Biomechanics 1 Final Exam
What is the role of the Volar Plates of the hand?
-Improve stability -Limit excessive extension/hyperextension
Types of motion produced by net unbalanced force vs net unbalanced torque
n.u. force produces translation n.u. torque produces rotation Combination of both produce Curvilinear motion
Which motions of elbow have hard end-feels?
-Extension -Pronation
What does load refer to?
-Forces applied to a structure -magnitude, direction and rate of force will affect the tissue's response to load
What is a Concurrent Force System?
-Forces applied to same object but action lines at different angles to each other
What do accessory joint structures such as labrums and menisci help with?
-Increases joint congruence (fit) -Increase stability -Absorb compressive joint forces
What is the most common injury to the hand in work or sports?
-Injury to PIP collateral ligaments -Radial side 2x likely to get injured
What factors will increase torque in a system?
-Longer moment arm = more torque -Greater magnitude of force = more torque
What are the different types of stress that can be imposed on the body?
-Tensile stress -Compressive stress -Shear stress -Torsional stress -Bending stress
What are the different types of displacement?
-Translation -Rotation -General movement is combination of both
What is a Distraction Force?
-net force that moves a bony segment away from its adjacent segment -causes separation at joint between two bones
What are the different types of Synovial Joints?
-plane -hinge -pivot -condyloid -saddle -ball and socket
How do you increase stability of the Base of Support?
-wider base of support = more stability -lower to ground = more stability
What is the normal carrying angle for the elbow in men?
10-12 degrees
What is the normal carrying angle for the elbow in women?
13-17 degrees
How many joints make up the elbow complex?
4 joints -Humeroulnar -Humeroradial -Proximal Radioulnar -Distal Radioulnar
What is the healing potential of Hyaline Cartilage?
Avascular, no cell turnover so it does not heal/regenerate
What produces Joint Reaction Forces?
Compression Forces
What is the arthrokinematics of the AC joint?
Concave on Convex (roll and glide in same directions)
What are the arthrokinematics of the Humeroradial Joint?
Concave radial head on Convex surface of capitulum (roll and glide in opposite direction)
What are the arthrokinematics of the Humeroulnar Joint?
Concave trochlear notch on Convex trochlea (roll and glide in same direction)
What are the arthrokinematics of the Radiocarpal joint?
Convex on Concave (roll and glide in opposite directions)
What is the arthrokinematics of the GH joint?
Convex on Concave (roll and glide in opposite directions)
Where is hyaline cartilage located?
Covers ends of articulating bones in synovial joints
What is the deformation that happens under the influence of persistent mechanical stress?
Creep
What is the force coupling for the GH joint?
Deltoid applies superior force while Infraspinatus, Subscapularis, and Teres Minor provide compressive and inferior force to hold Humeral Head in Glenoid cavity
What angle does a force become a Stabilizing Component? When does it become a Destabilizing Component?
Depends on joint angle
What is the difference between a Stress-Strain Curve and a Load-deformation Curve?
Different tissues can be compared w/ a Stress-Strain curve. Cannot compare different tissues w/ a Load-deformation curve.
What produces Capsuloligamentous Tensile Forces?
Distraction Forces
3rd class lever
Effort force in middle of fulcrum and resistance force
What is Newton's second law?
F = m * a Linear acceleration is proportional to net unbalanced forces or torques acting on an object
Which motions of elbow have primarily soft end-feels?
Flexion
What is Newton's third law?
For every action there is an equal and opposite reaction, when object 1 applies force to object 2, object 2 also applies force in equal force and opposite direction
What is the definition of Stress in terms of biomechanics?
Force applied to cross-sectional unit of material
What are coplanar forces?
Forces acting in same plane
What are colinear forces?
Forces acting on same line
1st class lever
Fulcrum in the middle of Effort force and Resistance force
What accessory structure of the GH joint increases the depth of the glenoid fossa?
Glenoid Labrum
Internal Forces vs. External Forces
Internal forces arise from within the body External forces come from outside force
What is the study of the forces that cause motion?
Kinetics
What is Newton's first law?
Law of Inertia -Sum of all forces = 0, object is at rest -Object at rest will remain at rest until acted upon -If sum of forces does not = 0, object MUST be accelerating
What is active insufficiency?
Muscle cannot contract maximally across two joints at the same time
What is passive insufficiency?
Muscles that cross 2 joints cannot stretch maximally across both joints at the same time
What is the definition of Strain in terms of biomechanics?
Percentage change in length and/or cross section of a material
What is the force couple for scapular rotation?
Produced by Trapezius and Serratus anterior during upward rotation of scapula
What are the arthrokinematics of the Proximal Radioulnar Joint? the Distal Radioulnar Joint?
Proximal radioulnar: Convex on Concave (roll and glide in opposite direction) Distal radioulnar: Concave on Convex (roll and glide in same direction)
2nd class lever
Resistance force in middle of fulcrum and effort force
What is the arthrokinematics of Convex on Concave?
Roll and glide in same direction
What do shunt muscles do?
Shunt muscles pull joint surfaces together to stabilize joint
Simple Joints vs Complex Joints
Simple joints = Stability Complex joints = Mobility
What do spurt muscles do?
Spurt muscles apply force across bone to create movement at joint
What concept describes the difference between a rapid application of force vs slow application?
Strain-Rate sensitivity: when force is applied rapidly, larger force is required to deform tissue
What is Kinematics?
Studies the qualities of motion: -type of motion -location in space of displacement -direction and magnitude of displacement -rate of change
What is a Resultant Vector?
Sum of all forces of in the same Linear Force System composed into a single vector
Which motions of elbow have primarily firm end-feels?
Supination
Joint Classifications based on Movement
Synarthrosis: little to no movement, usually fibrous Amphiarthrosis: minimal to moderate movement, usually cartilaginous Diarthrosis: Freely moveable, usually synovial
What Deformation is caused by Tensile Loads? Compressive force?
Tensile load leads to Elongation Compressive force leads to Compression
What is reciprocal inhibition?
The contraction of one set of muscles is accompanied by the relaxation of the antagonist muscles, motor neurons antagonist muscle are reflexively inhibited
What does Stress-Relaxation describe?
The force required to maintain a new stretched tissue length will decrease over time
What are the special rules for the arthrokinematics of the Midcarpal Joint?
Ulnar pole of Midcarpal Joint: Convex on Concave (roll and glide opposite directions) Radial pole of Midcarpal Joint: Concave on Convex (roll and glide same directions)
What is the relationship between Line of Gravity and Base of Support?
Vertical line of gravity must fall within base of support in order for a person/object to be stable
What is a Linear Force System?
When vectors are Colinear and Coplanar, they are considered part of a Linear Force System
What is the Rotary Component of a force system?
portion of force that is applied at 90 degrees to segment
