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Biomechanics Flashcards

1
Q

% of stance and swing phase

A

stance - 60%

swing - 40%

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2
Q

How to measure true vs apparent LLD

A

TRUE: ASIS to medial mall

APPARENT: umbilicus to medial mal

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3
Q

3 phases of stance phase

A

contact - 27%
midstance - 40%
propulsion - 33%

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4
Q

Normal Angle and Base of Gait

A

Angle: 15 deg (7.5 deg unilateral)

Base: 3 in (1.5 in unilat)

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5
Q

Normal Hip Transverse Plane ROM (with hip flexed and extended)

A

Internal rotation - 45 deg
External rotation - 45 deg

** if less ROM with hip extended than flexed, then capsular ligaments tight

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6
Q

Normal Hip Frontal Plan ROM

A

45 deg ABduction, 45 deg ADduction

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7
Q

Normal Hip Sagittal Plane ROM

A

KE flexion: 70-90 deg
KF flexion: >120 deg

KE/KF extension: 20-30 deg

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8
Q

Normal Malleolar Position/Tibial Torsion

A

Malleolar Position: 15-20 deg ext rot

Tibial Torsion: 18-23 ext

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9
Q

Normal Ankle Joint ROM

A

DF KE: 10 deg
DF KF: >10 deg

PF: 40-70

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10
Q

How to calculate NCSP

A

STJNP + TI

IE: TOTAL REARFOOT DEFORMITY!!

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11
Q

STJ normal ROM

A

20 deg inv, 10 deg evert, total ROM 30 deg (2:1 ratio)

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12
Q

Normal STJNP

A

0 (“rectus”) -2 deg inverted

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13
Q

STJNP

A
  • positon where the STJ is neither pronated nor supinated
  • it is the position of MAXIMUM JOINT CONGRUITY
  • position of GREATEST COMPRESSION FORCES AND LEAST TORSIONAL FORCES
  • “closed packed position”
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14
Q

Neutral Calcaneal Stance Position

A
  • angle that the posterior bisection of the calcaneus makes with the ground when the individ is in static stance and the STJ is held in neutral position

** it equals the TOTAL REARFOOT DEFORMITY!!!

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15
Q

Most RF valgus is a result of what?

A

genu valgum

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16
Q

Relaxed Calcaneal Stance Position

A
  • position of the sagittal bisection of the calcaneus to the ground while standing in a relaxed manner in patient’s normal angle and base of gait

** represents COMPENSATION at the STJ

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17
Q

when is the MTJ locked?

A

when STJ is in NP and the MTJ is maximally pronated

  • this is the position of max stability; incapable of further MTJ motion; contributes to the mobile adapter/rigid lever function of the foot
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18
Q

forefoot supinatus

A
  • a fixed ST adaptation as a result of the FF functioning in a chronically inverted position

** looks like FF varus but it is a ST rather than bony deformity

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19
Q

Purpose of Orthoses

A
  • to support, align, prevent, or correct deformities

- improve function of movable parts of the body

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20
Q

definition of biomechanics

A
  • a study of the application of mechanical laws to human locomotion
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21
Q

plane can be drawn by connecting (how many) points?

A

3

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22
Q

Axis

A
  • line created by the intersection of 2 or more planes and about which motion can occur
  • described as the amount of deviation from all 3 cardinal planes
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23
Q

As the axis moves further away from a particular plane, does more or less motion occur in that plane?

A

MORE

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24
Q

Examples of uniaxial joints of LE (i.e., a joint which allows motion only about one axis)

A
  • ankle
  • STJ
  • interphalangeal
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25
Q

2 LE examples of biaxial joints

A
  • knee joint (flex/ext and int/ext rotation)

- metatarsophalangeal joints (DF/PF and abd/add)

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26
Q

Which LE joint is triaxial

A

hip joint

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27
Q

T/F: the position of the axis of a joint changes depending on where the joint is within its ROM

A

true – this concept is referred to as the “instantaneous axis of motion” (IAR)

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28
Q

Example of biplanar motion in LE

A

1st ray – as it DF it inverts, and as it PF it everts

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29
Q

Examples of triplanar motion in LE

A
  • STJ, AJ, MTJ, 5th ray – all pronate and supinate which is triplanar motion
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30
Q

Planar Dominance

A

when the joint axis is deviated further away from one particular plane than normal, the joint motion can be described as having planar dominance in that particular plane

** important with flatfoot

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31
Q

Degree of Freedom

A

the number of independent angular motions available at a joint

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32
Q

Hypermobility

A

a part that is moving when it should be stable

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33
Q

Energy

A

the ability of an object to do work

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34
Q

potential energy vs kinetic energy

A

potential energy - stored

kinetic energy - energy of motion in an object

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35
Q

Force

A
  • a push or pull with BOTH magnitude and direction
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36
Q

Force = (equation)

A

mass x acceleration

  • NEWTON’S 2ND LAW*
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37
Q

TORQUE

A

a rotational equivalent of force – rotates an object about an axis of rotation

*synonymous with “moment”

= perpendicular force x length of lever arm

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38
Q

Moment

A

the tendency of a force to twist or rotate an object

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39
Q

Internal Moment

A
  • rotational force (torque) from within the body

e. g., muscles, ligaments, bony architecture

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40
Q

External Moment

A

rotational force from outside the body

e.g., GRF, momentum, gravity

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41
Q

Most common lever type in the MSK system

A

third class lever (mech adv

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42
Q

First Class Lever

A

axis of rotation is between the opposing forces (e.g., AT) – like a see-saw

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43
Q

Second class lever

A

axis of rotation located at one end of bone; internal moment (like muscle) at other, and load in b/w (RARE IN THE BODY)

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44
Q

Newton’s 1st Law

A

i.e., law of inertia - body in motion will tend to stay in motion and a body at rest will tend to stay at rest until acted upon by an external force

bmx implication: momentum

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45
Q

Newton’s 2nd Law

A

an external force will cause the body to accelerate in the direction of force (Force = mass x acceleration)

  • acceleration is proportional to the force and inversely proportional to the mass
  • bmx implication: change in momentum
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46
Q

Newton’s 3rd law

A

for every action there is an equal but opposite reaction

*bmx implication: GRF

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47
Q

Work =

A

force over distance measured in joules (= N*m)

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48
Q

Power =

A

rate at which work is done (Joules/sec = watts)

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49
Q

units of : force, work, power

A

force: N
work: joules
power: watts

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50
Q

Perry’s 4 Functions of the supporting limb (i.e., each WB limb accomplishes 4 functions):

A
  1. shock absorption
  2. stance stability
  3. energy conservation
  4. propulsion
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51
Q

Center of mass is thought to be located where?

A

anterior to S2

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52
Q

Center of gravity - fixed or fluid?

A

not fixed! - changes with position of body

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53
Q

3 Rockers during stance

A
  1. Heel Rocker (heel strike/loading response)
  2. Ankle Rocker (midstance)
  3. Toe Rocker (propulsion)
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54
Q

Kinematics definition

A

study of motion

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55
Q

Kinetics

A

study of FORCES that cause motion, masses, and moments

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56
Q

concentric contraction

A

muscle contraction in which the length of the muscle is shortened (usually accelerating function)

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57
Q

eccentric contraction

A

muscle contraction during which time the length of the muscle is elongating (usually decelerating function)

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58
Q

Center of gravity

A

average location of the body’s weight

** changes based on the forces applied (i.e., dependent on gravitational force)

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59
Q

center of mass

A
  • anterior to S2
  • point at which all the mass of the body may be considered concentrated in analyzing its motion
    • does not change
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60
Q

momentum

A

momentum = mass x velocity

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61
Q

General rule: muscles generally function as (accelerators or decelerators?) during gait

A

decelerators

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62
Q

What % of body weight applied to limb at heel strike

A

~60% of body weight applied to limb at heel strike in about 20 ms

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63
Q

Loading response - what happens to magnitude of F(y) and F(x)?

A

F(y) diminishing and F(x) beginning to peak – meaning meaning leg beginning to accept weight and initial vertical force decreasing – however, forces pushing us forward start to peak

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64
Q

Which aspect of stance represents the end of shock absorption and the beginning of stability

A

midstance

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65
Q

According to Perry, forward momentum of the body is preserved by what?

A

the three rockers (heel, ankle, and forefoot)

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66
Q

Two types of collision:

A
  • elastic and inelastic
  • elastic collision: the segments continue to move further - i.e., the kinetic energy is transferred from one segment to the other
  • inelastic collision: segments do not move when the segments collide with one another; the energy cannot transfer from one to the other, rather it is TRANSFORMED to other forms of energy (like heat) or it can deform segments
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67
Q

Things that help body with shock absorption during gait (heel strike –> loading response)

A
  • skin and adipose tissue
  • calcaneus everts/ STJ pronates
  • ankle plantarflexes
  • knee flexes
  • hip flexes and then begins to extend
  • MTJ also pronates as the FF dorsiflexes with FF loading

** therefore: if any of these change… i.e., callous/fat pad atrophy/previous trauma/ STJ already pronated/ equinus deformity/ knee already flexed/ hip excessively flexed/ limited MTJ motion …. then less shock absorption!!!

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68
Q

Extrinsic factors of footwear that affect shock absorption

A
  • softer materials produce less energy consumption (although may add weight)
  • good heel counters improve shock absorption by 8-30%
  • shock absorption DECREASED by cooler temps (i.e., any material that we use to make shoes gets harder when it’s cooler, thus shock absorption ability decreases)
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69
Q

Plantar fat pad absorbs what % of shock

A

20-25% shock absorption (fat globules under calcaneus are organized in fibroelastic reticulated “U-structure” –> absorb shock from beneath and transfer in horizontal way via hydrostatic pressure)

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70
Q

Describe 1st Rocker (Heel Rocker) as it pertains to shock absorption

A
  • Heel rocker helps to convert translational KE into rotational KE
  • ankle PF is resisted by the muscles in the anterior compartment of the leg so as to delay FF contact to floor – i.e., spread out the total time for shock absorption
  • simultaneously, the STJ pronates – calcaneus everts and talus plantarflexes and adducts – this permits the ankle mortise to continue moving downward and prevents medial impingement
  • it decreases compressive forces within the calcaneus and the talus
  • STJ pronation is resisted by Tib Post
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71
Q

How does arch of foot aid in shock absorption

A

distributes the GRF and stores energy of the forces through the elastic properties of the ST

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72
Q

How does the knee react to the heel rocker mechanism?

A
  • knee = 2nd shock absorbing mechanism
  • as tibialis anterior muscle eccentrically contracts to resist foot drop during heel strike-loading response, this drags the bony linked leg to follow – rolls about the heel rocker and leads to knee flexion
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73
Q

Hip (flexion or extension) produced by knee flexion and ankle flexion

A

extension

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74
Q

Does longer stride or shorter stride help with shock absorption

A

longer stride helps shock absorption

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75
Q

consequences of joint instability

A
  • acute injury - subluxation
  • chronic condition - DJD
  • decreased efficiency during locomotion
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76
Q

Stability of joints are provided by 4 factors

A
  1. bone and joint congruity- passive
  2. ligamentous and capsular effects - passive
  3. muscle activity and viscoelastic properties - active and passive
  4. balancing through neural feedback
    - visual
    - vestibular
    - sensory afferents
    - golgi tendon organs
    - muscle spindles

** failure of one or more of these subsystems leads to instability

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77
Q

Principles of bone and joint congruity

A
  • the more congruous the joint, the more stable it is
  • joint congruity depends on the surface contact area
    • compression across joint provides stability … vs. rotation across joint produces instability
  • surface contact area changes with each degree of motion
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78
Q

knee screw-home mechanism

A
  • femur internally rotates on tibia (tightens ACL and PCL and LOCKS THE KNEE) – this is a key element to knee stability
  • occurs at the end of knee extension (0-20 deg)
  • occurs b/c medial condyle is greater in radius than lateral condyle
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79
Q

Davis’ Law

A

soft tissue under prolonged tension will start to elongate

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80
Q

Jones’ Law

A

bone grows faster in compression than in tension

(good example = tibia varum – compression on medial side and thus medial side grows faster –> straight legs in adulthood)

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81
Q

Vertical and shear force ____% body weight @ heel lift on UNSTABLE 1st ray

A

125%—> traumatizes plantar tissues and overloads the lesser mets

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82
Q

Muscle has greatest ability to pull at what length?

A

its physiologic length

**once it moves beyond 10% of its resting length, it begins to lose tensile strength

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83
Q

Effect of lever arm

A

tendons attached far from a joint axis have a longer lever arm and therefore produce GREATER TORQUE

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84
Q

sesamoids: how do they affect lever arms

A

they function to INCREASE the moment arm of the tendon –> greater mechanical advantage

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85
Q

what did howard danenberg describe

A

way to correct issue in foot by working on more proximal structures (as in for tx of functional hallux limitus)

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86
Q

For Transverse Plane neutral position of hip, how to calculate?

A

(External - Internal)/2

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87
Q

7 shoe types

A
  • mocassin
  • mule
  • clog
  • oxford
  • pump
  • sandal
  • boot
88
Q

deformities that cause STJ to function in end range pronation

A
  • forefoot varus
  • flexible FF valgus
  • equinus
89
Q

parts of an orthotic

A
  • shell
  • heel cup / heel seat
  • medial/lateral flange
  • medial/lateral clip
  • forefoot extension
  • top cover
90
Q

theories on how functional orthoses work

A
  1. pre-positioning of foot
  2. proprioceptive facilitation
  3. altering extrinsic moments
91
Q

parts of functional orthoses that actually help prevent excessive pronaton

A
  • distal medial aspect of shell
  • anterior medial edge of RF post
  • anti-pronation pressure at distal medial calcaneal tuberosity (as determined by contour of heel cup, i.e., kirby skive)
92
Q

10 points of cast evaluation

A
  1. overall quality
  2. cast markings
  3. skin lines
  4. straight lateral border
  5. 5th digit in line with lateral column
  6. 1/3-2/3 rule
  7. plantar bisection passes through 2nd met
  8. hallux parallel to supporting surface
  9. FF:RF relationship in cast matches that in real life
  10. Appropriate thumb position
93
Q

types of casting techniques

A
  • neutral position casting
  • partial WB cast
  • pronated cast
  • rectus cast
  • vacuum cast
  • computer imaging

** type of casting technique used is 1st determined by the type of orthosis being made

94
Q

neutral position cast

A
  • STJNP
  • MTJ maximally pronated
  • AJ to 90 or 1st resistance, whichever comes first
95
Q

What is the most common cause of failure of orthotic

A

casting technique

  • b/c most partial or full WB techniques do not allow for control at the MTJ, and many practitioners do not have adequate positioning of MTJ when doing off-WB cast
    • need OMJA and LMJA fully loaded/maximally pronated!
96
Q

Straight Lateral Border: cast eval significance

A
  • should be straight in both the transverse and sagittal planes
    • indicates that the OMJA is fully pronated !

note: a supinated OMJA will cause the cast to be convex laterally and the FF to be PF on the RF

97
Q

5th digit in line with lateral column: cast eval significance

A
  • 5th digit should never be DF (more common) or PF (less common)
  • when the 5th digit is DF, the 5th met is relatively PF’d, causing apparent FF varus by supinating the LMJA
98
Q

Plantar heel bisection passes through the 2nd met: cast eval significance

A

if the bisection passes lateral to 2nd met, then the MTJ was probably supinated

99
Q

1/3 - 2/3 rule: cast eval significance

A
  • lateral 1/3 of the longitudinal arch should be flat, the middle 1/3 should be gradually sloping upward, and the medial 1/3 should be rapidly sloping upward.
    • if STJ is pronated, the flat lateral portion will be >1/3
    • if STJ is supinated, the flat lateral portion will be
100
Q

Hallux Parallel to supporting surface: cast eval significance

A
  • generally DF hallux indicates PF 1st Ray (may be a good thing)
  • a PF hallux indicates a DF 1st ray (almost never a good thing)
101
Q

FF:RF relationship in cast: cast eval significance

A
  • increased varus position of the FF in cast compared to foot indicates that the foot was casted with MTJ supinated
  • decreased varus/increased valgus position in cast comp to foot indicates that STJ was pronated
102
Q

Appropriate thumb position: cast eval significance

A
  • no thumb print indicates foot was not loaded!
  • a thumb position falling more medial than 4-5th rays may supinate the MTJ
  • thumb position too far distal may cause DF of 5th digit and PF of 5th met
103
Q

Good skin lines : cast eval significance

A
  • indicate good contact of plaster to skin
104
Q

Anatomical Axis vs Mechanical Axis vs Joint Axis/Axis of Rotation

A
  • Anatomical axis: longitudinal axis of any long bone
  • Mechanical axis: axis that GRF passes through
  • Joint Axis: axis about which motion occurs
105
Q

Example of 2nd class lever in body

A
  • PF of foot to raise body up on toes (Ankle)– the ball of the foot serves as the fulcrum as the ankle PF’s apply force to the calcaneus to lift resistance of body at tibial articulation with foot
106
Q

Kinetics vs Kinematics

A
  • kinetics: the study of forces, mass, and moments

- kinematics: the study of motion

107
Q

how does the neutral position of the hip differ from the NP of most other joints?

A
  • close packed but NOT its max congruous position
108
Q

function of hip capsular ligaments during gait

A
  • stability, - resist hyperextension, - keep femoral head in acetabulum
109
Q

2 reasons why femoral neck fxs more common in women

A
  • osteopenia

- angle of inclination (larger zone of weakness where the trabeculae are not providing support)

110
Q

what are the minimum ROM requirements at the hip for normal gait?

A
  • sagittal plane: 30 deg flexion, 10 deg hyperextension
  • frontal plane: 5 deg abd, 5 deg add
  • transverse plane: 5 dg int, 5 deg ext
111
Q

describe anatomical axis of tibia wrt femur

A

5-10 deg valgus to femur

112
Q

what is the “donation tendon”

A

plantaris

113
Q

role of plantaris

A
  • mostly proprioception

- may help with PF of AJ

114
Q

3 reasons why ankle is less stable in the PF position

A
  • b/c talus wider anteriorly – so when PF, doesn’t fit as tightly into ankle mortise
  • ligaments in best-functioning position when AJ DF
  • AJ pronates and supinates – get inversion with plantarflexion – and this is the position most assoc with lateral ankle lig injuries
115
Q

when is the ankle at its most DF position during gait and why?

A

just before heel off – where most force is passing across the ankle joint, i.e., when tibia passing over foot

116
Q

STJ axis

A

48 deg from frontal
42 deg from transverse
16 deg from sagittal

117
Q

Discuss the spiral of Archimedes

A

as talus rotates on calcaneus, it moves anteriorly as it pronates –> can get sinus tarsi syndrome

118
Q

type of movement of STJ

A

“mitered hinge” – angle of axis will change the planar dominance

119
Q

If STJ axis is deviated to a greater degree than normal from the transverse plane, what would you call this type of STJ?

A

Transverse Planar Dominance – “high axis STJ”

120
Q

LMJA axis

A

75 frontal
15 transverse
9 sagittal

121
Q

OMJA

A

57 sagittal
52 transverse
38 frontal

122
Q

Describe Elftman’s Theory

A
  • as STJ becomes more pronated, the 2 axes of the MTJ become more parallel, increasing the available MTJ ROM possible
  • as the STJ becomes more supinated, the 2 axes become more divergent, causing decreased ROM available at the MTJ
123
Q

Which theory explains how the position of the STJ affects the motion available at the MTJ

A

Elftman’s Theory

124
Q

What are the 3 positions available at the MTJ

A
  • maximally pronated
  • supinated
  • maximally supinated
125
Q

How are the AJ and the MTJ motions related?

A

OMJA = “secondary ankle joint” – when have loss of sagittal motion across the AJ, may be able to get increased sagittal motion in OMJA to compensate as long as STJ is pronated

126
Q

why does FF supinatus develop in foot that functions maximally pronated at the STJ

A

when STJ is maximally pronated, calcaneus is going to be everted –> to get foot to ground, FF (MTJ) is going to supinate –> going to stay like that, causing soft tissue structures to adapt

127
Q

Is it possible for the LMJA to undergo supination while the OMJA is undergoing pronation?

A

yes – as we pronate the STJ, calcaneus everts – the LMJA will then supinate (primarily see inversion) to counteract …. in the same foot, with pronated STJ, going to have relatively flat foot w/ FF dorsiflexing and abducting on RF (OMJA pronation)

128
Q

Direction of axis for 1st ray

A

lateral anterior plantar –> medial posterior dorsal

45 deg from sagittal
45 deg from frontal
9 deg from transverse

129
Q

discuss why the first ray does NOT provide pronation/supination motion

A

b/c of its orientation – as it DF, it inverts – inversion is a component of supination, and dorsiflexion is a component of pronation – therefore, it is not possible

130
Q

discuss the IAR of the 1st MTPJ

A

moves superiorly and posteriorly w/i the 1st MTH w/ DF

131
Q

describe how the 1st MTPJ function is dependent upone normal 1st ray function

A

1st 20-30 deg DF = pure rolling motion
the remaining 35 deg or more of DF occurs as a result of 1st ray PF, allowing base of proximal phalanx to slide up and over 1st met head (i.e., requires 1st ray PF or won’t be able to properly DF)

132
Q

discuss how the 1st ray, the 1st MTPJ, PL, and STJ work together to provide normal function

A

STJ needs to be supinated for proper function of all of the listed structures – if the STJ is pronated, then the lateral side of the foot is higher than the medial, and thus PL loses its plantarflexory pull and cannot PF the 1st ray, which then causes loss of DF function of hallux

133
Q

what are the CKC and OKC functions of the PL

A

OKC: pronates STJ, PF ankle joint and 1st ray
CKC: applies PF moment on the 1st ray but SUPINATORY moment on the STJ

134
Q

what does the jack test demonstrate

A

integrity of the windlass effect

135
Q

How might an uncompensated RF varus effect 1st ray function

A

with calcaneus inverted, increases the PF pull of PL…thus 1st ray will function in a more PF’d position

136
Q

Development of talar adduction

A

starts at 33 deg adducted relative to body of talus – abducts 11 deg relative to body and ends at 22 deg adducted

  • too little change leads to in-toeing (looks like met adductus/FF adductus)
    • too much change leads to out-toeing (not common)
137
Q

Development of Valgus rotation of talar head

A

start with head of talus everted 10 deg relative to transverse plane –> then head undergoes valgus torsion so that normal adult value is 40 deg of valgus!

138
Q

calcaneal frontal ontogeny

A

start at 15-30 deg varus –> end at 0 deg (mirrors the ontogeny of frontal plane bowing of tibia!)

  • too little change–> component of RF varus (calcaneal varus)
    • too much change –> calc valgus (not very likely!) - just like tibial valgum not very common
139
Q

Possible causes of in-toeing

A
  1. Femoral Retroversion
  2. Femoral Antetorsion
  3. Tibial Antetorsion
  4. Too little developmental talar abduction from 33 deg adductus
  5. Metatarsus adductus
  6. Tight Hamstrings
  7. Tight Hip Capsular Ligs – more likely to be tight twd internally rotated position
140
Q

List 4 ontogenous changes that occur in the transverse plane

A
  1. Femoral Version
  2. Femoral Torsion
  3. Tibial Torsion
  4. Talar Adduction
141
Q

List 4 ontogenous changes that occur in the frontal plane

A
  1. Femoral Angle of Inclination
  2. Tibial Bowing
  3. Valgus Rotation of Talar Hea
  4. Calcaneal frontal plane eversion
142
Q

Why do we normally have an abducted angle of gait?

A
  • our knees are normally straight, so primarily due to externally rotated tibial torsion/malleolar position
143
Q

What changes in ontogeny are responsible for getting knee if frontal plane

A
  • femoral version (60 ext –> 10 ext)

- femoral torsion (30 int –> 10 ext)

144
Q

how does intervertebral disc contribute to norma motion

A
  • provide shock absorption (have water in nucleus pulposus)
145
Q

List 3 reasons why the L5S1 segment is most at risk and how it relates to us as podiatrists

A
  • increased lordosis – incr shear forces (L4 sliding forward on L5, L5 sliding forward on S1– then gravity pulling the more anterior segments down)
  • lateral flexion not favored in this area
  • L5/S1 has all of the body weight above it – forces from lower extremity below it – a lot of stress in this area
146
Q

Describe motion that occurs at SI joint

A

nutation and counternutation

  • nutation =anterior sacral tilt and posterior iliac tilt
  • counternutation = posterior sacral tilt and anterior iliac tilt
147
Q

describe ontogeny of tibial plateau in sagittal plane

A

start 30 dg posteriorly tilted – finish at 5 deg posteriorly tilted

  • too little change = genu flexus
    • too much change = genu recurvatum
148
Q

In order for MTJ to be locked and for met heads to bear weight appropriately - how should mets be positioned?

A
  • mets 2-4 should be max DF

- mets 1 and 5 should be in centers of their ROM

149
Q

Ontogeny of Hip angle of inclination

A

(frontal plane)

  • birth: 135-140 deg
  • adult: normal male: 126-128 deg; normal female: 90-125 deg

** the higher the angle, the narrower the hips

150
Q

1st Ray NP calculation

A

DF - PF / 2

151
Q

PL forces on the 1st ray (as a result of its course)

A
  • PL passes lateral and inferior to the cuboid… then passes superiorly and medially to its insertion at the 1st met and medial cuneiform
  • the plantar pull allows the PL to PF the 1st ray (or at least resist DF)
  • also exerts a posterior force that stabilizes the 1st ray against the navicular and a lateral force that stabilizes the 1st ray against the 2nd ray
152
Q

how does STJ pronation affect PL

A
  • STJ pronation –> medial column drops plantarly… which leads to reduced PF moment of the PL on the 1st ray… more pronation leads to less efficient ability of PL to resist DF GRF and leads to unstable 1st ray
  • if the STJ pronates enough to drop the medial column below the level of the cuboid, the PL as it passes around the cuboid will now be dorsal to its insertion – will then pass dorsal lateral to plantar medial and actually apply a DF force on the 1st ray
153
Q

1st Ray Hypermobility

A
  • when the STJ becomes excessively pronated, the PL loses its pull allowing the 1st Ray to DF when it should be stable against the ground
154
Q

Amount of DF of the 1st MTPJ required for gait

A

generally 65 deg or more is required

155
Q

1st MTPJ is what kind of joint for first 20-30 deg

A

ginglymus (rolling)

156
Q

what type of compensation most commonly seen with gastroc equinus

A

knee flexion

157
Q

methods of compensation for equinus

A
  • STJ pronation (allows more DF at the OMJA)
  • abductory twist
  • genu recurvatum/ knee hyperextension
  • knee flexion
  • early heel lift
  • shortened stride length
158
Q

S/sx associated with subtalar pronation for equinus

A
  • Hypermobile 1st ray –> H. limitus or HAV –> transfer pain/callus sub IPJ hallux or sub 2nd met head
  • plantar fasciitis
  • posterior tibial tendon dysfunction
  • HDS
  • increased lordotic curve/low back pain
  • internal rotation of the tibia / patellar femoral syndrome
  • generalized leg fatigue (as muscles trying to hold the foot up in a better position)
159
Q

Describe why abductory twist might occur with equinus

A
  • as the tibia moves over the foot in midstance, the AJ needs to DF – if DF is inadequate, the STJ will pronate – if the STJ pronation is inadequate, the foot may ABDUCT (this occurs by the HEEL MOVING INWARD ON THE FIXED FOREFOOT)
160
Q

s/sx associated with abductory twist

A

diffuse hyperkeratosis at the plantar aspect of met heads 2-4, HAV, achilles tendonitis

161
Q

Describe why genu recurvatum/ knee hyperextension may occur as compensation for equinus

A

if STJ and MTJ are at their end ROM’s, and if knee is still posterior to ankle, then body momentum may still carry torso forward – causing knee to hyperextend

**may be asymptomatic or lead to anterior or posterior knee pain

162
Q

why is shortened stride length a compensation mechanism for equinus

A

b/c by reducing stride length, the amount of AJ DF required will be reduced

** usually associated with tight hamstrings and lower back problems

163
Q

why is knee flexion a compensatory mech for equinus

A

b/c with gastroc equinus, as the knee is flexed, AJ DF will be increased

** this tends to promote hamstring tightness leading to lower back problems

164
Q

If functional orthoses are being given to pt to tx any of the following (plantar fasciitis, posterior tibial tendon dysfunction/tendonities, or functional hallux limitus all as due to overpronation) but if the overpronation is due partly to underlying equinus, then you have to make sure to ID the equinus and address that in the orthoses… what are ways to do so?

A
  • decrease the rigidity of the shell
  • reduce the posting
  • increase the arch fill on the positive
  • heel lift
  • cast slightly pronated

** i.e., have to be able to pronate slightly to compensate for the equinus

165
Q

what kind of rocker indicated for equinus

A

forefoot rocker – will allow the shoe to transfer the pts weight over to the FF, which will then bring the tibia over the FF w/o having to have any ankle joint DF

166
Q

what test = done to assess generalized loss of flexibility (as with DM pts)

A

prayer sign

* we see generalized loss of flexibility everywhere due to glycosylation of everything)

167
Q

in DM neuropathy, which muscle groups lost 1st and 2nd?

A

1st: lose intrinsics –> HDS
2nd: anterior muscle group –> foot drop and equinus as posterior group overpowers

168
Q

Why are those who receive TMAs at increased risk of developing equinus?

A

b/c lose function of anterior muscle groups (long extensors) and possibly deep flexors – posterior superficial muscles overpower –> equinus deformity

169
Q

what should you do if you measure a STJ valgus NP

A

re-measure … it is NOT COMMON to have STJNP in valgus

  • usually really only result of injury
170
Q

compensation for RF varus

A
  • in RF varus, GRF will be at the lateral side of the foot, lateral to the STJ axis – from here, the MTJ will not be able to provide compensation b/c the MTJ will already be maximally pronated – therefore, the STJ will pronate until GRF are equal across the STJ/plantar aspect of the heel/plantar aspect of the foot
  • in ISOLATED RF varus, pronation at the STJ generally occurs until the calcaneus is perpendicular or until end ROM, whichever comes first
171
Q

In order to figure out compensation (RCSP) for any of the frontal plane FF and RF deformities, what MUST you know and/or figure out?

A
  • STJ inversion and eversion
  • STJNP
  • Tibial Influence
  • Maximally pronated stance position
  • Where fully compensated would be
172
Q

Maximally pronated stance position

A
  • NOT RCSP!
  • can be determined using tibial influence and STJ eversion

Equation = TI - STJ Eversion

173
Q

order of compensation for RF valgus

A
  • most commonly due to genu valgum = note
  • GRF will be on medial side of the foot, medial to MTJ and STJ axes, providing an external supinatory moment –> the LMJA will be able to supinate 4-6 deg (end ROM) to compensate –> if the RF valgus is greater than 4-6 deg, the STJ may also supinate –> if still not enough, may go back to OMJA
174
Q

As a general rule: any deformity that puts the STJ in an everted position of greater than _________ deg will force the STJ to go to end range of pronation

A

5 deg

175
Q

What is likely to develop with prolonged LMJA supination as a result of RF valgus compensation

A

forefoot supinatus (no longer locked and stable – ST adaptation becomes rigid)

176
Q

3 anti-pronation modifications

A
  • kirby skive
  • blake inverted pour
  • extended medial heel post
177
Q

Gait changes seen with Isolated RF Varus

A
  • heel strike will be inverted; the STJ will then pronate to rectus or end ROM, whichever comes first
  • significant increase in lateral loading is likely
  • medial loading may occur by PF of the medial column if inadequate STJ pronation is available to get the medial side of the foot to the ground
178
Q

Callus Patterns associated with Isolated RF Varus

A
  • sub 4th and 5th MTH’s as a result of increased lateral loading
  • may see sub 5th met base HPK if the RF varus is uncompensated or minimally compensated
  • may see sub 1st MTH as a result of compensatory PF of 1st ray (if calcaneus is in significant amount of varus, PL has a more efficient pull – pulls down 1st met and may see incr loading there)

** callus pattern is seen based on degree of compensation

179
Q

Shoe gear pattern with Isolated RF varus

A
  • increased wear at lateral heel

- may have increased wear at 5th met base or 5th and 5th met heads

180
Q

Pathologies associated with Isolated RF varus

A
  • H. Limitus (b/c pronating, but not pronating past perpendicular, i.e., not everting, the PL still maintains its pull, particularly laterally – the first ray tends to remain in fairly stable transverse plane position – why develops H. Limitus rather than HAV)
  • Tailor’s Bunion (due to increased loading on the lateral column, GRF may force the 5th ray into a more DF position w/ incr. stress on the 5th MTH)
  • Haglund’s Deformity (usually associated with increased frontal plane motion of the calcaneus around a relatively inverted calcaneal position – posterior dorsal lateral corner of the calcaneus remains prominent)
  • HDS (more likely to just be 4th and 5th digits as a result of lateral column dorsiflexion for compensation)
181
Q

Compensation for RF Varus/FF Valgus

A
    • depends on the severity of the RF varus and the FF valgus
  • if they are equal – no further compensation required
  • if FF valgus > FF varus – LMJA will supinate
  • if FF valgus more than 5 > RF varus – both LMJA and STJ will be required to supinate
  • if FF valgus
182
Q

Angle of Declination of Femur

A
  • AKA Femoral Torsion
  • structural angle of femur
  • one line bisecting the femoral condyles and another bisecting the neck of the femur
  • adults: 10˚ internally rotated
  • newborn: 30˚ internally rotated
183
Q

Angle of Anteversion

A
  • AKA Femoral Version
  • angle formed by neck of femur and the transverse plane
  • newborn: 60˚ external
  • adult: 10˚ external

**Retroversion: angle of less than 10˚ external, indicating greater than normal versional change (may cause in-toeing)

184
Q

Ontogeny of Tibial Bowing

A

Newborn: 15-30˚ varus
Adult: 0-2˚ varus

185
Q

Ontogeny of Tibial Torsion

A

Newborn: 0˚
Adult: 18-23˚

Malleolar position: 0˚ at birth, 13-18˚ external for adults; thus, clinically we use 15-20˚ as normal

186
Q

Compensation for Isolated FF Valgus

A
  • LMJA supinates 5 deg
  • then STJ supinates 5 deg
  • then OMJA supinates 5 deg
  • then back to STJ if necessary
187
Q

What condition is circumducted gait associated with?

A

Spastic hemiplegia (e.g. stroke)

188
Q

Ankle joint axis

A

S: 82˚
T: 8˚
F: 20-30˚

189
Q

Subtalar joint axis

A

F: 48˚
S: 16˚
T: 42˚

190
Q

Dorsiflexed 1st Ray

A

Rigid: unable to PF below lesser mets
Flexible: able to PF below lesser mets
Congenital: normal or greater than normal ROM
Acquired: less than normal ROM

191
Q

Compensation for valgus deformities

A

LMJA Supination: first 5˚
STJ Supination: next 5˚
OMJA Supination: next 5˚
STJ Supination: anything more

192
Q

Forefoot varus vs Forefoot Supinatus

A

FF varus: congenital, bony, primary

FF supinatus: acquired, ST, secondary

193
Q

Dorsiflexed 1st ray

A
  • deformity in which the first ray has more DF than PF available so that the neutral position of the 1st ray is DF
  • can be defined as flexible or rigid:
    1. rigid DF 1st ray: unable to PF below the plane of the lesser mets
    2. flexible DF 1st ray: able to PF below the level of the lesser mets
  • can also be defined as congenital or acquired:
    1. congenital DF 1st ray: has normal or greater ROM, but is dorsally displaced
    2. acquired DF 1st ray: has less than normal ROM and it is dorsally displaced (total ROM
194
Q

How does a DF 1st ray compensate?

A
  • UNLIKE a plantarflexed 1st ray, a DF’d 1st ray does NOT compensate for itself – it acts like a FF varus, requiring STJ pronation
195
Q

How to compensate for isolated FF varus

A

STJ pronation – will pronate until the GRF is equal across the plantar aspect of the foot (if 5 deg, the talus will be so far adducted and PF relative to the calcaneus that the STJ will go to end range of pronation!)

196
Q

Compensation for Isolated FF Valgus

A
  • LMJA supinates 5 deg
  • then STJ supinates 5 deg
  • then OMJA supinates 5 deg
  • then back to STJ if necessary
197
Q

Flexible (Mobile) FF Valgus

A

the deformity is compensated completely by supination at the LMJA ( a FF valgus of 5 deg or less)

** note, STJ supination causes foot to become more rigid… so if don’t need STJ supination, considered FLEXIBLE

    • additional compensations that may occur before STJ supination =
  • DF of the 1st ray to raise the 1st met head up to the level of the 2nd met
  • DF at the 3 cuneiform-navicular articulations to raise the medial column (met heads 1-3) up to level of 4th met head
  • PF of the 5th ray
198
Q

Rigid FF Valgus

A

deformity requires additional compensatory supination at the STJ (and possibly the OMJA) (a FF valgus deformity of >5 deg)

199
Q

Caviat of Flexible FF Valgus

A
  • the LMJA will likely go to END RANGE of supination when compensating for FF valgus (overcompensation…) – this requires STJ to pronate to make up for overcompensation in varus dxn
200
Q

Isolated PF 1st ray compensation

A
  • initial compensation likely to DF the 1st Ray
  • if the 1st ray can DF up to the level of the lesser met heads, the PFFR is said to be FLEXIBLE, and no other compensation required
  • if the 1st ray ROM does NOT provide DF up to level of the lesser met heads, the LMJA will be required supinate (ie. RIGID PFFR) –** remember that the LMJA will likely go to end range of motion and may likely result in STJ pronation
201
Q

For every 1 deg STJ pronation, the MTJ everts _____ deg?

A

1.2 deg

202
Q

A pt presents with 8 deg RF varus – his RCSP is 2 deg inverted… why?

A

the patient pronates until the medial side of the foot hits the ground – as he pronates the STJ, increased eversion is available at the MTJ which may allow the medial side of the foot to hit the ground before the RF gets to rectus

203
Q

Explain why the following is true: the 1st ray may be able to PF to compensate for some varus deformities (particularly RF varus deformities)

A

if the RF is in inverted position, the PL will have a more effective lever arm to apply greater internal PF moment on the 1st ray

204
Q

UCBL stands for what

A

university california berkley lab

205
Q

Types of Adult Orthoses

A
  • UCBL
  • pronated
  • Schaffer Plate
  • Neutral shell
  • Accomodative
  • Functional
206
Q

Types of Pediatric Devices

A
  • Heel Stabilizers (A-E) (2-7 yrs)
  • Whitman (all below = 7-12 yrs)
  • Roberts
  • Whitman-Roberts
  • Reverse Roberts

** all cast rectus

207
Q

purpose of functional orthoses

A
  1. prevent compensation
  2. allow the STJ to function around NP
  3. promote the normal timing of gait cycle
  4. to change/improve function
208
Q

5 things you need in orthotic Rx

A
  1. type of orthosis
  2. casting technique
  3. materials
  4. posting
  5. modifications
209
Q

blake inverted pour to what degree inversion

A

25-45 deg inverted on positive

210
Q

Kirby skive - how much to skive off?

A

2-4 mm off positive

211
Q

List all materials made out of polyethylene

A
  • sub-o
  • orthelon
  • alliplast
  • Plastizotes #1-3
212
Q

List materials that you can use for all parts of orthotic

A
  • EVA

- cork

213
Q

Materials that you would ONLY use for shell material

A
  • polypropylene
  • subo
  • # 3 plastizote
214
Q

Human ST replacements (3)

A
  • PPT/poron
  • # 1 plastizote
  • sphinco

ALL 15-20 DUROMETER

215
Q

most common posting material

A

EVA

Boards/Interviews (10 decks)

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