Lecture 7 - Sagittal Plane Biomechanics

Front 1

How is gait theorised?

Back 1

Gait is initiated by the swing limb maintained by anterior intertia advancing over the body's COG once the mass centre has moved sufficiently, process then repeated on opposite limb creating an effectively 'muscless' creation of power

Front 2

What impends the motion?

Back 2

Impended only by wind resistance and gravitation changes (walking up hill etc)

Front 3

What are the 4 mechanisms for the creation of power for efficient forward motion?

Back 3

1. The pull that is placed on the swing limb is most significant source of power that acts on the body's centre of mass
2. Moment provides continuation of motion
3. Gravity permits the body to use its own mass, by acting on the trunk when it is placed just in front of the planted foot
4. Elastic tissue response represents a complex form of energy return. Energy ithat is stored at impact is returned.

Front 4

What did Dananberg (1993a) state?

Back 4

The body is designed to pull the centre of mass over a single pivotal site formed by dorsiflexion of the 1st MPJ

Front 5

What are the premisis of the foot?

Back 5

- The foot must be able to resist forces that applied to it
-This must co-ordinate with the power input which is required to move the body forward over the foot
- The foot has 3' autosupportive' mechanisms

Front 6

Explain 'high gear vs low gear'

Back 6

A larger thrust is purportedy gained by 'high gear' propulsion where a visible protrusion of the medial slip of the plantar aponeurosis is seen during gait (believed to indicate the establishment of an effective windlass mechanism) while a 'low gear' propulsion is less effective and requires more muscular involvement (ie: less energy efficient)

Front 7

What is the locking wedge and truss effect?

Back 7

It reflects the ability of the metatarsals to transfer weight to the supporting surface around the pivotal motion of the bases on the heads allowing the metatarsal shaft to move froma parallel to vertical position

Front 8

True or false - The ability of the metatarsales to become perpendicular is dependent on the ability of the 1st MPJ to allow sufficient motion in the sagittal plane.

Back 8

True

Front 9

What is the Windlass Mechanism?

Back 9

An inwardly direct force from a tension band attached to a drum with a lever

Front 10

What occurs when the Windlass mechanism is activated?

Back 10

When the windlass mechanism is activated (ie: at heel off) the motion of DF at the hallux increases the tension in the plantar fascia which pulls the hallux proximally into the metatarsal, this force is met with an equal and opposite force. This 'reactive' force resists the attempt of further DF of the hallux

Front 11

What is occuring at the opposite end of the metatarsal of the windlass mechanism?

Back 11

The force upon the head of the metatarsal is resisted by the force acting on the base of the metatarsal by the medial cuneiform. This creates a PF moment at the metatarsal.

Front 12

Where does GRF come into play with the windlass mechanism?

Back 12

As the ground is forced upon by the foot, the foot is also receiving an equal but opposite reactive forces (ie: GRF) which is exerted upon the met head as the body weight is transferred through the 1st MPJ

Front 13

What does the GRF do?

Back 13

This force creates a DF moment on the metatarsal, one which opposes the previous moment of force.

Front 14

unknown

Back 14

- The PF moment from the windlass becomes larger then the DF moment from GRF the metatarsal will PF

Front 15

unknown

Back 15

DF of the first MPJ pulls on the plantar aponeurosis shortening the distance between the first metatarsal head and calcaneus
- Supinates the foot and co-ordinate with external rotation from above
- This mechanism requires first MPJ DF

Front 16

What is Sagittal Plane Block?

Back 16

-First ray/1st MPJ motion impended
- Mechanism fails when the talus is severely adducted, resulting in a rearfoot adduction on the forefoot and transverse plane forces being greater than safittal plane forces

Front 17

What are the results of Hallux Limitus?

Back 17

- Will result in failure of the foots autosupportive mechanism to be established
- Occurs as the joint is a pivotal point for forward motion and at the time of greatest power input from above
- this power has to be stored or dissipated
- this reflected as secondary motiion at other sites

Front 18

What is 'functional' hallux limitus (FHL) described by Dananberg?

Back 18

Described as being reduced or inadequate 1st MPJ motion during gait while maintaining adequate ROM during non wb examination

Front 19

What is 'structural' hallux limitus (SHL)?

Back 19

Due to primary and secondary structural deformity

Front 20

SHL is often more difficult to determine than FHL? True or false?

Back 20

False, FHL is more difficult to determine

Front 21

Why is FHL difficult to determine?

Back 21

It is only visible during stance phase of gait, and will often display full ROM during non wb examination with no obvious joint degeneration or malfunction

Front 22

What are the compensation mechanism for sagittal plane blockage?

Back 22

1. altered heel lift
2. vertical toe off
3. Inverted step
4. Abducted and adducted toe off
5. Flexion compensation of body

Front 23

What is altered heel lift?

Back 23

As one of the most common compensatory methods employed where the oblique axis of the midtarsal joint, as the next proximal structure, provides a portion of the required range of motion and results visually as an excessively pronated foot in the second portion of single limb phase.

Front 24

What is vertical toe off?

Back 24

Occurs when heel lift is delayed resulting the foot being lifted of the ground prior to propulsion (ie: appropulsive gait) in a energy inefficient unsteady gait style. Commonly seen in the older client.

Front 25

What is Inverted step?

Back 25

Occurs when weight flow fails to move medially to the first web space prior to heel lift. The resultant chronic inversion is difficult to see during bare foot gait (without the benefit of pressure measurement systems) and results in excessive lateral column loads visible as excessive wearing of the lateral shoe (ieL Ffoot valgus)

Front 26

What is abducted and adducted (pidgeon toe) toe off?

Back 26

Compensation occurs as the body will follow the path of least resistance and is dependent on the position or bias of the more proximal structures. If the hip or foot displays an internally rotated bias (met adductus) the body will direct weight laterally around the blockage and result in an adducted toe off. If the hip is exteranally rotated or a femoral retroversion exists, the foot will abduct.

Front 27

What did Stone et al (1999) state?

Back 27

that approximately 50% of patients presenting with a painful plantar fasciitis have FHL or SHL with a hypermobile or fixed elevatus first ray.

Front 28

Describe flexion compensation of the body...

Back 28

Abnormal torso flexion occurs during the single support phase of gait with a failure of the kee to fully extend. Spinal lordosis will be reduced leading to an abnormally straightened spine at heel strike with a flexed neck and head often seen. Over time, these flexion compensations lead to a chronic postural position.

Front 29

Why do high arch feet easier to raise?

Back 29

High arched feet have a stronger windlass mechanism and therefore are easier to raise.

Front 30

What are someways we can diagnose Hallux Limitus?

Back 30

- Lateral gait analysis
- Lateral shoe wear
- ROM of 1st MPJ tends to be restricted while first ray is prevented from movement
- 1st met head tends to be wider
- Pain sometimes present with dorso lateral aspect of first MPJ
- First MPJ block test

Front 31

What are we looking for in gait analysis with those with Hallux Limitus?

Back 31

- The compensatory motions
- Especially with MTJ collapsing just as the heel comes off the ground
- The late midstance phase pronation
- The abductory or adductory twist
- The delayed heel off
- The flexed knee and hip

Front 32

How may orthoses help Hallux Limitus?

Back 32

- Facilitate first ray motion and DF of the hallux
- Medial heel wedge and forefoot lateral wedge?

Front 33

What are some concerns regarding Hallux Limitus for podiatrist?

Back 33

- THeory needs more developement (only been around for short time)
- Theory doesnt exaplin everything and does not attmept to
- Difficulties in visualising a FHL
- Lack of clear guidlines for clinical management
- No evidence for assumed normal direction and timing of weight flow
- Need computerised in shoe plantar pressure measurements to properly apply the theory
- Still uncertain as too what causes FHL