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James W. DeVocht, DC, PhD

Module 4: The Mechanics of Spinal Manipulation (Herzog Chapter 4 – by Triano) Biomechanics (TECH 71613). James W. DeVocht, DC, PhD. Gross spinal abnormalities. Degenerative spondylosis Herniated nucleous pulposus Spinal instability/hypermobility Facet arthrosis Spinal stenosis

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James W. DeVocht, DC, PhD

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  1. Module 4: The Mechanics of Spinal Manipulation(Herzog Chapter 4 – by Triano)Biomechanics (TECH 71613) James W. DeVocht, DC, PhD

  2. Gross spinal abnormalities Degenerative spondylosis Herniated nucleous pulposus Spinal instability/hypermobility Facet arthrosis Spinal stenosis Scoliosis and deformity don’t always explain symptoms from Herzog Box 4-1 on page 93

  3. In order to understand a treatment paradigm, you need to understand its underlying assumptions Concepts vs. memorized steps Technician vs. doctor Herzog page 92

  4. Terms used to characterize spinal disorders Hypothetical Construct Subluxation Osteopathic leision (somatic dysfunction) Joint/segmental dysfuction Manipulable lesion Presenting Complaint Low back pain/lumbalgia Neck pain/cervicalgia Headache Radicular syndrome Pathoanantomy Facet syndrome Disc herniation Spondylosis Disrupted disc syndrome Spinal stenosis Myofascial syndrome from Herzog Table 4-1 on page 93

  5. Four Elements of the Subluxation (Palmer) Vertebral misalignment Narrowing of the IVF Nerve pressure Interference with nerve function Herzog page 94-5

  6. Speculations on the pathomechanics of the subluxation (Dishman and Lantz) Herzog Fig 4-1

  7. Stages of Contemporary Subluxation Complex Herzog Fig 4-2

  8. Segmental dysfunction Term used by practitioners of manual medicine Disturbance of internal function of vertebral unit Reversible impairment from trauma etc. Herzog page 95

  9. Terms related to segmental dysfunction concerning altered muscle tone & function: myotendinous: refers to cases of altered muscle tone accompanied by painful response to pressure myosis: noninflammatory degenerative condition located within the muscle belly attachment tendinosis: abnormalities affecting the myotendinous junction Herzog page 95

  10. Proposed reverberating cycle that perpetuates segmental dysfunction Irritation of nerve to muscle spindle  shortening of the spindle  increase tone of the muscle Sudden overstretching of muscle spindles is thought to reset them, restore normal tone, & break the cycle. 1 Etiologic Factor 2 Muscle or joint Pain receptor 5 3 Gamma fiber activation of muscle spindle Segmental dysfunction 4 Increased muscle tone Herzog Fig 4-4

  11. Somatic Dysfunction The term currently being used by osteopaths to refer to what they think of as a manipulable lesion Thought to be a modification of musculoskeletal function, of any freely moveable articulation, influencing vascular, lymphatic, and neural elements (Greenman) Still no single core hypothesis that can explain all the variations seen in clinical practice Herzog page 97

  12. Functional Spinal Unit (FSU): 2 adjacent vertebra, IVD, connecting ligaments and muscles Functional Spinal Region (FSR): multiple FSUs functionally connected to accomplish a task (varies according to the specific task being done) from Herzog Fig 4-5

  13. Range of Motion of FSUs C0/C1: has the most flexion/extension C1/C2: has the most axial rotation SI Joint: limited but complex motion (more sagittal than transverse) Herzog pages 99 -101

  14. Load Sharing Between Active & Passive Structures Illustrated by flexion/relaxation phenomenon Specific ligaments may compensate for ineffective muscular action Stretch is usually small fraction of failure Herzog page 103

  15. Variations to Normal Ligament Loads Degenerative changes (like disc narrowing) Usually large stature  increased size of vertebral elements and moment arms. Herzog page 103

  16. MechanicalEquilibrium (static or dynamic) of the body as a whole is like biological homeostasis of the living cell.This structural homeostasisis represented by transfer of loads without failure. Herzog Fig 4-15A

  17. Either excessive deformation or loss of continuity of one or more associated tissues constitutes mechanical failure degenerative spondylolisthesis spondylolytic spondylolisthesis Herzog Fig 4-16D Herzog Fig 4-16C

  18. Different modes of analysis which are used for different loading situations:1. Static2. Dynamic3. Quasistatic Herzog Fig 4-17

  19. Fatigue affects the manner in which loads are distributed among supporting structures and tissues. Herzog Fig 4-18

  20. Segmentation of Vertebral Load-Displacement Curves into Distinct RegionsSegment QualitiesRange of Motion A two-stage interval of FSU flexibility. The sum of the neutral and elastic zonesNeutral Zone A region of potential rest positions for the FSU. A neighborhood of the neutral position in which small loads cause relatively large displacementsElastic Zone The region of FSU resistance to physiological motion from Herzog Table 4-6 on page 109

  21. Intervals within the range of motion of one vertebra relative to another range of motion elastic zone resistance neutral zone graphic portrayal of data from Herzog Table 4-6 on page 109 angular displacement

  22. Experimental setup for measuring theeffects of pedicle screw internal fixation Herzog Fig 4-20

  23. Lateral shearing displacement- incremental loading of a segment- sequential transection of elements (anterior 50% of disc) Herzog Fig 4-19

  24. Central Sensitization: increased sensitivity of spinal cord neurons which may be caused by prolonged painful stimulation. Herzog page 112

  25. Conservative Medical Interventions Supporting Benefits from Manipulation (Chiropractic Adjustments)1.Analgesics 2. Nonsteroidal anti-inflammatories 3. Pain management injections Muscle trigger points Facet joints Costovertebral joints Sacroiliac joints Intradiscal steroid Direct nerve blocks Epidural steroids from Herzog Box 4-2 on page 113

  26. Effects of Prolonged Static PostureCreep deformation Stress relaxation Joint cartilage Pressure dehydration Matrix thinning Chronic irritation Connective tissue inflammation from Herzog Box 4-3 on page 113

  27. Effects of Immobilization onHuman Articular TissuesJoint capsule contracture Shortening ThickeningJoint stiffnessJoint painFibropatty joint infiltrationCartilage degeneration Fibrillation Erosion Intracartilaginous cystsIntraartiular capsule adhesionsMuscular atrophyDisuse osteoporosisDegenerative arthritis from Herzog Box 4-4 on page 113

  28. Injury mechanics and aging effects seem to progress in fairly well established patternsIndividual cases cannot be predicted accurately (variations in structure and behavior) Herzog page 114

  29. Factors Moderating Location & Extent of Injury Factors Elements1.Injury load Magnitude Direction of application Rate of application Site of application 2. Posture Mid-range of joint motion Symmetry of position End-range of joint motion 3. Muscular tension Preload activation Concurrent activity Post-load response 4. Tissue status Healthy, uninjured Recovering injury Degenerative from Herzog Table 4-7 on page 114

  30. Biomechanical Terms Injury thresholdHysteresisQuasistaticStaticStiffnessStressStrainUltimate strengthYield strength Angular velocityAngular accelerationAngular displacementCentral balance pointClinical injuryComplianceCreep deformityElastic limitFracture/breaking strength from Herzog Table 4-8 on page 116

  31. Hysteresis: energy lost to internal friction during a loading/unloading cycle Herzog Fig 4-24 Work: force times distance (area under the stress/strain curve for loading indicates work done) Releasing the load takes less force, therefore less energy has been released (area under the stress/strain curve for unloading) Hysteresis is represented by the area between the loading & unloading curves

  32. Mean Values for Neutral Zones(in degrees) Vertebral Flex/ Axial Lateral Segments Ext Rotation Bending C1-2 14.7 53.8 6.4 C2-3 6.8 6.7 9.0 C3-4 6.7 8.4 7.8 C4-5 7.6 9.6 7.5 C5-6 7.6 6.6 7.0 C6-7 6.6 6.2 6.7 from Herzog Table 4-9 on page 117

  33. Complete Stress/Strain Curve C D B A 0-A: toe region A-B: classical elastic region (slope is Young’s modulus of elasticity, or stiffness) B: elastic limit C: ultimate strength D: fracture/breaking strength adapted from Herzog Fig 4-26

  34. Static Creep Deformity/Relaxation Herzog Fig 4-27 Incremental increases in load during creep and recovery test (see slide 2-16) Incremental increases in deformation during stress-relaxation test (see slide 2-17)

  35. Dynamic Creep Deformity Cartilage thickness Herzog Fig 4-28 (modified) Each cycle of loading increases tissue deformation – up to a point

  36. Theoretic Bases of Aging Genetic Theories - Aging genes trigger age-related changes - Hormonal production rate - Increased susceptibility to infectious diseases Environmental Theories - Cumulative degeneration - Metabolic rate decreases with age - Cellular failure from genetic mutations from Herzog Box 4-5 on page 119

  37. 25% of postmenopausal women have radiological signs of osteoporotic fracture Herzog Fig 4-30A&B Same compression fracture of endplates as seen on x-ray and on MRI

  38. Bone density scan of patients femoral neck (shaded area is normal range as function of age) Herzog Fig 4-30C

  39. Age Related Changes in Articular Cartilage Cellular level changes Molecular changes Impaired development of osmotic pressure Loss of ability to retain water within matrix Functional changes Reduced shock absorption Increased friction Visual changes Roughening of joint surface (surface may undergo ulceration) from Herzog page 121

  40. Age Related Changes in Nervous System 1. Decreased sensory sensitivity 2. Decreased reflex activity 3. Denervation of muscle spindles from Herzog page 121

  41. Occam’s Razor: the notion that the best explanation is probably the simplest one that is able to explain all observations from Herzog page 122

  42. Mechanical Buckling: a deformation that occurs suddenly and is disproportionately large for an incremental increase of the applied load. from Herzog page 122

  43. Buckling phenomenon in isolated lumbar FSU Flexion Lateral flexion Herzog Fig 4-31

  44. L5 L3,4 Buckling behavior in normal lumbar FSR L2 L1 L5 Buckling behavior after injury to L5-S1 disc L3 L4 L2 L1 Herzog Fig 4-32

  45. Factors Associated with Spinal Buckling (isolated FSUs and FSRs) Buckling Factor Comment 1. Single overload event May be load-rate dependent a. Unguarded Muscle fatigue or unexpected loading b. Guarded Large loads 2. Prolonged static posture Incremental loading after creep deformity 3. Acceleration by vibration More rapid response, larger displacements from Herzog Table 4-10 on page 123

  46. Biomechanical tests that apparently discern between healthy and unhealthy subjects Test Procedure Biomechanical Attribute Straight leg raise Sciatic nerve pain sensitivity to compression/stretch Pelvic symmetry Postural symmetry Hip rotation Flexibility Abdominal strength Strength Prone press-up pain Pain response to extension bending moments from Herzog Table 4-11 on page 125

  47. Studies done concerning manual diagnostic procedures Procedure Attribute Validity Reliability Deep knee tapping Twitch response 0 1 Joint play Stiffness/pain 0 5 Leg length Relative kinematics/pain 0 2 Motion palpation Relative kinematics/pain 1 7 Muscle tenderness Pain response 1 2 Muscle tension Stiffness 1 1 Sacroiliac palpation Relative kinematics/pain 0 2 Static palpation Relative position/pain 0 1 from Herzog Table 4-12 on page 125

  48. Two different relevant questions to be addressed by manual spinal evaluation 1. Is this subject healthy or not healthy? 2. If not healthy, what is the level of the lesion? from Herzog page 126

  49. Differences Between Healthy & LBP Groups Lumbar Range of Motion Pressure Sensitivity LBP healthy degrees Lumbar Spinous Process Lumbar Paraspinal Muscles Herzog Fig 4-33 Herzog Fig 4-34 • LBP group has decreased ROM • 2. LBP group has increased sensitivity to pressure • on both the spinous processes & paraspinal muscles

  50. Valid Exam Findings (there is some supporting evidence – although minimal) Intersegmental Ensemble Intersegmental motion palpation Active: symmetry of accessory (coupled) motions Passive: Symmetry of compliance Midrange joint compliance (end feel) Overpressure symmetry Algometer load to spinous pain Algometer load to paraspinal pain Symmetry of paraspinal algometry Regional Ensemble Standing iliac spine symmetry Seated iliac spine symmetry Differential hip rotation (total internal – total external) Lumbar forward bending flexibility Lower abdominal strength Pain at onset of prone press-up from Herzog Table 4-13 on page 127

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