21/22: Orthosis Overview - Mahoney

Question 1

define orthosis

Answer 1

• • A prescription orthopedic device to be worn in shoes to assist in the realignment of lower extremity joint malfunctions or to aid in the maintenance of structural alignment following surgery
• • A prescription in-shoe medical device designed to alter the magnitude and temporal patterns of the reaction forces acting on the plantar surface of the foot to allow more normal foot and lower extremity function and to decrease pathologic loading forces on the structural components of the foot and lower extremity during weightbearing (this is mostly referring to an accomadative device)

Question 2

most accurate way to define orthoses

Answer 2

mechanism of action

Question 3

mechanism of action classifications

Answer 3

1. Functional/Root/Neutral [maintain normal foot function at STJ and MTJ]
2. Accommodative [does not attempt to control motion at STJ and MTJ]

Question 4

Allows improved functioning of joints proximal and distal to the STJ and MTJ

Answer 4

functional

• theoretically also controls ankle, knee, and hip problems

Question 5

Provides comfort from plantar lesions and bony prominences

Answer 5

accommodative

Question 6

alters function of the foot vs. alters magnitude and temporal loading patterns of injured plantar foot structures

Answer 6

functional v. accommodative

Question 7

which is softer? which maintains shape better? open or closed cell foams

Answer 7

open
closed

As the number of open cells decreases, the ability of the material to withstand compression increases

Question 8

most important step of orthosis fabrication

Answer 8

casting of the foot

Question 9

negative vs. positive cast

Answer 9

neg = the mold of the foot made from plaster or taken in foam material

pos = Made from plaster material poured into the negative cast OR from laser scan.

Question 10

negative casting technique

Answer 10

aka neutral casting technique

NWB with patient supine or prone and foot held with STJ in neutral and MTJ locked by maximally pronating MTJ (exerting dorsiflexion force on 4th and 5th metatarsals)

CPMS method

1. Place thumb beneath the 4th and 5th metatarsal heads or grasp (lift) the 4th and 5th toes in the toe sulcus
2. Gently dorsiflex 4th and 5th metatarsals until you meet slight resistance (foot still should be in 10-20° of a plantarflexed position at ankle) or gently dorsiflex the foot to 90° when lifting the 4th and 5th toes

Question 11

negative casting technique is for what type of orthosis

Answer 11

functional

Question 12

why would you want to additonally plantarflex the medial column/first metatarsal when casting the foot?

Answer 12

to increase the amount of forefoot valgus which enhances the windlass mechanism function and decreases tension on the plantar fascia

Question 13

when 2nd metatarsal lines up with middle of tibia

Answer 13

STJ is in neutral

Question 14

plastering the foot

Answer 14

1. Place splint around heel, 1/2 of length on each side of foot at a height justbelow malleoli. 2. Mold lateral side first into arch and then medial side overlapping lateral
   half
2. Mold the excess into the plantar/posterior aspect of heel
3. Fold excess plaster on plantar of heel towards posterior aspect
4. The sides of the plaster are folded onto the plantar aspect of the foot, starting with lateral side first. Any excess is folded under the sulcus of the toes
5. The patient’s skin is pulled away from skin on the dorsum of the foot after the plaster is set by squeezing the skin together. The cast is ready to be removed
   when it feels rough and grainy

Question 15

removing the cast

Answer 15

The cast is then grasped along the medial and lateral
aspects of the heel with the fingertips of one hand, still holding the foot in neutral. After the heel is freed, pull the cast straight towards the big toe. Rotate the heel gently to allow removal of the toes from the cast

Question 16

*** what is the correct placement of the foot/ankle for neutral position casting?

Answer 16

STJ neutral, MTJ pronated, ankle dorsiflexed (not beyond 90)

Question 17

intrinsic modification

Answer 17

adding or taking away from the positive cast

Adjustments are made to the positive mold based on biomechanical evaluation

Question 18

what is the technique for making an accommodative orthotic?

Answer 18

Semi-weight bearing (sitting in chair) impression with the patient seated in upright position with hip, knee, and ankle flexed at 90

Question 19

foam box technique

Answer 19

1. Maintain STJ in neutral with one hand and grasp lower leg with other hand
2. Lift foot and place on foam
3. Apply downward pressure to dorsal aspect of knee to drive heel into foam
4. Apply downward pressure to midfoot and then forefoot
5. Foot is withdrawn from foam by doctor

Question 20

making additions to the finished product

Answer 20

extrinsic modification

most common: A rearfoot post (wedge) is attached to the underside to improve stability in the rearfoot (makes it fit better and more stable within the shoe itself)

Question 21

CAD/CAM scans negative cast or the foot directly, how is the positive cast then made?

Answer 21

A physical positive cast can be milled out of a block of wood, OR the orthosis can be milled directly out of a block of polypropylene from a “virtual” positive

Question 22

which is inherently more stiff? milled or pressed orthotic

Answer 22

milled

Question 23

which of the following statements are true?

1. Modifications made to the positive mold are called intrinsic modifications
2. Modifications made to the orthosis are called intrinsic modifications
3. CAD/CAM technology can use laser scans of the foot
4. CAD/CAM technology can use laser scans of the negative mold

Answer 23

1. true
2. false, extrinsic
3. true
4. true

Question 24

where does a functional orthotic end? accommodative?

Answer 24

functional: Ends behind metatarsal heads and just lateral to 1st metatarsal and just medial to 5th metatarsal
accommodative: Full length (to sulcus or tip of toes) and full width (so they need to be a softer material)

Question 25

As long as the orthotic attempts to control abnormal STJ and MTJ motion by having a firm longitudinal arch and the cast is taken in neutral position …

Answer 25

the length and/or width of the orthotic is really not a defining characteristic as to whether it is functional or accomodative

Question 26

true or false: you are generally going to make a functional device narrower than anatomy

Answer 26

true

Question 27

top covers are _____ modifications

Answer 27

extrinsic

• A top cover can be added to help keep the foot from sliding around on the orthosis, to make the anterior edge of the orthosis more comfortable, and to help accommodate osseous structures that may rub against the orthosis and cause irritation
• The top cover can extend to the metatarsal parabola, to the sulcus of the toes, or to the ends of the toes

Question 28

what is spenco?

Answer 28

closed cell expanded rubber foam top cover

poron of ppt is open cell with more cushioning but doesn’t last as long

Question 29

mechanical objective of a functional orthosis

Answer 29

• Resists ground reaction forces that cause abnormal motion to occur during stance phase of gait
• attempts to prevent excessive compensatory pronation or supination
• does nothing during swing phase
• makes foot stable at push off
• controls hypermobility of joints

Question 30

if made correctly, functional orthosis will produce (5)

Answer 30

1. proper STJ and MTJ pronation and supination
2. normal ankle dorsi and plantarflexion
3. normal knee flexion at heel contact
4. proper hip flexion and extension
5. efficient internal and external rotation

Question 31

goals of an accommodative orthotic

Answer 31

• relieves high pressure areas, reduces shock, limits shear forces
• primarily accommodates plantar lesions
• use in neuropathic, vascularly impaired, arthritis feet, feet with inoperable bony or soft tissue prominence

Question 32

a functional device is one which …

1. Most commonly is made from a weightbearing position of the foot
2. Resists abnormal compensatory supination or pronation of the foot
3. Offloads pressure on bony prominences
4. Makes the foot stable at heel strike
5. Makes the foot stable at swing phase

Answer 32

2 is the correct answer

4- push off not heel strike