Skeleton2

Skeletal Considerations for Movement :Skeletal Considerations for Movement Robert C. Manske, MPT, CSCS Wichita State University Department of Physical Therapy Via Christi Regional Medical Center


Introduction :Introduction Skeletal framework determines shape of body size Can be influenced by nutrition, activity level and postural habits General shape and size of bones inherited, structural adaptations can occur by weight bearing and forces exerted by tendons, ligaments and muscles


Functions of Skeletal System :Functions of Skeletal System Levers: simple machine that magnifies force or speed of movement primarily the long bones of the body, and axes are joints where the bones meet


Functions of the Skeletal System :Functions of the Skeletal System Support support to maintain upright posture increase in size from top to bottom, as more weight is assumed by the skeletal structure Other Functions protection to brain and organs storage of fats and minerals blood cell formation or hematopoiesis


Architecture of Bone :Architecture of Bone Compact Bone: Exterior is compact and cortical. Has hollow tubes and laminae which form haversion canals. Provides strength Can withstand large levels of wt. Bearing or tension


Architecture of Bone :Architecture of Bone Spongy Bone: Cancellous bone interior. Weaker and less rigid than compact. Trabecula small flat pieces of bone. High porosity gives high energy storage capability High incidence of fracture in elderly


Long Bones :Long Bones Longer than they are wide Have shaft and diaphysis Shaft widens at end to form metaphysis End of bone is epiphysis


Long Bones :Long Bones End of bone consists of thin outer layer of compact bone covering spongy bone Periosteum is thin membrane covering bone Support body and create levers Length formed by compressive forces Protuberances formed by tensile forces


Short Bones :Short Bones Consist of primarily spongy bone covered with thin layer of compact bone Play an important role in shock absorption and transmission of forces


Flat Bones :Flat Bones Represented by ribs, scapula, ilium and sternum Two layers of compact bone, with spongy bone and marrow in between Protect internal organs and offer surfaces for muscular attachment


Irregular Bones :Irregular Bones Skull, pelvis and vertebrae Consist of spongy bone with a thin compact bone exterior Functions include weight bearing, dissipating loads. Protecting spinal cord, site for muscle attachments


Sesmoid Bones :Sesmoid Bones Short bone embedded within a tendon or joint capsule Found in the quadriceps, base of first metatarsal in flexor hallucis brevis, thumb in the flexor pollicus brevis


Bone Tissue :Bone Tissue Constituency One of body’s hardest structures 60-70% of bone made from calcium, minerals, phosphates and collagen 25-30% of weight water


Bone Tissue :Bone Tissue Resorption and Deposit of Bone Very sensitive to disuse, immobilization or vigorous activity and high levels of loading Self repairing and can alter its properties in response to mechanical demand “Wolff’s Law”: Every change in form and function of a bone or of their function alone is followed by certain definitive changes in their internal architecture, and equally definite secondary alteration in their conformation, in accordance with mathematical laws


Bone Tissue :Bone Tissue Resorption and Deposit of Bone Dynamic tissue in which large volumes of bone are removed through bone resorption and replaced through bone deposit Bone mass can be increased through exercise Deposits will exceed bone resorption when there is injury or when greater strength required More dense at sites where stress is greatest


Bone Tissue :Bone Tissue Physical Activity Vs Bone Remodeling Require mechanical stress in order to grow and strengthen Require daily stimulus to maintain health Intermittent loading 100 cycles a day produces significant increase in bone cross sectional area


Bone Tissue :Bone Tissue Lack of Activity Vs Bone Remodeling Significant losses can occur after inactivity Lack of wt bearing causes: less rigidity, more bending displacement, decrease in length, decreased cortical cross section and slow bone formation


Bone Tissue :Bone Tissue Bone Deposit in Soft Tissue myositis ossificans bone deposit laid down in soft tissue as a response to trauma or hematoma begins as fibrous tissue that eventually develops into cartilage and then bone


Bone Tissue :Bone Tissue Osteoporosis When bone resorption exceeds bone deposits Decrease in bone mineral mass, resulting in reduced bone density Loss of trabecular integrity creates weakness Can be hormonal, nutritional or lack of ex’s After age 30, .2-.5% yearly loss of mineral weight of bone After menopause bone loss 50% greater than in males


Strength and Stiffness :Strength and Stiffness Anisotropic Characteristics: Behavior will vary depending on direction of load. Can tolerate greatest load in longitudinal direction. Tolerates least when applied across surface.


Strength and Stiffness :Strength and Stiffness Viscoelastic Characteristics: Respond to the rate at which load is applied. Handle greater stress at higher speeds of loading. Slow loading causes fracture at 1/2 load.


Strength and Stiffness :Strength and Stiffness Elastic Response: Will change length or shape when load is applied. Deforms no more than 3%. This is considered elastic range of load deformation curve


Strength and Stiffness :Strength and Stiffness In elastic range, when stress is released bone will return to original form. Yield point, when fibers in material begin to fail Plastic phase is when microtears and debonding occurs


Strength and Stiffness :Strength and Stiffness If loading continues, bone tissue will permanently deform and eventually fracture. In plastic phase, when stress removed bone will not return to original length.


Strength of Bone :Strength of Bone Usually determined by failure point or load sustained before failure. Can also be assessed by energy storage, area beneath load deformation curve


Stiffness of Bone :Stiffness of Bone Determined by the slope of load-deformation curve during elastic response range. Stiff Material: minimal deformation to increased loads


Stiffness of Bone :Stiffness of Bone Stiff Material: minimal deformation to increased loads


Stiffness of Bone :Stiffness of Bone Brittle Material: will fail at the end of elastic phase. Ductile Material: continues to elongate and deform a great deal in the plastic phase.


Types of Loads :Types of Loads Compression Forces: Forces ends of bones together. Produced by muscles, wt. Bearing, gravity. Can be responsible for PFPS, vertebral fractures.


Types of Loads :Types of Loads Tension Forces: Pull or stretch of bone apart. Maximum stress applied to bone perpendicular to plane of the applied load. Can cause avulsion fractures. Can cause tendonitis.


Types of Loads :Types of Loads Shear Forces: Force applied parallel to surface, creating deformation internally in an angular direction. Acts on the surface parallel to the plane of applied force. Cause rapid failure.


Types of Loads :Types of Loads Shear Forces: Can produce fractures of femoral condyles or tibial plateau.


Types of Loads :Types of Loads Shear Forces: Can produce a spondylolysis & spondylolisthesis.


Types of Loads :Types of Loads Bending Forces: Applied to area with no direct support. One side will form concavity, while other side will form convexity. Typically bone will fracture on convex side.


Types of Loads :Types of Loads Bending Forces: In normal stance the femur bends anteriorly and laterally, tibia bends anteriorly. Bone stronger where bending occurs.


Types of Loads :Types of Loads Bending Forces: Three Point Force Application: force applied perpendicular to bone at ends of bone, force applied opposite in middle. Bone will break in middle. Used in bracing.


Types of Loads :Types of Loads Torsional Forces: Twisting manor creating shear over the entire bone. Magnitude of stress increased with distance of axis of rotation. Create fractures in humerus and lower extremity.


Types of Loads :Types of Loads Injury Vs Loading Muscular activity can influence loads that are transmitted to bones. Muscular forces can reduce tensile and compressive forces on bones. When muscles fatigue, their ability to alleviate the load on the bone diminishes, which makes them more susceptible to injury.


Types of Loads :Types of Loads Stress Fracture Will occur during a load application that produces a shear or tensile strain and results in lacerations, fractures, ruptures and avulsions. Can result from a response to several large excessive loads or through a large number of low to moderate levels of force.