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Transcript of Introduction to Orthopedics and Bio Mechanics.pdf
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
3.1 BiomechanicsJustin Wernick, D.P.M.
IntroductionBiomechanics 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
DorsiflexionA 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
PlantarflexionA 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
Closed Chain Sagittal Plane Movement of the Leg on the foot
Closed Chain Sagittal Plane Motion Dorsiflexion
52 The 2005 Podiatry Study Guide
Closed Chain Sagittal Plane Motion Plantarflexion
Midline of the Foot
The body midline is used as the reference.
Orthopedics | Biomechanics 53
AbductionA 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.
AdductionA movement on the transverse plane where the distal part of the foot or segments of the foot moves towards the
Position
• Abducted
54 The 2005 Podiatry Study Guide
EversionA 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
Orthopedics | Biomechanics 55
InversionA 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
56 The 2005 Podiatry Study Guide
Functional DefinitionsUpper 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.
Orthopedics | Biomechanics 57
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!
58 The 2005 Podiatry Study Guide
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.
Orthopedics | Biomechanics 59
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.
60 The 2005 Podiatry Study Guide
“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.
Orthopedics | Biomechanics 61
Open Chain PronationWith the leg and talus held stable, the calcaneus and the foot will undergo eversion, abduction, and dorsiflexion.
Open Chain SupinationWith the leg and talus held stable, the calcaneus and the foot will undergo inversion, adduction, and
plantarflexion.
62 The 2005 Podiatry Study Guide
Closed Chain MotionA combination of several joints united successfully where the end segment is not free! As during the stance
phase of gait.
Orthopedics | Biomechanics 63
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
64 The 2005 Podiatry Study Guide
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.
Orthopedics | Biomechanics 65
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.
66 The 2005 Podiatry Study Guide
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.
Orthopedics | Biomechanics 67
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 JointA pronatory/supinatory axis whose motion will appear clinically as:
• Eversion/abduction of the rearfoot with pronation
• Inversion/adduction of the rearfoot with supination
Planal Dominance of the Joints of the Foot
68 The 2005 Podiatry Study Guide
High-Pitched Subtalar Joint Axis--Increase in Adduction-Abduction
Low-Pitched Subtalar Joint axis—Increased 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.
Orthopedics | Biomechanics 69
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 FrictionFriction enhances sagittal plane walking by converting internal and external rotation at the hip to pronation
and supination at the subtalar joint.
70 The 2005 Podiatry Study Guide
Subtalar JointOn closed chain, the motion will appear clinically as:
• Eversion of the calcaneus with pronation
• Inversion of the calcaneus with supination
Orthopedics | Biomechanics 71
Subtalar Joint Pronation Closed Chain
• 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 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
72 The 2005 Podiatry Study Guide
Subtalar Joint Supination Closed Chain
• Abduction and dorsiflexion of the talus associated with external rotation of the leg
• Inversion of the calcaneus
• Knee extension
• Posterior tilt of the pelvis
Orthopedics | Biomechanics 73
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
Effects of Subtalar Joint Motion on the Architecture of the FootThe range of motion of the distal joints will increase with subtalar joint pronation and decrease with subtalar
joint supination.
74 The 2005 Podiatry Study Guide
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
Orthopedics | Biomechanics 75
Neutral PositionDefinitions
• 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
76 The 2005 Podiatry Study Guide
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
Orthopedics | Biomechanics 77
The Ankle JointPlanal Dominance of the Joints of the Foot
A pronatory / supinatory axis whose motion will appear clinically as:
• Dorsiflexion and abduction with pronation
• Plantarflexion and adduction with supination
78 The 2005 Podiatry Study Guide
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 JointsPlanal Dominance of the Joints of the Foot
Planal Dominance of the Longitudinal Midtarsal Joint Axis
Orthopedics | Biomechanics 79
The Midtarsal Joint Longitudinal Axis
A pronatory/supinatory axis whose motion will appear clinically as:
• Eversion of the forefoot with pronation
• Inversion of the forefoot with supination
80 The 2005 Podiatry Study Guide
On closed chain, the motion will appear clinically as:
• 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
Orthopedics | Biomechanics 81
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
A pronatory/supinatory axis whose motion will appear clinically as:
• Dorsiflexion/abduction of the forefoot with pronation
• Plantarflexion/adduction of the forefoot with supinatio
Planal Dominance of the Joints of the Foot
82 The 2005 Podiatry Study Guide
Planal Dominance of the Joints of the Foot
An increase in the pitch of the calcaneus will increase the transverse plane component.
Orthopedics | Biomechanics 83
An increase in internal rotation of the leg will increase the sagittal plane component.
84 The 2005 Podiatry Study Guide
Midtarsal Joint Oblique Axis
On closed chain, the motion will appear clinically as:
• Dorsiflexion/abduction of the rearfoot with forefoot supination
• Plantarflexion/adduction of the rearfoot with forefoot pronation
Orthopedics | Biomechanics 85
Closed Chain Pronation
• Apparent forefoot abductus
• cuboid notch
• “Too many toes syndrome”
• Foot rolling out from under the leg
• Apparent tibia varum
Planal Dominance of the Joints of the Foot
Forefoot
86 The 2005 Podiatry Study Guide
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 RayAxes of Motion
The axis of the 1st ray is deviated 45º from the sagittal and frontal planes. The major components of
the motion are:
• Plantarflexion with eversion
• Dorsiflexion with inversion
Orthopedics | Biomechanics 87
Joint Motions that Affect Arch MorphologyJoint involved Raise the arch Lower the archSubtalar Jt. No effect No effectLong. MT Jt Pronation SupinationOblique MT Jt. Supination Pronation1st Ray Plantarflexion Dorsiflexion
Components
88 The 2005 Podiatry Study Guide
Planal Dominance of the Joints of the Foot
Orthopedics | Biomechanics 89
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
90 The 2005 Podiatry Study Guide
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.
Orthopedics | Biomechanics 91
The 1st MP JointAnatomy
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
92 The 2005 Podiatry Study Guide
Axes of Motion
• I—Rolling motion
• II, III—Sliding motion associated with 1st ray plantarflexion
• IV—Compression
Orthopedics | Biomechanics 93
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.
94 The 2005 Podiatry Study Guide
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.
Orthopedics | Biomechanics 95
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
96 The 2005 Podiatry Study Guide
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
Orthopedics | Biomechanics 97
Elevatus of the 1st Ray Secondary to Pronation of the Rear Foot at Propulsion
98 The 2005 Podiatry Study Guide
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
Elevatus of the 1st Ray Secondary to a Long 1st Ray
Inverted Forefoot at Propulsion
Orthopedics | Biomechanics 99
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
100 The 2005 Podiatry Study Guide
Examination for Functional Hallux Limitus
The range of motion available at the 1st MP joint on weight bearing is approximately 20º . 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
Orthopedics | Biomechanics 101
Kinetic WedgeProblem: 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 axis—induces plantarflexion and eversion of the 1st ray
• Parallels the 1st MP joint axis—assists 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
102 The 2005 Podiatry Study Guide
The 5th Ray5th Ray Axis
A pronatory/supinatory axis whose motion will appear clinically as:
• Dorsiflexion and eversion of the ray with pronation
• Plantarflexion and inversion of the ray with supination
Orthopedics | Biomechanics 103
Planal Dominance of the Joints of the Foot
On closed chain, the motion will appear clinically as:
• Dorsiflexion/abduction of the 5th ray
• Plantarflexion/adduction of the 5th ray
104 The 2005 Podiatry Study Guide
GAITGENERAL 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 OLDContact Phase
Heel strike ..................Initial contact
Footflat .......................Load response
Midstance...................Single leg stance
Propulsion
Heel-off .....................Terminal stance
Toe-off ........................Preswing
GAIT CYCLESTANCE 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
Orthopedics | Biomechanics 105
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
106 The 2005 Podiatry Study Guide