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Orthopedic Biomechanics

Orthopedic Biomechanics. 沈文哲. 台灣 高雄市 博正醫院. Course Objectives. Why are we studying this? Terminology Understanding the condition Management of fractures Design and application of implants. Stress Strain Curve. Strain. Load Deformation Curve. Creep. Tension band.

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Orthopedic Biomechanics

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  1. Orthopedic Biomechanics 沈文哲 台灣 高雄市 博正醫院

  2. Course Objectives • Why are we studying this? • Terminology • Understanding the condition • Management of fractures • Design and application of implants

  3. Stress Strain Curve Strain

  4. Load Deformation Curve

  5. Creep

  6. Tension band Converts tension forces into compression forces

  7. Which is Strongest? How many twists are needed?

  8. 1) Rt side 2) Left side 3) No difference 4) Depends on the lumbar spine status Which hand do you hold the cane? Osteonecrosis Rt hip is painful

  9. The Non-Painful Side

  10. Which leg goes first when climbing stairs? Rt knee is painful

  11. 好腳上天堂, 壞腳下地獄 Painful knee kept straight.

  12. Which brace to order?

  13. Think of the Forces 3-point fixation

  14. Where to place the knot? Submandibular position hyperextension distraction “long drop” 83kg – 173 cm 51kg – 244 cm

  15. Deforming Forces

  16. Fracture Patterns AO classification (Muller)

  17. Different Forces

  18. Classification Based on Mechanism of Injury Allen classification of cervical spine injuries

  19. Plate Fixation 6 wks 3 mo 1 yr

  20. A Load Bearing Construct 1 mo 12 mo

  21. How long a plate? What kind of screw? Lag screw

  22. What angle? Where to put the plate?

  23. Placement of Implant

  24. How long? • How thick? • Titanium? • Solid? • Cross section? • Fluted? • Tapered? • Bowing? • Reaming? • Interlocking? • Cost!

  25. Stress risers Removal?

  26. Load Sharing and Stress Shielding Re-fracture

  27. Wolff’s Law Bone deposits along lines of stress transmission

  28. External Fixators Rubber band

  29. Fixator Design

  30. Hip Screws Gamma nail

  31. Choice of Implant

  32. Hip Prosthesis

  33. Choices of Stem

  34. Modularity

  35. Knee Prosthesis

  36. “軟骨凸出壓迫神經”

  37. Rank the intradiscal pressures • Bending forward at waist • Squatting • Sitting • Standing • Supine

  38. Herniated Disc

  39. How big can you make the hole? • 1) 75% of lamina • 2) 50% of lamina • 3) 75% of facet • 4) 50% of facet • 5) 25% of facet

  40. Spondylolisthesis Reduction flexion

  41. Missing Anterior Strut

  42. Fatigue Failure of the Screw

  43. Anterior Strut Only Fusion Cage椎籠 “子彈”

  44. Does Not Resist Extension Forces

  45. 40% Failure Rate • Biomechanically, an anterior strut requires posterior support. • “Supported on two rollers”

  46. Combined Ant/Post Fusion

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