flexion and extension
Triaxial joints/multiaxial has three degrees of freedom with third movement involved eg rotation
Not all joint movements are within planes as some joints are non axial and perform gliding movements in all directions - only very small movements permitted
Velocity of movement
Displacement per unit time regardless of direction Is known as speed whereas displacement per unit time in given direction is velocity
Changes in velocity per unit time is acceleration
Rate of movement used to know rate of acceleration or deceleration
eg swinging limb in gait cycle accelerates in initial swing but decelerates before contact with ground to minimise ground reaction force
forces affecting kinetics
External - Gravity Wind Mechanical force etc Internal - Muscles Ligaments Bones May be use to counteract external forces Both - Friction and atmospheric pressure may act as both internal and external forces
Force vectors
All forces are vector quantities and have:
A point of application on the objects being acted on
An action line in direction indicating a pull towards source or push away from source
A magnitude ie the quantity of force exerted
Vectors are represented by an arrow with point at point of application, shaft and arrowhead in direction of force and length representing magnitude
Centre of gravity
COG is a hypothetical point which all mass is concentrated and the point at which force appears to act
COG is point at which the object is held in balance and the line or direction of gravity is always downwards
In humans COG depends on proportions of the person and also their position. This centre and one change as the person moves
For an object to be stable the line of gravity must pass within the base of support and when outside this the object will fall
Larger the base of support the closer the COG to the base of support and the greater stability of the object
Bipedal (humans) have small bases of support
Reaction forces
Newton’s third law - forces always come in pairs
Gravity exerts force and things that touch objects exert force on the object
Whenever two objects are in contact they exert force in each other
Internal forces generated by muscles, joint capsules, ligaments to counteract external forces like ground reaction forces in gait cycle.
Muscles deemed internal moments - flexor or extensor moments opposing forces
A moment is a measure of force tendency to cause the body to rotate about a specific axis
For a moment to develop the force must act to cause the body to twist as a moment is due to a force not having an equal and opposite force along its line of action
Newton’s first law states objects in equilibrium will remain at rest or not move unless acted upon by an unbalanced force and forces must therefore equal 0
Newton’s second law - objects in motion acceleration will be proportional to forces acting. A=F/m or F=ma
Acceleration=force/mass
Kinematic chain
An engineering term to describe series of segments joined together and fixed at each end, closed chain
Movement of one segment causes the next and so on
In humans long bones represent chains and explains why movement at one joint affects another
When limbs are not fixed the chain is open which is most common limb use eg foot off the ground in walking while closed chain is when pushing against a solid object eg foot on in walking or pushing against a wall
Concept is only useful when elements are fixed such as when triceps extend arm with open chain but when closed the extension of arm moves away from the body eg press up motion this is due to the closed chain pushing against a force eg a wall while the open chain has less force so moves differently
Common shoulder condition causes
Fractured clavicle Sternoclavicular joint dislocation Acromioclavicular dislocation Glenohumeral instability Rotator cuff tears Rotator cuff tendinitis Impingement syndrome - rotator cuff muscles irritated and inflamed when passing through the subacromial space causing pain Frozen shoulder - adhesive capsulitis, painful, connective tissue of glenohumeral joint becomes inflamed and stiff restricting motion Glenohumeral arthritis
Top shoulder conditions for different ages
31-45 - incomplete cuff lesion and frozen shoulder most common but very close
Above 45 - degenerative joint disease, frozen shoulder and full thickness cuff tear most prominent not much else
More female related injury in all age ranges
Clavicle fractures and sternoclavicular and acromioclavicular dislocations
Clavicle fractures and dislocations very easy to spot
Bones move towards the ligaments or muscles attached to them causing large displacement
Fracture most common in medial third of clavicle due to being half way between ligaments either side making it weakest point
Can get medial or lateral breaks more commonly the acromial side changing shape and look completely
Sternoclavicular joint dislocations most commonly dislocate anteriorly, tearing ligaments. This is caused by force to lateral aspect of shoulder thrusting coracoid process back and clavicle forward. Posteriorly may be life threatening as the clavicle may compress or lacerate al lung, great vessel eg subclavian vein tearing or crushing, trachea or oesophagus all which lie behind it
Usually caused by a fall or sports with force on the shoulder
Acromioclavicular joint dislocation caused by downward blows to lateral shoulder or fall in outstretched arm.
Avascular necrosis of glenohumeral joint
Hass’ disease - very advanced stages of avascular necrosis
In radiology can see dense sclerosis over head of humerus ‘the snowcapped sign’
Caused by loss of blood supply to humeral head, axillary artery main branch gives off anterior and posterior humeral circumflex arteries and anastomoses with vessels from rotator cuffs
Can be caused by lax capsule moving humerus too high in glenoid fossa not sitting correctly and muscles pulling head upwards with nothing preventing them trapping arteries etc. Resulting in necrosis
Rotator cuff tears and glenoid labrum tears
Progressive thinning and weakening of muscles with age increases likelihood of potential damage to cuff during elevation of the humerus tearing the muscles
Glenoid labrum can have SLAP (superior to lateral, anterior to posterior lesion) lesions on superior head of humerus associated with long head of biceps attachment and labrum can be completely torn off here. or bankart tears on underside anterior of capsule
Most common cause of shoulder pain and instability leading to secondary problems
GHJ impingement syndrome
Occurs when a bursae or tendon is squeezed between moving structures
Supraspinatus is commonly impinged
Common in sports that emphasise overhead arm movements
Frozen shoulder
Adhesive capsulitis
Symptomatic limitation of passive motion of shoulder
Caused by thickening and stiffening of joint capsule after inflammation of rotator cuff tendons
No evidence of arthritis, calcium deposits or other abnormalities seen
Four types -
Idiopathic - most common, unknown cause
Diabetic - may be due to excess sugar in bloodstream
Post traumatic stiff shoulder
Post surgical stiff shoulder
Previous damage caused flaring of pain
Peak incidence age is 55
Glenohumeral dislocations
More common to dislocate anteriorly
More prone to dislocate in a 180degrees abducted arm position
Taking a Y view X ray allows good diagnosis of dislocation
Patient stands with back facing x ray diagonally with scapula being first bone in x ray picture and humerus furthest away from imagining
Impingement syndrome
rotator cuff muscles irritated and inflamed when passing through the subacromial space causing pain
Can cause development of Sesemoid bone from inflammation called subacromial roughness can be palpated or calcific tendinitis from irritations, Ca deposits build up forming solid bodies
Acromial spur
Reactive changes in greater tuberosity of humerus causes acromial spur growth
Painful arc syndrome
60-120 abduction is very very painful from excess compression on bursae of shoulder but once rotation at 120 degrees begins pain lessens
The notochord
A cellular rod forming the primitive axis of the embryo giving it rigidity.
The rod forms the mesenchymal axial skeleton and is the basis for the axial skeleton (vertebral column, Ribs, sternum and skull). The developing notochord induces the ectoderm to form the neural plate which develops into the CNS.
Somite development week 4
mesoderm cells are arranged around a small cavity. The cells of the anterior and medial walls of somite lose epithelial arrangement and migrate in the direction of the notochord (sclerotome).
The posterior somite gives rise to myotome layer
The dermatome cells lose their epithelial configuration and spread out under the ectoderm to become the dermis.
Sclerotome development
Sclerotome - the region of bone and periosteum that is innervated by a single spinal nerve.
week 4- The compact arrangement of somite changes to become more diffuse as a result of downregulation of N cadherin (main adhesion protein holding epithelial cells together in sheet arrangement)
Cells shift to surround the notochord and spinal cord. These are called the sclerotome (forming the mesenchyme) and form the vertebral column.
The development is in response to bmp and Wnt signalling from the ectoderm and Shh from the notochord and the neural tube floor plate (Chan et al 2014).
The sclerotome maintains it’s segmented nature as the blocks are separated by less dense areas containing intersegmental arteries. Each sclerotome consists of loosely arranged cells cranially and densely packed cells caudally. Shh regulates the sclerotome and it’s subsequent differentiation into axial skeleton. In absence of Shh the vertebral column doesn’t form.
Further development occurs as the caudal portion of each sclerotome proliferates and condenses and binds to the cephalic part of the adjacent sclerotome - the precartilaginous vertebral body (resegmentation). PAX1 is expressed in 7-8 week old foetuses suggesting it has a role in segmentation between the condensed and less condensed regions.
Resegmentation remarks theory
For movement to occur in the vertebral column each muscle must insert into two successive vertebrae. To achieve this the sclerotome must shift by half a segment with respect to the dermatome development.
The resegmentation model was proposed by remark in 1855 to explain the realignment of the the vertebrae with respect to the muscles.
Observed each sclerotome is subdivided into superior and inferior halves with different densities and separated by an intersegmental fissure. He suggested that to form a vertebra that half the sclerotomes from adjacent somite unite. Study by ward et al 2017 confirmed this theory.
IVD formation
Mesenchymal cells between the cephalic and and caudal parts of the sclerotome don’t proliferate but fill the space between two precartilaginous vertebral bodies and in this way contribute to the formation of the intervertebral discs. The notochord regresses in the region of the vertebral bodies but persists and enlarges in the region of the IVD. Lineage tracing studies show the notochord cells from the nucleus pulposus which is later surrounded by the annulus fibrosus AN which combined from the IVD. The AN is formed from the sclerotome and isn’t clear how the AN cell are directed or oriented into the correct lamellar arrangement or the signal to lay down the ECM material.
Spinal nerves c1-t2 and sclerotomes
The cranial part of sclerotome from c1 fuses with the caudal part of occipital 4 which then forms part of the base of the skull and explains why there are 8 cervical spinal nerves and 7 cervical vertebrae
Chondrification of vertebrae
During 6th week of development chondrification centres appear in each mesenchymal vertebra
At the end of the embryonic period the two centres fuse to form the cartilaginous body
The centres in the vertebral arch fuse with each other and the body
The spinous and transverse processes develop from extensions of the chrondrification centres in the vertebral arch.
Ossification of the vertebra
Ossification begins during the embryonic period and ends about the 25th year
Initially there are two primary ossification centres which soon fuse. Failure of one of these to develop leads to a wedge shaped vertebral body
Two other centres are present one in each half of the vertebral arch appearing at about 8 weeks gestation.
At birth each vertebra consists of three parts united by cartilage
Postnatal development- two parts of the vertebral arch fuse during the first 3-5 years. Union begins in the lumbar vertebrae and progresses cranially. The joint between the arch and body disappears during 3-6 years. Until puberty the upper and lower surfaces of the body and tips of the processes remain cartilaginous when 5 secondary ossification centres appear. In the bifid cervical spines two processes appear. Final fusion occurs at about 25 years. Also until puberty the diameter and volume of the IVD increases with the vertebral column. Additional lamellae are formed but the mechanism is unknown. Chan et al 2014.
Rib development
Develop from costal processes of thoracic vertebrae
Original union is replaced by synovial joints in thoracic region
Sacrum development
Costal elements unite to the body and arch between ages 2-5
The peripheral parts of bodies unite after the 20th year but the discs may persist until after middle life
Growth and development of vertebral column
Growth of components determine its overall length and contribution to height of the adult. The components have different growth rates which are reflected in changes in proportion between birth and adulthood
The lumbar and sacral vertebrae are relatively smaller at birth then in the adult when compared to the thoracic and cervical and thus grow the most. Thickness and height increase by growth at the annular epiphyses
Vertebral column length is assessed by sitting height and in second year of life grows 5cm after which it grows 2.5cm per year until around 7 years when it grows around 1.5cm until puberty where has peak growth velocity of 4cm a year. Females on average add 6-11cm and males 7-12cm during puberty. Growth is 99% complete in females by 15 and males by 17.
Adolescent growth spurt adds length due to the multiplicity of growth plates and therefore contributes a larger amount in overall height. The epiphysis close much later than those of long bones and may be seen into early 20s. The thoracic are present than other regions. IVD make up between 1/4 to 1/3 of length of the column. Their contribution is variable due to their dynamic nature as fluid changes can occur rapidly in response to postural alterations eg standing and lying down.
Body proportions
Sitting height - Africans in USA and Africa have considerably longer legs than Europeans eg at sitting height 60cm euro have leg length of 45 Cm and African 51cm and Australian 61cm even longer. This is genetic origin but better environmental circumstances produce longer legs
Developmental abnormalities of vertebrae
Few vertebral columns have structural symmetry and anomalies are common. In transition areas such as base of skull and between the lumbar and sacral vertebral anomalies are more common
95% of people have 7 C, 12 T, 5L, 5S fused vertebrae about 3% have additional vertebrae and 2% have less.
Asymmetry of articular facets of synovial joints (articular tropism) may be cause of back pain and rotational instability which may lead to IVD problems
Most common problems are failure of vertebral development, non-union of elements and segmentation failure ie several fused together
Other problems - spina bifida, hemivertebrae/wedge vertebrae,
Spina bifida
Most common vertebral abnormalities
A non-union problem
Spina bifida occulta occurs when the vertebral arch fails to either to form or fails to fuse
Doesn’t occur in thoracic region and is common in S1 in 20% of people
Hemivertebrae
Aka wedge vertebrae
May be caused by failure of condensation at mesenchymal stage, failure of chondrification centre to develop from the mesenchyme or failure of ossification centre.
Ageing and degeneration in vertebrae
During ageing trabecular and cortical bone is lost throughout the skeleton in both genders. Trabecular bone loss is much greater than cortical and as much of the vertebral bodies consists of trabecular bone there is a loss of strength with integrity of bone declining
As bone mass is greater in males then females the loss is more marked in females especially after menopause when decrease in oestrogen results in less bone tissue being laid down. The loss of transverse trabeculae causes loss of height in the vertebra and may lead to micro fractures which further decrease the height. As the proportion of cortical bone increases the vertebrae becomes less resilient and more likely to fracture. Loss of trabeculae may also lead to a lack of support for the vertebral end plate and cause it to reform leading to bowing of vertebrae.
IVD degeneration
IVD change with age with reduction in proteoglycan content. Result is a decrease in amount of water being bound by the nucleus and annulus. Falls from 88% to between 65-72% in nucleus between birth and 75 years. There’s a gradual increase in the relative proportion of collagen content of discs and the fibrils increase in diameter which may be due to decrease in the progenitor cell population of the disc. Result is disc becomes less resilient and more rigid. Disc height may not be reduced with age and may increase in some cases. Degeneration of discs may lead to osteophyte formation.
Weakening of cartilaginous end plate can lead to dysfunction and degeneration of IVD with Schmorls nodes as most common defect which may also occur during adolescence cause is unknown.
Schmorls node grading
Grade 1 age 15-40
Grade 2 age 35-75 nucleus appears fibrous and contains some brown pigment it is not degenerating.
Grade 3 moderate degenerative changes with annulus bulging into nucleus. There is also end plate damage.
Grade 4 severe degeneration with disruption to both end plates. The disc is reduced to both end plates. The disc is reduced in height and appears pigmented.
Osteophytes
Outgrowths of healthy bone from vertebrae protecting against compressive forces
They consist of compact bone and can develop at any age in response to pressure on vertebral body or disc degeneration
Number of osteophytes increases with age
Biceps brachii variations
Occurrence of third head - in South African populations most commonly.
Evolution of coracobrachialis
Potentially the supracoracoideus and coracobrachialis muscles of dinosaur pectoral region evolve to form the two heads of corcacobrachialis in man.
Coracobrachialis is pierced by the musculocutaneous nerve, single upper and several lower branches
Supracondylar process of humerus
Avian spur
A bony projection on the anteriomedial aspect of humerus about 5cm above the medial epicondyle. Points towards the medial epicondyle.
Struthers ligament
A band of connective tissue at the medial aspect of the distal humerus
Courses from the supracondylar process to the medial humeral epicondyle.
Not a constant ligament, can be acquired or congenital.
Clinically significant due to median nerve and brachial artery which may pass underneath its arch, can becomes compressed leading to supracondylar process syndrome.
Ligament may also affect the ulnar nerve after an anterior transposition surgery commonly performed to manage patients with cubical tunnel syndrome - form of ulnar nerve entrapment. Unlikely ulnar nerve is affected without This surgery.
Elbow joint ligaments
Radial collateral - lateral epicondyle to the annular ligament deep to common extensor tendon.
Annular ligament of radius - anterior and posterior margins of the radial notch of the ulna on both ends forming an articular surface surrounding the head and neck of the radius (wraps round)
Ulnar collateral/medial collateral - thick triangular band, two sections anterior and posterior united by thinner intermediate portion. Anterior portion runs obliquely forward attached to anterior medial epicondyle to the olecranon. Intermediate fibres attach from medial epicondyle to blend with transverse band across notch between olecranon and coronoid process.
Sacciform recess of synovial membrane - not ligament but membrane of distal radioulnar joint is extremely loose and extends upwards as a sacciform recess between radius and ulna.
Elbow collateral ligament functions
Posterior portion of ulnar collateral ligament is taught in maximal flexion
Anterior portion contains three functional fibre bundles - taught in maximal extension, taught in intermediate positions and last is always taught and serves as a guiding bundle.
Elbow oblique cord
Ligament between ulnar and radius in lower arm near elbow. Takes form of small flattened band extending down and laterally from lateral side of the ulnar tuberosity at base of coronoid process to the radius a little below the radial tuberosity. Fibres run in opposite direction to those of the interosseous membrane of the forearm.
Pro and supination mechanisms
Pair of unique movements only performed by the forearm and hands
Pronation - pronator teres and pronator quadratus drive this by pulling the radius and rotating it at elbow and wrist around the ulna. Distal end rotates around ulna from lateral to medial sides turning the hand 180 degrees
Supination - driven by biceps brachii pulling radius distal end from medial to lateral turning the palm to face outwards.
Cubital tunnel and ulnar nerve passage and compression
Formed by medial epicondyle anteriorly and medial edge of trochlea, olecranon and ulnar collateral ligament laterally and cubital gunnel retinaculum (aka arcuate ligament/Osborne band) posteriorly as the roof.
Ulnar nerve passes through this and has many possible paths of compression - arcade of struthers, medial intermiscular septum, epitrochleoanconeus muscle and Osborn’s ligament all of which it passes under therefore any inflammation or tightening will compress the nerve resulting in weaknesses such as Wartenburgs syndrome where the little finger is involuntarily abducted by extensor digiti minimi.
Trapezius
Broad flat and triangular
Attaches from skull, nuchal ligament and spinous processes of c7-t12
Inserts to the clavicle, acromion and scapula spine
Innervation - motor from accessory nerve and proprioceptor fibres from c3 and 4 spinal nerves
Upper fibres elevate and rotate scapula during arm abduction
Middle fibres retract scapula
Lower fibres pull scapula inferiorly
Latissimus dorsi
Origin- lower back spinous process of t6-12, iliac crest, thoracolumbar fascia and inferior three ribs
Fibres converge into tendon inserting into intertubercular sulcus of humerus
Innervation from thoracodorsal nerve
Extends, adducts and medically rotates upper limb
Levator scapulae
Origin - transverse processes of c1-4
Inserts to medial boarder of scapula
Innervation from dorsal scapula nerve
Elevates scapula
Rhomboids
Major - Origin from spinous processes of t2-5 Inserts on medial boarder of scapula between spine of scapula and inferior angle innervation dorsal scapula nerve Retracts and rotates scapula Minor - Origin spinous processes of c7-t1 Inserts on medial boarder of scapula at level of scapula spine Innervation dorsal scapula nerve Retracts and rotates scapula
Extrinsic superficial muscles of the back
Latissimus dorsi, trapezius, rhomboids and levator scapulae
Act to move the shoulder
Extrinsic intermediate muscles of the back
Serratus posterior (superior and inferior) muscles Act to move thoracic cage
Serratus posterior muscles
Deep to the rhomboids
Serratus posterior is two thin, intermediate back muscles which lie above the intrinsic back musculature. They are:
The serratus posterior superior muscle
The serratus posterior inferior muscle
Superior - spinous processes and supraspinous ligaments of c7-t2
Insertion into posterior aspect of ribs 2-5.
Assists forced inspiration elevating ribs
Supplied by anterior primary rami (t2-5) intercostal nerves.
Inferior - spinous processes and supraspinous ligaments of t11-L2
Inserts in posterior aspect of ribs 9-12
Assists forced expiration depressing spine
Supplied by primary rami t9-12 intercostal nerves
Intrinsic superficial muscles of back
Known as spinotransversales
Muscles - splenius capitis and splenius cervicis
Act to stabilise or move the vertebral column
Splenius capitis muscles
Origin from lower aspect of ligamentum nuchae and spinous processes of c7-t3/4
Insert to mastoid process and occipital bone of skull.
Innervated by posterior rami of spinal nerves c3 and 4
Function to rotates head to the same side
Splenius cervicis muscle
Origin from spinous processes of t3-6
Insert into transverse processes of c1-3/4
Innervated by posterior rami of lower cervical spinal nerves
Function to rotate head to same side
Intrinsic intermediate muscles of back
Iliocostalis, longissimus and spinalis known as the erector spinae.
All have a common tendinous origin arising from the lumbar and lower thoracic vertebrae, sacrum, posterior aspect of iliac crest and sacroiliac and supraspinous ligaments.
Iliocostalis - inserts into costal angle of the ribs and the cervical transverse processes.
Innervated by posterior rami of spinal nerves, is the most lateral of the muscles and acts to laterally flex the vertebral column. Acts bilaterally to extend the vertebral column and head.
Longissimus - between the other two muscles. Inserts into the lower ribs and transverse processes of c2-t12 and mastoid processes of the skull. Innervated by posterior rami of spinal nerves and acts unilaterally to laterally flex vertebral column and acts bilaterally to extend the vertebral column and head.
Spinalis - most medial of the muscle inserts to spinous processes of c2, t1-8 and occipital bone of skull. Innervated by posterior rami of spinal nerves. Acts unilaterally to laterally flex the vertebral column and acts bilaterally to extend the vertebral column and head.
Deep instrinsic muscles of back
Known as transversospinales
Short muscles associated with transverse and spinous processes of the vertebral column
Three major muscles - semispinalis, multifidus and rotatores.
Semispinalis
Most superficial of the deep intrinsic muscles of the back.
Originated from transverse processes c4-t10 inserting to c2-t4 and occipital bone
Innervation from posterior rami of spinal nerves acts to extend and contralaterally rotate head and vertebral column
Multifidus
Located underneath semispinalis and is best developed in the lumbar area
Has broad origin from sacrum, posterior iliac spine, common tendinous origin of erector spinae, mamillary processes of t1-3 and articular processes of c4-7.
Insert to spinous processes of vertebrae
Innervated by posterior rami of spinal nerves acts to stabilise the vertebral column
Rotatores muscle
Most prominent in thoracic region
Origin from vertebral transverse processes
Inserts into lamina and spinous processes of immediately superior vertebrae
Posterior rami of spinal nerves innervate
Acts to stabilise the vertebral column and has proprioceptive function.
Minor deep intrinsic muscles of back
Interspinales - spans between adjacent spinous processes and acts to stabilise vertebral column
Intertransversari - spans between adjacent transverse processes acts to stabilise vertebral column
Levatores Costarum - origin from c7-t11 insertion to rib immediately below acts to elevate ribs.
Scoliosis
Abnormal lateral curvature of the spine
Most common in thoracic spine region
Most often starts in children ages 10-15
Infantile idiopathic scoliosis - develops at ages less than 3
Juvenile idiopathic - between 3-10 years
Adolescent idiopathic - between 10-18 years
More than 80% of people with scoliosis is idiopathic and majority of those are adolescent girls.
Doesn’t normally improve without treatment but treatment isn’t always needed if mild
Can have back pain and look lopsided - shoulder not aligned etc
Can cause severe breathing problems
Can be treated with back brace sometimes surgery needed and treatment to manage the pain
Decreases chest wall compliance directly and lung compliance indirectly due to progressive atelectasis (Lung collapse) and air trapping significantly increasing the work of breathing. Any associated respiratory muscle weakness may lead to respiratory failure if severe enough
The cobb angle is a measurement of the degree of scoliosis. An X ray of the patient is taken, and an angle between the top and bottom vertebrae involved in the condition (not the straight ones) is drawn. Perpendicular lines are then drawn from each line and the intersection of these is the Cobb angle. (Top bit of intersection)
Must be angle of 10degrees or more for scoliosis.
Kyphosis
Excessive outward curvature of spine causing back hunching
A curve of more than 45 degrees (nhs)
Can cause back pain, stiffness, spine tenderness and tiredness. Can also be asymptommatic.
Particularly problematic in adults due to having to compensate for abnormality.
May lead to difficulty breathing and eating if severe enough
Caused by poor posture, abnormally shaped vertebrae (Scheuermanns kyphosis), congenital kyphosis from abnormal development in womb ie vertebrae fusing together, or age can naturally increase curvature. Can also develop as result of spinal injury.
Children can be treated with bracing etc or surgery rarely.
Lordosis
Excessive inward curvature of the spine
Can be caused by spondylolisthesis (spinal condition where lower vertebrae slip forward onto bone below), osteoporosis, obesity etc.
Types : lordosis of lumbar spine is most common.
Cervical lordosis the neck is a very wide C or runs outward (reverse cervical lordosis).
Only requires treatment if severe
Juvenile lordosis often occurs without cause when muscles in children’s hips are weak or tightened. Typically corrects itself with age
Vertebral body weight bearing
Anterior body withstands 75% weight and posterior 25% of longitudinal load
They’re shall of cortical bone surrounding trabecular framework
Solid (cortical) bone suitable for maintaining static load as dynamic load would disrupt their crystalline structure and fracture along cleavage planes.
Anterior triangle made up of mainly trabeculae and explains why you get wedge shaped fractures. 600kg would crush anterior part of healthy vertebrae while 800kg would crush the whole body.
Ability to withstand forces and load is dependent on bone mass with peaks in mid thirties and then slowly declines
In women this decline accelerates at a higher rate after menopause for about 10 years after
Trabecular bone mass declines more rapidly than cortical bone and alters loading properties of vertebral body
Trabecular pattern pedicle
Pedicles are the only connection between posterior elements and body and all forces sustained by posterior elements are ultimately channelled towards the pedicles which transmit them to body
Designed to sustain force and trabecular pattern makes them very strong
Lamina force transmittence
Contain articular facets which upper cervical region support forces acting between vertebral column and the head
From the third cervical vertebral forces are transmitted from lamina to body through the pedicles and therefore must be strong to withstand bending forces
Articular process and force
Paired superior and inferior processes project from laminae- faces of which form small synovial joints
These determine range of movements possible between vertebrae as well as shape of articulation, position of ligaments and muscles as it’s a synovial joint.
Major difference between vertebral column and other synovial joints is most forces generated go through body of vertebrae and not synovial joint itself with the exception of first two joints at base of skull. Second difference is position of ligaments which aren’t all intimate with vertebral articular joints as they are in other parts of the body.
Lumbar region and force
Synovial joints designed to block axial rotation protecting the intervertebral discs from excessive tension
Anterior sliding also prevented as orientation of joints acts as a block
Lumbrosacral joint
In upright position sacrum is inclined 50 degrees forward
Lumbar vertebra prevented from slipping forward and downward on the sacrum by:
IVD wedged at 16 degree lessens angle on superior surface of sacrum
Superior articular facet of sacrum face posteriorly at an angle between 45-90 degrees
Hooking inferior articular facet of L5 into sacrum preventing it from sliding forward and in addition the transverse process of L5 are secured by iliolumbar ligaments
Sacroiliac joint
Synovial but not designed for large range of movement limited to about 2 degrees
No muscles to provide movement
Acts as stress relieving joint in pelvic girdle
During gait pelvis is subject to twisting forces therefore if this joint was solid it would crack
Surrounded by strong ligaments that help absorb forces applied during gait
Secondary cartilaginous joints of vertebral column
Synovial joints would be unable to function without some movement of vertebral bodies
To sustain the forces and prevent sliding a strong layer of deformable material is in between each vertebra
Intervertebral discs
Has three components - nucleus pulposus, annulus fibrosus and end plates
Nucleus pulposus of IVD anatomy
In young healthy adults is semi fluid mass 70-90% water with few cartilage cells 1-5% total volume
Irregularly arranged collagen fibres mostly type II but up to 10 different types present dispersed in ground substance containing proteoglycans
Aggrecan is most abundant proteoglycan and may attach to hyaluronic acid to form even larger molecule
No blood vessels or nerves
May be deformed but volume can’t be compressed
When force is applied it reduces height and expands radically putting pressure on annulus which stretches lamellae outward resisted by collagen. Nucleus also exerts pressure on end plates which may bulge
Disc has resilience as once pressure is removed is restored to original position
Annulus fibrosus IVD anatomy
In the lumbar region consists of highly ordered collagen type I fibres mostly arranged in concentric rings anteriorly thicker
40% rings incomplete
Proteoglycans also present and glycoproteins
Is turgid and relatively stiff and when healthy will resist buckling and bear weight
After prolonged weight bearing will begin to deform - collagen lamellae will buckle and fluid will be squeezed out
Negative charge on GAGS prevents complete collapse of integrity of disc
Loss of proteoglycans is first indication of disc degeneration
Alterations In direction of fibres in lamellae are integral to capacity of disc to resist twisting
Differences in IVD composition in vertebrae
Most studies look into lumbar region. Some evidence indicate differences in cervical discs with nucleus pulposus forming only 25% in cervical but 50% in lumbar. Also differences I arrangement of annulus. Few studies on thoracic region suggest its similar to cervical.
Vertebral end plates
0.6-1 mm thick covering area of pulposus but not all of annulus. (Peripheral of annulus inserted into bone)
Collagen fibres in hyaline cartilage arranged horizontally at centre to withstand pressure form nucleus during axial compression
Vertebral end plate is weak link in compression as needs to be thin to pass nutrients to discs but pressure from nucleus can cause it to bulge into vertebra
Cranial end plate is weaker than caudial
IVD function
Fluid loss and gain is exponential
If forced added and removed in quick succession fluid gain may not return to original state
If force is maintained for long period of time disc might not recover to initially thickness
Pressure - muscle tension increases compressive force on disc. Higher forces generated during movement
To support joint and prevent unwanted movements several ligaments surround vertebral column
Anterior longitudinal ligament - slack in forward flexion stretch in extension.
Posterior longitudinal ligament - reverse.
Range of movement in vertebral column
Range of movement between two adjacent V is limited due to limited range of IVD deformation and shape of articulation, associated ligaments etc.
While individual movements are small, summation of all these produce wide range of movement
During movement is subject to tension, Compression, bending, torsion and shearing forces
Flexion and extension of atlanto occipital joint averages 15 degrees but only small degree of lateral flexion always accompanied by rotation.
Lateral flexion usually coupled with contralateral rotation in upper lumbar region but with ipsilateral rotation at L5/S1
Many movements of vertebral column are coupled but there’s a high degree of variability between individuals.
Loading forces acting on vertebral column
Axial compression occurs due to force of gravity and action of ligaments and muscles
When subjected to constant load disk will exhibit creep which causes fluid to be expressed from the disc. Removal of load allows disc to return to normal condition
Annulus and trabecular bone can undergo greater amounts of deformation before failure than end plate or cortical bone Can
Vertebral column muscles
Divided into trunk and neck muscles
Posterior muscles further divide into extrinsic, superficial and deep and intrinsic superficial and deep. Also anterior muscles which lie in front of vertebral column and in front of viscera in the neck, thorax and abdomen.
Trunk muscles - consist of posterior vertebral muscles divided into extrinsic (attaches to upper limb), superficial intrinsic and deep intrinsic. In front of vertebrae are psoas and quadratus lumborum muscles and also important group forming anterior abdominal wall-transversus abdominis, internal and external obliques.
Posterior muscles - tightness of erector spinae often present in back pain. In normal standing there’s little activity in muscle. Constant activity to counteract forward sway is increased when head or upper limbs move forward. Contraction of erector spinae increases intracranial pressure.
Transversospinalis muscles act as postural muscles stabilising vertebrae and controlling movement.
Quadratus lumborum acts as respiration accessory fixing 12th rib and stabilising origin of diaphragm. Flexes trunk ipsilaterally and aided by oblique muscles.
Psoas major when femur foxed and hip stabilises contracts leading to ipsilateral lateral flexion and contralateral rotation. Creates compressive force on IVD and increases intradiscal pressure. Flexes VC relative to pelvis accentuating lumbar lordosis.
Thoracolumbar fascia also surround muscles
Fascia of vertebral column - thoracolumbar fascia
Thoracolumbar, fascia lata and abdominal fascial systems play important role in stability and mobility
Thoracolumbar covers back muscles over sacral region extending through thoracic region to nuchal line. Complex fascia has several layer. Many fibres of superficial layer derived from aponeurosis of lat dorsi and blend with fascia of gluteus max. Also continuous with contralateral lat dorsi. Muscles are mechanically linked and play role in increasing fascia tension in turn stabilising lumbosacral and sacroiliac regions. Deep fibres attach to interspinius ligaments, posterior iliac spine, crest and sacroiliac ligament. Laterally two layers blend together and are directly linked to internal oblique and transversus abdominis muscles.
Functions- stabilise pelvis. Muscles in contact with (transversus abdominis, internal oblique, glut max, lat dorsi) have a pulling effect on fascia.
Muscles encased by it (erector spinae, multifidus) have pushing effect.
Movement of limbs and back also increase tension
May also aid alignment of vertebral column by reducing shear forces. May prevent buckling of ligamentum flavum.
Abdominal muscles and vertebrae movements
Bilateral contraction increases intra abdominal pressure but doesn’t result in trunk flexion. Aided by contraction of internal oblique
Play important part in expulsion efforts increasing pressure on bladder, rectum, stomach and in childbirth.
Intra abdominal pressure also increased during lifting accompanied by closing glottis and contraction of pelvic floor muscles. Axial compression of discs reduced and therefore useful for protecting vertebral column in short term when lifting heavy load
Spinal flexion
Increased activity in erector spinae muscles
Gravity
Produces movement but it’s rate is controlled by erector spinae and multifidus contracting eccentrically.
At 90degree flexion erector spinae activity ceases
Tension in facet joints and posterior ligaments braces the spine
Activity in anterior and lateral muscles occurs only when working against gravity
Spinal rotation
Oblique muscles main rotators
External oblique from one side works synergistically with opposite side
Fibres of muscle form a girdle around abdomen
Slant of muscle determines hollow of waist
Higher the tone of muscle the greater the hollow
Mathematical explanation is a hyperbolic curve, curve consists of series of straight lines
Palpating joints of elbow
Palpated inside triangle formed by bony prominences of lateral epicondyle, radial head and the olecranon. This palpitation reveals even minor effusions or mild synovitis. Puncture for joint aspiration performed in this triangle
Similarly an arthroscopy portal may be placed there (posterolateral portal)
Anatomical landmarks - lateral aspect of elbow, radial head palpated with thumb while other hand pro and supinates patients forearm
Elbow injuries/problems
Bursitis - bursa inflammation
Medial joint pain - Valgus injuries often from throwing action
Epicondylitis - golfers elbow (medial) - common in men 20-50 years, pain in medial elbow may radiate to inner forearm. Worsens when making goats or shaking hands. Treated by analgesia NSAIDS, steroid injection, physio. tennis elbow (lateral) - degeneration of tendon fibres over lateral epicondyle involved in wrist extension. Severe burning pain on outer elbow. Worsens when gripping or lifting and with direct pressure on lateral epicondyle. May radiate down forearm.
Fractures and dislocations - ulnar, radial And humeral. Fall backwards onto extended arm
Pulled elbow - wrestlers and children most commonly.
Nerve and vascular entrapments - ulnar, median, radial nerves and brachial artery
Elbow dislocations
Described according to direction of displacement of ulna relative to humerus
posterior has many variations -
Posterolateral, posteromedial, lateral and medial.
Anterior is very rare
Usually stable once reduced if bony stability is good.
Complex injuries - radial head fractures cause instability, MCL always damaged to varying degrees. May have fracture of medial epicondyle.
Coronoid fractures: fall into flexed elbow, due to avulsion by brachialis when elbow is hyperextended.
Terrible triad - radial head, coronoid and MCL often damaged together.
Median and ulnar nerve injuries in 20% cases.
In simple cases both collateral ligaments usually torn but MCL can survive. Variable amount of muscle origin lost. Greater instability with more muscle injury.
Pulled elbow
Usually 18 months to 4 years most common Partial dislocation of elbow History of pulling arm, won’t use arm Not very distressed Any movement causes a clicking noise
Elbow fractures
Humeral - supracondylar, hyperextension of arm on outstretched hand/direct blow to humerus. Or flexion type from direct force to tip of elbow.
Ulnar - coronoid, olecranon: impact or hyperextension
Radial - axial loading of radius from fall or dislocation. Pain on outside elbow, swelling, unable to fully flex or extend, pain with pro and supination.
Intercondylar/condylar/epicondylar type - medial epicondyle commonly avulsed during elbow dislocation. Nearly always associated with another dislocation.
Capitular fractures - transmission of force through radial head when landing on hand with elbow flexed or directly onto fully flexed elbow.
Olecranon and coronoid fractures - direct impact on posterior surface of elbow or indirect falls into hand. Often associated with ulnar nerve injury (10%)
Radial head fractures - fall onto outstretched hand
Supracondylar fractures of elbow complications
Vascular - brachial artery damaged, Volkmanns ischaemic contracture (permanent flexion of hand at wrist - claw hand from extension of MCP and flexion of IPJ), median nerve palsy.
Treatment - manipulation if displaced, arterial obstruction fixed
Long term arm plaster
Complications of elbow injuries
Neurovascular injury - ulnar, median, radial nerves and brachial artery (radial least common)
Osteoarthritis - osteophytes formation. Primary commonly seen in males 50-60 years repetitive elbow use. Secondary most commonly from post trauma. Catching or locking loose bodies in 20% cases. Terminal impingement pain from olecranon osteophytes possible. Loss of motion usually extension. Ulnar nerve irritation common.
Rheumatoid arthritis
Synostosis union or fusion of bones by growth of bony substance - congenital or acquired/post traumatic
Kidneys function
Maintaining overall fluid balance
Regulating and filtering minerals from blood
Filtering waste materials from food, medications and toxic substances
Creating hormones that help produce red blood cells, promote bone health and regulate blood pressure
Describe the kidneys
Bean shaped organs retroperitoneal at level t12-l3
Left higher than right due to liver on right hand side
Renal capsule surrounded by peri-renal fat, then renal fascia and pararenal fat.
Supplied by renal arteries from aorta at L1 just underneath superior mesenteric artery branching.
Renal arteries become interlobar either side of pyramids, then interlobular then entering the cortex become afferent arterioles forming capillary nertwork ending in efferent arterioles forming peritubular network around nephrons then vasorecta supplying inner 1/3 of cortex and the medulla.
Renal vein on the left is longer due to crossing the aorta and artery on the right is longer due to crossing the IVC.
Lymph drains into paraortic lymph nodes.
Drained by renal veins (lies anterior to artery in hilum).
Cortex contains vessels and nephrons - take in and filter blood for waste metabolites. Each kidney has roughly 1 million nephrons. Blood enters renal corpuscle (aka malpighigan body) containing the glomerulus and bowmans capsule. Then passes through into renal tubules - PCT, loop of henle and DCT absorbing water, sodium and glucose (PCT), K, Cl and Na (LoH), Na, K and acid (DCT) back into blood. Passes into collecting tubules in the medulla (LoH also dips into medulla) drains into renal pyramids containing strings of nephrons tubules finally moves into renal pelvis by minor and major calyces. Small cup shaped spaces that collect fluid before it moves to the bladder. Also where extra fluid becomes urine. Exits via the ureter through the hilum of the kidney into the bladder.
Ureter narrowings
Pelvi-ureteric junction - renal pelvis and ureter
Pelvic brim where ureter passes over iliac vessels
Vesicoureteric junction where ureter enters bladder
These can be involved in kidney stones pain as they’re the narrowest points and are where stones will most likely get stuck.
Causes sharp cramp in back, side or lower abdomen.
Ureter blood supply and innervation
Arterial blood supply varies along course
Upper part closest to kidneys - renal arteries
Middle part from common iliac arteries direct branches from abdominal aorta and gonadal arteries (testicular/ovarian arteries)
Lower part closest to bladder - internal iliac arteries as well as superior vesicle artery, uterine artery in women, middle rectal artery, vaginal artery in women and inferior vesicle artery in men only.
Nerve supply ureteric plexus. Primary sensation from T12-L2.
Can you cut the left renal vein without serious consequence
Yes as the left renal vein crosses the aorta so it is often necessary in surgery to sacrifice it luckily there are collateral drainage vessels from inferior adrenal veins that compensate for this.
Retroperitoneal organs
SAD PUCKER Suprarenal glands Aorta/IVC Duodenum after 1st section. Pancreas Ureters Colon (ascending and descending) Kidneys Oesophagus
Kidney topographical anatomy
Anterior (left) - spleen, stomach, splenic flexure, pancreas, jejunum, adrenal glands
Posterior (left and right)- psoas, quadratus lumborum, 11/12 ribs
Anterior (right)- liver, hepatic flexure, duodenum, adrenal glands
Mechanical damage to lumbar spine
Impairment of structure unable to withstand forces generated by normal activities
For fatigue failure to occur the microscopic damage must accumulate faster than the adaptive remodelling response can cope with
Repetitive mechanical loading and micro damage resulting from it can initiate adaptive remodelling response so that the spine can become stronger and more able to withstand load
Bone remodels in response to increase load as does muscle
Both will also adapt to a decrease in load. The metabolism and age of tissue dictate the rate of remodelling.
Compressive Load on vertebral column
Compressive load is resisted mostly by anterior column and IVD 75-85% while facets joints and laminae give rise to remainder of resistance.
Narrowing of IVD leads to increase in facet load. If narrowing is severe up to 70% load may be transmitted through facet joints.
In lumbar spine compressive strength of vertebrae ranges between 2-14kN depending on age, sex and body mass. Trabecular pattern of bone reenforces body but makes anterior portion more vulnerable to compression.
Compression of vertebra while In full flexion may effect either disc or vertebra.
