bones Flashcards
what are the skeletal system functions
- support
- protect
- locomotion
- production of red blood cells
how does flat bones form
formed in direct ossification
how does long bones form
formed by indirect ossification but in a multi stage process
how does short and irregular bones form
formed by indirect ossification where a carilage moel is created greadually dissolved and then replaced by bone
ossification steps
1- caritalage model grows
2- cartilage replaced by bone
3- ossificationcomplete (articular cartilage remains)
what is the bone composition
- minerals
- collagen
- apatite
what is the bone structure function
1- tubular constrcution of compact bone in the shaft
2- light, cancellous bone at the ends
3- efficent arrangement of strusts and ties in cancellous bone to minimize weight
where are osteoblasts formed
formed in the periosteum tight band of organic material
- building blocks of bone
- need osteoblasts and osteoplasts to repair and make growth
compact bone
dense and located in the shaft of the long bone
spongy bone
forms the holes in the bone
- holes filled of liquid to help form red blood cells
flat bone
have spongy and compact bone
bone repair
1- Haematoma formation
2- Granular material formation
3- Hard callus formation
4- Remodelling
Haematoma formation
After fracture, blood vessels in the bone and periosteum are torn and begin to hemorrhage. As a result, a haematoma (mass of clotted blood) forms at the site. Bone cells (deprived of nutrients) begin to die and the tissue becomes inflamed, swollen and painful
Granular material formation
Within a few days soft granulation tissue (soft callus) forms. This is caused by: • invasion of capillaries • phagocytic cells clean up the debris • fibroblasts migrate into the site and fill the area with collagen • osteoblasts migrate into the site from the periosteum and begin bone formation
Hard callus formation
The activity of osteoblasts causes new trabecular (spongey) bone to form within the soft callus. Hard callus formation begins 3 - 4 weeks after injury and continues for 2 - 3 months.
Remodelling
Remodelling begins during the hard callus stage and continues for several months. The excess material around the fracture site is removed, as well as from within the medullary cavity. Compact bone is laid down to reform the shaft walls.
what happens with a persons bone composition as they age
The 1 : 2 ratio of organic material : inorganic salts provides our skeleton with certain mechanical characteristcs. At birth the ratio is 1:1 and when an elder the composition is 1:7
long bones have evolved in 2 ways
- support weight
- perform speedy movements
what is the bone composition
- 60-70% minerals: resists compression loads
- 30-40% collagen: stiff and strong: resist tension forces (forces that pull the bone apart and ground substances)
explaint the stess strain curve
- increase the load so there is a strain and it cracks once over the plastic stage
- take the load off it will go back to its orginal function
- load tissue beyond yeild point (elastic) into plastic and it will never go back to being the same
name the 4 type of forces
1- compression: longitudinal forces
2- tension: pulling the bone apart
3- shearing/bending: transverse forces
4- torsion: rotation
The two conflicting roles of weight support, yet
lightness in construction of bones are met by:
- tubular construction of compact bone in the shaft
- light, cancellous bone at the ends
- efficient arrangement of struts and ties in cancellous bone to minimize weight
compression strenght vaires dependant on what
- direction of force (anisotropic behaviour)
(greatest when parallel to shaft’s long axis) - age and sex
(greatest in mature males) - size, shape robustness and how much minerals is in the bone effects the width and strength
tension forces
- tensile strength is a poor away from the long axis of the bone
- fracture time (time in which the load is applied) (viscoelastic response) the point at which the bone fails
bone failure
- fracture under exstenuating forces
- fracture can occur through shearing and bending
- can fracture under repeated subthreshold stresses known as fatigue fractures or stress fractures
what is tibial pain/shin soreness caused by
- result in a condition called periostalsis (inflammation of the periosteum) caused by:
- tibial flexing
- linear pain
- other factors
tibial flexing
increased tibial flexing at region of smallest cross sectional area
- increased stimulation of persiosteum to build bone in this region
- increased microtrauma and periostisis
linear pain
- increase muscle activity
- increased metabolic activity
- increased blood flow
- increased muscle volume
- increased pressure of fascia
other factors that cause tibial flexing
- biomechanics of running
- shoe design
- training surfaces
- training methods
the trajectorial theory
wolff
- if you change the load of the bone it will change the external and internal structure of the bone depending on the load placed on the bone
Pauwels theory
- use an organ this leads to the organ getting bigger and more robust known as hypertrophy
- if you dont use the tissue or organ it willl respond by getting smaller known as atrophy
- apposition = reabsorption (tearing down and building of bone)
the Mechanostat theory
relating strain to bone mass
what does immobilisation do to muscles
- leads to atrophy which in turn leads to poorer mechanical properties in bone
3 effects of immobilisation in 3 situations
- ageing and activity
- immobilisation due to casting
- the effect of weightlessness
how to prevent natural decline in post menopasual woman in fracture threshold
- calcium
- exercise
- vitamin D
- HRT
- bisphoonates
what did kannus investigate
120 elite racquet sports girls looked at the difference in bone density between the prefferred arm and the non preferred arm. If they started tennis early the more effect the bone material density
what did Morris investiagate
divided school groups into a control group who did the normal PE activity. Group 2 did an extra 30min x 3 week x 10 months
- groups matched in weight, height, maturity and BMC
- after 10 months the experimental group had 2x the role of bone accurral
factors that affect bone loss later in life
- lack of calcium in the diet (calcium store)
- lack of estrogen or testosterone (post-menopausal women, anorexia nervosa, amenorrhoeic athletes and dancers)
- lack of exercise and weight bearing
Andersson & Nilsson (1979)
44 sports injuries involving the knee joint:
• Operated cases (with casting) 18% loss in bone mineral
• No operation cases only 10% loss in bone mineral
After 1 year of recovery, bone mineral had still not returned to normal, HOWEVER, weight bearing activity will shorten healing time
what are the different facture types
- open vs closed
- complete vs incomplete
- displaced vs non displaced
what are the mutiple facture types
- green stick
- partial
- communuted
- transverse
- oblique
- spinal
what are the type of fractures treated by reduction (the realignment of broken bone ends)
1- closed reduction (the bone ends are coaxed back into position manually)
2- open reduction (bone ends are secured together surgically with pins)
stress fractures
- not a complete break
- caused by sub-maximal repeated loading
Osgood Schlatter’s disease
Traction periostitis of the tibial tuberosity.
- periosteum trying to accomodate the large amount of physical activity
- inflammation of the periosteum and trys to lay down lots of bone
- tibial tuberosity grows big and angry
treatment of overuse injurys
Rest Ice Compression Elevation Refrerral to medical practitionar
Avulsion factures
Often the bony attachment of the muscle is torn away
rather than the muscle or tendon tearing.
- heales quicker
- common in kids
Epiphyseal factures
Can result in uneven growth if left untreated
dislocation
complete seperation of the joint
- hand, elbow, shoulders
sublaxation
partial seperation of the joint. Repair can result in reducing the joint.
meniscal tears
More common in older adults.
No nerve supply, but damage to surrounding tissues causes pain.
Medical treatment required.
catrilage injuries
- Osteochondritis dissecans
- Chrondromglacia patellae
Osteochondritis dissecans
- caused by violent activity
- occurs on the articular cartilage of the femoral condyle
- this lesion can float in the joint if it breaks free may calcify further and eventually lock the joint
Chrondromglacia patellae
- misallienment of the patella over to one side
- late adolescents and early adulthood
- damage to the articular surface of the patella
surgical technique ACI
Phase 1: cartilage retrieval
- lesion filled with fibrous cartilage
- cartlage gets taken from a non weight bearing part of the body and then gets sent to the leg
Phase 2: cell culture
Phase 3: 2nd surgery to implant chondrocyte impregnation patch into defect
Phase 4: Graduated rehab program to cause chondrocytes to migrate, differentiate, and hypertrophy
