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Biomechanics Exam 1
Lectures 1,2,3
| Question | Answer |
|---|---|
| What does the vertebrae articulate with? | with each other, with the skull, with the pelvis |
| What are the levers? | vertebrae spinous process |
| What are the pivots? | IVD and facets |
| What are the passive restraints? | ligaments |
| What are the activations? | muscles |
| What are the functions of the spine? | Transfers the weight of the head and trunk to the pelvis, allows sufficient physiologic motions between three body parts, protects the spinal cord |
| An attempt to combine anatomy and pysiology by applying mechanis and biology | What is biomechanics? |
| The study of forces and their effects | What is mechanics? |
| Which branch of mechanics deals with equilibrium of the bodies at rest or in motion with zero acceleration? | statics |
| What branch of mechanics deals with the study of loads and interacting bodies? | dynamics |
| What branch of dynamics focuses on the geometry of motion? | Kinematics |
| What branch of dynamics deals with the relations between forces? | Kinetics |
| What is the difference between the vertebrae and spine? | The vertebral column refers to the osseoligamentous structures with curcatures in the sagittal plance, whereas the spine refers to the musculoskeletal and neurovascular elements |
| What causes kyphosis curves? | Primary curves caused by posterior deviations and wedge shaped bodies |
| What causes lordotic curves? | Anterior deviations and wedge shaped discs |
| What is the function of the curves of the spine? | Increase flexibility and increase shock absorption |
| How good are ligaments at stabilizing the spine? | Restricts motion but also allows motion. Good at stabilizing at the end range only. |
| What are the mechanical stabilizers of the spine? | Neuromuscular control system |
| What makes up 20-33% of the spine and what are its parts? | IVD with nucleus pulposus, annulus fibrosis, and cartilaginous end plate |
| Greater ratio= ______ Where is the ration the greatest? | Mobility; cervicals and lumbars |
| What makes up the whole disc? | Proteoglycans, Water, Collagen |
| What does the proteoglycan/collagen ration determine? Where is the highest? | Amount of water in the disc; greates in nucleus |
| What type of collagen is found in the annulus? | Type I (helicoid fibers) tension resisting tissues |
| What type of collagen is found in nucleus? | Type II copression resisting tissues |
| How are the concentric bands positioned in the disc? | 30 degrees to the disc plane and 120 degrees to adjacent bands |
| Where does the annulus attach peripherally? centrally? | Peripherally to ligamentous sharpey's fibers and centrally to the cartilaginous end plate |
| What makes up the cartilaginous end plate and what is its function? | Hyaline cartilage; separates nucleus and annulus from vertebrae |
| Where does disc ageing first occur? | nucleus |
| What are the cellular and chemical changes that occur in disc ageing? | Cells produce less proteoglycan (less water). Brown pigmentation occurs due to non-reducible collagen cross-links and injury to brittle discs |
| What happens to discs after 25 YOA? | become avascular and receive nutrients and waste exchange through imbibition |
| How does ageing of the end plates differ from nucleus? | Accompanying calcification may compromise nutrition to the nucleus |
| What differences exist in the ageing of the annulus? | Chemical changes are less pronounced; collagen content increases and becomes stiffer |
| What are the funtional consequences of disc ageing in the nucleus? | Nucleus becomes dry, stiff, fibrous, and volume decreases |
| What are the consequences of disc ageing in the annulus? | Annulus becomes weaker (stiffer), takes on more compressive load, but does noit lose disc height |
| What are some common trends where disc degeneration is seen? | More common in men than women. Usually occurs after 20 YOA with the maximum at middle age. Most evident in annulus and end plate. |
| T/F Ageing and degeneration can be used interchangeably. | False. NOT inevitable consequence of ageing |
| What are some structural changes that can occur from disc degeneration? | Inward buckling, Radial bulging, Reduced disc height, Endplate defects, Vertical bulging of endplates into bodies, Radial tears, Circumferential tears, Prolapse |
| List the three types of anular tears. | Concentric clefts, Rim lesions, Radial fissure |
| What are concentric clefts? | Anular tears that occur between adjacent lamellae and represent delamination of anulus. Very common. |
| What are rim lesions and how common are they? | Circumferential avulsions of the periphery with 2X more common anteriorly (typically antero-lateral margin) |
| What are radial fissures? | Radial disruption of the lamellae from the inner anulus to outer lamellae |
| What is a special case of radial fissure? | Disc prolapse which allows escape of nucleus material. |
| What are some cellular changes that occur in disc degeneration? | Cell clustering with concentric rings occuring around some cells, blood vessels and nerves grow toward the center due to loss of hydrostatic pressure,a dn matrix degrading enzymes increase. |
| What structural changes occur adjacent to the degenerated disc? | Z-joints degenerate and osteophytes develop around body margins |
| What functional changes occur in degeneration? | Reduced ROM in bending and increased ROM in rotation. |
| What are the Kirkaldy-Willis degeneration stages? What stage is chiropractic best in? | Normal (0), Dysfunction (1), Unstable (2), Stabilization (3) |
| Describe the dysfunction stage of degeneration. | small degree of joint subluxation with abnormal motion. (most patients in this stage) |
| Describe the unstable stage of degeneration. | Observable and audible catch, sway, or shift with increased motion. Spodylolisthesis on motion. |
| Describe the stabilization stage of degeneration. | LBP decreasing severity, stiffness and reduced movement, degenerative scoliosis, loss of disc height, small foramina, osteophytes |
| T/F Disc prolapse and herniation can be used interchangeably. | True |
| T/F Prolapse is particularly common in men and lumbars. | True |
| T/F Prolapse is an end-stage degeneration. | False |
| What are the three types of prolapse? | Protrusion, Extrusion, Sequestration |
| T/F Protrusion represents disc bulging. | True |
| What type of prolapse occurs when it is no longer attached to the nucleus? | Sequestration |
| What type of prolapse can be refered to as incomplete prolapse? | Extrusion |
| T/F No deformation occurs in elasticity. | True |
| What is viscoelasticity? | Property of of a material to return to its original form following the removal of the deforming load with some degree of stickiness |
| What type of loading rate occurs with physiologic loads? traumatic? | Slow rate with physiologuc loads, Fast rate with traumatic loads |
| What does a slow load curve represent? | More flexible, more deformation |
| What does a fast load curve represent? | More resistance, less deformation |
| What is the difference between compression and tension? | Compression is the normal force that tends to push together material fibers whereas tension tends to elongate (pull apart) fibers. |
| What was the result of the Virgin study on compression and herniation. | No herniation of the nucleus pulposus even with a longitudinal incision at the posterolateral annulus (most common site) |
| How was the Brown, Hanson, & Yorra study different from the Virgin study? | They used compressed functional spinal units and although no herniation occured, vertebral endplates were fractured. |
| T/F The Farfan study concluded that degenerative discs were weaker in compression that non-degenerated. | False. they were stronger |
| What is the most common site of herniation? | Posterolateral |
| According to the Brown. Hanson, & Yorra study, where is the most tensile strength? Least? | Most strength and anterior and posterior ends. Least strength at nucleus and lateral ends. |
| According to Galante, what angles have the greatest tensile strength? | 30 degrees to the disc plane with 3X more strength than horizontally |
| What is stiffness? | A measure of resistance offered to external loads by a structure as it deforms. |
| What does anistropic refer to? | The mechanical properties of the disc vary with different spatial orientations. (same force applied with differences in distance moved) |
| How does stiffness relate to compression and tension? | Less stiffness in tension than in compression. |
| According to Galante, what angle represents the greatest stiffness? | 15 degrees to disc plane |
| When did herniation occur in Farfan's study? Why was this not significant? | 15 degrees of bending. Posterior elements of the vertebrae were removed which is not likely in humans. |
| T/F Bulge is always on the concave side of the disc. | True |
| T/F Denucleation decrease disc bulging. | False |
| What is shear stress? | The intensity of force parallel to the surface on which it acts. |
| Wat is a relatively rare cause of anular tears? | Shear stress |
| What is torsion? | A type of load applied by a couple of forces about the long axis of a structure. |
| Where does torsion loading produce shear stress? highest? lowest? | 90 degrees to the axis of torsion with the highest at the periphery and lowest at the center |
| Where does torsion cause compression stress? | 45 degrees to the axis of torsion in the direction opposite the applied force |
| Where does torsion produce tension stress? | 45 degrees to the axis of torsion in the direction of the applied force. |
| What resulted from Farfan's study on torsion as the major causing load of herniation? | 25% higher torsion in a normal disc than degenerated, larger disc produces a higher torsional strength, average herniation at 15 degrees (not likely) |
| What did Adams & Hutton study represent? | Herniation occurred when a sudden compressive force applied in hyperflexion and lateral bending. |
| Why was the Adam & Hutton study flawed? | Most herniation/prolapse patients do not present with a precipitating traumatic event 9sudden compressive force). |
| Where did prolapse occur in the Adam & Hutton study? | convex side |
| What is creep? | A viscoelastic material deforms with time when it is subjected to a constant suddenly applied load. (shock absorption) |
| What is the difference in creep of a normal and degenerated disc? | Normal discs creep more slowly. Degenerated discs are less viscoelastic and creep more quickly. |
| What is hysteresis? | A phenomenom associated with energy loss exhibited by viscoelastic materials when they are subjected to loading and unloading cycles. |
| How does hystereis vary with load? | Higher load = Greater hysteresis |
| How does hysteresis vary with age of the disc? | Large hysteresis = very young disc, Smallest hysteresis = middle aged disc |
| How does hysteresis vary with repetition? | Second loading = decreased hysteresis |
| What is fatigue? | The process of the growth of cracks in structures subjected to repetitive load cycles with loads less than failure load. |
| What is fatigue failure? | When a fatigue crack reaches a certain size, the stress in the rest of the structure becomes so high that the structure fails. |
| Why was Brown's study on fatigue failure insignificant? | Represented signs of failure after 200 cycles and complete failure after 1000 cycles, however done in vitro when in reality repair/regeneration occur. |
| What is the take home message for disc herniation? | Compression WITH flexion/extension/letral bending WITH torsion and structural changes over time will cause herniation. |
Created by:
jtnguyen
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