1. Right ulna and radius in relation to the humerus and carpals

2. Skeleton of the Hand
The carpus (wrist) consists of 8 small bones (carpals)
Two rows of carpal bones
Proximal row - scaphoid, lunate, triquetrum, pisiform
Distal row - trapezium, trapezoid, capitate, hamate
Scaphoid - most commonly fractured
Carpal tunnel - space between carpal bones and flexor retinaculum

3. Articulations formed by the ulna and radius
Copyright 2009 John Wiley & Sons, Inc.
Articulations formed by the ulna and radius

4. Metacarpals and Phalanges
Five metacarpals - numbered I-V, lateral to medial
14 phalanges - two in the thumb (pollex) and three in each of the other fingers
Each phalanx has a base, shaft, and head
Joints - carpometacarpal, metacarpophalangeal, interphalangeal

5. Right wrist and hand in relation to ulna and radius

6. Skeleton of the Lower Limb
Two separate regions
1. A single pelvic girdle (2 bones)
2. The free part (30 bones)
Point out that the lower limb bones are larger and stronger than the upper limb bones due to the need to support the weight of the body

7. Pelvic (Hip) Girdle
Each coxal (hip) bone consists of three bones that fuse together: ilium, pubis, and ischium
The two coxal bones are joined anteriorly by the pubic symphysis (fibrocartilage)
Joined posteriorly by the sacrum forming the sacroiliac joints

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Right Hip Bone

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10. 08_10c

11. Bony Pelvis

12. The Ilium Largest of the three hip bones
Ilium is the superior part of the hip bone
Consists of a superior ala and inferior body which forms the acetabulum (the socket for the head of the femur)
Superior border - iliac crest
Hip pointer - occurs at anterior superior iliac spine
Greater sciatic notch - allows passage of sciatic nerve

13. Ischium and Pubis
Ischium - inferior and posterior part of the hip bone
Most prominent feature is the ischial tuberosity, it is the part that meets the chair when you are sitting
Pubis - inferior and anterior part of the hip bone

14. False and True Pelves
Pelvic brim - a line from the sacral promontory to the upper part of the pubic symphysis
False pelvis - lies above this line (Fig 8.9b)
Contains no pelvic organs except urinary bladder (when full) and uterus during pregnancy
True pelvis - the bony pelvis inferior to the pelvic brim, has an inlet, an outlet and a cavity
Pelvic axis - path of baby during birth

15. True and False Pelvis

17. Right Lower Limb

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Right Femur

19. Patella

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Tibia and Fibula

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Tibia and Fibula

22. Skeleton of the Foot - Tarsals, Metatarsals, and Phalanges
Copyright 2009 John Wiley & Sons, Inc.
Skeleton of the Foot - Tarsals, Metatarsals, and Phalanges
Seven tarsal bones - talus (articulates with tibia and fibula), calcaneus (the heel bone, the largest and strongest), navicular, cuboid and three cuneiforms
Five metatarsals - (I-V) base, shaft, head
14 phalanges (big toe is the hallux)
Tarsus = ankle

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Right Foot

24. Arches of the foot

25. Vertebral Segments

26. A-P View

27. Secondary Curves Lateral

28. Vertebral Column

29. Osteology Typical Vertebrae Body Vertebral Arch Spinal Foramen
Superior and inferior surfaces of body (plateaus)
Thickened around the rim, location of epiphyseal plates
Cartilaginous end-plates
Vertebral Arch
Pedicles, Laminae
Transverse Processes
Spinous Process
Facets – superior articular and inferior articular
Spinal Foramen
Intervertebral Foramen

30. Typical Vertebrae

31. Typical Vertebrae

32. Typical Lumbar

33. Typical Thoracic

34. Typical C

35. BIOMECHANICS

36. Basic Biomechanics Depends on Shape and Material!
Material Properties
Elastic-Plastic
Yield point
Brittle-Ductile
Toughness
Independent of Shape!
Structural Properties
Bending Stiffness
Torsional Stiffness
Axial Stiffness
Depends on Shape and Material!
Material Properties: fundamental behaviors of a substance independent of its geometry.
Structural Properties: the ability of an object to resist bending under torsion, axial load, or bending is a function of its shape and distribution of material around the cross section.

37. Basic Biomechanics Force, Displacement & Stiffness
Slope = Stiffness = Force/Displacement
Force applied to a body causes a deformation. If one plots a graph of displacement due to the force applied to a material, the slope of the curve represent the material’s stiffness.
Displacement

38. Basic Biomechanics Force Strain= L / L0 Stress =Force/Area Area L
Stress: is the force applied per unit area (F/A).
Strain: is the change in a material’s length due to an applied stress relative to its original length = L/ L0.
Stress =Force/Area
Strain= L / L0

39. Basic Biomechanics Stress-Strain & Elastic Modulus
Slope = Elastic Modulus
If one graphs the resulting strain (L/ L0) due to the applied stress (F/A), the slope of the Stress-Strain curve is the Elastic Modulus.
Strain

40. Basic Biomechanics Common Materials in Orthopaedics
Elastic Modulus (GPa)
Stainless Steel
Titanium
Cortical Bone
Bone Cement
Cancellous Bone
UHMW-PE
Stress
Review the elastic modulus of common materials encountered in orthopaedic surgery relative to each other.
Strain

41. Basic Biomechanics Elastic Deformation Plastic Deformation Energy
Force
Energy Absorbed
Elastic Deformation: In the elastic region, the relationship of displacement to the applied force in linear. In this region, the material returns to its resting state if the force is removed (elastic), like a rubber band.
Stiffness: again, is the slope of the elastic portion of the force-displacement curve.
Plastic Deformation: As more force is applied, the material’s behavior becomes plastic, and permanent deformation occurs. The material will not return to its original state after the force is removed (like when you bend a plastic ice cream spoon to far it stays bent).
Energy: The area under the curve represents energy absorbed into the material during the deformation process (work).
Displacement

42. Basic Biomechanics Stiffness-Flexibility Yield Point Failure Point
Brittle-Ductile
Toughness-Weakness
Elastic
Plastic
Failure
Yield
Force
Stiffness: The steeper the slope, the stiffer the material. A material with a flat slope is flexible.
Yield Point: the point on the force-displacement curve where the material changes from elastic to plastic deformation is the yield point.
Failure Point: At some point the material will break; this point due is the material’s Failure Point.
Brittle: a material which experiences little plastic deformation before it fails is said to be brittle (glass for example).
Ductile: if a material with a large plastic deformation region before it fails is said to be ductile (copper for example).
Toughness: a material which can absorb more energy prior to failure (large area under the curve) is said to be tougher.
Weakness: a material which can absorb little energy prior to failure (small area under the curve) is said to be weak.
Stiffness
Displacement

43. Stress Strain Stiff Ductile Tough Strong Stiff Brittle Strong Ductile
Weak
Brittle
Weak
Strain

44. Stress Strain Flexible Brittle Strong Flexible Ductile Tough Strong
Weak
Flexible
Ductile
Weak
Stress
Strain

45. Basic Biomechanics Load to Failure Fatigue Failure
Continuous application of force until the material breaks (failure point at the ultimate load).
Common mode of failure of bone and reported in the implant literature.
Fatigue Failure
Cyclical sub-threshold loading may result in failure due to fatigue.
Common mode of failure of orthopaedic implants and fracture fixation constructs.
Compare the two types of failure:
Load to Failure: Continuous application of force until the material breaks (failure point at the ultimate load). Bone usually fractures by load to failure.
Fatigue Failure: Cyclical sub-threshold loading may result in failure due to fatigue.
Load to failure testing often reported in the orthopaedic literature: however, clinically, failure fracture fixation constructs or implants often due to fatigue failure.

46. Basic Biomechanics Anisotropic Viscoelastic
Mechanical properties dependent upon direction of loading
Viscoelastic
Stress-Strain character dependent upon upon the speed at which the force is applied
Anisotropic: some materials (bone) have different mechanical properties dependent upon the type of load applied (transverse, longitudinal, shear).
Viscoelastic: many biological materials to include bone reveal different stress-strain curves depending upon the speed at which the force is applied.

47. Bone Biomechanics
Bone is anisotropic - its modulus is dependent upon the direction of loading.
Bone is weakest in shear, then tension, then compression.
Ultimate Stress at Failure Cortical Bone
Compression < 212 N/m2
Tension < 146 N/m2
Shear < N/m2
Bone is anisotropic-its modulus is dependent upon the direction of loading. Bone is weakest in shear, then tension, then compression. This can help us understand the fracture produced (failure) from various mechanisms (applied loads).
Review the values of the Ultimate Stress at Failure of cortical bone based upon the different direction of loading for cortical bone.

48. Figure from: Browner et al: Skeletal Trauma
Bone Mechanics
Cortical Bone
Bone Density
Subtle density changes greatly changes strength and elastic modulus
Density changes
Normal aging
Disease
Use
Disuse
Trabecular Bone
Bone, as a living material, can experience changes in its density. Subtle density changes can have great effects upon the material properties of the bone. Graph shows a marked change in the stress/strain curve of trabecular bone when its density is decreased by a factor of 3.
These changes occur with normal aging, disease, use and disuse.
Figure from: Browner B., Jupiter J., Levine A., Trafton P., Skeletal Trauma 2nd Edition, W.B. Saunders, 1998, figure 4-5, pg. 101
Figure from: Browner et al: Skeletal Trauma
2nd Ed. Saunders, 1998.

49. Basic Biomechanics Bending Axial Loading Torsion
Tension
Compression
Torsion
These bending, torsion, tensile and compressive forces are applied to bones, and if excessive, may lead to fracture.
Bending Compression Torsion

50. Figure from: Browner et al: Skeletal Trauma 2nd Ed, Saunders, 1998.
Fracture Mechanics
The nature of the applied force is often evident by the nature of the fracture.
Tension – Transverse Bending - Butterfly
Compression - Oblique Torsion - Spiral
Figure from: Browner B., Jupiter J., Levine A., Trafton P., Skeletal Trauma 2nd Edition, W.B. Saunders, 1998, figure 4-9, pg. 103.
Figure from: Browner et al: Skeletal Trauma 2nd Ed, Saunders, 1998.