Chapter 3f Pa Tho Mechanics

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3.6 Pathomechanics

Justin Wernick, DPM

Rules of Compensation

Uncompensated

No range of motion available at the primary compensation site to neutralize the abnormal influence.

Partially Compensated

Limited range of motion available at the primary compensation site to partially neutralize the abnormal

influence.

Fully Compensated

Adequate range of motion available at the primary compensation site to fully neutralize the abnormal

influence.

Calcaneal Varus

Subtalar Varus

Definition of calcaneal varus: An inversion deformity of the posterior portion of the body of the calcaneus due

to an incomplete derotation from its infantile position.

Figure 1.

Orthopedics | Pathomechanics 169



Examination

It is measured in respect to a bisection of the posterior aspect of the calcaneus and the lower one-third ofthe leg.

Subtalar joint compensation requires the calcaneus to only go to the vertical.

Figure 2.

Mechanism of Injury

• Pronation continues into midstance

• Calcaneus everts to the vertical

• Extrinsic frontal plane influences increase the demand to pronate

• Increased acceleration of subtalar joint pronation

170 The 2005 Podiatry Study Guide



Method of Compensation

Figure 3.

Figure 4.




Fully Compensated Subtalar Varus

• Calcaneus undergoes a larger excursion to evert to the vertical

• Leg continues to internally rotate

• Events continue into early midstance

Figure 5.




Haglund’s Deformity

The posterior-lateral border of the calcaneus is usually very prominent. In a calcaneal varus foot type, the exag-

gerated inverted attitude of the calcaneus will be irritated by the counter of the shoe during the resupination phase

of walking.

Figure 6.

Figure 7.




Tailors Bunion

• Since the rearfoot functions in a varus attitude, the forefoot will have the same attitude once footflat has

occurred

• This will increase the ground reaction force load on the 5th ray causing it to pronate

Figure 8.

Figure 9.




Clinical Symptoms• Haglund’s deformity

• Hammer toes, 4th & 5th

• Knee problems

– Medial strain

– Patello-femoral• Bunions and tailors bunions

• Tyloma, 2nd and/or 3 and 4 metatarsals

• Postural symptoms, fatigue

Normal Radiograph-Lateral View

Figure 10. Lateral View

• Continuous cyma line

• Visible sinus tarsi

• Body of talus parallel with weight-bearing plane• Calcaneal inclination of both feet should be uniform

• Calcaneal inclination is index of foot framework

• Cuboid articular facet is evenly aligned with calcaneal articular facet




Figure 11. Dorso Plantar View

• Continuous cyma line• Talar head closely aligned with anterior process of the calcaneus

• Long axis of the rearfoot is from the center of the calcaneus to the medial calcaneo-cuboid joint

• Talar head deviates 15° from the long axis

• 75% of talar head articulates with the navicular

• Lateral border of calcaneus parallels the long axis of the foot

Radiological Findings: Dorso-Plantar View• Thickening, 2nd metatarsal shaft

• Displaced sesmoids

• Cuneoform split

• Intact cyma line• Pronated 5th ray

Figure 12 Dorso-Plantar View




Radiological Findings: Lateral View

• Mild 1st ray elevatus

• Mild change in calcaneal inclination angle

• Intact cyma line


Concept of Function of the Orthoses

• Decelerate and limit subtalar joint pronation by controlling calcaneal eversion.

• Expedite subtalar joint supination

• Control compensations at the midtarsal joint

Figure 14.




Partially Compensated Subtalar Varus

• With a limited range of motion at the subtalar joint

• The ability of the medial forefoot to reach the support surface is enhanced by 1st ray plantarflexion

Figure 15.

Clinical Symptoms

• High arch appearance

• May develop lesion, plantar to the 1st metatarsal

• Lateral heel, knee and postural symptoms

Figure 16.




Block Test

We determine if we have a partially compensated subtalar varus or a rigid plantarflexed 1st ray by using the

Block Test.

Figure 17. Block Test

Uncompensated Subtalar Varus

Since there is no range of motion available at the subtalar joint, the calcaneus will remain inverted as well as the

forefoot, resulting in lateral foot and leg symtomology.

Symptomology

• Lateral heel callus• Lateral callus 5th metatarsal base and head

Figure 18.




Forefoot Varus

Definition: A fixed osseous structural deformity where the forefoot is inverted to the rearfoot.

Figure 19.

Examination

It is measured with respect to a bisection of the posterior aspect of the calcaneus and the plane of the lesser

metatarsals (2 - 4) when the subtalar joint is neutral and the midtarsal joint is maximally pronated.

Figure 20.




Subtalar Joint Compensation Requires the Calcaneus to go Beyond the Vertical.

Figure 21.

Subtalar Joint Compensation Requires the Calcaneus to go Beyond the Vertical.

Figure 22.




In Order for the Forefoot to Reach the Support Surface, the calcaneus will Pronate Beyond

the Vertical into Valgus.

Figure 23.




Figure 24.

Clinical Symptoms

• Severe H.A.V. deformity

• Helomatyloma

• Heel pain

• Plantar fasciitis

• Posterior tibial dysfunction

• Back and postural complications

• Medial knee pain




Morphology of the Arch with a Forefoot Varus Deformity

Since there is a marked inverted attitude to the forefoot, there is very little typography to the plantar of the foot.

Figure 25.




Radiological Findings: Dorso-Plantar View

• Broken cyma line

• Increased talo-calcaneal angle

• Thickening, 2nd metatarsal shaft

• Talar head escape

• Cuneiform split

Figure 26. Dorso-Plantar View





• 1st ray elevatus

• Lowering of the calcaneal inclination angle


• Ptosis of the midfoot





Mechanism for Developing a Forefoot Supinatus

Since the plane of the forefoot cannot pronate as far as the subtalar joint at heel off, an inverted attitude of the

forefoot to the rearfoot results.

Figure 28.

Figure 29.




Concept of Function of the Orthoses

• Decelerate and limit subtalar joint pronation by supporting the forefoot deformity

• Expedite subtalar joint supination

• Control compensations at the midtarsal joint

Figure 30.

Equinus

Definition: Any restriction of motion at the ankle joint that prevents the body from passing over the foot.

Figure 31.




Examination

Measured with the subtalar joint in neutral position and the knee fully extended.

Figure 32.

Etiology

• Congenital

– Bony block of the ankle

– Short and/or tight triceps• Spastic contractures of the triceps

• Acquired

– Constant and complete subtalar joint and oblique mt.jt. pronation

– Structural short leg

– Anterior tibial weakness

Compensation

What is the main factor that will determine how an individual will compensate for an equinus condition?

Range of motion at the primary compensation site

What is the primary compensation site for sagittal plane influences?

Oblique axis of the midtarsal joint




Uncompensated Equinus

With no range of motion available at the ankle and midtarsal joint, the heel will not make contact with the sup-

port surface.

Figure 33.

Partially Compensated Equinus

In each case, the compensations expedite the body passing from behind the support limb to in front of the sup-

port limb.

Figure 34.




With a limited range of motion at the ankle and midtarsal joint, the compensation can occur as:

• Knee flexion or extension

• Premature heel lift

• Out - toe gait

• Short stride

• Toe walking in children

Figure 35.

Figure 36.




Fully Compensated Equinus

With an adequate range of motion at the midtarsal joint the compensation can occur as:

• Lowering of the calcaneal inclination angle

• Collapse of the arch

With an adequate range of motion at the midtarsal joint the compensation can occur as:

• Lowering of the calcaneal inclination angle• Collapse of the arch

Figure 37.

Figure 38.




Clinical Symptoms

• Severe HAV deformity

• Corns and calluses

• Hammer toes

• Heel and arch pain

• Fatigue and postural symptoms• Back pain

Figure 39.



• “Medial escape of the talus”

• “Abductus of the forefoot”

• Less then 75% of the talar head articulates with the NAVICULAR

Figure 40. Dorso-plantar View






• Decreased calcaneal inclination angle

• Increased talar declination angle

• Saddle shape to the tarsal region

• Cuboid lowers and everts






Concept of Orthotic Device Function

Fully Compensated

• Decelerate calcaneal eversion

• Control plantarflexion of the distal portion of the calcaneus

• Control abduction of the forefoot

• Control medial shift of the tibia

Figure 43. Mild to Moderate Compensation

• Use an accommodative device

• Raise the heel to decrease the demand on the midtarsal joint

• Use a proper lasted shoe to assist in support

• Use of a SMO

Figure 44. Severe Compensation

• Use an accommodative device

• Raise the heel to decrease the demand on the midtarsal joint

• Use a proper lasted shoe to assist in support

• Use of a SMO

• Bring the support surface up to the heel to extend the weight-bearing period

• Balance abnormalities of the forefoot




Forefoot Valgus

Definition: An osseous deformity of the forefoot in which the plane of all the lesser metatarsal heads is everted

relative to a bisection of the posterior aspect of the calcaneus

Examination

Measured with the subtalar joint in neutral position and the midtarsal joint maximally pronated.

Planes of Deviation

Figure 45.

Rigid Platarflexed 1st Ray

Sometimes referred to as a rigid forefoot valgus. A congenital or acquired position of the 1st ray in which the

1st metatarsal head is fixed below the plane of the lesser metatarsal heads.

Figure 46. Rigid Plantarflexed 1st Ray




Flexible Plantaflexed 1st Ray

A condition where the 1st metatarsal head has migrated below the level of the lesser metatarsal head plane but

can be easily moved back to or above that level by some force applied to its plantar aspect.

Figure 47. Flexible Plantarflexed 1st Ray

Examination for Position of the 1st Ray

Figure 48.




Concept of Function: Rigid Plantarflexed Ist Ray

• 1st ray is plantar to the lateral forefoot plane

• 1st ray is plantar to the weight-bearing heel

• Generalized limitation of motion in the foot

Figure 49.

With limited range of motion in the longitudinal midtarsal joint, frontal plane compensation will take place via

supination of the subtalar joint.

With the forefoot plantar to the heel, compensation will occur as a lack of dorsiflexion at the ankle.

Figure 50.




With limited range of motion in the longitudinal midtarsal joint, frontal plane compensation will take place via

supination of the subtalar joint.

With the forefoot plantar to the heel, compensation will occur as dorsiflexion at the ankle.

Figure 51.

Clinical Symptoms Rigid Plantarflexed Ist Ray

• Hammer toes

• Heel pain

• Lateral ankle sprains

• Lateral knee and hip pain

• Impact shock to the back

• Plantar lesions, 1st and 5th met. heads

• Sesmoiditis




Concept of Function Flexible Plantarflexed Ist Ray

• 1st ray is plantar to the lateral forefoot plane

• 1st ray is plantar to the weight-bearing heel

• No limitation of motion in the foot

Figure 52.

With no limitation of motion in the longitudinal midtarsal joint, frontal plane compensation will take place via

supination of the midtarsal joint and longitudinal axis.

With the forefoot plantar to the heel, compensation will occur as dorsiflexion of the oblique midtarsal joint and

the 1st ray.

Figure 53.




Clinical Symptoms Flexible Plantarflexed Ist Ray

• Hammer toes

• Heel pain

• Arch pain

• Medial knee and hip pain

• Postural symptoms• Plantar lesions, 2,3,4th metatarsal heads

• HAV deformity

Figure 54.

Figure 55.





• Broken cyma line, anterior

• Increased calcaneal inclination angle

• Decreased talar declination angle

• “Humped” shape to tarsal region



• Broken cyma line, anterior

• Lateral deviation of the talus

• Adductus of the forefoot

• Bi-partite sesmoids

Figure 57. Dorso-Plantar View




Concept of Function Of The Orthosis: Flexible Plantarflexed Ist Ray

• Control calcaneal eversion

• Allow 1st ray stabilization

• Support midtarsal joint

• Align plane of 1st ray with the plane of the lesser metatarsals

• Control calcaneal inversion• Raise heel to reduce need to dorsiflex ankle

• Align plane of 1st ray with the plane of the lesser metatarsals with bar or valgus post

Figure 58.




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Chapter 3f Pa Tho Mechanics