chapter 3 and 3a introduction to orthopedics and bio mechanics

8/2/2019 Chapter 3 and 3a Introduction to Orthopedics and Bio Mechanics

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3 Orthopedics

C o n t e n t s

3.1 Biomechanics . . . . . . . . . . . . . . . . . . . . . . . . 50

by Justin Wernick, DPM

3.2 Common Orthopedic Pathologies of the

Foot and Ankle. . . . . . . . . . . . . . . . . . . . . . . 107

by Steve Levitz, DPM and

Justin Wernick, DPM

3.3 Neuromuscular Disease and Electrodiagnosis 119

by Ellen Sobel, DPM

3.4 Orthotics and Prosthetics . . . . . . . . . . . . . . 139

by Ellen Sobel, DPM and

Lauren Jones, DPM

3.5 Pathological Gait . . . . . . . . . . . . . . . . . . . . . 161

by Aaron Glockenberg, DPM

3.6 Pathomechanics . . . . . . . . . . . . . . . . . . . . . 169

by Justin Wernick, DPM

3.7 Physical Medicine . . . . . . . . . . . . . . . . . . . . 205

by Loretta Logan, DPM and

Carl Harris, DPM

3.8 Sports Medicine . . . . . . . . . . . . . . . . . . . . . 225

by Josh White, DPM and

Lauren Jones, DPM

Orthopedics 49


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3.1 Biomechanics

Justin Wernick, D.P.M.

Introduction

Biomechanics is the study of the structure and function of the biological systems by means of the methods of

mechanics.

ASB,1975

Body Planes

50 The 2005 Podiatry Study Guide


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Dorsiflexion

A movement on the sagittal plane where the distal part of the foot or segments of the foot moves toward the

anterior of the leg.

Position

Dorsiflexed

Calcaneous

Plantarflexion

A movement on the sagittal plane where the distal part of the foot or segments of the foot moves away from the

anterior of the leg.

Position

Plantarflexed Equinus

Orthopedics | Biomechanics 51


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Closed Chain Sagittal Plane Movement of the Leg on the foot

Closed Chain Sagittal Plane Motion Dorsiflexion



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Closed Chain Sagittal Plane Motion Plantarflexion

Midline of the Foot

The body midline is used as the reference.



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Abduction

A movement on the transverse plane where the distal part of the foot or segments of the foot moves away from

the midline of the body.

Adduction

A movement on the transverse plane where the distal part of the foot or segments of the foot moves towards the

Position

Abducted



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Eversion

A movement on the frontal plane where the plantar surface of the foot or segments of the foot faces away from

the midline of the body.

Position

Everted

Valgus



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Inversion

A movement on the frontal plane where the plantar surface of the foot or segments of the foot faces toward the

midline of the body.

Position

Inverted

Varus



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Functional Definitions

Upper segment => Talus and the leg

Lower segment => Calcaneus and the foot

Rearfoot => Talus and the calcaneus

Forefoot => Distal to the MT joint

Hypermobility

Hypermobility implies instability and is defined as movement of a segment or part that should be fixed and

stable when stress is applied.

Abnormal Compensation

An abnormal change of structure, position, or function of one part in an attempt by the body to neutralize the

effects of a deviation of structure, position, or function of another part.

The results are pathological.

Daily Stress

Walking and standing on a hard, unforgiving surface + Number of steps taken each day + Average body

weight = The amount of force the feet and body are exposed to each day

Average number of steps taken each day(10,000) X Average body weight (150 lbs) = The amount of force the

feet and body are exposed to each day (1,500,000 lbs!)

Axis

The axis is an imaginary line passing through the center of a body about which a rotating body turns; synonymous

with an axle.



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Axis of Motion

The hinge around which motion takes place. The motion is always perpendicular to the plane or planes in

which the axis is placed.

The Foot is Predictable

The primary joints of the foot are hinge joints with one axis, and therefore will react in one direction or the

other!



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Triplane Motion

A motion-taking place, consisting of three components where the axis of the motion makes an angle to all

three-body planes.

Pronatory/Supinatory Axes

A pronatory/supinatory axis is directed from posterior, lateral, inferior to dorsal, medial, anterior.



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Triplane Motion

Components of the motion

Planal Dominance

The determination of a motion at a given joint based upon the orientation of the axis.

Planal dominance of the individual foot is important to the evaluation of the function of the foot. The direc-

tion in which an individual foot can compensate is important.

The primary plane of compensation and the amount of available range are important considerations when

evaluating foot function.

Green,D.,Carol,A., Planal Dominance, JAPA,Vol.74, #2

Planal Dominance of the Joints of the Foot

Deviations of the axis from the body planes will determine which component will be dominant at each joint.



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Even in our everyday attempts to control the variety of foot types seen in our offices, planal dominance can

play a major part in our success.

Green,D.,Carol,A., Planal Dominance, JAPA,Vol.74, #2

General Rules

After a thorough assessment of the patient, determine on which body plane(s) the pathologic influence is

taking place

Then determine which joints the pathological influence will select to compensate for the influence. It will be

the joints with the largest component in that body plane

Determine if there is an adequate range of motion in the joint(s) selected to fully compensate for

the influence

Open Chain Motion

A combination of several joints united successfully where the end segment is free! As during the swing phase

of gait.



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Open Chain Pronation

With the leg and talus held stable, the calcaneus and the foot will undergo eversion, abduction, and dorsiflexion.

Open Chain Supination

With the leg and talus held stable, the calcaneus and the foot will undergo inversion, adduction, and

plantarflexion.



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Closed Chain Motion

A combination of several joints united successfully where the end segment is not free! As during the stance

phase of gait.



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Subtalar Joint Closed Chain Pronation

Adduction and plantarflexion of the talus associated with internal rotation of the leg

Eversion of the calcaneus

Flexion of the knee

Anterior tilt of the pelvis

Subtalar Joint Closed Chain Supination

Abduction and dorsiflexion of the talus associated with external rotation of the leg

Inversion of the calcaneus

Knee extension

Posterior tilt of the pelvis



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Criteria for Normal Function of the Foot

A basis by which we measure to determine if a patient is functioning normally or abnormally

The appropriate functional alignment for the foot and leg during the stance phase of gait

Neutral Position of the Subtalar Joint

The neutral position is a position of the subtalar joint where the joint is congruent and a bisection of the lower

one-third of the leg creates an angle of zero to four degrees with the bisection of the posterior surface of the

calcaneus.

Forefoot/Rearfoot Relationship

The forefoot/rearfoot relationship is represented by the transverse plane of the lesser metatarsal heads (2-4)

being perpendicular to the calcaneal bisection when the subtalar joint is in neutral and the midtarsal joint is maxi-

mally pronated.



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Sagittal Plane Motion of the Ankle

Sagittal plane motion of the ankle is represented by approximately 10 degrees of dorsiflexion that is required at

the ankle joint with the subtalar joint neutral and the knee fully extended. Measured as a angle between the proxi-

mal heel and the lower one-third of the lateral surface of the leg.

Frontal Plane Function of the Leg

There shall be no deviation (+/- 2) of the leg above in the frontal plane as it enters the foot when the subtalar

joint is in neutral position.



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Sagittal Plane Function of the Leg.

There shall be no deviation (+\-2) of the leg in the sagittal plane as it enters the foot when the subtalar joint is

in neutral position.

Transverse Plane Function of the Leg

There shall be no deviation (+\-2) of the leg in the transverse plane as it enters the foot when the subtalar joint

is in neutral position.



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When the Foot hits the Ground, Everything Changes!

Muscle pull reverses itself and functions from its insertion to its origin

Range of motion of the joints will decrease from its off weight bearing position

Extrinsic factors play a dominant role in influencing foot function

Movement of the center of gravity is instrumental in stabilizing specific segments of the foot

Subtalar Joint

A pronatory/supinatory axis whose motion will appear clinically as:

Eversion/abduction of the rearfoot with pronation

Inversion/adduction of the rearfoot with supination




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High-Pitched Subtalar Joint Axis--Increase in Adduction-Abduction

Low-Pitched Subtalar Joint axisIncreased Inversion-Eversion

Conversion of Rotation at the HipRotation at the hip joint is converted to motion at the subtalar joint via a system similar to a universal joint.



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Rotation at the subtalar joint converts transverse plane motion to frontal plane motion via a mitered hinge

Effects of Leg Rotation on the Foot

Four degrees to six degrees of subtalar joint pronation is required to expedite internal rotation

Internal rotation of the leg results in pronation of the subtalar joint!

External rotation results in supination!

Effects of Friction

Friction enhances sagittal plane walking by converting internal and external rotation at the hip to pronation

and supination at the subtalar joint.



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Subtalar Joint

On closed chain, the motion will appear clinically as:

Eversion of the calcaneus with pronation

Inversion of the calcaneus with supination



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Subtalar Joint Pronation Closed Chain



Flexion of the knee


Subtalar Joint Closed Chain Pronation



Flexion of the knee




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Subtalar Joint Supination Closed Chain



Knee extension




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Subtalar Joint Closed Chain Supination



Knee extension


Effects of Subtalar Joint Motion on the Architecture of the Foot

The range of motion of the distal joints will increase with subtalar joint pronation and decrease with subtalar

joint supination.



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General Effects

The average range of motion of the subtalar joint has been found to be approximately 25 - 30. The ratio of

supination to pronation is usually 2:1 but may be 4:1.

Pronation

Supination



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Neutral Position

Definitions

A position of a joint from which maximum function may occur in any of the permissible directions.

A position where the joint is neither supinated nor pronated and the body of the talus is in line with the

body of the calcaneus.

Neutral Position Subtalar Joint Congruency



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Subtalar Neutral Position

Axis of the subtalar joint is a hinge that results in an arc like motion

Supination in one direction, pronation in the other



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The Ankle Joint


A pronatory / supinatory axis whose motion will appear clinically as:

Dorsiflexion and abduction with pronation

Plantarflexion and adduction with supination



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Ankle Joint Function

Expedites forward movement of the body over the foot

Compliments the pull of the swing limb with a push-off of the support limb

Adapts to situations where there is a limitation or lack of motion in the subtalar joint

Provides the sagittal plane component to the rearfoot

The Midtarsal Joints


Planal Dominance of the Longitudinal Midtarsal Joint Axis



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The Midtarsal Joint Longitudinal Axis


Eversion of the forefoot with pronation

Inversion of the forefoot with supination



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Pronation of the rearfoot with supination of the forefoot

Supination of the rearfoot with pronation of the forefoot

Forefoot/Rearfoot Functional Relationships

Supination of the forefoot is: relative pronation of the rearfoot

Pronation of the forefoot is: relative supination of the rearfo



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Range of motion

The average range of Motion of the longitudinal MT Jt is 22. Pronation of the subtalar joint requires 4 - 6

of complimentary supination of the forefoot.

There is only supination available when the subtalar joint is neutral.

Effects of Rearfoot Function on the Midfoot

Subtalar Joint Pronation => Unlocks Midfoot => Longitudinal Axis MT Joint Supination

Subtalar Joint Supination => Locks Midfoot => Longitudinal Axis MT Joint Pronation

The Oblique Axis Midtarsal Joint


Dorsiflexion/abduction of the forefoot with pronation

Plantarflexion/adduction of the forefoot with supinatio




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An increase in the pitch of the calcaneus will increase the transverse plane component.



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An increase in internal rotation of the leg will increase the sagittal plane component.



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Midtarsal Joint Oblique Axis


Dorsiflexion/abduction of the rearfoot with forefoot supination

Plantarflexion/adduction of the rearfoot with forefoot pronation



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Closed Chain Pronation

Apparent forefoot abductus

cuboid notch

Too many toes syndrome

Foot rolling out from under the leg

Apparent tibia varum


Forefoot



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Effects of Rearfoot Function on the Midfoot

Subtalar Joint Pronation => Unlocks Midfoot => Oblique Axis MTJt. Pronation

Subtalar Joint Supination => Locks Midfoot => Oblique Axis MTJt. Supination

Pillars of the foot

The medial pillar (column) is the adaptive or spring-like structure, and the lateral pillar (column) is the stabile

structure.

The 1st Ray

Axes of Motion

The axis of the 1st ray is deviated 45 from the sagittal and frontal planes. The major components of

the motion are: Plantarflexion with eversion

Dorsiflexion with inversion


Joint Motions that Affect Arch Morphology

Joint involved Raise the arch Lower the arch

Subtalar Jt. No effect No effect

Long. MT Jt Pronation Supination

Oblique MT Jt. Supination Pronation

1st Ray Plantarflexion Dorsiflexion


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Components



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Range of Motion

The 1st ray has a range of motion of 5 mm dorsally and 5 mm plantarly for a total range of 10 mm.

Stabilization of the 1st Ray

The peroneus longus muscle functions to:

Compress the tarsus in concert with the posterior tibial muscle

Stabilize the 1st ray both posterior and lateral

Resist the ground reaction forces from dorsiflecting the 1st ray



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Requirements for Proper Function of the 1st Ray

Subtalar joint supination

Stable midtarsal joint

Heel lift

Posterior movement of the 1st metatarsal head on the sesamoids

A second metatarsal that is longer then the first

Effect of Supination of the Subtalar Joint on the First Ray.

Effect of Pronation of the Subtalar Joint on the First Ray.



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The 1st MP Joint

Anatomy

Together they create a dynamic acetabulum.

Osseous structures

Head of the first metatarsal

Base of the proximal phalanx Medial and lateral sesamoids

Capsule

Muscle attachments



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Axes of Motion

IRolling motion

II, IIISliding motion associated with 1st ray plantarflexion

IVCompression



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Design and Function of the 1st Metatarsal Head

Since the design of the head is in the shape of a cam, rolling of the head and then sliding is expedited.

Demand for Dorsiflexion at the 1st MP Joint

The average range of motion is 55 to 85.

During the propulsive phase of gait, the demand for dorsiflexion at the MP joints is the result of :

Hip extension

Knee flexion

Ankle plantarflexion

As the 1st ray plantarflexes, it slides plantarly in relationship to the base of the proximal phalanx.



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Once the heel has lifted maximally, the 1st ray will fully compress against the base of the proximal phalanx.

The range of motion available at the 1st MP joint weight bearing is approximately 20 . This is consistent with

the rolling segment of the motion.



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Requirements for Essential Motion at the 1st MP Joint

1st ray plantarflexion

2nd metatarsal longer then the 1st

Normal intrinsic and extrinsic muscle function

Normal sesamoid function

Intact base of the proximal phalanx

Functional Hallux Limitus

A blockage of motion at the 1st metatarso-phalangeal joint during walking, resulting in the inability of the

proximal portion of the foot to pass over the toes

Limitation may occur in spite of a normal range of motion off-weight bearin

This will result in some form of compensation to occur in the foot , limb and/or back and neck



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Factors that Block Sagittal Plane Motion at the 1st MP Joint

Elevation of the 1st ray

Forefoot valgus/plantarflexed 1st ray

Rearfoot and forefoot instability Abnormal muscle function

Long 1st metatarsal

Degeneratve joint disease

Arthritides



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Elevatus of the 1st Ray Secondary to Pronation of the Rear Foot at Propulsion


Compensations for sagittal plane blockade of the 1st MP joint

Intrinsic compensations

Dorsiflexion of the IP joint with medial roll-off

Inverted forefoot at propulsion. (Low gear) Abducted gait

S.A.R.P. (Secondary Active Retrograde Pronation)

Hallux abducto-valgus deformity

Extrinsic compensations


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Elevatus of the 1st Ray Secondary to a Long 1st Ray

Inverted Forefoot at Propulsion



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Secondary Active Retrograde Pronation (S.A.R.P.)

Compensations for Sagittal Plane Blockade of the 1st MP Joint

Extrinsic compensations

Flexion at the hip

Neck and shoulder flexion

Tempro -Mendibular Jt. complications

Flexion Contracture Compensation for Functional Hallux Limitus



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Examination for Functional Hallux Limitus

The range of motion available at the 1st MP joint on weight bearing is approximately 20 . This is consistent

with the rolling segment of the motion.

A lack of this motion is indicative of a functional hallux limitus.

Primary Passive Propulsive Phase Supination Windlass Mechanism

Heel lift with ankle plantarflexion will dorsiflex the MP joints

This will tighten the plantar fascia, raise the arch, and shorten the foot

Raising the arch will resist elongating the foot and assist in resupinating the subtalar joint



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Kinetic Wedge

Problem: Functional Hallux Limitus (FHL)

Dorsiflexion of the 1st ray at propulsion

Compensation causes foot symptoms

Compensation causes postural symptoms

Solution: Induce Plantarflexion-eversion of the 1st Ray

Dual angle cutout at the 1st MP joint

Parallels the 1st ray axisinduces plantarflexion and eversion of the 1st ray

Parallels the 1st MP joint axisassists hallux dorsiflexion and 1st ray plantarflexion

Bi-directional shell cutout to permit plantarflexion

Hallux extension to increase hallux purchase

Summary

The 1st ray is required to plantarflex and evert during the heel lift stage of walking

Motion at the 1st metatarso-phalangeal joint consists of rolling, sliding with compression at the end range

Factors that cause an elevatus of the 1st ray to occur will block motion and create a functional hallux limitus

Intrinsic and extrinsic compensations for this sagittal plane blockade will occur



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The 5th Ray

5th Ray Axis


Dorsiflexion and eversion of the ray with pronation

Plantarflexion and inversion of the ray with supination



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Dorsiflexion/abduction of the 5th ray

Plantarflexion/adduction of the 5th ray



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GAIT

GENERAL CONCEPTS

2 periods of double support (25%)

2 periods of single support (75%)

0 - heel strike

7% - footflat 12% toe-off of opposite limb

15% full heel eversion occurs

34% heel rise

50% heel strike of opposite limb

62% toe-off (reswing)

Heel rise occurring before 34% = Gastroc spasticity

Footflat not occurring by 7% = Gastroc spasticity

Heel rise occurring later than 34% = Gastroc weakness

TERMINOLOGY NEW VERSUS THE OLD

Contact Phase

Heel strike ..................Initial contact

Footflat.......................Load response

Midstance...................Single leg stance

Propulsion

Heel-off .....................Terminal stance

Toe-off........................Preswing

GAIT CYCLE

STANCE PHASE

CONTACT (0-15%) HEEL STRIKE TO FOOTFLAT CALCANEUS everts (passively) maximum to 15%

Entire lower extremity internally rotates

ANKLE JOINT plantar flexes to ~20%

KNEE flexes 15-20o

HIP flexes

QUADRICEP (L2,3,4) contract eccentrically to stabilize knee and prevent buckling

GLUTEUS MAXIMUS acts as break preventing too much truck flexion

ANTERIOR LEG MUSCLES (L4) contract eccentrical slowing down ankle joint plantarflexion

MIDSTANCE (15-34%) FOOTFLAT TO HEEL OFF

CALCANEUS inverts

EXTERNAL ROTATION initiated by contralateral swing limb

ANKLE JOINT dorsiflexes to 20

KNEE extends

HIP extends

GLUTEUS MEDIUS (L5) holds pelvis down on stance side

ERECTOR SPINAE and HIP ADDUCTORS contract to hold swing leg up

CALF MUSCLES eccentrically contract to control ankle joint dorsiflexion



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PROPULSION (34-60%) HEEL-OFF TO TOE-OFF

CALCANEUS inverts

EXTERNAL ROTATION of stance limb continues

ANKLE JOINT plantarflexes ~20

KNEE flexes to 40

HIP flexes

CALF MUSCLES (S1, S2) concentrically plantarflex calf

SWING PHASE

INITIAL SWING (ACCELERATION)

CALCANEUS everts (STJ pronates)

Internal rotation of the leg

ANKLE JOINT dorsiflexes to clear ground

KNEE flexes to 60

HIP flexes

ILEOPSOAS initiates swing phase of gait

ANKLE DORSIFLEXORS concentrically contract for foot to clear ground

MIDSWING

Swing leg is adjacent to weight-bearing leg

Internal rotation of leg continues

KNEE flexes 60

HIP flexes

TERMINAL SWING (DECELERATION)

CALCANEUS inverts

INTERNAL ROTATION of leg continues

ANKLE JOINT remains dorsiflexed to 90

KNEE extends

HIP extends GLUTEUS MAXIMUS slows down swinging limb

HAMSTRINGS control hip flexion and also slow down swinging leg

QUADRICEPS control knee extension

chapter 3 and 3a introduction to orthopedics and bio mechanics

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